Sheet Metal Research Articles

Compound Die for manufacturing of Plain Washer from sheet metal scrap

Compound Die for manufacturing of Plain Washer from sheet metal scrap

Polymer Tools Produced by Fused Filament Fabrication for Steel-Bending Process: Effect of Layering Orientation

Rapid tooling with polymer tools produced via additive manufacturing offers significant benefits in sheet metal forming processes as it allows for the production of parts with high accuracy while reducing tool production costs. In this research, the authors evaluate the performance of polymer punches and dies in the sheet metal bending of 2 mm thick AISI 314 stainless steel. The tools were made using nylon filled with carbon fiber and produced through Fused Filament Fabrication. Two different print orientations—horizontal and vertical—were compared. This experimental study focused on the accuracy of the sheet’s bending angle and thickness while also measuring the deformation induced in the tools. A new methodology was proposed combining both tools and sheet measures to highlight not only the sheet’s accuracy but also the behavior of the polymer tools. The results demonstrate that despite the permanent deformation of the tools, they were able to produce sheets with a geometry accuracy of less than 0.5%

Resistance of the Steel Lap Joints Connected by Spot Welding and Brazing

Welding technologies are constantly evolving, and their applicability is expanding, considering also the construction domain. Steel structures benefit from the advances in welding technologies due to the use of thin gauge steel sheets which can now be connected at high quality and automatically. The resistance of the connection between the thin steel sheets is crucial for the durability and safety of a structure made of built-up thin-walled cold-formed steel elements. Generally, self-drilling screws or bolts are used for the connection between thin-walled elements, but the quantity of time and manpower necessary for a large number of connections demands an improved solution. Conventional welding techniques are unsuitable for joining thin sheets, ranging from 0.4 to 1.0 mm to thicker ones measuring 1.0 to 3.5 mm. This article compares the results of an experimental investigation into lap joints connected by spot welding and MIG brazing with the design code provisions. The study examines single-lap joints in steel sheets of 0.8, 1.0, 1.2, 1.5, 2.0 and 2.5 mm thickness, connected using these welding technologies. The results obtained are then compared with analytical relations and processed according to EN 1990. Depending on the thickness of the connected sheets, spot welding can lead to two failure modes: button pull-out fracture and interfacial fracture. MIG brazing, a welding technology that deposits material below the melting point of the base material, is known for its advantages, such as low energy consumption, spatter-free operation, high welding speed, and compatibility with thin sheet metals. However, its application in the structural engineering of cold-formed elements lacks documentation. In the study, the MIG brazed specimens failed in the heat-affected zone of the connection. The results indicate the dependence of the spot weld lap joint resistance on the connected sheets' thickness, while the resistance of the MIG brazed lap joints is influenced by the minimum thickness of the connected steel sheet. The study aims to demonstrate the feasibility of the proposed solutions, evaluate their performance, and establish the limits of their applicability. A statistical interpretation of the results highlights the precision and reliability of joint resistance.

Enhancing formability in deep drawing: A 3D finite element analysis of plastic wrinkling in AA2090 Al–Li alloy

Deep drawing is a manufacturing process used to produce billions of metal containers, crucial for the aerospace industry in forming thin-walled components efficiently. However, wrinkling due to compressive instability remains a significant challenge in sheet metal forming. This study investigates plastic wrinkling in sheet metal forming to enhance the final drawn shape. A 3D finite element model using ABAQUS/Explicit was developed to examine the effects of mesh topology, blank holder force, and sheet thickness on wrinkling in AA2090 Al–Li alloy. The finding indicates that that an increase in blank holder force increases wrinkle number and amplitude. Additionally, it was found that a 2000 N blank holder force is necessary to prevent wrinkling.

Error compensation and path planning for sheet metal bending process based on improved modeling algorithms

Error compensation and path planning for sheet metal bending process based on improved modeling algorithms

Numerical investigation of the effect of laser peen forming process parameters on 1060 aluminium sheets under preload

Abstract Laser peen forming process changes the shape of the metal sheet or plate by plastic deformation caused by laser induced mechanical shock wave. The bending behavior of 1060 aluminium sheets under laser peen forming (LPF) are studied numerically taking into account the various laser peening process parameters for two distinct cases; with and without preload. Modal analysis has been performed on 3D finite element model (FEM) to stop post-shock oscillations. A time-dependent and space-dependent pressure distribution is applied to the laser-peened area along with preload at the free end. The numerical comparison of bending angles and surface profile of 1060 aluminium sheets under laser peen forming are studied for both the cases, with and without preload. Preloading provides better surface profile for same bending angle for a no laser shock overlap.

Synthesis and Characterization of TiO2 Nanotubes for High-Performance Gas Sensor Applications

In this study, we investigated the fabrication, properties, and sensing applications of TiO2 nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO2 nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO2 nanotube was found to be suitable for NO2 gas sensor applications. With an oxidation time of 15 min, its detection of NO2 gas showed a good result at 250 °C, especially when exposed to a NO2 gas flow of 100 ppm, where a maximum NO2 gas response of 96% was obtained. The NO2 sensors based on the TiO2 nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

A comprehensive validation of GRA with ant colony optimization for robust optimal design: A case study on the forming process

Sheet metal forming design involves numerous factors and controlling all these parameters to prevent cracks is a major challenge to maintain the quality. Therefore, the careful selection of process parameters is critical for ensuring product longevity. Several researchers employed different techniques for optimal selection of process parameters but consistency among the techniques and validation of results in real time scenarios will play a pivotal role in determining the suitable parameters. Therefore, the current work presents a validation method of Grey Relational Analysis (GRA) results with Ant Colony Optimization (ACO) for the robust optimum design with an illustrative example of forming process. Al 6061 – T6 alloy was chosen as a material for deep drawing process and L27 Orthogonal Array was planned to conduct experiments with four input parameters such as blank thickness, Die and Blank Temperature, Die Speed, Lubrication at three levels each. Punch force and Thickness variation were considered as the output parameters. GRA Technique was implemented to find the best optimal combination and regression equation was developed to predict the nature of objective function. These results were given as an input to ACO, a nature inspired algorithm to search for the optimal solution with in the design space. Sensitivity analysis has also been performed to highlight the effectiveness of the proposed solution in terms of solution quality and computational efficiency. The ACO method, GRA technique and the experimental results are almost similar with a margin of acceptable deviation. The results indicated the robustness of the projected approach in achieving the quality of solution.

Environmental Sustainability Assessment of Cold Storage Panel Production

Today's ever-increasing environmental sustainability concerns have led to a major shift in construction sites and industrial sectors. In this context, the choice of construction materials for important structures such as cold storages plays an important role in terms of both environmental impacts and energy efficiency. The aim of this study is to evaluate the environmental loads of cold storage panels with thicknesses of 80 mm, 100 mm, 120 mm, 150 mm, 180 mm and 200 mm. In order to reveal the production inputs that cause these loads, the environmental effects were examined specifically for the 100 mm thick cold storage panel. Environmental impacts were analyzed using the Life Cycle Assessment (LCA) method in accordance with the ISO 14040/44 methodology as a system boundary "cradle to gate". This study focused on three different environmental impact categories of cold storage panels produced in Türkiye: global warming potential (GWP), cumulative energy demand (CED) and water footprint. In the evaluation of environmental impacts, production inventory information obtained from the panel manufacturer was used. For analyses, Simapro v. 8.5 LCA software was used. Analysis results show that the use of galvanized sheet metal in cold storage panel production is a hot spot in terms of global warming effect. It has been determined that the largest share in the water footprint belongs to polyurethane used as insulation material. Additionally, according to the CED, non-renewable fossil and non-renewable nuclear were determined to be the most affected categories, and the use of galvanized sheet metal and polyurethane were determined to be the most important hot spots in terms of non-renewable and renewable resources. To help improve the environmental performance of the cold storage panel, it is recommended to use bio-based and less environmentally impactful raw materials in production and to measure their environmental impact on a life cycle basis from cradle to grave.

Optimization of machining efficiency and side quality in irregular sheet metal parts milling based on improved multi-objective seagull optimization algorithm

Optimization of machining efficiency and side quality in irregular sheet metal parts milling based on improved multi-objective seagull optimization algorithm

Effect of laser drilling process on combustor liner effusion hole quality

Abstract Effusion cooling is one of the significant cooling technologies in combustor liners in terms of cooling efficiency and weight reduction. However, effusion cooling technology is difficult to manufacture. In fact this technology requires laser-drilling of thousands of tiny holes with shallow angles on a sheet metal with a thickness generally varying between 0.5 to 1.5 mm. In addition, the use of thermal barrier coating is common in gas turbine engines and is one more challenge for the drilling process. In order to obtain more efficient gas turbine engines, the inlet temperature keeps increasing in the last decades, which induces the combustion chamber to operate in a hotter environment. Therefore, efficient cooling technology is needed, even if it is hard to manufacture. For laser drilling, several parameters have to be explored to obtain acceptable holes. This study includes the microstructure investigations of the holes produced with different laser parameters and the optimal laser parameters determined according to the microstructure of six different effusion cooling hole configurations. The results show that laser process differences affect the metal substrate microstructure and thermal barrier coating structure. Drilling method, peak power, number of pulses, gas type and pressure value have a significant effect on the hole geometry and its microstructure.

Comparison of Actual Deformations of Historic Wooden Structures with Values Obtained from Static Calculations

In historic wooden structures, deformations can be influenced by factors that are negligible within the first 50 years of the building's existence. In attics where the roof covering is made of metal sheets, the air and structural elements heat up during the day and cool down rapidly at night. This phenomenon, over a long period, can cause micro-cracks and surface material degradation. For the study, historic buildings meeting the criteria for service class II according to PN-EN 1995-1-1 were selected. Measurements of deflections, humidity, and modulus of elasticity of the wood were conducted. The actual deflections of the examined structures were found to be 28% to 37% higher than those obtained from numerical calculations, indicating ongoing rheological processes in the wooden structures.

Optimizing Sheet Metal Formation through Advanced Hydroforming Simulation Technique

In this study, we investigate into the simulation of sheet metal hydroforming for crafting the cap of the axle-hub of a tip trailer within our manufacturing facility. This cap serves a crucial role in safeguarding wheel bearings from the detrimental effects of dust, sand, and dirt. The motivation for this work arises from the challenges encountered during the fixation of a conventional dust cap, which often falls off when subjected to pressure or threading, particularly when the tractor is in motion. The innovative approach pursued in this research involves the utilization of lightweight aluminum sheet metal for cap production, owing to its facile formability. The cap design incorporates four evenly distributed holes around its circumference and secures to the flange using screws. Prior to the manufacturing phase, a simulation of the cap-forming process was conducted using ANSYS Model 15, a computer-aided engineering program. The necessary models were crafted in CATIA, a computer-aided design program, streamlining the entire process to enhance efficiency, reduce costs, and minimize manpower requirements. The simulation encompassed three different thicknesses (1 mm, 2 mm, and 3 mm) for two distinct aluminum alloys, namely 1100 and 5652. The objective was to discern the optimal alloy for the forming process. Essential mechanical properties, including ultimate tensile strength, modulus of elasticity, and yield stress, were input into the ANSYS program to accurately reflect the materials' behavior during forming. The outcomes of our investigation revealed that aluminum alloy 5652 outperformed 1100 in terms of formability. The former exhibited a forming pressure of 300.2 MPa, while the latter required 298.3 MPa for the same forming depth (40 mm) across all three thickness variations. Additionally, the study demonstrated that 5652 is not only more efficient but also safer and more resilient than 1100.

Kill Two Birds with One Stone: Cracking Lithography Technology for High-Performance Flexible Metallic Network Transparent Conductors and Metallic Micronano Sheets.

Flexible electronics have sparked a wide range of exciting applications, such as flexible display technologies, lighting, sensing, etc. Flexible conductors are essential components of flexible electronics and seriously affect efficiency and overall performance. Here, a facile and kill-two-birds-with-one-stone strategy of cracking lithography technology has been proposed to simultaneously fabricate two high-performance flexible conductors, flexible metallic network transparent conductors (f-NTCs) and metallic micronano sheets (MMNSs). The PET substrate flexible transparent conductors (FTCs) based on this strategy yield 88.1% transparency within the visible spectrum and a sheet resistance of 9 Ω/sq. In addition, the FTCs show exceptional mechanical stability, with the sheet resistance remaining virtually unchanged even after 6000 s of bending tests. Subsequently, the remaining MMNSs are recycled to manufacture a Ag paste, showing a very low conductive percolation threshold (∼13%) and excellent flexibility with 140% breaking elongation. After 1000 s of stretching tests, it showed excellent mechanical stability. Furthermore, flexible electroluminescent devices based on the FTCs and sensors fabricated with MMNSs both show excellent performance, demonstrating their potential wide applications in flexible electronics.

Unconventional mechanical responses and mechanisms of Ti-6Al-4V sheet subjected to electrically-assisted cyclic loading-unloading: Thermal and athermal effects

For the sake of unveiling the macro-micro behaviors and underlying control mechanisms of electroplastic effect (EPE) of sheet metals during recent thriving electrically-assisted incremental forming (EAIF) processes, electrically-assisted cyclic loading-unloading tension (EACT) experiments were carried out at a current density of 14～20A/mm2 followed by forced and unforced cooling. The electro-thermo-mechanical responses and the evolution rules of dislocation configurations, fracture modes, phase composition and local orientation distribution were characterized by IR imaging, SEM, quantitative EBSD and TEM tests. Moreover, the thermal and athermal components of the electrically-induced stress drop throughout the EACT processes were decoupled and systematically analyzed via temperature control tests and isothermal correction. The results show that thermal effect of electric current possesses a great proportion of 75 % in the overall stress drop and plays a key role in elastic modulus degradation and ductility enhancement by activating pyramidal {101‾1}⟨12‾10⟩ slip systems, weakening (0001) texture and promoting dynamic recrystallization (DRX) and α→β→α′ phase transformation. While the athermal effect only operates after reaching both threshold current density and plastic strain, it increases monotonically with current density, brings about “hot spots” effect, local charge imbalance and weakened atomic bonding, and further causes intensified local strain gradient, substructure formation and DRX nucleation. The ratio of athermal stress drop first decreases and then increases significantly with loading cycle at the later stage of EACT under the combined effect of local Joule heating effect and flow localization. Additionally, the athermal effect only activates short-range solute diffusion and localized diffusional α→β phase transformation, while the combined thermal and athermal effects promote long-range solute diffusion and an increasing rate in β content of 261.8 %. The present work provides theoretical basis for optimizing the EAIF forming process and realizing extreme manufacture of light-weight thin-walled complex components.

Design and Fabrication of a Novel Commercial Baking Oven

This study presents the design and fabrication of a novel wood-fired commercial oven for baking bread. The oven design features an external combustion chamber with heating elements which comprise stainless-steel pipes filled with magnesia starting from the combustion chamber to the 3 oven compartments. Each compartment has 12 heating elements laid under a mild steel sheet metal where the dough mould and its content is placed. Heat loss due to conduction, radiation and convection was prevented by the use of a double wall in both oven and combustion chamber compartments with silica brick and fibre glass respectively, and the oven was fired with wood to bake some dough. Findings showed that maximum temperature attainable by the oven was 700°C, however, the temperature required for baking bread is between 150°C and 180°C and the time was 25 minutes, the quantity of heat generated per time using 10 kg of wood was about 15,088 KJ. Furthermore, the physical appearance of the products was examined to meet consumers’ requirement and a total of 400 bread of 180 mm × 120 mm × 80 mm dimensions can be baked at a time. With slight modifications in the oven design, this number can be improved. The oven can be fired with other types of solid biofuels and can be used for metallurgical furnace applications like annealing, tempering and other heat treatments of metals.

Polymer Shaped Punches Produces with Fused Filament Fabrication to Improve Cup Accuracy in Sheet Metal Forming

Rapid tooling has become an effective solution for reducing time and costs in tool production. In sheet metal forming, polymer tools produced via additive manufacturing offer performance comparable to traditional tools. However, a key challenge in this area is compensating for the radial expansion of polymer tools during the forming process, which leads to reduced accuracy in the produced parts and limits the achievable forming depth. To address this issue, the authors of this study proposed a novel punch design aimed at containing radial expansion, thereby enabling greater drawing depth and improved part accuracy. Different punch geometries were designed with a re-entrant angle varying between 150° and 180°. Numerical simulations were conducted to evaluate the optimal geometry, identifying the 160° angle as the best option to compensate for radial expansion and reduce punch load. Experimental tests were then performed to verify the numerical results, demonstrating the potential of this new design producing cups with higher drawing depth and best radial accuracy.

Numerical springback prediction for high-strength aluminum alloys based on the sheet metal upsetting test

Springback prediction continues to play a special role in the process design of sheet metal forming processes. During the forming process, elastic energy is stored in the sheet metal, which is released after the tool is opened. The dimensional accuracy and the function of the component in particular can be negatively affected by this. For this reason, the springback is predicted by means of numerical modeling in order to improve the process design. The simulation accuracy depends primarily on the used material model to map the stress-dependent material behavior and the quality of the experimental input data. High-strength aluminum alloys, which have a distinctive springback behavior, have a slightly pronounced tensile-compressive asymmetry. Since tensile and compressive stresses often occur in sheet metal forming processes, the consideration of this effect can lead to an improvement in springback prediction. Besides modeling the yield locus curve for describing the yield strength in the plane stress area, the yield curve data is also relevant for determining the strain hardening behavior. The work hardening is usually characterized by the tensile test or the hydraulic bulge test, which is used to describe the material behavior in the tensile stress state. A promising experimental method for the analysis of the material in the uniaxial compressive stress state is the sheet metal upsetting test. In addition to a local characterization of sheet metal materials, this test also enables the investigation of the material behavior at significantly higher plastic strains than in the tensile test. Thus, in this contribution it is examined to what extent the sheet metal upsetting test is suitable for improving the springback prediction quality of material models in sheet metal forming processes.

Novel method to assess anisotropy in formability using DIC

In this study, a novel technique was developed to identify localized neck of a tensile sample based on the curvature of the surface that is expected to work with any metal in which a localized neck forms prior to fracture. Moreover, a MATLAB-based computational tool has been developed to conduct advanced mathematical computations and numerical analysis on data generated from uniaxial tensile test of DP980 steel coupled with Digital Image Correlation (DIC) based on the novel curvature method. The presented curvature technique is a geometry-based approach that uses the specimen's surface profile and groove geometry to detect localized necking, avoiding the limitations of strain-based methods in distinguishing between localized and diffuse necking. A detailed analysis was conducted on the accuracy of the onset and anisotropy of localized neck. The results of the study revealed that specimens fabricated with 30-degree orientation with respect to the Rolling Direction (RD) of the sheet metal, exhibit a higher level of total strain at the onset of the localized necking, indicating the influence of anisotropy on the material's behavior for DP980. Moreover, consistent R-values were observed among specimens with the same orientation with respect to the RD, exhibiting a rising trend of R-value for orientations from zero to 60-degree, followed by a decrease from 60 to 90-degree. Furthermore, the results exhibited a negative linear relationship between R-values and the magnitude of thinning strain.

Analysis of projection welding in relation to the non-parallelism of electrodes

The article contains the analysis of projection welding in relation to the non-parallel location (non-parallelism) of electrodes. For a thin-walled flat element, e.g., sheet metal with two embossed projections, calculations were conducted for different angles between the upper electrode and the lower electrode. The calculation involved the use of the SORPAS 3D software. The analysis included the distribution of temperature, power density, electrode displacement, the volume of molten metal in the weld nugget, nugget diameters, and energy supplied to the weld. The article presents the comparison of results obtained for various angles between the electrodes of the welding machine. The results of numerical calculations were verified experimentally through technological welding tests and destructive tests (peeling/metallographic). The convergence of the experimental and numerical results was satisfactory. The tests involved a typical element used in the automotive industry, i.e., a nut with two embossed projections in the flat part. The article represents quite an innovative new approach to multiple-projection welding from a numerical calculation point of view. Such an approach allows the researcher to identify the phenomena taking place in the process. The article also presents a new approach to the analysis of multi-projection welding as regards the non-parallelism of electrodes. The results enabled the determination of phenomena taking place in the multi-projection welding process as well as the boundary conditions in relation to which the process became improper (unstable).