CDA: Cyclic Damage Accumulation life prediction system. User and programmer manual

摘要

A high temperature, low cycle fatigue life prediction method has been developed by Pratt & Whitney under NASA sponsorship through contract NAS3-23288. This method is known as Cyclic Damage Accumulation (CDA) and is designed to account for the effects on creep-fatigue life of complex loadings such as thermomechanical fatigue, hold periods, waveshapes, mean stresses, multiaxiality, cumulative damage, coatings, and environmental attack. Several features of the model make it practical for application to actual component analysis using modern finite element or boundary element methods. Although it has been developed for use in predicting the crack initiation lifetime of gas turbine engine materials, it can be applied to other materials as well. In addition to developing the CDA model and its governing equations, the contract activity was expanded to include the writing of a computer program which performs life predictions using it. This report is a combined User Manual and Programmer Manual for the Cyclic Damage Accumulation (CDA) program. It will describe how to install, run, and modify the CDA program. Section 2 presents a brief theoretical description of the CDA life prediction model. Section 3 contains an input description for the program. Section 4 gives an output description and examples of the error messages and their causes. Section 5 describes program flow and algorithms used. Section 6 contains information on installation of the code and what changes, if any, may need to be made. Section 7 explains how to determine CDA model constants for new materials and what specimen tests are necessary. Section 8 tells how to modify the code to add modes or materials, increase/ decrease the amount of internal storage available, etc. Section 9 is a list of references. Another very significant part of the contract activity was the completion of hundreds of strain-controlled specimen tests on two nickel-base superalloys: cast Bl900Hf and wrought INCO 718. The constitutive behavior of each specimen was recorded and provided the basis for determining the form of the equations required for high temperature life prediction.