HATFIELD, PA– Laboratory Testing Inc. (LTI), materials testing, nondestructive testing and metrology lab, recently introduced fatigue crack growth testing as one of its mechanical testing services. LTI’s lab performs fatigue crack growth testing, also called da/dN testing, according to the ASTM E647 standard. Constant load, increasing, decreasing and constant delta K, and constant Kmax control methods are offered. The test can be performed at temperatures between -250°F and 400°F and at loads running from 50 lbs. to 55, 000 lbs.

The fatigue crack growth test generates a curve displaying the crack growth rate as the cyclic stress intensity factor (delta K) is varied. The test results also provide the data points and a da/dN-dK plot. Additionally, LTI also has the capability of providing customers with threshold and Paris Law values. Laboratory Testing works with customers to provide adaptable testing for specific testing and engineering needs.

The fatigue crack growth test reports the resistance of materials to stable crack extension under cyclic loading. Compact Tension (C(T)) and Middle Tension (M(T)) specimen configurations are supported in a variety of sizes. The M(T) specimen is primarily used for sheet materials, and the C(T) is used for a range of different material forms including sheet, plate, bar and forgings. Starter notches are formed using wire EDM.

Fatigue crack growth rates from the threshold regime to the critical region are typically developed using constant load or K-controlled parameters. The automated fatigue crack growth testing system at LTI uses MTS closed loop servo-hydraulic load frames controlled by FTA ADWin based system. Crack length is monitored using the compliance (FCGR-C) method.

Laboratory Testing Inc. provides fatigue crack growth testing through its Mechanical Testing Department, which also performs fracture toughness, hardness, impact, stress rupture and tensile testing. These other services are accredited by A2LA to ISO/IEC 17025 and by PRI/Nadcap, ensuring accurate and reliable results.