Band 67, Heft 2

The development of technology and the increase in needs have affected the manufacturing methods. It is of great importance to combine different materials to reduce costs and increase performance and design flexibility. Different parts can be joined by friction welding, which is a solid-state welding method. In this study, the weldability of AISI 304 stainless steel and AISI 1040 carbon steel with friction welding has been investigated. During welding, the temperature changes of the welds were measured. In addition to SEM, XRD, and EDS tests to examine the microstructure of the welds, tensile strength tests and hardness measurements were also performed to find out their mechanical characteristics. According to the analysis and test results, the best welding parameters were observed in the weld sample S6. As a result of this experimental study, it was seen that these different steels can be joined by friction welding.

Due to the dissimilar properties of the cladding layer and carbon steel substrate, which lead to inaccurate inspections, nondestructive testing (NDT) needs to be verified with a reference specimen. This research presented the preparation of stainless-clad steel reference for NDT with imaging inspections such as profile radiography (PRT), ultrasonic phased array (PA), and full matrix capture with the total focusing method (FMC/TFM). The effect of cladding thickness and complex defects on the inspection results was evaluated. In the experiment, the reference specimen was prepared by welding stainless steel on carbon steel and drilling holes to simulate defects as cluster, aligned, and interlayer characteristics. The PRT exhibited asymmetry in two-dimensional images with varying cladding thicknesses, which could be measured by image density analysis but could not identify complex defects. The PA provided images with good accuracy for measuring cladding thickness, but it was limited in detecting some complex defects due to signal reduction. The FMC/TFM demonstrated the best image for thickness measurement and identification of complex defects because its individual element probe could reduce signal intensity loss. In addition, a possible application of FMC/TFM in the butt weld inspection was also demonstrated.

The use of bio-inspired structures in vehicles is promising. The crashworthiness performance of crash boxes inspired by honeycomb, bamboo, and horsetail structures was compared according to impact simulations. Results were compared regarding specific energy absorption (SEA), peak crushing force (PCF), and specific energy absorption to peak crushing force ratio. Single and multi-objective optimization studies were carried out with a horsetail crash box, which gave the best results. This crash box design can be used in vehicles to improve passive safety.

Aiming at the characteristics of orthotropic anisotropy, multiangle and multilayer of carbon fiber composites, based on the relevant theories of mechanics of materials and mechanics of composites, a method of calculating the strain in the main direction of each ply inside the carbon fiber composite laminate by using the strain measured in the reverse order of the surface layer is proposed. In this study, carbon fiber composite laminates with different lay-up angles and thicknesses are selected as test objects, and the accuracy of the strain gauge measurement and rotational axis calculation method is verified by comparing the measured values of extensometer with those of the carbon fiber strain gauge that are different in the surface pasting direction. HyperMesh finite element software was used to simulate and solve the strain values in the main direction of the internal layers and compared with the strain in the main direction of the internal layers based on the surface strain measurement, which proved the validity of the method of calculating the strain in the main direction of the internal layers based on the surface strain measurement in inverse sequence.

Ferrotitanium is widely used in alloying stainless steels to enhance their strength, corrosion resistance, and high-temperature resistance. Ferrotitanium’s advantages over pure titanium – such as better solubility in the liquid steel bath and lower cost – have made it the preferred choice in stainless steel alloying. In this study, it was aimed to produce ferrotitanium alloy through the metallothermic reduction of Fe 2 O 3 and TiO 2 . The system’s thermodynamic modeling was performed using HSC Chemistry 6.12 and FactSage 7.1. The experimental studies investigated the effect of using aluminum as a reductant with varying stoichiometries on the total metal recovery yield, hardness, and microstructure. Atomic absorption spectrometry (AAS), optical microscopy, scanning electron microscopy (SEM), X-ray fluorescence spectrometry (XRF), and hardness measurement techniques were employed in characterization studies. The results of the experimental studies showed that the highest metal recovery yields were obtained with 105 % stoichiometric aluminum as 97.9 % for Fe and 100 % for Ti.

Many challenges are involved in solving mechanical design optimization problems related to the real-world, such as conflicting objectives, assorted design variables, discrete search space, intuitive flaws, and many locally optimal solutions. A comparison of algorithms on a given set of problems can provide us with insights into their performance, finding the best one to use, and potential improvements needed in their mechanisms to ensure maximum performance. This motivated our attempts to comprehensively compare eight recent meta-heuristics on 15 mechanical engineering design problems. Algorithms considered are water wave optimizer (WWO), butterfly optimization algorithm (BOA), Henry gas solubility optimizer (HGSO), Harris Hawks optimizer (HHO), ant lion optimizer (ALO), whale optimization algorithm (WOA), sine–cosine algorithm (SCA) and dragonfly algorithm (DA). Comparative performance analysis is based on the solution trait obtained from statistical tests and convergence plots. The results demonstrate the wide range of adaptability of considered algorithms for future applications.

AA8011 and mild steel are the most suitable candidates for several structural applications due to their unique properties. However, joining these two materials with fusion welding poses challenges for manufacturing engineers. As a result, it often leads to issues such as hot cracking, porosity, and alloy segregation due to incompatibilities in metallurgical factors. An alternative method, friction stir welding, is used to join these materials. While lap joint configuration is common in many sectors for joining different thicknesses, traditionally it has been performed using rivets, bolts, and fusion welding processes. In this investigation, friction stir spot welding is employed to eliminate the need for rivets. To analyse the influence of major process parameters on shear fracture load, a systematic analysis is conducted. From the experimental results, it is detected that the joint welded with a tool rotational speed of 1,000 rpm, plunge rate of 4 mm.min −1 , dwell time of 5 s, and a tool shoulder to pin diameter ratio of 3.0 exhibited peak load carrying capabilities of 9.46 kN. This can be attributed to the optimum levels of hook width, hook height and balanced material flow.

The primary objective of numerous optimization problems is to enhance a single metric whose lowest or highest value accurately reflects the response quality of a system. However, in some instances, relying solely on one metric is not practical, leading to the consideration of multi-objective (MO) optimization problems that aim to improve multiple performance indicators simultaneously. This approach requires the use of a multi-objective optimization method adept at handling the intricacies of scenarios with various indices. Consequently, researchers have not explored multi-objective truss optimization as extensively as single-objective (SO) scenarios. The novel multi-objective Lichtenberg algorithm with two archives (MOLA-2arc) has been developed to address this. The efficacy of MOLA-2arc is evaluated against eight other MO algorithms, including the multi-objective bat algorithm (MOBA), multi-objective crystal structure algorithm (MOCRY), multi-objective cuckoo search (MOCS), multi-objective firefly algorithm (MOFA), multi-objective flower pollination algorithm (MOFPA), multi-objective harmony search (MOHS), multi-objective jellyfish search (MOJS) algorithm, and the original multi-objective Lichtenberg algorithm (MOLA). The challenge is to minimize structural mass and compliance while adhering to stress limitations. The outcomes demonstrate that MOLA-2arc shows notable improvements over its predecessor, MOLA, and surpasses all other competing algorithms in this study.

The welding behavior of the resistance spot welded dissimilar TBF–HSLA300 steel joints under different welding parameters was investigated. TBF steels were used as galvanized or ungalvanized. Microstructural characterization and mechanical tests were performed. Higher heat input resulted in the higher possibility of shrinkage cavities at the weld nugget and also increased the risk of liquid metal embrittlement (LEM) crack in the heat affected zone (HAZ) on galvanized TBF steel sheets. A partial melting zone was observed on HSLA300 side. The welds with ungalvanized TBF sheets had the higher nugget size and indentation. The highest hardness values (over 500 HV0.1) were observed in HAZ on TBF side. The lowest hardness values (below 300 HV0.1) on TBF side were observed in a very narrow softening zone between tempered zone and base metal. The fractures of all spot welds in the tensile shear test occurred on the TBF steel side with the thinner thickness. Low-strength steel sheet have to be sufficiently thicker in order to achieve higher welding strength. Higher welding time led to higher weld strength in the ungalvanized TBF combination. In the galvanized TBF combination, higher heat input led to the drastic decrease in weld strength due to LEM cracks.

The current study presents a novel gradient-free metaheuristic search algorithm named Tactical Flight Optimizer (TFO), tailored to meet the growing need for high-performance optimization techniques in solving complex engineering and mathematical problems. The main contribution of this study is the development of a method that simulates tactical air combat formations, offering a sophisticated alternative to conventional search algorithms. In the proposed method, the location of each agent is updated based on a resultant vector derived from three updating vectors. The updating vectors incorporate total information stored by the agents in each iteration. Consequently, the navigation process is guided by a more logical mechanism rather than a simple random process. The search performance of the TFO is initially benchmarked by solving a set of constrained mathematical functions. Subsequently, it is evaluated by addressing a suite of constrained mechanical and structural problems, containing both discrete and continuous decision variables. The obtained results are compared with five other well-stablished metaheuristic techniques. Acquired numerical results indicate that the TFO algorithm can provide promising results in solving both mathematical and engineering problems in terms of computational cost, accuracy, and stability.

This study focuses on the optimum design of an auxetic energy absorber intended for automobile applications. The material chosen for this energy absorber is SCGA27D galvanized steel. This research proposes the utilization of an artificial neural network-assisted metaheuristic for optimizing automobile structural components. The geyser inspired algorithm (GEA), ship rescue algorithm, and mountain gazelle algorithm are employed to optimize an automobile energy absorber. The objective of the problem is to obtain optimal geometry for an energy absorber while simultaneously reducing mass and meeting energy absorption constraints. The findings demonstrate that both the GEA algorithm and SCGA27D galvanized steel material exhibit exceptional capabilities in designing vehicle structures.

Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This work focuses on testing machines operating in resonance, which allows for higher test frequencies and reduced test durations. Various types of fatigue testing machines, including those with rotating-unbalance actuators, servo-hydraulic actuators, and piezoelectric actuators, are examined through vibration analysis, methodical design, and mechatronics. Resonant testing machines provide significant advantages in energy efficiency and test accuracy for a wide range of applications in materials testing. These methods are crucial for future applications in industries where energy efficiency and precise fatigue testing are critical, such as aerospace, automotive, and civil engineering.

The effect of ultrasonic impact treatment (UIT) was studied on the surface microstructure, roughness parameters, micro- and nanoscale mechanical properties, surface residual stress, and nanoscale scratch and friction behavior of L-605 CoCrWNi alloy. According to the results, UIT increased the surface hardness of the L-605 alloy where the hardness of the 1-pass UITed sample (∼690 HV) was higher than that of the annealed alloy by about 120 %. This was attributed to the accumulation of strain, strain-induced martensitic transformation (SIMT), and the formation of ultrafine grains. The UIT also changed the tensile surface residual stress of the as-received L-605 sample to the compressive state. The stylus profilometry showed that applying 3-pass UIT substantially decreased the average roughness R a and resulted in a negative surface skewness with an improved ratio. According to the nanoindentation/nanoscratch results, applying the first pass of UIT increased the nanohardness, H E r −1 ratio, and H 3 E r −2 ratio by 230 %, 200 %, and 280 %, respectively. The UIT reduced the depth/width of the nanoscratch groove, lowered the amount of piled-up material, and substantially decreased the average friction coefficient (AFC).

In this study, the surface of AISI 1020 steel was coated with Ni/Ti and different ratios of SiC-reinforced Ni/Ti–XSiC powders by the self-combustion synthesis method using an inductive ignition system. The surface of AISI 1020 steel was coated with 25 g of Ni/Ti and SiC alloy powders at different ratios. After the coating process, optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy spot analysis (EDS) tests were applied to examine the microstructure of the alloyed surface. Also, wear and microhardness tests were run. The results showed that the ratio of SiC reinforcement should range between 4 wt.% and 12 wt.%, and the best wear resistance was achieved in the specimen reinforced with 4 wt.% SiC. Moreover, when the ratio of SiC reinforcement was greater than 4 wt.%, it caused a negative effect on the wear resistance.

In this work grain structure and tensile properties of as-cast and aged Pb–Sn–Ca alloys (with tin-to-calcium content ratio ranged from 2.6 to 3.3) used to produce negative grids for lead-acid batteries were determined. The microstructure of the alloys was studied by scanning microscopic and quantitative metallographic analyses. Mechanical properties in terms of ultimate tensile strength, yield strength, Young’s modulus, and elongation were estimated at room temperature using TIRAtest 2,300 universal testing machine. Based on the tensile test results, average stress-strain curves for aged Pb–Sn–Ca alloys were plotted for the subsequent age-strengthening analysis. The studies showed that the significant casting process parameter was the mold temperature that markedly affected grain structure of the alloys. With mold temperature rising from 60 °C to 170 °C, an average grain size was increased by as much as two-fold. As a result, elongation increased by 55 %, but ultimate tensile strength decreased by 25 %. Ageing time affected grain structure of the alloys to a much lesser degree since the change in average grain size was negligible. Strengthening occurred rapidly within first 3 days of ageing during storage at ambient temperature. With ageing time prolonged up to 35 days no appreciable differences in the tensile properties’ values were found.