A Study on Effect of Residual Stress on Crack Growth of Aluminum Plate
One technique used to enhance the fatigue strength of a fastener hole is to introduce a compressive residual stress field around the hole. An applied load must overcome this residual stress before the crack can grow, thus leading to a longer fatigue life. The cold expansion of the holes is largely employed to obtain improvement in fatigue performance of structures with initially uncracked holes. In this research, considered is a fatigue crack growth from a hole under the influence of residual stress. The entire cold working processing- including hole expansion, elastic recovery, and finish reaming of two aluminum alloys 2024-T351 and 7075-T6 is simulated. This method of fatigue life prediction is compared with a superposition technique and experimental data. The crack closure level is computed from a finite element simulation and a fatigue life is predicted. The conclusions obtained here are beneficial to the understanding of the phenomenon of fatigue crack initiation and growth at the perimeter of cold worked holes.
Weight Functions and Stress Intensity Factor Solutions
Hardbound. An important element of work in fracture mechanics is the stress intensity factor - the characterizing parameter for the crack tip field in a linear elastic material; something reflected in its intense research over the last 30 years. The weight function method is one of the most reliable, versatile, and cost-effective methods of evaluating the stress intensity factors and crack opening displacements. This book provides a valuable account of the author's research in these fields. It has two aims: firstly to provide a theoretical background to the weight function method in fracture mechanics for accurate analysis of two-dimensional crack problems; and secondly, to provide a significant number of stress intensity factor solutions for practical cases. The result is an easy-to-use, accurate analytical method for analysing crack problems, an ideal reference source for graduate students, researchers, and engineers involved with the fracture and fatig
Autofrettage of Cylinders: Prediction of Pressure/External Expansion Curves and Calculation of Residual Stresses:
The shear stress-strain relationship for an initially stress-free 2 1/2 per cent nickel-chromium-molybdenum steel under reversed stress has been determined by twisting thin tubes. The effect of a low-temperature heat treatment given to this material after various amounts of overstrain has been similarly determined.The information so obtained has been used to calculate by methods outlined in Appendixes I and II the behaviour of thick cylinders of the same material when subjected to one or two cycles of internal pressure, with or without an intervening low-temperature heat treatment, and to calculate the stresses throughout the material of these cylinders at any stage in the processes.Such cylinders have been made and subjected to the treatment described, the pressure and dimensional changes being measured at all stages. They have then been bored out in steps until all the overstrained material has been removed, the corresponding dimensional changes being again measured.One of the assumptions used in the ca...