Chapter 6
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (17 张)
Engineering Stress and Strain
stress = Force / Original Area Strain = change in length / original length Easy to compute, accurate interpretations of what the material actually experiences only for small deformations
True Stress and Strain
stress = Force / area at time force is applied strain = natural log( current length / original length) Accurately represents what the material experiences at all deformation levels but are difficult to compute.
Tensile Strength
Most Important Material test Gives accurate values for a wide variety of material properties which are valuable in engineering calculations
Tensile Test Elastic Modulus
Slope of the linear, elastic first portion of the curve
Tensile Test Yield STrength
Point from which elastic unloading would result in a 0.2% (0.002) permanent strain
Tensile Test Ultimate Tensile Strength
Maximum value of the engineering stress on the curve
Tensile Test Modulus of Resilience
Area under the elastic portion of the curve Represents energy/volume that can be stored in the material before it yields
Tensile Test Modulus of Toughness
Area under entire curve Represents energy/volume that must be expended to break the material
Tensile Test % Elongation to failure
(final length - original length) / original length *100% fracture strain * 100% Overall measure of ductility
Tensile Test Poisson’s Ratio
Ratio of lateral contraction strain to longitudinal extension strain
Tensile Test % Redunction in Area
(original area - final area)/original area * 100% local measure of ductility at the point of fracture in the neck
Hardness Test
Measure of resistance to indentation/scratching and qualitative measure of strength of the material Found by pressing a spherical, conical, or pyramidal indenter into the material and measuring either the size of the indentation or the depth of penetration Rockwell, Vickers, Brinnel, Knoop, Mohs
Hardness Test Advantages
Easy Cheap Portable Nondestructive to the material
Rockwell Hardness Test
Measures the depth of penetration
Impact Test
Direct measure of energy to fracture a specimen Useful as a pass/fail test for whether a material is tough enough, but does not give nearly as many high quality material properties as tension test
Bending Test
Measure properties of materials that will be used in bending mode and brittle materials which are amenable to tension testing Can get both strength and stiffness data from a bending test, but results are much harder to interpret than tension testing because the stresses in a bending specimen are non-uniform both axially and through thickness
Torsion Test
If done on a thin-walled tubular specimen this is almost as useful as the tension test Harder to perform, harder to interpret, and much less commonly performed than the tension test