Band 66, Heft 9

In brazing processes, the formation of defects within the brazing joint due to deviations in brazing process and material is a recurring problem. These affect the component quality as well as the component properties. In this study, modal analysis is fundamentally investigated as a potential tool for non-destructive testing of brazing joints as well as for fast quantification of the precision of the brazing process. The aim of the investigation is to detect defects in brazed components. For this purpose, test specimens in defect-free and defect-containing form are brazed by means of a high-vacuum furnace. The subsequent recording and real-time analysis of the oscillation behavior of these test specimens is to be used to evaluate the quality of these brazed joints. A method, developed specifically for this purpose, automatically evaluates the recorded oscillation profile based on several defined frequency positions. For the first time, the results show that a reproducible classification of brazing seam quality into OK and not-OK can be made by comparing several frequency positions with already known oscillation profiles.

This study develops a 3D model of a Christmas tree using cathodic protection technology and conducts numerical simulations on the Q355ND framework of a shallow Christmas tree. The boundary element method is employed for modeling, examining the distribution of protection potentials under varying corrosion layer breakage rates, anode numbers, and positions. The influence of sacrificial anode parameters on the cathodic protection effect of the Christmas tree is also investigated. The findings reveal that when the breakage rate of the anticorrosion layer reaches 35 % during Christmas tree operation, the sacrificial anode fails to provide complete protection. However, if the coating breakage rate is 10 %, reducing the number of anodes by six can still achieve a protection potential of −850 mV. Thus, it is imperative for Christmas trees to maintain a corrosion protection layer breakage rate below 35 %. Beyond this threshold, sacrificial anodes exhibit minimal effectiveness in preserving their integrity.

AZ31B magnesium alloy plates were lap-joined to AISI 304 stainless steel plates through the friction stir welding (FSW) method and utilizing various tool welding speeds. It has been found that the most important factor governing the weld strength is the hook formed on the advancing side of the welds. The weld tensile shear strength improved with an increase in the tool feed rate. Because, in general, height, length, and width of the hook taking place on the advancing side shrunk. Furthermore, the angle between the hook and interface of the plates increased, leading to reduced sharp corner formation. Apart from these, imperfections such as cavities, voids, and uncombined regions at the weld interface reduced and disappeared when increasing the welding speed. During the tensile shear test, all the welds fractured tensile mode and brittle type from the top AZ31B plate next to the hook on the advancing side. There was no breakage occurred in the weld interface, which is an indication of the strong joints. No intermetallic compounds between iron and magnesium were determined at the fracture region. At lower welding speeds, a higher amount of AISI 304 particles occurred at the weld stir zone resulting in a higher hardness.

The primary objective of this study is to analyze the effect of double pulse tungsten inert gas (DP-TIG) welding on microstructure and mechanical properties of super austenitic SMO 254 stainless steel joints. The butt joints of SMO 254 steel were made using ERNiCrMo-10 filler metal. The microstructural characteristics of different regions of joint were analyzed using optical microscope, scanning electron microscope, X-ray diffraction analysis, and energy dispersive spectroscopy. The micrograph of weld metal showed finer equiaxed grains at the middle of weld metal and columnar grains near the weld interface. The SMO 254 steel joints showed the tensile strength of 636 MPa, ductility of 35 %, and impact toughness of 52 J. The fractured surfaces showed ductile mode of failure of joints.

In this study, numerical and experimental analysis of impact performances of cast polymethyl methacrylate (CPMMA) and stretched polymethyl methacrylate (SPMMA) panels were conducted. First, the material characterization tests (tensile and compression tests as well as split Hopkinson pressure bar tests) of CPMMA and SPMMA materials were performed to determine the Johnson–Cook material model parameters to be used in the finite element models. Next, impact tests were performed for CPMMA and SPMMA panels. The velocity of the impactor before and after penetration was measured and the deformation patterns are recorded. Then, finite element models were generated using LS-DYNA to simulate the impact tests. Finally, the impact performances of the CPMMA and SPMMA panels were compared. It is found that CPMMA has better impact performance than SPMMA for the impact velocities investigated in this study.

In this study, Sr inoculated A356 alloy casted by sand-casting technique. Production parameters such as Sr concentration (wt.%), aging temperature (°C), aging time (h), and constant cooling rate were used. The effect of heat treatment on the microstructure and mechanical features of inoculated A356 materials was examined by using scanning electron microscopy, optical microscopy, and the Taguchi-based gray relational analysis method. The optimum production parameters for A356 alloy were determined as 0.03 Sr concentration, aging 300 °C temperature, and 3 h aging time. Multiple response optimization based on the interaction of these parameters provided a 30.15 % improvement in performance. Gray relational grade (GRG) experimental results showed that the most important parameter was Sr concentration, with a contribution of 76.51 %, according to the analysis by ANOVA statistical method.

Under low laser power conditions, the cladding layer is constrained by inadequate energy density, resulting in incomplete melting of certain powder particles and the occurrence of defects such as cracks and pores within the layer. This paper utilizes a QT500 substrate and synergistically integrates high-reactivity energetic materials (H-REMs) with metal powder. By external laser energy ignition, the localized combustion of the H-REMs (Al + Fe 2 O 3 ) is induced, thereby providing additional heat input during the laser cladding process. Through in-depth analysis of extensive experimental data, the influence of H-REMson microstructure and performance of alloy cladding layerhas beenrevealed. The research results demonstrate that the inclusion of H-REMs leads to a 450 K increase in the maximum temperature of the molten pool. By incorporating high-reactivity energetic materials, the energy density utilization of the composite material increased from 0.2663 to 0.7375. The combustion wave generated by H-REMs induces mixing in the molten pool, resulting in cladding layer grain refinement and an average hardness increase of 80 HV 1 . The friction coefficient decreases from 0.71024 (prior to the addition of H-REMs) to 0.35809, representing a reduction of approximately 49 %.

This work investigates the hyper-viscoelastic behavior of a thermoplastic polyurethane IROGRAN A 92 E 5670 FCM used in the gear rim of a jaw coupling. The aim is to provide the material parameters for the modeling of jaw couplings in engineering tasks. Uniaxial compression tests were conducted at various temperatures and loading speeds to fit a hyper-viscoelastic material model. The material model uses the Yeoh free energy and the power law model with one Maxwell element. The parametrized material model showed very good results in comparison to experimental data. In addition, the influence of friction on the experiments was modeled, investigated, and discussed. Further component tests for a jaw coupling of size 28 were conducted with two different specimen types. The original gear rim and a modified gear rim with central boreholes for integrated sensors were used in the test. The influence of such a modification was investigated with four different loading cases, focusing on the torsion-torque characteristic and the relative damping. These component tests enable the validation of numerical models of jaw couplings.

Optimization techniques play a pivotal role in enhancing the performance of engineering components across various real-world applications. Traditional optimization methods are often augmented with exploitation-boosting techniques due to their inherent limitations. Recently, nature-inspired algorithms, known as metaheuristics (MHs), have emerged as efficient tools for solving complex optimization problems. However, these algorithms face challenges such as imbalance between exploration and exploitation phases, slow convergence, and local optima. Modifications incorporating oppositional techniques, hybridization, chaotic maps, and levy flights have been introduced to address these issues. This article explores the application of the recently developed crayfish optimization algorithm (COA), assisted by artificial neural networks (ANN), for engineering design optimization. The COA, inspired by crayfish foraging and migration behaviors, incorporates temperature-dependent strategies to balance exploration and exploitation phases. Additionally, ANN augmentation enhances the algorithm’s performance and accuracy. The COA method optimizes various engineering components, including cantilever beams, hydrostatic thrust bearings, three-bar trusses, diaphragm springs, and vehicle suspension systems. Results demonstrate the effectiveness of the COA in achieving superior optimization solutions compared to other algorithms, emphasizing its potential for diverse engineering applications.

This study introduces a novel metaheuristic algorithm of optimization named Chaotic Artificial Rabbits Optimization (CARO) algorithm for resolving engineering design problems. In the newly introduced CARO algorithm, ten different chaotic maps are used with the recently presented Artificial Rabbits Optimization (ARO) algorithm to manage its parameters, eventually leading to an improved exploration and exploitation of the search. The CARO algorithm and familiar metaheuristic competitor algorithms were experimented on renowned five mechanical engineering problems of design, in brief; pressure vessel design, rolling element bearing design, tension/compression spring design, cantilever beam design and gear train design. The results indicate that the CARO is an outstanding algorithm compared with the familiar metaheuristic algorithms, and equipped with the best-optimized parameters with the minimal deviation in each case study. Metaheuristic algorithms are utilized to succeed in an optimal design in engineering problems targeting to achieve lightweight designs. In this present study, the optimum design of a vehicle brake pedal piece was achieved through topology and shape optimization methods. The brake pedal optimization problem in terms of the mass minimization is solved properly by using the CARO algorithm in comparison to familiar metaheuristic algorithms in the literature. Consequently, results indicate that the CARO algorithm can be effectively utilized in the optimal design of engineering problems.

Nowadays, laser welding is a powerful joining method. Thanks to the advantages it has, its usage area is increasing day by day. However, getting the desired result from the laser welding process is possible with the proper welding parameter selections. Otherwise, many problems may be encountered, including significantly incomplete penetration. For this reason, parameter selection has been discussed in many studies in the literature. At this point, validated numerical simulation models are precious. Since these models reduce experiment costs and save time. Especially numerical simulation of the structural steel, which is the one of most used materials, is crucial. In this study, the effects of laser power (LP) and welding speed (WS), which are among the vital parameters of laser welding, on weld width and stress were investigated numerically and statistically. Structural steel was selected as the material, and the Taguchi method was carried out for the simulation case study design. Simufact Welding software was used for simulation studies, and simulations were carried out thermomechanical. Thus, more realistic results were obtained via the thermomechanical method. One of the simulation results was verified through an experimental study. The results were evaluated with signal-to-noise (S/N) ratio and a statistical analysis of variance (ANOVA), and as a result of the study, it was seen that the welding speed was a more effective parameter, the optimal parameter combination was found to be 3500 W for laser power and 40 mm/s for welding speed to get maximum weld width and minimum equivalent stress. In addition, it was observed that correctly created simulation studies may provide very close results to experimental studies.

This work presents the influence of betel nut fiber hybridization on the properties (mechanical, thermal, wear, and water absorption) of novel aloevera fiber-reinforced vinyl ester composites. In this research, we fabricated the composites by changing the wt.% of aloevera fiber and betel nut fiber through the hand layup method using the compression molding technique. From the results, it has been observed that increases in wt.% of betel nut fiber increased the mechanical properties, thermal properties, wear resistance, and water resistance of the composites. The composite with the designation S1 shows the lowest hardness, tensile, flexural, impact, and shear strengths of 49.58, 26.59 MPa, 52.53 MPa, 4.12 J, and 101.26 MPa, respectively. Meanwhile, the composite with the designation S5 shows the highest hardness, tensile, flexural, impact, and shear strengths of 71.29, 62.61 MPa, 78.24 MPa, 9.57 J, and 139.52 MPa, respectively. Further, higher wear resistance and water resistance were obtained by the S5 specimen. SEM analysis shows the good strength of betel nut fiber and enhances the tensile strength of the composites.

In this study, the EDM machining performance of a cryogenic heat treated copper electrode was investigated. Within the scope of the study, electrodes selected from copper material were subjected to cryogenic heat treatment with a cycle between [room temperature/ − 184 °C/room temperature]. In the experimental design, the electrode material was changed at two levels: copper electrode (Cu) and cryogenic copper electrode (CCu). Controllable machine parameters, peak current (Ip), active pulse duration (Ton), pulse gap duration (Toff) and gap voltage (Vg) were changed at three levels. The effects of these parameters on outputs such as recast layer thickness (RLT), material removal rate (MRR), electrode wear rate (EWR) and taper angle (TA), which are taken into consideration in determining the processing quality after EDM machining experiments, were taken into account. A total of 18 experiments were carried out on Ti–6Al–4V (Titanium alloy) workpiece with copper electrode. Lower YKTK with combinations of EDM process parameters such as cryogenic copper electrode (CCu), 4 A peak current (Ip), 110 µs active pulse duration (Ton), 72 µs pulse gap time (Toff) and 6 V gap voltage (Vg), It was observed that EWR and TA and higher MRR were obtained.

The primary aim of this study is to analyze the influence of inter-pulse tungsten inert gas (IP-TIG) welding parameters (peak current, inter-pulse current, and inter-pulse frequency) on weld bead geometry, tensile properties, and microstructure of Ti6Al4V alloy joints for gas turbine applications. IP-TIG welding principally featured by magnetic arc constriction and pulsing was employed to overcome the high heat input problems in TIG welding of thin Ti6Al4V alloy sheets such as wider bead and HAZ, coarsening of beta grains, inferior ductility, distortion of joints, and atmospheric contamination which significantly deteriorates the mechanical performance of welded sheets. The tensile properties and microhardness of IP-TIG joints were evaluated and correlated to the microstructural features. The microstructural features were analyzed using optical microscopy. The fractured surfaces of tensile specimens were studied using scanning electron microscopy. Results showed that the Ti6Al4V alloy joints developed using peak current of 50 A, inter-pulse current of 30 A, and inter-pulse frequency of 20 kHz exhibited greater strength, hardness and elongation. It showed greater tensile strength of 1030 MPa, yield strength of 981 MPa, and elongation of 10 % and FZ microhardness of 391 HV 0.2 . It is mainly due to the development of refined grains in fusion zone (FZ).

In this study, a novel multi-cell crash box was designed and produced using 15 % short carbon fiber reinforced polyethylene terephthalate (CF15PET), polylactic acid (PLA), and acrylonitrile butadiene styrene (ABS) filaments using one of the additive manufacturing methods, the melt deposition method (FDM). All structures’ maximum force and energy absorption performances have been investigated. As a result of the test, it was determined that the crash box, which best meets the high energy absorption and folding properties, one of the expected features in crash boxes, has parts manufactured using ABS and CF15PET materials. According to the test result, it was found that the energy absorption of the ABS crash box is 11 % higher than CF15PET and approximately 4.5 % higher than PLA. It has been determined that the maximum force response value of the ABS box is 5 % higher than CF15PET and 12 % higher than PLA. As a result, it has been determined that ABS and CF15PET materials can be used in crash boxes and can form an idea about the design and test result by designing and analyzing crash boxes using finite element programs.

The main objective of this study is to develop the Kevlar fibre reinforced Onyx composite (KFRO) material by employing the 3D printing technology and examine the effect of Kevlar fibre reinforcement percentage on microstructural characteristics and mechanical properties of developed composite material. The methodology of continuous fibre reinforced composites (CFRC) was followed and the Kevlar fibre reinforcement % was varied as 10 %, 20 % and 30 % in the composite material fabrication. Results disclosed that the KFRO composite 3D printed using 30 % Kevlar fibre reinforcement in Onyx matrix yielded greater tensile strength of 124 MPa, flexural strength of 105 MPa, impact toughness of 2.4 J and shore hardness of 76 D. The mechanical properties of KFRO composite were significantly improved at 20 % of Kevlar fibre reinforcement compared to 10 % of Kevlar fibre reinforcement. Further increase in Kevlar fibre reinforcement up to 30 % showed slight enhancement in mechanical properties of KFRO composite when compared to 20 % of Kevlar fibre reinforcement. The overall strength improvement is a result of the increased reinforcement, precise alignment of fibres in the loading direction, and the uniform distribution of fibres within the onyx.

In this paper, the welding quality of API 5L X60 steel pipes was investigated after the application of three different welding scenarios by applying submerged arc welding (SMAW), tungsten inert gas (TIG) and hybrid (TIG + SMAW) welding methods with an average heat input of ca. 1 kJ mm −1 for all passes. For this purpose, the ultrasonic and radiographic tests were done to detect possible discontinuities such as crack and porosity in the welding zones. In addition, the macro and microstructures of weld zones were made to examine different zones in terms of weld quality and phases. Moreover, the hardness, impact toughness and tensile tests were carried out to determine the mechanical properties of the weldments. The tensile strength of the pipe weldments was recorded to be ∼603, 610 and 625 MPa after the welding of pipes by SMAW, TIG + SMAW and TIG welding, respectively. In addition, the impact toughness of the welds was obtained to be 48, 76 and 66 J, for these welding methods, successively. According to the experimental findings, all three welding plans were successfully applied to the steel pipes and found to be suitable regarding the relevant international standards.