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Ferritic steel weldments are invariably post-weld heat treated for relieving the residual stresses. However, the long duration of post-weld heat treatment (PWHT) required for very thick weldments can adversely affect the mechanical properties and fracture toughness. Thus, there is a need to establish the relative importance of temperature and time of PWHT with respect to stress relief. Accordingly, in the present work, the phenomenon of stress relief (due to PWHT) in an 800-mm-thick steel weldment was investigated using finite element analysis and the results were validated against experimental measurements. An analytical study was also carried out to determine the relative influence of temperature and time of PWHT on stress relief. It was found that time of PWHT plays a more significant role in case of relatively lower PWHT temperatures. It was also found that, for a given value of Hollomon parameter, different combinations of PWHT temperature and time can be employed to achieve the same level of stress relief. A mathematical relationship has been established between Hollomon parameter and magnitude of residual stress after PWHT. It has been shown that residual stress is a monotonically decreasing function of the Hollomon parameter. [ABSTRACT FROM AUTHOR]

Assuming plane strain conditions and taking phase transformations into account, finite element analysis was carried out using a bead-by-bead deposition model as well as two different lumped models. The effects of post-weld heat treatment at 600 °C were also studied. Predicted residual stresses were verified using X-ray diffraction method. While both bead-by-bead and lumped models were found to overestimate the maximum residual stress in as-welded condition, the latter facilitated a safer upper-bound estimate of the residual stress. The net tensile stress in the weld metal was found to decrease as a result of solid-state transformation of austenite to ferrite. Further, a significant part of stress relief was found to occur in the first half hour of the holding time during post-weld heat treatment. A formula was developed for estimating the maximum residual stress in post-weld heat treated condition. [ABSTRACT FROM AUTHOR]

Sealing performance of gasketed flange joints depends mainly on the behavior of gasket. In the present work, a three dimensional finite element analysis has been carried on a gasketed joint with single and twin gaskets having nonlinear material properties, to find the influence of gasket contact stress and sealing performance of the joint. Bolt preload required for safe operation of twin gasketed joints has been formulated by modifying the ASME code. A comparison is made on sealing performance of gasketed joint with single and twin gaskets. The contact pressure of twin gasketed joint is examined by varying the design parameters such as individual gasket widths and space between the gaskets. Contact pressure in single and twin gasketed flange joints at different operating conditions, viz., bolt preload and internal pressure have been investigated. It is observed that the flange joint with twin gasket can withstand higher internal pressure. [ABSTRACT FROM AUTHOR]

A novel composite barrier comprising of hydrophilic and solvent resistant chitosan (CS) membrane on porous solvent resistant poly(ether- block- amide) (PEBA-2533) substrate was synthesized for pervaporation (PV) based dehydration of the polar aprotic n -methyl-2-pyrolidone (NMP) green solvent. The composite barrier was crosslinked with tetraethyl orthosilicate (TEOS) to control swelling and enhance selectivity. Operating parameters such as feed water concentration, permeate pressure and membrane thickness were varied to assess membrane flux and selectivity. A two-dimensional finite element method (FEM) model was developed to predict the concentration profile within the membrane through computational fluid dynamics (CFD). On the basis of complete mixing experiments, a numerical simulation was performed to predict membrane area requirement and exit streams’ compositions for commercial pervaporation units operated in plug flow mode. Both unmodified chitosan and tetraethyl orthosilicate crosslinked composite membranes successfully separated feed mixture containing 4.6 wt% water by exhibiting water fluxes of 0.024 and 0.019 kg/m 2 h, whereas the corresponding selectivities were found to be as high as 182 and 225, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The dynamic response of piping system with gasketed flanged joints at various temperatures is studied using finite element analysis. FE simulation with thermo-mechanical analysis is performed, followed by modal and harmonic analysis. Important parameters affecting the vibration are discussed. Temperature of internal fluid induces thermal stresses which influence the natural frequencies significantly. A comparison has been made between metal gasket and spiral wound gasket. Results show that the natural frequencies corresponding to particular modes are influenced by the type of gasket used. [Copyright &y& Elsevier]

Abstract: The behavior of a gasketed flange joint under bending loads has been studied by three dimensional finite element analysis (FEA) and experiments. The in-plane and bending stiffness of spiral wound gaskets are considered using anisotropic Hill plasticity material model. The variation in bolt axial force of joints under bending load predicted by the finite element analysis compares well with the experimental results. The contact stress distribution obtained have significant variation in the pattern from the previous material models and consistent with the results of Bouzid regarding flange rotation. [Copyright &y& Elsevier]

The effect of end cap and PZT materials on the acoustic performance of Cymbal transducer was attempted. Generally there are three frequency bands of interest for identification of the objects in shallow and deep water environments. These are from 1 kHz to 10 kHz; 10 kHz to 100 kHz and 100 kHz to 1 MHz. Currently there is an interest in the lower frequency band and that can be addressed by using cymbal transducers. Cymbal is class V flextensional transducer, it consists of cylindrical ceramic disk sandwiched between two cymbal shaped metal caps with hollow cavities. Cymbals are used as both sound projectors and receivers. Finite Element Analysis (FEA) ATILA code was used to analyze the performance of sound projector and receiver. Three typical ceramic disks and materials used as driving elements and end caps respectively were included in this study. [ABSTRACT FROM AUTHOR]

Simulation of interface pressure and temperature distribution in a railway block brake is carried out using a coupled field (structural-thermal) finite element method. Temperature is estimated using the heat generation calculated from the interface pressure. Deceleration of the wheel is simulated by applying rotations. With the use of coupled field analysis along with the simulation of deceleration, heat generation at a point on the rubbing surface is calculated from the instant value of interface pressure at that time. Present results are verified with the experimental values for temperature rise, variation in speed, and stop time. [ABSTRACT FROM AUTHOR]

Simulation of interface pressure and temperature distribution in a railway block brake is carried out using a coupled field (structural—thermal) finite element method. Temperature is estimated using the heat generation calculated from the interface pressure. Deceleration of the wheel is simulated by applying rotations. With the use of coupled field analysis along with the simulation of deceleration, heat generation at a point on the rubbing surface is calculated from the instant value of interface pressure at that time. Present results are verified with the experimental values for temperature rise, variation in speed, and stop time. [ABSTRACT FROM AUTHOR]

Stresses in Teflon-filled spiral wound gaskets in flange joints are analysed by an axisymmetric finite-element method using micromechanical models constructed based on layer geometry. The constituents of the gasket are represented by hyperelastic and elasto-plastic material models. The inplane and bending stiffness and the non-linearity of the gasket are considered through micromechanical modelling. The micromechanical model is validated with experimental data available in the literature. An improved gasket stress distribution across the width of the gasket is obtained under different bolt preloads and internal pressures. At lower bolt preloads, only half of the gasket is effective for sealing. The results are compared with the average gasket stress model results with bolt axial force. [ABSTRACT FROM AUTHOR]

The effect of external bending on flange joints in pipelines, pressure vessels, and pressure vessel nozzles is significant and difficult to assess. In the current work, the sealing performance of a gasketed flange joint under external bending has been studied by using a three-dimensional finite element analysis, considering the non-linear material behaviour of the gaskets. Spiral wound gaskets and non-metallic gaskets with various sealing materials are considered. Results show that the allowable bending moment on a flange joint depends on the tightness required, type of gasket, and its deformation characteristics. Gaskets with elastomeric sealing materials show good performance against leakage under external bending. [ABSTRACT FROM AUTHOR]

This research is focused on developing trajectory planning tools for the automotive painting industry. The geometric complexity of automotive surfaces and the complexity of the spray patterns produced by modern paint atomizers combine to make this a challenging and interesting problem. This paper documents our efforts to develop computationally tractable analytic deposition models for electrostatic rotating bell (ESRB) atomizers, which have recently become widely used in the automotive painting industry. The models presented in this paper account for both the effects of surface curvature as well as the deposition pattern of ESRB atomizers in a computationally tractable form, enabling the development of automated trajectory generation tools. We present experimental results used to develop and validate the models, and verify the interaction between the deposition pattern, the atomizer trajectory, and the surface curvature. Limitations of the deposition model with respect to predictions of paint deposition on highly curved surfaces are discussed. Note to Practitioners-The empirical paint deposition models developed herein, which are fit to experimental data, offer a significant improvement over models that are typically used in industrial robot simulations. The improved simulation results come without the computational cost and complexity of finite element methods. The models could be incorporated, as is, into existing industrial simulation tools, provided the users are cognizant of the model limitations with respect to highly curved surfaces. Although the models are based on readily available information, incorporating the models into existing robot simulation software would likely require support from the software vendor. [ABSTRACT FROM AUTHOR]

Abstract: The present work aims to obtain failure modes and failure loads for multi-pin joints in uni-directional glass fibre/epoxy composite laminates by finite element analysis and validating the results with the experimental work. In multi-pin joints, the effect of variation in pitch-to-diameter ratio (P/D) is also important, in addition to side width-to-diameter (S/D) and edge-to-diameter (E/D) ratios. A two-dimensional finite element model is developed using ANSYS software. Tsai–Wu failure criteria associated with material property degradation is used in the analysis to predict failure load and to differentiate failure modes. The results from experimental and finite element analysis showed that it is very important to consider the affect of E/D, S/D and P/D ratios in designing multi-pin joints. [Copyright &y& Elsevier]

Abstract: Gaskets play an important role in the sealing performance of bolted flange joints, and their behaviour is complex due to nonlinear material properties combined with permanent deformation. The variation of contact stresses due to the rotation of the flange and the material properties of the gasket play important roles in achieving a leak proof joint. In this paper, a three-dimensional finite element analysis (FEA) of bolted flange joints has been carried out by taking experimentally obtained loading and unloading characteristics of the gaskets. Analysis shows that the distribution of contact stress has a more dominant effect on sealing performance than the limit on flange rotation specified by ASME. [Copyright &y& Elsevier]