Abstract
A durability design case study concerning a U spring is presented. For a given geometry of the component, the question was to predict the maximum permissible displacement per cycle whilst ensuring a service life of at least 260 kcycles. The stiffness of the spring was evaluated using the finite elements software SolidWorks. As an approximation a linear model was used in the finite elements analysis, which was also compared with an analytical treatment based on Castigliano’s theorem. Using a given safety factor, a high cycle fatigue analysis was performed assuming the use of a steel with 650 MPa ultimate tensile strength. The spring is either loaded by an imposed displacement, or it is load free,i.e.load ratio (minimum load / maximum load per cycle), isR= -1. An algorithm based on finite fatigue life prediction techniques, the Basquin and Goodman diagrams, and the relationship between ultimate tensile strength and fatigue limit was used and will be briefly presented and discussed. Also, the stress analysis helped to highlight the need for some minor geometry changes. The outcome of the study was the evaluation of the maximum permissible displacement per cycle, as required in the real life case addressed.
Highlights
Due to time dependent damage, as in the cases of corrosion, creep, fatigue or combinations thereof, the prediction of the durability of a component or structure is crucial in many engineering applications
Fatigue damage occurs in materials subjected to cyclic loads and eventually leads to rupture; it is a key consideration in the design of structures as aircraft, metallic bridges, ships, or elements of machines as the spring analyzed in this case study
The present case - durability design case study concerning a U spring - falls within the scope of high cycle fatigue studies and use is made of concepts as Basquin law, Goodman diagram and mean stress effect for finite life
Summary
Due to time dependent damage, as in the cases of corrosion, creep, fatigue or combinations thereof, the prediction of the durability of a component or structure is crucial in many engineering applications. The present case - durability design case study concerning a U spring - falls within the scope of high cycle fatigue studies and use is made of concepts as Basquin law, Goodman diagram and mean stress effect for finite life. These topics are briefly reviewed in the context of failure analysis and prevention by Harris and Jur, [1], and more detailed presentations are made by Lee and Barkey [2], Lee and Taylor [3], or Milella [4]. The finite element method was used to study evaluate the stiffness and stress of the component
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