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Welding is one of the most important metal joining techniques due to its advantages in relation to speed and versatility. One of the unwanted effects of gas metal arc welding is residual stress, that arises due to the inherent temperature loadings and can lead to structural integrity or assembly problems. Experimental investigation of these effects is highly desirable but often costly, especially in large-scale construction such as shipbuilding. It is therefore of interest to exploit the potential of computational analysis techniques, such as finite element analysis, for the assessment of these effects. The use of finite element analysis in this context is however not straightforward, due to the complex nature of the problem. The work presented here deals with an experimentally validated modelling strategy applied to two weld joint configurations: butt and fillet welded plates. Simulation techniques are presented which are aimed at predicting residual stresses. These are validated against measurements carried out using the hole drilling method for residual stress determination. Results show a good qualitative and quantitative match in simulated and experimentally measured values, which back up the modelling techniques adopted.

Multiply-stiffened, thin plate, welded fabrications are used in a wide variety of transport fields, however the resulting out-of-plane distortion associated with welding exacts a severe design penalty. Depending on the information required, the size of the structure under investigation and the computer power at hand, three computational strategies may be considered to predict welding distortion. If prediction of the localized residual stresses from welding is of major importance, then a full transient, uncoupled thermo-elastoplastic analysis is preferred. This method is not readily applicable to predict welding distortions in industrial-scale welded structures. More computationally efficient models are required and two other models are suggested in the current study. A series of experimental tests of a realistic nature were performed to validate the proposed computational strategies. Computational and experimental study of butt and fillet welding of small and industrial size fabrications is considered.

A new approach to the assessment and optimization of geometric stress-concentrating features is proposed on the basis of the correspondence between sharp crack or corner stressfield intensity factors and conventional elastic stress concentration factors (SCFs) for radiused transitions. This approach complements the application of finite element analysis (FEA) and the use of standard SCF data from the literature. The method makes it possible to develop closed-form solutions for SCFs in cases where corresponding solutions for the sharp crack geometries exist. This is helpful in the context of design optimization. The analytical basis of the correspondence is shown, together with the limits on applicability where stress-free boundaries near the stress concentrating feature are present or adjacent features interact. Examples are given which compare parametric results derived from FEA with closed-form solutions based on the proposed method. New information is given on the stress state at a 90° corner or width step, where the magnitude of the stress field intensity is related to that of the corresponding crack geometry. This correspondence enables the user to extend further the application of crack-tip stress-field intensity information to square-cornered steps, external U-grooves, and internal cut-outs.

The main aim of the development described in this paper is to establish a practice whereby undergraduate engineering students exercise their growing technical knowledge and analytical capability in the context of real engineering problems. This is done by setting ‘technical investigations’, which are based on actual industrial or consulting problems. In the present case, these case studies are set within a relatively conventional, ‘engineering science’ course on the theme of structural integrity, but the principle and the benefits to learning would be equally valid if applied to other engineering themes. The background needs which have prompted the introduction of this element and the strategies used to integrate and assess such work in a conventional lecture course are discussed and concrete examples of suitable case studies are given. Technical investigations have now been developing over three academic sessions in the author's department and information from feedback questionnaires in the first and most recent periods is included. The conclusion is that the integration of such exercises has several benefits, in terms of mastery of the subject area and in relation to the development of professional skills.

Modern lightweight stab-resistant body armour has been developed in response to the operational requirements and the experiences of police forces. While a high degree of protection may be afforded to the wearer, this has usually been achieved at the expense of weight, stiffness, and comfort. The use of a test method to measure the protection level of a proposed design against a target specification is inherent in the design and development process. This study reviews data used to establish recent improvements in standard test methods, and shows that deficiencies in current standards may well lead to over-specification of body armour. It is shown that more detailed characterization of real human stabbing actions is needed and the test situation needs to be viewed as a multibody, dynamic interaction if results are to be obtained that reflect the reality of an attack. The information will be of particular interest to body armour manufacturers and researchers working to improve armour design.

The aim of the research described was to establish a sound structural analysis procedure for load-carrying fillet-welded attachments with particular reference to cases where the welds are well separated by crack-like discontinuities. Finite element analysis (FEA) was used to determine linear elastic fracture mechanics stress intensities and limit states for a range of typical attachment geometries, on the assumption that these two failure conditions represent practical extremes of behaviour. The influence of differences between the yield strengths of the parent materials and the welds was explored in the theoretical study. The results of the FEA were analysed to obtain the development of appropriate design/assessment formulae, based on simple structural mechanics models. These formulae provide an approach that improves on current codes of practice, which treat the loads on welds as statically determinate and ignore crack-related failure potential. Collapse tests were carried out on two-dimensional models of the cases studied. These included specimens where the strength properties were uniform throughout and others where higher-yield-strength welds were incorporated. The results confirmed the FEA results and associated formula with respect to the limit state and provided some insight into the effects of heterogeneous strength properties in the junction.

The analytical equations given for stress concentration factors are based on the results of finite element analysis of stepped plates subject to uniaxial tension loading. The fillet radii at the stepped transitions were varied over a wide range, leading to elastic stress concentration factors between 1.1 and 8.3 (net stress basis).The parametric equations depend on the previously described concept of a ‘notch configuration factor’. This is similar to the crack configuration factor or compliance function used to modify the basic crack tip stress intensity solutions in the case of finite width or other problems.In the present case of the stepped plate, an energy approach was used to relate the sharp corner stress field to the corresponding sharp crack field, leading to a ‘sharp corner configuration factor’. This factor was then applied to the equation for the stress concentration factor at an elliptical hole in an infinite plate, to give a simple analytical expression for the stepped plate with a radiused fillet. The basic expression was refined further to improve the quality of fit, to an accuracy of 2 per cent with respect to the finite element models.

The closed-form equations given are based on the results of finite element analyses of double-edge-notched plates subject to tension or in-plane bending. The notch dimensions were varied in a parametric survey from shallow, part-circular forms to deep, sharp, slits with semi-circular ends, giving stress concentration factors varying from 1.2 to 13 (net stress basis). The concept of a configuration factor for notches, similar to that used to calculate crack-tip stress field intensity factors, is introduced. It is shown in the first instance that the analogous crack configuration factor can be used directly to modify the elastic stress concentration factor for an elliptical hole, giving closed-form functions that do not involve empirical fitting constants and have acceptable practical accuracy. Reasons for the effectiveness of this form are given, together with an analysis of the points where the notch stress concentration factors diverge from the simple closed form. Further refinements that improve accuracy are given and comparisons are also made with stress concentration factors for hyperbolic edge notches.