International Journal of Lightweight Materials and Manufacture最新文献

Three-layer aluminum/polymer/aluminum composite sheets are among the new materials developed to reduce the weight and fuel consumption of vehicles. Using the conventional methods for joining these materials to other materials is challenging. In this paper, the joinability of the three-layer aluminum/polymer/aluminum to a single-layer 1 mm-thickness aluminum sheet, in the clinching process is investigated. Three-layer sheets of AA5754/polyethylene/AA5754 with thicknesses of 0.5/0.6/0.5 mm were produced under laboratory conditions using two different methods; with and without a local reinforcement piece in the polymer core. The prepared specimens are joined using various geometric parameters of the clinching tools. The joint sections and their geometric parameters including interlock and neck thickness are evaluated in different joint conditions. Also, the strengths of the joints are examined by shear and peel tests. Studies show that it is possible to use the clinching process to join aluminum/polymer/aluminum sheets. Also, with a proper design of tools, the joint strength can be in the same order as the strength of the clinching of single-layer sheets. The maximum shear and peel test strengths, obtained in this study are 1288 N and 540 N, respectively. Increasing the pin penetration depth increases the interlock up to an optimal value. However, further increases in the pin penetration depth will decrease the neck thickness and joint strength. The conical angle of the pin, increasing the die cavity depth, and using a local reinforcement piece reduces the strength of the clinched joint and interlock in these materials. In all the test conditions, the most suitable joint conditions were when the failure mode was combined bottom separation and neck fracture mode.

The article presents the results of research that make it possible to solve a significant scientific problem associated with the creation of new technologies for processing hard-to-deform aluminum-silicon alloys. For this purpose, tasks were set and solved for the development of technological schemes for obtaining longish products from AlSi12 and AlSi5 alloys using the methods of electromagnetic crystallization ingots of a small cross-section and the manufacture of deformed semi-finished products in the form of rods and wire using the method of combined rolling-extrusion (CRE) and drawing. To solve these problems, the modeling of the CRE process, theoretical and experimental studies were carried out, the results of which made it possible to obtain pilot batches of welding wire from the AlSi12 alloy, the level of properties of which meets the requirements of current standards. To analyze the combined rolling-extrusion, modeling was carried out using the DEFORM 3D software package. Regularities were established for changing the temperature-rate and force parameters of this process along the deformation zone. Since the use of the proposed technological scheme for the combined processing of aluminum-silicon alloys leads to a decrease in labor intensity and production costs, it can be recommended for use in industry to obtain longish products from them.

Three polymeric materials; polystyrene (amorphous), low-density polyethylene (semi-crystalline), and poly(methyl methacrylate) (amorphous) were used to explore their behavior and properties during processing using a co-rotating twin-screw extruder. Injection molding and compression molding were used for preparing the test specimens. Screw speed and barrel set temperatures were considered as the main processing variables while observing the process energy consumption of the extruder. The tensile, thermal, and rheological properties of the extruded materials under different processing conditions were evaluated. Test results confirmed that the motor power of the extruder for processing polystyrene and low-density polyethylene increased with increasing screw speed and decreased with increasing barrel set temperatures. Motor power for processing poly(methyl methacrylate) increased significantly with increasing screw speed. The total power consumption of the barrel heaters for processing polystyrene and low-density polyethylene slightly increased with the barrel set temperatures. The tensile modulus of polystyrene decreased with increasing screw speed at higher barrel set temperatures, while low-density polyethylene showed no significant variation. The tensile modulus of poly(methyl methacrylate) did not exhibit a clear trend with the extruder process settings. The effect of process settings on the glass transition temperature and melting temperature of the polymers was not significant, and no evidence was found of any molecular degradation during processing. Rheological properties of poly(methyl methacrylate) showed a significant variation with increasing screw speed and barrel set temperatures, while those of polystyrene and low-density polyethylene did not exhibit a consistent variation.

The establishment of deformation mechanisms of Mg-metal matrix composite (Mg-MMC) is important to improve the high-temperature challenging applications. In this present work, an AZ91/TiC + TiB₂ hybrid in-situ Mg-MMC was synthesized, and its deformation mechanisms were studied through a uniaxial hot compressive test at different temperatures and strain rates. The Johnson-Cook (JC) model and constitutive equation were established using experimental stress-strain data. Through the development of JC model, it was revealed that the TiC–TiB₂ particles enhanced the yield strength parameter and increased the activation energy of the in-situ composite compared to the parent alloy. The load-shifting capability and grain refinement were found to be the dominating mechanisms, which effectively restricted dislocation movement during deformation, resulting in improved deformation resilience of the composite. A detailed study of JC model and constitutive equation parameters was analyzed with a focus on their microstructures.

Industrial heat exchanger applications dealing with highly corrosive fluids demand the use of thermoplastic heat exchangers because of the chemically inert and anti-fouling nature of the thermoplastics. A non-conventional joining framework, based on the friction stir welding (FSW) technique, is used to form high-quality thermoplastic tube-to-tubesheet joints (TTJs). The proposed technique has potential applications for thermoplastic shell-and-tube heat exchangers and piping industries (as flange-to-pipe joints). In this work, the tube and tubesheet materials made of carbon black reinforced high-density polyethylene were used. The effect of different FSW parameters (rotational speed, plunge depth, tube protrusion, dwell time) on the tube pull-out behavior was investigated. The FSW technique showed capabilities at a wide range of operating conditions. The highest load bearing capacity of 517 N was achieved using the FSW process, much higher than adhesive joints. Also, it provides higher extensions at maximum load than adhesive joints, with the highest extension of 5.161 mm. Two FSW cases provided high leak paths of 77% and 58% remaining sheet thickness (greater than tube thickness) along with high load bearing capacity and corresponding extensions. The macroscopic and SEM-based fractographic studies illustrated three types of failure behavior: ductile, brittle, or mixed depending on the FSW process conditions. The DSC results showed no significant crystallinity changes in the weld material. The TGA results showed no significant thermal degradation occurring in the weld material. Further, the FTIR analysis indicated possible oxidation of the weld material. The capability to form TTJs with high leak path, high load bearing capacity, and no significant material degradations makes the FSW technique suitable for thermoplastic shell-and-tube heat exchanger applications.

Fiber metal laminates (FMLs) are a kind of composite material prepared by alternately arranging fiber layers and metal sheets at a certain temperature and pressure. It has been widely used in aerospace and automobile transportation for its excellent combined mechanical properties. For the forming and failure processes of FMLs, the interfacial behavior and damage evolution of components are hard to be observed experimentally. Therefore, it is of great importance to simulate them accurately. In this article, the development and application of FMLs were first introduced. Then the comparison of constitutive models in FMLs simulation was given, especially the dynamic constitutive model applied to the metal layer. After that, the important aspects of damage evolution, interface behavior, and model optimization in the simulation on the forming and failure process of FMLs were analyzed, and the emphasis is on the nonlinear progressive damage model of different materials, the construction of cohesive zone model and superior meshing methods. Furthermore, the experimental verifications of FMLs simulation were given. It is shown that the deformation behavior and damage characteristics of various kinds of FMLs during forming and failure processing can be accurately predicted by reasonable numerical simulation. Eventually, the future outlooks for numerical simulation of FMLs was proposed. Through this review, scholars and engineers who are interested in FMLs can systematically understand the numerical simulation work of FMLs, which is helpful in improving the quality of research in this field.

Artificial neural network models were developed to estimate forming limit diagrams from tensile test results based on our own experiments and data from the literature for steel and aluminium sheet metals. Experimental data were obtained from tensile tests and Nakazima tests. The input parameters used in the models were yield strength, ultimate tensile strength, uniform elongation, elongation at fracture, anisotropy coefficient and hardening exponent or combinations of these. The forming limit curves were defined by the measured minor and major strains using seven standard test specimens. After training the artificial neural network, the difference between measured and predicted results was evaluated by linear regression parameters and by the absolute errors. For steel sheet data taken from the literature, the estimated outputs of ANN models were compared with the results of empirical formulae developed by different authors. It was found that there was a high correlation coefficient between predicted and measured values for models using neural networks, which gave better approximations than other linear and non-linear models.

Multi axial forging (MAF) is a forging-based severe plastic deformation (SPD) technique which is prominently used to refine grain structure and improve the strength of the material. While the advantages of MAF lie in its simple tool design and ability to process bulk materials, the main limitation is the inhomogeneity in the generated microstructure across the cross-section at initial passes. Increasing the number of MAF passes may partially help to solve the problem, but arbitrary increase in the number of passes may lead to redundant increase in manufacturing cost and time. The current work proposes a manufacturing strategy for MAF to achieve homogeneous microstructure with uniform grain refinement by using reduced number of MAF passes. To achieve structural uniformity within fewer MAF passes, a controlled thermo-mechanical based optimum MAF process strategy is developed on a commercial pure Al through the finite element analysis (FEA) simulation and the same is validated experimentally. The manufacturing strategy resulted significant grain refinement via simultaneous action of continuous dynamic recrystallization and geometric dynamic recrystallization with microstructural homogeneity which caused a significant improvement in tensile properties (more than two times than the base) with considerable ductility (more than 25%) and isotropy property across the thickness. The scientific knowhow has been established via processing–structure–property correlation-ship.

The current study exhibits the influence of aging temperatures on the metallurgical, hardness, and dry-sliding wear behaviour of LM25 (Al-6.6Si-0.2Mg) alloy reinforced with Al₂O₃ particles. The LM25 alloy reinforced with 10 wt% of alumina particles was fabricated using the liquid metallurgy route followed by solutionizing and aging. The baseline LM25 alloy and its composite were solutionized at 538 °C for 8 h and were aged at 155, 165, and 175 °C for 12 h. Optical, FESEM, EDS, and X-ray diffraction analysis were done on the fabricated alloy and its composite in all conditions. The microstructure revealed the formation of the Mg₂Si phase in the baseline alloy and the MgAl₂O₄ spinel generated at the composite interface of the aluminium matrix. The heat-treated alloy and composites were tested for their hardness on the Vickers microhardness tester. It was concluded that the aging temperature of 155 °C displayed significant enhancement in hardness values for tested samples. The heat-treated alloy and composite samples displayed an increment of 96% and 55% in hardness values relative to LM25. The wear rate and friction coefficient for the fabricated samples were analyzed using the pin-on-disc tribometer under dry sliding conditions. The hardness value increased from the as-cast state to samples aged at 155 °C and then decreased at 165 and 175 °C. Based on the wear study, a 14% and 25% decrease in the wear rate values for heat-treated alloy and composites were noted when sliding velocity was increased from 1 m/s to 3 m/s. However, the coefficient of friction (COF) decreased by 23% and 13% for the specimens in the same conditions. Furthermore, a similar trend was displayed by age-hardened LM25 alloy and the composite when subjected to varying load (5, 10, 15 N) condition. Lastly, the worn-out surface mechanisms were examined using FESEM analysis. Amongst the investigated samples, LM25/10 wt% Al₂O₃ composite aged at 155 °C revealed the least wear rate when subjected to an external load of 5 N and sliding velocity of 2 m/s. Therefore, it can be suggested to manufacture components in the automotive industry.

Sustainable cooling/lubrication strategies including dry, minimum quantity lubrication (MQL), cryogenic (LN₂) and hybrid (MQL and LN₂) were used in ultrasonic vibration helical milling (UVHM) machining to improve the performance of hole-making for CFRP/Ti–6Al–4V stacks. The machining temperatures and forces were measured to characterize the thermo-mechanical effects on UVHM with different cooling/lubrication conditions. The machining temperatures at cryogenic conditions were −146 °C, −170 °C and −53 °C at CFRP layer, interface and Ti–6Al–4V layer, respectively. Axial and radial resultant forces at different conditions were highly related to the cutting temperature. Fiber removal mechanism at different conditions was analyzed according to the cutting temperatures, forces and the kinematic analysis in UVHM. Effects of sustainable cooling strategies and ultrasonic vibration on the hole surface texture of Ti–6Al–4V alloy were discussed. The amplitudes at different conditions varied approximately from 3.5 to 7 μm due to the variation of the forces. High precision of the exit geometry was achieved, as the height of hole exit burrs at Ti–6Al–4V layer were less than 40 μm except for the cryogenic condition. Diameters at the MQL and hybrid conditions were closer to the target diameter (ϕ10 mm), and the precision of the cylindricity of the machined holes of the stacks with the MQL and hybrid cooling conditions was higher than those at other conditions. Tool wear at different conditions were analyzed according to the SEM and EDS results. This work provided the fundamental understand of the hybrid process with sustainable cooling/lubrication strategy in UVHM machining. High quality of holes in CFRP/Ti–6Al–4V stacks were achieved by the hybrid processes.