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A survey has been made of the developments of welding processes and the literature concerned with the fatigue resistance of butt welded joints. Evident from the literature survey was the fact that a mass of experimental data was available on the fatigue properties of welds yet many fatigue failures were still being reported. It appears essential therefore that the design data derived from experimental results should be presented in a meaningful way to aid the safe design of welded connections. Fatigue tests were conducted on specimens cut from 1/2 in. thick plate of medium carbon steel, over a range of alternating and mean stress levels. The welds were produced using manual metal arc, gas metal arc and electron beam welding processes and manufactured in industry by accepted production methods. A non destructive examination together with static tests were carried out on both the parent material and the welded joints. The results obtained have enabled a comparison to be made between the data obtained from static, dynamic and non destructive tests. The analysis shows some evidence of correlation between the information derived from the static and non destructive tests with that of fatigue performance. A method of analysing fatigue data, based on the method of least squares, has been developed. This provides good fits to data when used in conjunction with modified versions by Goodman and Gerber of the basic Jefferson empirical fatigue equation. The fatigue curves generated by this method can be described by two equation constants which can subsequently be used to generate a family of fatigue curves over a range of mean loads. The method of analysis is also capable of calculating confidence limits on experimental data for both stress and fatigue life for the predicted fatigue curve.

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This thesis is concerned with an experimental investigation of the behaviour of lapped joints in reinforced concrete. A review of existing literature highlights the need to establish the longitudinal strain distribution along lap joints. This has been achieved experimentally, with detailed strain measurements being taken using a technique of internally gauging the reinforcing rods. In some specimens, strain concentration gauges were installed at the tip of the lap to permit the acquisition of particularly localised information. Computer programs were developed to process the substantial amounts of data generated during the course of each test. Two series of tests were undertaken, both using axially loaded specimens, and dealing with tension and compression lap joints respectively. The laps ranged in length from 125 to 750 mm, and comprised bars of either 12 or 20 mm diameter. Transverse reinforcement was provided in two of the tension specimens. Greater emphasis was placed on the first series, with fifteen tension specimens being tested. Thirteen of these tests were each completed within a single day but, additionally, two long-term tests were undertaken. In the latter, a constant load was sustained for up to 81 days. The measurements clearly showed the changing behaviour of the specimens, first as transverse cracks developed and subsequently as failure of the lap joint was approached. The comprehensive analysis of the test results includes a comparison of the ultimate behaviour of these joints with existing design proposals and regulations. The detailed information provided by the strain measurements enables the justification of design assumptions regarding lap joint behaviour, and thus lends greater confidence to existing design regulations. The results from five compression specimens were analysed and compared with the tension tests. The significant contribution to force transfer made by the bearing of the free end of the steel against the concrete was evident. The specimens were loaded to the rig capacity without failing. Additional strain measurements were taken in one tension and one compression specimen by casting embedment gauges within the concrete. These gauges were arranged to measure the circumferential strains in the specimen, and were complemented by strain gauges mounted on the surface of the concrete. The data thus obtained permitted a comparison of the bursting forces set up inside and outside the lap joints. The work showed that some aspects of lap joint behaviour require clarification. Suggestions for further work are included.

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The purpose of the study was to investigate the metallurgical interactions that occur during the brazing of zirconium with Ag-28Cu filler, with particular reference to their effect on mechanical properties. The ultimate aim was to provide information that would aid in the production of tougher brazed zirconium joints than are currently being obtained. The investigation was carried out in a number of stages: 1. A general literature survey of the metallurgy of brazed joints. 2. Zirconium brazed lap joints were made using either vacuum furnace or high frequency induction brazing. Interalloying was studied by optical and electron microscopy, X-ray diffraction and electron microprobe analysis. Interface layers were produced consisting of Cu4Zr, CuZr2, AgZr2 and Cu, distributed in a mixture between two sub-layers. Induction brazing produced high quality joints with interface layers thinner than those in vacuum brazed joints; a link between heat-up rate and wetting was observed. 3. Butt joints for mechanical testing were produced to optimum conditions. Instrumented impact testing showed that the toughest joints were those brazed with a reactive copper filler, although in all joints most of the energy absorbed was due to fracture initiation energy. 4. The greater toughness of the reactive copper brazed joints was due to a lack of flaws of any kind in their microstructure, which consisted of a eutectic of CuZr and CuZr2. In contrast, interface layer Ag-28Cu brazed joints contained shrinkage cracks and interfacial voids, along which fracture occurred.

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