Volume 67, Issue 8

When testing double cantilever beam (DCB) specimens, the distance between the load line and the crack tip corresponds to the lever arm, thereby affecting the load necessary to propagate the crack. While ASTM D5528 defines an initial delamination length (IDL) from this load line to the end of the inserted release film, there is no such specification in DIN EN 6033. The question, therefore, arises as to whether the IDL affects the interlaminar fracture toughness energy – Mode I – G IC determined from DCB specimens. This is especially important to know for the positioning and application of the hinges. In the present work, the influence of two different IDL (5 and 20 mm) on the G IC of vacuum-infused quasi-unidirectional glass fiber reinforced plastic is studied according to DIN EN 6033. It is shown that there are significant differences in the load–displacement curves. After evaluation, however, the results of the two series are quite comparable because the differences even out in the course of the tests.

The purpose of this research is to examine the absorbed energy, resistance to impact load of sandwich composite, and power exercised by impactor, experimentally. Therefore, low velocity impact tests were performed at three different energy levels for two distinct noses on sandwich composite with a PVC core and varying amounts of S2-glass layers. The vacuum-assisted resin infusion method (VARIM) was used to manufacture sandwich composites. S2-glass fabric with an areal density of 190 gm −2 and polyvinyl chloride (PVC) core material with a thickness of 10 mm were utilized. For every face sheet material, three distinct layer numbers of S2-glass fabrics were used. It is seen that composites exposed to flat impactors absorb considerably more energy than hemispherical ones.

Cold deformation behavior and microscopic mechanisms of L605 centrifugal cast tubes were studied via room-temperature compression tests. The hardening behavior aligned well with the Hollomon equation, and a high-fidelity cold deformation constitutive relationship was determined using least-squares fitting in Matlab. Increasing cold deformation intensified grain distortion, promoted grain uniformity, and transformed the original columnar grains into elongated strip shapes. During deformation, twin boundaries with an orientation deviation of 60° remained at 1–4 %, whereas low-angle grain boundaries rose markedly, and high-angle grain boundaries declined. At 15 % compression, numerous dislocations were observed within stacking faults, along with SMIT processes. Upon further compression to 30 %, abundant stacking fault intersections emerged, and a geometric model yielded a dislocation motion resistance of 0.784  N  m −1 . Subsequent annealing of compressed specimens at 1,100 °C for 30 min unveiled abundant Σ3 (60°⟨111⟩) annealing twin boundaries, demonstrating an inverse relationship between deformation level and annealed grain size. Microscopic M 6 C carbides were trapped at interfaces between annealing twin boundaries and grain boundaries. Additionally, stacking faults arranged in orderly, parallel arrays on annealing twin surfaces, hindering the γ -to-ε phase transition.

Rod ends used in automotive industry are the utmost important elements that play a critical role in suspension system and steering devices. They are exposed to high sudden forces in both axial and radial directions and so the life performance is one of the big challenge for the manufacturers. In this study, the effect of design parameters on increasing the fatigue life of rod ends was investigated. Existing rod ends were subjected to fatigue tests under ±40 kN, ±50 kN and ±70 kN loading. The analysis and test results showed that the fatigue life of the existing design was low and the damage generally started in areas with sharp corners or low radii. Thus, a new road end design was proposed and thanks to the optimized new design, the fatigue life of rod ends was increased from 135,310 cycles to 884,043 cycles on average under ±50 kN load. The obtained results show that the improvement of the sharp corners and radius of the road end enhance the fatigue performance significantly, which is very important for the manufacturers and designers in the automotive steering mechanisms.

Pipe is a critical component of the drag link of automotive transmission systems. It keeps together ball joints after shrinking process. It is usually made of St52 alloy. A hardening rule is employed to represent the shrinking process accurately. It constitutes both bilinear isotropic model and Chaboche’s nonlinear kinematic model. Raw parameters are estimated through a nonlinear regression and data from uniaxial tensile and low cycle fatigue (LCF) test. For their calibration, an inverse analysis based on optimization is employed by means of genetic algorithm, screening, non-linear programming, and quadratic programming techniques. The novelty of this study is that the parameters for the shrinking process are acquired using only the data obtained from tensile and LCF tests. The force requirement, spring-back, and material flow path are also calculated. An insight is gained into the hardening model, its parameters, and their sensitivity for the shrinking process. The calibrated parameters are TM  = 10.03 MPa, YS  = 290.68 MPa, C 1  = 3,405.89 MPa, γ 1  = 39.62, C 2  = 3,486.45 MPa, γ 2  = 39.62, C 3  = 3,785.67 MPa, γ 3  = 39.62 where YS is yield strength, TM is tangent modulus, C is hardening modulus, and γ is decrease rate. Absolute relative error is 0.1 %.

In this study, 6061 T6 aluminum alloy (AlMg1SiCu) was welded using the laser welding method with E Al 4043 (AlSi 5) filler wire. The shielding gas composition and welding parameters were varied, and the joints were welded at different welding speeds. The metallurgical and mechanical properties of the welded joints were analyzed. The results showed that joints welded at the highest speed of 35 m s −1 exhibited the highest tensile strength. Furthermore, it was observed that as the amount of helium in the shielding gas composition increased, the number of pores in the weld seam decreased, while the weld seam width increased.

Due to their advantages, bolted connections are irreplaceable in machine, plant, and vehicle construction. High-strength bolts can be subjected to (high) dynamic loads during operation. Unfortunately, the knowledge of the strain rate dependence of the mechanical properties of high-strength bolts is very limited. Therefore, tensile tests were carried out at 11 different strain rates between 0.001 and 30 s −1 on high-strength bolts of size M6 of strength class 8.8. In addition, notch-free tensile specimens were manufactured from the bolts and also loaded at different strain rates in order to quantify the influence of the thread on the mechanical properties of the material. The tensile tests were analyzed in terms of yield strength, ultimate tensile strength, elongation at fracture, and energy absorption capacity. For this purpose, a test setup was developed and manufactured on which the bolts were axially loaded until fracture. It was found that the tensile strength and yield strength of bolts only increase above a certain strain rate. The elongation at fracture of complete bolts and also unnotched specimens is independent of the strain rate. For unnotched specimens, both the strength is dependent on the strain rate over the investigated strain rate range.

Current efforts in additive manufacturing commonly use magnesium alloys because of their numerous advantages. Despite these, the performance of magnesium at high temperatures often limits operational conditions. This study investigates the high–temperature performance of the additively manufactured WE43 magnesium alloy, with a particular focus on its creep behavior under quasistatic and cyclic compression loading at elevated temperatures. The results show that manufacturing–related defects result in reduced creep resistance and affect the fatigue capability.

In this work, a novel approach for a wear testing is investigated using a spherical, diamond-coated mounted point in a pin-on-disk tribometer to simulate two-body abrasion. The procedure establishes a new type of testing method for simulating abrasive wear with particularly harsh conditions. For validation, tests were conducted on both quenched and tempered as well as on additionally nitrided samples made of 16MnCr5. The design of the experiments is based on the ASTM G99-17 standard for pin-on-disk tests. A characteristic wear track is produced, which is formed by the recurring influence of the diamond wear particles. Due to the shape of the wear track, it is necessary to use a modified approach for evaluating the tests compared to the standard. The main focus of this work is on the effect of the aggressive abrasive grinding tool on hard surface layers and the repeatability of the test results. It is demonstrated that under the same test conditions, the heat treatment conditions of the samples can be clearly and repeatedly distinguished based on the wear curves. Due to the highly abrasive effect, the method is suitable for investigating procedures to enhance the surface hardness or wear resistance of surfaces.

Stainless steel 304 is the commonly utilized grade within the 300 series in various industries. Welding is a prevalent technique for producing stainless steel structures. In this study, 5 mm thick AISI 304 sheets were joined by plasma welding. The joint interface was detected using energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), elemental mapping, X-ray diffraction (XRD), and microhardness. The mechanical properties of the bonded samples were evaluated by tensile testing. The fracture morphologies of the tensile test samples were examined. In single-pass plasma welding, perfect welds with full penetration were achieved. Both ultimate tensile strength (UTS) and elongation percentage increased with the rise in welding current.

In this study, trials of disc brake pads, which have different compositions and are used in the front brake systems of trucks, were carried out by SAE-J 661 (Brake Lining Quality Test Procedure), SAE-J 866 (Friction Coefficient Identification and Environmental Marking System for Brake Linings), and SAE-J 2975 (Measurement of Copper and Other Elements in Brake Friction Materials) standards. As a result of the experiments, the superiorities or weaknesses of the brake pads relative to each other were evaluated. In the experimental studies, first, EDS (energy dispersive spectroscopy) analyses were carried out with the help of scanning electron microscopy (SEM) and XRF (X-ray fluorescence) analyses to determine the compositions of three different disk brake pads. After the brake pad compositions were determined, friction-wear tests were carried out following the standards. Apart from these, TG (thermogravimetric) analyses, hardness, density, and internal shear strength measurements were carried out.

In this study, the friction and sliding behaviors of Polyetheretherketon (Peek) and Ultra-high-molecular-weight polyethylene (Uhmwpe) polymers when sliding against different counterfaces unreinforced Polyethylenimine (Ur-Pei), 20 vol.% glass fiber reinforced Pei polymer (20 vol.% Gf + Pei), wear durable Pei polymer (Dw-Pei), and stainless steel (Aisi 304L Ss) were determined and compared. Additionally, the tribological behaviors of these two polymers used in the industry were tested using the Taguchi optimization method. Mathematical equations were created using the regression method for optimal friction coefficient and specific wear rate. Accordingly, the optimal friction coefficient was obtained when Uhmwpe polymer was slid against Ur-Pei counterface with a 10 N application load. In contrast, the optimal specific wear rate was determined under 20 N load test conditions for Uhmwpe polymer against Ur-Pei counterface.

Advanced high-strength steels (AHSS) are increasingly used in the automotive industry for lightweight components due to their superior mechanical properties. Quench and partitioning (QP) steels provide an optimal balance between strength and formability, but their susceptibility to liquid metal embrittlement (LME) during resistance spot welding presents challenges. Laser welding, with its low heat input and high efficiency, offers a promising solution for reducing LME risks while ensuring strong, reliable joints for automotive applications. This study investigates the microstructural changes and mechanical performance of laser-welded joints between QP and dual phase (DP) steels. The fusion zone (FZ) and supercritical heat-affected zone (HAZ) primarily exhibited martensitic microstructures, while the midcritical and subcritical HAZ contained tempered martensite and ferrite on the DP side and a combination of tempered martensite, ferrite, and retained austenite on the QP side. These microstructural transformations contributed to enhanced FZ and HAZ regions, resulting in defect-free welds. Fractures occurred within the softer base metal (BM) regions, exhibiting ductile fracture characteristics without significant strength loss. However, joint ductility was slightly reduced compared to BMs due to strain localization caused by microstructure and thickness variations. The results demonstrate that laser welding is an effective method for joining QP steels in automotive manufacturing.

Optimizing real-world engineering design challenges is inherently complex and difficult, especially when optimal solutions are expected. To this end, the creation of new and efficient optimization algorithms is not an option but a necessity. This paper presents an improved version of the recently developed Polar fox optimization technique. The addition of dynamic adversarial learning improves the dynamic adversarial learning Polar fox optimization algorithm by improving the performance of the algorithm to optimize real-world optimization problems not only very quickly but also accurately. Using test problems from the field of engineering disciplines, such as car crash test, welded beam structure, three-bar truss, and cantilever beam problem, the new optimizer known as the modified Polar fox optimization algorithm (MPROA) was validated before being used to optimize an automobile suspension arm. MPROA achieved superior results in achieving the goal quickly and accurately and proved its potential to solve complex engineering problems. Moreover, the comparison will also reveal the power of the MPROA developed in this work to tackle multiple issues that constrained the reach of a globally optimal solution.

Polymer composites are structural materials created by incorporating fillers into polymer matrices. The tensile and hardness properties of polymer composites are important for their functioning in structural applications. Incorporating co-fillers into polymer composites has emerged as an alternative strategy for improving their mechanical properties further than the capabilities of the single filler system. In this concise review, various co-fillers, primary fillers, and polymer matrices employed in polymer composites are classified. In addition, the effects of co-fillers on the tensile and hardness properties of polymer composites are briefly described. This review provides succinct insights that increase the comprehension of tensile and hardness properties in polymer composites containing co-fillers. In short, numerous investigations demonstrate that incorporating co-fillers improves the tensile and hardness properties of polymer composites. This improvement is attributed to co-fillers (whether inorganic-, organic-, or carbon-based materials) enhancing the strength, stiffness, flexibility, and hardness of various polymer composites, including elastomer, thermoplastic, and thermoset composites.