Hydroforming of sheet metal

This study proposes a novel technique for increasing the limiting drawing ratio (LDR) in the deep drawing process. This work uses "triple-action forming (TAF)" as a new technique to enhance LDR, achieving an LDR of 2.40 for stainless steel JIS and SUS304. The TAF consists of three sequential steps with a constant blank holder force of 3 kN. The first step involves deep drawing with a punch diameter of 30 mm. In the second step, we used a smaller punch diameter of 25 mm. The third step is going deep down with a punch diameter of 30 mm until the end of the die cavity. TAF reduces the intensity of material flow during deep drawing, which results in a delay in cup wall stretching and fracturing as a result of the reduced friction. The TAF approach offers a notable edge over alternative deep drawing techniques, such as multi-step deep drawing and temperature-based forming, due to its ability to effectively enhance the LDR. These process parameters are determined before experimentation through precise finite element simulation. Validation is shown through deep drawing experiments on JIS and SUS304, conducted using FE simulations with the Y-U model and Yoshida 6th yield function.

The sheet metal forming operations process involves the Male (Punch) and the female (Die). The procedure is of sheet metal deformation due to the relative movement between the punch tool and the sheet, an interaction that generates friction forces between the elements. The formability of AISI 304 stainless steel sheets is examined in this study using the Nakajima test specimen. The Nakajima test is a widely used method for evaluating the formability of sheet metals. The forming limit diagram (FLD) of AISI 304 steel sheets is experimentally determined in this work using the Nakajima test. Additionally, the FEA HyperForm Radioss software is used to simulate the forming process and validate the experimental results. The effects of various process parameters, such as punch speed and lubrication, on the formability of AISI 304 steel sheets are also investigated. The results of this study offer valuable insights into the formability of AISI 304 steel sheets, which can be utilized to optimize the sheet metal forming process.

To increase the process stability and improve the product quality in the sheet hydroforming with die process, it is crucial for identifying and analyzing the dependence of forming pressure on process parameters. The effects of process parameters (blank holder force, frictional condition) on the forming fluid pressure were thoroughly studied experimentally. The main objective is to establish a relationship between the forming fluid pressure and several factors such as blank holder force and friction between die and sheet. The results demonstrate that the maximum fluid pressure increases with increasing blank holder force and friction. Finally, this relationship aims to support calculations and design data and provide control during the SHF-D process.

At present, sheet metal forming is gaining importance in the
manufacturing sector and this process is essentially used to produce
various engineering components having applications in railway cars,
automobile bodies, construction, farm equipment, office furniture, lighting
equipment, computer peripherals, medical appliances, etc. The formed
component having the best design, superior quality and an aesthetic look
is the demand of the present sheet metal industry. The present needs
of the sheet metal manufacturing industry are to optimise the forming
operations.
Deepdrawing is one of the sheet metal forming operations widely
used in manufacturing industries for producing cup-shaped components.
In this process, sheet metal placed between the die and blank-holder on
its periphery can be drawn into the die for forming into a cup-shaped
component. This process is extensively used for the manufacture of cups,
cans and other similar types of products. The deep drawing process is
influenced by geometric parameters as well as process parameters. Its
geometric parameters include Die Shoulder Radius (DSR), Punch Nose
Radius (PNR) and clearance between punch and die. The Blank Holder
Force (BHF), coefficient of friction, punch speed and blank temperature
are the process parameters. All these parameters have their influence on
the quality of the cup produced. A literature search reveals that PNR, and
BHFaresignificantly influencing tool design based parameters of the deep
drawing process. In any deep drawing process uniform wall thickness of
the drawn cup is the desired quality characteristic. From the literature, it
is also found that these parameters vary in their respective ranges. Experiments are conducted using DoE to optimise the
combinations of geometric and process parameters and levels that would
give minimum variation in the thickness of the cup produced in the deep
drawing process. To develop optimised deep drawing facilities using
Design of Experiments (DoE), the ranges for highly influencing parameters
are fixed after a thorough study of literature. The tool setup is designed for
optimization of highly influencingparametersusingDoEbasedonTaguchi
technique. The parameter ranges for highly influencing parameters fixed
are PNRfrom 5.5 to 10.5 mm, DSR from 5.5 to 10.5 mm and BHFfrom3
to 7 kN. The uniform thickness of the drawn cup is considered as output
characteristic and the variation in cup wall has to be as minimum as
possible. The three level values fixed for these parameters are 5.5 mm,
8 mmand10.5 mm for PNR; 5.5 mm, 8mm and 10.5 mm for DSR and
3 kN, 5kNand7kNforBHF.
Subsequently, experimental tests are conducted using L9
Orthogonal Array (OA) for optimisation of the process setup. Following
the DoE procedure, nine experiments are performed according to L9 OA
instead of conducting all the possible 27 experimental tests. During the
experimental tests, Aluminium alloy AA6111 blanks are considered as the
test material having 130 mm diameter and 0.9 mm thickness. In every test,
the thickness readings are measured at nine different points, radially from
the edge of the flange to the centre of a cup at the bottom. Considering
"Nominal is the Best" (NB) characteristic, The Signal to Noise (S/N)
ratios are determined using Qualitek- 4 software. The application of this
Taguchi based DoE software for optimisation of the deep drawing process
indicated the optimal values for the parameters considered, and these are
PNRof5.5 mm,DSRof5.5mmandBHFof7kN.Thestatistical method
Analysis of Variance (ANOVA) is applied to estimate the contribution of
each optimal parameter to obtain a minimum variation in the thickness of
the cup produced and it is found that PNR, DRS and BHF contributions
are 33.736 %, 07.140 % and 54.315 % respectively

Experiments are conducted using DoE to optimise the
combinations of geometric and process parameters and levels that would
give minimum variation in the thickness of the cup produced in the deep
drawing process. To develop optimised deep drawing facilities using
Design of Experiments (DoE), the ranges for highly influencing parameters
are fixed after a thorough study of literature. The tool setup is designed for
optimization of highly influencingparametersusingDoEbasedonTaguchi
technique. The parameter ranges for highly influencing parameters fixed
are PNRfrom 5.5 to 10.5 mm, DSR from 5.5 to 10.5 mm and BHFfrom3
to 7 kN. The uniform thickness of the drawn cup is considered as output
characteristic and the variation in cup wall has to be as minimum as
possible. The three level values fixed for these parameters are 5.5 mm,
8 mmand10.5 mm for PNR; 5.5 mm, 8mm and 10.5 mm for DSR and
3 kN, 5kNand7kNforBHF.
Subsequently, experimental tests are conducted using L9
Orthogonal Array (OA) for optimisation of the process setup. Following
the DoE procedure, nine experiments are performed according to L9 OA
instead of conducting all the possible 27 experimental tests. During the
experimental tests, Aluminium alloy AA6111 blanks are considered as the
test material having 130 mm diameter and 0.9 mm thickness. In every test,
the thickness readings are measured at nine different points, radially from
the edge of the flange to the centre of a cup at the bottom. Considering
"Nominal is the Best" (NB) characteristic, The Signal to Noise (S/N)
ratios are determined using Qualitek- 4 software. The application of this
Taguchi based DoE software for optimisation of the deep drawing process
indicated the optimal values for the parameters considered, and these are
PNRof5.5 mm,DSRof5.5mmandBHFof7kN.Thestatistical method
Analysis of Variance (ANOVA) is applied to estimate the contribution of
each optimal parameter to obtain a minimum variation in the thickness of
the cup produced and it is found that PNR, DRS and BHF contributions
are 33.736 %, 07.140 % and 54.315 % respectively

maximumpunchload is linearly proportional to the blank diameter for
all successfully drawn cups and remains constant for all oversized blanks
forming into crack induced/failed cups.
As the maximumpunch load is linearly proportional to the blank
diameter, a newconceptknownasarapidmethodofdeterminationofLDR
using only three blanks of different sizes gained significance. In the rapid
determination method, the LDR values for Aluminium alloy AA6111 and
Copper C11000 material are found. Experiments are conducted with three
different size blanks, i.e., two undersized blanks of different diameters
for determining the linearity of the punch load and one oversized blank
for finding the maximum forming load at which fracture takes place.
The LDR results found in the traditional method involving testing of
several different sized blanks and the rapid method using only three
different blank sizes are compared. The results found through the rapid
determination method of LDR are in close agreement with the traditional
method.
Further, simulation tests are conducted for Aluminium alloy
AA6111 at 30 oC temperature for confirmation of experimentally found
LDRat 30 oCtemperature. The deep drawing model is constructed using
CATIA V5 and simulations are performed using PAM-STAMP 2G®, a
simulation software. It has been observed that the experimental results at
30 oC temperature for Aluminium alloy AA6111 are in close agreement
with simulation results obtained at 30 oC temperature.
It is found through this present research that the rapid
determination of LDR is quick compared to the traditional method. This
concept of finding LDR can reduce testing time and scrap in multistage
deep-drawing operations in which two or more drawing operations are
required to form a complete cup. Results of the parameter optimisation,
the experimental tests conducted determining LDR values for Aluminium alloy AA6111andCopperC11000atdifferenttemperaturesandsimulation
tests discussed and conclusions made are presented.

This article examines the formability of 3-layer Al 1050/Mg-AZ31B /Al 1050 sheets experimentally and numerically. Mg AZ31B, with its high strength-to-weight ratio, and Al 1050, with its formability and lightweight, are attractive industrial metals. In the experimental method, the forming limit diagram (FLD), the Forming limit angle (FLA), and the fracture depth were investigated for the 3-layer and base samples with two pyramid and cone geometries. The results showed that the ductility in the cone geometry is higher than that of the pyramid. Also, by comparing the FLD of the 3-layer sample to the base sample, the results showed that the formability of the 3-layer sample increased compared to the Mg-AZ31B base sample. In contrast, the formability decreased compared to the base sample of Al 1050. Numerical studies for predicting the FLD using the SPIF method were carried out using Abaqus software. The numerical techniques considered the second deviation minor strain (SDMIS), second deviation effect strain (SDEF), second deviation thickness (SDT), and second deviation major strain (SDMS). The results showed that the highest accuracy occurred for the SDT method compared to other numerical methods. To remove the effect of the strain path on the numerical analysis for predicting the FLD (from the stress analysis method), a second deviation of von Mises stress (SDVMS) was used. By examining the results, it was found that the results of numerical methods considering stress could be highly accurate.
Graphical Abstract

Under the leadership of the Kyoto agreements on reducing emissions of greenhouse gases, the automotive sector was forced to review its methods and production technologies in order to meet the new environmental standards. In fuel consumption reduction is an immediate way to reduce the emission of polluting gases. In this paper, the study of the formability of sheet submitted to the hydroforming process is proposed. The numerical results are given to validate the proposed approach. To show the influence of uncertainties in the study process, we take some characteristics of the material as random and the probabilistic approach is done. The finding results are showing the effectiveness of the proposed approach. I.

The shaping by hydroforming process involves several complex phenomena and presents several types of nonlinearities (geometric, material, etc.). The development of a hydroforming operation requires a lot of testing to determine with precision the optimum loads of trips and get a room without defects. Advances in digital tools have enabled manufacturers to simulate and optimize their production facilities before launching the production in order to minimize the maximum rate of defective parts. Several techniques or deterministic optimization methods have been proposed over the last decade in order to properly conduct a formatting operation. The majority of these techniques combine the finite element method and optimization techniques.

Deux méthodes de caractérisation du comportement anisotrope de tôles sont comparées. Les coefficients de Lankford de tôles en alliage d'aluminium-magnésium sont tout d'abord déterminés via des essais de traction à température ambiante. Un système de reconnaissance automatique de motifs aléatoires est utilisé pour analyser ces essais en termes de comportement mécanique et pour identifier les coefficients d'anisotropie. En parallèle, des essais d'emboutissage de type Nakazima ont été réalisés, puis analysés à l'aide d'un module d'analyse inverse. Ce modèle s'appuie sur une méthode d'optimisation automatique couplée à un logiciel éléments finis tridimensionnel. Le comportement anisotrope des tôles d'aluminium est modélisé en utilisant un critère de Hill. Les mesures de champs de déformation obtenues avec le système de corrélation d'images sont utilisées pour identifier les paramètres du critère de Hill. Les coefficients de Lankford ainsi déterminés sont comparés à ceux issus des essais de traction.

An effort has been made to improve the formability of (1006) AISI steel alloy sheets in deep drawing of square-shaped parts with flat bases through hydroforming. To achieve this goal, the manufacturing process involved the use of a newly developed experimental setup for sheet hydroforming with a die, which was created by the researchers. The key design features of this setup aimed for simplicity and modularity, allowing for potential utilization with oil pressures of up to 100 MPa. The obtained results were compared with those of conventional
deep drawing. Both processes were examined under specific conditions to form identical cups up to the full depth of the provided die. Indicators of formability considered for comparison included the minimum possible corner radius, the maximum achievable depth without failure, and the maximum percentage of thinning at the corners. This study demonstrates that hydroforming can enhance the formability of low-carbon steel alloy sheets by improving the flow of metal into the die cavity and reducing thinning at critical regions, when compared to
conventional deep drawing processes. In conventional deep drawing, only 70% of the full depth could be achieved before failure due to high local deformations resulting in significantly higher thinning at the corners.

Incremental sheet forming (ISF) is a novel technology to takes part in solving a lot of problems from classical sheet forming operation in terms of more flexibility, cheap, low production time, convenient for small batches and particularly rapid prototype production. This paper aims to provide enough information for understanding of the incremental forming process, especially focusing on numerical two point incremental sheet forming mechanism and multi stages incremental forming. The influence of some process parameters such as incremental step size and forming tool radius, on thickness distribution across the wall of the part is studied, as well as, studying the thickness distribution and strain analyses for three stages in multi stages incremental forming during forming the product with vertical angle.2-D model of cone shaped part with right forming angle has been developed in the three stages from sheet with thickness (1mm) of the aluminum alloy (AA1070). A commercial available finite element program code (ANSYS 11), is used to carry out the numerical simulation of the multistage incremental sheet forming. The results show that, when considering multi-stage incremental sheet forming, the task is even more difficult because the strain and thickness distribution resulting from the first stage will influence the subsequent results. Decreasing in the forming tool radius will increase in the thinning of the wall product due to excessive stretch will occurs, while the incremental step size is not significant effect on the numerical results (thickness, strain) distribution of the product. Finally, the goal to attain a vertical wall angle and equally maintain wall thickness and strain over the wall part is pursued. Mechanical tests, computer programming, geometry and design were required.

The shaping by hydroforming process involves several complex phenomena and presents several types of nonlinearities (geometric, material, etc.). The development of a hydroforming operation requires a lot of testing to determine with precision the optimum loads of trips and get a room without defects. Advances in digital tools have enabled manufacturers to simulate and optimize their production facilities before launching the production in order to minimize the maximum rate of defective parts. Several techniques or deterministic optimization methods have been proposed over the last decade in order to properly conduct a formatting operation. The majority of these techniques combine the finite element method and optimization techniques.

In this paper, an attempt has been made to enhance formability of cryorolled AA5083 alloy sheets (annealed at 275 • C for 15 min) in deep drawing of flat bottom square cup-shaped parts by hydroforming. Numerical simulations based on finite element method have been carried out to study the effect of important process parameters (fluid pressure and sealing force) on formability. The minimum corner radius and the maximum depth that can be achieved without failure and the maximum percentage thinning at the corners have been considered as measures of formability. The results have been compared with conventional deep drawing. The simulation results have also been validated with experimental work in both hydroforming and conventional forming. A process window with optimum combination of peak sealing force and peak pressure has been identified to form the cups up to full depth of the die without failure at die entry or bottom corners. Lubrication between the die and the blank reduced the minimum possible corner radius to nearly 16 mm with thinning less than 6%. In conventional forming only 70% of the full depth could be obtained before failure with 16 mm punch corner radius due to much higher thinning at the corners. This work demonstrates that, by hydroforming, formability of high strength cryorolled Al alloy sheets can be enhanced due to lower thinning and more uniform strain distribution and hence this process route (cryorolling followed by hydroforming) is a potential technique to produce complex parts from lightweight high strength Al alloy sheets due to enhanced formability.

In this paper, an attempt has been made to enhance formability of cryorolled AA5083 alloy sheets (annealed at 275 • C for 15 min) in deep drawing of flat bottom square cup-shaped parts by hydroforming. Numerical simulations based on finite element method have been carried out to study the effect of important process parameters (fluid pressure and sealing force) on formability. The minimum corner radius and the maximum depth that can be achieved without failure and the maximum percentage thinning at the corners have been considered as measures of formability. The results have been compared with conventional deep drawing. The simulation results have also been validated with experimental work in both hydroforming and conventional forming. A process window with optimum combination of peak sealing force and peak pressure has been identified to form the cups up to full depth of the die without failure at die entry or bottom corners. Lubrication between the die and the blank reduced the minimum possible corner radius to nearly 16 mm with thinning less than 6%. In conventional forming only 70% of the full depth could be obtained before failure with 16 mm punch corner radius due to much higher thinning at the corners. This work demonstrates that, by hydroforming, formability of high strength cryorolled Al alloy sheets can be enhanced due to lower thinning and more uniform strain distribution and hence this process route (cryorolling followed by hydroforming) is a potential technique to produce complex parts from lightweight high strength Al alloy sheets due to enhanced formability.

The paper presents an analysis of the multistage deep drawing process considering the three
deformation stages namely drawing reverse and reverse redrawing respectively. This work aim to
study the mechanism of deformation during the redrawing process where the second and the third
stages were done in reverse redrawing and study the effect of this mechanism on produced cup wall
thickness, strain distribution across the wall of the drawn part. 2-D model of cylindrical cup
(46.75mm) diameter has been developed in the first stage from sheet with thickness (0.5mm) of the
low carbon steel (AISI 1008) and (85mm) diameter, while for second and third stages of drawing a
punch diameter (32.725mm, 27.489mm) respectively, and inside diameter of dies equal to
(33.825mm, 28.589mm) respectively, the clearance is chosen for three stage equal to 0.55mm. A
commercial available finite element program code (ANSYS 11), is used to perform the numerical
simulation of the multistage deep drawing. The results show that, when considering multi-stage
drawing, the task is even more difficult because the strain and thickness distribution resulting from
the first stage will influence the subsequent results, increase in thinning in the wall cup will appear
in the second and third stages. Finally this work introduces new method (multi reverse redrawing)
to produce circular cup throw three stages of drawing reduction in one stroke without the need to
the loading and unloading the tools among the stages as in direct redrawing which means reducing
the cost, time, efforts and enhancing cup production.

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This work aims to experimentally study the deep drawability of DD14 hot-rolled steel sheets and to optimize numerically the material formability. The material anisotropy was confirmed by metallographic analysis of the material and tensile tests on specimens taken in three orientations with respect to the sheet rolling direction. Where the stress-strain curves show a sensitivity of material to the Piobert-Lüders phenomenon. The die pressure and the blank holder were considered as controlling factors on plastic instability and the success of the deep drawing operation. The forming limit curves (FLC) were plotted to highlight the different deformation modes that the sheet metal underwent during the deep drawing process. The collected deep-drawn parts observation shows severe plastic instability, until fracture. The initial plastic anisotropy is determined by the Hill48 quadratic criterion and the work hardening by the Hollomon power law. It results, during the experimental tests, that the front bottom corners of the deep drawn part are the areas at high risk of damage. The various numerical simulation scenarios followed by comparisons with the experimental results, allowed us to confirm the optimum conditions that minimize the material's plastic instability risks, forming operation "Step" and BHP "Amplitude".

Under the leadership of the Kyoto agreements on reducing emissions of greenhouse gases, the automotive sector was forced to review its methods and production technologies in order to meet the new environmental standards. In fuel consumption reduction is an immediate way to reduce the emission of polluting gases. In this paper, the study of the formability of sheet submitted to the hydroforming process is proposed. The numerical results are given to validate the proposed approach. To show the influence of uncertainties in the study process, we take some characteristics of the material as random and the probabilistic approach is done. The finding results are showing the effectiveness of the proposed approach. I.

Deep drawing process is a significant metal forming process used in the sheet metal forming industries. From these process most complex shapes is manufactured with less defects. Deep drawing process has many effectible process parameters from which optimum parameters must be identified so that an efficient final product will be obtained. In which effects of different sheets on deep drawing process observed for sheet metal of 0.8mm of SS304, Brass and 0.9 mm of Al. The experiments are performed by designing the deep drawing tools such as die, blank holder, and punch. Also the numerical simulations are performed for deep drawing of rectangular cups using two levels of aforesaid parameters like lubricating condition and blank material. The experiments are conducted by attaching the deep drawing tools to the Universal Testing Machine. For numerical simulation a commercial FEM code is used in which Hollomon's power law and krupowski power law along with Hill's 1948 yield criterions are implemented. The deep drawing setup used in the FEM code is modelled using a CAD tool by considering the modelling requirements from the literature. Strain path of 55x55mm are simulated. Punch forces and dome heights are evaluated for all the conditions. From this work the formability for different metal sheets is observed for different blank materials.

Incremental sheet forming (ISF) requires no or partial dies for sheet metal fabrication and is widely used for small batch production. In this process, necking is either suppressed or delayed due to the localized nature of tool–sheet contact; hence, more strains than conventional stamping and deep drawing are obtained. In the present study, two variations of ISF, namely cold ISF (CISF) and warm ISF (WISF), are compared. First, FEA modeling is carried out on ABAQUS to reach the forming forces involved in the process. It is found that WISF reduces the forming forces. The temperature for WISF is maintained at 180 °C. Following the simulation analysis, tests are carried out. The forming force in WISF is 55.77% less than that in CISF. The part fabricated by CISF is slightly more substantial than that by WISF; however, more forming depth can be achieved by WISF. There is a more uniform thickness distribution in the case of CISF than in WISF. However, the surface quality of the CISF produc...

The deep drawing method is widely used in the metal industry. With this method, metal sheets are formed in the desired form. In this study, a finite element analysis of the deep drawing process of DC02 sheet was made using an angular die. In the study, 15 different die radii were used. 10° die angle was used in all experiments. A blank holder was not used in this study. The effects of different die radii on the forming process were investigated. As a result of the study, it was determined that the most suitable die radius in terms of both equivalent plastic strains (PEEQ) and Mises stress was 8 mm. It was observed that the largest stresses occurred just above the cup radius, and the plastic strain increased as it moved towards mouth region of the cup.

The deep drawing process is a forming process which occurs under a comb ination of tensile and compressive conditions. Formability is the ability of a given metal work piece to undergo plastic deformation without being damaged. The p lastic deformation capacity of metallic materials, however, is limited to a certain extent, at which point, the material could experience tearing or fracture. Formability of sheet metal can be evaluated by various tests like swift cup drawing test, fukui's conical cup drawing test , erichsan cupping test, osu Formability Test, Hydraulic Bulge Test, Duncan Friction Test. These tests are widely used to evaluate of formability for different sheet metals. In this paper, swift cup a nd erichsen cupping tests presented.

In this research, the fracture phenomenon was investigated on flexible roll forming process of channel section using ductile fracture criteria and forming limit diagram (FLD) by considering the effect of anisotropy. For this purpose, a finite element simulation of the process using the ABAQUS software was done. The fracture in this process was evaluated by considering six types of ductile fracture criteria by UMAT subroutine implementation on the FEM software and using FLD criterion. Experimental tests were performed on 27 blanks of Al6061-T6 using flexible roll forming machine made in Shahid Rajaee Teacher Training University (SRTTU). Numerical results were validated by experimental results. In addition, prediction of occurrence and fracture position by ductile fracture criteria and FLD criterion were compared with experimental results; the Argon criterion was chosen as the most appropriate criterion to predict the fracture position and its occurrence. The fracture occurrence was only observed in a 60°bending angle for 1.5-and 2-mm thicknesses, and the fracture position error percentages of the Argon criterion with experiments for these cases were 18.7 and 3.5%, respectively. Also, the effects of parameters such as sheet thickness, bending radius, and bending angle on the fracture phenomenon by using the selected criterion of Argon were studied.

This research was carried out aiming to investigate the application of a tip-bottomed tool for bending an advanced ultra-high strength steel sheet. The V-die bending experiment of a dual phase steel (DP980) sheet which had a thickness of 1.6 mm was executed using a conventional bending and a tip-bottomed punches. Experimental results revealed that the springback of the bent worksheet in the case of the tip-bottomed punch was less than that of the conventional punch case. To further discuss bending characteristics, a finite element (FE) model was developed and used to simulate the bending of the worksheet. From the FE analysis, it was found that the application of the tip-bottomed punch contributed the plastic deformation to occur at the bending region. Consequently, the springback of the worksheet reduced. In addition, the width of the punch tip was found to affect the deformation at the bending region and determined the springback of the bent worksheet. Moreover, the use of the tip-bottomed punch resulted in the apparent increase of the surface hardness of the bent worksheet, compared to the bending with the conventional punch.

Hyper Form is the module of Altair Hyperworks used for formability analysis and prediction various defects like wrinkles, spring-back and thinning occurred in sheet metal drawing process. A sheet metal drawing process is widely used in industry for producing seamless cup formed parts in automobile, aircraft and household applications. During the product design and tool design designer are still adapts trial and error method to decide blank shape, blank size, draw tool and process parameters. Computer aided engineering (CAE) plays very significant role in the decision making of various parameters of sheet metal forming processes and it helps to designer during product design as well tool design stage to decide optimum and accurate process parameters. The use of CAE software such as HyperForm during product design and tool design stage minimizes the tool trial time and cost. This paper describes the study of effect of die parameter such as die radius and process parameters such as bla...

The forming process leads to a considerable differentiation of the strain field within the billet, and finally causes the non-uniform distribution of the total strain, microstrusture and properties of the material over the product cross-section. This paper focus on the influence of stress states on the deformation-induced a' martensitic transformation in AISI Type 316 austenitic stainless steel. The formation of deformation-induced martensite is related to the austenite (g) instability at temperatures close or below room temperature. The structural transformation susceptibility is correlated to the stacking fault energy (SFE), which is a function not only of the chemical composition, but also of the testing temperature. Austenitic stainless steels possess high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Nevertheless, the deformation-induced martensite transformation may enhance the rate of work-hardening and it may or may not be in favour of further material processing. Due to their high corrosion resistance and versatile mechanical properties the austenitic stainless steels are used in pressing of heat exchanger plates. However, this corrosion resistance is influenced by the amount of martensite formed during processing. In order to establish the links between total plastic strain, and martensitic transformation, the experimental tests were followed by numerical simulation.

Metal bipolar plates are the most important parts of the fuel cells and recently these plates are used instead of graphite ones.In the present study, gas blow forming of a pin-type aluminum 5083 bipolar plate has been studied. After the simulation of the process, the FE model has been validated using experimental results. Then, the effects of parameters including maximum pressure of the gas, pressurization profile and corner radius of the pin on thinning ratio and forming depth of final part have been investigated. Nine experiments were designed using the Taguchi L9 orthogonal array and the experiments were performed using the FE model. The signal to noise (S/N) ratio and the analysis of variance (ANOVA) techniques were carried out to determine the effective parameters and the contribution of each parameter. The maximum pressure of 1.2 MPa, SP2 pressurization profile and corner radius of 0.2 mm lead to the minimum thinning ratio. Also, it was found that to maximize the forming depth...

Osnovni predmet i cilj ovog rada se odnosi na prikaz uloge tehnološke pripreme proizvodnje u procesu izrade alata za injekciono presovanje plastike. Opisane su i realizovane aktivnosti konstruisanja alata za konkretan proizvod - držač cevi za podno grejanje, pro­jektovanja tehnološkog procesa izrade vitalnih delova alata (kokila) kao i generisanje upravljačkih programa za njihovu obradu na CNC mašinama uz primenu prog­ramskog sistema PTC/Creo Parametric.

In body design, Finite Element Analysis becomes an unavoidable step in optimizing forming processes to ensure the feasibility of a specific designed shape. Different failure criteria exist but the Forming Limit Diagram remains the most used criterion. It can be built in a wide variety of forms but the most usual one is composed only of a Forming Limit Curve (FLC) which represents the onset of localized necking limit of sheet metal. FLC is determined experimentally by standardized Nakajima or Marciniak tests. However, both present lots of roadblocks in the accurate determination of product formability limits due to the use of counter-blanks, no linear strain paths and because they are not adapted for high ductility steels. Tensile tests were performed in the past to determine the left hand side of the FLCs. They were not included into the ISO 12004-2 standard because of technical reasons although they present lots of advantages (frictionless, no curvature effect and planar configuration). Now, thanks to the current advanced technologies and tools, these issues are overcome. In this paper, the advantages of tensile tests compared to Nakajima or Marciniak ones are briefly discussed. The design and conceptualization of specific jaws to perform plane strain tensile tests on AHSS are presented. A wide range of AHSS was characterized through plane strain tensile tests and results were compared to formability limits determined by the usual practice using Nakajima tests. Different evaluation strategies were used to determine the maximum formability: the position dependent method, the time dependent one and close to fracture.

In this work we propose a method for deforming a pre-coated metal sheet via SPIF. The influence of the pitch and feed-rate on the dimensional precision has been studied. This work is of interest for companies dedicated to the manufacture of molds for the agri-food sector, which can directly manufacture prototypes or short series by this system.

Incremental sheet forming (ISF) requires no or partial dies for sheet metal fabrication and is widely used for small batch production. In this process, necking is either suppressed or delayed due to the localized nature of tool–sheet contact; hence, more strains than conventional stamping and deep drawing are obtained. In the present study, two variations of ISF, namely cold ISF (CISF) and warm ISF (WISF), are compared. First, FEA modeling is carried out on ABAQUS to reach the forming forces involved in the process. It is found that WISF reduces the forming forces. The temperature for WISF is maintained at 180 °C. Following the simulation analysis, tests are carried out. The forming force in WISF is 55.77% less than that in CISF. The part fabricated by CISF is slightly more substantial than that by WISF; however, more forming depth can be achieved by WISF. There is a more uniform thickness distribution in the case of CISF than in WISF. However, the surface quality of the CISF produc...

The microstructure, texture, and mechanical properties of the Al/Ni/Cu composite during various accumulative roll bonding (ARB) cycles were studied using optical microscopy, scanning electron microscopy, xray diffraction, shear punch test, and hardness test. In addition, ImageJ software and Rietveld software were used in order to study microstructure and dislocation density variations, respectively. It was found that Ni and Cu layers were fractured and distributed in the Al matrix due to differences in their mechanical properties. Fracture and distribution of Cu and Ni particles after cycle five led to the alteration of the composite structure from a layered to a particle-reinforced structure. ARB process leads to the formation of strong orientation along the b-fiber and also to pronounced copper and dillamore components in both Al and Cu phases. Furthermore, the shear yield stress and ultimate shear strength of the composite increased as the ARB process advanced; however, shear elongation presented a non-uniform variation. Investigation of the fracture surfaces revealed that the mechanical properties of the composite are affected not only by the strain hardening of the Cu layer, but also by the structural change in the composite during the initial ARB cycles. During the last stages of the process, however, changes in mechanical properties were mostly governed by reinforcement particles serving as strain concentration zones and the strain hardening of the Al matrix.

This study explores the impact of pre-strain on the uniaxial tensile stress-strain behavior of extra deep drawing (EDD) steel at varying strain rates. The EDD steel blanks were subjected to a uniaxial pre-strain of 15 % in either the transverse or rolling direction. Subsequently, uniaxial tensile tests were conducted at different strain rates, both orthogonal and parallel to the initial pre-straining direction. The study also investigates the alterations in yield stress (YS), ultimate tensile strength (UTS), uniform elongation (UEL), total elongation (TEL), and strain energy absorption (SED, represented by the area under the tensile stress-strain curve) at diverse strain rates after pre-straining. The experimental findings indicate that pre-straining is advantageous for enhancing YS, UTS, and SED. However, this improvement comes at the expense of UEL or TEL. A square crush tube, which shares similarities with automotive components, was examined to assess the crash performance of several automotive structural parts during crash events. A validated constitutive model was used to predict the square tube's energy absorption and crush performance under high-velocity conditions for different pre-straining scenarios.

The formability of the drawn part in the deep drawing process depends not only on the material properties, but also on the equipment used, metal flow control and tool parameters. The most common defects can be the thickening, stretching and splitting. However, the optimization of tools including the die and punch parameters leads to a reduction of the defects and improves the quality of the products. In this paper, the formability of the camera cover by aluminum alloy A1050 in the deep drawing process was examined relating to the tool geometry parameters based on numerical and experimental analyses. The results showed that the thickness was the smallest and the stress was the highest at one of the bottom corners where the biaxial stretching was the predominant mode of deformation. The problems of the thickening at the flange area, the stretching at the side wall and the splitting at the bottom corners could be prevented when the tool parameters were optimized that related to the thi...

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Incremental forming is a novel process which proves to be an effective and alternative method for the production of economically low-volume functional products. The process exhibits a potential to manufacture three dimensional parts without the use of dedicated dies. The paper describes the technique of using CNC milling machine and hemispherical shaped tool which aids in the formation of final shape of the component by a series of step deformation. The associated attributes pertinent to the analysis are forming angle, roughness characteristics and thickness distribution. Finite element modeling using ABAQUS were carried out and results were compared and validated.

More recently, titanium and aluminum alloys are gaining more interests to be implemented in hydro-forming applications. It is necessary to predict forming limits for these sheet alloys. Forming limits play an important role in metal forming processes. Forming limit diagrams, present the limit strains for various linear strain paths. In other hand, forming limit curve (FLC), illustrates localized formability for sheet metals under proportional loadings and are known as a powerful tool for trouble-shooting in sheet metal forming processes. In this study, mechanical properties of Ti-6Al-4V titanium sheets, AA7075-T6 and AA2024-T3 aluminum sheets are investigated through the uni-axial tensile test. Anisotropy coefficients as well as work-hardening exponent resulted from tensile test were used to theoretical prediction and numerical simulation of limit strains. For the theoretical prediction of the forming limit curves, several constitutive models were implemented. Several Hill's yield criteria combined with Swift equation and empirical equation proposed by NADDRG were accomplished to predict the FLDs. Results showed that calculated numerical results are in good agreement with the predicted theoretical data when Hill93-Swift is the used instability criteria.

Unexpected fractures at high-curvature die radii in sheet forming operations limit the adoption of advanced high strength steels (AHSS) that otherwise offer remarkable combinations of high strength and tensile ductility. Identified as ''shear fractures'' or ''shear failures,'' these often show little sign of through-thickness localization and are not predicted by standard industrial simulations and forming limit diagrams. To understand the origins of shear failure and improve its prediction, a new displacement-controlled draw-bending test was developed, carried out, and simulated using a coupled thermo-mechanical finite element model. The model incorporates 3D solid elements and a novel constitutive law taking into account the effects of strain, strain rate, and temperature on flow stress. The simulation results were compared with companion draw-bend tests for three grades of dual-phase (DP) steel over a range of process conditions. Shear failures were accurately predicted without resorting to damage mechanics, but less satisfactorily for DP 980 steel. Deformation-induced heating has a dominant effect on the occurrence of shear failure in these alloys because of the large energy dissipated and the sensitivity of strain hardening to temperature increases of the order of 75°C. Isothermal simulations greatly overestimated the formability and the critical bending ratio for shear failures, thus accounting for the dominant effect leading to the inability of current industrial methods to predict forming performance accurately. Use of shell elements (similar to industrial practice) contributes to the prediction error, and fracture (as opposed to strain localization) contributes for higher-strength alloys, particularly for transverse direction tests. The results illustrate the pitfall of using low-rate, isothermal, small-curvature forming limit measurements and simulations to predict the failure of high-rate, quasi-adiabatic, large-curvature industrial forming operations of AHSS.

This paper presents new results on dynamic neck evolution in steel bars of varying diameters. Dynamic tensile tests were carried out in a Kolsky apparatus using cylindrical steel specimens with various cross-section diameters ranging from 1.5 mm to 4 mm. A high speed digital camera was used to record the deformation of the specimen during the loading process. Video recording of the tests enabled accurate experimental measurements of the necking evolution, specifically its growth rate as a function of the diameter. The experiments show that increasing the specimen cross-section slows down the neck development. This behavior has been further investigated using two different kinds of numerical calculations: (1) axisymmetric finite element simulations and (2) one-dimensional finite difference computations. While the finite difference model only considers the normal stress along the longitudinal direction of the bar, the finite element model does not entail any simplification on the stress state of the specimen during the loading process. In agreement with the experiments, the finite element calculations show a decrease of the necking growth rate with the increase in the cross-section of the sample. On the contrary, the damping effect of the specimen cross-section on the necking evolution is not captured by the finite difference computations. We postulate that this result comes from the one-dimensional nature of the finite difference model. This work uncovers, by means of combined experiments and modelling, the key role played by stress multiaxiality in the growth rate of dynamic necks.

This paper addresses modeling and optimization of loading path in T-shape hydroforming of tubes using analysis of variance technique and Simulated Annealing (SA) algorithm. A set of experimental data has been used to assess the influence of loading process parameters in hydro-formed geometry. The process variables considered here include the yielding and expanding internal pressures and their required times, the calibration pressure, the axial and counter punches movements. The process output characteristics include thickness and height of protrusion. The Taguchi method and regression modeling are used in order to establish the relationships between the input and output parameters. Thirty two different cases for different loading paths are designed. The Abaqus/Explicit is used to calculate the minimum thickness and maximum height of protrusion. The adequacy of the model is evaluated using analysis of variance (ANOVA) technique. The proposed model is embedded into a Simulated Annealing (SA) algorithm to optimize the loading process parameters and to find the best input variables. Computational results prove the effectiveness of the proposed model and optimization procedure.

In sheet metal forming operations, the most deleterious defect are wrinkling, tearing, necking and springback. Wrinkling of cups drawing was simulated using the finite element method (FEM). The fem code Autoform was used in numerical analysis. Wrinkling phenomenon is affected by the mechanical properties of the blank sheet material, contact conditions, blank holder force and the geometry of the punch and dies. The wrinkling prediction is difficult to perform due to the highly sensitivity of the parameters. The small variations of the parameters can result in widely different wrinkling behaviours. The aim of this paper is to investigate the effects of lubrication and blank holder force on a dome wrinkling behaviour. Two different punch geometries have been selected for Auminum and steel.

Abstract Sheet metal forming industry widely adopted the forming limit curve (FLC) as a limiting criterion in sheet metal forming. Regardless of its commercial importance, controlling factors of FLC are not systematically investigated up to date. The present paper comprehensively discussed the effect of different influencing factors on FLC, including limiting strain determination method, punch geometry, microstructure, pre-straining path, strain rate, and temperature. Different tensile properties and their correlations with FLC are also investigated. The introduction of microstructural features such as reducing void nucleation sites i.e., non-coherent particles, evenly distribution of fine hard phases, the introduction of twin and transformation induced plasticity (TRIP & TWIP), are favourable for higher FLC.

In this article, for the first time, the forming limit diagram (FLD) and mechanical properties of aluminum foil samples processed by the accumulative roll bonding (ARB) process have been studied experimentally. For this purpose, thin aluminum foils with a thickness of 200 microns have been produced using ARB in five passes at ambient temperature. By rising the number of ARB passes, the ultimate tensile strength (UTS) enhanced drastically, and at the end pass of ARB, it reached 393 MPa, about 5.9 times larger than the initial sample. Also, during the ARB process, the applied strain increased, and the thickness of the layers decreased, and the bonding quality between layers improved. SEM images of tensile fracture surface after five cycles showed the mechanism of fracture retained ductile. However, due to the unevenly applied strain, the dimples were drawn in different directions, and their depth and number were reduced relative to the raw material. The area under the FLDs, a criterio...

Hydraulic power transfer and management systems are widely used in modern agriculture, especially in agricultural engineering and the associated processing industry. They can be very simple, but also extremely complex, when precise matching of the interaction of their components in real time is very difficult to controll and achieve. In addition, the designs of a number of hydraulic components is sufficiently complicated for detailed representation on the corresponding hydraulic installation. In all cases, analyzing the performance characteristics of components and the entire hydraulic system, as well as understanding the structure of the hydraulic system, is of great importance. One of the generally accepted ways to facilitate and speed up these processes is the application of schematic diagrams of hydraulic systems and their subcircuits. Officially, hydraulic symbols are defined by ISO industry standards. Therefore, ideally, all hydraulic schemes should be configured using univers...

Two-layer sheets which consist of dissimilar metallic components are widely used in various industries. In this paper, formability of Al3105-St14 two-layer sheet is evaluated numerically and experimentally. Freudenthal, Cockroft & Latham, Oh and Brozzo ductile fracture criteria are implemented to predict forming limits in the numerical approach. Numerical FLDs and FLSDs are compared with experimental observations for Al3105-St14 two-layer sheet, and a good agreement is seen. The results show that the prediction of forming limits based on Oh and Brozzo ductile fracture criteria are more accurate than the predictions based on Freudenthal and Cockroft criteria.

Using a rigid-plastic finite element program deep drawing, direct and reverse redrawing of two layer aluminum-austenitic stainless steel (AL-ASS) laminated sheets have been simulated. The results of simulations as the variation of drawing ratios with thickness ratio and setting condition are presented. They show that to access the highest drawing ratios in direct and reverse redrawing, thickness ratio should be about 1/3 (one layer aluminum and three layer stainless steel) and the setting conditions are opposite to each other. In another word, while in direct redrawing contact of austenitic stainless steel with punch leads to the maximum drawing ratio, in reverse redrawing, aluminum should contact the punch in order to access highest drawing ratio. An explanation for this finding is offered through the thickness strain distribution.

The formability of the drawn part in the deep drawing process depends not only on the material properties, but also on the equipment used, metal flow control and tool parameters. The most common defects can be the thickening, stretching and splitting. However, the optimization of tools including the die and punch parameters leads to a reduction of the defects and improves the quality of the products. In this paper, the formability of the camera cover by aluminum alloy A1050 in the deep drawing process was examined relating to the tool geometry parameters based on numerical and experimental analyses. The results showed that the thickness was the smallest and the stress was the highest at one of the bottom corners where the biaxial stretching was the predominant mode of deformation. The problems of the thickening at the flange area, the stretching at the side wall and the splitting at the bottom corners could be prevented when the tool parameters were optimized that related to the thi...

Friction between sheet and tool is important phenomenon in sheet deep drawing process. The paper provides the analysis of impact friction coefficient on a deep-drawing force change. 3D numerical simulation was applied by using PAM-STAMP software. Key words: deep drawing, simulation, analyze 1.