Volume 64, Issue 7

Thin strips of electrochemically deposited nanocrystalline nickel-iron with thicknesses of 320 or 330 µm are modified by defined grinding. Small changes in the cutting depth and the variation of the grinding process, up cut or down cut, result in different surface states. X-ray diffraction provides the analyses of the microstructures and residual stresses on the surfaces. In the initial state, the grain sizes have an average value of 9.3 nm, the micro strains 0.74% and the residual stresses predominantly values in the low-pressure range. Up grinding with the smallest depth of cut 1 µm causes the lowest compressive residual stresses at workpiece surface due to cold plastic deformation. Larger cutting depths and surface temperatures reduce the mechanical effects. Then prevailing thermal effects cause tensile residual stresses through thermoplastic deformation and through changes in the microstructure, which can be observed by grain enlargements and decreases in micro strains. However, the recovery and recrystallization processes are only partial. Down grinding with a cutting depth of 3 µm thus leads to a maximum grain size increase to 23.4 nm and a maximum decrease in micro strain to 0.41% as well as to maximum residual stresses of 880 MPa.

In this study, design optimization of the lower control arm, one of the main parts of double wishbone system widely used in the armored wheeled vehicles, is performed. The crucial factor in design is to keep the vehicle weight at a minimum especially for the amphibious vehicles that can operate in both the land and water. In this study, after the validation of the finite element (FE) analysis of suspension lower control arm with on-vehicle tests, weight optimization study is performed by using surrogate models. In FE model validation, strain values are collected with strain-gauge from the lower control arm of the 8 × 8 wheeled vehicle and the similar boundary conditions are applied to the FE model. A surrogate based approach is used in optimization. The training points for surrogate models are generated by using central composite design. Genetic aggregation surrogate modelling technique available in ANSYS Workbench. It is found that the weight of the control arm can be reduced from 25.2 to 21.8 kg, indicating a weight reduction of 13.3%. This leads to approximately 27 kg weight reduction in total for 8 × 8 vehicle. Finally, the performance of the optimized design is evaluated under two off-design quasi-static load scenarios (pothole strike and pavement crushing) that may be exposed on the suspension while the vehicle is in motion and preferred by vehicle manufacturers. It is observed that obtained stress values are below the yield strength of the material, and the off design performance of the control arm is verified with the safety factor of 1.46 for pothole strike scenario, and 1.08 for pavement crushing.

Laser beam welding under vacuum (LaVa) offers advantages regarding the achievable weld penetration depths compared to conventional laser beam welding. Thus, it is increasingly used in industry. Despite the high weld penetration depths that can be achieved and the good inner seam qualities, undesirable reworking is often necessary due to surface deposits on the welded sample. The causes of these surface deposits have not yet been investigated in depth. In this context, the influence of the residual oxygen present inside the vacuum chamber is investigated in this study. For this purpose, the oxygen content within the chamber is recorded for LaVa welds at different working pressures and different evacuation times. The welded specimens are evaluated metallographically and investigated with regard to an influence of the oxygen content within the working chamber. This study shows that the residual oxygen content considerably influences the weld formation and the surface weld appearance for all working pressures investigated. For lower oxygen contents, the weld penetration depth decreases, and the weld width, on the other hand, increases. These observations can be explained in good agreement with findings for the influence of oxygen on the weld appearance for other material joining processes, such as TIG welding.

Although the electrical system is important in the development of electric vehicles, the durability of the battery system against mechanical loads and the performance of the battery against shock reactions are just as important. The objective of this study is to develop a methodology to determine the structural life of the battery of the C-platform sports utility vehicle (SUV). For this purpose, a power spectral density (PSD) durability test profile is generated and compared to battery test standards such as ISO 6469:2019, AK-LH 5.21 and SAE J2380. Analytical Virtual Proving Ground (VPG), a multibody dynamics simulation model, is also developed and correlated to test data. The results show that FDS values for AK-LH is higher than the fatigue damage of the collected vehicle data, while the FDS results for ISO standard are lower compared to the vehicle data. The results also indicate that the loads in the longitudinal ( x -direction) and lateral ( y -direction) directions are different. Therefore, loads of different amplitudes should be used for these directions, contrary to SAE J2380 and USABC standards. Finally, it is concluded that the VPG model can be used for determining the fatigue life when there is no test data, thanks to its high accuracy.

Cobalt-based alloys, called Stellite, have a microstructure consisting of complex carbides dispersed in a Co-based solid solution matrix. These alloys are resistant to corrosion, erosion through cavitation, abrasive, and sliding wear. To increase the erosion resistance through cavitation, hardfacing of the stainless steel duplex X2CrNiMoN22-5-3 with Stellite 21 alloy was performed using the pulsed tungsten inert gas (TIG) process. The positive effects of the hardfacing process are the low heat input, reduced distortions, controlled volume of the weld, and reduced susceptibility to hot cracking. The effect of dilution is essential for the quality of the deposited layers and, in this sense, the TIG pulsed current welding process was performed to reduce the excess linear energy and implicitly the substrate melting. Iron dilution levels were in the range between 5.9 and 6.1. The higher Fe content in the first layer does not significantly reduce its hardness or wear resistance through erosion cavitation. Compared with the substrate material, the cavity erosion resistance increases 7 to 11 times even in the first layer hardened by the TIG pulsed current welding process.

In this work, the dynamic fracture behavior of 11MnNiMo steel under medium-low loading rate was studied. In the fracture morphology with and without prefab crack, the fracture surface had obvious morphological partition phenomenon. In comparison, there were more crack roots in the crack root region with preset cracks and gradually expanded to the interior. Transmission analysis showed that there were many displacements in the matrix and dispersed secondary phase particles, which should be MnS impurity phase. In the microstructure of 11MnNiMo matrix, the elongated morphology of lath martensite structure was retained. During the process of impact shear deformation, massive plastic deformation was associated with the material, so that a great deal of displacements led to the movement of the slip system. At the same time, the transmission analysis showed that there was elastic stress inside the impact fracture.

In this study, the high-velocity impact behavior of Ramor 500 armor steel was investigated experimentally and numerically. For this purpose, the steel specimen was impacted by a 9 mm Parabellum full metal jacket (FMJ) bullet at the reliable polygon. On the other hand, the mechanical properties of specimens were found by a tensile test at different temperatures and Johnson–Cook (J-C) parameters were obtained by Split Hopkinson Pressure Bar (SHPB) test data. By using these data, the same test was simulated by ANSYS Explicit Dynamic. Results show that experimental and numerical results provide NIJ LEVEL IIIA conditions. In addition, the perforation thickness of Ramor 500 at the constant projectile velocity and the perforation velocity at the constant thickness were obtained by using ANSYS Explicit Dynamic.

In this study, the microstructural characterization of a solution annealed and quenched EN AW 6082 alloy was performed that was subjected to cold deformation (10 and 30%) and equal channel angular pressing. The findings showed that a band structure was formed, the crystallite size decreased significantly as well as that the dislocation density and stored energy increased due to severe plastic deformation. Static and dynamic precipitations in the processed alloys were characterized by thermal analyses and it was observed that precipitation sequence in heating shifted to lower temperatures due to increased kinetics caused by deformation. Increased precipitation kinetics due to severe plastic deformation could be seen in the variation of hardness during aging at 190 °C and the peak hardness of deformed alloys shifted to shorter aging times. The peak hardness of conventional heat-treated alloy was attained as 122 HV 0.5 for 300 min, whereas the same hardness was achieved for an aging time of 45 min in the 30% cold-deformed alloy. By severe plastic deformation, the highest peak hardness was obtained as 130 HV 0.5 after aging for 15 min. Microstructural characterization on overaged alloys indicated that the alloy having the highest stored energy had the highest tendency for recrystallization.

This study was aimed to produce and test dental implants made out of biocompatible commercial pure titanium (Grade 4) material with improved mechanical strength. The implant samples were designed and manufactured in real sizes using both machining and thread-rolling (TR) processes. This study is also discovering the benefits of cold forming (TR) versus machining processes in terms of increased efficient strength and reduced costs. To produce the samples using the TR method, a suitable TR processing bench including a pair of reverse threaded flat dies and relevant jigs and fixtures were designed and manufactured. The produced implant samples were tested with static and dynamic loads considering the requirements of the ISO14801:2016 standards. The obtained results were compared in terms of mechanical strength and fatigue life. Their microscopic structures and micro-hardnesses were examined to realize the effects of the manufacturing processes. In addition, the effects of hardness, surface roughness, and residual stresses on both mechanical strength and fatigue life of the implants were also evaluated. Therefore, the obtained results showed that the TR process is extremely effective to improve the implant strength and fatigue life.

The effects of thermomechanical processing on the grain size, tensile strength, and strain rate of a CuZn10 alloy were investigated. Microstructures of thermomechanically treated samples were introduced using a scanning electron microscope. The relationships between the flow stress, reduction ratio, annealing temperatures, and strain rates were detected for determination of activation energies and optimized thermomechanical parameters. The effect of grain size on the mechanical properties was examined by tensile and microhardness tests. The typical fractographs of samples after tensile tests were examined using a scanning electron microscope. It was observed that the annealing temperature and aging time have significant effects on the optimum grain size. Mechanical properties of the thermomechanically treated samples were improved by strain rate, deformation ratio, annealing temperature, and aging time.

Austenitic stainless steels are mainly preferred especially for resistance to aggressive oxidizing medias and high temperature applications such as equipments and mechanical parts which are used in defense and conventional industries. In this study; 3 mm thick 304L austenitic stainless steel sheets and rings are joined to each other by using Tungsten Inert Gas welding method under pure argon shielding gas with ER316L and ER2209 filler metals. Weld metals and heat-affected zones of welded joints were examined by metallurgical and scanning electron microscopes. Microhardness, tensile and Charpy impact tests of weld regions are investigated. It has been determined that the filler metals have dominantly changed the microstructure of weld metals. The microhardness values of the welded samples joined with ER2209 filler metal was lower than the sample joined with ER316L filler metal in weld metal regions. Besides, corrosion tests indicated that the corrosion rates of welded samples joined with ER2209 filler metal is lower than the samples joined with ER316L filler metal.

Nature-inspired algorithms known as metaheuristics have been significantly adopted by large-scale organizations and the engineering research domain due their several advantages over the classical optimization techniques. In the present article, a novel hybrid metaheuristic algorithm (HAHA-SA) based on the artificial hummingbird algorithm (AHA) and simulated annealing problem is proposed to improve the performance of the AHA. To check the performance of the HAHA-SA, it was applied to solve three constrained engineering design problems. For comparative analysis, the results of all considered cases are compared to the well-known optimizers. The statistical results demonstrate the dominance of the HAHA-SA in solving complex multi-constrained design optimization problems efficiently. Overall study shows the robustness of the adopted algorithm and develops future opportunities to optimize critical engineering problems using the HAHA-SA.

A newly hybrid algorithm is proposed based on the combination of seeker optimization algorithm and particle swarm optimization. The hybrid algorithm is based on a double population evolution strategy, and the populations of individuals are evolved from the seeker optimization algorithm and the particle swarm optimization separately. The populations of individuals employ an information sharing mechanism to implement coevolution. The hybrid algorithm enhances the individuals’ diversity and averts fall into the local optimum. The hybrid algorithm is compared with particle swarm optimization, the simulated annealing and genetic algorithm, the dragonfly algorithm, the brain storming algorithm, the gravitational search algorithm, the sine cosine algorithm, the salp swarm algorithm, the multi-verse optimizer, and the seeker optimization algorithm, then 15 benchmark functions, five proportional integral differential control parameters models, and six constrained engineering optimization problems are selected for optimization experiment. According to the experimental results, the hybrid algorithm can be used in the benchmark functions, the proportional integral differential control parameters optimization, and in the optimization constrained engineering problems. The optimization ability and robustness of the hybrid algorithm are better.

In aerospace industry, optimizing designs has become inevitable in terms of weight and performance requirements. Topology optimization is the most suitable optimization type for use in the conceptual design phase. Even though academic topology optimization algorithms have a modular structure (open to development), they are often useable for a regular design domain. Alternatively, commercial topology optimization software products, on the other hand, are very useful in terms of their solution speed, accuracy, and ability to handle complex or irregular design domains. However, the user is restricted with the optimization algorithms available in the software, and these software do not usually have a modular structure. In this study, a modular topology optimization framework that combines useful features of the academic codes (e.g., modularity) and the commercial software tools (e.g., capability of easily handling complex design domains) is developed. The developed framework is tested on two popular academic topology optimization problems, followed by aerospace bracket design problem. It is observed that the proposed framework usually provides lower objective function values and converges to the optimum result in fewer iterations than the Altair Optistruct topology optimization software.