No abstract

In nonlinear applications of computational fracture mechanics, energy release rate techniques are used increasingly for computing stress intensity parameters of crack configurations. Recently, deLorenzi used the virtual-crack-extension method to derive an analytical expression for the energy release rate that is better suited for three-dimensional calculations than the well-known J-integral. Certain studies of fracture phenomena, such as pressurized-thermal-shock of cracked structures, require that crack tip parameters be determined for combined thermal and mechanical loads. A method is proposed here that modifies the isothermal formulation of deLorenzi to account for thermal strains in cracked bodies. This combined thermo-mechanical formulation of the energy release rate is valid for general fracture, including nonplanar fracture, and applies to thermo-elastic as well as deformation plasticity material models. Two applications of the technique are described here. In the first, semi-elliptical surface cracks in an experimental test vessel are analyzed under elastic-plastic conditions using the finite element method. The second application is a thick-walled test vessel subjected to combined pressure and thermal shock loading.

Intermediate test vessel V-8, a 152-mm-thick vessel fabricated of SA533, grade B, class 1 steel, was pressurized to failure at -23°C. The vessel contained a fatigue-sharpened notch adjacent to a half-bead weld repair that had not been stress relieved. Residual stresses and fracture toughnesses were determined before the pressure test by measurements on a prototypical weld, and fracture predictions were made by linear elastic fracture analysis. Predictions agreed well with test results, demonstrating the important influence of high residual stresses on fracture behavior.

1. INTRODUCTION 1 REFERENCES ? 2. DESCRIPTION OF VESSELS 4 DESIGN AND PROCUREMENT 4 MATERIALS CHARACTERIZATION In Traulr and Clurpt V-Nokh Impxi Doij 10 Fractur? T^wyhncs* 14 REFERENCES I: 3. FLAW PREPARATION I" INSTRUMENTATION 33 TEST PROC EDURES »* Vevrl Preparation. . ^^ Piruurc Testing 37 Ultrasonic Moniiurine 37 TEST RESULTS »«• REFERFNf ES <0 5. FRACTURE ANALYSIS METHODS AND RESULTS 51 BACKGROUND 51 MODEL TESTS FOR Ft AW SIZt SELECTION 55

No abstract