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Technical Paper

The Effect of Flange Flexibility on the Response of Gasketed Bolted Joints Subjected to External Forces

1997-02-24
970524
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.
Technical Paper

Sealing Performance of an Embossed Rubber Coated Metal Gasket

1995-02-01
950328
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.
Technical Paper

A Probabilistic Gasket Design Method

1995-02-01
950765
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.
Technical Paper

A Design/Analysis Method of Gasketed Bolted Joints for Noise/Vibration Control

1995-09-01
952087
A large portion of the noise transmitted from an engine is a result of structural born vibration which may be radiated through the various pans and covers of the engine if they are not isolated from the engine through the gasketed bolted joints. This paper presents an analytical approach for the design of gasketed bolted joints when vibration isolation is required. A simulation of the scaling and isolation performance was created to include the effects of design, temperature, material properties, and loading conditions on the functionality of the noise isolation/sealing system. A systematic design process is developed and applied to the development of an oil pan gasket/noise isolation system.
Technical Paper

A Method for Determining the Load-Deflection Curve of an Elastomeric Gasket

1996-02-01
960217
The gasket cross section plays an important role in the resultant total load, contact stress, and stiffness of a gasket constructed from elastomeric materials. One standard approach to design is based on using a shape factor in conjunction with a simple stiffness calculation. This approach can produce reasonable results for simple cross-sections under small deformation. In many situations, the complexity of the shape and relatively large deformation prevents this approach from predicting the behavior of the gasket with acceptable accuracy. Experimental approaches and finite element methods are effective at characterizing the stiffness under these conditions. In this paper, a parameter study of the results of a sequence of finite element analyses were used to construct a model of standard gasket cross sections, specifically a triangular beaded cross section. The resulting formula can be used to quickly determine the gasket load-deflection with good accuracy.
Technical Paper

Development of a Computer Aided Gas Sealability Test System

1996-02-01
960213
A test system is presented that performs gas sealability tests on gasket materials and components. The system is computer controlled and capable of providing elevated compressive loads and gas pressures. It incorporates a personal computer controller interface, a hydraulic load frame, and integrated gas pressure control. Gas leakage is measured using a mass flowmeter. It performs several multiple-condition tests, the most important being a load sequence sealability test at constant gas pressure and a pressure and load sequence sealability test. The test system provides for automatic test control and data acquisition, so that the test sequences can run unattended. An overview of sealability test methods is included to provide perspective regarding this development.
Technical Paper

Flange Bending Model and Its Application to Bolt Span Specification

1998-02-23
980579
The oil sump sealing performance analysis has been carried out through the analysis of the joint formed by the sump flange, the engine block flange, the gasket, and the bolts. Oil sump flange bending plays a major role in affecting the gasket sealing performance, it is modeled using 3D shell element and reduced to a substructure stiffness matrix for the sealing surface. This reduced stiffness matrix along with the stiffness of the gasket and bolt are used in a 2D plate program to provide detailed gasket pressure profile on the sealing surface. The effect of sump wall height, corner bend, boundary conditions have been studied in detail to make sure that the lowest sealing pressure on the entire flange is at least equal to or larger than the predicted value. The effect of bolt spacing on the sealing pressure has also been studied, the results of which can be used as a guideline for bolt spacing specification in new engine development.
Technical Paper

The Role of the Stopper in the Mechanics of Combustion Seals

1998-02-23
980575
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.
Technical Paper

Gasketed Joint Analysis Including Flange Bending Effects

1993-03-01
930120
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.
Technical Paper

Gasketed Bolted Joint Design Analysis Using a Spreadsheet-Finite Element Approach

1999-03-01
1999-01-0598
Gasketed bolted joint analysis tools are gaining importance as the market place demands superior product performance, reduced cycle time, and lower cost. Design analysis tools can be used to predict product performance over the life of the joint. Numerous design concepts under a range of operating conditions can be simulated. The optimal designs can be determined before a prototype is manufactured and tested. The reduction in prototyping and testing results in cost savings and a reduction in design time. The customer is provided with a product with superior sealing performance at a lower cost. This paper presents a design analysis technique which uses a non-linear finite element program in conjunction with a spreadsheet. The spreadsheet functions as a user friendly input and output interface to the finite element program. Parametric models are used to define the geometry of standard sealing system components that include gaskets, flanges, and fasteners.
Technical Paper

3D Engine Analysis and MLS Cylinder Head Gaskets Design

2002-03-04
2002-01-0663
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.
Technical Paper

New Stopper Technologies for MLS Gaskets

2002-03-04
2002-01-0665
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.
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