Engineering Materials Ch 4

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Engineering Materials Ch 4
2013-02-19 11:58:10
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  1.             is defined as the resistance of a material to external elements such as force, load, or weight measured in pounds per square inch (PSI).
  2.               is the amount of deformation or stretch that occurs over a standard gage length (2") expressed in inches or a percentage.
  3. Stress is equal to                 divided by          .
    • Applied force
    • Cross-sectional area
  4. Strain is equal to              divided by             .
    • deformation
    • original length
  5. The four types of stress involved in strengths of materials are:
    a. tension

    b. compression

    c. torsion

    d. shear
  6. The primary objective of the tensile test is to determine the                  a specimen can resist before taking a                set or before         occurs.
    max load, permanent, rupture
  7.              materials will neck down through the plastic range before rupture occurs.
  8.               materials do not neck down significantly; instead, they fail sharply and abruptly at the maximum load(because brittle materials do not exhibit much plasticity).
  9. Proportional Limit
    the stress value at which the elastic portion of the curve loses it's proportionality between stress and strain
  10. Yield Stress
    the top of the elastic region, where the amount of strain increases with little increase in stress.
  11. Tensile strength
    maximum load divided by original area.
  12. Percent Elongation
    • Lf = length at fracture
    • Lo = length original
  13. Percent Reduction of Area

    Ao=Area of original cross section

    Af=Area of final cross section
  14. Modulus of Elasticity
    is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression.
  15. Ductility
    the property that allows a material to deform permanently, under tension.
  16. Malleability
    the property that allows a material to deform permanently, in compression.
  17. Plasticity
    the ability of a metal to be deformed permanently, without failing.
  18. Creep
    The plastic deformation resulting from the application of a long-term load.

    is a slow, but steadily increasing strain applied to a material under load.

    is important in structures as bridges, buildings and other load-bearing structures in which the members are subjected to long-term static loads.
  19. Hardness
    is generally referred to as a material's property that indicates resistance to surface penetration

    may be either static or dynamic.

    is measured by resistance to indentation.
  20. Common static hardness tests:


  21. The             hardness test is the oldest and most established method.
  22. Rockwell Scales
    B - for testing materials of medium hardness.

    C - for testing very hard materials.
  23.                  hardness testers are indentation tests and depend on the calculation of energy absorbed by the specimen during the test.
  24. The general outcome of an impact test is the determination of the energy required to           the specimen.
  25.                   is an indication of how well a material can withstand shock loading.
    Impact stregth
  26.                is used to measure the transfer of energy required to break a given volume of material.
    Impact testing
  27. Two common forms of impact testing are:

  28.              is defined as the failure of a material due to repeated or cyclic stresses being applied to it.
  29.                  is the stress at which a material fails by fatigue.
    Fatigue strength
  30. Three factors affecting fatigue are:

    Composition and structure of the material

    Imperfections such as surface scratches, notches, inclusions, and other defects that can help initiate cracking.
  31. NDT stands for
    Non-Destructive Testing
  32. NDT is typically used to identify defects such as                          , or              that might lead to the failure of the part.
    voids, inclusions, cracks
  33. Four types of NDT testing are:
    magnetic particle

    flourescent penetrant


  34.                   is an applied force that acts in a direction parallel to the plane in which the force is applied.
    shearing stress
  35. Direct shearing occurs when parallel forces are applied in opposite directions.

    Single-shear forces occur along a            plane.

    Double-shear forces occur between               planes simultaneously.
    single, two
  36. When a material is bent or flexed under a load, a portion of the cross section is under        and a portion is under              .
    tension, compression
  37. Somewhere between these two opposing forces is a              line, or axis, separating the forces. Along this axis, the specimen is                        in tension nor in compression.
    neutral, neither
  38. The                   of a beam is the displacement of a point on the neutral surface of a beam from its original position under the action of applied loads.
  39. Compression
    tends to compact or squeeze the specimen.
  40. Torsion
    uses a twisting motion to test the strength of the specimen.
  41. Non-Destructive Testing
    does not render the part unusable for its intended purpose.
  42. Shear
    applies force perpendicular to the primary axis of the part.
  43. Hardness
    measures the resistance to surface penetration.
  44. Flexure
    most commonly used to determine the cross-sectional geometry for a given application.
  45. Fatigue
    uses repeated, cyclic motions to determine the point of failure for a given part or specimen.
  46. Creep
    conducted over a very long period of time.
  47. Tensile
    tends to pull the specimen apart.
  48. Impact
    used to measure the transfer of energy required to break a specimen.