Band 61, Heft 8

This research work aims to study the effects of pre-weld and post-weld heat treatment conditions in the laser welding process on the microstructure of cast nickel based superalloy grade, GTD-111. Pre-weld heat treatment conditions consist of a solution treatment at a temperature of 1473 K for 7.2 ks and three over-aging processes at temperatures of 1393, 1413, 1433 K for 7.2 ks. All as-received and pre-weld heat treated specimens received the same post-weld heat treatment, which consisted of a solution treatment at a temperature of 1473 K for 7.2 ks and precipitation aging at a temperature of 1118 K for 86.4 ks. From the results, it can be seen that the higher temperature of the solution treatment with respect to the pre-weld heat treatment provided coarser gamma prime particles precipitating in a gamma matrix with a more uniform microstructure and very fine gamma prime precipitated particles. Furthermore, when followed by the post-weld heat treatment or standard heat treatment of the alloy, the final microstructures of all as-received and pre-weld heat treated specimens were very similar with regard to uniform gamma prime particles. No significant effect of pre-weld heat treatment conditions on the microstructure was found after post-weld heat treatment.

This study performs fatigue tests by using a small specimen of Sn3.0Ag0.5Cu solder at 313 and 353 K. The specimen has a 3 mm-diameter gage section and a gage length and total length of 6 and 55 mm The specimen is heated in an electric furnace to control the temperature within ±1 K from the target temperature. The strain ranges employed are 0.5 %, 0.7 %, 1.0 %, and 1.5 %. A triangular waveform with 0.5 % × s −1 strain rate is adopted. The number of cycles to failure (failure life) N f is defined as the number of cycles that causes a 25 % decrease of stress amplitude from that at the middle of the lifespan or at specimen breakage. The relationship between the strain range and failure life at 313 and 353 K coincides well, and no variation of the failure life with the test temperature is identified. Stress amplitudes decrease with increasing cycles and decrease faster for higher strain ranges because of higher crack propagation rates. The degree of relaxation in the stress amplitude is larger at 353 K than at 313 K. Crack observation of the fatigued specimens is performed to discuss the relationship between crack propagation and the failure life of solders. The relationship among slips, microcracks, and main cracks is discussed, and the mechanisms for fatigue failure are proposed. Almost no change in the crack morphology is observed at 313 and 353 K, and this result is related to the lack of changes in the failure mechanism because of the change in the test temperature.

In this research, the Harris hawks optimization algorithm (HHO), the grasshopper optimization algorithm (GOA) and the multi-verse optimization algorithm (MVO) have been used in solving manufacturing optimization problems. This paper is the first research study for the optimization of processing parameters for manufacturing processes using the HHO, the GOA, and the MVO in the literature, and in particular, for grinding operations. A well-known grinding optimization problem is solved to prove how effective the HHO, the GOA and the MVO are in solving manufacturing problems and to demonstrate superiority over other algorithms. The results of the HHO, the GOA and the MVO are compared with other methods such as the genetic algorithm, the ant colony algorithm, the scatter search, the differential evolution algorithm, the particle swarm optimization algorithm, simulated annealing, the artificial bee colony, harmony search, improved differential evolution, the hybrid particle swarm algorithm, teaching learning-based optimization algorithms, the cuckoo search, and the fractal search algorithm. The results show that the HHO, the GOA, and the MVO are efficient optimization approaches for obtaining optimal manufacturing variables in manufacturing operations.

In this paper, a novel hybrid optimization algorithm (H-HHONM) which combines the Nelder-Mead local search algorithm with the Harris hawks optimization algorithm is proposed for solving real-world optimization problems. This paper is the first research study in which both the Harris hawks optimization algorithm and the H-HHONM are applied for the optimization of process parameters in milling operations. The H-HHONM is evaluated using well-known benchmark problems such as the three-bar truss problem, cantilever beam problem, and welded beam problem. Finally, a milling manufacturing optimization problem is solved for investigating the performance of the H-HHONM. Additionally, the salp swarm algorithm is used to solve the milling problem. The results of the H-HHONM for design and manufacturing problems solved in this paper are compared with other optimization algorithms presented in the literature such as the ant colony algorithm, genetic algorithm, particle swarm optimization algorithm, simulated annealing algorithm, artificial bee colony algorithm, teaching learning-based optimization algorithm, cuckoo search algorithm, multi-verse optimization algorithm, Harris hawks optimization optimization algorithm, gravitational search algorithm, ant lion optimizer, moth-flame optimization algorithm, symbiotic organisms search algorithm, and mine blast algorithm. The results show that H-HHONM is an effective optimization approach for optimizing both design and manufacturing optimization problems.

There is a growing interest in designing lightweight and low-cost vehicles. In this research, the Harris hawks optimization algorithm (the HHO), the salp swarm algorithm (SSA), the grasshopper optimization algorithm(GOA), and the dragonfly algorithm (DA) are introduced to solve shape optimization problems in the automotive industry. This research is the first application of the HHO, the SSA, the GOA, and the DA to shape design optimization problems in the literature. In this paper, the HHO, the SSA, and the DA algorithms are used for shape optimization of a vehicle brake pedal to prove how the HHO, the SSA, the GOA, and the DA can be used for solving shape optimization problems. The results show the ability of the HHO, the SSA, the GOA, and the DA to design better optimal components.

The axial crushing behavior and energy absorption ability of metallic tubes are areas in which a large number of academic studies have been undertaken. In this study, the basic steps in the progressive folding behavior of circular-sectioned aluminum tubes under axial loading, changes in tube geometry after deformation and the ability to absorb energy were investigated both experimentally and by the finite element method. The deformation behavior of an aluminum tube wall, derived from finite element analysis was validated by experimental results with a degree of accuracy reaching 99 %. In addition, absorbed energy values approached the experimental results by approximately 93 %. As a result, the folding behavior of aluminum tubes under axial loading was successfully investigated using the finite element method. Thus, some difficulties and costs in experimental studies could be overcome.

In this study, a powder mixture containing Al-Zn and Al 2 O 3 particles on AA6083 aluminum alloy was coated by the cold spray method. In order to investigate the effect of the substrate surface properties on the composite coating structure obtained by the cold spray process, the substrate surface was prepared by grit blasting and shot peening. It was found that Al and Zn particles in the coatings of all samples flattened near the substrate surface regions due to the deformation effect. But, Zn particles, because of their low hardness in contrast to the shot peened surface fragmented near the material surface regions through the impact. Similarly, the size of the Al 2 O 3 particles decreased incrementally from the coated surface to the substrate. Particularly in the shot peened samples, the size of the Al 2 O 3 particles decreased by striking the hard substrate surface and fracturing more. Moreover, the amount of Al 2 O 3 particles in the substrate surface of all samples was lower as the particles rebounded. It was also found that pore formation in the coating layer of all samples was very limited. Pore formation in the shot peened samples was by contrast lower than in the grit blasted samples. In addition, a very low oxide layer was found between the particles in the upper region of both the grit blasted and shot peened samples' coating layer.

Uncertainty is the scientific representation of the quality level and dispersion of measured results. Considering the problems with the current classical uncertainty evaluation method (namely, the GUM method), such as the repeated evaluation, omission and difficulties in quantifying uncertainty components, a ‘top-down’ approach represented by the control chart method is proposed, using the intermediate precision standard deviation of laboratory quality control data accumulated over a long period of time to indicate measurement uncertainty. Based on the principle of the ‘top-down’ approach, a new evaluation method for the measurement uncertainty of laboratory quality control data is proposed here, which use the standard deviation defined by grey system theory to indicate uncertainty (abbreviated as quality control – grey method). Furthermore, we have evaluated the measurement uncertainty of hydrogen in titanium using the quality control -grey system theory method, based on quality control data according to the inert gas fusion thermal conductivity method in the laboratory. The results achieved are 12.6 ± 4.0 μg × g −1 , k = 2, which is consistent with the value of 12.6 ± 3.5 μg × g −1 , k = 2, evaluated by the quality control chart method. The quality control-grey evaluation method developed a top-down uncertainty estimate approach and provides a new idea and tool for physical and chemical laboratories to evaluate measurement uncertainty using quality control data that has been accumulated.

The current study presents an experimental investigation aimed at exploring the effects of intraply fiber hybridization on the apparent hoop tensile and compression behavior of glass/carbon filament wound composite pipes by conducting split-disk and external parallel-plate loading tests, respectively. The efficiency of the hybridization process is also analyzed for a variation in fiber orientation by preparing composite pipes of different winding angles. The results show that a deterioration occurs in the apparent tensile strength of hybrid composites because of the weak interfacial adhesion between carbon and glass reinforcements. However, the compression behavior of glass fiber wound composite pipes, in terms of pipe stiffness and the stiffness factor, increases with the inclusion of carbon fiber. The increase in pipe stiffness and the stiffness factor are in the range of 10 and 20 %, respectively. Failure modes of the samples have also been discussed to understand fracture mechanisms. In conclusion, the intraply hybridization exercises significant influence, especially in the apparent hoop tensile characteristics of the pipes.

In the present research paper, an attempt is made to perform non-linear modeling of the plasma arc welding (PAW) of Inconel 617 plates with the help of experiments conducted using a central composite design of experiments (CCD). It is to be noted that the PAW is a high depth to width ratio welding process that can be used to join high strength materials like Inconel 617. Furthermore, mechanical properties such as ultimate tensile strength (UTS), percentage of elongation, flexural strength and hardness of the welded joints are highly dependent on the conditions under which the welding is performed. In the present paper, the weld current, weld speed and plasma gas flow rate of PAW are considered as input process parameters to study the effect of these variables on the above mentioned mechanical properties. Industrial pure argon (99.99 %) is used as both plasma and shielding gas during the welding of the 2 mm thick Inconel 617 plates. Surface plots and analysis of variance (ANOVA) are used to test the statistical adequacy of the models. Moreover, the prediction accuracy of the models is tested with the help of experimental test cases and found to be in good agreement.

An aluminum alloy 8011 was reinforced with varying weight percentages of TiB 2 using an in situ stir casting technique by adding inorganic halide salts of K 2 TiF 6 and KBF 4 in molten AA8011 matrix alloy. X-ray diffraction and scanning electron microscopy were performed on the cast materials to confirm the presence and distribution of the reinforcements in the composite materials. To investigate the wear behavior of the cast materials, pin on disc wear testing was carried out at varied levels of sliding distance, amount of reinforcement, temperature, load and sliding velocity based on Taguchi's L18 orthogonal array with wear rate as the response. AA 8011 with a reinforcement of 4 wt.-%, 1500 m sliding distance, at a temperature of 100 °C, load 10 N and sliding velocity 2 m × s −1 provided the best wear resistance. The significance and influence of factors on wear rate were analyzed by an analysis of the variance.

In this study, the surface of AZ91D magnesium alloy was coated with ZrO 2 –wt.-% 22 MgO by the plasma spray method. The coatings were made at two different current levels (600 and 500 A) and three different spraying distances (120, 130 and 140 mm). The surface roughness was measured by a profilometer and hardness was measured via a microhardness test. Coated cross-sections were examined under an optical microscope (OM) and scanning electron microscope (SEM). The phases formed on the coating surfaces were detected by x-ray diffractometer (XRD). A dry sliding wear test was performed at 5, 7.5 and 10 N normal loads. Mg 2 Zr 5 O 12 , ZrO 2 , MgO, and Zr formed on the coating layers. Surface roughness and porosity percentages were enhanced by increasing the spray distance and decreasing current. The maximum microhardness value was reached at 1152 (HV 0.1 ), and significant improvements were observed in the wear resistance of the coatings compared with that of the AZ91D. An extreme learning machine (ELM) algorithm, which is one of the machine learning algorithms, was applied to the wear loss data obtained. The success rate for the model designed using the ELM algorithm, was calculated as 0.9287 (R-squared).

Fitting products of different dimensions and design geometries are used in natural gas pipelines, water supply systems, fire installations, machinery equipment and in the aviation and automotive industries. This study aims to investigate the machinability of Al 6061-T6 fittings, which are widely used in the aerospace and automotive industries. In an endeavor to produce reliable and healthy installation systems, Al 6061 material was reinforced with 10 % copper and 316L stainless steel powder in order to increase its corrosion resistance and improve its mechanical properties for sustainable production. These new materials were threaded using a ½ BSP (British Standard Pipe) tap tool via the Taguchi L 9 method. Different materials, heat treatments and spindle speeds were used during this manufacturing process. The effects of these manufacturing parameters on the total power dissipated P total were calculated using variance analysis (ANOVA). According to these results, the most effective parameter was the heat treatment type (44.9 %), followed by the material type (30.6 %) and the rpm (19.9 %). It was observed that these aluminum materials can be threaded using 30 to 40 % lower energy consumption compared to cast iron. In addition, the aluminum alloy fitting materials achieved higher hardness than the cast iron fittings.

Environmental friendly natural fibers have been used instead of petroleum-based synthetic fibers as reinforcements because of the depletion of oil resources, plastic waste disposal problems and the emissions generated during combustion. In these natural fibers, thermoplastic or thermoset materials are used as matrix material because of their low cost, light weight and durability. In this study, the effects of ply number (2 and 3 layer) and orientation angle of reinforcement (0/90° and ± 45°) and matrix type (thermoset and thermoplastic) on the tensile strength of jute reinforced composites were investigated. Also, the effect of the reinforcement orientation angle, sliding time (600, 1200 and 1800 s) and applied load (5, 10 and 15 N) on tribological characteristics were determined. Adhesive and abrasion wear tests were carried out at 0.15 m × s −1 sliding speed. It was observed that the matrix material and the reinforcement are very important in tensile and wear tests, while the ply number and the orientation angle only exert an influence in the tensile strength of composites. It was determined that an increase in load and sliding time is the most effective parameter on wear experiments.