BEASY Technical Papers and Publications

The present work summarises a numerical procedure aimed to the residual strength assessment of a cracked butt-joint, based on R-curve analysis and plastic collapse prediction. In a linear elastic fracture analysis, the Stress Intensity Factors evaluation is based on the use of the Dual Boundary Element Method, as implemented in the BEASY code. A two-dimensional approximation (plane stress) of the joint is also validated by a three-dimensional numerical analysis, which allows to take into account the secondary bending effect and to assess its relevance. Experimental joint collapse load was available for comparison with numerical results, in order to validate the procedure.

A comprehensive study of the structural integrity of a precast concrete tunnel was conducted following the discovery of cracking, during construction, in some sections of the tunnel liner. The structural behavior of the jointed tunnel ring was investigated through experimental testing and computer simulation. Data gathered from field performance monitoring and full-scale laboratory testing was used in conjunction with numerical simulation to investigate the effect of stress concentrations at bolt pocket recesses and excessive rotation at jointed connections.

(491KB) Mechanical and thermal crack initiation along the seal edge of cathode ray tube
C.Y. Cha, V. Lakshmanan, H. Betrabet, C.A. Brebbia, R. Adey

This article describes a thermal stress boundary element analysis which was carried out to select a mechanical device that would innovate the frit salvage of cathode ray tubes (CRT). The panel and funnel of a CRT are fritted at the seal edge. To reuse a CRT the panel and funnel are separated by etching and then applied a thermal shock. This procedure is known as frit salvage. Current yield of the frit salvage success rate is about 61% which means that 39% of the components are lost and cannot be reused.

In a stress analysis of a cathode ray tube (CRT), it is important to consider the performance of the design under two loading conditions; the vacuum loading and the load applied by a pretensioned metal band around the tube. The stress analysis may be done using either the Finite Element Method (FEM) or the Boundary Element Method (BEM). With both techniques it is important to examine the convergence properties of the solution when the mathematical model is improved This gives a better idea of the true solution as well as giving information about the required mesh density for future models.

Design of pressure vessels is covered by references such as the ASME Pressure Vessel Code and textbooks devoted to pressure vessel design. Detailed stress analysis, particularly in the area of discontinuities, is generally left to the design engineer. The type discontinuity addressed in this paper is the design of bolted flanges for a pressure vessel. Work for this project involves optimization of the hub contour using the ASMEZ Pressure Vessel Code requirements as constraints. This paper summarises the initial work, development of the BEM (BEASY) models and verificafion of the model to classical techniques such as a “Roarkl’ 123.

This paper discusses application of the boundary element method (BEM) to preliminary stress analysis of a failed drive sprocket from a laboratory dynamometer. Initial inspections indicate the failure may have initiated in a slot key groove in the hub of the sprocket. The boundary element method, using BEASY, has been used to perform an initial, two-dimensional stress of the sprocket to evaluate the overall affect of the stress concentrations of the key slot.

2.2 Contact Analysis

Contact geometry has a strong influence on the load capacity and life of transmission elements, such as spline couplings, that rely on power transfer via contacting conformal surfaces. This paper describes a new numerical tool that automatically generates the necessary contact geometry for the required distribution of contact stress and load transfer. As an example, the method is applied to a spline coupling for which experimental measurements are available.

This paper describes the application of the boundary element code BEASY as an analysis tool to investigate the acute variations in stress and displacement that occur at the edges of contacting surfaces. These "edge of contact" effects can be significant when frictional forces are present and play an important role when evaluating the susceptibility of a component to fretting fatigue damage. This point is substantiated by reports [1] from the U.S. Air Force (USAF) describing several disk post failures attributed to high stress gradients arising at the edge of contact between the blade and disk.

This work concerns a study on steel polygonal couplings, with trochoidal 3-lobe profile, and is aimed to highlight the contact stress and strain state of shaft-hub interface, with reference to particular profile geometric parameters. From Mechnik’s and Kollmann’s works, in which the analysis was performed by the Finite Element Method, this work develops a CAD/CAE methodology for coupling design, oriented to an efficient integration between CAD systems and Boundary Element solvers.

In 1996 a project was established under the BGA Gear Research Foundation initiative with support from the DTI to develop new design and modelling technology for spline transmission joints. Improved shaft spline design methods were required to meet the needs of new civil aero engine designs that would have higher by-pass ratios and reduced core sizes. Such designs require smaller diameter shaft splined couplings that are capable of transmitting greater torque. Significant improvements in torque capacity may be required by future designs and will be realised by combined improvements in material strength and analysis techniques.

The implementation of a contact algorithm in a general purpose boundary element system is described. The paper describes the approach adopted in BEASY and applications of the system to general contact problems.

2.3 Dynamic Analysis

The boundary element method (BEM) has became established as a powerful alternative to finite element modeling for a variety of automotive engineering solutions. In particular, it has been effective in the static analysis of powertrain components and also for the acoustic analysis of both the passenger compartment and the air-spare surrounding a vehicle. While the technique offers a substantial improvement in ease of use and modeling times for many problems, especially those described above, and also produces highly accurate solutions, the only drawback of the BEM has been its some-what more limited range of analysis types. This paper describes how the Dual Reciprocity BEM technique has been applied in a commercial BEM package to offer a solution for dynamic analysis.

It is over twelve years since the dual reciprocity method (DRM) was first proposed by Nardini and Brebbia, [1]. Many authors have proposed extensions to the technique and it has been applied to dynamic problems, transient problems and others to transform equations to the boundary where the fundamental solution is now known. The technique provides a very general methodology for obtaining a boundary element solution to a wide range of problems [2].

BEASY Technical Papers

BEASY Publications
Technical Papers Index

2.0 Mechanical Design

2.1 Stress Analysis

2.2 Contact Analysis

2.3 Dynamic Analysis