Search Results (358)

Cold forging backward extrusion is mainly employed in the manufacturing of axisymmetric cup-like components used extensively in automotive and aerospace assemblies due to the process-induced strength that has a pivotal role in such applications. Although cold forging backward extrusion yields mechanically robust components, it demands high forces, subjecting tooling to immense stress, thereby restricting process capacity. The process encounters hindrances in gaining widespread industrial acceptance due to frequent failures of die elements, necessitating proper die design and control of major influencing factors for process viability and cost-effectiveness. The punches in backward extrusion are often susceptible to failures when processing steel billets. The punch service life is significantly affected by geometrical attributes, the type of steel undergoing deformation, and tool manufacturing aspects. Hence, the present study evaluates punch performance in cold forging backward extrusion using optimized geometrical attributes, manufactured through a design of an experimental approach comprising an L9 orthogonal array. The manufacturing factors considered are punch material, hardness, and advanced surface coating. Punches were designed for two industrial components using powder metallurgy (PM) steels—S600, S290, and S590, heat treated to 60–66 HRC, and coated via physical vapor deposition with TiN, AlTiN, and TiAlCN. Punch performance was analyzed against existing industry practices, and the strategy demonstrated improved productivity. Punch performance was determined based on the number of forgings produced before wear- and fatigue-induced failures. Significant improvements in punch performance were witnessed in both high-speed steel (HSS) and PM punches with optimized geometries. Fractographic investigations were carried out on fractured punches and analyzed, focusing on the coating’s effect on the thermal aspects of the punches. The proposed study will assist the cold-forging industry in determining appropriate variables to minimize forming responses, thereby enhancing tool life. The research also benefits industries by enhancing process robustness and improving process efficiency with respect to cost and time. Full article

This study explores the feasibility of using polyurethane (PU) elastomer as a flexible punch-filling medium in cold forming. Microforming processes encounter challenges such as size effects and friction effects, which can lead to defects including fractures, distortions, and central depressions. The proposed method incorporates a high-hardness PU plate (95A) with excellent elasticity and near-incompressibility to address these issues. By compensating for axial compression through lateral expansion, the PU plate distributes pressure uniformly, reduces central stress, mitigates central acceleration effects, and minimizes defects caused by velocity gradients. Experiments and simulations using aluminum alloy Al 1050-O demonstrate that the PU-assisted extrusion–cutting process improves material flow, redistributes forming pressure, and enhances forming stability compared to conventional methods. This approach shows significant potential for advancing microforming technologies, particularly in industries requiring high-precision components. Full article

To reduce mold costs in composite forming, multi-point tooling technology has been integrated into the hot diaphragm forming process. However, this approach still faces several challenges, including time-consuming prepreg layup, high energy consumption, and poor surface quality. This study proposes a heating pad-assisted multi-point thermoforming process: the prepreg is embedded in the thermal functional layers, placed on the lower mold, and formed via the downward movement of the upper mold to accomplish mold closure. Instead of the conventional rectangular array, this study adopted multi-point tooling with a hexagonal pin arrangement. Compared to traditional configurations, this hexagonal layout increases the punch support area by 9.8%, while its dense punch arrangement improves the accuracy of the molded curved surface. Taking a saddle-shaped surface as the target, a prototype part was fabricated. Subsequent analysis of the part’s surface quality identified three defects: dimples, fiber distortion, and ridge protrusions. The surface dimples were eliminated by adjusting the distance between the upper and lower molds. Notably, ridge protrusion is a defect unique to the hexagonal pin arrangement. We conducted a detailed analysis of its causes and solutions, finding that this defect arises from the combined effect of the pin arrangement and the saddle-shaped surface. Through a series of height compensation experiments, the maximum deviation at the ridges was reduced from 0.46 mm to approximately 0.35 mm, which is consistent with the deviation of defect-free areas. This work demonstrates that the multi-point hot-pressing process provides a potential, efficient, and low-cost method for manufacturing double-curvature composite components, whose effectiveness has been verified through the saddle-shaped case study. Full article

With the continuous growth of highway traffic volume and the increasing proportion of heavy vehicles, vehicle–bridge collisions have emerged as a significant accidental hazard threatening the safe operation of bridge infrastructure. Systematic investigation of the collision resistance of critical bridge components is therefore essential for the development of rational anti-collision design strategies and reliable risk assessment methods. Focusing on the representative disaster scenario of high-speed heavy vehicles impacting concrete bridge piers, this study first develops a finite element model of an RPC beam and validates its reliability through impact experiments. The validated modeling approach is then extended to bridge piers, where a high-fidelity finite element model established using ANSYS/LS-DYNA 2020 is employed to simulate the vehicle–pier collision process and to systematically investigate collision force characteristics, bridge damage evolution, and collision response behavior. The results show that the established reactive powder concrete (RPC) beam model, validated through drop hammer impact tests, reliably captures the impact-induced damage and dynamic response of concrete members. During heavy-vehicle impacts, the vehicle head and cargo compartment successively interact with the pier, generating two distinct collision force peaks, with the peak force induced by the cargo compartment being approximately 38.2% higher than that caused by the vehicle head. Severe damage is mainly concentrated within the impact region, characterized by punching shear failure on the impact face, tensile damage on the rear face, and shear failure near the pier top. The collision-induced structural response is dominated by horizontal displacement, which remains below 10 mm during the vehicle head impact but exceeds 260 mm under the cargo compartment impact. Significant displacements are also observed in the cap beam, with maximum horizontal and vertical values of 24 mm and 19 mm, respectively. These findings provide valuable insights into the impact behavior and failure mechanisms of concrete bridge piers, offering a sound theoretical basis and technical support for anti-vehicle collision design, collision-resistant structural optimization, bridge damage assessment, and the refinement of relevant design specifications. Full article

Forming tools adjustable by tensile elastic deformations offer opportunities for improved process control and reduced wear in high-volume metal forming processes such as ironing. However, the lack of tensile and fatigue data for hardened cold-work tool steels limits their broader adoption. This study investigates the mechanical performance of three tool steels—Vanadis^®4 Extra SuperClean, Vancron^® SuperClean, and Caldie^®—through uniaxial tensile and fatigue testing, supplemented by destructive static and fatigue/wear tests on specimens representative of an adjustable ironing punch. Non-coated specimens exhibited ultimate tensile strengths above 2700 MPa with approximately 2% plastic strain, while coated specimens fractured in a brittle manner between 1600–1900 MPa. Fatigue life at stress ranges between 1450–1750 MPa varied from several thousand to over four million cycles, with crack initiation linked to non-metallic inclusions and precipitates 10–30 μm in size. Finite element simulations accurately linked failure observed in uniaxial tests to the component-level tests, confirming that first principal stress is a reliable predictor for punch failure. All punch specimens withstood 10⁶ cycles at diameter changes up to 140 μm (4‰), with coated punches exhibiting minimal wear and non-coated ones showing localized surface damage. The findings support material and coating selection for adjustable forming tools and highlight opportunities for further optimization. Full article

The progressive stamping process includes blanking, piercing, bending, and drawing operations on press machines with a single die set for high production runs. The processing conditions at individual progressive stamping stations are intricately coupled, posing a challenge for maintaining part quality at high production rates and dimensional precision. This study investigated the effects of the die bottom dead center (and later, BDC) depth, punch-die clearance, tool wear condition, and lubrication performance on the precision of stamped parts and bending angles. Quality characteristics were measured using a coordinate measuring machine (CMM) by employing a thin-sheet steel progressive die in a factorial experimental design. Using Pareto effect plots and the MINITAB platform, it was observed that for part bending angles, the first greatest factor of importance is BDC, followed by clearance as the second greatest, and then tool condition. The results reveal that although it affects part quality through interactions, the lubrication effect is not as significant as the main factors. However, SEM analyses show that worn tools and inadequate lubrication induce grain boundary separation, microcracking, and dislocations, while proper lubrication and sharp tooling maintain more homogeneous grain structures. Research indicates that achieving the full control of part quality in the progressive stamping process requires more than bottom dead center (BDC) adjustment; factors such as component clearances, punch condition, and lubrication level must also be considered. Process-based knowledge of the relationships among process parameters in multi-stage stamping processes can be used to develop adaptive monitoring systems that stabilize part geometry and minimize production variation. Full article

This study optimized the punch-assisted demolding technique for the separation of contact lenses, incorporating finite-element analysis to evaluate the effects of punch geometry (punch material: 304L stainless steel) on the stress and strain distributions of polypropylene lens molds. The simulation results revealed that the punch surface featured a flat base with a central arc-shaped groove (groove diameter: 7 mm, depth: 0.75 mm), which exhibited optimal stress dispersion characteristics during the demolding process, effectively reducing mold deformation. Experimental validation over 100 demolding cycles confirmed that the use of the aforementioned punch resulted in the manufactured lens having high central stability and reduced van der Waals forces during demolding, allowing smoother lens release and facilitating improved demolding performance. Comprehensive evaluation based on defect inspection and centering stability indicated that a yield of 82% was achieved with the optimized punch, with this yield being 13% higher than that obtained with a flat punch lacking an arc groove (69%). These results indicate that the optimized punch design not only reduces development costs but also enhances manufacturing yield and throughput, demonstrating strong potential for application in contact lens production. Full article

As research on new, lightweight energy vehicles continues to develop, the application of high-strength steel sheets with tensile strength greater than 1 GPa and their mechanical clinching technology, which is associated with aluminum alloys, has emerged as a new research focus. However, due to the challenges associated with the cold deformation of high-strength steel, conventional mechanical clinching processes often fail to establish effective joint interlocking, resulting in weak connections. This study proposes a center-punching mechanical clinching process for connecting DP980 high-strength steel to AL5052 aluminum alloy. The mechanical evolution during the forming process was analyzed via finite element simulation. An orthogonal experimental design was employed to optimize key geometric parameters of the punch and die, yielding the optimal configuration for the mold. Mechanical testing of the joint demonstrated average pull-out force and pull-shear forces of 1124 N and 2179 N, respectively, confirming the proposed process’s ability to successfully connect high-strength steel and aluminum alloy. Full article

The West Nile Virus (WNV), transmitted by Culex mosquitoes as a major vector, has been reported worldwide. Also, West Nile neuroinvasive disease (WNND) caused by WNV lineage 1a and 2 neuroinvasive infections has been constantly reported with high fatality rates. Nevertheless, there are no treatments and vaccinations, so diagnosis in the early stages is important. Recently, a molecular diagnostic technique using DNA endonuclease-targeted CRISPR trans reporter (DETECTR) with the CRISPR-Cas12a system integrated with isothermal nucleic acid amplification has newly emerged. In this study, we designed a 2-Step WNV DETECTR with reverse transcription–recombinase polymerase amplification (RT-RPA) for rapid and sensitive WNV diagnosis. It successfully detected down to 1.0 × 10² RNA copies for both WNV lineage 1a and 2 with demonstrating similar sensitivity to qRT-PCR without cross-reactivity to other viruses. Additionally, we designed a 1-Step WNV DETECTR, incorporating all processing steps into a single tube, capable of detecting down to 1.0 × 10³ RNA copies for both lineages. Furthermore, we developed a more streamlined method, the 1-Step with Filter WNV DETECTR, which achieved detection limits comparable to the 2-Step method, while reducing the processing time by 5 min. This study also explored the potential of the Punch-it™ NA-Sample Kit as an efficient alternative lysis method by comparing the detection differences across various lysis methods. Through this method, we achieved rapid and simple amplification and detection processes suitable for field diagnostics with high specificity and sufficient sensitivity. Therefore, DETECTR methods presented themselves as promising alternatives to conventional diagnostic tools, potentially overcoming financial and technical constraints in diverse medical settings. Full article

Punching is a widely adopted cold sheet metal forming process, prized for its cost-effectiveness and high production efficiency. However, premature tool failure remains a persistent challenge, leading to increased downtime and maintenance costs. This study investigates solutions to mitigate tool failure through a combination of 3D design optimization, Finite Element Modeling (FEM), and Response Surface Methodology (RSM). Specifically, FEM was used to analyze stress distribution and deformation in the punch under varying geometric and operational parameters, while RSM optimized the design space to identify key factors influencing tool life. The findings reveal that each proposed solution, including modifications to punch geometry, clearance, and material treatment, offers distinct advantages and trade-offs. A comparative analysis of these solutions highlighted one optimal design, which was then further analyzed using FEM to predict damage progression. While this study provides a framework for reducing tool failure, experimental validation of the damage prediction model is recommended for future work to confirm the numerical results. This research aims to provide industrial practitioners with actionable insights and methodologies to enhance punch durability, ultimately reducing production interruptions and costs. Full article

The present research investigates the optimization of the punching process in cold forming manufacturing, focusing on enhancing tool life, reducing damage, and improving product quality. Punching, a shearing process widely used in sheet metal forming, requires careful management of process parameters to prevent tool damage, especially to the punch and die. The research explores various design modifications to the punching tool, including conical, pointed, and stepped shafts, aimed at reducing punching force and minimizing wear, fatigue, and crack formation. Using numerical simulations (ABAQUS/Explicit), the study evaluates the impact of shear angle, punch geometry, and other key parameters on the maximum punching force and stress distribution. The results show that adjusting the punch shaft shape and optimizing the shear angle can significantly decrease stress concentrations, extend tool lifespan, and improve process efficiency. This work provides valuable insights for improving punching tool designs and ensuring longer, more efficient service lives in industrial applications. Full article

Warm deep drawing is an effective special deep drawing technique for improving the forming limits of difficult-to-form materials such as aluminum alloys, magnesium alloys, and stainless steels. This paper experimentally investigated the effect of a combined variable process path, which integrates a variable punch speed (VSPD) and a variable blank holder force (VBHF) path, on the warm deep drawing performance of an A5182 aluminum alloy sheet at 300 °C (where the strain rate sensitivity index m equals 0.11). Experiments demonstrated not only a reduction in the forming time and an improved wall thickness uniformity, but also an improvement in the forming limits. The significant improvement in the forming characteristics is discussed in terms of the theoretical three-dimensional process window (SPD-BHF-flange reduction ratio (ΔDR*) space) consisting of the fracture limit and flange wrinkling limit derived from deep drawing theory, and it was shown to be consistent with the experimental results. Finaly, the novel combined VSPD/VBHF process path successfully achieved deep drawing with a challenging drawing ratio (DR) of 3.3. Full article

This study investigates a metal-contact etching process that differs from conventional device contact etching by focusing on the film-stack configuration and the associated super-contact etching characteristics. Because metal-contact etching is closely linked to both physical profiles and electrical performance, evaluating a single parameter provides limited insight; thus, the physical profile characteristics of metal-contact etching and 3D-integrated super-contacts were comprehensively examined. In the first-step etch, the target depth in the wafer left region was approximately 2365 Å, and the bottom surface exhibited a desirable rounded profile. Following the removal of liner TEOS and nitride, the stopping margin was evaluated under three conditions: (1) metal-contact etching with a ~22 s target reduction, (2) a CMOS image-sensor baseline incorporating an interlayer-dielectric-reduction scheme, and (3) a high-selectivity condition achieved by increasing the C₅F₈/O₂ ratio with a reduced etch target. Under all three conditions, the bit-line contact (BLC) nitride experienced punch-through. To address this limitation, a three-step etch sequence was implemented, in which the first two steps achieved the required etch depth and the final step utilized a high-selectivity over-etch to secure a sufficient stopping margin. This approach demonstrated robust process windows, favorable CD control, and reliable nitride stopping performance, thereby establishing a practical methodology for stable super-contact etching in advanced 3D-integrated logic applications. Full article

Different types of polymeric materials are used as footbeds in shoes. Environmental degradation behavior of polymeric footbed materials is an important parameter for understanding materials’ environmental footprint. Most of the previous studies focus on geotextiles, polymeric insulation materials, and exposure behaviors that are not the same due to the nature of applications of geotextiles and insulations being completely different from the footbeds. There is a lack of studies to understand artificial weathering, the influence of physical–chemical factors, and the subsequent behavior of different types of footbeds. In this paper, we have selected three needle-punched nonwoven footbed materials and studied their environmental degradation behavior by subjecting them to artificial weathering using different exposure durations, viz. 120 h, 240 h, and 360 h. The physical–chemical properties of polymeric footbed materials were characterized by Fourier-Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and thermogravimetric analysis (TGA). The selected polymeric footbed materials were made from recycled polyester (RPET), hemp, and shoddy fibers. Furthermore, the RPET footbed was tested for biodegradation in soil and compost conditions for 120 days. The footbed materials were also tested for physical and performance (tensile and abrasion resistance) properties. Hemp footbed materials undergo abiotic degradation after 120 h, but in the case of RPET, it undergoes abiotic degradation after 360 h, resulting in a fragmentation process due to synergistic effects of chemical and hydrolytic degradations. From the DSC results, RPET undergoes a slight thermal transition under abiotic degradation after 360 h, indicating that environmental abiotic factors influence degradation behavior. The tensile and abrasion resistance properties of RPET were the highest, followed by hemp and shoddy materials. The tensile strength range of the materials was between 50.74 and 851.44 N. The weight loss range after abrasion resistance was 0.016–0.014%. From the RPET biodegradation test in soil and compost conditions, the evolved CO₂ was 20% and 59%, respectively, after 110 days. The DSC and TGA results indicate that the hemp footbed materials have a higher rate of abiotic degradation as compared to the RPET and shoddy footbed materials. From the RPET biodegradation test in soil and compost conditions, the CO₂ degradation values were 20% and 59%, respectively. The obtained degradation results indicate that the synergistic effect of abiotic and biotic conditions greatly influences footbed materials’ biodegradation under natural environmental conditions. Full article

Carbon fiber-reinforced polymer (CFRP) laminates are extensively utilized in aerospace and advanced engineering fields because of their outstanding strength-to-weight ratio and superior fatigue durability. However, despite their high in-plane strength and stiffness, CFRP laminates are inherently susceptible to delamination. This weakness stems from the relatively low interlaminar strength of the resin-rich interfaces between layers compared to the much stronger in-plane fiber reinforcement. During mechanical processes such as drilling and punching, out-of-plane stresses and interlaminar shear forces develop, concentrating at these weak interfaces. This study investigates the delamination behavior of CFRP laminates with 3 to 7 plies under drilling and punching, focusing on the effects of ply count and drilling speed. Experimental tests were conducted using an 8 mm punch and drill bit at 2500, 3000, and 3500 rpm, reflecting typical workshop practices for M8 fastener holes. Scanning electron microscopy (SEM) analyses at different magnifications were used to quantify delamination extent. A three-dimensional finite element model was created in ABAQUS/Explicit, integrating the Hashin failure criterion to predict damage initiation within the plies and cohesive surfaces to simulate interlaminar delamination. The analyses show that with proper support, punching can approach the damage levels of drilling for thin CFRP plates, but drilling remains preferable for thicker laminates due to better integrity and tool longevity. Full article