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Stress Rupture Testing

stress_ruptureStress rupture testing determines the tendencies of materials that may break under an overload. During the stress rupture test, material is subjected to a constant load at a constant temperature while the time to rupture is measured. The reported results are very useful in the selection of materials where dimensional tolerances are not critical, but rupture cannot be allowed.

At Laboratory Testing Inc., stress rupture testing complies with ASTM standards and is performed on fully-automated machines that provide the following:

  • Testing at temperatures up to 1850°F
  • Calibrated thermocouples attached to the test specimens to provide the required temperature control
  • Automatic load at various time intervals for reliability and efficiency

Pratt & Whitney (P&W) has qualified LTI as a commercial laboratory for performing Reference MCL Manual Section Appendix 56: Code 3 stress rupture testing. The stress rupture testing systems at LTI also meet with ISO 9000 and ASTM compliance.

stress_rupture_testsTest Methods/Specifications

  • ASTM E139
  • ASTM E292
  • NASM-1312-10

The Stress Rupture Test Process

Stress rupture test machines are designed to apply a static stress to a test specimen at a specific temperature for an extended period of time. The test specimen is machined from a sample of the material in question, according to specific guidelines usually published in a specification. A variety of test specimens can be machined at LTI and used for stress rupture testing, including:

  • Smooth
  • Notched
  • Combination smooth & notched
  • Flat

Stress rupture testing is generally performed at elevated temperatures which may be as high as a few thousand degrees Fahrenheit. During the test, data is plotted showing stress versus time. A straight line is usually obtained at each temperature.

This information can then be used to extrapolate time-to-failure for longer times. Changes in slope of the stress rupture line are due to structural changes in the material. It is important to be aware of these changes in material behavior when extrapolating the data, because they could result in errors.

LTI Capabilities

  • Temperatures – up to 1850°F
  • Compliance – comply with ASTM standards E4, E8, E83, E139, E292, and ISO 9000
  • Approvals – P&W qualified as a commercial laboratory for Reference MCL Manual Section Appendix 56: Code 3 stress rupture testing
  • Test Specimens – LTI’s Machine Shop can provide smooth, notched, combination smooth & notched and flat stress rupture test specimens