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Multi-layer steel (MLS) cylinder head gaskets are becoming more widely used to seal an engine. Therefore, it is important to understand the interaction between the engine head, block and head gasket. While experimental methods for determining necessary gasket tightening loads and experimental data relating some gasket design parameters to failure are available, it is very costly and time consuming. A numerical method, such as the finite element (FE) method, has proven to be very useful and efficient in aiding gasket design. A 3D engine FE analysis can predict a number of parameters. Of particular interest are the motion as well as the contact profile of the head, block and gasket. This information, usually difficult or impossible to obtain from a 2D FE analysis, can be used to predict the two most common failure modes of a gasket, fatigue crack and leakage.

Gaskets are used to provide sealing in bolted joints that function under a wide range of assembly and loading conditions. Tolerance distributions of the gasket and flange components as well as assembly load variation will cause the gasket sealing stress to vary. In some cases, this variation is significant. In these cases, gasket designs based on nominal dimensions and loads may not function properly unless one or more engine test and design modification cycles are carried out. A probabilistic technique has been developed to evaluate gasket designs under a range of assembly conditions. The output is a prediction of the statistical distribution of key dimensions such as compressed thickness or parameters such as percent compression. Analysis of these distributions can be used to determine the number of occurrences where a gasket design would be expected to function improperly.

A bolted joint mathematical model is presented which includes flange bending effects. The approach simulates the behavior of a system of elastic flanges, a one component non-linear gasket, and linear elastic bolts subjected to assembly and pressurization loadings. Flange distortion is introduced to the joint diagram to predict the overall, midspan, and under the bolt gasket loads.

The current trend in today's engine environment is dictated by an increased need for higher robustness and performance. Therefore more engine head gasket applications require a fresh and more rigid approach. Currently about 50% of the total cylinder head gasket market is designed and equipped with folded stopper layers. The stopper layer increases the overall robustness of the gasket by increasing both the contact stress in the combustion area and the fatigue life of the functional layers. The increased demand in the diesel segment in Europe and the expected growth in North America will intensify the need for new methods to manufacture these stopper gaskets with higher design flexibility and process robustness in a more economical way. This paper gives an overview of today's methods of manufacture of stopper layers and stopper zones including their advantages and potential to include future enhancements, such as topographic heights for reduced bore distortion.

An embossed single layer of rubber coated metal is a technology that is being applied to the sealing of gasketed joints in internal combustion engines. This technology has the stability of steel, the sealability of rubber, and the control of stiffness through emboss geometry. The sealing performance of this technology is a function of many parameters involving material properties, gasket geometry, surface finish, and joint loading. The relationship between coolant sealability and these parameters was measured. In this paper, results are presented for half emboss configurations where emboss height, surface finish, and clamp load are varied. The data shows that emboss height and flange surface roughness have little effect on the sealing performance of the material studied. The data can be used to select gasket designs which require less expensive flange finishes and lower assembly loads while providing good sealing performance.

Many gaskets have constructions that combine structures of varying compressive stiffness. Low stiffness features may be used for coolant and oil seals; while, extremely stiff components could be used around a fastener as a load stop or around a combustion opening as part of a combustion seal. The use of a high stiffness stopper as part of a combustion seal has a significant effect on the overall behavior of the gasket. The stopper influences the distribution of total bolt load over the entire gasket by concentrating load toward the combustion opening. In the case of multi-layer steel gaskets, fluctuating loads on the combustion seal such as the head lifting force that is generated from the cylinder firing pressure are split between high stiffness stoppers and lower stiffness embosses that surround the combustion opening. In this paper, we will look at the basic mechanics of combustion seal stoppers and consider the effect of the stopper on combustion seal performance.