A variety of tool shoulder designs comprising three families i.e. blade, spiral and circular shaped scrolls, were produced to improve the material flow and restrictions to avoid the tunnel void. The bobbin tools were manufactured by 3D printing additive manufacturing technology using solid filament. The butt weld joint was produced by each tool using plasticine as the workpiece material. The apparent surface features and bi-colour cross-sections provided a physical flow comparison among the shoulder designs. For the bobbin friction stir welding (BFSW), the tool shoulder with a three-spiral design produced the most stability with the best combination of the flow patterns on surface and cross-sections. The circular family tools showed a suitable intermixing on the surface pattern, while the blade scrolls showed better flow features within the cross-sections. The flow-driven effect of the shoulder features of the bobbin-tool design (inscribed grooves) was replicated by the 3D-printed tools and the analogue modelling of the weld samples. Similar flow patterns were achieved by dissimilar aluminium-copper weld, validating the accuracy of the analogue plasticine for the flow visualization of the bobbin friction stir welding.
Many automobile industries prefer hybrid joining practices in the part-assembly of advanced lightweight automobile and commercial vehicles. The main cause for this is the greater need for mixed material design. One of the combinations is composite with aluminium, like a combination of Titanium-Aluminium, CFRPs with aluminium etc. This paper deals with comparative study of mechanical strength evaluation in riveted joints, adhesive joints and hybrid single-lap joints. Hybrid joints are a combination of riveted and adhesive joints. The riveted joint produces enormous stress around the holes of the fasteners, which is detrimental to its performance. The adhesive joint allows good load distribution; however, it leads to plastic deformation that is detrimental in the long run. The hybrid joint has better load bearing capacity when compared to the riveted or adhesive joints. Thus, the study indicates that a hybrid joint has better properties suitable for structural, automobile and aerospace applications.
Unsaturated polyester (UP) toughened epoxy blend system is developed. A nanocomposite based on an epoxy/polyester blend matrix reinforced by exfoliated montmorillonite clay has been processed to prepare nanocomposite specimens in different weight ratios viz. 0%, 1%, 2%, 3%, 4% and 5% for thermal and damping properties studies. The specimen are developed and studied as per American Society for Testing and Materials (ASTM) standards. Among all the weight ratios, 5% clay filled nanocomposite exhibited better thermal properties. Similarly, 4% clay filled nanocomposite exhibited better damping properties. The experimentation is further undergone to factorial analysis to extract the absolute optimal values of % clay-filled blend nanocomposite. The objective of this study is to identify a suitable nanocomposite which offers low-cost, high strength material; which can be applied for engineering and structural applications to provide better performance. Keywords: Thermal property, damping property, Epoxy, Unsaturated Polyester, Clay I. INTRODUCTION Plastics are extremely sensitive to changes in temperature. Molecular orientation has a significant effect on thermal properties. The molecular weight of polymers affects low temperature flexibility and low temperature brittleness. Many other factors such as intermolecular bonding, cross-linking, and co-polymerization have considerable effect on thermal properties. At low temperatures, plastics tend to become rigid and brittle. This happens mainly because at low temperatures the mobility of polymer chain is greatly reduced. The study of the response of a material to heat is very important. When a solid absorbs heat energy, its temperature, and its dimensions increase. The heat energy absorbed by the solid may be transported to cooler regions if temperature gradient exists. Further heating of the solid causes it to melt. Therefore, the study of thermal properties of materials is essential to evaluate the thermal behaviour of polymers and their response to thermal changes [1][2][3]. The study of thermal behaviour of the polymers is also important for making component parts of automobiles etc. that have to withstand high as well as fluctuating temperatures. Materials that are used in various engineering structures like aircrafts, spacecrafts, automobiles, building structures etc. are required to possess certain special vibration-damping properties for best performance. The requirements are different for different applications. Some materials have good ability to dissipate elastic strain energy when subjected to vibratory loads and are widely used in the fields of high performance structural applications such as aerospace, marine, construction, etc. Damping is an important modal parameter for the design of structures for which vibration control and cyclic loading are critical. Damping is also a significant factor for the fatigue life and impact resistance of structures. All engineering materials dissipate energy under cyclic load. Some of them such as elastomeric, plasti...
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