Band 65, Heft 12

To flake aluminum powder and strengthen the B 4 Cp/Al composite, pure aluminum powder is natural oxidized and ball milled. The effect of shear deformation on mechanical properties of the forged B 4 Cp/Al composite with flaked Al are studied. The results show that ball milling can flake the pure aluminum powder, reduce grain size of aluminum, and increase the volume fraction of Al 2 O 3 on the surface of the flaked aluminum. The forging helps to refine the grain size of aluminum. The flow of aluminum matrix is helpful to the uniform distribution of the B 4 C particles. Shear deformation can refine grain size and also can break the Al 2 O 3 layer, with the increment of strength, hardness, and relative density. After shear deformation, the ultimate tensile strength of the B 4 Cp/Al composite is 157.0 MPa.

Since mechanical properties of parts in mechanical engineering are influenced in many ways by their surface structure, detailed knowledge of the surface structure is essential for predicting and describing these properties. Tactile and optical measurement methods are well established but cannot always reach every area of a part due to geometric constraints. To enable measurements in these areas, a method utilizing impressions and a laser scanning microscope is proposed. It is easy to use and able to correctly reproduce surface structures of technical surfaces, which is proven by a comparison of original parts and impressions of three surface areas on an example specimen. Two application examples from the domain of fatigue strength tests are shown. The surface structure is measured directly in the notch radius of shaft shoulders and inside hollow shafts made in different manufacturing processes. Utilizing modern optical measurement instruments, the proposed method enables accurate measurements of surface structure in previously inaccessible areas.

Nature-inspired metaheuristic algorithms are gaining popularity with their easy applicability and ability to avoid local optimum points, and they are spreading to wide application areas. Meta-heuristic optimization algorithms are used to achieve an optimum design in engineering problems aiming to obtain lightweight designs. In this article, structural optimization methods are used in the process of achieving the optimum design of a seat bracket. As a result of topology optimization, a new concept design of the bracket was created and used in shape optimization. In the shape optimization, the mass and stress values obtained depending on the variables, constraint, and objective functions were created by using artificial neural networks. The optimization problem based on mass minimization is solved by applying the dandelion optimization algorithm and verified by finite element analysis.

A large number of metal parts specific to the aviation, energy, and biomedical industries are produced by the electron beam melting (EBM) method, which is one of the powder bed additive manufacturing techniques. The limited build volume of EBM machines does not allow the production of parts in the desired dimensions. One way to overcome this limitation is to weld small size additive manufactured parts. In this study, EBMed Ti6Al4V tensile specimens were joined by laser (LBW) and tungsten inert gas (TIG) welding. Welding morphologies, microstructures, and mechanical properties of joints were investigated. The main defects in the samples are pore formation and insufficient penetration. The weld zones of TIG samples contain a higher amount of pores than laser samples, and these pores are distributed over the entire area of the weld. The pores are less than 200 µm in diameter. TIG welded samples exhibited higher mechanical properties than laser welded samples. The highest microhardness was measured in the weld zone. Microhardness of laser welded samples are higher than TIG welded samples. While the welding regions of TIG welded samples consist of coarse and acicular α and α + β structures, laser welded samples consist of thin and acicular α′ structure.

The multi-pass fillet welds of casing pipe were welded onto the in-service pipeline, which is widely used in pipeline repairs. However, the influence of welding heat input of B-type sleeve circumferential fillet weld on the temperature and stress field at the pipe circumferential weld is still unclear. In this paper, a double ellipsoid heat source model is developed to investigate the weld temperature field, residual stress field, and deformation field of the repair welding in service. The results show that the increase of weld heat input can effectively increase the size of the weld pool and the size of the high-temperature zone of the B-type sleeve circumferential fillet weld. And the peak temperature of the inner wall of the pipe girth weld increases with the increase of welding heat input of the sleeve circumferential fillet weld. The axial stress peak of the inner wall of the pipe girth weld reduces with the increase of welding heat input of sleeve circumferential fillet weld, and the axial deformation peak of the inner wall of the pipe girth weld increases first and then decreases with the increase of welding heat input of sleeve circumferential fillet weld.

In recent years, there has been a logarithmic interest in three-dimensional printing technologies. This technique has made it possible to make more intricately shaped parts of superior quality, allowing for use in a variety of industries, including aircraft, automobiles, and ships. This study characterized the materials and assessed the mechanical features of PLA, PETG, and ABS materials generated at various raster angles. The strength ratios of the various materials have been found to fluctuate when the raster angles change. The PLA parts created at a picture raster angle of 45° had the maximum tensile strength. ABS material created with a picture raster angle of 45° has been shown to have the best energy absorption, and PLA material made with a raster angle of 45° has the best performance compressive strength. When bending strength was evaluated, it was found that samples of ABS made with a raster angle of 0–90° had the greatest value. The SEM micrographs were obtained, and the tensile test was used to examine the fracture behavior of the materials. As a result, it has been found that materials created using various raster angles can have various strength values from one another.

Almond gum and varied concentrations of nanosilica (0.2, 0.4, 0.6, 0.8, and 1.0 wt%) were introduced into the chitosan polymer matrix by solution cast method to enrich the characteristics of the bionanocomposite film. The surface topography, thermal stability, crystalline nature, and functional moieties of the synthesized bionanocomposite films were characterized by SEM, TGA, XRD, and FT-IR. The UV–Vis spectrophotometer showed a maximum absorption wavelength for the film containing the highest concentration of nanosilica. Change in properties such as increased tensile strength, elongation and reduced water solubility, and swelling properties were observed for the bionanocomposite film containing 1.0 wt% nanosilica. In addition, the films exhibited excellent inhibition effect against Escherichia coli bacteria and Candida albicans fungus, which were proven by well diffusion assay method. The carrot slices packed in the bionanocomposite film containing the highest amount of nanosilica retained their freshness for a longer period of time, suggesting the film to be an effective and excellent food packaging material.

In this article, a recently developed physics-based Fick’s law optimization algorithm is utilized to solve engineering optimization challenges. The performance of the algorithm is further improved by incorporating quasi-oppositional–based techniques at the programming level. The modified algorithm was applied to optimize the rolling element bearing system, robot gripper, planetary gear system, and hydrostatic thrust bearing, along with shape optimization of the vehicle bracket system. Accordingly, the algorithm realizes promising statistical results compared to the rest of the well-known algorithms. Furthermore, the required number of iterations was comparatively less required to attain the global optimum solution. Moreover, deviations in the results were the least even when other optimizers provided better or more competitive results. This being said that this optimization algorithm can be adopted for a critical and wide range of industrial and real-world challenges optimization.

In this study, hybrid (carbon, glass, and aramid) fabric epoxy composite laminates were fabricated with different layering sequences by hand lay-up. The effects of layering arrangements of laminated composite fibers on the mechanical properties of hybrid composites were investigated. Tensile, bending, and impact tests were performed to obtain the mechanical behaviors of hybrid composites. It was found that the layering sequences significantly affect the tensile, bending strength, and impact energy. As a result of the tensile tests, the highest tensile strength was obtained in the 3C + 3G combination. The highest load-carrying capacity in three-point bending tests was obtained in the 2G + 2A + 2C combination. The combination with the highest impact energy was 2C + 2G + 2A, and the lowest was 3C + 3G. It has been observed that hybrid composites containing aramid fiber absorb higher impact energy than others. The results showed that the layering sequences are essential in hybrid composites with the same fiber and layer number.

Super duplex stainless steel (SDSS) plates of 6 mm thickness have been welded using tungsten inert gas, activated tungsten inert gas, electron beam welding and friction stir welding processes. Among these, in the first two, melting and solidification of material occurs slowly whereas, it is faster in electron beam welding process and no melting occurs in friction stir welding. Macro and microstructural studies, hardness surveys, tensile tests and percentage of ferrite content were compared for all the welds. The ferrite–austenite phase balance is 50 % each, with electron beam weld metal at about 65 % ferrite. This showed the hardness of the weld metal and heat affected zones to be higher than base metal. The weldment joint efficiencies are more than 90 %. The fracture location is found to be in the weld metal for tungsten inert gas and activated tungsten inert gas weld, in the nugget for friction stir welds and in the base metal for electron beam welds. The ductility of electron beam weld joints is 32 % while it is around 20 % for the others. The preferred order while choosing the welding process should be activated tungsten inert gas welding, tungsten inert gas welding, electron beam welding, and friction stir welding.

With the new manufacturing technologies, it has been possible to machine hard metals efficiently. During high-speed machining (HSM) of high-strength steel, the poor surface integrity of the workpiece affects the performance of the process. Surface roughness, microstructure, microhardness and residual stress are key performance indices for surface integrity directly controlled by tool wear and cutting parameters. In this study, high-feed milling (HFM) of a pocket on test samples made of DIN 1.2344 ESR mould steel with 55 HRc hardness was carried out on the CNC vertical milling machine. Three different cutting speeds and five different feed rates were used. At the end of the machining, tool wear was measured using a microscope. Subsequently, X-ray diffraction and hole drilling procedures were used to quantify residual stresses on machined test specimens. The results showed that under cutting conditions, the highest tensile residual stress was attained at f z  = 0.78 mm·tooth −1 , v  = 127.58 m·min −1 , and the highest compressive residual stress at f z  = 0.5 mm·tooth −1 , v  = 127.58 m·min −1 , on the workpiece surface. The most suitable cutting parameters were reported as f z  = 0.63 mm·tooth −1 and v  = 70 m·min −1 cutting speed when tool wear and residual stresses are considered together.

Composite materials have a wide range of applications in many industries due to their manufacturability, high strength values, and light filling. The sector where composite materials are mostly used is the aviation industry. Today, as a result of the development of aviation systems, drones have started to be actively used, and many studies have started to be carried out to mitigate them. In this study, the subcarrier part, which is part of the drone, was designed using glass and carbon fiber–reinforced composite materials. Using the data obtained at the end of the analysis, the stacking angle with the optimal displacement and stress value was determined by using the genetic algorithm (GA), gray wolf algorithm (GWO), and slime mold optimization (SMO) techniques in order to develop a carrier with a minimum displacement and stress value of more than 60 MPa. As a result of the optimization, it was determined that artificial intelligence algorithms could be used effectively in determining the stacking angle of composite materials, and the optimum values were determined in the slime mold algorithm.

The crashworthiness and deformation behavior of circular composite tubes that were internally supported with expanded polypropylene (EPP) foams were investigated under lateral compression tests. Carbon woven (CFRP) and glass woven fiber/epoxy (GFRP) composites and EPP foam with densities of 30, 60, and 75 kg·m −3 were used. According to results, empty CFRP and GFRP tubes absorbed almost the same amount of energy; however, the GFRP tube had a higher specific energy absorption value due to its lower weight compared to the CFRP tube. EPP foam filling has a more significant effect on the crashworthiness of CFRP tubes compared to GFRP tubes. The best results in CFRP tubes, in terms of specific energy absorption, were obtained as 2.67 J g −1 at 75 kg·m −3 EPP foam-filled sample; however, 60 kg·m −3 EPP foam–filled sample exhibited the best configuration in terms of force efficiency. For the GFRP tubes, the best configuration was obtained at 60 kg·m −3 EPP foam–filled sample for all of the crashworthiness parameters. It is seen that the crushable length of composite tubes was shortened with the increase of EPP foam density. Lastly, the deformation behaviors of composite tubes showed that the CFRP tubes were more brittle than the GFRP tubes.

The mechanical, thermal, and morphological analysis of red mud filled sisal/glass fiber–reinforced polyester composites have been investigated. In this study, four composite specimens were prepared through hand layup technique by changing the weight percentage of sisal fiber and red mud. Weight percentage of glass fiber and polyester resin are kept constant. The fabricated composite specimens were subjected to mechanical properties such as hardness, impact and tensile behavior, thermal, and morphological analysis. From the results, it is observed that, maximum tensile strength of 45.6 MPa was obtained for C1 specimen. Maximum hardness and impact strength of 85.67 and 391.5 J m −1 was achieved for C2 specimen. In TGA study, C1 and C2 specimen exhibited 85 % of weight loss with the temperature ranges from 300 °C to 400 °C. From SEM analysis, good bonding between fiber and matrix, voids, fiber breakages, fiber pullout, delamination, rich matrix area, poor adhesion between fiber and matrix, poor arrangement of fibers, interlinked fibers, and crack propagation were observed. Based on the results, C2 specimen which contains 30 wt% of sisal fiber and 5 wt% of red mud is performed well than other composites and it is suitable for various applications such as marine, automobile, and aeronautical.

In this study, composite plates adhesively joined using single-lap joint without intermediated material (SLJ) and intermediated material (IM-SLJ) subject to bending loading were investigated via finite element analysis. DP 410 type adhesive was used. Composite parts and intermediate material were preferred as T700 carbon/epoxy. Numerical analyses were carried out using ANSYS 14.5 software package, in which the finite element method was taken into account. Failure situations for adhesive and composites were examined by the von-Mises failure criteria and the Tsai-wu failure criteria, respectively. Firstly, the failure loads for each parameter situation were determined. The equivalent stresses of the critical stress lines on adhesive layers were examined and critical stresses line were determined for length and width of adhesive layers. Shear, normal, and von-Mises stresses were investigated at obtained failure load for each parameter of SLJ and IM-SLJ. The von-Mises on the critical stress lines were compared for different overlap width and length of SLJ and IM-SLJ. The effects of joint techniques, orientation angles, and overlap dimensional were investigated on adhesive layer, and joint techniques were compared about advantages. A different study from the literature was carried out to compare the mechanical behavior of SLJ and IM-SLJ joining techniques.