Die Radius Research Articles

State-of-the-art Review of Springback Behavior of Polymers

The spring-in and spring-back behavior of polymers is intricate and influenced by various process parameters and mechanisms, including interply slip, anisotropic thermal expansion, and crystallization, all of which can lead to residual stresses. Composite materials made of metal and polymer are being investigated by researchers as a promising alternative to monometallic materials due to their superior properties. However, the number of studies related to metal/polymer/metal laminates on the same topics is relatively limited. A comprehensive review study was carried out with a focus on research works that were conducted with the consideration of different process parameters, such as radius of die and punch, friction, and force applied by blank holder, in order to observe their impact on the springback behavior of polymers. Springback on polymer components depends on the accuracy of appropriate materials and the consideration of appropriate experimental strategies. However, due to their viscoelastic properties, polymers demonstrate distinctive springback behavior. Furthermore, when subjected to deformation, polymers experience a combination of elastic and viscous responses, resulting in immediate elastic recovery and time-dependent viscoelastic relaxation. This intricate behavior presents difficulties in precisely forecasting and managing springback. To enhance the control and optimization of springback in polymer-based manufacturing processes, it is essential to improve the understanding of polymer behavior under diverse loading conditions and to refine simulation techniques accordingly. This review focuses on springback prediction models specific to polymers.

A numerical model to analyse the under-tension-bending-unbending processes. Special analysis for determining the spring-back of TRIP 690 steel sheet

In this work, a numerical model has been developed to determine the stresses and deformations involved in the under-tension-bending-unbending processes of metallic sheet strips. The presented procedure allows us to evaluate the behavior in the die radius of a typical deep-drawing process. The procedure is based on a flexible numerical method that can be adapted to many other processes. Experimental results have been obtained from TRIP 690 + EBT steel sheets under different pure shear deformation states. The forces involved as well as the final deformations, or spring-back, after each forming process analyzed (bending, unbending over-unbending and stretching), were determined by introducing these experimental data into the ad-hoc created numerical method. The results obtained by the proposed model have been compared with finite element simulations (FEM) and contrasted with the experimental results. This allows the proposed procedure to be validated as a general method with more accuracy than FEM as permits the thickness of the sheet to be divided into a great number of points or elements.

Numerical and experimental analyzes of forming parameters of low carbon steel

Understanding sheet metal forming presses are important to reduce manufacturing costs. Thus, the best method of finding the optimum values of processing is by studying the effect of forming parameters on the behavior of formability, friction, and die radius. In this work, the deep drawing process of a low-carbon steel cup was studied and the significance of two important process parameters are investigated which are the friction coefficient and the radius of the die. The finite element method program, ANSYS, is used to study the effect of these parameters on forming load in the deep drawing process. The three ​​levels of friction coefficient are considered which are 0.08, 0.00, and 0.15, and three die shoulder radius of 4, 6, and 8 mm. The results show that the predicted behavior of the punch load coincided well with both experimental and practical behaviors and the confidence is exceeding 94%. The wrinkling defect is happening when using a high die radius, Rd=8mm although the punch load is low due to the increase in the surface area on the edge of the die.

Experimental Study on Removing Wrinkle Defect

Abstract: Manufacturing is the process of turning raw materials or parts into finished goods through the use of tools, human labor, machinery, and chemical processing. In Aerospace industry, the most commonly used manufacturing process is sheet metal forming processes that helps in manufacturing the parts for tons of known and unknown purposes. Sheet metal forming process is done on a press and the parts are formed in between two die. It involves reshaping a metal while it is still in its solid state. Example of sheet metal forming process are bending, stretch forming, deep drawing, etc. But in aerospace industry, their exists some parts which occurs wrinkling defect while forming process, which is because of uncontrolled material flow into the die radius and no holding for the blank during forming , needs to be rectified. It is one of the major defects in sheet metal forming processes. It may become a serious obstacle to implementing the forming process and assembling the parts, and severe wrinkling may leads to break the part

Effect of ultrasonic and low frequency vibrations on friction coefficient at die radius in deep drawing process

In the deep drawing process, the friction between sheet metal and die can be reduced by ultrasonic vibration (UV) or low frequency vibration (LFV), and the forming performance can be improved by the surface effect. In this study, a new friction test apparatus to determine the effect of both UV and LFV on the friction coefficient in the die radius region was designed and fabricated. The apparatus can realize UV and LFV conditions by switching the vibration exciters. New, simplified theoretical models with combined types of vibration were proposed, including flexible friction model and vibration superposed model. Using these models, the reduction mechanism of the macroscopic friction coefficient was investigated, and the corresponding mathematical expressions were derived. The theoretical results showed that the reduction ratio of the macroscopic friction coefficient (RMFC) is a function of only two parameters: the dimensionless relative velocity ratio and the wrap angle. Several groups of tests were conducted on three materials, stainless steel 304, brass CuZn40 and aluminium 1060, under UV and LFV conditions, and validated the theoretical results. Tests under UV conditions obtained higher RMFC values than those under LFV conditions, but caused more wear and adhesion.

Channel deformation of bilayer material using tool rollers: Part I-Springback

ABSTRACT In this two-part paper, the bilayer material is created by sandwiching the aluminium alloy and carbon fibre composite and then deforming through the conventional channel forming. In both aluminium alloy and polymer, the common problem is the springback due to their lower modulus of elasticity. To reduce the springback mechanically, the patented process is used in this work. In this novel manufacturing process, the die and punch radii are converted in rollers. These rollers can be fixed or rotated depending on the necessity. The first part of this paper involves investigating the bilayer material deformation and springback through the novel manufacturing process. For this the bilayer material was created with equal thickness of aluminium alloy and composite. In one sample the aluminium alloy was the top layer and, in another sample, the aluminium alloy material was bottom layer. From the results it was found that the top layer aluminium alloy composite material with punch roller rotating in counterclockwise and die roller rotating in clockwise direction shows lowest springback. The residual stress graph shows that the rollers rotation changes the stress patterns in the material which results in lower springback.

Impact of Die Radius in a Streamlined Die during Wire Drawing

The effects of die radius in a streamlined die on design factors, such as the distribution of strain, stress, temperature, damage, and drawing force of a wire, were investigated during wire drawing for a better understanding of streamlined die and improvement in drawing quality of the wire. A numerical simulation was performed with the die radius of the streamlined die. The behavior of the design factors of the drawn wire fabricated by the streamlined die was different from that of the conventional die and was highly dependent on the die radius. The different behaviors of the design factors with the die radius can be explained by the frictional work and redundant work of the wire with die angle. The temperature rise and drawing force were high at a greater die radius because of the great frictional stress and heating effect stemming from the high contact length of the wire and die. Meanwhile, the higher redundant work at the surface area with decreasing die radius led to higher strain inhomogeneity, effective stress, damage value, temperature rise, and drawing force due to the abrupt change in the metal flow of the wire stemming from the high die angle. After the optimization of several design factors with die radius, it was concluded that the optimum IDR values ranged from 0.14 to 0.18, indicating that a streamlined die with a radius of 70 to 90 mm was the most suitable in the present process condition. In particular, the damage value of the wire was reduced in this range of die radii compared to the conventional die.

G Sciences Experimental and Numerical Study on the Effect of Strain Hardening Characteristics on Curved Flaring Process of Pure Copper and Brass

An experimental and numerical study of tube curved flaring process was conducted to investigate the effect of strain hardening characteristic of material on the process using two metals that differ in strain hardening characteristic which are pure copper and brass (70-30) by using curved dies which have curvature ratio () of (6) and (12) and base radius of die (rd=24mm) and () is the radius of curvature. The experimental part was included experiments on specimens with an outer diameter of (39 mm) and a wall thickness of (2 mm). The expansion process was carried out for different expansion ratios that it was reached to about (32%). The results were showed that the strain hardening exponent of pure Copper more than Brass (70-30) and its value reached (0.54) for pure Copper and (0.49) for Brass (70-30). However, this paper concluded a study of the effect of strain hardening characteristics on the curved flaring process. It was found that the increasing of flaring ratio and relative axial displacement of the die through the specimen are caused increase in the relative forming stress, and its value is significant in expanded tubes with high strain hardening characteristic and it is about (0.77) in Brass and (1.42) in Copper. It also found that a little difference in the deformation of specimens' geometry which means that the deformation is not affected by the strain hardening characteristic and there is no significant difference in strain distribution. The study also included a numerical simulation using the finite element ANSYS program. The results obtained are compared with experimental data and showed good agreement.

Experimental and Numerical Study on the Effect of Strain Hardening Characteristics on Curved Flaring Process of Pure Copper and Brass

An experimental and numerical study of tube curved flaring process was conducted to investigate the effect of strain hardening characteristic of material on the process using two metals that differ in strain hardening characteristic which are pure copper and brass (70-30) by using curved dies which have curvature ratio ( ρ rd ) of (ρ rd =6) and (ρ rd =12) and base radius of die (rd=24mm) and (ρ) is the radius of curvature. The experimental part was included experiments on specimens with an outer diameter of (39 mm) and a wall thickness of (2 mm). The expansion process was carried out for different expansion ratios that it was reached to about (32%). The results were showed that the strain hardening exponent of pure Copper more than Brass (70-30) and its value reached (0.54) for pure Copper and (0.49) for Brass (70-30). However, this paper concluded a study of the effect of strain hardening characteristics on the curved flaring process. It was found that the increasing of flaring ratio and relative axial displacement of the die through the specimen are caused increase in the relative forming stress, and its value is significant in expanded tubes with high strain hardening characteristic and it is about (0.77) in Brass and (1.42) in Copper. It also found that a little difference in the deformation of specimens' geometry which means that the deformation is not affected by the strain hardening characteristic and there is no significant difference in strain distribution. The study also included a numerical simulation using the finite element ANSYS program. The results obtained are compared with experimental data and showed good agreement.

Investigation on the Crack and Thinning Behavior of Aluminum Alloy 5052 Sheet in Stretch Flanging Process

Stretch flanging is the important sheet metal-forming process which is widely used in automobile and aerospace sectors. The formability of sheet metal depends on various parameters such as material properties, geometry of the tool setup and process parameters. In the present work, effects of different die radius and sheet width on deformation behavior of sheet are studied by FEM simulation and experiments. The predicted FEM results are presented in the form of edge crack location and its propagation, crack length, forming load and strain distribution in sheet along the die profile radius. This study indicates that crack length increases with increase in the sheet width, while the crack length decreases with increase in the die radius. It is found that the crack propagation in stretch flanging process is affected by the strain distribution in sheet and this distribution of strain depends on many parameters. The crack initiates during deformation of the sheet at the die corner edge and propagates toward the center of the sheet along the die profile radius. Simulation results are compared with the experimental one in terms of crack length and variation in sheet thickness. FE simulation results are found in very good agreement with experimental results. Fractography study is also presented in terms of size, shape of the dimples along with their distribution on the fractured surface.

Study on Simulation of Stamping Process and Optimization of Process Parameters of Fender

In order to obtain the optimum technological parameters of fender forming, the finite element analysis software DYNAFORM is used to simulate the drawing process of fender in this paper. The orthogonal test is designed and completed. On the basis of the orthogonal test, Taguchi method is used to design the orthogonal inner table, and the SNR of each factor at each level is calculated. The results of Taguchi method are analyzed with variance analysis, and the adjustable influencing variables and influence factors on quality stability that affect the forming quality of the fender are obtained. Experimental optimization of the adjustable variables is carried out again to obtain the optimal combination of process parameters that affect the shaping quality of the fender. The optimal combination of process parameters is as follows: blank holder force is 120 kN, model clearance is 1.0 t (t represents sheet thickness), friction coefficient is 0.11, and radius of die is 6 mm. Finally, the experimental results show that the fender manufactured with this combination of process parameters has better performance.

Experimental analysis of AZ31B magnesium alloy sheet failure using punch stretching

The formability of magnesium alloy sheets at room temperature presents anisotropy in mechanical properties and difficulties in terms of occuring cracks easily, especially in regions with bend radius. In addition, the elastic spring-back is significant, leading to massive deviations from the desired shape. Recent studies conducted in this field lead to stretch forming magnesium alloys sheets using thermo-mechanical treatments at temperatures up to 400°C. The present study was conducted on 1 [mm] thick magnesium alloy AZ31B sheet to investigate its formability when stretching at room temperature by several dies with different radius. The stretching process was conducted on a hydraulic press, using 3D printed PLA dies with the following values: R180, R320, R540, R720, R900 and R1080. The samples were stretched until fracture to highlight the fracture force, distance to fracture, deviation from the die radius and bend angle.

Experimental and FE analysis on spring-back of copper/aluminum layers sheet for a L-die bending process

This paper is a conduct of experimental tests to investigate different effective parameters of a UNS C10100 copper/aluminum 1100 spring-back on a two-layer L-die bending sheet through finite element simulations. The parameters are the radius and clearance of die, sheet length, thickness of each layer, different lay ups, and sheet annealing. The paper shows that the spring-back decreases with the reduction of the die clearance and radius, similar to the behavior of single-layer sheet and with the increase of the sheet length. The outcome displays a contradiction with ‘no significant effect’ in the single-layer sheets, previously published in other papers. Furthermore, the thicknesses of copper and aluminum are important roles to evaluate spring-back; however, there is no certain rule to decrease or increase the spring-back through changing the thickness of each layer. Moreover, this work shows the effects of stacking sequence of aluminum and copper layer on the spring-back, because of the different natural axis in each stacking sequence and also different ultimate strength of each layer. Finally, it is concluded that annealing heat treatment significantly reduces the spring-back, where the intermetallic bond hardness in the interface of Cu/Al layers and spring-back increases with the rise of annealing temperature.

FEM-based assessment of wear of stamping die

In sheet metal forming industry, surface damage and wear such as adhesion and ploughing of metallic sheet, is a well-known problem which reduces the tool life and quality of drawn elements. Surface defects are the consequences of wear and they accelerate the galling process. The knowledge of places particularly endanger wear allows appropriate design of tools. In this paper, an investigation that focused on the finite element-based analysis of wear of stamping tool for forming an axisymmetric drawpiece has been reported. The analyses were carried out for deep-drawing quality steel sheet with a sheet thickness of 2 mm. The basic mechanical parameters of the sheet tested are determined in uniaxial tensile tests. The analyses performed using Marc/Mentat program for nonlinear analyses take into account the strain hardening phenomenon of sheet material and different values of friction coefficient. The implementation of an Archard’s wear model in the numerical simulation proved the possibility of tool wear simulation in sheet metal forming. As a result of the conducted tests, the places of the stamping die potentially exposed to quick wear were determined. It was found that the most exposed region on accelerated wear is the upper part of the die radius.

Experimental investigation of tool-sided surface modifications for dry deep drawing processes at the tool radii area

Abstract In conventional deep drawing processes lubricants are applied to reduce friction and wear. Demands for increased sustainability, environmental protection and resource efficiency motivate the realization of lubricant-free forming processes. The direct tool-workpiece contact during dry deep drawing leads to changed tribological conditions. Especially in the areas of increased normal and shear stresses, such as the die radius, the dry contact causes an increased risk of wear and damage to the sheet surface. A well-known approach to face the challenges of dry deep drawing of steel sheets and aluminum alloys is the application of amorphous carbon based coatings on the tool surfaces. Within this study the tribological behavior of conventional and modified tool surfaces at the critical radii area is investigated with a strip bending rotation test. In this test, the friction coefficient is determined based on the relative movement between a rotating test cylinder and a sheet-metal strip bent in a die. For the tribological tests the sheet materials AA6014, AA5182 and zinc coated DC04 are applied. The modification of the tool sided surface was achieved by applying ta-C and a-C:H coatings to the test cylinder. In addition to tests with coated surfaces, tests with uncoated tools are carried out for reference. By analyzing the resulting friction coefficients for the different sheet materials, the suitability of ta-C and a-C:H coatings for dry deep drawing processes is evaluated comparatively. In order to investigate cause-effect relations as well as wear mechanisms, the tool and workpiece surfaces are characterized before and after testing.

Experimental investigation of non-isothermal deep drawing of DP600 steel

To increase the limiting drawing ratio (LDR) in deep drawing, experiments are conducted on DP600, IF, and HSLA steels. The flange region of blank is heated up to temperatures in the warm range by inductance heating. During heating, the central portion of blank is cooled by water to prevent the reduction of the strength of the material in the central region. The temperature increase of flange region is observed by two infrared sensors focusing on two different points, one on the blank rim and the other near the die radius. An intensive cooling by cold water is applied to the bottom side of a blank during deep drawing. Increases up to 25.58% on LDR are obtained. There is no significant change in the microstructure of the material due to warm forming. Material characterization is obtained by a Gleeble 3800 thermo-mechanical testing machine for the temperature range 150–300 °C.

A theoretical model of the inversion tube over a conical die

As an important impact energy absorber and a way to produce double-wall tubes, the inversion of the metal tube over a conical die is investigated in this study. Adopting the deformation profile inspired by FEM simulations, a theoretical model is proposed assuming the energy is dissipated by bending and compression in the meridional direction, and expansion in the circumferential direction. FEM simulations with a large range of geometrical parameters are used to validate the theoretical model, and results show that both the compressional force and the final circular radius of tube predicted by the theoretical model are quite accurate. Then, the energy dissipations along the axis of the tube by various mechanisms are analyzed in detail, and it is identified that the tube deformation in the thickness direction is the major reason of the current model’s deviation. Besides, the influence of the die radius, the friction between die and tube, as well as the dynamic effect are discussed.

A Comparative Study on Formability of the Third-Generation Automotive Medium-Mn Steel and 22MnB5 Steel

Third-generation advanced automotive medium-Mn steel, which can replace 22MnB5 steel, was newly developed to improve the lightweight and crashworthiness of automobile. Studies on the formability and simulation method of medium-Mn steel have just been initiated. In this study, finite element simulation models of square-cup deep drawing were established based on various material property experiments and validated by experiments. The effects of blank holder force (BHF), fillet radii of tools (die and punch) on the maximum drawing depth (MDD), thickness distribution of the formed products, and the microstructure before and after forming were investigated and compared with those on 22MnB5 steel. Results show that the MDD of the two steels decreased with increased BHF but increased with the fillet radius of punch; however, the fillet radius of die showed no significant effect on the MDD for both steels. Compared with hot-formed 22MnB5 steel, the martensitic transformation of the hot-formed medium-Mn steel is rarely influenced by the process parameters; thus, it holds the complete, fine-grained, and uniform martensitic microstructure. Moreover, the medium-Mn has better formability, lower initial blank temperature, and smaller impact of BHF and fillet radius of tools on the hot-formed product. Thus, a theoretical basis for the replacement of 22MnB5 steel by medium-Mn steel in hot forming process is provided.

Effect of die width on spring back of electrogalvanized CR4 steel during air bending

This study is an attempt for analyzing the effect on spring back due to changes in the die width during air bending of electro-galvanized CR4 steel. A universal testing machine, enabling recording of bending force and controlling of punch travel was used for conducting the experiments. A flexible die set with die width Wd = 40mm, Wd = 60mm and Wd = 80mm was used whose die width can be changed by simply changing a distance block. Die radius, punch radius and punch speed were kept constant. Galvanizing was done by electrodeposition method using alkaline non-cyanide baths. Different thickness of electro-galvanizing, Tg = 0 µm, 4 µm, 7 µm, and 10 µm were achieved by changing the timing of electrodeposition. An approach to vary one factor at a time was employed. Angles were measured by using optical profile projector and graphics. The Graphical method was used for analyzing the spring back. It has been witnessed that spring back increases with the increase in width of die for every punch travel and for non-galvanized as well as galvanized steels of different galvanizing thicknesses. An increase in spring back was observed when the galvanizing thickness was increased. The results are important for the tool engineers and process shop engineers for tool design and process control.

Wear characteristics of die surface in deep drawing of stainless steel 304 by using finite element simulation

The characteristics of adhesive wear of TiN coating in drawing process by using finite element method were carried out to investigate the effects of drawing angles and sliding velocities of punch to explained wear index. Bending radius of die was used to increase the contact pressure between stainless sheet and TiN coating surface. Three sliding velocities (0.5, 1 and 5 mm/s) were studied each bending angle between (0O to 90O) by keeping the hardness of material coating to 24 GPa (HV.0.05). The results showed that the wear index were decreased with drawing angle but sliding speed of punch was not affected in slightly speed.