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A new computerized method using a thin, flexible sensor to measure stress distribution during loading and unloading of gaskets is disclosed. Stress measurement is achieved by a change in the sensor's electrical resistance as a function of load. Each sensor has many electrical pressure responsive contact points that give a map of stress. The unloading of a gasket due to hydrostatic end forces, thermal motions, and external loads can be observed and measured without modifying the flange environment. Use of this new technology permits better and faster gasket and flange design optimization. Monitoring of gasket stress during unit operation is also possible in some cases. The system uses a personal computer operating specially developed graphics software. It provides visual two and three dimensional dynamic stress distribution representations as well as total compressive force, on the sensor, in real time.

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.

Cylinder head gasket problems are identified and discussed for indirect combustion light duty diesel engines. Bi-metal considerations, engine testing, force analysis, precombustion chamber factors, gasket coatings and surface finish of the mating flanges are reviewed. Included is a discussion of various design approaches used for the cylinder head gasket.

A gasket material fluid sealability test system has been developed using a fixture analogous to a bolted joint in an internal combustion engine. This system applies uniform load, simulates bolted joint rigidity, and measures leakage rate. It also measures load loss as a function of the material stress relaxation. It can be used with most liquids and gases over a broad pressure range. Novel concepts are employed to improve fluid sealability testing, such as an innovative method of applying bearing load and electronic data acquisition that assures accuracy and increases operator productivity.

Many of the gaskets used in modern performance engines need to incorporate different design configurations than their counterparts which are used to seal similar engines installed in passenger cars. In this paper some of these different configurations are identified.

Using the Lucas Compression Stress Relaxometer, the effect of cycling heating and cooling on retention of sealing force of various elastomers is presented. The study includes the effect of exposure of the sealing material to air, engine coolant, and motor oil. Thermal expansion, stress relaxation, and polymer swell or shrinkage are related to sealing force retention. Variations in formulation vs sealing force retention are explored.

THERE ARE A VARIETY of combustion seal designs used throughout the world for sealing the combustion gases of internal combustion engines. This paper describes a number of the designs and discusses the sealing theory inherent in them. Static and dynamic physical properties as related to sealing performance are discussed.

The response of a gasketed, bolted joint to an external load is understood to be effected by all components involved in the joint. The analysis involves the equilibrium of the gasket compressive force with the bolt tension force and the forces external to the bolted joint. Geometric compatibility is maintained when the change in the stretch of the bolt caused by an external force is equal to the change in compressed thickness of the gasket. When the flanges are treated as nondeformable, the classical joint diagram analysis indicates that externally applied loads, which unload the gasket, increase bolt tension. In this paper, the effect of flexible flanges is included in the analysis of simple gasketed bolted flanges. The results show that bolt tension response can deviate significantly from the rigid flange behavior. In certain situations where flanges have a relatively high level of flexibility, external joint forces that unload the gasket also unload the bolt.