Clamped Sheet Research Articles

Revolutionizing automotive lightweighting: a comparative analysis of electromagnetic free forming for clamped sheets

Reducing vehicle mass is a critical strategy for enhancing fuel economy and meeting the growing demand for lightweight materials in the automotive industry. Aluminum alloys have emerged as a promising solution due to their low density, but their limited formability compared to steel poses significant challenges. Electromagnetic Forming (EMF) is a high-speed process capable of significantly improving the formability of aluminum alloy sheets, enabling the production of lightweight structural components for automotive applications. This process operates within microseconds, which provides a unique advantage for rapid and efficient manufacturing. The numerical modeling of EMF plays a pivotal role in understanding the complex physics and deformation behaviors associated with this process. This research investigates the numerical modeling of EMF for various aluminum alloy sheets using a spiral coil. The results provide insights into the distinctive deformation behaviors and performance variations of different alloys under identical process conditions, which offers valuable guidance for material selection and process optimization in automotive applications.

Feature Segmentation of Multifeatured Freeform Geometries for Incremental Sheet Forming

Incremental sheet forming (ISF) of sheets is a flexible forming process that forms a geometry from a clamped sheet using local deformation of the sheet by moving a forming tool along a predefined path. Many factors are responsible for the accessibility and accuracy of forming in the ISF; some of them are forming force, sheet thickness, clamping force, working temperature, and toolpath. One of the important factors which affect the ISF process is the toolpath. However, conventional toolpath generation strategies are designed for the machining process and are not suitable for forming multifeature parts in the case of ISF. A feature segmentation method, which would segregate geometry into multiple features and generate the optimum toolpath with the correct forming sequence, is required to successfully form multifeatured parts through ISF. This paper presents a simple, but an innovative method to segment a component into multiple geometrical features. The proposed method uses the internal characteristics of the STL part file and the number of sliced contours on the parts for feature segmentation.

Analysis of material behaviour and shape defect compensation in the flexible roll forming of advanced high strength steel

Roll forming is a fast and low-cost forming process with the ability to form a wide range of materials, especially advanced high-strength steels (AHSS) that have limited ductility. However, roll forming is only able to form constant cross-sections along the longitudinal direction of the component, while many automotive components are more complex in shape. Flexible Roll Forming (FRF) uses rolls that have the ability to translate or rotate during production, enabling the manufacture of a part that has a variable cross-section potentially useful for the automotive industry.Deakin University is equipped with a flexible forming facility that can prototype parts with variable cross-sections. The machine has been developed, patented and manufactured by dataM Sheet Metal Solutions GmbH. Deakin’s Flexible Forming Facility (DFFF) consists of a single forming stand with two opposing robotic arms connected to forming rolls. The flexibly controlled arms form the clamped sheet along a CNC defined bend line while the sheet remains clamped. This facility is capable of creating changes in the cross-section in both width and depth along the part. Moreover, the Deakin facility can form the part in both forwards and backwards directions along the longitudinal dimension of the part. In contrast, conventional FRF facilities use multiple stands of forming rolls, and the forming sequence occurs in a single direction along the part.The first part of this study compares material deformation in the DFFF in contrast to that of the conventional FRF setup. This study will determine the similarities and differences in the final formed part between DFFF and the forming conditions in conventional FRF. The second step of the study is to investigate the forming properties of the final part when the part has variable depth. An experimental part formed on DFFF was compared to a numerical analysis using COPRA RF FEA to investigate the material flow and the forming defects. The results show that the major shape error is wrinkling. A new forming concept using a blank holder tool was analysed, and it shows promising results in regard to wrinkling reduction.

PADDLE SHAPE OPTIMIZATION FOR HOLE-FLANGING BY PADDLE FORMING THROUGH THE USE OF A PREDEFINED STRAIN PATH IN FINITE ELEMENT ANALYSIS

This research investigates a novel hole-flanging process by paddle forming through the use of finite element (FE) simulations. Paddles of different shapes rotating at high speeds were used to deform clamped sheets with pre-drilled holes at their centers. The results of the simulations show that the paddle shape determines the geometry and principal strains of the formed flanges. A convex-shaped paddle forms flanges with predominant strains in the left quadrant of the forming limit diagram (FLD). However, the convex paddle promotes unwanted bulge formation at the clamped end of the flange. A concave paddle forms flanges with no bulge but the principal strains of elements in the middle section of the flange are in the right quadrant of the FLD which indicates an increased probability for crack occurrence. An optimization of the paddle shape was conducted to prevent bulging at the clamped end while avoiding crack occurrence. The paddle shape was optimized by mapping the deformation of some elements along the flange length to a pre-defined strain path on the FLD while maintaining the bulge height within the desired geometric tolerance. The radii and lengths of the paddle edge were varied to obtain an optimum paddle shape.

Joining of thermoplastic structures by Friction Riveting: A mechanical and a microstructural investigation on pure and glass reinforced polyamide sheets

Friction Riveting is a spot joining, which consists in rotating a cylindrical rivet and inserting it into clamped sheets. In the first friction phase, the rotational speed and the applied axial force heat the material by friction plasticizing it. After that, the spindle rotation is stopped and the axial force is increased passing to the so called forging phase. Several working parameters, such as the rotational speed, the friction and forging times, and the friction and forging pressure, have to be optimized to achieve sound connections.In the proposed work, the attention was given to the joints of sheets made of a thermoplastic material with and without short glass fiber reinforcements. Rivets were made of Titanium Grade 2. The quality of the obtained results was verified by tensile tests. Moreover, microscopic observations were performed analyzing the material deformation and integrity inside the connection volume. The influences of the monitored process parameters on the above highlighted outputs were reported providing a guideline for the process execution.

Automated Flexible Forming Strategy for Geometries With Multiple Features in Double-Sided Incremental Forming

Double-sided incremental forming (DSIF) is a dieless sheet metal forming process that uses two generic tools to form a part of arbitrary geometry from a clamped sheet via the accumulation of small localized deformations. In DSIF, there is a need for an automatic toolpath generation method to separate geometric features coupled with a strategy to form these features in the correct sequence such that they can be accurately formed. Traditional CNC machining toolpaths are not suitable for DSIF because these toolpaths are designed for material removal processes, which do not have to account for the motion of the virgin material during the process. This paper presents a novel and simple way to represent geometric features in a hierarchical tree structure during z-height-based slicing along with algorithms to generate different forming strategies using this tree structure. The proposed approach is demonstrated through physical experiments by forming a complex part with multiple features.

An approach to eliminate stepped features in multistage incremental sheet forming process: Experimental and FEA analysis

Incremental sheet forming (ISF) is a recently developed manufacturing technique. In ISF, forming is done by applying deformation force through the motion of Numerically controlled (NC) single point forming tool on the clamped sheet metal blank. Single Point Incremental sheet forming (SPISF) is also known as a die-less forming process because no die is required to fabricate any component by using this process. Now a day it is widely accepted for rapid manufacturing of sheet metal components. The formability of SPISF process improves by adding some intermediate stages into it, which is known as Multi-stage SPISF (MSPISF) process. However during forming in MSPISF process because of intermediate stages stepped features are generated. This paper investigates the generation of stepped features with simulation and experimental results. An effective MSPISF strategy is proposed to remove or eliminate this generated undesirable stepped features.

Incremental sheet punching on the base of sinusoidal tool path

To carry out incremental sheet-punching process without adding any additional device on a common numerical control machine or a specialized incremental sheet-forming machine, a method was proposed by modifying the tool path generated by commercial CAD/CAM software. The method consists of a few steps: generating the tool path for the three dimensions model of the desired part, exporting the tool path as dispersed points, interpolating the tool points with liner polynomial, modifying the tool points to sinusoid in the vertical direction to the clamped sheet, exporting the new sinusoidal tool path, etc. Different geometries were formed using two kinds of sheets, non-perforated sheet and perforated sheet, to determine the feasibility of the method. Furthermore, the effects of the wavelength and the amplitude of the sinusoidal tool path on material formability and surface quality of the formed sheet were analyzed on the basis of forming truncated funnels and pyramids. The results show that it is feasible to form both non-perforated sheet and perforated sheet by the proposed method. Additionally, they show that the wavelength has obvious influence on material formability and surface quality while the amplitude only influences material formability significantly.

Investigation of Punching Parameters Effect on Mechanical Properties of Al-1100-O in Incremental Sheet Metal Hammering Process

Incremental forming process is an efficient method for rapid prototyping and low-volume production. Recent ideas have been presented for a new type of this process known as incremental sheet metal hammering method. In incremental sheet metal hammering process, a three-dimensional work piece is produced by only moving a hammering punch over a clamped sheet metal without using a special die. In this paper, the effect of diameter and frequency of the punch on the mechanical properties of Al-1100-O sheet will be investigated. To investigate these parameters, the hardness, tensile strength and the grain size and orientation have been considered. Finally, it is indicated that by decreasing the punch diameter and by increasing the punch frequency, the hardness and the tensile strength of the formed material are increased. Two different statistical models were suggested for prediction of mechanical properties after incremental sheet metal hammering process.

Design and development of an incremental sheet metal hammering system using mass damper

Incremental forming is a method for rapid-prototyping and low-volume production. Incremental sheet metal hammering is relatively a new technique in which successive blows of punch on the clamped sheet are used to apply desired shape. In this article an incremental sheet metal hammering system has been designed and developed. The developed mechanism is equipped with a cam shaft including some hard metallic balls as dampers into the central driver core. It can reduce the system vibration to some degree. This research describes the theoretical, simulation and practical background of the designed system. In addition, experiments are accomplished to assess the tool performance. Also, by evaluation of experimental results, the effects of some parameters on the surface quality and maximum forming angle have been studied.

A Mixed Double-Sided Incremental Forming Toolpath Strategy for Improved Geometric Accuracy

Double-sided incremental forming (DSIF) is a relatively new dieless forming process which uses two hemispherical ended tools, one on each side of the sheet, moving along a predefined trajectory to locally deform a peripherally clamped sheet of metal. DSIF provides greater process flexibility, higher formability, and eliminates the tooling cost when compared to conventional sheet forming processes. While DSIF provides much improved geometric accuracy compared to other incremental forming processes, current toolpath planning strategies suffer from long forming times. A novel mixed double-sided incremental forming (MDSIF) toolpath strategy is proposed in the present study. It simultaneously reduces the total forming time by half while preserving the best currently achievable geometric accuracy. The effect of the forming parameters, i.e., of the incremental depth and of tool positioning on the geometric accuracy of the parts formed with MDSIF was investigated and compared to those formed by traditional DSIF strategies.

Experimental investigation into effect of cooling of traversed weld nugget on quality of high-density polyethylene joints

Thermal residual stress is an undesirable and unavoidable phenomenon in welding structures. It causes distortion of the weld and reduces the weld’s mechanical properties. In the present study, a new setup of friction stir welding process including cooling of weld nugget was developed to enhance the weld strength and to reduce the angular distortion of the friction stir welded polyethylene sheets. The clamped sheets are firstly welded by FSW process, and then, the traversed weld nugget is cooled by injection of CO2 gas. Here, Taguchi experimental design and response surface methodology were used to analyze effects of tool rotary speed, traverse speed, and cooling gas intake pressure on tensile strength and angular distortion. Also, the nondestructive ultrasonic evaluation was used here to measure residual stress to justify variation of angular distortion. Obtained results revealed that applying cooling causes better consolidation of plasticized material; also, it causes releasing residual stress and decreases the angular distortion.

Investigation of dimensional accuracy in incremental sheet metal hammering process: a parametric study

With the increasing demand for low-volume production, the incremental forming process is developed as a rapid prototyping method. Incremental sheet metal hammering method has been used in recent years. In this process, a sequence hammer moving over a clamped Aluminum sheet and a three dimensional workpiece can be produced by using a simple die. In this paper, the influence of the punch diameter on the dimensional accuracy was studied. This component was divided to four sections: thickness, overall geometry, surface quality and spring-back. By using the image processing and roughness tester, the values of results were obtained and analyzed. The results had revealed that the surface roughness and spring-back were decreased by decreasing the punch diameter. Overall geometry was deviated from the ideal shape by increasing the punch diameter.

Incremental Sheet Forming (ISF) of AISI 316 Stainless Steel Sheet Using CNC Milling Machine

Incremental sheet forming (ISF) is a method to form a sheet metal into desired shape and surface features in a batch production series. This method includes forming a clamped sheet metal in controlled conditions by a CNC milling machine, lathe machine or a robot. In this study, the effects of forming parameters on the amount of stretch in stainless steel sheet using a CNC milling machine have been investigated. A ball-point shaped tool made of a bronze alloy was fabricated and used throughout the experiments. The tool acted as the indenter that formed the stainless steel sheet into a small pyramid-like shape. The results showed that as the spindle speed and feed rate increased, the amount of sheet stretch also increased, up to a point where the sheet could not stretch anymore and the process changed from forming to shear thinning and chipping. In addition, the surface quality of the part was badly affected at higher spindle speed and feed rate settings. The temperature of the lubrication oil was also measured during the process and the maximum temperature recorded was 45°C which remained constant until the end of the process. In conclusion, to obtain a good quality part while increasing the productivity of ISF, the optimized values of the feed rate and spindle speed in this work were found to be at 500 mm/min and 1000 rpm respectively.

Laser dimpling and remote welding of zinc-coated steels for automotive applications

The flexibility in terms of beam shapebility and amplitude in the range of process parameters offered by the emerging high power and quality active fiber lasers can be advantageously used in overcoming the well-known problems in remote laser welding of zinc-coated steel components in the car mass production. The paper explores the potentiality offered by the combination of the scanner technology with high brilliance fiber lasers when laser dimpling and remote welding are executed in a successive order: the first one to realize gap spacers and the second one to weld together clamped sheets in zinc-coated steels. In particular, the substitution of the traditional mechanical dimpling with the laser dimpling is investigated in order to highlight the potentiality of a solution that is flexible, unaffected by tool wear and highly productive.

Deformation mechanics in single-point and accumulative double-sided incremental forming

Single-point incremental forming (SPIF) uses one small hemispherically ended tool moving along a predefined toolpath to locally deform a completely peripherally clamped sheet of metal such that the sum total of the local deformations yields the final desired shape of the sheet. While SPIF is characterized by greater formability than conventional forming processes, it suffers from significant geometric inaccuracy. Accumulative double-sided incremental forming (ADSIF) is a substantial improvement over SPIF in which one hemispherically ended tool is used on each side of the sheet metal. The supporting tool moves synchronously with the forming tool, therefore acting as a local but mobile die. ADSIF results in considerably enhanced geometric accuracy and increased formability of the formed part as compared to SPIF. In light of the aforementioned advantages of ADSIF as compared with SPIF, an investigation of the mechanics associated with the ADSIF process, which has yet to be presented in the literature, is warranted. The present study sheds light on the differences in deformation mechanisms between SPIF and ADSIF. Finite element analyses are performed to simulate deformation in the two processes, and a detailed analysis of the deformation history is presented. It is shown that the presence of the supporting tool in ADSIF elicits substantial differences in the plastic strain, hydrostatic pressure, and shear strains as compared to SPIF. The implications of these trends on the prevalent modes of deformation in ADSIF along with possible explanations for increased formability observed in the process arediscussed.

Comparison of the Identifiability of Flow Curves from the Hydraulic Bulge Test by Membrane Theory and Inverse Analysis

In the hydraulic bulge test, flow curves are determined by applying a hydrostatic pressure to one side of a clamped sheet metal specimen, which bulges freely into a circular cavity under the pressure. The pressure and various data such as bulge height, curvature and equivalent strain at the pole are recorded and used to calculate the flow curve of the specimen material using analytical equations based on membrane theory. In the determination of the flow curve, the elastic behavior of the specimen, the elastic-plastic transition and bending effects are neglected, and the flow curves calculated this way are affected by these simplifications. An alternative to this procedure is an inverse analysis, which proceeds by searching for a flow curve that minimizes the difference between computed and measured data, e.g. bulge height vs. pressure. An inverse analysis based on a finite element model takes into account elastic and bending effects but since it involves the solution of an optimization problem, it is not clear whether it yields more accurate results than membrane theory. The objective of this paper is to compare the ‘identifiability’ of a given flow curve from the bulge test by direct identification based on membrane theory and by inverse analysis with different objective functions to be minimized. Using a re-identification procedure, it is shown that an inverse analysis can improve the results of the direct identification if a suitable objective function is chosen.

RESEARCH ON THE FORMING ANGLE OF A1050-H14 ALUMINUM MATERIAL PROCESSED BY USING SINGLE POINT INCREMENTAL FORMING TECHNOLOGY (SPIF)

Single Point Incremental Forming - SPIF is the recent manufacturing process of metal sheet forming by drafting a non-cutting edge sphere-tip tool on a clamped metal sheet. The formability of metal sheet in SPIF is considered by the forming angle (ψ)- the maximum draft angle so that the material is not torn. The experimental research on A1050-H14 aluminum sheet on Bridge Port VMC500-16 CNC milling machine in C1 workshop of the HCMUT in order to find out the regression equations to predict the maximum forming angle in the relation with four most important technology parameters in SPIF: size of the step down z, forming feed vxy, spindle speed n, forming tool diameter d.

A CALCULATION OF POWER FOR FORMING METAL SHEET BY SPIF PROCESS

This paper attempts to represent a case of calculating of the energy power that is consumed by CNC milling machine when manufacturing via forming membrane metal sheet by SPIF (Single Point Incremental Forming), the recent manufacturing process of metal sheet forming by drafting a no cutting-edge spheric tip tool on a clamped metal sheet. The calculation is based on the disclocation, the crystal plasticity and the slip of lattices inside the structure of the deformed metal. In the while time there is a series of empirical species of 24 groups batch of workpieces that were also machined by CNC milling machine Bridge Port VMC500, CAD/CAM Lab., FME of HCMUT for checking this calculation on consumed power.

Numerical analysis of the influence of various factors on forming the limit of hydrostatic bulging for ductile materials

The influences of various factors on the limit strain of the hydrostatic bulging of a circular clamped sheet of ductile and damaged materials have been analyzed with the rigid-viscoplastic finite element method. These factors include strain hardening, strain-rate sensitivity, yield surface shape and the inhomogeneous distribution of cavitation. It has been shown that the average limit thickness strain for hydrostatic bulging increases linearly with both strain hardening exponent ( n) and strain rate sensitivity ( m) of material. For damaged material, the average limit thickness strain for the case that initial maximum cavitation locates at the periphery of circular sheet is much larger than that at the pole.