| Activation |
A chemical treatment of a surface, typically involving immersion into a bath, that prepares it to accept further chemical changes. An example would be immersion of a material into an acid bath prior to electroplating. It is the opposite of passivation. |
| Active Corrosion |
Chemical attack of a metallic surface that results in continual formation of corrosion product and continual loss of material. |
| Adsorption |
Deposition of environmental vapors onto the surface of a material. This is the mechanism by which some precious metals become tarnished. |
| Age Hardening |
A heat treatment process in which the alloying elements in a supersaturated solid solution are allowed to precipitate out of solution, putting strain on the crystalline matrix and greatly increasing strength. This is the mechanism by which copper beryllium is strengthened. |
| Allowable Deflection |
The maximum amount that a component can be deflected without some kind of failure. The use of materials with high resilience such as copper beryllium will result in components with greater allowable deflection. |
| Alloy |
A metal made of a combination of several elements. Alloys are typically designated by their composition. |
| Alternating Stress |
A loading pattern in which the applied stress cycles through high and low values. |
| Ampacity (Current Carrying Capacity) |
The maximum amount of current an electrical conductor can carry without exceeding a prescribed temperature rise. This is not a physical property of a metal, since it depends on the geometry of the conductor as well as the definition of a safe temperature rise. |
| Anisotropy |
The tendency of a material to exhibit different properties when tested in different orientations. Most alloys strengthened only by cold work will exhibit great anisotropy, (directionality) while age hardened materials like copper beryllium will be more isotropic. |
| Anisotropy Coefficient (r) |
A measure of the degree of the anisotropy (directionality) of mechanical properties in cold worked materials. In strip material, it is defined as the ratio of the true transverse strain to the true through-the-thickness strain, and is calculated as the negative of the true transverse strain divided by the sum of the true longitudinal strain and the true transverse strain. |
| Annealing |
The use of a thermal treatment to soften a metal after cold working. It reduces strength and hardness, and increases ductility, allowing for further cold working. If it recrystallizes the material and fully dissolves precipitates, it is called a solution anneal. |
| Antimicrobial |
The tendency of a material to kill bacteria that come to rest on its surface, and to resist further growth of the bacteria. |
| Arc Column |
The column of ionized air through which an electric arc travels between two surfaces of different electrical potential. |
| Arcing |
The transfer of electrons between two non-contacting surfaces under different electrical potentials. Arcing occurs only when the voltage is above the dielectric breakdown voltage of the medium between the two surfaces at the given distance between the two surfaces. This can happen if the voltage between the surfaces increases, or if the two surfaces come closer together. |
| Asperity (A-spot) |
On the microscopic scale, these are the high spots on a rough surface. When two bodies are in contact with each other, contact occurs at the asperities on each surface. |
| ASTM |
The American Society of Testing and Materials. This is a standards organization that provides specifications for materials and testing methodology. |
| Bad Way Bending |
Forming a strip material in the transverse direction, in which the axis of the bend is parallel to the rolling direction of the strip. For alloys strengthened by cold work, it typically requires a larger bend radius than the longitudinal (good way) bending. |
| Bauschinger Effect |
A work-hardening phenomenon that tends to increase the effective strength of a metal when strained in the same direction as the initial forming strain, and to decrease the effective strength when strained in the opposite direction as the initial forming strain. Metals such as Alloy 25 that are heat treated after forming do not experience this effect. |
| Biocompatibility |
The ability of a material to be placed inside a human body or other living tissue without causing any harm to the surrounding tissue. |
| Biofouling |
The tendency of materials to grow organisms on the surface, such as barnacles on ship hulls, algae on steel pipes, etc. Copper alloys are inherently resistant to biofouling. |
| Boundary Lubrication |
A condition in a bearing surface where the lubrication does not completely separate the moving and stationary surfaces (i.e., hydrodynamic conditions do not exist or do not yet exist), characterized by some metal to metal contact. |
| Brazing |
An elevated temperature process used to join two materials in which a filler material is allowed to melt and wick between the two surfaces to be joined, and then subsequently cooled to form a metallic bond between the surfaces. |
| Break |
The final, fractured part of a cut or slit edge. On such edges, the initial part of the cut is crushed into a rollover zone, the middle part is sheared straight, and the final part of the cut fractures and breaks away at an angle, potentially leaving a burr pointing in the direction of the cut. |
| Brinell Hardness |
Hardness as measured by a Brinell test, which uses a 10 mm spherical indenter. The Brinell hardness number is proportional to the applied load divided by the area of the indentation. |
| Bulk Resistance |
The component of electrical resistance that is due to the inherent electrical resistivity of the base metal. |
| Burrs |
Small slivers of metal left at the final fracture zone of a slit or cut edge. |
| Camber |
Edgewise (in the plane of the strip) curvature of strip material, either before or after entering a progressive die. It occurs when one side of the strip is longer or contains higher stress than the other side. Post-die camber can be minimized by notching the edge of the carrier strip. |
| Cantilever Beam |
A simple model of a spring component, with one end fixed and a force or deflection applied to the other end of the beam. |
| Cavitation |
A wear mechanism in components immersed in moving fluid, where microscopic bubbles form on the components surface and collapse with great force, potentially dislodging small pieces of material. |
| CDA (Copper Development Association) |
The organization responsible for providing the UNS numbers for copper alloys. Its website (www.copper.org) provides information on properties and processing of copper alloys. |
| Center Buckle |
A defect in strip material where the center of the strip is longer than the edges, causing buckles to appear down the length of the strip center. |
| Charpy V-Notch Impact Strength (CVN) |
A measure of how much energy a material can absorb in impact without fracturing. It is typically characterized by impacting a notched specimen with an anvil swung on a pendulum, and measuring the amount of energy that the test specimen absorbed during the fracture. This is done by comparing the potential energy difference between the starting height of the pendulum and the height it obtains after fracturing the test specimen. |
| Clad Metal |
A mechanical method of joining two or more strip metals together in layers by passing them through a rolling mill together. Since the metal strips involved are wrought, there is no porosity as there would be in a plating operation. |
| Closure Arc |
An electrical arc that forms between the contact surfaces of a separable connector as the contacts are brought together, provided that there is sufficient voltage to create the arc. |
| Coefficient of Thermal Expansion |
A measure of how much a material expands and contracts in response to changes in temperature. It is calculated by dividing the change in length by the product of the original length and the difference in temperature. |
| Coil Set |
The tendency of a coiled strip material to partially retain the curvature of the coil when it is removed from the spool. |
| Cold Drawing |
Reduction in diameter of a wire by passing it through a drawing die, at a temperature less than the recrystallization temperature. This increases the strength of the wire at a penalty of reduced ductility |
| Cold Heading |
A cold working process designed to increase the diameter of the end of rod by forcibly compressing the end. |
| Cold Rolling |
Reduction in thickness of strip by passing it between cylindrical rollers, at a temperature less than the recrystallization temperature. This increases the strength of the strip at a penalty of reduced ductility and formability. |
| Cold Working |
Reshaping of a material below the recrystallization temperature. Cold Working typically imparts strength to a material at a penalty of reduced ductility. |
| Compressive Strength |
The strength of a material as measured in a compression test. As in a tensile test, a compression test plots stress vs. strain. Yield strength is calculated the same way in both tests. Ductile materials typically do not have a compressive ultimate strength, but brittle materials do. |
| Constriction Resistance |
The electrical resistance at contact interface between two electrical conductors due to the current being constrained to flow between touching asperities. The constriction resistance decreases as the normal force between the conductors increases, and increases as the hardness of the mating surfaces increases. |
| Contact Bounce |
When the two halves of a contact interface are brought together quickly, such as in a snap switch, the halves may bounce off of each other briefly before coming to rest in contact with each other. Each bounce has the potential to create an electrical arc and the associated arcing damage on the contact surfaces |
| Contact Force |
The force between two bodies in contact. Higher contact forces in in electrical connectors result in lower resistance of the contact interface. |
| Contact Resistance |
The electrical resistance of the a separable connector. It is a sum of the bulk resistance of the contacts and plating layers, as well as the film resistance and constriction resistance of the contact interface. |
| Contact Wipe |
During mating of electronic connectors, the two surfaces are typically designed to make initial contact and then slide across each other. This sliding action is called wipe, and it is used to push debris, films, oxides, etc. away from the contact interface, allowing for good electrical contact. |
| Corrosion |
Chemical attack of a metallic surface resulting in formation of corrosion product (oxides, sulfides, chlorides, etc.) accompanied by loss of metal from the surface. |
| Corrosion Migration |
Migration of corrosion product from an unprotected area across a protected surface. For example, copper chloride can spread over a gold plated copper alloy from pores in the plating or from unplated edges. |
| Corrosion Resistance |
The ability of a material to resist corrosion. ToughMet and copper beryllium have very good corrosion resistance compared to other copper alloys. |
| Creep |
For components loaded in tension and subjected to elevated temperatures, this is a gradual increase in strain at constant stress. |
| Creep Corrosion |
Migration of corrosion product from an unprotected area across a protected surface. For example, copper chloride can spread over a gold plated copper alloy from pores in the plating or from unplated edges. |
| Creep Rupture Strength |
The stress level at which a material undergoing creep deformation fractures. |
| Crimping |
A method of joining a terminal to a wire. The end of the terminal is compressed onto the wire, which deforms and potentially cold welds itself to the terminal. |
| Crown |
A deflect in strip material where the center of the strip is thicker than the edges. |
| Current Carrying Capacity (Ampacity) |
The maximum amount of current an electrical conductor can carry without exceeding a prescribed temperature rise. This is not a physical property of a metal, since it depends on the geometry of the conductor as well as the definition of a safe temperature rise. |
| Delta R |
A measure of the tendency of material to ear during deep drawing, it is the measure of the directional variation of the anisotropy coefficient of a material. |
| Design for Six Sigma |
The use of Six Sigma methodology in research and development, to create new products with already optimized processes. |
| Design Force |
The force that an electrical contact is designed to produce at the beginning of life, assuming that all dimensions and material properties fall at the nominal value of the tolerances. |
| Diamond Pyramid Hardness (DPH) |
A microhardness test using a Vickers diamond indenter, under a light load to create very small indentations, used to measure the hardness of very small parts. It is sensitive to local variations in the microstructure, so it should be calculated as the average of multiple measurements. |
| Dielectric Breakdown Voltage |
The minimum voltage between two non-contacting surfaces necessary to generate or sustain an electrical arc between them. It depends on the distance between the surfaces and the dielectric strength of the medium between them. |
| Diffusion |
The tendency of atoms of one material to diffuse through a different material, under the influence of time and temperature. For example, in an electrical contact, copper atoms from a copper base metal may diffuse through a plating layer and form copper oxide on the surface of the plating. |
| Diffusion Barrier |
Any substance that prevents or significantly retards diffusion. An underlayer of nickel plating on a copper alloy will prevent diffusion of copper atoms through the top layer of plating. |
| Diamagnetic |
Non-magnetic in the sense that any applied magnetic field will generate an opposing magnetic field within the material, cancelling out the applied magnetic field within the material. |
| Dimensional Tolerances |
The maximum amount by which dimensions of produced parts are allowed to vary from the nominal dimension specified on the print. |
| Directionality |
The tendency of a material to exhibit different properties when tested in different orientations. Most alloys strengthened only by cold work will exhibit great anisotropy, (directionality) while age hardened materials will be more isotropic. |
| Dislocation |
An imperfection in the crystalline structure of a metal. These are areas where sections of the crystalline matrix are free to move across each other, which results in yielding and permanent set in the material. In low strength materials, dislocations are free to move easily. Higher strength materials have various mechanisms to impede the motion of dislocations. |
| Dislocation Entanglement |
When a material is heavily cold worked (large amounts of permanent deformation), the dislocations tend to pile up and prevent further motion. This increases the strength of the metal (strain hardening). If, however, the goal is to further cold work the material, the material needs to be annealed above the recrystallization temperature to create a new crystalline structure with new dislocations free to move. |
| Dispersion Hardening |
Strengthening of a material by dispersing inclusions of another material (such as small oxide particles) throughout the matrix. |
| DPH (Diamond Pyramid Hardness) |
Microhardness as measured by a Vickers test under a very small load, which uses a diamond indenter. The diamond pyramid hardness number is proportional to the applied load divided by the area of the indentation. |
| Drawing |
In wire, this is a reduction in diameter by passing it through a drawing die. In strip, this is an operation that forces material to flow into a raised or depressed embossment or feature on the surface, such as drawing an upright cylinder out of the plane of the strip. |
| Drill String Temper (DST) |
A special temper of Alloy 25 copper beryllium used in downhole drilling operations. It is given a proprietary heat treatment to increase toughness and ductility. |
| Ductile to Brittle Transition Temperature |
The temperature below which a normally ductile metal will fail in a brittle fashion. This is common in steel alloys, but copper alloys remain ductile at cryogenic temperatures. |
| Ductility |
A measure of how much a material will plastically deform before fracture. It is the opposite of brittleness. |
| Earring |
A condition in anisotropic strip, where material will not flow evenly into a deep draw, leaving excess material around the base of the draw in certain directions. |
| Edge Wave |
A defect in strip material where the edges of the strip are longer than the center, causing a wave-like appearance on the strip edges. |
| EDM (Spark Erosion Machining) |
A machining method in which electrical arcs are transmitted from the cutting tool to the workpiece in order to cut into the workpiece or to remove metal from it. |
| Elastic Limit |
The stress level at which any further strain will result in plastic deformation of the material. Below the elastic limit, all strain is elastic and will be recovered when the loading is removed. |
| Elastic Modulus |
The ratio of stress to strain in the elastic portion of a stress-strain curve. A high modulus describes a stiff material, while a low modulus describes a flexible material. When a part is elastically strained (deformed), the force required to produce this deformation is directly proportional to the modulus. |
| Elastic Resilience |
A measure of how much a metal can be strained without undergoing permanent set. It is approximated by dividing the yield strength of a material by its elastic modulus. Materials with high elastic resilience such as copper beryllium or ToughMet can withstand much greater strain without permanently deforming than materials with lower elastic resilience. |
| Elastic Springback |
The tendency of elastic strain to recover in a forming operation. For example, when a part is bent to a 90-degree angle, it will spring back to a larger angle when the forming tool is removed. |
| Elastic Strain |
The strain placed in a material that will completely recover when the loading is removed. If all the strain placed in a material is elastic, the part will return to its original shape when the applied load is removed. |
| Electrical Arcing |
The transfer of electrons between two non-contacting surfaces under different electrical potentials. Arcing occurs only when the voltage is above the dielectric breakdown voltage of the medium between the two surfaces at the given distance between the two surfaces. This can happen if the voltage between the surfaces increases, or if the two surfaces come closer together. |
| Electrical Conductivity |
The ability of a material to pass electrical current. It is the inverse of resistivity. Higher conductivity materials will be able to pass current through with less of the electrical energy lost as heat. |
| Electrical Resistance |
The resistance of a material to passing electrical current. It is the inverse of conductivity. Higher resistivity materials will be cause more of the energy of the passing current to be lost as heat. |
| Electroless Plating |
An autocatalytic reaction that allows ions of the plating bath to deposit on the surface of the object to be plated without the use of an electrical current. |
| Electroplating |
Deposition of material from a plating bath onto the surface of the object to be plated, using an electrical current to drive a galvanic reaction. |
| Elongation |
The amount that a material stretches during a tensile test. This is typically measured at the conclusion of the test, after the specimen breaks and the elastic strain is recovered. |
| ELV |
End of Life Vehicle directive. A European directive that promotes recyclability and limited use of hazardous materials in vehicles. It does not restrict copper beryllium in any way. |
| End of Life Contact Force |
The contact force that remains in an electrical contact at the end of the useful life of the connector. It will be less than the beginning of life contact force due to stress relaxation, occasional overstressing, fatigue, etc. |
| Endurance Limit |
The maximum stress level a material can be subjected to in cyclic loading without experiencing fatigue failure. Copper alloys do not have endurance limits, so the fatigue strength at a very large number of cycles, such as 100,000,000 is reported instead. |
| Engineering Strain |
The strain in a tensile test, calculated by taking dividing the instantaneous change in length of the test specimen by its initial length. |
| Engineering Stress |
In a tensile test, this is the applied force divided by the original cross sectional area of the test specimen. |
| Extraction Force |
The amount of force it takes to disengage an electrical connector. It is theoretically equal to the sum of the normal force at each point of contact multiplied by the coefficient of friction at each point of contact. |
| Extrusion |
A hotworking process where material is heated up and is forced through a die in order to reduce the cross section and elongate the material. An example is extrusion of short cylindrical billet into a long rod. |
| Fatigue |
A failure mechanism in cyclically loaded components where small cracks or crystalline imperfections gradually grow over time, leading to fracture of the component. |
| Fatigue Life |
The typical amount of time that a cyclically loaded component can be expected to survive before failing in fatigue. |
| Fatigue Limit |
The maximum stress level a material can be subjected to in cyclic loading without experiencing fatigue failure. Copper alloys do not have endurance limits, so the fatigue strength at a very large number of cycles, such as 100,000,000 is reported instead. |
| Fatigue Strength |
The stress level at which a material undergoing cyclic loading would be expected to last the required number of cycles without failing. |
| Fatigue Test |
A test in which a sample is cyclically loaded in bending or tension and released. The number of cycles to failure at a given stress level is recorded. The results of a number of these tests for a given material are plotted on an S-N curve as stress level vs. number of cycles to failure. |
| Ferromagnetic |
Strongly attracted to a magnetic field. |
| Film Resistance |
The electrical resistance of the oxides, tarnishes, corrosion products, dirt, and/or lubrication films that form on the surface of an electrical contact. It is a highly variable number. |
| Finite Element Analysis (FEA) |
A computer simulation of a component under loading. It can be used to determine stresses, strains, deformation, temperature rises, etc. of a component without the need to first produce a prototype, saving time and tooling costs. The prototype is only necessary for testing after the model predicts that it will function adequately. |
| Fixturing |
Restraining of components during heat treatment to prevent them from moving and distorting. |
| Flux |
A substance used to clear debris and activate surfaces prior to soldering or brazing. |
| Formability |
The ability of a material to be formed into the desired shape. In strip, it is usually characterized by the R/t ratio. |
| Forming Strains |
The plastic strains imparted to a material during forming operations. These can be a source of residual stress. |
| Fracture Toughness K1C |
A measure of the amount of energy required to cause cracks to propagate through a material. |
| Fretting |
Repeated relative motion on the microscopic scale between two surfaces in contact. It can be caused by mechanical vibration or by thermal expansion and contraction. |
| Fretting Corrosion |
Corrosion that occurs under fretting on soft, ductile platings that have hard oxides, such as in tin-plated contacts. After the initial contact breaks through the hard oxide, motion of the contact point oxidizes the freshly exposed surface. After a number of motion cycles, the oxide layer becomes too thick to break through, resulting in poor electrical contact. Fretting corrosion can be minimized by using high contact forces and lubrication to prevent oxidation and carry away oxides. |
| Frictional Polymer |
A polymer that builds up on the surface of platinum and palladium contact surfaces through adsorption of the polymer's components from the atmosphere. |
| Fully Reversed Bending |
Bending strip or other flat product in a fatigue test. The test piece is bent in one direction, passed back through its unbent shape to be bent an equal amount in the opposite direction, then returned to its initial unbent shape. The cycle is then repeated. This bending method is sometimes referred to as R=-1 bending, where R is the ratio of minimum stress experienced in each cycle divided by the maximum stress. Failure is faster than in unidirectional bending. |
| Galling |
Transfer of metal between a stationary surface and a rotating surface held together under pressure. |
| Galling Stress |
The minimum stress at which galling occurs between two metallic surfaces. Copper Beryllium and ToughMet have high galling thresholds relative to other metals. |
| Galvanic Corrosion |
Corrosion that occurs when two dissimilar metals are in electrical contact with each other and an electrolytic fluid. The less noble metal (anode) will dissolve and release positive ions into solution with the electrolyte. This frees electrons to move through a conducting path to the more noble metal (cathode), where they pair up with the positive ions that deposit on the surface from the electrolyte. The net result is that the anode material slowly dissolves, and plates onto the surface of the cathode. |
| Gerber Diagram |
A diagram used to predict the fatigue life of parts that are in a cyclic stress state that is neither fully reversed nor unidirectional. It is used to calculate the maximum allowable fluctuations from a given stress level, based on the fully reversed fatigue strength at the desired number of cycles, the mean stress experienced in each cycle, and the ultimate tensile strength of the material. The Gerber diagram is less conservative than the Goodman diagram. |
| Good Way Bending |
Forming a strip material in the longitudinal direction, whereby the axis of the bend is perpendicular to the rolling direction of the strip. For alloys strengthened by cold work, it can typically be done with a smaller bend radius than the transverse (bad way) bending. |
| Goodman Diagram |
A diagram used to predict the fatigue life of parts that are in a cyclic stress state that is neither fully reversed nor unidirectional. It is used to calculate the maximum allowable fluctuations from a given stress level, based on the fully reversed fatigue strength at the desired number of cycles, the mean stress experienced in each cycle, and the ultimate tensile strength of the material. The Goodman diagram is more conservative than the Gerber diagram. |
| Grain |
A single crystal, or region of uniform crystalline orientation within a metal. |
| Grain Boundary |
The spaces between the grains in a metal, where the atoms do not line up perfectly with the crystalline structures of the adjacent grains. |
| Grain Boundary Precipitate |
Precipitate that forms in the grain boundaries during age hardening. Precipitation within the grains adds strength to the metal, while excessive precipitation in the grain boundaries can decrease the strength and make it brittle. Heavy precipitation at the grain boundaries is a sign of severely overaged material. |
| Grain Size |
An average value of the apparent diameters of grains within a metal. |
| Hard Gold |
A gold plating with a small amount of cobalt or nickel added to increase hardness or wear resistance. It requires a greater normal force at the point of electrical contact than does soft gold. |
| Hardness |
The ability of a material to resist indentation. |
| Heat Capacity |
A physical property of a material that provides the ratio of thermal energy gained or lost divided by the corresponding change in temperature. |
| Heat Treat Distortion |
The tendency of a material to change shape during heat treatment, as unbalanced residuals stresses cause certain areas of a part to respond more quickly to age hardening than the rest of the part. |
| Heat Treating |
Subjecting a part or material to elevated temperatures in order to achieve a change in mechanical properties. Annealing heat treatments soften the material, while hardening treatments increase the strength. |
| Hot Working |
Deformation of a metal at a temperature greater than the recrystallization temperature, so that no strengthening occurs during the process, leaving the material soft enough for further deformation. |
| Hydrodynamic Lubrication |
A condition in a bearing surface where the lubrication completely separates the moving and stationary surfaces, and the moving part is entirely supported by the pressure of the lubricant. There is no metal to metal contact in this lubrication regime. |
| Hydrogen Embrittlement |
A failure mechanism in which hydrogen atoms diffuse into the base metal and settle in the crystalline interstices, causing the metal to become brittle. Steel alloys are vulnerable, but copper alloys such as copper beryllium and ToughMet are immune. |
| IACS |
International Annealed Copper Standard - A measure of the electrical conductivity of a material relative to copper, with 100% IACS conductivity is defined as 6.79 x10-7 ohm-inches or 1.72 x 10-6 ohm-cm. A material with 50% IACS conductivity has approximately half the electrical conductivity (or twice the resistivity) of 100% IACS copper. |
| Impact Strength |
A measure of how much energy a material can absorb in impact without fracturing. It is typically measured by an Izod or Charpy test, and is an approximation of the toughness of the material. |
| Inclusions |
Small particles of foreign matter or alloying elements present in a metal. |
| Insertion Force |
The amount of force it takes to engage an electrical connector. It is larger than the extraction force, since some of the force must go into deflecting the spring contacts inside the connector. Ergonomic regulations limit the maximum value that this force can be, so high performance materials like copper beryllium are often used to ensure that the beginning of life contact force (and thus insertion force) does not have to be dramatically increased to compensate for loss of normal force over time. |
| Interface |
The area where two surfaces come into contact with each other. |
| Intergranular Cracking |
Cracks that propagate through the grain boundaries (around the grains) in a material, as opposed to propagating directly through the grains. |
| Intermetallic |
A sometimes parasitic alloy that forms between two metals in contact. For example, a tin-plated copper alloy contact will form a brittle copper-tin intermetallic compound at the interface. This may reduce the fatigue strength of the contact. |
| Interstice |
A space among the atoms in the lattice of a crystalline structure. |
| Interstitial Solution |
An alloy in which atoms of the alloying element reside in the interstices of the crystalline lattice. |
| Isotropy |
The tendency of a material to exhibit identical properties when tested in different orientations. Most alloys strengthened only by cold work will exhibit great anisotropy, (directionality) while age hardened materials like copper beryllium will be more isotropic. |
| JIG - Joint Industry Guide for Material Composition Declaration in Electronic Products |
An international directive that encourages the declaration and reporting of certain materials used in electronic equipment. Copper beryllium is usually not present in enough quantity in electronic equipment to exceed the threshold reporting limit. |
| Joule Heating (Resistive Heating) |
Heating of a metal due to an electric current passing through it. Materials with higher conductivity (lower resistivity) will experience a lower temperature rise than materials with lower conductivity (higher resistivity). |
| Knoop Hardness |
Hardness as measured by a Knoop test, which uses an elongated diamond indenter. The Knoop hardness number is proportional to the applied load divided by the area of the indentation. |
| Laser Cutting |
A method of cutting metal where laser pulses are used to vaporize the material to be removed. |
| Lean Manufacturing |
A methodology designed to reduce waste in production, resulting in cost savings. |
| Lean Sigma |
A combination of lean manufacturing and six sigma, designed to reduce variation and waste in production, resulting in cost savings and process improvement. |
| Liquid Metal Embrittlement |
A degradation mechanism where contact with a liquid metal may cause integranular attack of a susceptible solid metal, resulting in permanent weakening and loss of ductility in the solid metal. For example, contact with liquid mercury will embrittle most copper-based alloys. |
| Longitudinal |
Oriented in the rolling direction of strip and plate, or in the drawing or extrusion direction of rod, bar, and tube (i.e., "down-the-length" direction.) |
| Longitudinal Formability |
The formability of the strip in the longitudinal, or good-way direction. For alloys strengthened by cold work, it is typically better than the transverse (bad way) formability. |
| Lubricant |
A material such as grease, oil, graphite, etc. used to reduce the coefficient of friction between two contacting surfaces. |
| Lubricity |
The inherent low friction or "slipperiness" of a material surface. A highly lubricious surface will provide a lower friction coefficient than a less lubricious surface. |
| Machinability Rating |
A number used to rate the relative ease of machining various metals. A free-machining alloy is chosen as a baseline, and the machinability rating of another material is the percentage of in-tolerance parts that can be manufactured out of the second material without a tooling change relative to the free-machining alloy. |
| Macrohardness |
A hardness test using a standard load and indenter, creating a sufficiently large indentation that localized variations in the microstructure average out. It is used to measure the hardness of large parts. |
| Magnetic Permeability |
The ratio between the strength of a magnetic field entering a material to that exiting the material. A diamagnetic material has a permeability less than 1, so that the strength of the field is diminished. A magnetically transparent material has a permeability of 1. A paramagnetic material has a permeability slightly greater than 1, so that the filed is slightly increased. A ferromagnetic material has a permeability much greater than 1, while a magnetic shield has a permeability close to zero. |
| Magnetic Susceptibility |
The tendency of a material to be magnetized when a magnetic field is applied to it. Ferromagnetic materials have high susceptibilities. |
| Magnetic Transparency |
The ability of a material to allow magnetic fields to pass through completely unaltered. A material with a magnetic permeability exactly equal to 1 is completely transparent to magnetic fields. Copper beryllium and ToughMet have permeabilities approximating 1, which allow them to be used in non-magnetic applications such as inside MRI's or in sensitive downhole drilling equipment. |
| Manufacturing Tolerances |
The maximum amount by which dimensions of produced parts are allowed to vary from the nominal dimension specified on the print. |
| Material Tolerances |
The maximum amount by which the properties of materials are allowed to very from the nominal values. |
| MBR/t Ratio |
In bending operations, this is the ratio of the smallest inside radius of the bend to the strip thickness that does not result in cracking of the strip at the bend. The smaller the value of MBR/t, the more severely the strip can be bent. |
| Mean Stress |
The average of the maximum and minimum stress experienced in one cycle of a cyclically loaded component or fatigue test specimen. |
| Mechanical Properties |
These are the properties of a material that are affected by how the material is processed, including hardness, strength, formability, ductility, stress relaxation resistance, fatigue strength, etc. This is differentiated from physical properties, which do not change with the processing of the material. |
| Microhardness |
A hardness test using a very light load and creating a very small indentation, used to measure the hardness of very small parts. It is sensitive to local variations in the microstructure, so it should be calculated as the average of multiple measurements. |
| Mill Hardening |
A heat treatment that is provided at the production mill, so that the material sold to the customer is already aged and no further heat treatment is necessary. |
| Minimum Arc Current |
The minimum current passing between two contacting surfaces necessary to generate and sustain an electrical arc between them when the surfaces are separated, or the minimum current required to generate an arc when the surfaces are brought together. If the current is less than this value, no arcing will occur. |
| Minimum Arc Voltage |
The minimum voltage between two non-contacting surfaces necessary to generate and sustain an electrical arc between them when the surfaces are separated, or the minimum current required to generate an arc when the surfaces are brought together. If the voltage between the surfaces is less than this value, no arcing will occur. |
| Modulus of Elasticity |
The ratio of stress to strain in the elastic portion of a stress-strain curve. A high modulus describes a stiff material, while a low modulus describes a flexible material. When a part is elastically strained (deformed), the force required to produce this deformation is directly proportional to the modulus. |
| Modulus of Resilience |
The area under the elastic portion of a stress-strain curve. It is a measure of the maximum amount of strain energy that can be stored in the material without inflicting permanent deformation. It can be approximated by dividing the square of the yield strength by twice the elastic modulus. |
| Mushrooming |
A permanent deformation (lateral expansion) of the end of a component subjected to a compressive load, such as the widening of the tips of resistance welding electrodes. |
| n Value |
Another term for the strain hardening exponent. On a true stress-strain curve, the plastic portion of the curve can be approximated by the following equation: Stress= K * Strain^n, where N is the strain hardening exponent and K is the strength coefficient. A higher n value implies greater formability. |
| NACE MR0175/ISO 15156 |
An international standard that provides a set of guidelines for the use of various materials in sour oilfield service. Copper beryllium and ToughMet comply with this standard, although simulation is recommended for service conditions for which test data does not exist. |
| Necking |
The reduction in width and thickness or diameter of a specific point on a tensile test specimen, while the remainder of the specimen experiences no additional reduction. This occurs when the stress exceeds the ultimate tensile strength. |
| Non-Uniform Elongation |
In tension testing, the elongation induced in the test after the point of necking, when only the area that necks will be experiencing any additional elongation. This occurs when the stress exceeds the ultimate tensile strength. |
| Non-Uniform Strain |
In tension testing, the strain induced in the test after the point of necking, when only the area that necks will be experiencing any additional strain. This occurs when the stress exceeds the ultimate tensile strength. |
| Normal Force |
The force between two bodies in contact. Higher contact forces in in electrical connectors result in lower resistance of the contact interface. |
| Omega Processing |
A proprietary processing of Brush Wellman alloy rod and tube resulting in a fine, uniform microstructure and enhanced mechanical properties relative to standard material. |
| Opening Arc |
An electrical arc that forms between the contact surfaces of a separable connector as the contacts are separated, that persists as long as there is adequate current and voltage to sustain the arc. |
| Orange Peel |
A surface disruption on the outer surface of bent components resembling the surface of an orange. It indicates that be bending operation is close to reaching the formability limit of the material. |
| Overaged |
Precipitation age hardened for a longer time and/or at a higher temperature than peak aged material. This results in less strength than peak aged, but results in greater ductility, fatigue strength, and conductivity. |
| Paramagnetic |
Non-magnetic in the sense that random orientation of the magnetic dipoles in the material results in an overall net of zero magnetization. |
| Passivation |
A chemical treatment of a surface, typically involving immersion into a bath, that renders it chemically inert. An example would be immersion of a stainless steel into an acid bath in order to place entirely passive (non-growing) oxides on the surface. It is the opposite of activation. |
| Passive Corrosion |
Self-limiting chemical attack of a metallic surface that results in a small amount of corrosion product that effectively covers the surface and prevents further corrosion from occurring. |
| Peak Aged |
Precipitation age hardened at a time and temperature that provides maximum strength and hardness, at the minimum ductility. |
| Permanent Set |
Permanent strain induced in a part in which the maximum stress has exceeded the yield strength. This is the amount of deformation that remains when the applied load is removed. |
| Photochemical Machining |
Also known as photoetching, this is a method to cut thin strip by applying light-sensitive mask over the areas that are not to be cut, flooding with light, and then chemically etching away the untreated areas, before finally removing the mask. |
| Physical Properties |
These are the properties of a material that are not affected by how the material is processed, including specific heat, conductivity, melting temperature, density, etc. This is differentiated from mechanical properties, which do change with the processing of the material. |
| Physical Vapor Deposition (PVD) |
A coating process in which the component to be coated is placed in a high temperature vacuum chamber, while charged particle bombardment of a target made of the coating material produces releases ions into the vacuum that then deposit and permanently bond to the surface of the workpiece. |
| Pickling |
A process used to remove oxides or scales from the surface of strip that has been exposed to high temperatures. It is typically done by immersion into an acid bath, followed by a water rinse. |
| Pin Bearing Strength |
The maximum stress that a material can withstand without yielding or fracture when a pin is pressed into a matching concave segment of the surface. |
| Pitting |
A corrosion mechanism in which corrosion occurs in a metal underneath small holes in the surface or in a plating layer. |
| Plastic Strain |
Permanent strain induced in a part in which the maximum stress has exceeded the yield strength. This is the amount of deformation that remains when the applied load is removed. |
| Poisson's Ratio |
The ratio of lateral to longitudinal strain in a substance under tension. i.e., it is the percentage that the material stretches in length divided by the percentage that the material shrinks in width. For most metals, the value is approximately 0.3. |
| Pore Corrosion |
Corrosion that occurs to the base metal exposed by pores in a plating layer. The corrosion product may then creep across the plated surface, increasing the electrical resistance of the surface. |
| Porosity |
The presence of small holes in a plating material that exposes the underlying base metal. It is also a void containing air in a cast part. |
| Precipitation Age Hardening |
A heat treatment process in which the alloying elements in a supersaturated solid solution are allowed to precipitate out of solution, putting strain on the crystalline matrix and greatly increasing strength. This is the mechanism by which copper beryllium is strengthened. |
| Precision Elastic Limit |
A test to measure the greatest amount of stress that can be placed on strip in tension without resulting in any appreciable permanent set. It is more accurate than the tensile test at determining the elastic limit but may take hours to run a single specimen. |
| Process Capability Index Cpk |
A statistical measure of the repeatability of a process, based on the frequency with which products produced by the process fall within tolerances. |
| Proportional Limit |
The highest value on the stress-strain curve for which the stress and strain are directly proportional to each other via the elastic modulus. It is usually very close in value to the elastic limit. |
| PV Limit |
The maximum combination of pressure and surface velocity that a material can withstand in a bearing application without failure in some performance criterion, usually by exceeding a threshold in friction coefficient or temperature rise. |
| Quench Hardening |
Rapidly cooling a metal from elevated temperature to create a supersaturated solid solution, that sufficiently strains the crystalline lattice to pin dislocations. Metals strengthened in this way, such as a aluminum bronzes or certain steels become harder, stronger, and brittle. A later tempering treatment can soften these materials and restore some ductility. |
| Quenching |
To quickly reduce the temperature of a component being heat treated below a critical value, usually by plunging the component into a water or oil bath, but sometimes by flooding the component with cool gasses. |
| r Value (Anisotropy Coefficient) |
A measure of the degree of the anisotropy (directionality) of mechanical properties in cold worked materials. In strip material, it is defined as the ratio of the true transverse strain to the true through-the-thickness strain, and is calculated as the negative of the true transverse strain divided by the sum of the true longitudinal strain and the true transverse strain. |
| R/t Ratio |
In bending operations, this is the ratio of the smallest inside radius of the bend to the strip thickness that does not result in cracking of the strip at the bend. The smaller the value of R/t, the more severely the strip can be bent. |
| Recrystallization |
An elevated temperature process in which new crystalline grains form within the existing grains. These new grains grow and consume the old grains, creating an entirely new crystalline structure within the metal. |
| Recrystallization Temperature |
The temperature at which recrystallization of the metal matrix occurs. |
| Reduction of Area |
The maximum reduction in cross sectional area of a test specimen at the conclusion of a tensile test. |
| Residual Stress |
Any stress from fabrication processes that remains in a material after fabrication is complete. |
| Resilience |
A measure of how much a metal can be strained without undergoing permanent set. It is approximated by dividing the yield strength of a material by its elastic modulus. Materials with high elastic resilience such as copper beryllium or ToughMet can withstand much greater strain without permanently deforming than materials with lower elastic resilience. |
| Resistance Welding |
Welding of two components together, by compressing the workpieces between two electrodes and passing sufficient current through them to cause the weld zone to melt. |
| Resistive Heating (Joule Heating) |
Heating of a metal due to an electric current passing through it. Materials with higher conductivity (lower resistivity) will experience a lower temperature rise than materials with lower conductivity (higher resistivity). |
| Rockwell Hardness |
Hardness as measured on one of the Rockwell scales, which uses either spherical or conical indenters. The Rockwell hardness number is proportional to change in penetration when the indentation load increases from its preliminary value to its full value. |
| RoHS (Restrictions on Hazardous Substances) |
European regulations that ban or restrict the use of mercury, lead, cadmium, hexavalent chromium, and certain brominated flame retardants. Copper beryllium alloys are not restricted under RoHS. |
| Rolling |
Reduction in thickness of strip by passing it between cylindrical rollers. Cold rolling is done at a temperature less than the recrystallization temperature, in order to increase the strength of the strip at a penalty of reduced ductility and formability. Hot rolling is done at a temperature above the recrystallization temperature, in order to leave the material soft and ready for further work. |
| Rolling Direction |
The longitudinal, or down the length direction in strip or plate. |
| Rollover |
The initial semi-crushed part of cut or slit edge. On such edges, the initial part of the cut is crushed into a rollover zone, the middle part is sheared straight, and the final part of the cut fractures and breaks away at an angle, potentially leaving a burr pointing in the direction of the cut. |
| Rotating Beam |
A technique designed to produce fully reversed stress in a fatigue test. A cylindrical beam is bent to a desired stress level, and then is rotated about the axis, so that every point on the circumference passes alternately through tension and compression on each cycle. |
| Safety Factor |
The ratio of the yield strength, fatigue strength, or limiting stress value of a material to the design stress in a part made from that material. |
| Secant Modulus |
The slope of a line from the origin of a stress-strain curve to a given point on the curve. In the elastic region of the stress-strain curve, the secant modulus is equal to the elastic modulus. In the plastic region of the curve, the secant modulus will be less than the elastic modulus. |
| Shear |
The straight part of a cut or slit edge. On such edges, the initial part of the cut is crushed into a rollover zone, the middle part is sheared straight, and the final part of the cut fractures and breaks away at an angle, potentially leaving a burr pointing in the direction of the cut. |
| Shear Strength |
The maximum stress that a material loaded in shear or torsion can withstand without permanent deformation. In ductile metals, it is typically 57.7% of the yield strength in tension. |
| Shear/Break Ratio |
The ratio of the sheared area to the fractured area on a cut or slit edge, indicating how tight the tooling clearances are. A tight clearance provides mainly shear, while a loose tolerance is mainly fracture. A ratio of 50% is typically considered optimum. |
| Shock Loading |
Any loading that is suddenly applied to a material, typically by impact, sudden acceleration, or failure of an adjacent load-bearing component. |
| Showering Arc |
An electrical arc that repeatedly forms and extinguishes itself, until the voltage between the arcing surfaces falls below the breakdown voltage. This is a significant source of electromagnetic interference. |
| Silver |
A precious metal plating material that is typically used for connectors in high current applications. |
| Simply Supported Beam |
A simple model of a spring component, with both ends fixed and a force or deflection applied to the middle of the beam. |
| Six Sigma |
A data-driven methodology designed to reduce variation in production, resulting in cost savings and process improvement. |
| Skiving |
A process used to mechanically place a flat groove in a piece of strip material, in order to prepare the strip to receive a clad inlay. |
| Slip Plane |
A plane in the crystalline matrix of a metal through which dislocations are free to move. |
| Slitting |
An cutting operation used to convert a wide coil of strip into two or more narrower coils. |
| S-N Curve |
A curve of fatigue data where the stress level is plotted against the number of cycles to failure. This can help the engineer estimate the number of cycles that a component can be expected to last under a given stress level, or to estimate the maximum design stress that a component can experience in order to survive a given number of cycles. |
| Soft Gold |
Gold plating without any hardening agents. It has less resistance to wear than hard gold, but does not require as much contact force for good electrical contact. |
| Solder Reflow |
A thermal treatment applied to temporarily mated, solder-coated components in order to cause the solder to melt and permanently solder the connections. |
| Soldering |
A bonding technique in which two surfaces are joined by a liquid tin alloy, which is allowed to cool and bond with the two surfaces. |
| Solid Solution Hardening |
Also known as alloying, this is increasing the strength of a metal by dissolving a small amount of another material in it. |
| Solubility Limit |
The point at which a solution is saturated, where no more solute can be dissolved in the solvent without precipitation. |
| Solute |
The material that is dissolved into another to form a solution. |
| Solution Annealing |
A heat treatment in which all of the constituents of an alloy are driven into solid solution, with no precipitates present. In copper beryllium, this recrystallizes the base metal and reverses the metallurgical effects of previous cold work, increasing ductility and the capacity for additional cold work, provided that the material can be quenched to room temperature before precipitation can occur. It also allows the material to later be precipitation hardened. |
| Solvent |
The material in a solution into which the solute dissolves. |
| Sour Service |
A condition in drilling for oil and gas reserves in which the well contains a significant concentration of hydrogen sulfide. |
| Spark Erosion Machining (EDM) |
A machining method in which electrical arcs are transmitted from the cutting tool to the workpiece in order to cut into the workpiece or to remove metal from it. |
| Specific Heat |
A physical property of a material that provides the ratio of thermal energy gained or lost per unit mass divided by the corresponding change in temperature. |
| Spinodal Decomposition |
A strengthening heat treatment in ToughMet and BrushForm 158 alloys, where a solid solution of copper, nickel, and tin decomposes on the microscopic scale to two different phases that are chemically different but structurally identical. |
| Spot Plating |
A method of applying precious metal plating to a substrate in only the area that needs to be plated, eliminating the waste of plating in unnecessary areas. |
| Spot Welding |
Welding two components together at one small point, usually done by resistance welding. |
| Spring Bend Limit |
The amount of stress that a strip sample can experience in bending without incurring any permanent set. It is a function of the strip thickness and orientation relative to the coil set direction. |
| Spring Rate |
This is the ratio of the applied force to the corresponding deflection in a spring contact. |
| Springback |
The tendency of elastic strain to recover in a forming operation. For example, when a part is bent to a 90-degree angle, it will spring back to a larger angle when the forming tool is removed. |
| Springback Ratio |
The ratio of the actual formed angle to the angle of the forming tool (intended angle). |
| Stiffness |
The measure of how much force it takes to produce a given deflection on a part. It is the opposite of flexibility. A still part provides more force at a given deflection than a flexible part. Alternatively, a stiff part will deflect less under a given load than a flexible part. A material with a high elastic modulus has greater stiffness than a material with a low elastic modulus. |
| Strain |
The measure of how much a material is deformed under load. |
| Strain Energy |
The energy required to produce a given amount of strain in a material. |
| Strain Energy Density |
The area under the stress-strain curve up to a given point on the curve. It describes how much energy was required to produce the given strain, or how much energy is stored as strain in the crystalline lattice. |
| Strain Hardening |
Increasing the strength of a material by imparting cold work and causing dislocation entanglement. |
| Strain Hardening Exponent |
On a true stress-strain curve, the plastic portion of the curve can be approximated by the following equation: Stress= K * Strain^n, where n is the strain hardening exponent and K is the strength coefficient. A higher n value implies greater formability. |
| Strength Coefficient |
On a true stress-strain curve, the plastic portion of the curve can be approximated by the following equation: Stress= K * Strain^n, where n is the strain hardening exponent and K is the strength coefficient. |
| Stress |
In a tensile test, this is the force divided by the area of applied force. It is a measure of the energy stored in an object under strain. |
| Stress Corrosion Cracking (SCC) |
Cracking of material at a stress lower than the tensile strength while under corrosive attack. The presence of ammonia tends to cause this to occur in copper alloys. |
| Stress Relaxation |
The tendency of a material to experience a reduction in stress while under constant strain, due to the effects thermal exposure. This means that electrical contacts can lose contact force over time at elevated temperatures, requiring the use of materials with good resistance to stress relaxation like copper beryllium and copper-nickel-tin. |
| Stress Relief |
A thermal treatment to reduce the residual stress in a material, based on the principal of stress relaxation. A thermal stress relief of 1.5 hour at 450°F is adequate to relieve the stress in copper beryllium. |
| Stress-Strain Curve |
A plot of stress against strain obtained through a tensile test. Most of the mechanical properties of a material are derived from this plot. |
| Substitutional Solution |
An alloy in which atoms of the alloying element replace the base metal atoms in the crystalline lattice. |
| Sulfide Stress Cracking (SSC) |
Cracking of material at a stress lower than the tensile strength while exposed to hydrogen sulfide. Copper beryllium and ToughMet have much greater resistance to sulfide stress cracking than hard steel or nickel alloys. |
| Superficial Hardness |
A hardness test on the surface of a material, under a very light load, used to measure the hardness of thin materials, or thin surface layers. |
| Surface Roughness |
The localized variation in height of a surface on the microscopic scale. |
| System Tolerances |
Tolerances specified by the end user on the performance of a device. |
| Tangent Modulus |
In a strict metallurgical sense, the slope of a line tangent to the stress-strain curve at a given point. In finite element analysis (FEA), this refers to the slope of the plastic portion of the stress-strain curve in a bi-linear approximation. |
| Tarnishing |
The tendency of a metal to oxidize over time when exposed to air. This involves no loss of material. Contrast to corrosion, where material is removed from the base metal. |
| Temper |
A description of the particular processing that is done to an alloy to achieve specific property ranges. Tempers typically describe both the cold working and thermal treatments given to a material. Temper also defines a low temperature thermal treatment used to soften quench hardened materials. |
| Temperature Rise |
An increase in temperature due to resistive heating of a material when an electrical current passes through it. |
| Tensile Strength |
The highest stress value obtained in the tensile test in the entire stress-strain curve. This is the point at which brittle materials fail and ductile materials begin to neck down on the way to failure. |
| Tensile Test |
A test used to derive the stress-strain curve of a material. A test coupon is gripped on both ends by the machine, and then is pulled to failure. The elongation of the specimen and the force applied to achieve that elongation are continuously monitored throughout the test, allowing for easy calculation of stress and strain. |
| Thermal Conductivity |
The ability of a material to transfer heat from a hot location to a cold location. A material with a higher thermal conductivity is better able to transfer heat. |
| Thermal Diffusivity |
The ratio of thermal conductivity of a material to the product of specific heat and density. A material with a higher thermal diffusivity is more able to quickly transfer heat. Copper beryllium has a high thermal diffusivity, which enables it to quickly remove heat when used as cores or cavities in plastic molding operations. |
| Thermal Permeability |
The property that determines the temperature at the interface where two bodies of different temperatures come into contact. A higher thermal permeability means a greater increase in the temperature of the cold body and a greater decrease in the temperature of the hot body, more quickly transferring heat. Thermal permeability is a composite property of the interface, not an inherent property of the material on either side of the interface. |
| Thermal Stress Relief |
A thermal treatment to reduce the residual stress in a material, based on the principal of stress relaxation. A thermal stress relief of 1.5 hour at 450°F is adequate to relieve the stress in copper beryllium. |
| Thread Saver |
A component made of copper beryllium designed to fit between the threads of coupled drill string components, used to prevent galling and seizing of the threaded joint |
| Tin Whisker |
A long, thin filament of a tin growing from an electroplated tin surface. In electronic applications, these whiskers could result in short circuits. Tin whiskers can be mitigated by alloying the tin with lead (and risking non-compliance with the RoHS directive), or by reflowing the tin after plating to alleviate internal stresses. |
| Tolerance Stack-up |
An interaction of all of the tolerances on a part that may cause the performance to drift out of the overall system tolerances, despite having all input variables within tolerance. |
| Total Strain |
The amount of strain that a material experiences during a tensile test. It is the sum of the elastic strain and the plastic strain. |
| Toughness |
A measure of how much energy it takes to fracture a material. It is equal to the area under the stress-strain curve of the material. Impact strength (Izod or Charpy) provides a measure of toughness. |
| Transgranular Cracking |
Cracks that propagate directly through the grains in material, as opposed to propagating through the grain boundaries. |
| Transverse |
Oriented in a direction across the width of strip or plate. |
| Transverse Formability |
The formability of the strip in the transverse, or bad-way direction. For alloys strengthened by cold work, it is typically worse than the longitudinal (good way) formability. |
| True Strain |
The strain in a tensile test, calculated by dividing the instantaneous length of the test specimen by its initial length, and then taking the natural logarithm of the resulting quantity. |
| True Stress |
In a tensile test, this is the applied force divided by the instantaneous cross sectional area of the test specimen. Under uniform elongation, the true stress can be calculated by adding 1 to the engineering strain and then multiplying the resulting quantity by the engineering stress. |
| Twist |
Rotational deformation of strip around the longitudinal axis. It can be controlled by notching the edges of the carrier strip. |
| Ultimate Tensile Strength |
The highest stress value obtained in the tensile test in the entire stress-strain curve. This is the point at which brittle materials fail and ductile materials begin to neck down on the way to failure. |
| Under Aged |
Precipitation age hardened for a shorter time and/or at a lower temperature than peak aged material. This results in less strength and conductivity than in peak aged material, but results in greater ductility and fatigue strength. |
| Unidirectional Bending |
Bending strip or other flat product in a fatigue test. The strip is bent in one direction and then returned to its unbent shape before repeating the cycle. This bending method is sometimes referred to as R=0 bending, where R is the ratio of minimum stress experienced in each cycle (in this case 0) divided by the maximum stress. Failure is slower than in fully reversed bending. |
| Uniform Elongation |
In tension testing, the elongation induced in the test up to the point of necking, where all portions of the test specimen show an equal amount of strain. This occurs as long as the stress is less than the ultimate tensile strength. After reaching the tensile strength, only the area that necks will be experiencing any additional elongation. |
| Uniform Strain |
In tension testing, the strain induced in the test up to the point of necking, where all portions of the test specimen show an equal amount of strain. This occurs as long as the stress is less than the ultimate tensile strength. After reaching the tensile strength, only the area that necks will be experiencing any additional strain. |
| Vee-Block Testing |
A method of testing the formability of a strip coupon, by forming a 90 degree bend with a punch and die. The minimum radius of the punch tip that does not cause the strip to crack during bending is reported as the R/t or MBR/t ratio. |
| Vickers Hardness |
Hardness as measured by a Vickers test, which uses a diamond indenter. The Vickers hardness number is proportional to the applied load divided by the area of the indentation. |
| Voice of the Customer |
A method of designing new parts or materials that systematically takes into account and assigns relative weights to customer needs. |
| Water Jet Cutting |
A method of cutting metal where a concentrated stream of water and abrasive particles is directed onto the workpiece. |
| WEEE |
Waste Electrical/Electronic Equipment directive. A European directive that promotes recyclability and limited use of hazardous materials in electronic equipment. It does not restrict copper beryllium in any way. |
| Whiskering |
A tendency of electroplated tin surfaces to grow long, thin filaments of tin from the surface. In electronic applications, these whiskers could result in short circuits. Tin whiskers can be mitigated by alloying the tin with lead (and risking non-compliance with the RoHS directive), or by reflowing the tin surface after plating to alleviate internal stresses. |
| Wipe |
During mating of electronic connects, the two surfaces are typically designed to make initial contact and then slide across each other. This sliding action is called wipe, and it is used to push debris, films, oxides, etc. away from the contact interface, allowing for good electrical contact. |
| Work Hardening |
Increasing the strength of a material by imparting cold work and causing dislocation entanglement. |
| Yield Strength |
A mechanical property derived from the stress-strain curve to approximate the stress level at which a material begins to yield. It is determined by finding the stress level at the intersection of the stress-strain curve with a line drawn parallel to the elastic modulus at a specified strain offset, typically 0.2%. |
| Young's Modulus |
The ratio of stress to strain in the elastic portion of a stress-strain curve. A high modulus describes a stiff material, while a low modulus describes a flexible material. When a part is elastically strained (deformed), the force required to produce this deformation is directly proportional to the modulus. |
| Zone Annealing |
Selective softening of a part by applying a localized heat treatment. An example might be softening the crimp zone of a terminal to allow it to crimp a wire without cracking, while still retaining strength and hardness in the spring on the connecting end of the terminal. |
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