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  • Material Testing

  • Material Testing Reproducible evaluation of material properties

    Material response to varying loading

    conditions, including magnitude, cycling,

    and mode

    Dynamic Testing

    Material response to constant loading

    Static Testing

  • Static Material Testing

    Strength

    Deformation

    Fracture

    Design requirement compliance

    Tensile test

    Compression test

    Hardness test

    Evaluation of Material

    Standardized Tests

  • Tensile Test Uniaxial

    A straight line axial force is

    applied to a test sample

    (typically in the y axis)

    Destructive Force is applied until sample fails.

    Image courtesy of NSW Department of Education and Training

    Hounsfield Tensometer

  • Tensile Test

    Ensures meaningful and reproducible results.

    Uses a uniform cross section.

    Standard Test Sample (dog bone)

  • Tensile Test Procedure Dog bone is created to test specifications

    Dog bone is secured in tester

  • Tensile Test Procedure A tension force (F) is applied to the dog bone until failure occurs.

    Simultaneously the applied tension force (F) and dog bone elongation (d) are recorded.

    A plot is created from the stored load

    elongation data.

    F

    d

  • Tensile Test Data

    F

    d

    Test sample A and B are 230 red brass. Test

    sample A has a diameter of 0.125 in. Test

    sample B has a diameter of 0.375 in.

    If both samples are tested to failure, will the

    applied tension force and elongation be the

    same for both tests?

    A

    B

    NO Why?

  • Tensile Test Data

    Load-elongation results are dependent upon

    sample size.

    How can test data be manipulated to

    represent a material and not an individual

    test sample?

    Larger sample indicates larger load-elongation.

  • Tensile Test Data

    To eliminate test results based on sample

    size, calculate sample stress.

    Divide load (F) by the original test sample

    cross-sectional area (A0)

    Stress is load per unit area.

    lo

    stread

    ss =area

    F = A

  • Tensile Test Data

    Calculate the stress in the dog bone with a

    430 lb applied force.

    2area = r

    2area = (0.0625 in.)

    2area = 0.0123in.

    F = A

    2

    430 lb

    0.0123 in.

    35,000 psi

  • Tensile Test Data

    Manipulating Elongation Results

    To eliminate test results based on sample

    size, calculate sample strain.

    Strain (e) is the amount of stretch per unit

    length.

    Elongation (d) under load, divided by the

    original length (L0)

    amount of stretchstrain =

    original length

  • Tensile Test Data Calculate the strain in the dog bone with an

    elongation of 0.0625in.

    0.0625in. =

    1.000in. = 0.0625

    amount of stretchstrain =

    original length

  • Tensile Test Stress-Strain Curve

  • Elastic Range

    Initial response is linear.

    Stress and strain are proportional

    to one another.

    Tensile Test Stress-Strain Curve

    Proportional

    Limit

  • Proportional Limit

    Stress at which material starts elongating

    more than the proportion in force.

    Tensile Test Stress-Strain Curve

    Proportional

    Limit

  • Modulus of Elasticity (E)

    The proportional constant (ratio of

    stress and strain).

    A measure of stiffness The ability of a

    material to resist stretching when loaded.

    An inherent property of a given material.

    stressE = =

    strain

    Tensile Test Stress-Strain Curve

  • If the load is removed, the

    test sample will return to

    its original length.

    The response is elastic or

    recoverable.

    Exaggerated stretch to

    illustrate principle

    Tensile Test Stress-Strain Curve

  • Elastic Limit = Yield Point

    Uppermost stress of elastic behavior .

    Elastic limit and yield strength mean the

    same thing.

    Elastic limit and proportional limit are

    almost identical, with the elastic limit being

    slightly higher.

    Tensile Test Stress-Strain Curve

  • Resilience

    The amount of energy per unit volume

    that a material can absorb while in the

    elastic range.

    Area under the stress-strain curve.

    Why would this be important to designers? Hint:

    car bumper 1 bh2

    Tensile Test Stress-Strain Curve

  • Yield Point

    When the elastic limit is exceeded.

    A very small increase in stress

    produces a much greater strain.

    Most materials do not have a well-

    defined yield point

    Tensile Test Stress-Strain Curve

  • Offset Yield Strength

    Defines the stress required to

    produce a tolerable amount of

    permanent strain.

    Common value is 0.2%

    Tensile Test Stress-Strain Curve

  • Plastic Deformation

    Unrecoverable elongation beyond

    the elastic limit.

    When the load is removed, only the

    elastic deformation will be recovered.

    Tensile Test Stress-Strain Curve

    Yield

    Point

  • Tensile Test Strength Properties Stress Strain Curve

    Plastic deformation represents failure.

    Part dimensions will now be outside of

    allowable tolerances

  • Plastic Deformation without necking

    Elongation continues, some is permanent

    Cross-section decreases along entire

    sample.

    Load can continue increasing.

    Tensile Test Stress-Strain Curve

  • Tensile Strength

    Load bearing ability peaks.

    Less force is now required to

    continue elongating.

    Weakest location begins to

    decrease in area more than other

    locations Necking

    Tensile Test Stress-Strain Curve

  • Plastic Deformation with Necking

    Sample can now be stretched with less

    force.

    Tensile Test Stress-Strain Curve

  • Tensile Test Stress-Strain Curve

    Failure

    If continued force is applied,

    necking will continue until fracture

    occurs.

    Ductility

    Amount of plasticity before fracture;

    The greater the ductility, the more a

    material can be deformed.

  • Compare the material properties of these

    three metal samples.

    Tensile Test Samples

  • Brittleness

    Material failure with little or no ductility.

    Lack of ductility, not lack of strength.

    Tensile Test Stress-Strain Curve

  • Toughness Work per unit volume required to fracture a material.

    Total area under the stress-strain curve from test

    initiation to fracture (both strength and ductility).

    Tensile Test Stress-Strain Curve

  • Tensile Testing Examples

    steel rebar tensile test

    steel cylinder tensile test

    welded steel

    concrete cylinder

    metal cable

    http://www.youtube.com/watch?v=YdqvGGFIbfchttp://www.youtube.com/watch?v=W5A8gU37wGghttp://www.youtube.com/watch?v=cbdyxnOOiHAhttp://www.youtube.com/watch?v=8c_vPBGi6lkhttp://www.youtube.com/watch?v=2J-AHvOjMN0

  • Stress and strain relationships are similar to tension

    tests elastic and plastic behavior

    Test samples must have large cross-sectional area

    to resist bending and buckling

    Material strengthens by stretching laterally and

    increasing its cross-sectional area

    Compression Test

    Video examples

    concrete test

    composite test

    soda can

    concrete 2

    http://www.youtube.com/watch?v=X9QQD5UM9FI&feature=relatedhttp://www.youtube.com/watch?v=X9QQD5UM9FI&feature=relatedhttp://www.youtube.com/watch?v=X9QQD5UM9FI&feature=relatedhttp://www.youtube.com/watch?v=X9QQD5UM9FI&feature=relatedhttp://www.youtube.com/watch?v=PpOWnsOXX6whttp://www.youtube.com/watch?v=b0YJgr9u0HQhttp://www.youtube.com/watch?v=WC6AgX2N1Go

  • Resistance to permanent deformation.

    Resistance to scratching, wear, cutting or

    drilling, and elastic rebound.

    Brinell Hardness Test A tungsten carbide ball is held with a 500 lb

    force for 15 sec into the material.

    The resulting crater is measured and

    compared.

    Hardness Testing

    Brinell testing video

    http://www.youtube.com/watch?v=Csm8buOxdekhttp://www.youtube.com/watch?v=Csm8buOxdekhttp://www.youtube.com/watch?v=Csm8buOxdek

  • Rockwell Test A small diamond-tipped cone is forced into

    the test sample by a predetermined load

    Depth of penetration is measured and

    compared.

    Hardness Testing

    Rockwell testing video

    http://www.youtube.com/watch?v=YPgxXKP42Ck

  • Resources

    NSW Department of Education and Training (2011). Retrieved from

    http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/tensile_testin

    g/index.htm?Signature=%287e02281c-318a-461b-a8ed-

    3394db0c4fe6%29

    Askeland, Donald R. (1994). The Science and Engineering of

    Materials, 3rd ed. PWS Publishing: Boston.

    http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/tensile_testing/index.htm?Signature=(7e02281c-318a-461b-a8ed-3394db0c4fe6)http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/tensile_testing/index.htm?Signature=(7e02281c-318a-461b-a8ed-3394db0c4fe6)http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/tensile_testing/index.htm?Signature=(7e02281c

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