Thin-walled Sheet Metal Research Articles

Enhancing the electromagnetic forming performance of thin-walled sheet metal via a thicker driver: forming behavior and experimental validation

Enhancing the electromagnetic forming performance of thin-walled sheet metal via a thicker driver: forming behavior and experimental validation

Defeaturing of CAD Models Using Machine Learning

Part features, such as dents, holes, and bumps, are integral to the thin-walled sheet metal components used in the automobile and aerospace industries. These features are often required to be suppressed for more agile and reasonably accurate results during the CAE analysis. However, identifying these features is a critical task usually performed by experts. It requires a detailed analysis of the CAD model, which largely depends on the importance of each feature, feature size, and domain boundary conditions. Thus, identifying such features is a challenging task. This work proposes a novel data-driven approach to create an intuitive model that identifies suppressible features on CAD models of sheet metal parts. The dataset to train the supervised learning model is generated by extensive finite element analysis of the part models. The case studies show that the trained Machine learning model gave good test accuracy.

Optimization Method of Sheet Metal Laser Cutting Process Parameters under Heat Influence

To address the issues of workpiece distortion and excessive material melting caused by heat accumulation during laser cutting of thin-walled sheet metal components, this paper proposes a segmented optimization method for process parameters in sheet metal laser cutting considering thermal effects. The method focuses on predetermined perforation points and machining paths. Firstly, an innovative temperature prediction model Tpr,t is established for the nth perforation point during the cutting process, with a prediction error of less than 10%. Secondly, using the PSO-BP-constructed prediction model for laser cutting quality features and an empirical model for processing efficiency features, a multi-objective model for quality and efficiency is generated. The NSGA II algorithm is employed to solve the objective optimization model and obtain the Pareto front. Next, based on the predicted temperature at the perforation point using the model Tpr,t, the TOPSIS decision-making method is applied. Different weights for quality and efficiency are set during the cutting stages where the temperature is below the lower threshold and above the upper threshold. Various combinations of machining parameters are selected, and by switching the parameters during the cutting process, the thermal accumulation (i.e., temperature) during processing is controlled within a given range. Finally, the effectiveness of the proposed approach is verified through actual machining experiments.

Numerical and experimental fatigue strength evaluation of thin-walled aluminum components for aerospace application manufactured by roll forming

The design of structural components for use in commercial aircraft places high demands on the safety under static and cyclic loading conditions during the total operating time. With immerging innovative developments in the production of thin-walled sheet metal components, savings in energy consumption and material are achievable by switching from metal-cutting production to forming operations. As the forming process has an impact the local material properties due to resulting residual stress state, cold working and surface finish, the fatigue life estimation requires the consideration of the forming history.The structural component under consideration from aluminum alloy EN AW-7475 T761 is manufactured by automated, robot-assisted roll forming. Potentially existing residual stresses are determined via process simulation of the angled profile utilizing commercial finite element solver LS-Dyna®. The fatigue life assessment is carried out using the Local Strain Approach for different loading conditions.

A review of process parameters in friction drilling on joining of steels

Friction drilling is a unique way of creating holes in steel. In a solitary advance, a rotating conical tool is utilized to enter by penetrating as an opening on the surface of the sheet and making a bushing without making a chip. During this process, the heat produced by the frictional power linking the device and the sheet metal workpiece is used to pierce and make a bushing out of work. The goal of this novel hole-making process is to improve the bushing length in the thin-walled sheet metals by forming a bush and then combining thin sheet metals. The inconceivable utilizations of warm grating penetrating in a few modern areas will introduce another period of interfacing processes for different work materials in automobiles.Researchers have undergone numerous experiments based on the machining parameters, including spindle speed, feed rates, Friction Contact Ratio (FACR), tool angle, tool diameter, sheet thickness, and the output of the friction drilling, includes the bushing length, surface roughness, tool wear, hardness, thrust force, torque and microstructural evaluation.The crucial concerns that should be addressed and researched by researchers in the near future, such as determining the optimal machining parameters of such process and analysing, bushing length, microstructural impacts on the many aspects and their performance, are highlighted.This research paper tends to examine the advancements in research on the friction drilling method and its applications, taking into account the benefits and limits of friction drilling.The present paper identifies the machining parameters and their contribution towards the output level of various materials like Stainless steel, Brass, aluminium, titanium, tempered steel and nickel-based compounds of different thickness.The machining parameters like spindle speeds, feed rate, tool angles, thrust force, Torque, surface roundness, bushing height, frictional heat and tool diameter are optimized in the friction drilling. The incorrect bushing is formed due to the high thrust force, and Low temperatures cause ductility and softening issues.

Numerical investigation of the clinched joint loadings considering the initial pre-strain in the joining area

The components of a body in white consist of many individual thin-walled sheet metal parts, which usually are manufactured in deep-drawing processes. In general, the conditions in a deep-drawing process change due to changing tribology conditions, varying degrees of spring back, or scattering material properties in the sheet blanks, which affects the resulting pre-strain. Mechanical joining processes, especially clinching, are influenced by these process-related pre-strains. The final geometric shape of a clinched joint is affected to a significant level by the prior material deformation when joining with constant process parameters. That leads to a change in the stiffness and force transmission in the clinched joint due to the different geometric dimensions, such as interlock, neck thickness and bottom thickness, which directly affect the load bearing capacity. Here, the influence of the pre-straining in the deep drawing process on the force distribution in clinch points in an automotive assembly is investigated by finite-element models numerically. In further studies, the results are implemented in an optimization tool for designing clinched components. The methodology starts with a pre-straining of metal sheets. This step is followed by 2D rotationally symmetric forming simulations of the joining process. The resulting mesh of each forming simulation is rotated and 3D models are obtained. The clinched joint solid model with pre-strains is used further to determine the joint stiffnesses. With the simulation of the same test set-up with an equivalent point-connector model, the equivalent stiffness for each pre-strain combination is determined. Simulations are performed on a clinched component to assess the influence of pre-strain and sheet thinning on the clinched joint loadings by using the equivalent stiffnesses. The investigations clearly show that for the selected component, the loadings at the clinch points are dependent on the sheet thinning and the stiffnesses due to pre-strain. The magnitude of the influence varies depending on the quantity considered. For example, the shear force is more sensitive to the joint stiffness than to the sheet thinning.

Design Using Special Steel Sheet Profiles – Procedures Developed within the Framework of Grispe and Grispe Plus Projects

AbstractNew computational procedures developed within the framework of international research projects „Grispe” and „Grispe Plus” are briefly presented and characterised here. Considered algorithms pertain to the verification of bearing capacity and serviceability of selected bearing structure components erected with especially shaped thin-walled sheet metal panels. Structural components of this type are so far rather absent from the codes, and as a result the unequivocal design requirements have not been developed for them. Key problems related to the detailed analysis of the following element classes: steel decks with embossments, indentations and/or outwards stiffeners; liner trays; corrugated sheeting; curved profiles; cladding and roof profile assemblies; perforated and holed profiles; external interlocking planks and their assemblies are indicated in the text. The procedures formulated as a part of the projects indicated above have been delivered to CEN as an official proposal of amendments and/or additions submitted for introduction to the new generation of Eurocodes currently under preparation, and especially as an extension to the code EN 1993-1-3.

NUMERICAL ESTIMATES OF CURRENTS AND FORCES IN LINEAR TOOLS OF THE MAGNETIC-PULSE ATTRACTION OF METALS. PART 1: LOW ELECTRICAL CONDUCTANCE METALS

Цель. Целью работы является обоснование дееспособности линейных инструментов магнитно-импульсного притяжения тонкостенных листовых металлов с высокой удельной электропроводностью, принцип действия которых основан на силовом взаимодействии проводников с однонаправленными токами при интенсивном проникновении возбуждаемых полей. Методика. Для численных оценок использовались аналитические зависимости, полученные с помощью методов теории электромагнитного поля, и стандартные программы из пакета «Wolfram Mathematica». Результаты. Проведенные вычисления иллюстрируют амплитудно-временные зависимости для возбуждаемых токов и сил при требуемом понижении рабочих частот действующих электромагнитных полей. Обоснована действенность линейных магнитно-импульсных инструментов, основанных на возбуждении сил взаимного притяжения проводников с низкочастотными однонаправленными токами. Научная новизна. На примере с алюминием, который является основным сырьевым материалом в современном авиа- и автомобилестроении, установлено, что для металлов с высокой удельной электропроводностью требуется значительное понижение рабочих частот, что необходимо для интенсификации процессов проникновения действующих полей и, соответственно, для возбуждения реальных сил притяжения. Практическое значение. Результаты работы позволяют сформулировать обоснованные рекомендации по созданию и практическому применению линейных инструментов магнитно-импульсного притяжения в прогрессивных технологиях восстановления повреждённых участков корпусных покрытий из тонкостенных листовых металлов с высокой удельной электропроводностью.

Experimental investigation on friction drilling of stainless steel AISI 304

Friction drilling is an unexplored manufacturing process to produce holes in thin-walled sheet metals. In this study, the effects of process parameters in friction drilling of austenite stainless steel investigated experimentally and statistically. It was confirmed, sufficient heat generation, which cause to better bushing shape and height, acceptable drilled-hole diameter and lowest roundness error result from low spindle speed and high feed rate. It was obtained, although effect of feed rate on hole-wall thickness was negligible; spindle speed has significant effect on that which is inverse from spindle speed effect on bushing height. Moreover, micro-hardness reduced gradually away from the drilled-hole edge. Observing on tool shape and wear damage using optical microscope and scanning electron microscope quantifies effects of spindle speed and feed rate on tool performance and tool wear characteristics. Results indicate that better performance of drilling tool obtained from lower spindle speed and high feed rate.

Experimental investigation on friction drilling of stainless steel AISI 304

Friction drilling is an unexplored manufacturing process to produce holes in thin-walled sheet metals. In this study, the effects of process parameters in friction drilling of austenite stainless steel investigated experimentally and statistically. It was confirmed, sufficient heat generation, which cause to better bushing shape and height, acceptable drilled-hole diameter and lowest roundness error result from low spindle speed and high feed rate. It was obtained, although effect of feed rate on hole-wall thickness was negligible; spindle speed has significant effect on that which is inverse from spindle speed effect on bushing height. Moreover, micro-hardness reduced gradually away from the drilled-hole edge. Observing on tool shape and wear damage using optical microscope and scanning electron microscope quantifies effects of spindle speed and feed rate on tool performance and tool wear characteristics. Results indicate that better performance of drilling tool obtained from lower spindle speed and high feed rate.

Improving Friction Drilling and Joining through Controlled Material Flow

Friction drilling is a novel hole-making process that can be performed on thin-walled sheet metals. The friction between a rapid-rotating conical tool and a sheet metal workpiece generates heat to soften and displace the material to form a hole. The bushing is formed in-situ from the workpiece. This experimental study investigated the effects of feed rate and spindle speed on the thrust load curve of friction drilling. Generating a good quality bushing has been a challenge in friction drilling. A counter-bore die was proposed and implemented to eliminate cracks and petal formation. Threads were tapped to demonstrate the improvement of the bushing quality. The present work also evaluated the feasibility of joining sheet metals with friction drilling. It was found that under an appropriate process condition, it is possible to perform friction drilling through two metal sheets to create a weld joint.

MAGNETIC PULSED PROCESSING OF METALS FOR ADVANCED TECHNOLOGIES OF MODERNITY – A BRIEF REVIEW

The aim of the article is dedicated to the brief review of the main achievements of the advanced technologies with usage of the energy of the pulsed magnetic fields. Originality. The new suggestions are represented. They are based on the results of development of the new scientific direction in area of the magnetic pulsed processing of thin-walled sheet metals when a penetration of the acting fields is quite significant. The known traditional approaches based on the skin-effect in electrodynamics and were successfully implemented. Methodology of the analysis consist of careful theoretical and practical experiments review and its future development. Results of the research based on the existing experimental approbation were presented visually with the description followed The known approaches to solution actual production problems based on the skin-effect in electrodynamics are described. Practical value. The first of practical propositions is related to stamping of the drawing the printed circuit boards on the cooper foil with thickness about ~50 mkm. This operation is realizing by the forces of magnetic pressure directly without any supplements introduction. The second consists in usage the magnetic pulsed attraction for external removing the dents in the car body. This operation does not demand disassembling of elemental base and allows preserving the paint of coverings. Both of these technologies could to minimize the working time, to decries the volume of the waste products and to make the manufacturing existed much cheaper. References 10, figures 3.

Hyperplasticity effect under magnetic pulse straightening of dual phase steel

An investigation of the behaviour of dual phase steel parts during straightening operations, by means of magnetic pulse treatment, is presented. The mechanical analysis of magnetic-pulse treatment for the straightening of thin-walled sheet metal parts produced from dual phase steel was performed, taking into account the effect of hyperplasticity under the influence of the magnetic field. Taking account of the causes of the hyperplasticity and thus the increase of material plasticity, it has been shown that the magnetic impulse gravity can be adjusted by controlling the operation modes. The dependence of the generated magnetic impulse gravity force on the electrical current strength inducted in this part was explored and used for analysis of the magnetic pulse straightening of dual phase steel part. Experimental results were obtained for thin-walled sheet metal part produced from dual phase steel DP 780. The results are used to demonstrate the material deformation under the influence of magnetic impulse gravity force considering the increase of material plasticity. The dependence of relative material deformation on the generated magnetic impulse gravity as well as on the current strength induced in this material was obtained and analyzed

Modeling and predicting of aeronautical thin-walled sheet metal parts riveting deformation

Purpose Riveting deformation is inevitable because of local relatively large material flows and typical compliant parts assembly, which affect the final product dimensional quality and fatigue durability. However, traditional approaches are concentrated on elastic assembly variation simulation and do not consider the impact of local plastic deformation. This paper aims to present a successive calculation model to study the riveting deformation where local deformation is taken into consideration. Design/methodology/approach Based on the material constitutive model and friction coefficient obtained by experiments, an accurate three-dimensional finite element model was built primarily using ABAQUS and was verified by experiments. A successive calculation model of predicting riveting deformation was implemented by the Python and Matlab and was solved by the ABAQUS. Finally, three configuration experiments were conducted to evaluate the effectiveness of the model. Findings The model predicting results, obtained from two simple coupons and a wing panel, showed that it was a good compliant with the experimental results, and the riveting sequences had a significant effect on the distribution and magnitude of deformation. Practical implications The proposed model of predicting the deformation from riveting process was available in the early design stages, and some efficient suggestions for controlling deformation could be obtained. Originality/value A new predicting model of thin-walled sheet metal parts riveting deformation was presented to help the engineers to predict and control the assembly deformation more exactly.

Improvement strategy for edge waviness in roll bending process of corrugated sheet metals

This paper focuses on the corrugated thin-walled sheet metal in the roll bending process. The main defect that appears in corrugated panels subjected to high amounts of bending deformation is a wavy edge. Edge defects are caused by excessive longitudinal stress and strain near the edge of the plate, and local edge buckling may occur when some critical value of the bending radius is exceeded. This paper proposes two different approaches to avoid a wavy edge for a formed panel: excessive stress on the edge region is restrained by controlling the length of the cross-sectional end of the corrugated panel while considering the stress distribution, and the bending radius in each forming step is determined by considering the strain limit at which the initial edge waviness occurs to avoid excessive compression at particular steps. The experimental and numerical results indicated that the two proposed design strategies can minimize wavy edges in the formed shape.

STRAIGHTENING TOOL «INDUCTOR SYSTEM WITH AN ATTRACTING SCREEN» AND LENGTHY SOLENOID

The article presents the analysis of electrodynamic processes in the «inductor system with an attracting screen». Its design is presented by a cylindrical multi-turn solenoid at the end of which various thin-walled sheet metals are attached. Estimates of excitation efficiency of electrodynamic attracting forces are presented. The adequacy of Physics and mathematical model is provided by taking into account the inductor geometry, its location and diffusion effects

New Method of Car Body Panel External Straightening: Tools of Method

Recently repair and recovery vehicle body operations become more and more popular. A special place here is taken by equipment that provides performance of given repair operations. The most interesting things are methods for recovery of car body panels that allow the straightening without disassembling of car body panels and damaging of existing protective coating. Now, there are several technologies for repair and recovery of car body panels without their disassembly and dismantling. The most perspective is magnetic-pulse technology of external noncontact straightening. Basics of magnetic-pulse attraction, both ferromagnetic and nonferromagnetic thin-walled sheet metal, are explored. Inductor system calculation models of magnetic-pulse straightening tools are presented. Final analytical expressions for excited efforts calculation in the tools under consideration are introduced. According to the obtained analytical expressions, numerical evaluations of excited forces were executed. The volumetric epures of the attractive force radial distributions for different types of inductors were built. The practical testing of magnetic-pulse straightening with research tools is given. Using the results of the calculations we can create effective tools for an external magnetic-pulse straightening of car body panels.

THE EXCITED LOADS OF ATTRACTION IN A SYMMETRICAL INDUCTOR SYSTEM FOR THE MAGNETIC PULSE REMOVING OF THE BODY CAR

Recently, repair and recovery of vehicle body operations become more and more popular. A special place here is taken by equipment that provides performance of given repair operations. The most interesting are methods for recovery of car body panels that allow the straightening without disassembling of car body panels and damaging of existing protective coating. Now, there are several technologies for repair and recovery of car body panels without their disassembly and dismantling. The most perspective is magnetic-pulse technology of external noncontact straightening. Results. The calculation of excited loads attractions in a symmetrical inductor system in the universal tool of magnetic-pulse straightening is provided. According to the obtained analytical dependence of the numerical evaluation of volumetric construction diagrams, phase and amplitude of the radial dependence of the spatial distribution of the excited efforts of attraction is obtained. The influence of the magnetic properties of the blank screen and manifested in the appearance of powerful magnetic attraction forces is determined. Originality. A new trend of research of magnetic-pulse working of thin-walled metals has been formulated and received further development, which allows to create not only new equipment, but principally new technological processes of external non-contact repair and recovery of vehicle body panels. Scientific basis of electrodynamic and magnetic attraction of thin-walled sheet metals with using the energy of high-power pulsed fields was created for the first time and proved theoretically and experimentally. Scientific and technical solutions in design of effective tools based on single-turn inductor systems of cylindrical geometry for straightening and recovery of car body panels were formulated and proved theoretically, as well as experimentally. Practical value. Using the results of the calculations we can create effective tools for an external magnetic pulse straightening of car body panels.

Multi-cornered thin-walled sheet metal members for enhanced crashworthiness and occupant protection

Crash energy management in frontal crumple zone of the automotive body is one of the key elements for the design of automotive structure. Improving energy absorption characteristics reduces the magnitude of forces transferred to the occupant compartments. Here, a new strategy has been proposed to improve energy absorption efficiency of thin-walled columns by introducing extra stable corners in the cross-section. Several profiles of multi-corner thin-walled columns obtained through this strategy were presented and their crashworthiness capacities under axial crush loading were investigated analytically, experimentally, and numerically. First, explicit formulations for predicting the mean crushing force of multi-corner thin-walled columns were derived using the theory of super folding element (SFE). Predicted results of these formulations showed a good agreement with the results of quasi-static experiments and CAE simulations, which were performed by explicit non-linear finite element code through LS-DYNA. Based on this agreement, other significant crashworthiness assessment parameters were then investigated experimentally and numerically. Newly introduced 12-edge section with high energy absorption capacity was developed and its dominance was established through the responses in quasi-static experiments and CAE simulations. Finally, the foundational dominance of the 12-edge section was extended to the dynamic environment through a full vehicle crash test simulation to evaluate overall reduction in crashworthiness parameters which reflected occupant safety. Interestingly, in the case of using 12-edge section as crush absorbers, specific energy absorption (SEA), dash intrusion and maximum occupant’s chest deceleration showed significant improvement, compared to the baseline design which used a rectangular section.

Multiobjective crashworthiness optimization of multi-cornered thin-walled sheet metal members

Plastic deformation of structures absorbs substantial kinetic energy when impact occurs. Therefore, energy-absorbing components have been extensively used in structural designs to intentionally absorb a large portion of crash energy. On the other hand, high peak crushing force, especially with regard to mean crushing force, may lead to a certain extent and indicate the risk of structural integrity. Thus, maximizing energy absorption and minimizing peak to mean force ratio by seeking for the optimal design of these components are of great significance. Along with this analysis, the collapse behavior of square, hexagonal, and octagonal cross-sections as the baseline for designing a newly introduced 12-edge section for stable collapse with high energy absorption capacity was characterized. Inherent dissipation of the energy from severe deformations at the corners of a section under axial collapse formed the basis of this study, in which multi-cornered thin-walled sections was focused on. Sampling designs of the sections using design of experiments (DOE) based on Taguchi method along with CAE simulations was performed to evaluate the responses over a range of steels grades starting from low end mild steels to high end strength. The optimization process with the target of maximizing both specific energy absorption (SEA) and crush force efficiency (CFE), as the ratio of mean crushing load to peak load, was carried out by nonlinear finite element analysis through LS-DYNA. Based on single-objective and multi-objective optimizations, it was found that octagonal and 12-edge sections had the best crashworthiness performance in terms of maximum SEA and CFE.