Influence Of Blank Holder Force Research Articles

Research on stamping formability and process simulation of AZ31 magnesium alloy based on deep learning

To study the formability of AZ31 magnesium alloy under different temperature conditions and improve the forming quality of its parts, this paper aims to solve the minimization problem of pursuing the “maximum thinning rate”. This study obtained the mechanical properties of AZ31 magnesium alloy at 25 °C, 150 °C, 250 °C, and 350 °C through uniaxial tensile tests and explored the stamping formability of AZ31 magnesium alloy mobile phone cases using the finite element inverse calculation method (MSTEP). Based on the hot stamping of AZ31 magnesium alloy at 250 °C, the Monte Carlo Simulation (MCS) method was used to randomly sample the blank holder force, stamping speed, friction coefficient, and resistance coefficient, and then simulate to obtain the corresponding “maximum thinning rate”. In addition, a hybrid prediction model optimized by Genetic Algorithm (GA) and Dung Beetle Optimization (DBO) based on the Back Propagation Neural Network (BPNN) - Random Forest (RF) was used to explore the nonlinear relationship between blank holder force, stamping speed, friction coefficient, resistance coefficient, and the “maximum thinning rate”. The results show that the plasticity of AZ31 magnesium alloy enhances with the temperature increase, especially exhibiting the best stamping formability at 250 °C. Feature importance indicates that the resistance coefficient and stamping speed have a greater impact on the maximum thinning rate, while the influence of blank holder force and friction coefficient is relatively smaller. Mean Square Error (MSE) shows that the predictive capability of the hybrid model is significantly superior to that of the single BP neural network and Random Forest model, displaying optimal efficiency. The predicted maximum thinning rate by the model is 15.39 %, with an error rate of only 0.32 % compared to the DYNAFORM finite element software simulation results, confirming the correctness, accuracy, and effectiveness of the prediction model. Overall, this study provides practical optimization strategies for metal stamping forming processes, with significant practical application value.

Investigation of defect behavior during the stamping of a thin-walled semicircular shell with bending angle

Springback, wrinkling, and thinning typically occur during the stamping of thin-walled semicircular shells with bending angle. These defects cause poor forming accuracy of specimens and lead to assemble difficultly; consequently, the produced specimens do not meet requirements. In this work, the defect behavior during the stamping of thin-walled semicircular shells with bending angle is studied via an analytical model, experiments, and finite element (FE) simulation. First, an analytical model is established to predict springback and analyze springback trend. Second, stamping experimental tests of a thin-walled semicircular shell with bending angle are conducted. The influences of blank holder force (BHF) and stamping speed on the springback, wrinkling, and thinning of specimens are investigated. Finally, an FE simulation model is developed to investigate the deformation characteristics and springback of the thin-walled semicircular shell with bending angle. Results show that the maximum springback decreases with increasing BHF. Meanwhile, the results of the analytical model are consistent with the experimental and simulation results. The maximum thinning rate of the specimen increases with increasing BHF, whereas the wrinkling defect exhibits the opposite trend. The maximum thinning rate and wrinkling of the specimen increase with increasing stamping speed. Compared with that of BHF, the effect of stamping speed on defects is smaller.

Incommensurate vibro-acoustic performance due to in-process blank holder force variation during deep drawing process

Single-stage forming is widely used in automobile industry due to less cycle times, cost-effectiveness and ease of implementation. The continuously adaptable blank holder force (BHF) systems help produce defect-free components during the deep drawing process. However, this manufacturing process induces a significant amount of variability both at geometry and functional performance of the component. A systematic investigation of the effect of small geometrical changes on the vibro-acoustic properties is carried out using a combination of simulations and experiments. The influence of BHF and friction coefficient on vibro-acoustic properties is investigated through forming simulations. The forming analysis results—geometry profile and thinning—are used as an input to predict the vibro-acoustic behaviour of the formed component. The small geometric profile and thickness variations are significant and affect radiated noise-directivity pattern and sound power levels by 1.4 dB. Two physical components are manufactured using a single-stage deep drawing process. The natural frequencies and mode shapes obtained in free-free boundary conditions vary between the two components up to 20% for the first six flexible modes. The sound power levels between the actual parts varied by 2 dB(A). Finally, it is shown that the vibro-acoustic variability is more pronounced at higher frequencies.

Influences of Blank Holder Force in The Multi-Step Deep Drawing Process of Aluminum Sheets

In recent decades, the use of aluminium alloys is developed in the automotive industry with regard to the need for lightweight and anti-corrosion components, one of which is AA7075 Al alloy. In this study, the multi-step deep drawing process of AA7075 aluminium sheets under various blank holder forces is investigated through a numerical simulation and is then validated with experimental results. Simulations were conducted by ABAQUS finite element software, and the influences of the blank holder force on the wrinkling height, rupture occurrence and thickness distribution of the sheet were studied. The optimum amount of blank holder force at each drawing step is determined so that the height of wrinkling, and the thinning percentage do not exceed the permissible value. Based on the results, the blank holder force magnitude should be considered descending during the four successive steps to achieve more uniform thickness distribution, and also the wrinkling height could be reduced by increasing the blank holder force in the analysed force range. The optimum amount of blank holder force in the four drawing steps was 28000, 2500, 1500 and 600 N, respectively. In general, the minimum thickness was created in the corner of the punch. The results also showed that an excessive increase in the blank holder force in order to eliminate the wrinkling caused the thinning percentage to increase. Finally, a good accordance between the experimental and numerical results was observed.

Springback analysis of 6016 aluminum alloy sheet in hot V-shape stamping

Springback behavior of 6016 aluminum alloy in hot stamping was investigated by a series of experiments under different conditions using V-shape dies and a finite element model which was validated reliable was used to further elucidate the springback mechanism. The effects of initial blank temperature, blank-holding force, die closing pressure and die corner radius were studied. It is found that springback decreases remarkably as the initial blank temperature rises up to 500 °C. The springback also reduces with the increase of die holding pressure and the decrease of die corner radius. Under different initial temperatures, the influence of blank-holding force is distinct. In addition, the bending and straightening of the side wall during the stamping process is found to interpret the negative springback phenomenon.

Influence of Blank Holding Force on Stretch Flange Forming of Aluminum Alloy

The effect of blank holding force on the stretch flanging process was investigated using finite element simulation and experimental analysis. Finite element model was used to study the effect of blank holding forces on punch load and forming kinematics. An aluminum alloy 5052 sheet of 0.5mm thickness was employed for this work. Blank holding force has a great effect on punch load and significant influence on forming kinematics. Validation of FEM results were obtained by conducting experiments. A very good agreement was obtained between FEM simulation results in terms of punch load and final shape which shows the accuracy of present finite element model.

Study of the Parameters of Deep Drawing Process Based on the Simulation of Dynaform

A simulation of deep drawing process on the sheet metal was done by using Dynaform, the influence of blank holder force, deep drawing speed and friction coefficient on the forming speed of sheet metal in the deep drawing process were got. The forming speed of sheet metal determines the quality of deep drawing, in the deep drawing process the blank holder force and the deep drawing speed are controllable parameters, the friction coefficient can be intervened and controlled, and it’s a manifestation of the interaction of all parameters, the main factors which influence the friction coefficient just have blank holder force, deep drawing speed and lubrication except the material. The conclusion of this study provides the basic data for the analysis of the lubrication of mould, the study of lubricant and the prediction of the service life of deep drawing die.

Influence of Blank-Holder Force on Springback of Cap-Shape Parts Bending

Springback is the prominent problem in bending forming of sheet metal, which is difficult to control accurately, especially for the complex shaped bending parts. The change of blank-holder force will cause significant changes of bending springback amount. The theoretical analytical model of cap-shape parts bending, which takes into account of the harden ability, anisotropy and elastic deformation of material, is proposed in this paper based on the plane deformation assumption and the bending theory of sheet metal, the cap-shape parts bending of wide sheet is analyzed theoretically, the approximate calculation relational expression is derived between the blank-holder force and springback angle, and the influence of blank-holder force on springback is discussed. In the same conditions, the springback result deduced from theoretical formula is basically consistent with numerical simulation and experiment result.

Numerical Simulation of Cylinder Part Based on Dynaform

The forming process of a typical cylinder part is simulated by the platform of Dynaform. The influence of blank holder force (BHF), punching speed and clearance between punch and die on the quality of forming part is assessed by the orthogonal experimental method. The value of BHF of 20KN, punching speed of 2000mm/s and clearance between punch and die of 1.1mm which are the optimized parameters value are obtained.

Quantitative analysis of surface deflections in the automobile exterior panel based on a curvature-deviation method

A major problem with the evaluation of surface deflection is that panels are evaluated manually and to a great extent subjectivity is involved. For further study on surface deflections such as process optimization, it is necessary to evaluate the defect objectively and quantitatively. In this paper, quantitative analysis of surface deflections in the automobile exterior panel is carried out based on a curvature-deviation method. The curvature-deviation method uses the deviation-based indicators to quantify the surface deflection and uses the local curvature information to filter defect points in evaluation algorithm. In order to verify the effectiveness of the proposed evaluation method, sample panels with a door handle feature are stamped and measured in experiment. The sample panels are made of different materials and are formed under various blank holder forces. A stylus instrument is used to measure eight representative sections in the sample panel. The measurement result is analyzed in a program based on the curvature-deviation method. We also use the oil stoning method to make a subjective evaluation on surface deflection in the sample panel. By analyzing some verification curves and comparing the evaluation results based on the curvature-deviation method with the experimental oil stoning results, it is verified that the proposed curvature-deviation method can analyze the surface deflection accurately and has a good consistency with the stoning-based subjective evaluation method. In addition, the proposed method is applied to analyze the critical values of surface deflection and the influence of blank holder force on surface deflection. The proposed method to quantify surface deflections is beneficial to process optimization, material selection and tool design for automobile exterior panels.

Parametric and non-parametric modelling of earing and hardness of deep drawn cups

This study compares different approaches in modelling the earing phenomenon and hardness of cups in deep drawing process. The blank holder force (BHF), annealing temperature and annealing time of blanks before deep drawing process have been chosen as the three influential parameters on the earing and hardness. To obtain mathematical models for the earing and hardness of the deep drawn cups, the methodology of artificial neural networks have been used. Bayesian network, radial basis function network, Gaussian processes and multilayer perceptron are four different ANN approaches that have been used for the modelling. The research has been conducted on a cold rolled Al–Fe–Si (AA8011A) aluminium sheet. After obtaining the mathematical models describing the influence of BHF and annealing on hardness and earing, a comparison of the proposed models has been performed. A search for the optimal parameters of deep drawing process has been carried out.

Investigation of the Hot-Stamping Process for Advanced High-Strength Steel Sheet by Numerical Simulation

Hot forming is a new way to manufacture complex-shaped components of advanced high-strength steel (AHSS) sheet with a minimum of spring-back. Numerical simulation is an effective way to examine the hot-forming process, particularly to determine thermal and thermo-mechanical characteristics and their dependencies on temperature, strain and strain rate. The flow behavior of the 22MnB5 AHSS is investigated through hot tensile tests. A 3D finite element (FE) model of hot-stamping process for the Open image in new window shaped part is built under the ABAQUS/Explicit environment based on the solutions of several key problems, such as treatment of contact between blank and tools, determination of material characteristics and meshing, etc. Numerical simulation is carried out to investigate the influence of blank holder force (BHF) and die gap on the hot-forming process for the Open image in new window shaped part. Numerical results show the FE model is effective in simulation of hot-forming process. Large BHF reduces the amount of spring-back and improves the contact of flange with tools while avoiding cracking of stamped part. Die gap has a considerable influence on the distribution of temperature on side walls; the larger the die gap, higher is the temperature on the sidewall of Open image in new window shaped part.