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Part 1: 3D-Finite Modeling of Bolted Flanged Joints and Development of a Transducer for Measuring Gasket Contact Stress: 3D Finite Element Modeling of Bolted Flanged Joints Subjected to External Bending Loads

In real life, bolted flanged joints can be subjected to external loads from many different sources including thermal expansion of piping and piping components, misalignments of pipe supports, and non-symmetrical thermal expansion of the joint components. In most of these cases bending moments are induced in the pipes and are transmitted to the flanges. For the design of bolted flanged joints, the effect of these moments must be accounted for as it can affect their mechanical and tightness behaviors. The use of the finite element technique for the analysis of bolted flanges subjected to non-symmetrical loadings is powerful and economical. This is particularly true for large dimension flanges for which experimental testing is very expensive and difficult to achieve. An attempt has been made in 1996 at TTRL [1] to develop a finite element model with non-axisymmetric loading using Fourier expansion to transform the three dimensional loading into a two dimensional one. The results obtained with this model were not satisfactory because the non-linearity of the bolted joint behavior was not accounted for. For non-symmetrical loading, the use of a three dimensional modeling of the joint components is certainly more appropriate to study the effect of external bending moments. In fact a three dimensional model has a great potential since it allows a more realistic behavior of the structure when compared to two dimensional model, particularly if the flange holes and the bolts need to be modeled. In addition, a three dimensional approach is essential to obtain a realistic circumferential and radial distribution of the gasket contact stress which is the key parameter that controls leakage [2]. The purpose of this research is therefore to develop a three dimensional finite element model (3D FEM) to evaluate the effect of bending loads on the mechanical and tightness integrity of bolted flanged connections, and to compare the numerical results obtained with the 3D FEM to existing experimental data obtained from bolted joints that were tested for previous PVRC projects [3, 4, 9].

Part 2: 3D-Finite Modeling of Bolted Flanged Joints and Development of a Transducer for Measuring Gasket Contact Stress: Development of a Transducers for Measuring Gasket Contact Stress in Bolted Flanged Joints

The gasket stress distribution generated by flange rotation has a major impact on the leakage behavior of a bolted flanged joint, however there is currently no reliable experimental technique to directly measure the gasket contact stress in a bolted, flanged joint. Several PVRC finite element models have been generated to predict the gasket stress distribution [7, 8,9] in bolted, flanged connections. However, the validation of these FE models is based on the measurement of indirect parameters such as the flange rotation and the residual bolt loads. In this project, a special transducer, located in the flange beneath the gasket, to measure the radial variation of the contact stress developed in a bolted flanged connection has been developed and evaluated. The experimental results obtained with this transducer will be compared to the available numerical contact stress distributions obtained with the 3D-finite element model developed in PVRC project 98-04.

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Published: 2006 Number of Pages: 96 File Size: 1 file , 4.4 MB