Blank Thickness Research Articles

A comprehensive validation of GRA with ant colony optimization for robust optimal design: A case study on the forming process

Sheet metal forming design involves numerous factors and controlling all these parameters to prevent cracks is a major challenge to maintain the quality. Therefore, the careful selection of process parameters is critical for ensuring product longevity. Several researchers employed different techniques for optimal selection of process parameters but consistency among the techniques and validation of results in real time scenarios will play a pivotal role in determining the suitable parameters. Therefore, the current work presents a validation method of Grey Relational Analysis (GRA) results with Ant Colony Optimization (ACO) for the robust optimum design with an illustrative example of forming process. Al 6061 – T6 alloy was chosen as a material for deep drawing process and L27 Orthogonal Array was planned to conduct experiments with four input parameters such as blank thickness, Die and Blank Temperature, Die Speed, Lubrication at three levels each. Punch force and Thickness variation were considered as the output parameters. GRA Technique was implemented to find the best optimal combination and regression equation was developed to predict the nature of objective function. These results were given as an input to ACO, a nature inspired algorithm to search for the optimal solution with in the design space. Sensitivity analysis has also been performed to highlight the effectiveness of the proposed solution in terms of solution quality and computational efficiency. The ACO method, GRA technique and the experimental results are almost similar with a margin of acceptable deviation. The results indicated the robustness of the projected approach in achieving the quality of solution.

Lightweighting an automotive fuel tank through formability analysis

For lightweighting automotive sheet metal parts, it is important to use the right grade/material with the minimum possible initial blank thickness in the forming processes. Fuel tank is one of the most critical sheet metal parts in automobiles due to its complex shape and large depth. In this work, a simulation-based approach has been employed to study the feasibility of lightweighting an automotive fuel tank (for two wheelers) by reducing blank thickness and changing steel grade. Formability analysis has been carried out using numerical simulations of a 0.8 mm thick sheet of Extra Deep Drawing (EDD) steel which is being used to manufacture the fuel tanks. Simulations have been performed to find out the minimum initial sheet thickness which can be formed successfully without failure or excessive thinning. From the predictions of formability, thinning, and strain distributions in the formed parts, it has been found that the weight of the part can be reduced by 12.5% by reducing the initial thickness from 0.80 to 0.70 mm. To reduce the thickness further, simulations have also been carried out by changing the grade from EDD steel to Interstitial Free (IF) steel which has superior drawability than EDD steel. It has been found that the blank thickness can be further reduced to 0.65 mm in the case of IF steel which is expected to result in 19.0% reduction in the weight of the component. The predictions have been validated by the actual press trials in the industry with reduced sheet thickness. The predicted strain distribution and thinning in the formed parts have also been validated with the experimental press trails. In addition to the weight reduction, the proposed change in thickness and grade would lead to a reduction of 16.5% and 4.0%, respectively, in the raw material cost of the fuel tank.

Comparative Analysis of Finite Element Formulations for Simulating Hot Forming of Ti-6Al-4V Aerospace Components

This study presents a comprehensive finite element analysis to compare the performance of different element formulations (classic shell elements, solid elements, and continuum shell elements) in simulating the hot-forming process at 725 °C of a complex Ti-6Al-4V aerospace component with an initial blank thickness of 1.6 mm (0.063 inches). The Ti-6Al-4V blank is modeled as a deformable body exhibiting anisotropic plastic behavior, whereas the forming tools (matrix and punch) are assumed to be rigid bodies. The simulation accounts for temperature and strain rate effects on the material properties, incorporating phenomena such as friction and anisotropy. Three different element types are studied and compared: S4R and S4 (classic shells), C3D8R and C3D8 (solids), and SC8R (continuum shell with reduced integration). Finally, the model is validated by comparing the predicted final part geometry, especially the thickness distribution, against the experimental measurements. The model can also predict the springback effect on the final geometry. The SC8R continuum shell element provides the smoothest representation of thickness variations along critical regions of the final part. The study highlights the importance of selecting the appropriate element type for the accurate simulation of hot-forming processes involving large deformations and complex contact conditions. The ability of continuum shell elements to accurately capture the thickness variations makes them an ideal candidate for such applications.

Predictive and experimental analysis of forces in die-less forming using artificial intelligence techniques

The use of a novel technology for producing the components of lightweight materials and to reduce the requirements of power utilized during manufacturing processes can be a great aspect to decrease pollution and save resources. Single point incremental forming (SPIF) is the viable and novel approach for manufacturing the parts of high strength and lightweight materials without involving dedicated tools and dies economically. This die-less forming technique outperforms the conventional forming techniques by saving the energy and materials. In this work, the estimation and investigation of forming forces have been accomplished to ensure the secure uses for the SPIF machines for performing this process for the designed conditions on AA2024 sheets which is a lightweight aluminum alloy being widely used in aerospace and automotive sectors. To predict the peak deforming load, machine learning (ML) techniques are employed in the current work along with the artificial neural network (ANN) by taking experimental results as the input dataset. The proposed ML model revealed better accuracy (99%) than previous work performed using similar approaches. The proposed ANN model produced lower mean absolute percentage error 4.35 as compared to other models. Authors also calculated the computing time taken during estimation of forming force. Combination of the Flatend-R1 tool and the 1.6 mm blank thickness increased the deforming loads drastically and can become the limiting factor for forming machine which should be avoided whereas the combination of hemispherical tool and lower blank thickness (0.5 mm) reduced the deforming loads that are needed to manufacture the conical frustum. It was also noticed that as the tool shape was changed from hemispherical-end to Flatend-R1, the axial peak forces were increased by 13.16%, 16.59%, 20.43%, and 22.78% for the levels 1, 2, 3, and 4 of the blank thickness, respectively.

Experimental and numerical investigations of Al 1100 cup using conical die without blank holder

In sheet metal forming processes, the wrinkle phenomenon has been one of the main limiting failure factors. Both numerically and experimentally investigations were done using conical cup test method for wrinkling phenomena. This research work aim is to drawing a flat-bottom cylindrical cup from Al 1100 sheet material, with the effect of drawing parameters, including blank shape, blank thickness, load, and dry lubrication, employing both numerical and experimental methods. Simulation results were obtained using ANSYS 19.2 software, while experimental data were acquired through a universal testing machine. The optimization of process parameters led to the formation of a cylindrical cup with a flat bottom and no defects like thinning or wrinkling. This parametric research contributes to the accurate prediction of the final geometry of the sheet blank and the distribution of stresses, crucial for the forming process and the production of high-quality products. The results show that a die angle of 20° and an optimized punch speed of 3.5 mm/sec give the wrinkle-free cup with high compressive strength.

Experimental characterization and prediction of forming limit diagrams of PHS1800 during hot stamping

The use of press-hardening steels (PHSs) in automotive bodies creates the opportunity of producing thinner, higher-strength components. PHS1800, an Al-Si coated PHS grade with ultimate tensile strength of around 1.8 GPa after hot stamping, is a candidate material for vehicle anti-intrusion applications. The current study aims to investigate the formability of this steel during the hot-stamping process. A custom Marciniak punch test and in situ digital image correlation (DIC) techniques were used to determine the in-plane forming limits of this steel during quenching from an austenitic temperature. The carrier blank thickness and geometry were exploited to quench the surrounding material of the specimens while promoting localization in their central regions. Approximately linear strain paths ranging from uniaxial to biaxial stretching were obtained in the tests while avoiding friction and out-of-plane bending. The forming limit curves (FLCs) of the material under various hot-stamping conditions were then predicted using the Marciniak-Kuczyński (MK) model, taking into account the temperature and strain-rate histories. The predicted limit strains were in good accord with the measured data.

Control System for Automated Technological Process of Hot Stamping-A Case Study.

Hot forming process has been used more and more frequently in the production of body structures of modern ultralight passenger cars for several years. This, unlike the commonly used cold stamping, is a complicated process, combining heat treatment and plastic-forming methods. For this reason, permanent control at each stage is required. This includes, among others, measurement of the blank thickness, monitoring its heating process in the suitable atmosphere in the furnace, control of the forming process itself, measurement of shape-dimensional accuracy as well as mechanical parameters of the finished drawpiece. This paper discusses the method of controlling the values of production parameters during the hot stamping process of a selected drawpiece. For this purpose, digital twins of the production line and the stamping process, made in accordance with the assumptions of Industry 4.0, have been used. Individual components of the production line with sensors for monitoring process parameters have been shown. The system's response to emerging threats has also been described. The correctness of the adopted values is confirmed via tests of mechanical properties and the assessment of the shape-dimensional accuracy of a drawpiece test series.

Analysis of Roller Tip Radius and Blank Thickness on The Aluminium Bowl Forming by Metal Spinning Method

Analysis of Roller Tip Radius and Blank Thickness on The Aluminium Bowl Forming by Metal Spinning Method

Analysis of Roller Tip Radius and Blank Thickness on The Aluminium Bowl Forming by Metal Spinning Method

Metal spinning is used to form a circular metal plate by rotating the blank at high speed and then applying pressure using a roller regularly. So that, its shape will follow the shape of the mold or mandrel. There are still a few bowl-making industries in Indonesia that use the metal spinning method. In general, still use the manual method. The purpose of this study is to find the right and efficient parameters to produce the thickness and height of the bowl as expected. The method used in this study uses experimental data collection. This study uses variations in the radius of the roller tip with variations of 2 mm, 4 mm, and 6 mm, and variations in the blank thickness of 1 mm, 1.2 mm, and 1.4 mm. The results obtained from this study are good interaction results, namely a roller tip radius of 2 mm and a blank thickness of 1.4 produces the most appropriate formability, where a roller tip radius of 2 mm results in high elongation of the workpiece. The metal workpiece is given to experience deformation plastic without being damaged or torn and at a thickness of 1.4 mm experienced an increase in an area up to 44.6% from the initial blank position.

GA-based optimization to control the thickness distribution in components manufactured via superplastic forming

Superplastic forming (SPF) is a net-thinning sheet metal forming process that allows to achieve very complex geometries; nevertheless, due to its deformation mechanics, it is difficult to achieve a uniform thickness distribution in the final component since the most stretched regions of the blank are contemporarily characterized by the most severe thinning. With the aim of proposing a robust approach, a new methodology able to optimize the thickness distribution in components produced by SPF is proposed. Although two different titanium-based (Ti-6Al-4 V ELI) axisymmetric components – i.e., a hemisphere and a frustum of cone – were chosen as case studies, the methodology can be extended to any material and to any geometry, even considering more than one objective function. The superplastic forming was numerically simulated, and the Finite Element (FE) model was embedded into an automatic procedure managed by the multi-objective genetic algorithm MOGA-II. The blank's initial thickness distribution was modelled using a second-order polynomial function and its coefficients were determined to get, at the end of the SPF process, a uniform thickness in the formed part irrespective of the specific geometry. Titanium blanks were machined on a 5-axis milling machine to obtain the calculated optimal initial thickness distribution; subsequently, such blanks were superplastically formed and inspected in order to measure the thickness distribution. Tests showed a very good fitting with the numerical prediction thus confirming the robustness and the effectiveness of the proposed methodology.

Estimating Forming Conditions for Deep Drawn SUS304 Square Cups Having no Delayed Cracks Using FE Simulation

Forming conditions for deep drawn SUS304 square cups having no delayed cracks are determined using finite element (FE) simulations based on the threshold % of wall thickening for delay cracking obtained from deep drawing tests of SUS304 cylindrical cups. The maximum drawing ratio and the initial blank thickness are fixed at 1.87 and 0.8 mm, respectively in this study taken into the considerations of the capacity of the press machine i.e., 100 kN. The blank holding forces (BHF), punch corner radius, rp and die corner radius, rd are varied to obtain 75 mm x 75 mm square cups having % of local thickening less than the threshold value i.e., 47% in the cracking zones located adjacent to the top corners of the cups. A quarter 3D FE simulation model of the deep drawing process is constructed, the wall thickness distributions of the cups are calculated. The simulation results showed that the forming conditions for the crack-free cups could be obtained with BHF ≥ 47 kN, rp ≥ 8.5 mm and 6.8 mm ≤ rd ≤ 9.5 mm. A method for designing the forming conditions of deep drawn SUS304 square cups is proposed in this study.

Computerized analysis of traveling wave vibration characteristics of aviation thin-walled spiral bevel gears

Aviation thin-walled spiral bevel gears are prone to traveling wave vibration. This study proposes an efficient traveling wave vibration analysis method based on the contact finite element model of the spiral bevel gears. The excitation vibration modes under the typical working condition is obtained through comparison to the modal analysis and harmonic response analysis. The resonance modes and frequencies are determined by Campbell diagram. The effect of thin-walled structure parameters on the traveling wave vibration of aviation spiral bevel gears is investigated. The results show that the traveling wave vibration of the gear is easily excited by the forward traveling wave and backward traveling wave resonance of 2nd nodal diameter/1st nodal circle, forward traveling wave resonance of the 6th nodal diameter, backward traveling wave resonance of 7th nodal diameter. The increase of gear blank web thickness will decrease peak stresses. The increase of conical web thickness and angle will decrease the peak stresses of compound vibration. The adjacent modals will aggravate the vibration. The decrease of the modal frequency spacing will increase the peak stresses.

Selection of Constitutive Material Model for the Finite Element Simulation of Pressure-Assisted Single-Point Incremental Forming

Pressure-assisted single-point incremental forming (PA-SPIF) is one of the emerging forming techniques for sheet metals that have been the subject of rigorous research over the past two decades. Understanding of its forming mechanisms and capabilities is growing as a result. Open gaps are still present in material constitutive modelling for accurate numerical predictions and finite-element simulations as the characteristics of localised deformation behaviour in SPIF are different from those of conventional sheet metal forming. The current investigation focused on the comparison of three different material models for the finite-element analysis of PA-SPIF of cold-rolled, dual-phase steel DP600. Experimental trials using different fluid pressures showed good agreement with simulation results with discrepancies in deformed blank thickness and shape geometry predictions of 3–11% and 10–21%, respectively. Within the tested materials and range of parameters, the fracture-forming-limit diagram (FFLD) material model was identified to be of superior accord with experiments.

Process Optimization and Die Design of Hydromechanical Calendering Based on Wireless Network Communication and IoT

Aiming at the problem of the study, of high error probability in the practical application of traditional hydromechanical calendering process, the hydromechanical calendering process is optimized based on wireless network communication. GPRS or LORaipot-IOT wireless communication mode is adopted to calculate the impact kinetic energy of hydromechanical calendering, and the simulation model of hydromechanical calendering is built based on AMESim. The characteristics of hydromechanical calendering are analyzed. The oil pressure is controlled by setting the pressure adjusting valve and adjusting the spring pressure to realize the optimization of the hydromechanical calendering process. On this basis, the grinding tool is designed, and the clearance between punch and die is reserved to prevent the blank from cracking. The experimental results show that the error probability of hydromechanical calendering with the optimized design process is significantly lower than that of the control group, which can solve the problem of high error probability of traditional hydromechanical calendering process in practical application and meet the application requirements. Conclusions. Hydraulic mechanical calendering may be used to calendar different plastic materials, with a blank thickness of 0.5-3 mm, according to the technology’s operating principle, test production, and foreign data. Thicker sheets may be calendered with adequate hydraulic pressure. For the form of parts, the optimum effect is that the projectile, cone, etc. section vary from small too big. For the section does not change or smaller parts also have an impact? Some pieces with an interior concave shape and bottom and side stiffeners are difficult to the calendar. Hydromechanical calendering technologies make it easier to create these pieces.

The Rollers’ Offset Position Influence on the Counter-Roller Flow-Forming Process

Background: The general counter-roller flow-forming (CRFF) process rarely considers the roller’s offset position for the symmetric rollers. However, the rollers’ offset position can regulate the tube shape, force, and other features. Studying the novel asymmetric CRFF process, which is the CRFF process with the rollers’ offset position, is essential. Methods: The influence of the rollers’ offset position, the tube blank thickness, thickness reduction on the material deformation, flow-forming force, final tube middle radius, and thickness in the CRFF process are studied using AA5052 aluminum tube experiments and numerical simulation. Result: The final tubes with three tube blank thicknesses, four thickness reduction, and four rollers’ offset positions were obtained by the symmetric and asymmetric CRFF processes. Conclusions: AA5052 aluminum alloy tube can be made by the novel asymmetric CRFF process using a small rollers’ offset position (−17.5–0%). Different rollers’ positions could change the tube’s middle radius. With negative rollers’ offset position, the outer roller force is larger than the inner roller force. The force differences increase with the increase of tube blank thickness, the increase of thickness reduction, and the decrease of rollers’ offset position. The asymmetric CRFF process helps design and construct large tube flow-forming equipment.

Effect of Cooling Rates and Intermediate Slab Blank Thickness on the Microstructure and Mechanical Properties of the X70 Pipeline Steel

Effect of Cooling Rates and Intermediate Slab Blank Thickness on the Microstructure and Mechanical Properties of the X70 Pipeline Steel

Formability Experiments for Unidirectional Thermoplastic Composites

Reliable composite forming experiments are required to characterize composite formability, to aid material development, and to validate process simulations models. Due to practical reasons, however, typically a limited amount of forming configurations is studied. The objective of this study is, therefore, to develop a methodology for obtaining controlled forming results in a wide range of configurations. Press forming experiments using a dome geometry were used to explore the formability of two commercial unidirectional thermoplastic composite materials. A variety of forming configurations was employed by changing the blank dimensions and layup. The observation of wrinkling defects was simplified by leaving an additional 3 mm tool gap. Blank width and layup had the most influence on the wrinkling severity, followed by blank thickness and length. Quasi-isotropic layups were found to produce wrinkles in nearly all cases, confirming a difficulty in general to form double curved parts. The size and number of wrinkles in these layups were found to change with the stacking sequence. Cross-ply layups showed better formability, but significant wrinkles were still observed depending on the orientation of the blank relative to the layup. The formability experiments using a dome geometry provided a reliable methodology for controlled forming results in many configurations using a generic toolset. Additionally, a comprehensive comparison of formability for two commercial thermoplastic UD materials in a variety of scenarios was provided.

Non-axisymmetric die-less spinning using ball-crown-shape roller

The non-axisymmetric cone has broad application prospects. However, the severe wall thickness thinning has been the bottleneck problem restricting the application of non-axisymmetric parts which are manufactured via die-less shear spinning. In order to control the spun wall thickness distribution, the ball-crown-shape roller is adopted to carry out the non-axisymmetric spinning. The spun workpiece with the non-axisymmetric cone shape is obtained, and the deviation of the maximum and minimum half cone angles α and β between the experimental results and the theoretical values is no more than 4.11%. The wall thicknesses are much greater than that of the shear spinning value with the corresponding half cone angles, and basically maintain at (even locally exceed) the initial blank thickness. At the same time, the half cone angle is considered to have small effect on the wall thickness distribution. The finite element model for this spinning process is established and verified to reveal the wall thickness distribution mechanism which is illustrated as that the BCSR causes the complementary relationship between the metal outflow and circumferential replenishment in the each half cone angle direction.

Deep Drawing Process Using a Tractrix Die for Manufacturing Liners for a CNG High-Pressure Vessel (Type II)

The liner of a CNG pressure vessel is manufactured by a DDI (deep drawing and ironing) process for the cylinder part, which is a continuous process that includes a drawing process to reduce the diameter of the billet and a subsequent ironing process to reduce the thickness of the billet. A tractrix die used in the 1st deep drawing allows the blank to flow smoothly by decreasing the punch load and radial tensile stress occurring in the workpiece. It also increases the draw ratio compared to conventional dies, but it causes forming defects. In this study, a shape coefficient (Sc) is proposed for the tractrix die using the blank diameter (D0), inflow diameter of the workpiece (di), and inflow angle of the workpiece (theta) for design of the tractrix die. The effects of the thickness and inflow angle of the workpiece on wrinkling and folding were investigated through FEA. Also, a discriminant is proposed for the relative radial stress (tilde{sigma }) generated during the deep drawing process using the tractirx die and used to predict fracture. Based on the results, the blank thickness, the draw ratio, and the inflow of the workpiece angle in the 1st deep drawing process are suggested, and the number of operations in the DDI process was reduced from 6 to 4. This improves the productivity and reduces the manufacturing cost.

An analytical model integrated with toolpath design for wrinkling prediction in conventional spinning

Blank wrinkling is the most frequently encountered material processing failure in spinning. Design of toolpath profiles and selection of process parameters are important in preventing wrinkling. Existing studies employ simplified toolpath profiles and rely on the calculation of maximum and critical stresses of the blank to determine the onset of wrinkling, often requiring time-consuming Finite Element simulations. To overcome these limitations, this paper develops an analytical wrinkling prediction model integrated with toolpath design in developing multi-pass conventional spinning. The toolpath design is parameterised for concave, convex and linear profiles and a wrinkling-wave function using a concave profile is developed to capture geometrical characteristics of a wrinkled blank. The forming depth is introduced as a critical variable in designing a toolpath profile to control wrinkling. Material plastic deformation is analysed by employing the Donnell-Mushtari-Vlasov theory and wrinkling initiation is predicted by the occurrence of the instability of the blank as a doubly-curved thin shell. Experimental tests of first-pass conventional spinning using concave, convex and linear toolpath profiles are performed to validate the developed wrinkling prediction model. The experimental validation confirms that the proposed critical forming depth of toolpath profile is an accurate and effective measure in predicting the onset of wrinkling. The results show the significant effect of the design of toolpath profile, blank thickness, spin ratio and feed ratio on the onset of the wrinkling. The wrinkling prediction model is capable of producing processing maps of these key parameters to prevent wrinkling for the spinning process development in practical applications.