Probabilistic material strength degradation model for Inconel 718 components subjected to high temperature, mechanical fatigue, creep and thermal fatigue effects. Final report

Technical Report · Tue Mar 01 00:00:00 EST 1994

OSTI ID:7037707

Bast, C C.S.

This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

• Research Organization: Texas Univ., San Antonio, TX (United States)
• OSTI ID: 7037707
• Report Number(s): N-94-28840; NASA-CR-195284; E-8629; NAS-1.26:195284; CNN: NAG3-867; RTOP 584-03-11
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
INCONEL 718
CREEP
THERMAL FATIGUE
STATISTICAL MODELS
ALLOY-NI53CR19FE19NB5MO3
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
CORROSION RESISTANT ALLOYS
FATIGUE
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCONEL ALLOYS
IRON ALLOYS
MATERIALS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM A
360103* - Metals & Alloys- Mechanical Properties
360104 - Metals & Alloys- Physical Properties