Blank Holder Pressure Research Articles

Investigation of tribological performance of hydrothermal carbon by pin-on-disc test and warm deep drawing process

In this study, the synthesis of hydrothermal carbon (HTC) lubricant and its usability as a lubricant under hot industrial conditions were investigated. In this context, the characterization of HTC produced from organic sources at low cost and in a short time was performed, and its tribological performance was analysed in detail. HTC produced by the hydrothermal carbonization method was characterized through SEM images and EDS analysis. To determine the effect of HTC on friction at different temperatures, HTC was subjected to a pin-on-disc wear test with AA5754 material. The effect of various lubricants, temperatures, blank holder pressure, and forming speed parameters on the forming force for the analysis of the tribological effect of HTC on deep drawing processes were statistically analysed. The performance of HTC was compared with Teflon, fullerenes, graphene, and carbon nanotube (CNT) materials. According to the results obtained from wear tests, the lowest friction coefficient value was achieved in the presence of fullerenes as the lubricant, and as the temperature increased, the friction coefficient decreased. It was observed that HTC exhibited lower performance in the wear test compared to fullerenes due to oxidation. When the effect of deep drawing parameters on the forming force was analysed, it was concluded that the most effective parameters were temperature (72.32%) and lubricant (20.89%). According to the S/N analysis results, the minimum forming force was obtained under the conditions of solid Teflon lubricant, 250 °C temperature, 15-bar blank holder pressure, and 2 mm/s forming speed. The tribological performance difference between HTC and Teflon is at the 1% level. The results demonstrate the potential industrial usability of HTC as a lubricant.

Controlling non-uniform blank holder pressures in an extra-deep drawing process for enhancing formability and product quality

Controlling non-uniform blank holder pressures in an extra-deep drawing process for enhancing formability and product quality

Development of forming process for deep drawing of square cup with optimized blank holder pressure

Development of forming process for deep drawing of square cup with optimized blank holder pressure

The Comparison of the Multi-Layer Artificial Neural Network Training Methods in Terms of the Predictive Quality of the Coefficient of Friction of 1.0338 (DC04) Steel Sheet.

Friction is one of the main phenomena accompanying sheet metal forming methods, affecting the surface quality of products and the formability of the sheet metal. The most basic and cheapest way to reduce friction is to use lubricants, which should ensure the highest lubrication efficiency and at the same time be environmentally friendly. Due to the trend towards sustainable production, vegetable oils have been used in research as an alternative to petroleum-based lubricants. The analysis of friction in sheet metal forming requires an appropriate tribotester simulating the friction conditions in a specific area of the sheet metal being formed. Research has used a special strip drawing tribometer, enabling the determination the value of the coefficient of friction in the blankholder zone in the deep drawing process. Quantitative analysis of the friction phenomenon is necessary at the stage of designing the technological process and selecting technological parameters, including blankholder pressure. This article presents the results of friction testing of 1.0338 (DC04) steel sheets using a strip drawing test. The experimental tests involved pulling a strip of sheet metal between two countersamples with a rounded surface. The tests were carried out on countersamples with different levels of roughness for the range of contact pressures occurring in the blankholder zone in the deep drawing process (1.7-5 MPa). The values of the coefficient of friction determined under dry friction conditions were compared with the results for edible (corn, sunflower and rapeseed) and non-edible (Moringa, Karanja) vegetable lubricants. The tested oils are the most commonly used vegetable-based biolubricants in metal forming operations. Multi-layer artificial neural networks were used to determine the relationship between the value of the contact pressure, the roughness of the countersamples, the oil viscosity and density, and the value of the coefficient of friction. Rapeseed oil provided the best lubrication efficiency during friction testing for all of the tested samples, with an average surface roughness of Sa 0.44-1.34 μm. At the same time, as the roughness of the countersamples increased, a decrease in lubrication efficiency was observed. The lowest root mean squared error value was observed for the MLP-4-8-1 network trained with the quasi-Newton algorithm. Most of the analysed networks with different architectures trained using the various algorithms showed that the kinematic viscosity of the oil was the most important aspect in assessing the friction of the sheets tested. The influence of kinematic viscosity on the value of the coefficient of friction is strongly dependent on the surface roughness of the countersamples.

Investigation on the Effect of Blank Holder Force and Initial Blank Size on the Thinning Problem of the Fuel Tank Part Made from Aluminum Alloy Sheet 5754-O under Deep Drawing Process

Deep drawing process is a common sheet metal forming technique in motor vehicle manufacturing. There are three primary defects that could be occur in deep-drawn parts: tearing, wrinkling, and thinning. When the thinning is difficulty detected by visual inspection. As a result, this study aims to address the thinning issue in a fuel tank part made from an aluminum alloy sheet AA5754-O 1.5 mm thick under cold working deep drawing process, while the manufacturer's desired upper limit for thinning is 20%. Two influential parameters viz. blank holder force and initial size of blank, were investigated and optimized by using Finite Element Analysis (FEA) through PAM-STAMP simulation software with the validated material model was based on Hill’s 1948 anisotropic yield criterion with Swift hardening law. The mechanical parameters in the mentioned model were derived from the results of uniaxial tensile tests. In conclusion, both the hydraulic cushion's blank holder pressure and the initial size of the blank were found to influence the thinning of the part, either individually or in combination. Despite optimizing both parameters, they were unable to consistently achieve the desired limit.

An extended stress-based forming limit diagram focusing on the wrinkling phenomenon and the effect of the normal pressure on clamped surfaces

A novel wrinkling limit representation following the pattern of the conventional forming limit curves (FLCs) and the stress-based forming limit curves (SFLCs) as well as the application of the assumed criterion in finite element modelling are discussed in this manuscript. FLCs can partially refer to the wrinkling potential in the area left to the uniaxial tension line, but just like the SFLCs, cannot characterize the limits of the material behavior in a deeper sense, if negative in-plane stress and normal pressure act together on the sheet. This study predicts the wrinkling risk of clamped surfaces with a stress-based criterion through solving the analytical equations of the critical compressive stress causing wrinkling, and the corresponding blank holder pressure. The critical values were calculated based on the Wang and Cao’s theory using Hill48 anisotropic yield function coupled with the Swift hardening law. The results draw a novel wrinkling limit curve representation methodology, in which the minor stress responsible for wrinkling and its ratio to the major stress are distinguished in the function of the applied blank holder pressure. The applicability of the calculated curves was investigated using finite element simulations, which showed that this method provides the opportunity to quantitatively interpret how close a component is to the wrinkling limit. The calculated wrinkling tendencies were verified by standard cup drawing tests supplemented by round shape error measurements on three different automotive steel sheets. It can be stated that the obtained numerical conditions of wrinkling were fitted to the experiments fairly well.

An Attempt to Evaluate and Optimize the Hydroforming of Fiber Metal Laminates with the Comprehensive Forming Limit Curve

Although some papers have studied the formability of fiber metal laminates (FMLs), there is still a lack of a standard criterion for the engineering field. To give a standard for predicting the failure and provide the optimized method of the hydroforming process for FMLs, a comprehensive forming limit curve (FLC) was established by a hydro-bulging test method. The influence of pressure rate (PR), blank holder pressure (BHP), and temperature (T) was studied in this paper. Both theoretical and experimental results showed that the higher BHP and PR have a significant negative effect on limit height, while increased T has a positive effect. Moreover, the semi-cured forming of a real part was evaluated by this FLC for the very first time and the improvement suggestions of process parameters were given based on the comprehensive research. Finally, the real part that met the quality requirements was obtained by numerical simulation and trial production, which verifies the effectiveness of this comprehensive FLC.

Pressure Distributions in Deep Drawing with a Passive Cardanic Blank Holder

Deep drawing processes are strongly influenced by the blank holder forces, as well as their local distribution. In current deep drawing tools, this pressure distribution is dominated by the compliance of the specific machine the tool is mounted on. Therefore, each tool must be manually polished to enable the desired distribution of the blank holder pressure. This regularly causes problems when transferring tools from one machine to another, for example from a try-out press to a regular press line. As both machines have unique compliances, the pressure distribution on the flange of the drawn part changes. Additional manual spot grinding is needed to achieve the desired pressure distribution on the flange. To counteract this problem, the use of a passive cardanic blank holder is proposed in this paper. The cardanic blank holder can freely tilt around two axes, which leads to an auto-leveling effect of the blank holder on the sheet, resulting in a more uniform blank holder pressure. This effect is demonstrated experimentally using pressure sensitive film on the same tool with two different blank holders, one equipped with a conventional blank holder, the other with a cardanic blank holder. To demonstrate transferability, the experiments are repeated on multiple single acting presses. The contribution will present and discuss the resulting pressure distributions.

Variable blank holder pressure by magneto-rheological actuators in deep drawing

Deep drawing is one of the most used processes in industry, whose reliability is closely linked to the possibility of adequate control of the blank holder force (BHF). To avoid typical failure mechanisms, such as wrinkling and tearing, it is necessary to properly adjust the BHF during the process. The paper presents the design of a new blank-holding set-up based on magneto-rheological actuators, which allow a flexible adjustment of the force during the process. A closed-loop control, based on the direct detection of the metal sheet displacement under the blank holder, is implemented to regulate in real-time the actuator's load. The obtained experimental test results show that (i) the presented set-up allows to apply blank holder pressures with an average error less than 5% with respect of the target forces; (ii) the low latency times to allow the force variations, and (iii) the possibility to vary in real-time the blank holder load response during the deep drawing.

Investigation into a comprehensive forming limit curve considering multi-parameters effects for semi-cured FMLs through uniform pressure loading test

Recently, hydroforming has paid dividends in composite forming due to its uniform pressure distribution, which helps in reducing the delamination defects. Considering the need to develop an appropriate criterion for evaluating the formability of FMLs, inspired by sheet metal forming and testing, the uniform pressure loading test was adopted to characterize the formability of semi-cured FMLs by forming limit curve ( FLC). In this paper, both theoretical analysis models considering and ignoring the tangential cohesive effect were established, and the stress expression of the critical zone was given. The results show that the tangential cohesive stress demonstrates a non-negligible influence on the FLC. A new form of comprehensive FLC was given by defining global equivalent strain and global strain ratio and analyzed by the finite element method. In addition, the numerical simulation model and the experimental parameters were verified. A simplified Hashin criterion was proposed and developed into the numerical simulation as a subroutine based on theoretical analysis. Parameters such as blank holder pressure, pressure rate, and temperature were considered both in experiments and simulation. Only fiber stretching damage was distinguished in the cross, single, and arc crack but no wrinkling. As predicted theoretically, a lower forming limit is expected when FMLs are subjected to greater tangential cohesive stress. Finally, with the help of numerical simulation, the influence of different boundary conditions on the comprehensive FLC was studied. Instead of a simple evaluation of FMLs, this comprehensive FLC could be used directly to optimize hydroforming processes in the engineering field.

A Study on the Impact of Blank Holder Pressure on Forming Pressure and Product Quality in Hydrostatic Forming

A Study on the Impact of Blank Holder Pressure on Forming Pressure and Product Quality in Hydrostatic Forming

Deep Drawing Behavior of Metal-Composite Sandwich Plates.

The deep drawing behavior of metal-composite sandwich plates, or fiber-metal laminates, in which aluminum or steel sheets are used as the face layer and composite materials are used as the core layer, is discussed in this work to find the workpieces without fractures and wrinkles. Two types of aluminum, 1050 and 6061, are considered their suitability as face sheets. The preheat effect of aluminum 6061 on formability is also investigated. When steel sheets are used, the effect of blank-holder pressure is included. In addition, to understand the deformation of fabric composite, pure composite laminates are deep drawn. The results of composite laminates show that after drawing, the weft and warp lines are shorter than the other radial lines, causing the specific deformed shape and the variation of the fiber intersection angle. For Al-composite sandwich plates, fractures and wrinkles are easy to occur. Even though the fracture and wrinkle conditions are released with the increase in preheating temperature of aluminum 6061, it may be not enough. For the deep drawing of the steel-composite sandwich plates, in which fractures are avoided, the increase of blank-holder pressure could reduce the wrinkle number. Hence, good quality workpieces without fracture and wrinkle could be obtained when the blank-holder pressure is high enough.

Analysis of the Mechanical and Preforming Behaviors of Carbon-Kevlar Hybrid Woven Reinforcement

Carbon-Kevlar hybrid reinforcement is increasingly used in the domains that have both strength and anti-impact requirements. However, the research on the preforming behaviors of hybrid reinforcement is very limited. This paper aims to investigate the mechanical and preforming behaviors of carbon-Kevlar hybrid reinforcement. The results show that carbon-Kevlar hybrid woven reinforcement presents a unique “double-peak” tensile behavior, which is significantly different from that of single fiber type reinforcement, and the in-plane shear deformation demonstrates its large in-plane shear deformability. Both the tensile and in-plane shear behaviors present insensitivity to loading rate. In the preforming process, yarn slippage and out-of-plane yarn buckling are the two primary types of defects. Locations of these defects are closely related to the punch shape and the initial yarn direction. These defects cannot be alleviated or removed by just increasing the blank holder pressure. In the multi-layer preforming, the compaction between the plies and the friction between yarns simultaneously affect the quality of final preforms. The defect location of multi-layer preforms is the same as that of single-layer, while its defect range is much wider. The results found in this paper could provide useful guidance for the engineering application and preforming modeling of hybrid woven reinforcement.

Comparative study of formability characteristics in deep drawing of DP 590 steel using analytical models

ABSTRACT The aim of the present work is to perfectly utilise the resources with minimal wastage of material by the implementation of theoretical models for prediction of different responses of deep drawing viz., limiting drawing ratio (LDR), and maximum drawing load (MDL). Initially, some trial and error experimental and finite element (FE) simulations are performed to find the coefficient of friction (COF) values under lubricated (L) and non-lubricated (NL) conditions which is difficult to find from experiments. The various processing conditions like temperature, blank holding pressure (BHP), blank diameter and lubrication are used as input. The coupled effect of temperature and lubrication helped in increasing the formability of the material and also reduced the maximum load required to draw the cup. The experimental limiting drawing ratio (LDR) was observed to be 1.933 under 400°C lubricated condition which is 3.53% more than other processing conditions. Further, several models namely: Leu, Whiteley, Hosford, Atkinson, Siebel, Siebel-Beissiwagner, Lange and Groover have been applied for the prediction of LDR and MDL among which Leu’s and Siebel’s analytical relation has displayed the least error of 2.452% and 7.977% respectively.

Zoning Lubricant Die Application for Improving Formability of Box-Shaped Deep Drawn Parts

The ‘formability’ of sheet metal is a major keyword referring to process design in the sheet metal forming industry. Higher formability could reflect lower production costs and time. Many studies have been carried out to improve formability in various ways, by using the finite element method and experimental approaches. In the present research, a new zoning lubricant technique is proposed. The stainless steel SUS304 square deep drawn box is used as an investigative model. Based on the material flow analysis, we found that zoning lubricant die application could reduce the difference in material flow velocity between wall and corner zones. This material flow characteristic resulted in decreased nonconcurrent plastic deformation during the deep drawing process, as well as decreased stretching in the cup wall and the delaying of the fracture. In the present research, the design of the zoning lubricant die was strictly concerned with achieving functionality related to the friction coefficient, area of zoning, and blank-holder pressure. A smaller friction coefficient positioned in the corner zone and larger friction coefficient positioned in the wall zone are recommended. It was revealed that, by appropriate zoning lubricant die application, formability could be increased in terms of box height by approximately 7 mm or 10%.

Investigation of the formability behaviour of optimized tufted and un-tufted multi-layer carbon preforms during the stamping process

The originality of this work consists of studying the stamping behaviour of tufted and un-tufted multi-layer carbon preforms. Several tufted preforms with different stratifications have been manufactured. The stamping test was carried out using a hemispherical punch and conducted at two blank-holder pressures (0.05 and 0.2 MPa). The experimental data show that the addition of tufting yarn, the number of layers and the blank-holder pressure significantly affected the forming behaviour: the tufted preform presents a higher punch force, lower material drawin and shear angles with significant structural defects than the un-tufted preform. The increase of the blank-holder pressure increases all these characteristics and emphasizes the structural defects on the fibrous reinforcements. Similarly, the transition from two layers to four layers lamination at the same blank-holder pressure is followed by an increase of the punch force, reducing the material draw-in and the shear angles especially those measured at the transient zone, and causes more structural defects on all stamped preforms. Therefore, two localized tufting configurations, Right Localized Tufted and Inclined Localized Tufted, at the stamping transition area have been proposed. The results show that these two configurations present a minimum punch force and a maximum material draw-in similar to those measured on the un-tufted structure. The shear angles are much greater than those recorded on the conventionally (fully) tufted preform. Thus, the localized tufting in the most stressed areas proves to be the most suitable solution for the stamped preforms.

On the thinning variations in hydrostatic forming of sheet metal

In sheet metal forming, thinning phenomenon is one of the most concerned topics to ameliorate the final quality of the manufactured parts. The thinning variations depend on many input parameters, such as technological parameters, geometric shape of die, workpiece’s materials, and forming methods. Hydrostatic forming technology is particularly suitable for forming thin-shell products with complex shapes. However, due to the forming characteristics, the thinning variations in this technology are much more intense than in other forming methods. Therefore, in this paper, an empirical study is developed to determine the thinning variations in hydrostatic forming for cylindrical cup. Measurement of thickness at various locations of deformed products are conducted to investigate the thickness distribution and determine the dependence of the largest thinning ratio on the input parameters (including the blank holder pressure, the relative depth of the die and the relative thickness of the workpiece). The results are expressed in charts and equation which allow determining the effect of each input parameter on the largest thinning ratio.

Experimental and numerical analysis of aluminium alloy cylindrical cup using novel deep drawing technique

ABSTRACT In the traditional deep drawing process, a blank holder is required to press the blank over the die to prevent wrinkling and to control the material flow into the die cavity. But, this important tool responsible for fracture on the sheet and the optimisation of blank holder pressure is very critical. This present study introduces a new technique for the deep drawing process of cylindrical cups through a conical die without a blank holder. In this new technique, cylindrical cups are produced by pushing a circular blank using a flat-headed cylindrical punch through a conical die with a cylindrical throat in a single punch stroke. A 3-D parametric FE model was built using the commercial FE package ANSYS/APDL-19. A die with a half cone angle of 18° has shown the best drawability for the new technique. A flat-headed punch was used for forming of AA8011 & AA1200 with 1 to 2 mm initial thicknesses and diameters varies from 45 to 65 mm in experimental analysis. 100-ton hydraulic press used for deep drawing setup. Finite element model results showed good agreement with experimental results. Experimentally, a cylindrical cup with a LDR of 2.5 has been successfully achieved.

Investigation of the formability behaviour during stamping of tufted and un-tufted carbon preforms: towards localized reinforcement technologies

The originality of this work consists in the study of the stamping behaviour of tufted and un-tufted carbon preforms. Several preforms by varying the tufting thread orientations (0°, 90° and 0°/90°) and with different stratifications ([0°/90°,-45°/+45°] and [0°/90°,-45°/+45°]2) were manufactured in order to study their out-of-plane deformability. The stamping test was carried out using a hemispherical punch and conducted at two blank-holder pressures (0.05 and 0.2 MPa). The experimental data highlight the influence of tufting threads on the forming force, maximum material draw-in, shear angle mapping and wrinkling phenomenon during the forming process. Furthermore, the orientations of tufting thread, the number of layers and the pressure of the blank-holder significantly affected the forming behaviour: all tufted preforms present a higher forming force, lower maximum material draw-in and shear angles and notable structural defects than the un-tufted preform. The increase in the pressure of the blank-holder from 0.05 to 0.2 MPa increases all these characteristics and emphasizes the structural defects on the fibrous reinforcements. Similarly, the transition from two layers to four layers in lamination at the same blank-holder pressure is followed by an increase of the forming force required for stamping operation, reducing the material draw-in and the shear angles especially those measured at the transient zone, and causes more structural defects on all stamped tufted and un-tufted preforms. For all these reasons, two localized tufting configurations, Right Localized Tufted (RLT) and Inclined Localized Tufted (ILT), at the stamping transition area are proposed. The stamping results show that these two original configurations present a minimum punch force and a maximum material draw-in similar to those measured on the un-tufted structure. The shear angles are higher than those recorded on the conventionally tufted preforms (over the entire surface).

Analysis of the Stamping Speed for Sheet Metal Forming of Aluminum Alloy 5052-H112

Deep drawing is the most advanced sheet metal forming technique. In today’s demanding environment is the global environment and energy saving, the process has been supposed to play a vital role in light-weight component industry. Light-weight, high strength, low density and extreme corrosion aspects must be almost guaranteed in a deep drawn product. However, due to those requirements, thinning and wrinkling and other defects will be increased also. Numerous elements such as blank-holder pressure, punch force, speed of punch, blank shape, thickness variation, surface-to-surface friction coefficient, material characteristic,…influenced to the success of methods as well as the quality of the products. In addition, worldwide manufacturers keep getting the most goods done in less time. Indeed, the increasing of productivity should be also dealt because it proportionally relates to the stamping speed. This paper investigates the influence of punch velocity on deformation behavior of aluminum alloy 5052–H112. Finite Element Method was used to perform Nakajima test at several of punch velocities of specimen widths and monitor fluctuations in magnitude of von Mises stress, the major strain and minor strain. Forming Limit Curve (FLC) was obtained at different velocities and almost uniform. Stretching and sliding across the top of the punch resulted in thinning of sheet metal. Beside this, the action of punch stroke resulted in the production of more von Mises concentrated stress and the largest specimen in widths had shown the peak value of von Mises stress compared with the other specimens at all different velocities. Furthermore, the ratio of the major strain to the minor strain is influenced by the mass of material at the contact area and keeps consistent over the variation in velocities of punch. This will pave the way for future studies of the optimization of the stamping speed in deep drawing.