Structural components with complex geometries are frequently subjected to alternating loads, which produce multi-axial stresses. In most cases, the loading is non-proportional. Alternating loads tend to initiate fatigue cracks at notches and at other regions of high stresses. Some typical situations in which fatigue can occur are the repeated expansions and contractions of a pressurised aircraft, a car suspension unit absorbing the undulations of a normal road surface and the rhythmic crashing of waves against hull of a ship. However, occurrence of fatigue is a common phenomenon in many engineering components and their failures are also attributed to fatigue. Knowledge of cyclic deformation behaviour is essential for fatigue analysis of industrial components. However, such knowledge is difficult to obtain for non-proportional loading situations. Although notch deformation can be analysed by methods such as Neuber, these methods are not suitable for critical nonproportional loading paths encounted in industrial components. The aim of this paper is to present cyclic deformation curves for multi-axial varying non-proportional loadings obtained from finite element analysis. The material used was medium carbon steel. It is essential to find the plastic strain ranges under cyclic loads as it is used for fatigue life prediction under variable amplitude tension-torsion multi-axial, non-proportional loops. Hysteresis loops were obtained using ABAQUS Code for different loading conditions of nonproportional loads and the shapes of the loops are discussed for different non-proportional loading paths. Considering the results obtained from different non-proportional multi-axial loading paths, most damaging and the least damaging non-proportional loading paths have been found.
Finite Element, Non proportional loading, multi axial fatigue
 Andrzej BUCZYNSKI and Grzegorz Glinka, 1997, Elastic-Plastic Stress-Strain Analysis of notches under nonproportional loading, Proceeding of the 5th international conference on Biaxial/Multiaxial Fatigue and Fracture Cracow'97, Poland, pp 461-479.
 Segerlind L.J., 1976, Applied Finite Element Analysis, John Wiley and Sons.
 Peterson R.E, 1974, Stress Concentration factors, New York: Wiley
Cite this paper
Nimali T. Medagedara, PDSH Gunawardane. (2018) Finite Element Analysis for Non-proportional loading. International Journal of Mathematical and Computational Methods, 3, 20-27
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