24-10-2012, 02:25 PM
Reliability Quantification of the Flexure: A Critical Stirling Convertor Component
ABSTRACT
Uncertainties in the manufacturing, fabrication process, material behavior, loads, and boundary conditions results in the
variation of the stresses and strains induced in the flexures and its fatigue life. Past experience and the test data at material
coupon levels revealed a significant amount of scatter of the fatigue life. Owing to these facts, the design of the flexure, using
conventional approaches based on safety factor or traditional reliability based on similar equipment considerations does not
provide a direct measure of reliability. Additionally, it may not be feasible to run actual long term fatigue tests due to cost and
time constraints. Therefore it is difficult to ascertain material fatigue strength limit. The objective of the paper is to present
a methodology and quantified results of numerical simulation for the reliability of flexures used in the Stirling convertor for
their structural performance. The proposed approach is based on application of finite element analysis method in combination
with the random fatigue limit model, which includes uncertainties in material fatigue life. Additionally, sensitivity of fatigue
life reliability to the design variables is quantified and its use to develop guidelines to improve design, manufacturing, quality
control and inspection design process is described.
ABSTRACT
Uncertainties in the manufacturing, fabrication process, material behavior, loads, and boundary conditions results in the
variation of the stresses and strains induced in the flexures and its fatigue life. Past experience and the test data at material
coupon levels revealed a significant amount of scatter of the fatigue life. Owing to these facts, the design of the flexure, using
conventional approaches based on safety factor or traditional reliability based on similar equipment considerations does not
provide a direct measure of reliability. Additionally, it may not be feasible to run actual long term fatigue tests due to cost and
time constraints. Therefore it is difficult to ascertain material fatigue strength limit. The objective of the paper is to present
a methodology and quantified results of numerical simulation for the reliability of flexures used in the Stirling convertor for
their structural performance. The proposed approach is based on application of finite element analysis method in combination
with the random fatigue limit model, which includes uncertainties in material fatigue life. Additionally, sensitivity of fatigue
life reliability to the design variables is quantified and its use to develop guidelines to improve design, manufacturing, quality
control and inspection design process is described.