Fatigue and Fracture Toughness Testing

Fatigue testing applies cyclic loading to a test specimen, to understand its performance under similar conditions when in actual use. The load application can either be a repeated application of fixed load or simulation of in-service loads. The load application may be repeated millions of times and up to several hundred times per second.

 

Many engineering metals and alloys display embrittlement at reduced (below sub-zero) temperatures. Structures fabricated from them fracture or shatter unexpectedly at low temperatures when loaded to stress levels at which performance would otherwise be satisfactory at room temperature. To avoid such incidents, selection of the right material can be done by testing them for their mechanical properties.

 

In the recent years, tremendous interest has been generated in fracture toughness testing based on linear elastic fracture mechanics. Fracture mechanics principles have been used to quantify safety factors in structural design, taking into account crack propagation and/or brittle fracture. Most structural members, components, vessels, piping, aviation, and aerospace are designed according to analysis criteria that guard against failure. CTOD testing requirement is most common in welded coupon as recommended in ONGC, EIL, DNV & API specification.

 

TCR Engineering has expanded its capabilities to include fatigue, fracture toughness, CTOD and high-temperature tensile testing with the addition of two fatigue systems with the Universal Testing Machine which has a capacity of 50 kN and 250 kN. The versatile Servo-hydraulic systems will allow the mechanical testing laboratory to perform numerous types of fatigue tests on different specimen sizes and orientations, in the temperature range from ambient to 1000° C. TCR has the capability of applying linear displacements, utilizing linear and hydraulic actuators. Comparison fatigue testing of OEM and alternate source parts can also be performed to demonstrate equivalency of fatigue life.