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Polymer Processing
Published in Anil Kumar, Rakesh K. Gupta, Fundamentals of Polymer Engineering, 2018
The results of White and Dee also revealed that, if fluid injection was rapid, a jet emerged from the gate, struck the mold wall at the far end, and piled up upon itself, as shown in Figure 15.23 [36]. Later, a front entered the gate and filled the mold. The advancing front, however, could not entirely absorb the piled-up material within itself, and the solidified molding showed evidence of jetting in the form of weld lines. Note that, whenever flow splits around an insert in the mold, the two fronts meet later, and the place where they meet shows up as a weld line. A weld line usually represents a region of weakness and is undesirable. One way to eliminate jetting is to place an obstruction directly in front of the gate or to mold against a wall. Oda et al. have found that if the die swell were large enough, the jet thickness would equal the mold thickness and the polymer would contact the mold walls; the mold walls would then act as a barrier, and jetting would not occur [36].
Arc Heat Model
Published in G. Ravichandran, Finite Element Analysis of Weld Thermal Cycles Using ANSYS, 2020
The in-plane analysis is performed by considering a two-dimensional plane at the mid-section of the plate. The arc moves along the length of the plate from one end to another end as shown in Figure 5.17. At the start point, the arc is just touching one edge of the plate as shown in the figure. The arc moves to a newer location along the weld line as shown in Figure 5.18 for different time intervals. Finally the welding phase comes to an end when the arc just touches the other end of the plate as shown in Figure 5.19. During the welding phase, the arc heat is experienced by some points along the weld line. During the subsequent cooling phase, the arc heat is totally absent.
Computations and Sustainability in Material Forming
Published in R. Ganesh Narayanan, Jay S. Gunasekera, Sustainable Material Forming and Joining, 2019
Zhengjie Jia, R. Ganesh Narayanan
Some representative predictions like the stress–strain behavior, draw-in profile, weld line movement, and draw depth during cup deep drawing, are presented as below. The tools required for tensile test, deep drawing test simulations, and neural network modeling details can be obtained from the earlier work (Veera Babu et al., 2009, Veera Babu et al., 2010, Dhumal et al., 2012, Dey et al., 2012). The comparison between expert system predictions (true stress–strain behavior) and simulation results are shown in Figure 8.18. The strain-hardening exponent (n) and strength coefficient (K) values obtained from neural network predictions are incorporated in the power law (hardening law), σ = K εn, for TWBs made of steel and aluminum alloy base materials for true stress–strain curve prediction. In Figure 8.19, the draw-in profiles during deep drawing are predicted for two different material combinations. Both the tensile behavior and deep drawing behavior are predicted with acceptable accuracy. In Dhumal et al.’s work, the drawn depth and weld line movement are predicted. Weld line movement is commonly observed during the forming of TWBs—the weld zone moves during stamping. The imbalance in the drawing resistance of the base sheets constituting TWBs leads to different levels of deformation or draw depths, but maintaining continuity, resulting in movement of the weld zone. In other words, the weld line movement is due to the heterogeneity in plastic deformation achieved in the two base metals during forming. The weld line movement is unwanted as it reduces formability. Sometimes tool design needs major modification incurring extra cost. Therefore, it is essential to predict the weld line movement during forming of TWBs and the expert system predictions are encouraging.
Effect of process parameters on the joint strength in ultrasonic welding of Cu and Ni foils
Published in Materials and Manufacturing Processes, 2019
Muhammad Bilal Shahid, Seung-Chang Han, Tea-Sung Jun, Dong-Sam Park
In recent years, Battery Electric Vehicles (BEV’s) have received a great deal of attention from industries owing to fossil fuel and climate-change concerns.[1–3] For the proper functioning of these BEV’s, lithium-ion batteries which have their performances up to par[4] are needed. To manufacture them, sound welding techniques are required to meet stringent joining requirements since lithium-ion batteries have different pack configurations that demand robust mechanical joining for reliable functioning.[5,6] The pack configurations involve the joining of multiple, dissimilar and highly conductive metal layers and hence it is rather challenging to perform joining using conventional welding processes. A suitable welding technique is, therefore, required to fulfill the joining requirements. Ultrasonic Welding (USW) has been considered a very promising technique for joining the highly conductive multiple layers of metals, as it is a solid state welding technique and thus there will be no melting at the weld interface.[7] Weld specimen during USW are clamped under high pressure between vibrating horn and anvil, resulting in the development of high strain rates and temperatures at the weld interface. As the weld energy is increased, the weld interface changes from planar to wavy nature and different kinds of features like vortices, swirls, and porosity occur close to the weld line.[8] Some voids have also been observed close to the weld line during welding of thermoplastics which were vanished at higher amplitudes and resulted in good strength welds.[9] Ultrasonic welding is a coupled thermal-mechanical phenomenon since frictional heat generation takes place that stimulates severe plastic deformation at the weld interface with an increase in temperature and introduces material softening which then forms a weld.[10]