Masahide Katsuo

A two-dimensional finite element thermal stress analysis of adhesive butt j oints containing some hole defects

Thermal stress distributions in adhesive butt joints containing some hole defects under uniform temperature changes were analyzed using a two-dimensional finite element method (FEM). Four kinds of adhesive butt joints which contained no hole, 3-hole, 8-hole, and 16-hole defects in the adhesive layer were studied. In particular, the stress concentrations around the hole defects and near the edges of the interface between the adherends and the adhesive were examined. From the results, the thermal stresses around the hole defects located near the center of the adhesive were found to be larger than those around the hole defects located near the free surface of the adhesive. The thermal stress near the edges of the interface decreased with an increase in the number of holes and a decrease in Youngs modulus of the adhesive. For verification, photoelastic experiments were carried out and fairly good agreement was seen between the numerical and the experimental results.

Two-dimensional thermal stress analysis in adhesive butt joints containing hole defects and rigid fillers in adhesive under non-uniform temperature field

This study is concerned with the thermal stress analysis of an adhesive butt joint which contains circular holes and rigid fillers in an adhesive and is under a non-uniform temperature field. In the analysis, the adherends are assumed to be rigid and the adhesive is replaced with a finite strip having holes and rigid fillers in it and the thermal stress distribution in the adhesive is analyzed using a two-dimensional theory of elasticity. The effects of size and location of the circular holes and rigid fillers on the stress distributions at the interface and at the hole and filler peripheries are clarified by numerical calculations. For verification, photoelastic experiments were performed using an epoxide resin plate with small holes and fillers in it, to model and adhesive in the joint. The analytical results are fairly consistent with the experimental ones.

Two-dimensional transient thermal stress analysis of adhesive butt joints

Transient thermal stress distribution in an adhesive butt joint is considered. It is assumed that both the upper and lower end surfaces of the joint are maintained at different temperatures at a certain instant in time and that no heat transfers between the side surfaces of the joint and ambient air. In the analysis, two adherends were replaced with finite strips and unsteady temperature distribution in the joint was obtained theoretically. Then the transient thermal stress distribution in the joint was analyzed using a two-dimensional theory of elasticity. The effects of the ratios of the coefficient of thermal expansion and Youngs modulus of the adherend to those of the adhesive on the thermal stress distribution were clarified from numerical calculations. Furthermore, the transient stress distribution in the adhesive was measured by a photoelastic experiment on a joint where the adhesive was modelled by an epoxy plate. The experimental results were consistent with the analytical results.

FEM Stress Analysis and Sealing Performance in Pipe Flange Connections With Adhesive Subjected to Internal Pressure and External Bending Moments

This study deals with the stress analysis and the estimation of sealing performance of the pipe flange connections with an adhesive under an internal pressure and an external bending moment are analyzed by using the 3-dimensional elastic finite element method (FEM). The experiment of the leakage test of the connections with an adhesive was carried out by applying the above loads to the connections. From the FEM analysis, the following results were obtained; (1) when an internal pressure is applied to the flange connections, the compressive stress at the interface between a flange and an adhesive increases proportionally from the inner side of the interface to outside, and (2) when an internal pressure and a bending moment apply to the flange connections, the stress distribution at the half part of the interface increases as the external bending moments increase and also Young’s modulus of the adhesive increases. From the experiments, the following results were obtained: (1) sealing performance of the pipe flange connections with an adhesive under an internal pressure and an external bending moment increases as the flange thickness and an initial clamping force of bolts increases and (2) the sealing performances were not found between the connections with an adhesive and that with a gasket combining an adhesive. Furthermore, the numerical results are in fairly good agreement with the experimental results.Copyright

Finite Element Stress Analysis and Evaluation of the Sealing Performance in Pipe Fittings With Adhesive for Threaded Connections Under Internal Pressure and Bending Moment

In practice, PTFE tape is being used for sealing of a pipe fitting. However, the efficiency, the decrease in work time, and the sealing performance can be improved by using adhesive instead of the tape. When such a pipe fitting is under an internal pressure and external bending moment by an internal fluid and others, however, an influence in the sealing performance is taken by how to use an adhesion. This study deals with the stress analysis and the evaluation of the sealing performance of the pipe fitting with an adhesive under an internal pressure and an external bending moment analyzed by using the 3-dimensional elastic finite element method. Furthermore, the experiment of the leakage test of the pipe fitting with an adhesive was carried out when the above loads were applied to the pipe fitting. From 3-D FEM analysis, the following results were obtained: (1) the stress distribution at the interface between thread and adhesive on the side of the internal pressure is tensile stress, and stress on the opposite side is compressive, (2) the stresses at the area of the clearance between the valley of the screw and the mountain increase as the numbers of turns of the thread in fittings increase, and (3) the compressive stress at the side of the tensile part in the fittings decrease as the external bending moments increase. However, the sealing performance will not change when the bending moment is not so great because the compressive stress at the side of the compressive part in the fitting increases. From the leakage tests, the following results of the sealing performance were obtained: (1) the sealing performance of a fittings with adhesive under an internal pressure and a bending moment didn’t decrease when bending moment was not so great, and (2) when it exceeds fixed pressure, rapid leakage from the fitting with adhesive occurred by the exfoliation of the adhesive. Furthermore, the numerical results are in fairly good agreement with the experimental results.© 2005 ASME

Finite Element Stress Analysis and Estimation of the Sealing Performance in Pipe Fittings With PTFE Tape for Threaded Connections Under Internal Pressure

The interface stress distributions between the unsintered PTFE (Polytetrafluoroethlene) tape and threads of the fittings under an internal pressure are analyzed by using the finite element method (FEM). From the numerical calculations, the following results were obtained: (1) the stress distributes uniformly at the interface except near the edges, (2) the stress becomes singular at the edges of the interfaces and (3) the stress increases as the Young’s modulus of the PTFE tape thickness increases. The experiment of the leakage test of the connections consist of the socket and the plug manufactured of cast iron or stainless steel, which was also carried out by applying an internal oil pressure to the threaded connections. From the experiments, the following results are obtained: (1) the sealing performance in pipe fittings with PTFE tape increased as the number of turns in the PTFE tape increased, and it was not proportional to the numbers of turns, and (2) also as the number of turns in the screw plug increased, and it became a quadratic form, (3) the flow rate of leakage oil from the fittings under the internal pressure decreased as the number of turns in the screw plug increased, and (4) it could be estimated by using the Darcy-Weisbach and the Hagen-Poiseuille equations in the laminar-flow.Copyright

Axisymmetrical FEM Analysis and Estimation of the Sealing Performance in Pipe Flange Connections Combining Metallic Gasket With Adhesive Subjected to Internal Pressure and Temperature Change

This study deals with the stress analysis and the estimation of the sealing performance of the pipe flange connections combining a metallic gasket with an adhesive subjected to an internal pressure and a temperature change. Stress distributions at the interface between the adherends and the adhesive in the connections are analyzed by using the finite element method (FEM). From the numerical calculations, the following results are obtained: (1) the stress distributes uniformly at the interface except near the edges, (2) the stress increases as Young’s modulus of an adhesive decreases, (3) the stress becomes singular at the edges of the interfaces. In the experiments, the pipe flange connections consisting of dissimilar circular gaskets with an adhesive were manufactured, and the leakage tests of the connections were carried out by applying an internal pressure and a temperature change to the connections. From the experimental results, the following results were obtained: (1) the sealing performance increased as the width of a gasket decreased and the initial clamping stress increased, and (2) the sealing performance of the pipe flange connections subjected to a temperature change increased under a moderately high temperature.Copyright

Two-Dimensional Thermal Stress Analysis in Butt Adhesive Joints Containing Hole Deffects and Rigid Fillers in Adhesive.

This study is concerned with the thermal stress analysis of a butt adhesive joint which contains circular holes and fillers in the adhesive and is under non uniform temperature held. In the analysis, the adherends and fillers are assumed to be rigid and the adhesive is replaced with a finite strip containing holes and rigid fillers and the thermal stress distribution in the adhesive is analyzed using a two-dimensional theory of elasticity. The effects of size and location of circular holes and rigid fillers on the stress distributions at the interface and at the filler and hole peripheries are clarified by numerical calculations. For verification, photoelastic experiments were performed using an epoxide resin plate containing small holes and fillers, to model an adhesive in the joint. The analytical results were fairly consistent with the experimental ones.

Delamination Growth and Thermal Stress Analysis of Adhesive Butt Joints by Finite Element Method

In electric devices, generally electric components are bonded to substrates and their material and thermal properties are usually quite different each other. Thermal stress is generated in an electric device under its temperature changes and it often becomes significantly large at the edges of the interface between a bonding layer and an electric component or a substrate. Consequently, electric devices are suffered from the damages such as delamination of which growth will lead to catastrophic breakage of bonding even if no external loads applied to them and sometimes their own electric function and reliability will be lost. Moreover, if there are some imperfections in the bonding layer such as hole defects or fillers, the thermal stress concentrates around the hole defects or the fillers and also these existence affect on the thermal stress distribution at the interface. However, up to now, there are few investigations which examine the effects of the defects on the thermal stress distributions in the bonding layer[1]–[2].

Transient Thermal Stress Analysis of Butt Adhesive Joints Subjected to Heat Radiation at Side Surfaces of the Adhesive

Electronic devices are composed of different kinds of small components and substrates and recently produced in lay-up structure in order to achieve ultimate scale of integration. These electric components and substrates of which material properties such as coefficient of thermal expansion, thermal conductivity, Young’s Modulus and so on are generally quite different each other, are joined by soldering or adhesively bonding. These mismatches cause the thermal stress in the device when it is subjected to any temperature distribution during manufacturing and operation processes and the thermal stress may cause a failure or a fracture of the device even if the device is free from any mechanical loading. Some analytical investigations have been done on the thermal stress in an electronic device using a finite element method and a theory of elasticity[1][2]. However most of them are concerned with the device in steady state temperature conditions. Estimating the thermal strength of such electronic device in unsteady state is also necessary for practical use of it. In this study, a procedure of transient thermal stress analysis of a butt adhesive joint modeled as a simple electric device is presented. Followings are assumed as the thermal conditions of the joint, i.e., adherends modeled as an electric component and a substrate are bonded together by an adhesive at certain constant temperature then the adherends are maintained at 0°C at some instance and heat radiates at side surfaces of an adhesive into an ambient air of 0°C. In the analysis, the adhesive is replaced with the finite strip and the transient thermal stress distribution is analyzed using a two-dimensional theory of elasticity.