Limiting Drawing Ratio Research Articles

Prediction of earing defect and deep drawing behavior of commercially pure titanium sheets using CPB06 anisotropy yield theory

Recently, sheet metal forming industries have shown interest in characterization of anisotropy properties, tension-compression strength differential and deep drawing behavior of commercially pure titanium (CP Ti) material for successful fabrication of lightweight components. In present work, the formability of 1.0 mm thick CP Ti sheet metal was studied using a laboratory scale deep drawing test set-up, and the limiting drawing ratio (LDR) was found to be 2.143. Four ears were observed in the LDR cup with maximum cup height along diagonal direction (DD) and troughs along both rolling direction (RD) and transverse direction (TD), and the earing height was approximately 13.7% of the total cup height. Tensile and stack compression tests were carried out along different orientations to evaluate the anisotropy properties and tension-compression strength differential, and these data were used to develop the CPB06 constitutive yield model. Also, the developed CPB06 anisotropy plasticity theory was implemented in an FE model to predict the non-uniform material flow, earing defect and thickness distribution successfully. In order to reduce earing defect, a two-stage blank modification technique was proposed incorporating directionalities of both yield strength and plastic strain ratio. A significant 83% reduction in earing height was achieved through use of modified blank with simultaneous benefit of improvement in thickness distribution and reduction in peak load.

Evaluation of numerical and experimental investigations on the hybrid sheet hydroforming process to produce a novel high-capacity engine oil pan

The engine oil pan is used for restraining pollutant and gathering greasing oil from the engine components’ surface which is significant for thermal dissipation and preventing deterioration of oil quality. The study intended to investigate and develop a hybrid sheet hydroforming process for fabricating an innovative high-capacity oil pan that has the characters of asymmetrical cavity depth and major lateral bulging. Firstly, a two-stage hydromechanical deep drawing (HMDD) process was accomplished, which included precedingly regional and eventually integral deep drawing assisted by fluid counter force. The finite element modeling (FEM) was employed to study the impact of the die fillet dimension as well as the loading routes on the formability of the preformed part. The limited drawing ratio can be enhanced from 2.34 to 2.77 for AISI 304 by HMDD. Hydro-bulging was subsequently investigated by the simulations accompanied by the relatively experimental verification. Both the simulated and experimental results showed that there is a remarkable influence of lubrication condition and intermediate heat treatment on the formability of the final part. The cracks occurred at the corners of the main bulging area can be alleviated by reduction of friction coefficient. Furthermore, wrinkles and cracks have been completely eliminated and the thinning ratio can be reduced to 31.8% for the final part, when intermediate heat treatment is additionally employed. It was concluded that the present hybrid sheet hydroforming process is feasible and sufficient to manufacture a sound engine oil pan without any defects through the optimization of the process parameters.

Cylindrical cup-drawing characteristics of aluminum-polymer sandwich sheet

Compared with conventional monolithic material, an aluminum-polymer sandwich sheet possesses advantageous strength/stiffness versus weight ratio and has received increasing attention in aeronautical, automotive, marine, and civil engineering industries. In the present study, limiting draw ratio (LDR) and other cylindrical cup-drawing characteristics of aluminum-polymer sandwich sheets were investigated by experiments and numerical simulations. Deformation behaviors of skin layer and core polymer layer were analyzed respectively. It was demonstrated that the deformation mode of exterior sheet tends to biaxial tension state and that of interior sheet tend to compression state. The LDR of aluminum-polyethylene sandwich sheet was well predicted, and influences of core layer thickness and mechanical properties of skin sheet on the LDR of sandwich sheet were analyzed. Research results show that the drawability of the aluminum-polymer sandwich sheet becomes poor with increasing the thickness of the polymeric core and the strength of core polymer. The LDR of the sandwich sheet mainly depends on the drawability of the skin sheet.

Effect of solution treatment on deep drawability of IN718 sheets: Experimental analysis and metallurgical characterization

A promising approach to decrease deformation load and improve ductility during forming of Inconel-718 (IN718) is through the use of solution treated blanks. In the present work, IN718 sheets were separately solution treated to different temperatures in the domain of 970–1070°C at an interval of 50°C to dissolve the strengthening precipitates (γ′ and γ′′), and subsequently, were oil quenched to retain the microstructure. Due to significant difference in average grain size, the solution treated samples of 970°C (HT970) and 1070°C (HT1070) were selected for tensile characterization, deep drawing analysis, and micro-texture evolution. The tensile test response showed approximately 30% improvement in ductility and 27% reduction in load in case of HT1070 material with respect to that of HT970 material. The deep drawing process window was evaluated using flat bottom and hemispherical dome punch geometries, and it was found that the limiting draw ratio (LDR) improved marginally by 4.5% in case of HT1070 material. This improvement was due to the dominating presence of cube component in initial texture of HT1070 material. The high presence of cube and goss components in initial texture and the large difference in Taylor factor of individual grains at critical regions of deep drawn cups led to higher unsatisfactory surface roughness in the case of HT1070 material. Hence, it is suggested that the deep drawn components of HT970 material has better part performance in terms of surface roughness. Further, an attempt was made to correlate the fractographs with the fracture and formability behavior of sheet metal.

Математическая модель расчета предельного коэффициента вытяжки цилиндрических деталей из листовых заготовок переменной толщины

Математическая модель расчета предельного коэффициента вытяжки цилиндрических деталей из листовых заготовок переменной толщины

Управление качеством заготовок, получаемых обработкой металлов давлением

Current requirements to blanks manufactured by metal forming are presented. There are shown data on accuracy and surface roughness of rolled blanks. Different fracture criteria used for the analysis of press forming are analyzed. It is shown that metal tests on Eriksen should not be used for the estimate of the limiting drawing ratio.

Analysis of non-isothermal warm deep drawing of dual-phase DP600 steel

Improving the formability of the material is a key issue in the deep drawing process. Heating the material above its recrystallization temperature drastically increases formability, but in the case of dual phase (DP) steels, it results in a loss of their mechanical properties. To improve the drawing ratio, only the heating of the flange region in the warm temperature range up to 573 K was studied on DP600 sheet steel by numerical simulation. A thermo-elastic-plastic finite element method (FEM) analysis of deep drawing at several drawing ratios was performed and compared with experimental results. During the experiments, the flange area of the blank was heated by induction heating, and the central part over the punch was cooled with spray water. Experimental results showed that limiting drawing ratio could be increased by 25.58%. The microstructure of the DP 600 steel was analyzed before and after the warm forming process. No significant changes were observed, and the high strength properties of the DP 600 steel remained intact. There was good agreement between numerical and experimental results.

Developing a Zener–Hollomon Based Forming Limit Surface for Warm Sheet Forming of Magnesium Alloy

The concept of Zener–Hollomon (Z) based Forming Limit Surface (Z-FLS)—which has minor strain, major strain, and ln(Z) as its three axes—was initially proposed in a previous study. In the Z-FLS diagram, strain rate and temperature effects on the major limit strain are reflected by ln(Z). In the current study, the concept of Z-FLS is revisited to provide a practical approach to construct Z-FLS. A Z-FLS then is constructed for magnesium alloy AZ31B sheet material using available experimental forming limit curves. The constructed Z-FLS is used to identify fracture in a non-isothermal warm cup forming process, which was modeled as a coupled thermo-mechanical process. Based on the Z-FLS, the determined limiting draw ratio (LDR) matches well with the published experimental results.

Deep drawing of cylindrical cups using polymer powder medium based flexible forming

A novel flexible forming process—polymer powder medium based flexible forming (PPFF)—was presented in this research. Cylindrical cups with inner diameter of 8 mm were formed using rigid mould deep drawing and PPFF process, respectively. The blank material was pure copper C1100 with a thickness of 0.4 mm which was annealed at 450°C for 1 h in vacuum condition. The deep drawing experiments were carried out at room temperature under dry friction condition. Ethylene-vinyl acetate copolymer (EVA), poly vinyl chloride (PVC) and ultra-high molecular weight polyethylene (UHWPE) were used. The influence of polymer powder type and weight on deep drawing force and limiting drawing ratio (LDR) were investigated. The results showed that the cylindrical cups were well formed by using PVC. The LDR reached 2.1 by using PVC, higher than rigid mould. The surface quality was also good, with the thinning rate much smaller than rigid mould forming.

Experimental Research of the Usability on Double Acting Intensifiers in Hydroforming

The hydroforming method is especially used for forming lightweight materials like aluminum, magnesium alloys, high strength steels or materials that have limited formability. Intensifiers are the most important component of hydroforming presses. Nowadays single-acting intensifiers are used in hydroforming presses. Single-acting intensifiers provide pressurized liquid by forwarding movement of the piston through one direction and their volumes are limited. The mass of the intensifiers increases significantly depending on their liquid volume capacity and this causes high manufacturing costs. For this reason, two or more single-acting intensifiers which bridged in a parallel circuit are used to manufacture bigger products that require a high volume of liquid. But this method is not an economical solution. So double-acting intensifiers can overcome this problem. The pressurized liquid can be obtained during both forward and backward movement of the piston in double-acting intensifiers which work like a pump. This is why double-acting intensifiers have no volume limit on the contrary of single-acting intensifiers. Yet there are sudden pressure drops in double-acting intensifiers caused by returning movements of the piston to pressurize liquid again. This pressure drops cause some problems to use double-acting intensifiers on hydroforming method. The situation of solving this problem to use double-acting intensifiers on the hydroforming method can eliminate limited volume problem and decrease investment cost of hydroforming presses. In this study, the usability of double-acting intensifiers on hydroforming with die method was investigated. Because of the existing hydroforming press, used in experiments, doesn’t contain any double-acting intensifiers, pressure drops obtained by single-acting intensifier to perform simulated experiment. A die was designed and manufactured to synchronize the blank holder force with pressure drops. This die was integrated on the hydroforming press, located on Selcuk University Hydroforming Laboratory, for the success of the process. Performance of improved system was measured as well as repeatability of applying process parameters and product’s geometry were determined. The AA5754 aluminum alloy used processes, both single- and double-acting intensifier, were compared. Limiting drawing ratios were determined for all processes. It is obtained that pressure drops have no negative influence on formability. Moreover, there is no difference observed in thickness distribution which is an indicator of product’s quality and strength. However, when geometric accuracy was investigated then noticed that the pressure drops count has a good influence on product radius. 5.96 mm product radiuses on the process with single-acting intensifier was obtained 5.92 and 5.10 mm by using double-acting intensifier increasing pressure drop’s frequency.

Deep Drawing of constrained groove pressed EDD steel sheets

Constrained groove pressing (CGP) is a severe plastic deformation process for producing ultra-fine grained sheet metal without any change in the initial dimensions. CGP works on the principle of repetitive shear deformation of the material by alternate pressing by using asymmetrically grooved die and flat die constrained tightly by boundaries of the die. In this study, CGP, up to two passes has been performed on Extra deep drawing (EDD) steel specimens. To study the formability, the CGPed steel specimens have been deep drawn using a typical deep drawing setup and the limiting draw ratio (LDR) has been calculated. This LDR of CGPed material has been compared to the LDR of cups drawn using as-received EDD steel blanks. The formability of the CGPed material is almost the same as that of the as-received material. Apart from this, micro-hardness study of the cups has also been done on a similar comparative basis. These investigations show a slight improvement in the hardness values. It is found that by doing two passes of CGP on EDD steel, stronger cups can be produced without sacrificing much of the formability.

Hot stamping of titanium alloy sheets using partial contact heating

Hot stamping of titanium alloy sheets using partial contact heating by contact heating was developed, and cylindrical deep drawing was performed. An outer portion of a 6Al-4V titanium alloy disc blank was heated with a hot stainless-steel ring by thermal conduction. The partially heated blank was drawn just after contact heating. The limiting drawing ratio in partial contact heating was higher than that of whole heating with a furnace. The concentration in deformation at a corner was prevented by the difference in flow stress between the outer portion and punch portion of the blank. A small distortion of the bottom of the cup was observed for the result of partial contact heating because of the non-uniform thermal shrinking.

Improvement of deep drawability of ultra-fine grained 6000 series aluminum alloy by tailored heat treatment

Among other approaches like alloying, it is possible to increase the strength of aluminum sheet material by the application of processing techniques like Accumulative Roll Bonding. However, the ductility will be reduced, which results in a limited formability in deep drawing operations. In this context, the Tailor Heat Treated Blanks technology is a well-known approach to enhance the forming limits of conventional precipitation hardenable aluminum alloys. The local softening of a blank can be achieved by a short-term heat treatment, which causes a dissolution of the MgSi-clusters in the heat treated zones. In a subsequent deep drawing operation, the material flow can be improved from the softened towards crack-critical areas. Within this investigation, the method of Tailor Heat Treated Blanks is transferred to a multi-layered, ultra-fine grained sheet material of the aluminum alloy AA6014 in order to investigate the effect of a local short-term heat treatment on the forming limits in deep drawing. In a first step, a material characterization in dependency of different heat treatment temperatures is carried out. The strength and ductility, as well as the bond strength of the multi-layered sheets, are investigated. Concluding, the effect on the formability is examined by deep drawing experiments on cylindrical cups in combination with a local heat treatment of the outer flange area prior to the forming step. The results regarding the limiting drawing ratio are compared with a conventional sheet material in the T4 temper condition and a multi-layered sheet material without heat treatment. The investigations indicate that the drawability can be enhanced significantly by the combination of both methods.

Tensile properties and drawability of thin bimetallic aluminum-scandium-zirconium / stainless steel foils and monometallic Al-Sc-Zr fabricated by magnetron sputtering

Al-Sc-Zr alloys are interesting for the production of high strength micro components by micro deep drawing. These alloys show a good hardenability due to the formation of nanometer-scale spheroidal Al3(Sc, Zr) precipitates, which are highly coherent with the aluminum matrix. However, the formation of these precipitates in Al-Sc-Zr foils fabricated by conventional metallurgical methods dramatically reduces their ductility and drawability. In this work, magnetron sputtering was used to produce Al-Sc-Zr foils and Al-Sc-Zr / stainless steel bimetallic foils which are nearly free of these precipitates. Tensile tests were carried out to measure and compare the mechanical properties of monometallic Al-Sc-Zr foils and bimetallic Al-Sc-Zr / stainless steel foils deposited with varying plasma target powers and containing different volume fractions (layer thickness) of Al-Sc-Zr. Micro deep drawing was used to determine the drawability of selected monometallic and bimetallic foils. The results show that the density of monometallic Al-Sc-Zr foils can be improved significantly by increasing the DC target power and by using the high power impulse magnetron sputtering (HiPIMS) technology, resulting in foils with higher ductility. Bimetallic foils achieved higher strength and ductility than monometallic Al-Sc-Zr foils. Their mechanical properties vary with the target power and the volume fraction (thickness) of Al-Sc-Zr. The limit drawing ratio of HiPIMS deposited monometallic foil was 1.7 or 1.8 depending on the side of the foil facing the die, whereas a limit drawing ratio of 1.9 was observed for bimetallic foils.

Determination of LDR in deep drawing using reduced number of blanks

Indeed, deep drawing is one of the important sheet metal forming process, widely used in production of cup shaped articles having applications in different engineering and domestic fields such as aerospace, automobile, beverage, kitchenware etc. It is essential to determine the quality characteristics of the process for minimization of rejections as well as cost involved in it. LDR is one such quality characteristic essential to evaluate thoroughly with reduced number of steps in deep drawing. Here, the LDR is determined by means of experimental and simulation method by using the concept of “ punch force is proportional to blank diameter up to limiting drawing ratio” and remains constant over the LDR for all oversized blanks resulting in failure. In this research paper, an attempt has been made to establish a standard and quick method for “determination of LDR”. The LDR tests have been conducted with the use of only three blanks of different sizes; i.e., two of undersize and one blank of oversize. The LDR found through experiments and simulation are in good agreement with only 5.4% variation and this variation may be due to variation in lubrication conditions among the experimental and simulation methods.

Micro deep drawing of T2 copper foil using proportional decreased tools

Cooper foils are widely used in micro electronic industry, and they are suitable to be deep drawn to form cup-like parts. In this study, micro deep drawing experiments were conducted by using T2 copper foils after an annealing process, and three scale factors (λ = 0.5, 1, and 2) were set to indicate effects of proportional decreased tool dimensions and processing parameters on the forming result. The experimental results show that micro deep drawing parts with internal diameters of 0.5, 1.0, and 2.0 mm can be formed successfully. And the 0.5-mm cup drawing part has achieved the minimum dimension in recent reports. The standardized punch travel-deep drawing force curves are similar, and the maximum deep drawing force is decreased with smaller scale factor. The thickness distributions of different processing parameters are all decreased firstly and then show the trend to increase from bottom to upper regions. We find that the size effect influences the maximum deep drawing force during the forming process and the quality of forming part. And the maximum limit drawing ratio (LDR) is 2.2 for the experiment with scale factor of 0.5. Forming regularities of the proportional decreased micro deep drawing process can be presented clearly by changing the scale factor.

Microstructure, Texture and Microhardness Evolution during Annealing Heat Treatment and Mechanical Behavior of the Niobium-Stabilized Ferritic Stainless Steel ASTM 430 and Niobium-Titanium-Stabilized Ferritic Stainless Steel ASTM 439: a Comparative Study

A comparison of the influence of microstructure and texture on mechanical behavior between the niobium-stabilized ferritic stainless steel type ASTM 430, 430Nb, and the niobium-titanium-stabilized ferritic stainless steel type ASTM 439 was performed. The two steels were supplied as cold rolled thin sheets and the annealing was interrupted in different temperatures aiming the characterization of the microstructure and texture in different stages of recrystallization using optical microscopy, Vickers microhardness and Electron Backscatter Diffraction. The annealed samples were tensile tested to determine the mechanical properties and undergone to Swift test to evaluate the drawability. The steel 430Nb showed smaller grain size and greater yield stress. The steel ASTM 439 presented higher normal anisotropy coefficient, R, and higher Limit Drawing Ratio due to greater proportion of γ fiber. These results are presented and discussed in terms of precipitates and crystallographic texture developed in the recrystallization of both steels.

Numerical and Experimental Study on Manufacture of a Novel High-Capacity Engine Oil Pan Subjected to Hydro-Mechanical Deep Drawing

The oil pan is equipped at the bottom of engine crankcase of the automobile to prevent impurity and collect the lubrication oil from the surfaces of the engine which is helpful for heat dissipation and oxidation prevention. The present study aims at manufacturing a novel high-capacity engine oil pan, which is considered as a complex shaped component with features of thin wall, large size and asymmetric deep cavity through both numerical and experimental methods. The result indicated that it is difficult to form the current part through the common deep drawing process. Accordingly, the hydro-mechanical deep drawing technology was conducted, which consisted of two steps, previous local drawing and the final integral deep drawing with hydraulic pressure. The finite element analysis (FEA) was carried out to investigate the influence of initial blank dimension and the key process parameters such as loading path, draw-bead force and fillet radius on the formability of the sheet blank. Compared with the common deep drawing, the limit drawing ratio by hydro-mechanical deep drawing can be increased from 2.34 to 2.77, while the reduction in blank wall thickness can be controlled in the range of 28%. The formability is greatly improved without any defects such as crack and wrinkle by means of parameters optimisation. The results gained from simulation keep a reasonable agreement with that obtained from experiment trials.

Stretchability and drawability of twinning-Induced plasticity steel-Cored layer steel sheets

Abstracts In this work, the qualCONVERSION(0ities of sheet formability (i.e., stretchability and drawability), of twinning-induced plasticity (TWIP), steel-cored thr$ee-layer steel sheets were investigated in terms of tensile parameters (i.e., strain hardening exponent, strain rate sensitivity, normal anisotropy, mean R -value, and total elongation). The tensile parameters of TWIP steel-cored three-layer steel sheets follow the force-based rule of mixtures. The limit drawing ratio, the measure of drawability, of the three-layer steel sheet was proportional to the mean R -value and the strain rate sensitivity while the limit dome height (LDH), the measure of stretchability, could not be correlated with any tensile parameters. The LDH of the TWIP steel-cored layer sheet was superior to that of the single layer due to the inhibition of serration in the TWIP steel-core during the Erichsen test.

Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.