Advanced Life Analysis Methods. Volume 3. Experimental Evaluation of Crack Growth Analysis Methods for Attachment Lugs

Abstract : This volume covers the results of experimental evaluation of crack growth analysis methods for attachment lugs which were reported in Vol. II of the final report. These experiments were conducted to assess the damage tolerance of aircraft attachment lugs. The experimental test program included baseline material characterization, crack initiation, residual strength and crack propagation tests. Several loading and geometric complexities were considered in the test program. The types of loading complexities included were constant-amplitude, block spectrum and flight-by-flight spectrum, symmetric and off-axis loadings. Peak stress levels in the lug which were below and above the yield strength of the materials were also included in the test program. The types of geometric complexities considered were straight, tapered, dogbone, clevis and real aircraft lug configurations. Additional geometric complexities considered include lugs with lower thickness and lugs with interference-fit bushings. The experimental results were correlated with the analytical predictions made using methods described in Vol. II of the final report and are presented in this volume. Excellent correlation results were obtained for most of the test cases. In some cases, the developed analytical methods needed some improvements or some new solutions had to be generated. Such efforts were conducted and the refined correlation results are also included in the present volume.