SEDL / STP / STP1461-EB / STP11515S

A New Method for Opening Load Determination from Compliance Measurements

Kujawski, D
Professor, and Graduate Student, Western Michigan University, Department of Mechanical and Aeronautical Engineering, College of Engineering and Applied Sciences, Kalamazoo, MI

Stoychev, S
Professor, and Graduate Student, Western Michigan University, Department of Mechanical and Aeronautical Engineering, College of Engineering and Applied Sciences, Kalamazoo, MI

Pages: 12    Published: Jan 2005

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Abstract

A brief review of the most popular compliance based methods for determination of the crack opening load is included in the introduction. This review reveals the demand for a noise resistant method that is especially needed in the near-threshold region where a partial crack closure prevails and the existing ASTM method does not calculate the correct opening load. With this in mind, a new technique was developed (‘Q’ method). It uses integration instead of differentiation of the compliance data. It also accounts for the partial crack closure situations. The derivation of the Q method is discussed together with its relation to the ASTM procedure, and both methods were used to analyze experimental data of 2324-T39 and 7475-T7351 Al alloys tested at 0.1 and 0.9 load ratios. On average, the crack opening load values from the Q method are smaller by the factor of about 2/π in comparison to those obtained from the ASTM procedure.