Stress Rupture Testing

Creep Test Capabilities Too

stress_ruptureStress rupture testing and creep testing are performed conveniently and reliably at Laboratory Testing Inc. A stress rupture test applies a constant load to a test sample at a specified temperature until failure. The creep test shows material deformation at temperatures that are generally elevated and under a constant load over time.

Fully Qualified for Reliable Results

At Laboratory Testing Inc., the stress rupture test and creep test are Nadcap accredited, comply with ASTM standards and are performed on Metal test specimens.

The Lab, near Philadelphia, PA (USA), is equipped with fully-automated machines that provide:

  • Testing at temperatures up to 1800°F
  • Calibrated thermocouples attached to the test specimens to provide the required temperature control
  • Automatic load at various time intervals for reliability and efficiency

GE Aviation has approved LTI for stress rupture testing and 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 and creep testing systems used at LTI also meet with ISO 9000 and ASTM compliance.

stress_rupture_testsTest Methods/Specifications

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

The Test Processes

Stress rupture and creep testing are generally performed at elevated temperatures which may be as high as nearly a few thousand degrees Fahrenheit. Stress rupture and creep test machines are designed to apply a static stress to a test specimen at a specific temperature. During the test, data is plotted showing stress versus time.

Why is a Stress Rupture Test performed?

The stress rupture test is used to determine the time necessary to produce failure while material is subjected to constant load at a constant temperature. The test measures time to rupture and the effect of temperature on long-time load-bearing characteristics. The reported results are very useful in the selection of materials where dimensional tolerances are not critical, but rupture cannot be allowed. Stress rupture testing is similar to creep testing, except the stresses are higher.

What happens in a Creep Test?

The creep test is time dependent and measures dimensional changes that occur to a specimen due to high temperature when a constant stress or load, below its yield strength, is applied. The elongation or deformation of the specimen is measured by an extensometer, thereby calculating how a component or part will change in shape during service. Creep testing is valuable for determining the speed at which a component or part will deform at a given load and temperature. This is of particular importance when dimensional control is crucial, so components can be safely designed for high temperature service. This information can then be used to extrapolate time-to-failure for longer time periods.

Test Specimens Machined at LTI

Precision specimens in all configurations are prepared by the fully-capable in-house Machine Shop at LTI. A test specimen is machined from a sample of the material in question, according to specific guidelines usually published in a specification. The variety of test specimens required for stress rupture testing and creep testing include:

  • Smooth
  • Notched
  • Combination smooth & notched
  • Flat

LTI Capabilities

  • Temperatures – up to 1800°F
  • Standards – comply with ASTM standards E139, E292, and NASM-1312-10
  • Nadcap accredited – stress rupture and creep testing
  • Approvals:
    • GE Aviation
    • 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 and creep test specimens

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“Thank you for allowing me to visit your facility and witness a micrometer calibration first-hand, it helped me understand the concept so much better. It is clear that LTI is a wonderful group of people to work with and they operate in a true team environment. Your staff has gone over and above the call of duty to help Superior Tube. We truly appreciate your help.”

Deb Rosenberry,
Superior Tube Inc.


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