Fatigue characteristics of a co-cured single lap joint subjected to cyclic tensile loads

In this paper, the effect of bond parameters on the fatigue characteristics of a steel-composite co-cured single lap joint under cyclic tensile loads was experimentally investigated. We considered the surface roughness of the steel adherend and the stacking sequence of the composite adherend as bond parameters. A fatigue failure mechanism of the co-cured single lap joint was explained systematically by investigating the surfaces of failed specimens.     

Study of single side single pass submerged arc welding using reusable backing strip

Abstract

An attempt has been made to establish a submerged arc welding procedure that will enable the production of welded butt joints in thin steel plate, having proper fusion and reinforcement geometry in a single welding run. In this work, the combined effect of the basic welding parameters, i.e. voltage, current, and speed, along with the effect of thickness, on weld penetration have been studied. Also an attempt has been made to develop a flux filled reusable backing strip. In the present investigation submerged arc welding flux in its powdered form has been used without application of any external pressure and also without any additives. Experiments have been carried out extensively on 6 mm and 8 mm thick C–Mn steel plate specimens. This form of backing strip has shown great promise towards achieving single side single run welding. The welds achieved in this single side single pass welding process are not yet 100% satisfactory, however, the results indicate the feasibility of the process to achieve quality welds to meet relevant quality standards.     

Numerical analysis of single sided spot welding process used in sheet to tube joining

Abstract

As a new kind of lightweight structure, hydroformed tubes are now widely used in vehicle bodies. The single sided spot welding (SSSW) is a variation of resistance welding used in joining hydroformed closed tubular parts and vehicle structures. During the process of SSSW, large deformation and complex contact status of the workpieces occur because there is no inside support. The time variation of the contact region and pressure distribution changes the flow paths for electric current timely and brings a fierce shunting at the position far away from the axis line, which prevents the heat concentration at the faying surface of workpieces. The characteristics of SSSW different from those of classical resistance welding mentioned above make it difficult to determine rational welding processing parameters for SSSW. In the present paper, a comprehensive structural–thermoelectric model is established. Using the incrementally coupled analysis of finite element analysis, the electrical, thermal and mechanical aspects of sheet to tube process using SSSW are investigated. The mechanical characteristic of specimens during the squeeze and welding progress, the electric current density transient distribution, the nugget formation process, and the effects of welding parameters for SSSW are discussed. It is found that ring nugget is obtained by sheet to tube SSSW. Modifying electrode force during welding cycle is a valid method to obtain acceptable nugget with shorter welding time or less energy. The calculated results of nugget size and location are in good agreement with those of experimental observations.     

Experimental study of joint performance in spot friction welding of 6111-T4 aluminium alloy

Abstract

The effect of process parameters (cycle time, tool speed and axial force) on the specimen temperature measured 2 mm away from the weld in spot friction welding (SFW) of Al 6111-T4 is investigated. The temperatures were correlated to the lap shear load. Results revealed that, to achieve a good joint strength with the maximum lap shear load >2˙5 kN, temperatures should be greater than a threshold value, which is 350°C at a location close to the SFW joint in this study. By studying the specimen macrographs, two internal weld geometric features based on the cross-section area were identified and correlated to the shear and mixed failure modes of the lap shear tested specimens. A model was developed and validated using experimental data of the cross section area of SFW joint with either shear or mixed mode fracture. The model predicts that the SFW joint strength is maximised at the transition region between the shear and mixed mode fracture.     

Database construction and data retrieval for optimal casting design

Abstract

The existing optimal casting design data retrieval system enables a user to easily retrieve only the needed text data from a huge text database. While the necessary data can be found quickly through search terms, however, it is difficult to access know how gained in the field and the shape data on casting design models. To solve this problem, an optimal system has been developed to retrieve all the shape data generated in the field. The features and keywords of comparative optimal casting designs are extracted and stored in the shape feature keyword database. Through the user interface, the two-dimensional and three-dimensional shape data and shape keywords of a product model are compared with those of casting designs stored in the database. In this way, the optimal casting design most similar to a good model is chosen.     

Experimental characterisation of a semi-solid A356 alloy during solidification and remelting

Abstract

Within the general framework of hot tearing research in casting processes the tensile behaviour of the semi-solid aluminium alloy A356 under remelting and solidification conditions is studied. In order to measure true-stress versus true-strain curves of the semi-solid metal, a new experimental technique has been developed to perform hot tensile tests in the mushy regime between the coherency and the solidus temperatures. The local true-strain in the semi-solid region of the tensile specimen is measured optically with a laser speckle extensometer (LSE). During the solidification tests measurement is done by using a transparent aero-gel mould. The resulting stress–strain curves and the corresponding microstructure are compared for the remelting and solidification condition.     

High temperature soldering of SiC particulate aluminium matrix composites (series 2000) using Zn–Al filler alloys

Abstract

The present paper evaluates the solderability of three discontinuously reinforced aluminium matrix composites. The tested composites were an aluminium alloy of the 2000 series (AA2014) reinforced with different percentages of silicon carbide particles (6, 13, and 20 vol.-% respectively). A similar study was carried out on the unreinforced aluminium alloy for comparative purposes. Three low temperature filler alloys of the Zn–Al system were used for soldering. Drop formation tests were performed to evaluate the wettability of the molten filler alloys and sample joints (single overlap specimens) were produced to determine solder penetration in the joint clearance. Microstructural studies of the joints were carried out to determine the effects of the solid reinforcement particles on molten pool behaviour and solidification mechanisms.     

Scalable Symmetry Detection for Urban Scenes

In this paper, we present a novel method for detecting partial symmetries in very large point clouds of 3D city scans. Unlike previous work, which has only been demonstrated on data sets of a few hundred megabytes maximum, our method scales to very large scenes: We map the detection problem to a nearest‐neighbour problem in a low‐dimensional feature space, and follow this with a cascade of tests for geometric clustering of potential matches. Our algorithm robustly handles noisy real‐world scanner data, obtaining a recognition performance comparable to that of state‐of‐the‐art methods. In practice, it scales linearly with scene size and achieves a high absolute throughput, processing half a terabyte of scanner data overnight on a dual socket commodity PC.     

Behaviour of Thiosulphate in Electrodialysis in the Presence of Photographic Gelatin

Electrodialysis of a 10 per cent solution of gelatin containing 30 /M of thiosulphate labelled 3,S in the outer sulphur atom was carried out with a brentzinger apparatus. Forty-five per cent of the radioactivity appeared in the anodic liquid, thirty per cent in the cathodic and the remaining twenty-five per cent in the gelatin solution. The validity of these results is discussed also in relation to other experiments carried out with ,SS labelled sulphate and :aP labelled phosphate.