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Sequence diagrams can be valuable aids to software understanding. However, they can be extremely large and hard to understand in spite of using modern tool support. Consequently, providing the right set of tool features is important if the tools are to help rather than hinder the user. This paper surveys research and commercial sequence diagram tools to determine the features they provide to support program understanding. Although there has been significant effort in developing these tools, many of them have not been evaluated using human subjects. To begin to address this gap, a preliminary study was performed with a specially designed sequence diagram tool that implements the features found during the survey. On the basis of an analysis of the study results, we discuss the features that were found to be useful and relate these to the tasks performed. It concludes by proposing how future tools can be improved to better support the exploration of large sequence diagrams. Copyright © 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.

The tool is a key component in the friction stir welding (FSW) process, but the tool degrades and changes shape during use, however, only a limited number of experimental studies have been undertaken in order to understand the effect that worn tool geometry has on the material flow and resultant weld quality. In this study, a validated model of the FSW process is generated using the CFD software FLUENT, with this model then being used to assess the detail of the differences in the flow behaviour, mechanically affected zone (MAZ) size and strain rate distribution around the tool for both unworn and worn tool geometries. Comparisons are made at two different tool rotational speeds using a single weld traverse speed. The study shows that there are significant differences in the flow behaviour around and under the tool when the tool is worn. This modelling approach can therefore be used to improve understanding of the effective limits of tool life for welding, with a specific outcome of being able to predict and interpret the behaviour when using specific weld parameters and component geometry without the need for experimental trials.

The commercial materials forming package DEFORM-2D is used to model the inertia friction welding (IFW) process with particular reference to aero-engine mainline drive shafts. Both representative and predictive modelling techniques are presented, and models are described for the welding of identical and dissimilar material/geometry combinations. The range of material properties required for the models are discussed and details of the tests carried out to produce suitable material data are included. Case studies involving Inconel 718 and AerMet 100 are presented. The phase transformations in a high-strength aerospace steel are included in the model and their effects on residual stresses are presented. Temperature profiles are compared with experimental thermocouple measurements and the models are also compared with upset and rotational velocity data collected during welding. The DEFORM-2D software in conjunction with a friction law coded into a subroutine are shown to be suitable for modelling the IFW process between similar and dissimilar shaft materials. Results highlight the importance of the inclusion of the volume change associated with the martensite transformation on the residual stresses generated during the post-weld cooling of IFW joints.

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