Blank Shape Research Articles

Automatic Optimization of Initial Blank Shape in Production of All Kinds of Rectangular Parts in Computer Aided Hydroforming Process

Automatic Optimization of Initial Blank Shape in Production of All Kinds of Rectangular Parts in Computer Aided Hydroforming Process

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.

Zirconia CAD/CAM machining vibrations related to zirconia blank shape and initial digital nesting.

To evaluate CAD/CAM milling vibrations related to zirconia disk design, framework, and location of digital crown nesting during zirconia soft milling. In the present in vitro study, 25 round zirconia disks of 98 mm (R group) and 15 D-shaped zirconia disks of 71 mm (D group) were placed in a 5-axis CAD/CAM milling unit. The R group had 3 crown milling sites (n = 75) and the D group had 2 crown milling sites (n = 30). In the R group, site A was located 57 mm, site B was 92 mm, and site C was 123 mm from the machine holder attachment. In the D group, site A was 57 mm and site C was 123 mm from the machine holder attachment. A vibration meter (VB-8200; Lutron) was connected to the disk holder, and data (mm/second) were collected during the milling process at the different nesting locations. One-way ANOVA with post-hoc tests and Bonferroni correction for multiple tests were used to compare the groups (α = 0.05). In the R group, site C exhibited the highest mean vibration values compared with site A (P = 0.001). The first and second cutting tools (2.5 and 1 mm) exhibited statistically significant differences between the D and R groups at milling sites A and C (P < 0.001 and P = 0.003, respectively). Milling vibration increased as the distance between the machine holder arm and a digitally nested site increased. Round zirconia disks induced higher vibration values compared with D-shaped disks.

Numerical optimization of the blank shape in order to minimize the earring defect in the deep drawing process of square sections

Numerical optimization of the blank shape in order to minimize the earring defect in the deep drawing process of square sections

Investigation of the Accuracy of the Height Dimensions of Forgings for Cold Volumetric Stamping Processes by the Computational and Analytical Method

In mechanical engineering, product quality indicators are inextricably linked with the accuracy of machining parts. The dimensions, shape and location of the surfaces obtained during processing determine the actual gaps and tightnesses in the joints of machine parts, and consequently, the technical parameters that affect the quality, reliability and economic performance of production and operation. Very often in practice, the achievable accuracy of processing, including cold volumetric stamping (HOS), is judged by the accuracy tables contained in special reference literature. Such tables contain indicative data on achievable accuracy for various technological operations, obtained by systematization of direct long-term observations in production conditions. However, the peculiarities of individual operations do not allow us to give a conclusion about the accuracy of stamping by analogy with other operations, since there is no comprehensive similarity between them. In particular, the sizes and shape of the initial blanks differ, mechanical the properties of their material, the friction conditions in the die cavity, the characteristics of the press used and other technological factors. Thus, taking into account the listed circumstances, in each specific case it is necessary to calculate the accuracy of processing, which should have the ultimate goal not only to obtain a numerical result, but first of all to disclose the mechanisms of accuracy control. The calculation of the processing accuracy should be carried out taking into account the methods of obtaining dimensions and methods of setting up the technological system. The article is devoted to the computational and analytical method for calculating the forging accuracy based on the application of the theory of parametric sensitivity.

Process-based surface flattening method for laser peen forming of complex geometry

Laser peen forming (LPF) is a novel flexible forming process with several advantages, such as noncontact and high controllability, but it lacks a method to obtain the initial blank geometry based on its specific deformation behavior, limiting the application of the process. This study proposes a process-based surface flattening method to determine an optimal initial blank of complex geometry to accommodate the precise forming requirement. The process-based surface flattening method is developed based on the deformation behaviors of the laser-peened (LPed) and non-LPed zones with equal-strain and equal-area criteria, respectively. The objective surface is first flattened with the equal-area criterion, then the in-plane strain in LPed zones is loaded into the equal-area flattened blank. Because the in-plane strain is unknown before flattening, an optimization model is conceived to solve the in-plane strain in LPed zones based on the proposed equal-strain flattening method. Experiments are designed to validate the surface flattening methods regarding the LP-formed saddle surface as the objective with a known initial blank. The flattening blanks are quantitatively compared with the initial blank. The process-based flattening method presents the blank geometry with a mean absolute error (MAE) of 0.027 mm, while the geometry-based flattening method presents the result with a MAE of 0.398 mm, illustrating the process-based method can provide a more effective initial blank shape.

Microstructure evolution and deformation mechanism of AZ80 alloy during die forging

Die forging is a processing method that can produce a size and shape close to the finished product and improve the mechanical properties of the alloy. In this paper, Mg–8Al-0.5Zn magnesium alloy was used to prepare stepped shaft by isothermal die forging. The microstructure and stress-strain state of different parts of stepped shaft forging were analyzed. The metal rheological law and microstructure evolution mechanism of AZ80 alloy during die forging were discussed. At the position of low stress and high strain state of the die forging, continuous dynamic recrystallization (CDRX) is the main deformation mechanism, and the microstructure is mainly composed of coarse un-dynamic recrystallized (unDRXed) grains and fine equiaxed dynamic recrystallized (DRXed) grains. The unDRXed grains have a strong basal texture, while the DRXed grains exhibit random orientations. At the position of high stress and low strain state of the die forging, {10–12} twinning is the main deformation mechanism, the parent grains show a strong basal texture, while {10–12} twins present [-12-10]-[01–10] double fiber texture parallel to forging direction (FD). The compressive strength and yield strength of the part in the low stress and high strain state are higher than those in the high stress and low strain state, but the fracture strain of the former is lower than that of the latter. The results of this study can provide a reference for the design of die forging die together with the blank shape and size, so as to meet the corresponding performance requirements of different parts of the die forging.

The Variation of Surface Shape in the Gas Jet Forming

This study investigated the the gas jet forming process for optical aspherical mirror blanks. The trend of the influence of the gas jet parameters on the surface shape of the mirror blanks was inferred by analysing the variation in the morphology of the gas jet stream. Based on the theoretical analysis, the inference was verified by numerical simulation. The experimental results were compared with the simulation predictions, and it was found that the average prediction deviation for the diameter was 1.07 mm, while the average prediction deviation for the principal curvature was 0.03665 mm−1, which is challenging to correct in simulation. Therefore, we developed a dimensionless prediction model of the surface curvature and surface diameter of the mirror blanks by considering the jet parameters using experimental data. The model’s average prediction error for the surface diameter of the formed surface was 0.3192 mm, and the average prediction error of the principal curvature for the formed surface was 0.00269 mm−1.

Isogeometric algorithm for one-step inverse forming of sheet metal

The isogeometric one-step inverse forming method aims to predict the shape of blanks and the formability of stamping parts using accurate geometry without meshing. In this paper, the discrete surface Ricci flow algorithm in computational conformal geometry is introduced as an unfolding algorithm for one-step inverse forming of isogeometric membrane elements. A combination of discrete surface Ricci flow algorithm and elastic iteration is proposed to predict the initial solution. It is proved applicable, even for the extremely curled parts which have negative angles and vertical walls. In addition, we propose a method that the external force of the punch is equivalent to the control point by means of Greville abscissae. A nonlinear equation system is established based on the principle of minimum potential energy. The Newton–Raphson iteration is used to calculate the blank shape and the thickness distribution of the stamping parts. The examples of square box, flower box, and L shape prove that the algorithm can predict the contour of the initial configuration and the formability of sheet metal stamping.

Blank shape optimization in sheet metal processing using a hybrid fuzzy-sensitivity method

ABSTRACT In this paper, the blank shape is optimized by three approaches: a slow and accurate method, sensitivity analysis, a fast and approximate method, fuzzy logic decision-making, and finally, a novel quick and precise way was introduced by a combination of sensitivity analysis and fuzzy logic. It is shown that by using hybrid fuzzy logic-sensitivity, the number of iterations has been reduced down to 1 iteration in both cylindrical and square punch forming when the allowable geometrical error was considered to be less than the 1% of target size. The fuzzy logic code was written in Matlab software, and commercial finite element code Abaqus was used to simulate the forming process. Also, the results of the simulations obtained from finite element method analysis were verified experimentally on AL1050-O sheet for two different cylindrical and square die configurations. There was close agreement between the results of simulations and experiments. The difference was within the acceptable range of almost 3.5% in the square die and 1.8% in the cylindrical die.

INCREASING THE ROBUSTNESS OF AN INVERSE STAMPING ALGORITHM

Inverse stamping is a useful tool in engineering. It can be used to find the initial blank shape of stamped parts. It is also useful for quick and easy analysis of a forming process and its impact on the design of a component. Algorithms for inverse stamping are commonly available, but in some situations these algorithms can collapse or may provide confusing results. This article describes improvements to a newly designed inverse stamping algorithm which lead to an increase in its robustness.

Bringing shape into focus: Assessing differences between blades and bladelets and their technological significance in 3D form

Laminar technologies were adopted by Paleolithic foragers to produce a variable range of stone implements. Archaeologists have reconstructed the different reduction procedures involved in the production of laminar stone tools, often underlying a separation between the bigger blanks (i.e., blades) and smaller bladelets. However, these two blank types are in most cases poorly defined, as their classification typically relies on arbitrary size thresholds that do not consider blank shape, which is a fundamental component of tool production and function. In this study, we investigate whether traditional classifications of blades and bladelets are morphologically and technologically meaningful. For this purpose, we employ a three-dimensional geometric morphometric approach on a large sample of complete blanks retrieved from one of the earliest laminar industries assigned to modern humans in southern Europe: the Protoaurignacian from Fumane Cave. We rely on a cutting-edge protocol for acquiring virtual 3D meshes of stone tools using micro-computed tomography. This novel approach allows us to scan large quantities of small lithics in a short period of time and without the typical technical problems associated with scanning small objects. After calculating the principal components of shape variation, we explore differences and similarities across the dataset using linear discriminant analysis and analysis of variance. Our multivariate study highlights distinct morphological tendencies across blades and bladelets that are however better framed when the technological organization of Protoaurignacian stone knapping is taken into consideration. Overall, our results demonstrate that virtual analysis of stone tool shape can help elucidate aspects of lithic technology and its implications for past human behavior.

Optimization of process parameters for rectangular cup deep drawing by the Taguchi method and genetic algorithm

Abstract This article presents the optimization of process parameters in reducing the risk of failure due to wrinkling and fracture in deep drawing of a rectangular cup. Blank holder force, friction coefficient, punch radius and initial blank shape were chosen as design parameters. Wrinkling and fracture criteria were used as objective functions. Two-stage optimization approach was used. In the first stage optimization, optimum blank shape was determined using the Taguchi optimization method. In the second stage optimization, optimum parameter values were determined for the selected blank shape by the first stage optimization using genetic algorithm. In the second stage of optimization, response surface models based on 3-level full factorial design of experiments were constructed. Finite element simulation results were used for creating response surface models. Parameters obtained from optimization study were confirmed by conducting deep drawing simulations using commercial code DYNAFORM 5.9.2. Optimum results showed that proposed optimization methodology can solve wrinkling and fracture problems in the sheet metal forming process.

A Novel Method for Friction Coefficient Calculation in Metal Sheet Forming of Axis-Symmetric Deep Drawing Parts

Friction is one of the important factors in sheet metal forming. It greatly affects dynamic behaviors of metal sheets and stress and strain distributions in the metal sheets. In this study, deformation characteristics, stress–strain distribution, and change law of symmetrical parts in the process of deep drawing are analyzed using a new theoretical model based on the plastic flow law and partitioning the forming area. In the model, the least-square method is used to linearize the friction coefficient in nonlinear problems and reverse the calculation of friction coefficients to interpret the friction coefficient. To evaluate the model, the friction coefficient in sheet metal drawing of axis-symmetric deep drawing parts under various friction conditions was measured using a self-developed measuring system. The comparison between the experimental results and the calculation using the model shows a good agreement. The results show that the drawing force increases with the increase in punch depth; the friction coefficient decreases with the rise in punch depth. The friction coefficient obtained by fitting is relatively stable, and the average error is less than 3%. Using the friction coefficient model in finite element simulation analysis, it shows that the thickness and blank shape errors are less than 5%. The novel method studied in this paper shows great significance in support for theoretical research, numerical simulation research, and sheet metal stamping performance evaluation.

Feasibility of one-shot forming for manufacturing of steel/CFRP hybrid B-pillar

ABSTRACT In this study, the feasibility of one-shot forming for manufacturing of steel/CFRP hybrid B-pillar was investigated using a steel sheet with a CFRP patch. The design of one-shot forming process has been described in three stages. First, CFRP reinforcement was designed to substitute for the steel reinforcements for weight reduction. The thickness of CFRP reinforcement was determined through structural analysis by comparing the strengths of the conventional and hybrid B-pillars. Second, the stamping of B-pillars using only the steel sheet was preliminarily designed to determine a proper blank shape that could be used as an initial blank shape in one-shot forming. Third, one-shot forming of the steel/CFRP hybrid B-pillar was designed by finite element (FE) simulation to investigate if fracture and wrinkling occur during the forming process. The feasibility of the designed one-shot forming was evaluated by experimentally manufacturing a steel/CFRP hybrid B-pillar. The FE simulation and experimental analysis indicated that one-shot forming is efficient and suitable for manufacturing steel/CFRP hybrid structures and can be used for mass production of automotive parts at low cost without an additional assembly process.

Effect of blank shape during hot stamping of gas turbine engine blades on structural inhomogeneity

The issues of manufacturing of blanks for hot stamping of gas turbine engine blades are considered. The analysis of the applied shapes of blanks and its stamping on hot stamping crank presses and screw presses is carried out. Various shapes of blanks is simulated based on the results of the analysis.

Optimum blank shape design in deep drawing process using a new boundary updating formula

Optimum blank shape design in deep drawing process using a new boundary updating formula

Design optimization and application of hot-stamped B pillar with local patchwork blanks

The demand for new structural concept design of automotive parts has grown with weight reduction and improvement of crash safety in automotive industry. In this study, the established local patchwork hot stamping technology was used in structural design of hot-stamped automotive parts and expected to obtain maximum lightweight efficiency while maintaining crash performance by using local patchwork blanks instead of conventional reinforcement. Firstly, the technical feasibility of this technology was verified in an experimental method, and an optimization method was proposed to determine the optimal position and shape of local patchwork blanks. Then it was used for the improvements of two parts as examples, a top-hat channel created based on a conventional B pillar cross section and a B pillar. Finite element (FE) analysis models of these two parts were established based on the deformation of B pillar during full vehicle side impact and validated through experiments. It was confirmed that both the top-hat channel and the B pillar optimized have the same crashworthiness but became lighter compared to the original parts with reinforcement. Furthermore, the effects of local patchwork blank thickness, material strength and outer thickness on the optimal position and shape of local patchwork blanks and lightweight efficiency were investigated. Finally, the effectiveness of a hot-stamped B pillar with local patchwork blanks was verified through full vehicle side impact simulations. It can be concluded that the established local patchwork hot stamping technology and the proposed optimization method can be used as a dependable tool to design and manufacture hot-stamped parts with local patchwork blanks.

Optimization and Mapping of the Deep Drawing Force Considering Friction Combination

Deep drawing is characterized by extremely complex deformation that is influenced by process characteristics such as die and punch shapes, blank shape, blank holding force, material properties, and lubrication. The optimization of the deep drawing process is a challenging issue due to the complicated functions that define and relate the process parameters. However, the optimization is essential to enhance the productivity and the product cost in the deep drawing process. In this paper, a MATLAB toolbox (Pattern Search) was employed to minimize the maximum deep drawing force (Fd-min) at different values of the operating and the geometrical parameters. As a result, a minimum deep drawing force chart (carpet plot) was generated to show the best combination of friction coefficients at the blank contact interfaces. The extracted friction coefficients guided the selection of proper lubricants while minimizing the deep drawing force. A finite element analysis (FEA) was applied through 3D model to simulate the deep drawing process. The material modeling was implemented utilizing the ABAQUS/EXPLICIT program with plastic anisotropy. The optimization results showed that the deep drawing force and the wrinkling decrease when compared with experimental and numerical results from the literature.

Shaping the Lyric: Literal and Metaphorical Blank Space in the Poetry of Emily Berry and Ocean Vuong

This article examines two poetry collections that evoke the theme of parental loss: Stranger, Baby by Emily Berry, and Night Sky with Exit Wounds by Ocean Vuong, both published in 2017. It will focus on the poets’ use of blank space, both literally and metaphorically, to emphasise their underlying themes of loss, absence, distance and detachment. However, an analysis of their poems will reveal that their subject is not that of loss but the impossibility of articulating such loss through language. The concept of blank space shapes these poems both physically and figuratively, as Vuong and Berry write into the void that exists between experience and its articulation, foregrounding the void itself through the process of writing. While Berry’s poetry centres on the language of personal grief, Vuong’s collection negotiates other types of loss: a sense of lost heritage, and the silence that results from the erasure of multiple voices.