Fatigue Testing Services

FATIGUE TESTING USING AXIAL, SHEAR, ROTATING BEAM, HCF/LCF, ELEVATED TEMPERATURE/SUB-AMBIENT METHODS

Fatigue testing is used to determine the lifespan that can be expected from a material or coating subjected to cyclic loading. A metal or non-metallic material's fatigue life is the total number of cycles that it can be subjected to under a single loading setup. A fatigue test can also used for the determination of the maximum load that a sample can withstand throughout a specific number of cycles.
 
The two most common forms of fatigue testing are load controlled high cycle (HCF) and strain controlled low cycle fatigue (LCF). An HCF test determines elastic load characteristics and LCF tests help define plastic deformations. These tests are conducted to examine and evaluate the behavior, susceptibility, and extent of resistance of certain materials to sharp-notch tension, tear, axial fatigue, strain-controlled fatigue, surface crack tension, creep crack, and residual strain.
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AXIAL FATIGUE TESTING

Axial testing methods help characterize mechanical properties of materials, both in static and dynamic conditions, The fatigue resistance measurement of metallic materials subjected to direct stress for relatively large numbers of cycles produces data that helps in choosing the right materials for different applications where components are exposed to axial loading profiles.

To perform a fatigue test a sample is loaded into a fatigue test machine. A load is applied using the pre-determined test stress, then unloaded to either zero load or an opposite load. The loading/unloading cycle is repeated until the end of the test is reached. The test may be run to a pre-determined number of cycles or until the sample has failed depending on the parameters of the test.

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ELEVATED TEMPERATURE FATIGUE TESTING

High-Temperature operating environments affects the fatigue life of many materials. Under the same cyclic or repeated stress or strain loading conditions, a material's characteristics could vary significantly in different temperature environments. Such an environment could be a low, moderate, high temperature or a cyclic temperature that may or may not couple with the cyclic loading.

The test frame's ability to expose the test specimen to temperatures up to 1800°F can replicate the operating conditions experienced by turbine blades in gas engines, power generating plants and jet engines.

The effect of a high temperature on mechanical properties can be associated with transformations of the material's structure due to diffusion processes, aging, dislocation restructuring (softening), and recrystallization.

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SUB-AMBIENT TEMPERATURE FATIGUE TESTING

Sub-Ambient fatigue testing analyzes materials engineered to perform in very low temperature environments, and are subject to very different stresses than in ambient or high-temperature applications. Often, these materials are designed to perform in all these temperature ranges. Various alloys and composites are used in both aerospace and native environments, while still experiencing extreme temperatures. Our cryogenic fatigue testing frames can accommodate temperatures down to -320°F.

The fatigue crack growth rate of metals can be lower at low temperature than typical ambient temperatures.

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ROTATING BEAM FATIGUE TESTING

In rotating beam fatigue testing applications, a bending stress is applied to a round specimen in constant rotation, causing the surfaces of the specimen to experience alternating tensile and compressive stresses.

The basic operating principle of the rotating beam test system is the use of an electric motor in order to rotate a shaft or a test specimen of specified dimensions around its longitudinal axis. The specimen may be mounted either as a simply supported beam or as a cantilever. On application of a known static force through a set of bearings, the resulting bending moment induces alternating tensile and compressive stresses of equal magnitude on the outer surface of the test section in each revolution.

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SHEAR FATIGUE TESTING

Shear Fatigue Testing is used on modern orthopedic and dental implant devices, which often incorporate porous coatings or structures that are designed to promote bone infiltration for biological fixation of the implant. These coatings are often subjected to shear stresses in normal use and the coating must not shear off under those stresses.

Test programs can be designed to determine the performance of these coatings under constant or cyclic application of shear stresses. Test samples are subjected to shear loads parallel to the surface plane in order to evaluate their strength and fatigue life properties. Fatigue testing methods can either be for developing S-N stress-life curves or for completing several run-out tests against predetermined acceptance criteria. Data from these tests can be used to satisfy regulatory requirements, as well as comparing/evaluating coating types and suppliers.

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FATIGUE TESTING STANDARDS

  • ISO 12016
  • ASTM E606
  • ASTM E466

Common coatings tested to ASTM F1104:

  • HA- hydroxyapatite
  • TPA- porous titanium plasma spray
  • DMLS- direct metal laser sintered coatings on implants

RELEVANT ACCREDITATIONS

Click here for a complete list of accreditations and certifications for all IMR Test Labs locations.