Cylinder Head Gasket Fretting/Scrub Mechanism Investigation and Analysis Procedure Developments 2017-01-1091
Typically, modern automotive engine designs include separate cylinder heads and cylinder blocks and utilize a multilayer steel head gasket to seal the resulting joint. Cylinder head bolts are used to hold the joint together and the non-linear properties of head gasket provide capability to seal the movement within the joint, which is essential for engine durability and performance.
There are three major failure modes for head gasket joint: fluid or gas leakage due to low sealing pressure, head gasket bead cracking due to high gap alternation and scrubbing/fretting due to pressure and temperature fluctuations causing lateral movement in the joint. During engine operation, the head gasket design should be robust enough to prevent all three failure modes and the resulting design must consider all three major failure modes to provide acceptable performance. Analysis methods to address the first two failure modes (low sealing pressure and bead cracking) are well developed and common within the industry. This paper is focused on the development and utilization of an analytical model for the gasket scrubbing/fretting failure mode.
First, a basic understanding of the gasket scrubbing and fretting mechanisms is investigated. Based on an understanding of the fundamental mechanisms, an analysis procedure is developed and critical design parameters for scrubbing and fretting are defined. The developed method is employed for cylinder head gasket joint design to prevent scrubbing and fretting, and the critical design parameters are discussed.