Fatigue on engine pistons - A compendium of case studie

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Fatigue on engine pistons - A compendium of case studies

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CASE STUDY

In an automobile, the most stressed component is the piston as it undergoes thermal and mechanical fatigue. It undergoes a huge number of cyclic loading during its lifetime. Piston designs over the decades have transformed but the damage to the pistons due to high pressures and temperatures could not be avoided. The analysis of pistons is a necessary part in the design of engines as it performs a variety of useful functions in the working of engines.

Piston in the Engine fails due to various mechanisms and the origin of failure can be a crack initiated and leading to failure of piston on different regions. These areas are termed as critical regions and high temperature and stresses add on the failure process. Any discontinuity present in the piston such as holes, grooves leads to stress concentration in these areas and becomes region of high stress. A crack is supposed to be initiated in these locations only which propagate through the material and ultimately damages the pistons. Pistons are basically designed on the basis of infinite life working, however in order to safeguard the engine components and piston itself from damage, the pistons are analysed for the safe failure conditions.

In order to have a healthy functioning of the piston cylinder, timely inspections must be performed in order to ensure that the piston is in good shape. The basis inspection that can provide a very clear picture is the visual inspection, where all the potential regions such grooves, holes must be inspected thoroughly. Other testing procedures includes the FEM (finite element method), simulations for thermal fatigue failure, fractography analysis for determining the stresses and hence the critical regions. Testing for thermal analysis may not present a satisfactory result as thermal fatigue may occur due to several reasons. The main thing to be noted while designing a piston is that we cannot avoid the potential regions of crack initiation, but the only thing that can be practiced is to improve the design and the material selection from the strength, weight considerations, economic and safe operational conditions point of view.

The advancement in the technological research in the materials has helped to select the best material which reduces the thermo-mechanical damage to the piston, on the other hand increasing its credibility to work efficiently. The other techniques such as improvised coatings on the piston components which help in the smooth functioning, uniform heat transfer from the piston is recommended. The advancement in design of the piston head, piston body has now proved to be more efficient then the vintage vehicles engines. Continuous efforts are on the roadmap of progress of the better engine design which can bear the high temperatures and stresses and hence provide a longer life to the engine along with cost, weight and fuel reductions.

Fatigue on engine pistons - A compendium of case studies

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