Paper 2: Safety and Failure Analysis of Large Diesel Engine Pistons

Abstract

This paper describes investigations that were undertaken to identify the reasons for fatigue failures in cast iron and aluminium pistons of large diesel engines. The work involved experimental and theoretical stress analyses, and fatigue tests were made on specimens cut from actual pistons. It was found that four pistons which suffered fatigue failures had safety factors of 0·60, 0·68, 0·94, and 0·96, while three modified designs which performed satisfactorily were assessed to have safety factors of 1·1, 1·24, and 1·57. Special attention is drawn to the method of fatigue testing in which features typical of the piston are retained.

While it is considered prudent to design for safety factors substantially in excess of unity, the results presented should promote confidence that this approach to the design of components is valid not only in this case but more generally.