Current Issue : October - December Volume : 2019 Issue Number : 4 Articles : 5 Articles
By controlling various friction stir spot-welded (FSSW) factors, two base sheets AA5052-H32\nand 6061-T6 were selected to bond similar and dissimilar metal joints while considering dissimilar\nconfiguration orders. The effects of weld parameters on the sheer strength and peel strength were\nseparately developed into empirical models utilizing the integrated central composite matrix design\nand response surface methodology (RSM). Meanwhile, the finite element (FE) analysis of the multi-axis\nload-bearing characteristics for automotive solder joints during service was carried out. As a result,\nthe weights of the shear and axial stress, accounting for 90.5% and 9.5% respectively, were employed\nto restrict the relationship between multiple target properties, and the resulting security strength\nwas applied to determine the feasible domain in subsequent parametric optimization. In order to\nenable the optimal multi-axis capacities in accordance with the load mode, the genetic algorithm\nNSGA-II was chosen to compute the Pareto front and further determine the best compromise solutions.\nThe obtained optimums corresponding to each joining condition were validated by confirmation runs,\nindicating that this coupled multi-objective optimization approach based on working conditions was\nbeneficial to the targeted improvement of post-weld mechanical properties....
The process class of sheet-bulk metal forming (SBMF) involves several advantages for the\nmanufacture of functional components. Its incremental variant (iSBMF) enables a very flexible\ndimensioning of components. To treat the unfavorable manufacturing time of the incremental\napproach, this investigation is focused on an alternative process route using rotating forming tools,\nwhich decrease the process time significantly. After an analysis of the mechanical properties as well\nas the micro- and macroscopic surface quality, a quasi-static benchmark test was performed.\nNormalized by the weight of the component, gears manufactured by iSBMF and BS600 steel\npresented the same load capacity as gears manufactured by blanking with subsequent hardening.\nHere, using innovative high strength steels with a significant strain hardening behavior like high\nmanganese steels enables for weight-reduced gears....
Synergistic effects during hybrid laser-arc welding may cause increased process efficiencies.\nHowever, the basic interactions behind these effects are still being discussed, with some contradictory\nreports. In this study, particular welding parameters of interest were systematically varied to further\nthe understanding of involved phenomena. The experimental trials are evaluated regarding their\nsynergistic achievements in terms of process efficiency, melting efficiency and energy coupling\nefficiency using a factorial two-level Design-of-Experiment (DoE) approach. The results show that\nthe growth in process efficiency can be attributed to a dramatic increase in melting efficiency whereas\nthe energy coupling efficiency is only moderately increased. Thus, the synergistic effect is mainly\ncaused by secondary mechanisms that change the energy usage inside the work piece while direct\ninteractions between the two heat sources can be excluded as a reasonable cause for increased process\nefficiencies. It is concluded that the different sizes of the heat sources change the heat and mass flow\npositively and consequently lead to a higher performance level....
A free-piston engine generator (FPEG) is a new type of energy converter, which eliminates the crankshaft and connecting rod\nmechanism. In order to achieve efficient energy conversion, the two-stroke thermodynamic performance optimization of a single cylinder\nfree-piston engine generator is investigated in this paper. Firstly, the components, four-stroke thermodynamic cycle, two stroke\nthermodynamic cycle, and prototype system of the FPEG are presented in detail. The one-dimensional flow simulation\nmodel of the FPEG is created based on the gas dynamics equation, Weber combustion function, and heat transfer function, and\nthen the model is validated by the data tested from the prototype system. According to the four-stroke experimental results of the\nFPEG, an effective power of 4.75kW and a peak pressure of 21.02 bar have been obtained. Then, the two-stroke thermodynamic\ncycle is simulated and compared under the different control parameters of intake air pressure, injection timing, ignition timing,\nand valve timing through the simulation model. The optimized results show that an indicated thermal efficiency of 27.6%, an\nindicated power of 6.7 kW, and a maximal working frequency of 25 Hz can be achieved by the prototype system, when the two stroke\nthermodynamic cycle is used....
Free-cutting steels are developed to produce large quantities of parts with low mechanical\nbehavior, mainly for automotive sector. These alloys contain phosphorous, lead, sulfur, and manganese\nthat help to improve the machinability and surface roughness. However, due to the toxicity of lead,\nsteel mills in recent years have been focusing on non-toxic steels to produce minimum environmental\npollution and better machinability. The present work investigates the tool wear during dry and\nwet turning of free-cutting steels (SAE 1212, SAE 12L14, and SAE 1215) by using uncoated hard\nmetal inserts at three cutting speeds. Additionally, a EDS analysis was performed to determine the\npresence of Mn and S elements at the rake face of the cutting tool that can induce a higher adhesion of\nmanganese sulfide (MnS). The results show that the SAE 12L14 steel has the best performance in\nterms of tool life at different cutting speeds. This difference is maximum at the lowest cutting speed,\nwhich gradually decreases with the increase of the cutting speed. The wear behavior is evaluated\nin the three steel alloys at each cutting speed and, consequently, the tool wear exhibits a slightly\nbetter performance in the dry machining condition for higher cutting speeds (180 and 240 m/min),\nindependent of the steel alloy. Finally, EDS analysis confirms the presence of Mn and S elements at\nthe rake face of the inserts machined in dry condition. Hence, MnS is expected to interpose between\nthe machined surface and cutting tool surface to behave similar to tribofilm by reducing the wear on\nthe cutting edge....
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