Hole-flanging Process Research Articles

A critical review on hole-flanging process

A critical review on hole-flanging process

Tool path planning for hole-flanging process using single point incremental forming

Hole-flanging is a process used to create flanges around holes in sheet metal parts. It traditionally relies on dies and punches, posing cost and time challenges for small quantities or prototypes. While Incremental forming does not require dedicated sets of tools and dies, and it provides more flexibility and adaptability with enhanced formability, and emerged as a better alternative to conventional press forming. However, precise and efficient tool path planning is essential to achieve high-quality hole-flanged components. Precise toolpath planning is one of the crucial and important part in designing of hole flanging process for both through numerical simulations and experiments. The objective of the present work is to generate tool paths as well as associated G-codes using MATLAB code for different geometries of incremental hole flanging process using SPIF. Six different geometries of hole flanges were considered to generate tool path using MATLAB code. The proposed methodology was successfully applied for different shapes of hole flanges. Since the proposed methodology provides unified programming technique in the current MATLAB environment, which performs dual duties, creating toolpath coordinates against time data and outputting a G-code file and it saves computational time and programming efforts. Hence, proposed methodology is found to be better for incremental hole flanging in contrast to previously existed methodology for development of toolpath for incremental forming cases. Thus, it was concluded that this proposed methodology can be effective for capturing any intricate shapes for incremental hole flanging. You should leave 8 mm of space above the abstract and 10 mm after the abstract. The heading Abstract should be typed in bold 9-point Arial. The body of the abstract should be typed in normal 9-point Times in a single paragraph, immediately following the heading. The text should be set to 1 line spacing. The abstract should be centred across the page, indented 17 mm from the left and right page margins and justified. It should not normally exceed 200 words.

Effect of meshing technique and time discretization size on thickness strain localization during hole-flanging simulation of DP980 sheet at high strain level

In the simulation of the hole-flanging process, many had reported that the effect of mesh sensitivity on strain localizations is insignificant. In this study, mesh layouts including the number of elements along the hole circumference (CD), element sizes in radial directions (R1) and the time discretization (or increment) sizes (T) are varied in the 3D FE simulation of 10-mm hole flanging process of DP980 thin sheets using a conical punch. Its effect on wall thickness distributions and forming load profiles are investigated. Also, the effect of punch surface meshing techniques i.e., analytical and discrete rigid on the distributions is investigated. The simulation results showed that the largest % wall thinning range around the expanded hole edges for punch displacement, S = 15 mm and 20 mm are 25.8–29.2% and 33.3–64.2%, respectively. The load-displacement curves during the continuous hole expansion are not linear for R1 ≥ 0.5 mm. For CD70 & R1 = 0.1 mm, the increase in T values from 0.1 s to 1.0 s has significantly increased the total simulation time by 25% due to the convergence problems. The automatic time increment mode in each step at T = 1.0 s has failed to reduce the total simulation time. The discrete rigid punch surface produces more concentrated wall thickness distributions than the analytical one, leading to higher amount of wall thinning, particularly for high S values. Since the model stiffness reduces with decreasing mesh size. It is recommended to match the simulated peak load with the experimental peak under the instability condition with a smooth hole e.g., a laser cut hole to determine the appropriate meshing method for the mesh sensitivity study. With that, the stiffness of the simulation model is calibrated with the experiment.

Modelling and evaluation of the post-hardness and forming limit diagram in the single point incremental hole flanging (SPIHF) process using ANN, FEM and experimental

In the single point incremental hole flanging (SPIHF) process, a sheet material with pre-cut holes is deformed using the SPIF technique to generate a flange, making it an effective approach for low volume manufacturing and quick prototyping. In the case of the SPIHF technique, the post-forming hardness property, the forming limit diagram (FLD), and spring-back phenomena are not completely evaluated. To this end, this paper employs experimental investigation and numerical validation to analyse the impact of SPIHF process parameters like tool diameter, feed rate, spindle speed, and initial hole diameter on these aspects for the truncated incrementally formed components made from AA1060 aluminium alloy and DC01 carbon steel. The plasticity behaviour of both sheet metals was simulated using the Workbench LS-DYNA model and ANSYS software version 18. Additionally, Cowper Symonds power-law hardening was added to the model to account for material properties. The average post-hardness of AA1060 and DC01 was evaluated using an SPIHF prediction model based on the performance of an artificial neural network (ANN). This ANN model was developed using a feed-forward back-propagation network trained using the Levenberg-Marquardt approach. The ANNs 4-n-1 were created by varying the transfer functions and the number of hidden neurons. Greater spindle speed and bigger pre-cut holes were shown to significantly increase the post-formed hardness of the truncated components, whereas the converse was seen when using a higher feed rate and a larger tool diameter. In addition, the FLD and spring-back improved dramatically with larger hole diameters. Employing correlation coefficient (R) and mean square error (MSE) as validation measures, it was shown that the established ANN models accurately predicted the SPIHF process response. Both the DC01 and AA1060 neural network models with a 4-8-1 network architecture performed very well, with MSE and R values of 0.0000105 and 1 for DC01 and 0.02613 and 0.99982 for AA1061.

Effect of ironing on forming characteristics in the Lorentz-force-driven hole flanging process

Ironing that achieved by reducing the clearance between forming tools have been proved to be able to generate high collar, regular geometry and good formability in conventional flanging process. In this paper, the effect of ironing on flanging characteristics during the Lorentz-force-driven (LFD) hole flanging process were investigated with the use of 5182 aluminum alloy. The ironing phenomenon in the LFD flanging process were realized by decreasing the diameter of die and keeping the punch diameter constant. To reveal the formation mechanism with or without ironing in this high-speed process, the elastoplastic finite element simulation model was established. Typical features in the final profiles, including junction ridge, spring-back, tip inclination, that determined by three critical clearance-thickness ratios ( R cc1 , R cc2 and R cc3 ) were analyzed. Especially, the evolution of spring-back and tip inclination with respect to the varying clearance-thickness ratios ( R c ) were discussed in details. According to three R cc values, ironing identification and ironing extents (mix-ironing and pure-ironing) separation could be achieved at the same time. Based on the analysis of radius, wall and tip in the flanged part, a height calculation method was proposed for the replacement of simulation in flanging cases with R c lowered than R cc2 . The comparison with experimental heights proved the feasibility of prediction formula.

Reduced order modelling for spatial-temporal temperature and property estimation in a multi-stage hot sheet metal forming process

A concise approach is proposed to determine a reduced order control design oriented dynamical model of a multi-stage hot sheet metal forming process starting from a high-dimensional coupled thermo-mechanical model. The obtained reduced order nonlinear parametric model serves as basis for the design of an Extended Kalman filter to estimate the spatial-temporal temperature distribution in the sheet metal blank during the forming process based on sparse local temperature measurements. To address modeling and approximation errors and to capture physical effects neglected during the approximation such as phase transformation from austenite to martensite a disturbance model is integrated into the Kalman filter to achieve joint state and disturbance estimation. The extension to spatial-temporal property estimation is introduced. The approach is evaluated for a hole-flanging process using a thermo-mechanical simulation model evaluated using LS-DYNA. Here, the number of states is reduced from approximately 17 000 to 30 while preserving the relevant dynamics and the computational time is 1000 times shorter. The performance of the combined temperature and disturbance estimation is validated in different simulation scenarios with three spatially fixed temperature measurements.

Forming a Flanged Hole When Quenching Press-Hardened Steel for Mechanical Fastening

The recent stringent regulations on vehicle safety and reducing CO2 emissions have led to a continuous increase in the application of press-hardened steel (PHS) in automobiles. Similar to other high-strength steels, assembling PHS components using the common welding techniques employed in automotive production lines is significantly difficult because of the surface coating layers and the additives within. This difficulty in post-processing, attributed to its high strength, also limits the mechanical fastening of PHS components. Therefore, this study aims to develop a process for forming a structure enabling mechanical fastening by sequentially applying piercing and hole-flanging operations during the hot stamping process. Our experimental apparatus was designed to perform the hole-flanging operation after the piercing operation within a single stroke at a specific temperature during the quenching process of PHS. At high temperatures of 440 °C or higher, the hole-flanging process was conducted in a direction opposite to that of the piercing operation for creating the pilot hole. An extruded collar with a height of 8.0 mm and a diameter of 17.5 mm was achieved, which is hole expansion ratio(HER) of 82.5%.

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.

Experimental studies on incremental hole flanging of steel sheets

ABSTRACTIncremental Hole-Flanging (IHF) process has various applications in rapid prototyping and low volume production of conical and vertical flanges in sheet metal parts. Therefore, understanding mechanics and failure strategies in IHF is very important for successful forming without cracks. In this paper, Deep Drawing (DD) steel blanks with pre-cut hole of 40 and 70 mm diameter are used for multistage conical hole flanging. Conical hole flanges are formed on CNC milling machine with starting angle 60° to final angle 90° with an increment of 10°. The experimental results showed a crack at 80° flange angle with the blank of 40 mm pre-cut hole. The blank with 70 mm-pre-cut hole has no such crack behaviour even at 90° flange angle. The paper also discusses the variation of flange height, surface roughness and forming forces in IHF of DD steel sheets.

Pengaruh Parameter Proses Incremental Backward Hole-Flanging terhadap Ketebalan Kerah pada Alumunium 1050A

Conventional hole-flanging process in a small batch is sometimes costly or almost impossible due to the variety of the product profile. Recent studies showed that modern manufacturing was developed to overcome the limitation of the conventional hole-flanging process. Incremental backward hole-flanging (IBHF) was one of the strategies that developed to overcome this particular limitation. The main objective of this research was to investigate the influence of IBHF process parameters toward collar thickness of the product. It enables to measure the impact and behavior of each process parameters, i.e., forming speed, axial and radial forming step size toward the particular response parameter. The result showed that axial and radial forming step size was the main influence and the forming speed has a slight effect towards collar thickness. The behavior of each parameter was increased forming speed and radial forming step size would decrease collar thickness, whereas increased axial forming step size would increase collar thickness.

Determination of the Hole-flangeability for thin Sheets

Sheet metal stretching is one of the most frequently applied sheets forming operation in the industry. Hole flanging is a common sheet forming operation to produce structural sheet metal components. Flanges are used for appearance, rigidity, hidden joints, and strengthening of the edge of sheet metal parts. Trial-end-error is the most common approach for tooling and process design in flanging operations. This paper presents some experimental results of hole-flanging process performed on flat deep drawing steel sheets with circular hole drilled or punched in the centre of blank. Three punches of different geometry i.e. cylindrical, hemispherical and conical were used in this experiment. The effect of both the punch geometry and material mechanical parameters (especially strain hardening and plastic anisotropy) on the limit expansion of the hole, limit strain dependence on hole performing technology as well as sheet thickness distribution along collar formed was determined.

Plastic anisotropy effect on forming kinematics of the hole-flanging process

The plastic anisotropy effect on the forming kinematics of the hole-flanging process was experimentally and numerically analyzed. Firstly, the heterogeneity of the flange thickness and the flange height along the circumferential direction were distinguished experimentally. The measurements were performed from different flanges obtained under various process conditions. In order to explain the experimental results, a 3D finite element model was developed for the different conditions. The zone of the flange in contact with the punch and the zone free from any contact with the tools were distinguished for hole-flanging both with and without ironing. The variation of the contact zone with the punch and the normal contact force were identified along the circumferential direction for selected punch displacements. The profiles of deformed flange obtained on rolling and transverse directions were also characterized. The dependence to the sheet orientation of the clearance thickness ratio (Rcc) which indicates the occurrence of ironing was finally studied. Accordingly, the experimental observations were justified. In some cases, numerical results were validated by experiments. A 0.8-mm 1000 series aluminum alloy was used as typical material.

Optimization of Hole-Flanging by Single Point Incremental Forming in Two Stages.

Single point incremental forming (SPIF) has been demonstrated to accomplish current trends and requirements in industry. Recent studies have applied this technology to hole-flanging by performing different forming strategies using one or multiple stages. In this work, an optimization procedure is proposed to balance fabrication time and thickness distribution along the produced flange in a two-stage variant. A detailed analytical, numerical and experimental investigation is carried out to provide, evaluate and corroborate the optimal strategy. The methodology begins by analysing the single-stage process to understand the deformation and failure mechanisms. Accordingly, a parametric two-stage SPIF strategy is proposed and evaluated by an explicit Finite Element Analysis to find the optimal parameters. The study is focused on AA7075-O sheets with different pre-cut hole diameters and considering a variety of forming tool radii. The study exposes the relevant role of the tool radius in finding the optimal hole-flanging process by the proposed two-stage SPIF.

Evaluation of the feasibility of the hole-flanging process using a multiple criteria method

Software dedicated to simulating the hole-flanging process has been developed for the sheet metal forming profession. This software innovates by providing companies in this sector with an alternative, which is easier and less expensive than existing, more general, software. The hole-flanging process can be applied in various ways. The software uses the most known method in the profession to manufacture a flanged hole, which is based on expanding a hole with or without ironing. This study focuses on evaluating the feasibility of the hole-flanging operation. Three fracture criteria have been used for this purpose: Rice & Tracey, Latham & Cockroft and the Hole Expansion Ratio (HER). The first two criteria apply an uncoupled approach and the values of the criteria are compared with the corresponding thresholds post-process. The third criterion is used either as input data or as a test to determine thresholds for the first two criteria. The fracture thresholds are determined from experimental trials on press and from hole-flanging simulations based on the same configurations. Various hole-flanging trials with or without ironing have been carried out. Comparing the results of experimental trials and simulations highlights similar flange geometries and forming forces. The simulation shows that the locations of fracture areas on the flange are accurately modelled. However, differences appear regarding the sensitivity of the criteria to the process parameters. In particular, the fracture thresholds for the criteria may vary according to whether the flanging is carried out with clearance or with ironing. For this reason, the software allows the user to view the two criteria and choose the best one for their configuration. The HER test is used to determine thresholds for the fracture criteria and seems to be suitable for subsequently evaluating the feasibility of new flanging configurations.

Surface Analysis of Uncoated and PVD Coated Punch at the Hole-Flanging Process

This paper researches the surface condition and wear on the hole-flanging punch when producing a flanged Ø7 mm hole in a steel strip S355J2 + N (1.0577) with a thickness of 3 mm. The hole was flanged by a punch with a defined geometry known as a tangent ogive and described via a caliber radius head (CRH) ratio. During the process, wear of the punch made of hardened tool steel 1.3343 appeared after 20,000 strokes. Thus, a multipurpose coating TiCN-MP deposited via Lateral Rotating Arc-Cathode technology was applied on the punch to extend the punch lifetime. The coated punch was polished to remove droplets after deposition process. By applying TiCN-MP coating, 120,000 strokes were applied to reach the same wear as for the uncoated tool steel. The surface of the punch made of the hardened tool steel for uncoated and PVD coated conditions was researched by scanning electron microscopy after wear, and an energy dispersive X-ray (EDX) analysis was done to identify components of bonded material. In addition, the normal pressure on the punch active surface was studied via a numerical simulation of the hole-flanging process. The position of the high normal pressure is well correlated to the position of the adhesive wear for the uncoated and coated punches.

THE INFLUENCE OF PROCESS PARAMETERS TOWARD COLLAR HEIGHT ON INCREMENTAL BACKWARD HOLE-FLANGING PROCESS

Abstract The experimental study of the influence of process parameters towards collar height on incremental backward hole-flanging (IBHF) process with aluminium plate workpiece was presented in this paper. The effect of process parameters toward collar height which produced by IBHF process was investigated. Experiments were performed with a CNC machine, a 30o conical forming tool, and aluminium plates. The process parameters are feed speed with two levels, radial forming step size with three, and axial forming step size with three levels. Some parameters were kept constant, i.e., spindle speed, initial hole diameter, final hole diameter, and conical forming tool diameter. Digital Vernier caliper was used to measure the height of the collar. Experimental results of IBHF process have shown that the feed speed (vf) parameter has no effect toward collar height. Increased radial forming step size (Δx/y), increased the collar height also. Increased the axial forming step size (Δz) reduced the collar height. Keywords: hole-flanging, incremental sheet metal forming, incremental backward.

Determination of an adequate geometry of the flanged hole to perform formed threads

In this work, the flanged hole is adopted as a potential solution to increase the number of formed threads in the case of sheet metal part. To achieve an adequate initial tap hole for tapping process, the final shape of the flanged hole was analyzed by 2D finite element (FE) simulations. An adequate range of the clearance j between the die and the punch of the hole-flanging process was identified for which formed threads are performed on a vertical flange with more substantial and uniform thickness as well as an important height. To ensure that the selected flange is free from fracture, 3D FE model was developed using Gurson-Tvergaard-Needleman coupled approach. Experiments were carried out in order to validate the numerical results and to analyze the geometry of formed threads performed on the selected flanged hole and the drilled hole.

Preliminary investigation on homogenization of the thickness distribution in hole-flanging by SPIF

A drawback of the hole-flanging process by single-stage SPIF is the non-uniform thickness obtained along the flange. Multi-stage strategies have been used to improve it, however they increase notably the manufacturing time. This work presents a preliminary study of the tool paths for a hole-flanging process by SPIF in two stages. An intermediate geometry of the piece is proposed from the analysis of the thickness distribution observed in previous single-stage process. A simple optimization procedure is used to automate the intermediate part design, the NC code generation for the tool path and the validation of the optimal forming strategy by means of FEA.

A study on sheet metal hole-flanging process

Hole-flanging is a manufacturing process which is used to form flanges around holes by using sheet metal. A brief and concise review of the contributions made by the previous researchers in the area of hole-flanging process has been presented. Steel sheet material and aluminum alloys are used by researchers for hole flange forming. FEM modelling of hole-flanging is carried out by employing axisymmetric conditions. Meshing of the work piece is done by using axisymmetric quadrilateral elements. Experimental set-up and tools utilized in formation of hole flanges are presented and discussed. Results are presented in terms of variation of distribution of thickness along flange wall through conventional hole-flanging and incremental forming technique. Incremental forming techniques with different forming strategies is found to be more accurate, less complicated and better means of hole flanging in comparison to conventional forming techniques.

Analysis of geometrical parameters and occurrence of defects in the hole-flanging process on thin sheet metal

Geometrical parameters of the flange were analyzed in the conventional hole-flanging process on thin sheet metal of 0.8mm by varying both the initial hole diameter and the clearance-thickness ratio. An elastic-plastic finite element (FE) model with normal anisotropy assumption was performed together with experiments and analytical solutions. The excessive thinning generated by ironing was distinguished and the occurrence of a non regular geometry was identified by the exam of the final shape. The influence of the initial hole diameter on the state of the flange was also investigated. Therefore, the occurrence of defects such as necking and tearing were predicted by considering the uniform strain and the thickness of crack initiation under the simple tensile test, respectively. Practical diagrams were proposed to exploit the geometrical and forming parameters as well as the state of the flange. Good agreement was shown between numerical simulations and experiments.