Stress Intensity Factors for Cracking Metal Structures under Rapid Thermal Loading. Volume 2. Theoretical Background.

摘要

An SBIR Phase II study has been conducted on a novel method of calculating cracktip stress intensity factors for cracked metal structures under rapid thermal pulse loadings. The work couples a Green's function integration technique for transient thermal stresses with the well-known influence function approach for calculating stress intensity factors. A total of seven most commonly used crack models were investigated in this study. A computer program implementing the methodology designated THERMO-K, was developed and delivered with the Phase II project report. Temperature, stress and stress intensity factor solutions predicted by THERMO-K for all seven crack models have been verified by comparing them with finite element results or experimental measurements. Operable on an IBM-pc or compatible, the program demonstrates the ability to accurately calculate stress intensity factors, with very short turnaround times, and immediate graphics visualization of the results. Based on the success of this Phase II study, it is concluded that the computer program THERMO-K resulting from this study is an easy to use, fast, and accurate tool, for predicting stress intensity factors for a wide range of metallic (or other structures of interest to the Air Force, under rapid thermal pulses. The resulting THERMO-K program would thus be expected to have extensive benefits and commercial applications to the Air Force and other organizations concerned with fracture mechanics and flaw tolerant design of airframe and other structures subjected to thermal transient loading conditions. Keywords: High temperature. (AW)