Box-shaped Parts Research Articles

A novel dual-stage failure criterion based on forming limit curve for uncured GLARE

Forming limit curve (FLC) is an essential criterion for evaluating the formability of fiber metal laminates (FMLs) in mass fabrication. However, conventional methodologies are unable to predict inner fiber failure, very sensitive to wrinkling defects, resulting in low measurement accuracy and stability. Hence, a novel dual-stage failure criterion considering the progressive failure of fiber and metal layers has been developed and validated by utilizing a notch-pattern sample and forming of typical thin-walled structure, with four typical categories of glass laminate aluminum reinforced epoxy (GLARE). The Nakajima tests of a series of notch-pattern and conventional pattern specimens with different widths were conducted in this study, demonstrating the superiority of wrinkling and delamination prevention of the notch-pattern by enhancing 22.84 % stress triaxiality and reducing 39.51 % compress strain in the edge area. Notably, punch reaction force and strain field analyses unveiled a mutation phenomenon indicative of premature fiber failure while the aluminum remained intact, which was also verified by numerical and interrupted methods. Furthermore, the acoustic emission in-situ method was adopted to monitor the progressive damage evolution of uncured GLARE in the Nakajima test, providing solid support for the occurrence of fiber failure at the mutation site. Leveraging these mutations, a list of dual-stage forming limit curves was devised to quantify the progressive damage behavior of uncured GLARE under biaxial tensile conditions. Finally, the practical application of this novel dual-stage forming limit curve methodology was demonstrated in the manufacturing process of a box-shaped part, serving as a proof of concept for its effectiveness. This study offers a foundational guideline for characterizing the intrinsic failure mechanisms of fiber metal laminates, particularly internal fiber failure under various strain conditions, thereby enhancing predictive accuracy.

Failure analysis and formability improvement of GLARE laminates in warm active hydroforming technology: Experimental and numerical approach

Warm hydroforming shows considerable promise as a forming technology for Fiber Metal Laminates (FMLs) parts due to its capacity to enhance the formability of materials. However, a detailed investigation into the failure behavior during hydroforming is still lacking. In this paper, a systematic experiment was performed to analyze the possible failure modes for GLARE in warm active hydroforming. Five main defect modes have been identified, including fiber crack, combined Al & fiber crack, wrinkle, low resin, and voids defects. The related formation mechanisms have been analyzed based on both experiments and numerical methods. Additionally, the effects of critical process parameters, including the blank holder force (BHF), liquid pressure rate (PR), and temperature (T) on failure behavior are thoroughly investigated and quantified. The use of step-loading BHF was recommended to enhance formability, which caused a nearly 36% decrease in the prepreg tensile damage criteria coefficient. Conversely, decreasing PR or increasing T significantly improved the formability of GLARE but resulted in low resin content and significant void defects. Consequently, a feasibility map that quantified the BHF and liquid pressure effects on various defects was developed, leading to optimized parameters for manufacturing a box-shaped part. This study not only explores the failure model of FMLs but also offers valuable insights for process parameter improvement and how to optimize key parameters in engineering processes.

Finite Element Simulation and Microstructural Evolution Investigation in Hot Stamping Process of Ti6Al4V Alloy Sheets.

Titanium alloy hot stamping technology has a wide range of application prospects in the field of titanium alloy part processing due to its high production efficiency and low manufacturing cost. However, the challenges of forming titanium alloy parts with large depths and deformations have restricted its development. In this study, the hot stamping process of a Ti6Al4V alloy box-shaped part was investigated using ABAQUS 2020 software. The thermodynamic properties of a Ti6Al4V alloy sheet were explored at different temperatures (400 °C, 500 °C, 600 °C, 700 °C, 800 °C) and different strain rates (0.1 s-1, 0.05 s-1, 0.01 s-1). In addition, the influence law of hot stamping process parameters on the minimum thickness of the formed part was revealed through the analysis of response surface methodology (RSM), ultimately obtaining the optimal combination of process parameters for Ti6Al4V alloy hot stamping. The experimental results of the hot stamping process exhibited a favorable correlation with the simulated outcomes, confirming the accuracy of the numerical simulation. The study on the microstructure evolution of the formed parts showed that grain refinement strengthening occurred in the part with large deformation, and the formed box-shaped parts exhibited a uniform and fine microstructure overall, demonstrating high forming quality. The achievements of the work provide important guidance for the fabrication of titanium alloy parts with large depths and deformations used in heavy industrial production.

A novel active hydroforming & curing process to manufacture GLARE laminates: Numerical and experimental investigations

Fiber Metal Laminates (FMLs) are preferable thin-walled structures in several fields for their exceptional mechanical properties. However, how to manufacture thin-walled FMLs structures with complex shapes and guarantee the high mechanical properties is still a challenge. To address these, this paper proposes an innovative hybrid forming method, referred to as active warm hydroforming and curing, to enhance the formability and performance of FMLs in GLARE form by combining the forming and curing process into a single step. The hybrid method was verified on a box-shaped part as a proof-of-concept to assess the feasibility and parameter influence. Online curing was utilized to enhance efficiency and quality. The outcomes revealed that the new method increases the ultimate tensile stress by 12.1 % and reduces curing deformation from 3.1 mm to 1.3 mm compared to the vacuum bagging method. Furthermore, the critical parameters in forming of thin-walled structures, including blank holder force (BHF), pressure rate (PR), maximum pressure (MP), and forming temperature (FT), were identified using experimental, mathematical, and numerical approaches. Four defects in the formed thin-walled structures were observed and successfully eliminated through the control of these parameters. The method and results presented in this paper also provide direct guidance for optimizing the process parameters of FMLs warm hydroforming.

A method combining optimization algorithm and inverse-deformation design for improving the injection quality of box-shaped parts

A method combining optimization algorithm and inverse-deformation design for improving the injection quality of box-shaped parts

The Influence of Springing of High-Strength Steel DP780 on the Limiting Possibilities of its Forming during Electro-Hydraulic Stamping

Using the example of stamping a box-shaped part from high-strength sheet steel by a pulsed electro-hydraulic method, the limiting possibilities of its shaping, taking into account the springing of the material, are studied. The influence of the radius of the curvature and the shape of the surface of the corners of the part on the change in the structure of high-strength steel DP780 and the appearance of defects in it is determined. Relations between the radius of the curvature of the surface of the part and the thickness of the workpiece are obtained, at which there are no defects in the structure of DP780 steel and the limiting possibilities of its deformation are achieved with minimal springing of the material.

316L Stainless Steel Thin-Walled Parts Hybrid-Layered Manufacturing Process Study.

Additive manufacturing technology overcomes the limitations imposed by traditional manufacturing techniques, such as fixtures, tools, and molds, thereby enabling a high degree of design freedom for parts and attracting significant attention. Combined with subtractive manufacturing technology, additive and subtractive hybrid manufacturing (ASHM) has the potential to enhance surface quality and machining accuracy. This paper proposes a method for simulating the additive and subtractive manufacturing process, enabling accurate deformation prediction during processing. The relationship between stress distribution and thermal stress deformation of thin-walled 316L stainless steel parts prepared by Laser Metal Deposition (LMD) was investigated using linear scanning with a laser displacement sensor and finite element simulation. The changes in stress and deformation of these thin-walled parts after milling were also examined. Firstly, 316L stainless steel box-shaped thin-walled parts were fabricated using additive manufacturing, and the profile information was measured using a Micro Laser Displacement Sensor. Then, finite element software was employed to simulate the stress and deformation of the box-shaped thin-walled part during the additive manufacturing process. The experiments mentioned were conducted to validate the finite element model. Finally, based on the simulation of the box-shaped part, a simulation prediction was made for the box-shaped thin-walled parts produced by two-stage additive and subtractive manufacturing. The results show that the deformation tendency of outward twisting and expanding occurs in the additive process to the box-shaped thin-walled part, and the deformation increases gradually with the increase of the height. Meanwhile, the milling process is significant for improving the surface quality and dimensional accuracy of the additive parts. The research process and results of the thesis have laid the foundation for further research on the influence of subtractive process parameters on the surface quality of 316L stainless steel additive parts and subsequent additive and subtractive hybrid manufacturing of complex parts.

Defects, microstructures and mechanical properties of a box-shaped Ti–6Al–4V alloy part fabricated by laser powder bed fusion

A box-shaped Ti–6Al–4V alloy part was fabricated by laser powder bed fusion (LPBF) with a gas-atomized powder and annealed at 800 °C for 2 h. The defects, microstructures and mechanical properties of the part at different distances from the substrate and in different directions were studied. It was found that the part contained blowhole defects and exhibited a columnar macrostructure of prior β grains with a microstructure mixed by α variant colony and basketweave microstructure. The prior β grains and α lamellae near the substrate were coarser due to preheating impeding heat transfer and they were slightly finer in the last solidified layers and the heat-affected zone due to incomplete in-situ heat treatment, and this rendered the latter to have better ductility than the former (elongation to fracture 11.1% vs. 8.1%) without changing the strength (yield strength: 961 MPa, ultimate tensile strength: 1042 MPa). The box-shaped part exhibited anisotropy of mechanical properties due to the columnar macrostructure and the α phase preferred orientation that activates a higher proportion of prismatic <a> slips.

Аналіз науково-технічних інновацій в галузі машинобудування з виявленням закономірності впливу технологічних параметрів

Based on the analysis of scientific and technical information, it established that today layered metals are one of the most modern and promising materials used in all branches of mechanical engineering and national economy. The use of bimetals allows you to achieve significant cost savings, obtain materials with unique properties, increase production efficiency and competitiveness of a wide class of parts and equipment. The purpose of the article is to analyze the methods of determining the stress state of a workpiece with heterogeneous mechanical characteristics in the process of plastic deformation and to determine the stress-strain state when drawing rectangular parts from bimetals. As a result, of unequal deformation conditions in different parts of the contour, as well as anisotropy of the mechanical properties of the workpiece material, the height of box-shaped parts is even more uneven than the height of axisymmetric parts obtained by drawing. Therefore, in the manufacturing process of such parts, cutting of the uneven edge provided. The trimming allowance depends on the relative height of the part. The bigger it is, the bigger the allowance. Since the flange naturally thickens during drawing in the corner sections of the part contour, this phenomenon taken into account when determining the gap between the punch and the die of the drawing die: in the corner sections, the gap should be greater than in the straight sections of the die contour. Extrusion of box-shaped parts from bimetals causes even greater unevenness of deformations. A different amount of deformation of the layers of the bimetallic work piece imposed on the general sign change of the voltages, which causes bending and warping of the rectilinear parts of the semi-finished product, and therefore, the impossibility of obtaining a high-quality product. Based on the analysis of the stress-strain state of the workpiece in the process of drawing bimetal. The following provisions are proposed: if the mechanical properties of the metal layers do not differ - the two-layer metal behaves like a single-layer, then the ratio of the thicknesses of the two-layer metal does not change after drawing; if the mechanical properties of the layers differ, then the ratio of the thicknesses of the two-layer metal changes after drawing. Thus, when the ratio σs1/σs2 decreases, the thickness of the first layer, which has lower mechanical properties, decreases at the output; the thickness ratio after drawing also depends on the initial ratio of metal thicknesses. Based on the analysis of the stress-strain state of the work piece during the extraction of box parts, the following methods and techniques have been determined for obtaining high-quality parts by extraction and saving material: use metals with similar mechanical properties; the desire to increase the curvature of the corner zones of the work piece; to calculate the dimensions of the work piece for the hood with the involvement of modern mathematical apparatus (potential method); use brake media instead of brake ribs; affect the center of deformation, increasing the effect of unloading tangential stresses.

Theoretical Investigation of Forming Process of Aluminum Alloy Rail Vehicle Side Window

With the vigorous development of rail transit trains around the world and the emergence of global environmental pollution and energy shortages, the world has an urgent need for manufacturing technology for lightweight aluminum alloy rail transit train components. This paper mainly studied the superplastic forming law of 5083Al for rail transit. Through the high-temperature tensile test and blowing forming experiments, the superplastic properties of 5083Al were determined. Based on this, the die design, finite element simulation, and forming experiment of the rail vehicle side window were carried out. In order to study the superplastic deformation behavior of industrial 5083Al under complex stress conditions, the influence of the depth, area ratio, and friction coefficient of the pre-forming die on the part thickness distribution is simulated. The side window is made of a high-strength 5083Al sheet in the form of bending at both ends to ensure the strength of the connection between the overall side window and the side wall skeleton. The variation law of the side wall forming height of 5083Al box-shaped parts was studied. The efficient manufacture of parts that meet quality standards was made possible by the optimization of the pressure profile. The microstructure changes of the material after superplastic forming were studied by Energy Dispersive Spectrometer (EDS) and Electron Backscattered Diffraction (EBSD).

Prediction and Experimental Verification of the Critical Fracture Blank Holder Force for Deep Drawing of Box-Shaped Parts

Prediction and Experimental Verification of the Critical Fracture Blank Holder Force for Deep Drawing of Box-Shaped Parts

Correction of mould cavity geometry for warpage compensation

Warpage is one of the most challenging defects occurring in plastic injection moulded parts. Various approaches to overcome this issue have been proposed in the literature, but they all provide only partial solutions to the problem. This paper proposes a new method for the compensation and minimisation of warpage. The method is based on Mould Cavity (MC) correction. In contrast to other similar methods, here the MC correction is accomplished through a direct comparison of the local deviations of the warped part’s geometry to the desired geometry of the part. Modifying the MC shape accordingly yields parts with a lower shape discrepancy from the desired geometry compared to the nonadjusted shape. The key novelty of the paper is the development of software that iteratively adjusts the MC shape to minimise local deviations. In every iteration, the warped part is compared to the desired geometry in order to compute local deviations between both geometries. Computation is done first by determining the point normal vector of the warped geometry mesh and its piercing point through desired geometry mesh. Second, distance between the base point and the piercing point is calculated. After all local deviations are determined, the MC geometry is adjusted accordingly. Two case studies demonstrate the method’s capabilities. In the first case we present a curved thin-walled plate part. The maximum warpage value of 0.005 mm (0.7% of the initial maximum warpage) was reached after three iterations of MC geometry correction and remained stable afterwards. In the second case the method was tested on the box-shaped part. The maximum warpage dropped from initial 0.711 mm to 0.066 mm after three iterations.

Research on the zoned lubrication process based on forced lubrication technology during box-shaped part deep drawing

Research on the zoned lubrication process based on forced lubrication technology during box-shaped part deep drawing

Machine learning in the prediction of formability in aluminum hot stamping process with multiple variable blank holder force

ABSTRACT Multiple blank holders with variable blank holder forces is a promising method to effectively improve the formability of aluminum alloy for the hot stamping process. However, it introduces much more variables of holder forces in the process. The conventional simulation- or experiment-based methods cannot effectively analyze and optimize the hot stamping process. This paper provides a new way to solve this problem by utilizing the advantages of machine learning techniques. Finite element models (FEM) of hot stamping of a box-shaped part considering eight separate blank holders with varying forces were established first. Based on the model, 1000 sets of process parameters and corresponding hot stamping results were generated randomly to provide enough data. A machine learning model was then established to predict the maximum and minimum thickness of the stamped parts. Fourth, a convolutional neural network was established to predict the thickness variation distribution. The results showed that a series of optimal multiple variable blank holder forces were obtained to improve formability, and the machine learning models could accurately predict the thickness distribution. This technique provides an efficient tool in applying multiple blank holders with variable blank holder forces in the hot stamping process.

Mechanical Analysis of Deformation Law in the Flange Area of Box-Shaped Parts during Deep Drawing

The investigation of deformation law is the theoretical basis for analyzing instability wrinkling and forming performance during the sheet-metal-forming process. In order to explore the deformation law in the flange area of box-shaped parts and conduct qualitative and quantitative analysis on stress and strain, it is assumed that the deformation law of the mass point on the zero line of shear stress in the corner area is equal to that of the axisymmetric parts. Based on the basic assumptions that the equivalent strain in the flange area is linear with the radius along the radial direction, the simple linear relationship between in-plane shear stress and geometric parameters and the expressions of stress and strain in each region of the flange area are derived. The theoretical derivation is compared and analyzed through finite element (FE) simulation and process tests. The results demonstrate that the theoretical calculation results are consistent with the trends of experimental and simulation results. The calculation accuracy of equivalent strain is higher than that of stress calculation, which reveals that calculation accuracy is sensitive to the parameters in the material constitutive model. The theoretical analysis has reference significance for exploring the law of deep drawing deformation, optimizing the forming process and guiding the actual production.

Conventional and Microcellular Injection Molding of a Highly Filled Polycarbonate Composite with Glass Fibers and Carbon Black.

Conventional solid injection molding (CIM) and microcellular injection molding (MIM) of a highly filled polycarbonate (PC) composite with glass fibers and carbon black were performed for molding ASTM tensile test bars and a box-shape part with variable wall thickness. A scanning electron microscope (SEM) was used to examine the microstructure at the fractured surface of the tensile test bar samples. The fine and uniform cellular structure suggests that the PC composite is a suitable material for foaming applications. Standard tensile tests showed that, while the ultimate strength and elongation at break were lower for the foamed test bars at 4.0–11.4% weight reduction, their specific Young’s modulus was comparable to that of their solid counterparts. A melt flow and transition model was proposed to explain the unique, irregular “tiger-stripes” exhibited on the surface of solid test bars. Increasing the supercritical fluid (SCF) dosage and weight reduction of foamed samples resulted in swirl marks on the part surface, making the tiger-stripes less noticeable. Finally, it was found that an injection pressure reduction of 25.8% could be achieved with MIM for molding a complex box-shaped part in a consistent and reliable fashion.

Research on the Mechanism of Multi-pass Ironing Drawing Process of High Box-shaped Parts and Establishment of Numerical Simulation Model

Research on the Mechanism of Multi-pass Ironing Drawing Process of High Box-shaped Parts and Establishment of Numerical Simulation Model

Increasing the accuracy of processing thin-walled box-shaped parts

The paper describes the development of a procedure for increasing the accuracy of processing thin-walled parts. The paper proposes a new method for fixing and processing thin-walled box-shaped parts, during which the coordinate of the workpiece base side position is measured using an RMP40 sensor before and after the application of clamping forces, followed by compensation for processing on a CNC milling machine. A special control program that takes into account elastic deformations has been developed. A comparative analysis of dimensions performance showed that the accuracy of coordinate dimensions performance taking into account the compensation of elastic deformations is higher than without compensation.

Experimental study of the error in the height of the contour of box-shaped parts, obtained by drawing from welded blanks of different thickness

The development of sheet-stamping production within the framework of meeting the needs of modern mechanical engineering involves the use of advanced technologies, materials and blanks, which makes certain requirements for the level of blank production technologies in general. In modern conditions, sheet-stamping production involves the manufacture of stamped parts in limited quantities due to their constantly changing design, which, in turn, requires optimization of the volume of investments and reduction of the time required for the implementation of technological preparation of production, flexibility of technological and design solutions, as well as the maximum approximation of all parameters of stamped parts to parameters of the finished product in order to reduce subsequent processing. Box-shaped sheet metal stamped parts obtained during the implementation of the drawing operation are actively used in the medical, light, watchmaking, food machine-building, electrical, instrument-making, and automotive industries. One of the main tasks for obtaining high-quality box-shaped sheet-stamped parts is the creation of a stamping technology that meets modern production requirements based on progressive methods for calculating shaping operations, as well as designing the contour of the original blank taking into account the peculiarities of the shaping process and the required geometric parameters of parts. Depending on the purpose of the box-shaped sheet-stamped part, the main geometric parameters are determined, the correspondence of the actual values of which to the required ones allows to make a conclusion regarding the quality of the obtained stamped product. As a rule, such a parameter is the height of the box-shaped part, the error of which ultimately should not exceed the tolerance assigned by the designer. For example, in the automotive industry, one of the promising directions for reducing the weight of a car while maintaining the strength parameters of its units and elements, as well as reducing their cost, is the introduction of sheet welded blanks of different thickness. This article is devoted to an experimental study of the error in the height of the contour of tall boxes with relatively large radii of corner curvatures, obtained by drawing from these blanks made of high-strength steel. This work was carried out within the framework of the grant NSh-2601.2020.8.

Finite Element Study on Pattern of Pins Supporting an Elastic Blankholder Used for Stamping Irregular Shaped Sheet Metal Parts

Working with individual in-process controllable elements to support an elastic blankholder is the state-of-the-art for stamping irregular shaped sheet metal parts without wrinkles and cracks. It is thus needed to carefully determine the position for each expensive device. This study is therefore aimed to appraise a feasible approach with finite element analysis, in that the blankholder is first modelled as a rigid object instead of an elastic one to evaluate the contact pressure of the blankholder to the blank during the forming process. The sites showing a locally relative high contact pressure, which are usually induced by local thickening of material, can be regarded as the locations of the supporting elements to intently form a local high pressure to control the material flow and thus to eliminate the local thickening there. As a result, since the blankholder force can be efficiently delivered from the supporting elements directly to the blankholder as well as to the blank, it is not only applied to the rectangular box-shaped part but also to a fender-like irregular sheet metal part. Furthermore, the initiated contact pressure can be maintained at locations during the whole stamping process. This is also experimentally validated by stamping a sound fender-like irregular sheet metal part with an elastic blankholder supported by elements located accordingly at those sites suggested by this study.