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Definition
| used for the Rockwell hardness test. Small indenter, either a small diameter steel ball or a diamond tipped 12 degree cone, is firmly seated against the material |
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Term
| breaking strength (fracture strength) |
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Definition
| the stress as which fracture occurs, for relatively ductile materials, the breaking strength is less than the ultimate tensile strength and necking precedes fractures. Brittle material, fracture normally terminates the stress-strain curve before necking and maybe plastic flow |
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Definition
| one of the earliest accepted methods of measuring hardness (might want to read the whole paragraph!) |
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| Brinnel hardness number (BHN) |
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Definition
| equal to the load (500, 1500, 3000 kg) divided by the surface area of the spherical (2-5 mm) indention when the units are expressed as kilometers per square millimeter. |
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| when material fails with little or no ductility they are brittle—simple lack of significant ductility, should not be confused with lack of strength |
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Definition
| utilize specimens that are supported as beams. The standard specimen contains a V, keyhole, or U-shapes notch. The test specimen is supported on the ends and the impact is applied to the center, behind the notch, to complete a 3-point bending. |
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| long-term exposure to elevated temperatures can lead to failure by a phenomenon. If a tensile type specimen is subjected to a constant load at an elevated temperature, it will elongate continuously until rupture occurs. The rate of elongation is small, but creep should be considered when designing equipment (stream or gas turbines, power plant boilers..) |
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Definition
| rate of elongation in the 2nd stage (long, elongation is somewhat linear) elongation verse time plot. The higher the temperature or with higher applied loads would have higher creep rates and shorter rupture times. |
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Definition
| defect in a material, according to philosophy of fracture mechanics. Defects whose size remains unchanged through the lifetime of the part and are permissible.o It is a major goal of fracture mechanics to define the difference between dormant and dynamic for the specific conditions of material, part geometry, and applied loading. |
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Term
| ductile-to-brittle transition temperature |
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Definition
| the temperature at which the response goes from high energy absorption to low energy absorption. All steels tend to exhibit this transition when temperature is decreased-varies with carbon content and alloy. |
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Definition
| amount of plasticity that precedes fracture (might want to read more?) |
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Definition
| used when testing soft, elastic materials such as rubbers and non-rigid plastic. It measures the resistance of a material to elastic penetration by a spring-loaded conical steel indenter. No deformation occurs. |
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Definition
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Term
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Definition
| up to a certain stress, if the load is removed, the specimen will return to its original length. The response is elastic and the uppermost stress for which this behavior is observed is known as the elastic limit. For most materials elastic and proportional limit are almost identical with elastic being slightly higher. |
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Definition
| May also be important design considerations. Theses properties will vary not only with the material, but also with the way the material has been processed and the temperature. |
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Definition
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Term
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Definition
| (delta)L, for a given weight, the magnitude of elongation depends on the original length of the bar. The amount of elongation for each unit length, expressed as e=(delta)L / L, called unit length. |
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Definition
| the value of stress below which the material will not fail regardless of the number of load cycles. Also called endurance strength. May be an important criterion in many designs. |
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Term
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Definition
| symbol-e. Stress-strain curve, e is elongation (delta)L divided by original gage length Lo(L not). |
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Term
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Definition
| symbol-S. applied load W divided by the original cross-sectional area Ao(Anot). Goes with engineering strain. |
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Definition
| materials can also fail by fracture if they are subjected to repeated applications of stress, even though the peak stresses have magnitudes less than the ultimate tensile strength and usually less then the yield strength. Fatigue can result form either the cyclic repetition of a particular loading cycle or entirely random variations in stress and have been associated with almost 90% of all metallic fractures. |
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Term
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Definition
the maximum stress that can be sustained for a specific number of loading cycles
o Figures 2-25 stress verse number of cycles, of S-N curves, and summarize the results of multiples fatigue tests. Any point on the curves is fatigue strength. |
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Term
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Definition
| electron microscopy may be required to reveal ridges(striations), they are characteristics of fatigue failure |
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Definition
| refers to a material’s suitability for a plastic deformation processing. Since a material often behaves differently at different temperatures a material with good ‘hot formability’ may have poor deformation characteristics at room temperature. Materials that flow nicely at low deformation speeds may behave in a brittle manner when loaded at rapid rates. Formability needs to be evaluated for a specific combination of material, process, and process conditions. The results cannot be extrapolated or transferred to other processes or process condition. |
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Term
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Definition
| quantity that describes the resistance of a material to fracture or crack growth, which is usually denoted by K with subscripts to signify conditions of testing. Part of fracture mechanics. |
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Term
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Definition
| specific length. Elongations will vary with different gage lengths, it is important to remove these geometric or size effects to produce data that are characteristics of a given material (not a specific specimen), use original length (read for better understanding) |
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Definition
| very important, but hard to define property of engineering materials. Many tests, based on resistance to permanent deformation (indentation) under static of dynamic loading (most common). Other tests evaluate resistance to scratching energy absorption under impact loading, wear resistance, or resistance to cutting or drilling. Since the tests are different they don’t always correlate. |
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Term
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Definition
or specific heat. The amount of energy that must be added to or removed form a given mass of material to product a 1 degree change in temperature.
o This is important in processes such as casting, where heat must be extracted rapidly to promote solidification, or heat treatment, where large quantities of material are heated and cooled. |
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Term
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Definition
| cantilever beam and is impacted at the end. Some supply a predetermined impact energy in the form of a swinging pendulum. After breaking of deforming the specimen, the pendulum swings upward with an energy equal to its original minus that absorbed by the impacted specimen. The loss of energy is measured by the angle that the pendulum obtains during the upward swing. (Can read more!) |
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Definition
evaluates the fracture resistance of a material when subjected to impact (dynamic load).
o Two basic types
1) bending impacts—Charpy and Izod tests
2)tension impacts |
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Definition
hardness value, obtained by dividing the load in kilograms by the projected area of the indentation. Expressed in square millimeters.
o For Vickers and Knoop tests- series of knoop indentations progressing (left to right) across a surface-hardened steel specimen (hardened surface to unhardened core). |
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Term
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Definition
| depends not only on the material being machines but also on the specific machining process and the aspects of that process that are of greatest interest. Machinability ratings are generally based on relative tool life data. May mean different things to different people, it frequently involves multiple properties of a material acting in unison (ex. How easy or fats a metal is cut…) |
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Term
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Definition
how material responds to applied load
Metal-material having properties of luster, high thermal conductivity, high electrical conductivity, ductile, and some have good magnetic properties |
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Definition
| static indentations made with loads not exceeding 1 kg-force (9.81 N) |
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Term
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Definition
| the proportionality constant, or ratio of stress to strain also known as Young’s modulus |
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Term
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Definition
| the process by which a ductile material deforms under tension forming a thin neck |
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Definition
| properties vary widely, less ductile, weaker, and less dense than metals, poor electrical and thermal conductivities |
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Term
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Definition
| the value of stress that will produce a given but tolerable amount of permanent strain |
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Term
| Percent reduction in area |
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Definition
| measure of ductility, occurs in the necked region of the specimen. R.A.=(Ao-Af)/Ao*100% Ao= original cross sect. area Af=smallest area in necked region |
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Term
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Definition
| density, melting point, optical properties(transparency, opaqueness, color) thermal properties: specific heat, coefficient of thermal expansion and thermal conductivity, electrical conductivity and magnetic properties |
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Term
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Definition
| when elongation beyond the elastic limit becomes unrecoverable |
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Term
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Definition
| the stress at which the strain and stress direct proportionality ceases to exist |
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Definition
| property of a material to absorb energy when it is deformed elastically and then, upon unloading to have this energy recovered, maximum energy per unit volume that can be elastically stored |
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Term
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Definition
| widely used, hardness value determined through an indentation produced under a static load can’t be used on thin materials, rough surface, or non-homogeneous materials |
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Term
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Definition
| a plot of stress (S) against the number of cycles to failure (N) a log scale is almost always used for N. |
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Term
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Definition
| hardness measured by the rebound of a small diamond-tipped hammer that is dropped from a fixed height onto the surface of the material, evaluates resilience of a material |
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Term
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Definition
| amount of energy that must be added to or removed from a given mass material to produce a 1 change in temperature |
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Definition
| - characterization of the behavior of materials under static loads, used to qualitatively rate and compare materials |
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Definition
| when a force/load is applied, a material is deformed or distorted |
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Definition
| when metals become harder and stronger when they are plastically deformed |
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Definition
| a force/load being transmitted divided by the cross-sectional area transmitting the load, Stress=weight/area, megapascals or lbs./in2 |
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Definition
| multiple tests conducted over a range of temperatures and stresses and the rupture time data collected into graph, provides overall picture of material performance at elevated temperatures |
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Definition
| tests a material's strength. a pulling force is applied to a material from both sides until the sample changes its shape or breaks |
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Term
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Definition
| measures the rate at which heat can be transported through a material |
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Term
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Definition
| most materials expand upon heating and contract upon cooling, but the amount of expansion and contraction will vary with the material |
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Term
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Definition
| the work per unit volume required to fracture a material |
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Term
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Definition
| temperature at which a material changes from one crystal state to another |
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Term
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Definition
| - summation of the incremental strains that occur throughout a test =ln(L/Lo) |
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Term
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Definition
| , computed by taking simultaneous readings of the load and the minimum specimen diameter =Weight/Actual Area |
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Term
| Ultimate tensile strength |
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Definition
| the stress at which the load bearing ability of a material peaks |
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Term
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Definition
| most common static test, standard specimens ensure meaningful and reproducible results and designed to produce uniform uniaxial tension in the central portion and reduced stresses in sections that are gripped |
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Term
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Definition
| similar to Brinell test but uses a square-based 136 diamond pyramind as the indenter with increased accuracy |
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Term
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Definition
| also known as jointability, ability to be welded |
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Term
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Definition
| the point at which the elastic limit is exceeded, increases in strain no longer require proportionate increases in stress |
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Term
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Definition
| the proportionality constant, or ratio of stress to strain also known as modulus of elasticity |
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