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Questions and Answers
What type of grips are recommended for testing sheet materials?
What type of grips are recommended for testing sheet materials?
Self-adjusting grips standardized dimensions
Why may grips for testing sheet materials not totally represent the properties of the entire end product?
Why may grips for testing sheet materials not totally represent the properties of the entire end product?
They cannot be tested satisfactorily in the usual type of wedge grips.
What are considered satisfactory for acceptance testing of commercial shipments?
What are considered satisfactory for acceptance testing of commercial shipments?
Wedge or snubbing grips
What accuracy and precision are required for dimension-measuring devices?
What accuracy and precision are required for dimension-measuring devices?
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What should testing machines used for tension testing conform to?
What should testing machines used for tension testing conform to?
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What is the effect of eccentric force application on the determination of yield behavior?
What is the effect of eccentric force application on the determination of yield behavior?
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How does the gage length of the extensometer relate to the nominal gage length of the specimen being tested?
How does the gage length of the extensometer relate to the nominal gage length of the specimen being tested?
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Define upper yield strength (UYS) in a uniaxial test.
Define upper yield strength (UYS) in a uniaxial test.
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What is yield point elongation (YPE) in a uniaxial test?
What is yield point elongation (YPE) in a uniaxial test?
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How is the YPE end point determined if the transition occurs over a range of strain?
How is the YPE end point determined if the transition occurs over a range of strain?
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What is uniform elongation in material testing?
What is uniform elongation in material testing?
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How does the fracture distance impact tensile properties in testing?
How does the fracture distance impact tensile properties in testing?
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What is the percentage increase in stress for each 0.025 mm [0.001 in.] of eccentricity in a 9 mm specimen?
What is the percentage increase in stress for each 0.025 mm [0.001 in.] of eccentricity in a 9 mm specimen?
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What does the nominal gage length of a standard 12.5-mm specimen indicate in testing?
What does the nominal gage length of a standard 12.5-mm specimen indicate in testing?
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How is the bending moment and stress added to illustrate the effect of eccentric force application?
How is the bending moment and stress added to illustrate the effect of eccentric force application?
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Study Notes
Terminology and Exceptions
- E8 and E8M test specimens have significant differences in gage length, particularly for powder metallurgy (P/M) materials.
- Exceptions to test methods may be necessary for individual specifications or materials, as seen in Test Methods A370 and B557.
- Room temperature is considered 10 to 38°C (50 to 100°F) unless specified otherwise.
Test Machine Preparation
- The test machine should be exercised or warmed up to normal operating temperatures to minimize errors from transient conditions.
- Measurement of dimensions should be done at the center of the reduced section, where the least cross-sectional area is found.
Tension Test Specimens
- Transverse tension test specimens for tube may be taken from rings cut from the ends of the tube.
- Flattening of the specimen may be done before or after separating the specimen.
- Small-size specimens may be used for large tube under 20 mm (0.750 in.) in wall thickness.
Grips and Dimension-Measuring Devices
- Self-adjusting grips are suitable for testing sheet materials that cannot be tested in usual wedge grips.
- Grips for wire may be of the wedge or snubbing type.
- Dimension-measuring devices, such as micrometers, should be accurate and precise to at least one half the smallest unit of measurement required.
Testing Machines
- Testing machines should conform to the requirements of Practices E4.
- For referee testing, the ends of the 12.5 mm (0.500 in.) wide specimen should be symmetrical within 0.2 mm (0.01 in.).
Measurement and Calculation
- Cross-sectional dimensions of test specimens with rough surfaces may be measured and recorded to the nearest 0.02 mm (0.001 in.).
- The effect of eccentric force application may be illustrated by calculating the bending moment and stress added.
- For measuring elongation, the gage length of the extensometer should be equal to the nominal gage length required for the specimen being tested.
Definitions
- Uniform elongation includes both elastic and plastic elongation.
- Upper yield strength (UYS) is the first stress maximum associated with discontinuous yielding at or near the onset of plastic deformation.
- Yield point elongation (YPE) is the strain separating the stress-strain curve's first point of zero slope from the point of transition from discontinuous yielding to uniform strain hardening.
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Description
Test your knowledge on ASTM standards for mechanical testing methods, significant digits in test data, and verification of extensometer systems. Learn about test specimens, conformance with specifications, and maintaining a specific projected area.