Stress Analysis of Bolted Flange
Bolted Flange have been in use in many industries. They are building blocks for piping design and enable transfer of fluid to a distant place. The project was a part of Finite element analysis course in which we had to undertake an individual project and complete it with high precision.
Detailed Design
Executive Summary
The bolted flanges are the components that are used in various industrial sector and pipe assemblies. They are the components in a pipe assembly that are used to connect them for elongation of the system. They are mainly used in oil industry to connect pipes for transportation. The problem with the flanges is the leakage over a certain cycle of use. This has motivated the designers of the system to focus on improving the system. The other problem with the flange is the deformation caused due to the combined effect of the bolts and nuts and the internal pressure of the fluid flowing in the All this can be designed using the FEM modelling in ANSYS. ANSYS has been a trusted software for conducting the high risk designs. The flange was modelled in a CAD software for the simplicity and further analysis was carried out using the ANSYS. The geometry was modelled In the ANSYS using different assumptions and discretization techniques to create real life model of the problem that is easy to solve. Taking the real life situation various researches are conducted in the field of flange design. For instance, the standard codes such as the ASME B16.5 has been considered to be the best flange design tool and recommends the various parameters to design. However, the designers are recommended to find the best solution themselves. The boundary conditions are applied to the model to make it mimic a real life problem. The solution of the flanges can be used in various applications such as boilers and couplers of cars. This wide spread applicability of the bolted flanges has made it one of the most applicable design research topics. The Objective of the project was to design a new type of flange with the use of a linear material. The nonlinear analysis requires an experimental data to verify the results. The results obtained have been synthesized and detailed in respect to the stress, gasket design, and the leakage proof ability of the design.
Geometry Description
The Geometry of the Flanges are simple to understand , and contain two connection faces which are bolted in with multiple bolts and gasket to prevent leakage of the fluid that is being transported. The Geometry of the Flange was designed referring to the standards set in ASME B16.5. The flange is a 16 bolt flange with a gasket in the central position between the faces. The dimensions of the flange has been shown in the diagram below :
ANSYS Geometry
The CAD model was then imported in to the ANSYS software, the simulation time for the model presented on the LEFT is significantly more compared to RIGHT. The Right figure represents 1/16th section of the bolted flange with symmetry on the two faces. In this way the complexity of meshing the model can be reduced and also the number of contacts can be reduced.
Mesh Generation Strategy
The mesh generation was carried out using Hexahedral elements , due to it having higher quality . The elements with tetra-hederal mesh had significant number of low quality mesh in the critical zones. Hence, the hexahedral mesh was used.
Study Results
The study of the total deformation and the von-mises stress was carried out on the flange . This flange was given a bolt pretension load which in addition with the pressure of the fluid caused the deformation . The maximum deformation observed was 0.05 mm. Also, the equivalent stress on the flange is 237 MPA which is well below the yield strength of the steel material it is made out of.
Contact study
The Contact study was carried out to check the leakage of fluid during the operating conditions. Gap study was performed to check the gap between the gasket and the flange contact , which is 0 mm in most of the region, which means that there is no gap for the fluid to leak. Besides, the pressure on the gasket was also analysed, we can observe that the gasket pressure is "0 Mpa" on the liquid region, which suggests that there was no damage to the gasket at that pressure.
Model Verification
Model Verification is an important step in the verification of the simulation model. For this, the mesh convergence study and element quality check was carried out. As it can be seen from the diagrams below, that the element quality is significantly better using the hexahedral mesh and the mesh convergence of the shows a pleature and not a lot of variation. Hence, the model was said to be verified and the results are satisfactory.
