Sheet Metal Research Articles

Design of flat hole-clinching for joining polymer and metal sheets

There is a growing need for joining processes capable of joining dissimilar materials, specifically lightweight materials. In this study, flat hole-clinching (FHC) is developed for joining polycarbonate and AZ31 magnesium alloy sheets. A ductile fracture criterion is calibrated using tensile tests and employed in the finite element analysis of the process to investigate the effect of geometric parameters on the joint characteristics and strength. A tool concept is also proposed for the FHC process. Results show that the FHC process enables to successfully connect these sheets without fracture. The flat hole-clinched joint resisted the maximum force of 0.9 kN in the pull-out test, and failed with bottom separation mode.

Modified cure cycles for increased fatigue performance of fiber metal laminates

Modified (MOD) cure cycles that deviate from the manufacturer’s recommended cure profile can reduce the inherent thermally induced residual stresses (TRS) in fiber metal laminates (FML). Literature shows that MOD cycles do not adversely affect the material properties but enhance the quasi-static material strength. However, the literature does not comprehensively discuss the impact of MOD cycles on material performance during cyclic fatigue loading. This paper, therefore, investigates how MOD cycles influence the fatigue characteristics of different FML layups made of carbon fiber-reinforced polymer (CFRP) and steel. The experimental results confirm that the quasi-static material strength and the modulus of the FML are increased when using MOD cure cycles. The evaluation of fatigue tests with digital image correlation, thermography, and electrical resistance measurements of notched specimens shows that a reduction of TRS delays damage initiation in the metal facesheets and decreases the crack growth rate until facesheet failure. The results further show that layup-dependent parameters, the maximum stress in the metal sheets, and metal sheet thickness significantly govern the evolution of fatigue damage. In summary, modified cure cycles are an efficient tool to enhance the quasi-static and fatigue performance of CFRP-steel hybrid laminates.

Digital image correlation and infrared thermography data for seven unique geometries of 304L stainless steel

Material Testing 2.0 (MT2.0) is a paradigm that advocates for the use of rich, full-field data, such as from digital image correlation and infrared thermography, for material identification. By employing heterogeneous, multi-axial data in conjunction with sophisticated inverse calibration techniques such as finite element model updating and the virtual fields method, MT2.0 aims to reduce the number of specimens needed for material identification and to increase confidence in the calibration results. To support continued development, improvement, and validation of such inverse methods—specifically for rate-dependent, temperature-dependent, and anisotropic metal plasticity models—we provide here a thorough experimental data set for 304L stainless steel sheet metal. The data set includes full-field displacement, strain, and temperature data for seven unique specimen geometries tested at different strain rates and in different material orientations. Commensurate extensometer strain data from tensile dog bones is provided as well for comparison. We believe this complete data set will be a valuable contribution to the experimental and computational mechanics communities, supporting continued advances in material identification methods.

Tribological and investigation study of a dlc-coated H13 friction drilling tool on AZ31B magnesium alloy

IntroductionFriction drilling is an innovative method in hole-making for sheet metal applications, thin sheets of conventional structural alloy materials like copper, titanium, steel etc., even though there are other methods, such as thermal distortion for the welding of nuts, riveting of nuts, and threading. For the last hundred years, researchers have focused on studying the development of this technique to maintain strength, hole roughness, hole geometry, hardness etc. It is interested in finding solutions for wear, tool life, and plastic deformation.MethodFriction drilling is also called a green hole-making process because this process uses the friction between the rotating tool and the workpiece. In this research, instead of regular HSS and Tungsten Carbide tools, the H13 tool steel is used, because the H13 steel tool has unique chemical compositions like chromium and molybdenum, which give high toughness, hot hardness, and wear resistance. Diamond-like-carbon (DLC) coating has been used in this research to enhance tool life and AZ31B magnesium alloy is used as the work material. Initially, in this research, the wear stability of the DLC-coated H13 tool was investigated, and later, the tool surface roughness and hole quality were verified.Results and DiscussionThe material loss observed for the DLC-coated H13 steel tool in the pin-on-disk test was 0.05 g. This investigation used two different diameter tools, namely 3 and 7 mm. Research has concluded that the 7 mm tool is better for friction drilling by seeing the roughness and hole quality. However, the conditions were that the spindle should rotate at 4,000 rpm and the feed rate of the tool to be at 200 mm/rev.

Nanoscale dual-axis accelerometer based on a cross-shaped MIM waveguide structure

This paper details the design and simulation of a dual-axis accelerometer based on the cross-shaped MIM waveguide structure, in which mass blocks are set in the middle of metal sheets inside the resonant cavities as acceleration-sensitive elements. To maintain the balance between the sensitivity and accuracy of the accelerometer, the optimal surface plasmon resonances (SPRs) are discussed to determine the relationship between resonance wavelength and acceleration. Firstly, the performances of two single-axis accelerometers are evaluated within the range of -20 g to 20 g, and the fitting results indicate that the wavelengths of specific SPRs are linearly related to the acceleration. The maximum sensitivities of the x-axis and y-axis accelerometers are 0.15 nm/g and 0.31 nm/g, respectively. After that, a dual-axis accelerometer is designed based on the structural features of the two single-axis accelerometers, achieving the maximum acceleration sensitivity Sa and FOM of 0.16 nm/g and 0.0015g-1 along the x-axis, and 0.30 nm/g and 0.0077g-1 along the y-axis. As a result, this design implements high-precision independent dual-axis acceleration sensing and presents substantial potential for application in diverse nano-scale acceleration sensing fields.

Research Status of Laser Welding Technology for Thin Metal Plates

Thin metal sheets have always been one of the core materials in the mechanical industry, and laser welding technology is an important technique for connecting thin metal sheets. This article analyzes the current research status of laser welding technology for metal thin plates, discusses the problems existing in laser welding technology for metal thin plates, points out the development direction of laser welding technology for metal thin plates, solves some problems in the welding process of metal thin plates, and provides reference for future thin plate welding technology.

Determination of an optimum patch configuration in the repair of a center crack in thin aluminum sheet using polymer composite patch

AbstractThe formation of cracks and their growth is an issue of concern in structural applications incorporating thin metal sheets. Adhering cracked region with a patch of composite material has proved effective in repairing cracks. Determining an optimum configuration of composite patch is still a challenge as a shorter patch may not be effective and a larger patch leads to wastage of resources. An appropriate methodology is required for specifying an optimum patch configuration in terms of its length, width, and thickness. The work presented prescribes a methodology for obtaining an appropriate combination of geometrical parameters of the composite patch. The computational tools like finite element analysis and response surface method have been incorporated. This is an extensive work consisting of a number of iterations of numerical analyses carried out for different combinations of the length and width of the patch. The results were also obtained for three different patch thicknesses in which the number of plies were increased from a single ply to three plies. The optimum size was obtained for each of the three patch thicknesses. Finally, a methodology for obtaining the most appropriate patch configuration based on the practical constraint of a small available area is prescribed.Highlights The crack repair in a thin structural sheet using fiber reinforced polymer composite patch separates at the interface. The optimum size of the patch needs to be used for an effective repair. The work consists of a combination of experiments and numerical simulations using finite element analysis. Response surface methodology is employed in this optimization study.

Dissimilar Resistance Welding of NiTi Microwires for High-Performance SMA Bundle Actuators

Shape memory alloys (SMAs) are becoming a more important factor in actuation technology. Due to their unique features, they have the potential to save weight and installation space as well as reduce energy consumption. The system integration of the generally small-diameter NiTi wires is an important cornerstone for the emerging technology. Crimping, a common method for the mechanical and electrical connection of SMA wires, has several drawbacks when it comes to miniaturization and high-force outputs. For high-force applications, for example, multiple SMA wires in parallel are needed to keep actuation frequencies high while scaling up the actuation force. To meet these challenges, the proposed study deals with the development of a resistance-welding process for manufacturing NiTi wire bundles. The wires are welded to a sheet metal substrate, resulting in promising functional properties and high joint strengths. The welding process benefits from low costs, easy-to-control parameters and good automation potential. A method for evaluating the resistance-welding process parameters is presented. With these parameters in place, a manufacturing process for bundled wire actuators is discussed and implemented. The welded joints are examined by peel tests, microscopy and fatigue experiments. The performance of the manufactured bundle actuators is demonstrated by comparison to a single wire with the same accumulated cross-sectional area.

Vibration and noise reduction on a cover for power electronics for electric vehicles with vibroacoustic metamaterials

Electric vehicles represent a particular challenge in terms of noise, vibration and harshness, since there is no masking of the combustion engine anymore. For consumer acceptance, long distances need to be covered with electric vehicle, which makes lightweight structures necessary. Consequently, vibration problems occur during operation, as lightweight structures are more susceptible to vibrations. Common measures for vibration and noise reduction add a considerable amount of mass to the vehicle, counteracting the lightweight efforts. Vibroacoustic metamaterials as a novel approach promise greater vibration reductions than common measures like Alubutyl or bitumen and are accompanied by a lower weight. This study deals with the design of vibroacoustic metamaterials for the noise and vibration reduction of a cover for power electronics of an electric vehicle. The design process is demonstrated for two different kinds of vibroacoustic metamaterials made from sheet metal and a plastic film. The structural dynamic behavior of both approaches is experimentally investigated and compared with a cover equipped with Alubutyl. The vibroacoustic metamaterial, which is made from sheet metal, is furthermore tested in a vehicle under driving condition. A reduction of tonal noise components by 11 dB is achieved within the passenger compartment.

Multi-Response Optimization of Single Point Incremental Forming of Al 6061 Sheet Through Grey-Based Response Surface Methodology

The single point incremental forming process (SPIF) is materialized to form the desired shapes in low-cost sheet metal processing and well suited for low batch components and customized designs. Many modifications have been attempted in recent years to maximize the formability, geometric accuracy and quality of the SPIF formed parts. In this work, an attempt has been made to analyse the influence of process parameters namely ball tool diameter, step size, spindle speed and sheet thickness on final wall thickness, forming force and surface roughness. The optimized results exhibit the desirable formability when the roller ball tool diameter of the tool is 12 mm. The results also project that formability of the sheet metal is minimized when the spindle speed is increased and the ball diameter maximizes the accuracy and surface roughness. Also minimizing the step size increases the product quality features. Upon conducting this multi-response optimization by grey based response surface methodology (RSM) technique It is identified that 12 mm ball diameter of the tool, 0.25 mm step size, 2445 rpm spindle speed, and 2 mm sheet thickness are the obtained optimized SPIF process parameters as confirmed through confirmation experiments.

An extended mesoscaled M-K model for predicting discrete ultimate strains and evaluating the effect of normal stress on forming limits

Due to the size effect, the formability of metal sheets diminishes and the ultimate strain points exhibit a more discrete distribution. This poses a huge challenge to the process design and manufacture of microparts. This paper presents a modified mesoscopic scale forming limit model based on the M-K model. The model extends the forming limit curve (FLC) into forming limit bands to predict the discrete nature of the ultimate strain. In addition, a method for applying normal stresses to increase the forming limit of thin metal sheets is proposed. The effects of normal stresses on surface roughening and flow stresses in thin metal sheets were evaluated and quantified by uniaxial tensile experiments under normal stresses. The results show that the normal stress suppresses the increase of surface roughness and improves the work hardening rate. The effect of normal stresses on forming limits was obtained using a constructed model. The results show that the predictions of the proposed model are able to include almost all the ultimate strain points. The forming limit bands are more inclusive and safer than the single forming limit curve. In addition, the forming limits of thin plates under normal stresses are significantly increased, which is attributed to the suppression of surface roughening and the increase of strain hardening index. The forming limit bands proposed in this paper provide a more reliable form of forming limit assessment for thin metal plates. The proposed method of applying normal stresses provides a robust and inexpensive process route to address the challenge of poor formability of thin metal sheets.

Re-manufacturing of Pre-deformed Automotive Sheet Metal Stamping Scrap Without Melting

Abstract The recycling of aluminium sheet metal typically involves shredding and re-melting, processes which are both energy-intensive and challenged by the presence of metallic contaminants. To mitigate these issues, this study explores an alternative approach: the re-manufacturing of deep-drawn parts directly from scrap aluminium sheets, thus bypassing the melting step. We used 2 mm thick Al-Mg sheet metal in H111 temper to produce simulated stamping scrap (miniaturized bonnets). Blanks were cut from these bonnets and secondary parts in a cross-cup geometry were deep-drawn using two different forming processes: warm-forming at 200 °C and O-temper forming at room temperature. The resulting maximum draw depths were 20-22 mm for warm-forming and 25-30 mm for O-temper forming. While warm-forming resulted in lower draw depths, O-temper forming led to coarse recrystallized grain formation in some regions. Our approach could significantly reduce the energy consumption associated with aluminium recycling.

In-process part tracking and shape measurement using vision-based motion capture for automated English wheeling

An English wheel is an exceedingly adaptable instrument in traditional metalworking. It is a manual manufacturing technique, enabling skilled craftsmen and blacksmiths to shape complex compound curves in sheet metal panels. Accurate measurements and precise adjustments are essential when operating an English wheel to ensure that the metal is shaped with the desired curvature. An automated method to form English wheeled panels through robot forming has recently been proposed. For such a method to be successful, accurate tracking of sheet information including positions, orientations, and deformation is important for error compensation and the design of the subsequent tool paths. In this study, a Vicon motion capture system is employed to monitor the position and shape of the sheet metal during the English wheeling process. The initial experimental results demonstrate the potential of such an in-process metrology system, along with possible avenues for future work.

Forming limit analysis of magnesium alloy sheet metal forming process at elevated temperatures

Abstract Magnesium alloys are valued by industry for their lightweight structures. Magnesium alloy are mainly produced by warm forming because the sheet formability is poor at room temperature. The mechanical properties of magnesium alloy AZ31, such as stress-strain curves and damage values at different elevated temperatures, were obtained by this study using a computerized screw universal testing machine. Freudenthal fracture criteria were used to obtain the forming limit at distinct temperatures. The forming limit analysis proceeded during the sheet metal forming process at various elevated temperature. The fracture’s forming load, stroke, and position were determined for different working temperatures of the sheet metal forming process for AZ31, using a finite element simulation combined with the ductile fracture criteria. Finally, the predicted values were compared with the experimental results during the sheet metal forming process. The simulation results agreed with the experimental values for the fracture forming load, stroke, and position of the sheet metal forming process. The feasibility of the present method was confirmed to predict forming limit during the sheet metal forming process for different elevated temperatures. A finite element analysis for forming limit prediction would be beneficial to the design of sheet metal processes for AZ31 magnesium alloys.

A generalized, computationally versatile plasticity model framework - Part II: Theory and verification focusing on shear anisotropy

Shear-dominated deformation (SHDD) is pivotal in sheet metal forming; however, comprehensive modeling of plastic anisotropy in SHDD, specifically shear anisotropy considering both yield stress and plastic flow, has been inadequately addressed in existing literature. In this work, a generalized constitutive framework is introduced on the basis of stress triaxiality-dependent state variable to accurately emulate plastic anisotropy and the physics-based shear constraint in SHDD. The framework is capable to seamlessly integrate with existing yield criteria, preserving computational efficiency and versatility. Notably, the yield function, anisotropic parameters, and their optimization or analytical determination for the non-shear deformation state remain unaltered. When integrated with the Hill48 yield function, featuring either one or two anisotropic parameters within the generalized constitutive framework, precise characterization of yield strength and plastic flow in SHDD is achieved. The applicability of the framework extends to various anisotropic yield functions such as the widely employed Yld2k-2d and the sixth-order polynomial (Poly6) function as a class of associated flow rule-based yield functions, and one non-quadratic yield function for non-associated flow rule scenarios. Experimental validation with two engineering sheet metals, high-strength dual-phase steel DP980 and high-strength aluminum alloy AA7075-T6, was conducted. Comparative analyses with several recently proposed yield criteria, especially Poly6-18p, highlighted the efficiency of the proposed constitutive framework. Furthermore, this study explores intrinsic shear constraints, particularly the absence of through-thickness strains under in-plane shear stress. Additionally, it offers an enhanced description of plastic anisotropy in shear yield stress within the general framework, providing valuable insights into the complexities of SHDD.

Design and prototyping of smart mobile grinding bots as an educational experience

Abrasive finishing of large areas is often done manually and can be time-consuming, ergonomically challenging, and even detrimental to the operator’s health. Inspired by ant robots, this paper presents a senior design project that developed a grinding robot and a quality robot, which can grind and assess a sheet metal surface. This concept of mobile grinding robots is novel and demands a multidisciplinary design approach. The main requirements included applying a controlled pressure with the grinding spindle to the surface, having a range of mobility within a predefined work area, and communication between the robots. A first prototype was delivered based on Linkbot modules, a commercial power tool as grinding spindle, sensors to measure spindle height, taped work area boundary, and surface finish. The mechanical and electronical system performance was analyzed and tested. This paper presents a proof of concept for smart mobile grinding bots and a reproducible educational experience.

PROSES PEMBUATAN BRACKETBRAKE PEDAL STOPPER TYPE SU2ID MENGGUNAKAN MESIN STAMPING PRESS

AbstractPersada Selaras Indonesia is a company operating in the field of stamping and die sheet metal in Majalengka Regency. One of the products produced at PT. Persada Selaras Indonesia is part of the Brake Pedal Stopper Bracket. In the process of making Brake Pedal Stopper Bracket Parts using SAPH-440 material using a Press Stamping Machine with a capacity of 110 Tons through the Dies selection process for the Blanking, Bending (1 + 2), and Pierching processes. Researchers used the observation method to determine the process of the Brake Pedal Stopper Bracket Part. The Brake Pedal Stopper Bracket Part is one of the components contained in the brake pedal of the Hyundai Creta vehicle which is produced at PT. Persada Aligned Indonesia. The process of making Brake Pedal Stopper Bracket Parts is divided into several parts, namely the Planing process, Shearing, Blanking Process, Bending Process (1 + 2), Pierching Process, and Quality Control Process. Keywords : SAPH-440, Press Stamping Process, Part Bracket Brake Pedal Stopper

Evaluation of the effect of forming strategy in newly introduced flexible roll forming process

In recent years, with the emergence of Industry 4.0 trends and the impact of the COVID-19 pandemic, the agile manufacturing paradigm has gained increasing significance. Substantial efforts have been directed towards introducing new methods, driven by the dual objectives of flexibility and agility. This paper presents an innovative machine that employs two rollers to apply localized deformation to sheet metal through repetitive movement along the length of the sheet. As with all incremental forming processes, the forming strategy is a critical parameter influencing both the forming force and the dimensional accuracy of the manufactured workpiece. In this research, two different forming strategies, internal and external, were implemented for manufacturing elongated 90 deg bends on 1 mm and 3 mm thick AISI 304 sheets. Both numerical and experimental analyses were performed to assess the effects of these different strategies. The results confirm that the forming force with the external strategy is 50 % and 47 % less for the 1 mm and 3 mm sheets, respectively. Moreover, the external forming strategy allows for better control of the obtained angle, but limits the minimum obtainable bending radius.

Fresh water production via atmospheric water harvesting using solar energy for green hydrogen production

Abstract Solar energy is used to drive an atmospheric water harvesting unit to produce fresh water needed for the electrolysis process to produce hydrogen, as well as to drive the electrolyzer. So, the system can be considered as a solar powered hybrid system for fresh water harvesting and green hydrogen production implementing the electrolysis concept. Implementation of the system specially in arid regions with high levels of water scarcity and high relative humidity levels helps in achieving SDGs 3, 7, 9, and 13 progressively, improving health and wellbeing, reducing water scarcity, using clean renewable energy, and limiting climate change. The system is proposed and investigated for the production of both fresh and clean water and green hydrogen gas. To improve the productivity of the overall system, performance enhancement of the atmospheric water harvesting subsystem is experimentally investigated to assure the reliability and continuous operation of the overall green hydrogen hybrid system. It was investigated in summer and winter using different number of porous sheet metals with the silica gel bed. The results show that the productivity of the atmospheric water harvesting system can be increased by a minimum of 6% with one mesh metal sheet and 30% with two meshes, and increases by a maxinmum of 60% with one mech and 260% with two meches.

Smart design and additive manufacturing of bending tools to improve production flexibility

For the automotive industry, especially on the part of Tier 1 and Tier 2 suppliers, the future will be about maintaining sovereignty in the form of technology openness and accelerating digitization. The product portfolio, which is generally passed on by OEMs to suppliers for production, often includes body parts that cannot always be manufactured economically with the prevailing production technology. The reason for this is a high diversity of model-variants, which requires smaller batches. To this end, highly flexible large-series production cells for body sheet components that can be scaled in all dimensions are being developed and tested. For the first time, they will make it possible to redesign the process planning in series production on a component-specific basis. The aim is to reduce production costs for new, geometrically different component variants. The basic components of the flexible manufacturing system are, firstly, new flexible forming technologies which have the potential to produce typical vehicle part geometries. Secondly, a process generator develops the corresponding production plan. A digital mapping of the manufacturing processes enables the selection of cost-, efficiency-, flexibility- and resilience-optimized production chains depending on the number of parts. Established manufacturing processes to produce car body components are supplemented in the cell by flexible processes such as 3D swivel bending. As a use case for flexible manufacturing, a concept for Rapid Tooling of 3D swivel bending tools is developed. In the flexible manufacturing system to be developed, a method of a standardized process sequence to produce forming tools within 24 h has been lacking to date. For this purpose, the concept of an automated design is being developed in which a reconfigurable tool body can be sliced into sheet metal stripes The active tool surface is additively manufactured after the tool has been packaged using LMD and adapted to individual requirements. The goal in the application of Rapid Tooling is to reduce lead times and development costs through a largely automated tool design and lead time-optimized manufacturing concept.