Metal-forming Processes Research Articles

The Use of Non-Edible Green Oils to Lubricate DC04 Steel Sheets in Sheet Metal Forming Process

Lubrication is a basic and relatively effective way to reduce friction in sheet metal forming operations. The drive to eliminate synthetic and mineral oils, which are difficult to recycle, from the manufacturing process has opened up opportunities for the use of vegetable-based bio-lubricants. This article presents a comparison of the lubrication performance of two non-edible oils (karanja and moringa) with the most frequently tested edible oils (sunflower and rape-seed). Deep drawing quality low-carbon steel sheets DC04, commonly used in the automotive industry, were used as the test material. Friction tests were carried out under various lubricants and normal pressures in the range between 3 and 12 MPa using the strip drawing test. Furthermore, a study was also made of the effect of a change in the surface topography and the mechanical properties of the sheet metal due to plastic deformation resulting from friction. It was found that under the most favorable lubrication conditions (sample pre-strain 21%, nominal pressure 6 MPa), karanja oil reduced the coefficient of friction by approximately 33%. Both non-edible lubricants provided the best lubrication when testing samples pre-strained at 7% under the whole range of nominal pressures. It was also revealed that in the case of the smallest pre-straining of the specimens (7%), karanja oil was the most effective within nominal pressures of 3–6 MPa, while at higher pressures (9–12 MPa), the moringa oil lowered the value of the coefficient of friction to a greater extent.

Theoretical study of the accuracy of the height dimensions of forgings for upsetting and closed forging operations, taking into account the choice of forging and pressing equipment

The use of low-waste technologies in blank production in the process of performing cold die forging (CDF) operations involves the use of various types of presses, such as crank, hydraulic and screw ones. The range of forging and pressing equipment is quite wide, so the problem of rational use of a particular type of press always arises. Any press must provide the necessary force to deform the original workpiece. Technological processes of metal forming are accompanied by high specific forces of resistance to deformation of materials, which is realized by the design features of the working link of forging and pressing equipment. It should be noted that one of the most important criteria influencing the choice of a press for performing CDF operations is the achievable accuracy of stamped forgings. Taking into account the design features of the types of presses, there are significant differences between them. These differences will be determined by the forging deformation conditions. The performed analytical calculation of error conversion coefficients for forgings during CDF operations makes it possible to evaluate the influence of the factors of the original workpiece on the accuracy of the height dimensions of the forging itself. The obtained graphic dependences for crank, hydraulic and screw presses show the relationship of conversion factors depending on the initial errors of the forgings and the rigidity of the forging itself to the accuracy of height dimensions. As a rule, the rigidity of a forging is determined by the ratio of diameter and height for the upsetting operation, but in the case of a closed forging, the radius at the edges must be taken into account. The article is devoted to a theoretical study of the height error of forgings for the operation of upsetting and closed forging, taking into account the used forging and pressing equipment.

Microstructure and Wear Resistance of Hot-Work Tool Steels after Electron Beam Surface Alloying with B4C and Al

(1) Background: Operational properties and durability of dies in different metal-forming processes significantly depend on their surface quality. Major die failures are related to surface damage due to heat checking cracks, wear, etc. Thereby, strengthening of the working surfaces of dies for hot bending, stamping, forging, and die casting processes is an urgent engineering challenge. Surface alloying with high-energy beams improves the properties of steel products. In these processes, the alloying powders and the treated surfaces can be remelted by electron beam within a short time while the bulk structure of the component remains unchanged, resulting in minimal distortion. The paper presents the results of the electron beam surface alloying (EBSA) of H21 and L6 tool steels with the treatment pastes containing boron carbide and aluminum powders. (2) Methods: Two types of pastes were used for surface alloying: a single-component (B4C) paste and a two-component (B4C+Al) one. The microstructure, microhardness, wear resistance, and elemental and phase composition of the layers obtained on steels were investigated. (3) Results: Four layers up to 0.4 mm thick were distinguished on the surface of the steels after the EBSA. Metallographic analysis showed coarse dendrite formation in the layers embedded in matrices of a eutectic or a solid solution. Microhardness of the steels after the two-component EBSA was higher than after B4C EBSA, which was related to a higher concentration of hard phases, such as iron borides and carbides. In addition, aluminum boride was revealed by the XRD analysis on L6 steel after B4C+Al EBSA. (4) Conclusions: Wear test indicated that the most resistant samples were H21 steel after single B4C EBSA and L6 steel after B4C+Al EBSA. Both samples contained carbon particles in the layer contributing to the high wear resistance as a lubricant. The conducted research is beneficial for mechanical engineering, automotive engineering, medical technology, aerospace engineering, and related industries, where coatings with high microhardness, wear resistance, and surface quality are demanded.

A Review on Design of Additively Manufactured 3D Printed Tools for Sheet Metal Forming Processes

The additive manufacturing technology is progressing at a faster rate than any other manufacturing process, as it influences the process innovatively and facilitates customize products and iterative design, which help the production system to achieve a higher goal. Further, rapid prototyping like the 3D printing process is now being the alternative support system for traditional manufacturing. The industries are relying on rapid prototyping, which is now a key factor in competitive leading market conditions. Due to the growing interest, industries such as sheet metal forming, aerospace, automotive, healthcare, electronics, food, fashion, and retail are adopting this technology aggressively. On the other hand, to optimize the geometry and process parameters of sheet metal forming for economic batch production, sheet metal industries are using 3D printed tools for forming processes. In this study, the review of sheet metal forming processes is done based on the design of tooling development by Fusion Deposition Modelling 3d printing technology. Further process parameters like punch force, blank holding force, anisotropy, clearance, bend allowance are studied for deep drawing and V-bending process. In a later stage cost, comparisons of standard steel tools and polylactic acid (PLA) tools are carried out on basis of volume, density, and cost. The findings suggest that 3d printed tools can be used for small lot production due to easy availability and flexibility in the manufacturing system of the sheet metal forming process.

Tube and Sheet Metal Forming Processes and Applications

In the late 1960s, pioneer works by Keeler [...]

Perspectives on data-driven models and its potentials in metal forming and blanking technologies

Today, design and operation of manufacturing processes heavily rely on the use of models, some analytical, empirical or numerical i.e. finite element simulations. Models do reflect reality as best as their design and structure may appear, but in many cases, they are based on simplifying assumptions and abstractions. Reality in production, i.e. reflected by measures such as forces, deflections, travels, vibrations etc. during the process execution, is tremendously characterised by noise and fluctuations revealing a stochastic nature. In metal forming such kind of impact on produced product today in detail is neither explainable nor supported by the aforementioned models. In industrial manufacturing the game to deal with process data changed completely and engineers learned to value the high significance of information included in such digital signals. It should be acknowledged that process data gained from real process environments in many cases contain plenty of technological information, which may lead to increase efficiency of production, to reduce downtime or to avoid scrap. For this reason, authors started to focus on process data gained from numerous metal forming technologies and sheet metal blanking in order to use them for process design objectives. The supporting idea was found in a potential combination of conventional process design strategies with new models purely based on digital signals captured by sensors, actuators and production equipment in general. To utilise established models combined with process data, the following obstacles have to be addressed: (1) acquired process data is biased by sensor artifacts and often lacks data quality requirements; (2) mathematical models such as neural networks heavily rely on high quantities of training data with good quality and sufficient context, but such quantities often are not available or impossible to gain; (3) data-driven black-box models often lack interpretability of containing results, further opposing difficulties to assess their plausibility and extract new knowledge. In this paper, an insight on usage of available data science methods like feature-engineering and clustering on metal forming and blanking process data is presented. Therefore, the paper is complemented with recent approaches of data-driven models and methods for capturing, revealing and explaining previously invisible process interactions. In addition, authors follow with descriptions about recent findings and current challenges of four practical use cases taken from different domains in metal forming and blanking. Finally, authors present and discuss a structure for data-driven process modelling as an approach to extent existing data-driven models and derive process knowledge from process data objecting a robust metal forming system design. The paper also aims to figure out future demands in research in this challenging field of increasing robustness for such kind of manufacturing processes.

Room temperature and high temperature micro-forming analysis of SS304 foil

ABSTRACT The micro-sheet metal forming (MSMF) processes such as microstamping and micro-deep drawing can be used to mass-produce miniature parts. However, to design the tools and the processes, material behavior of workpiece under various deformation conditions is required. This paper analyzes the material behavior of 200-µm thickness Stainless steel-304 foil with room-temperature tensile (RTT) tests and high-temperature tensile (HTT) tests. The effect of strain rate and temperature on flow stress behavior, surface roughness, microstructural evolution and fracture mechanism have been examined. It is observed that the percentage elongation for HTT tests is significantly higher than as compared to RTT tests. However, the percentage elongation and the tensile strength during HTT tests are dependent on the strain rate and decreases with a decrease in the strain rate. Recrystallization followed by grain growth in the material took place during high-temperature deformation, thereby changing the surface roughness and fracture mechanism. All the RTT specimens showed ductile failure with characteristic trans-granular dimpled fracture surfaces. The HTT specimens, in contrast, have intergranular fracture by grain pull out due to crack propagation along the grain boundaries. The present analysis can be used to guide the designing of micro-sheet metal forming processes to obtain the required micro-parts.

Design and implementation of magnetic field effect sensor for ISF process

In this paper, an efficient approach for sheet metal thickness measurement is proposed. It is based on the concept of magnetic field effect resonance commonly called as Hall effect. The combination of magnet and metal tools generates the DC voltage signal. The magnitude of the generated signal is inversely proportional to the distance between magnet and tool and hence the thickness of the sheet metal. The proposed idea is designed and implemented successfully using suitable hardware. Initially, the designed circuit is tested manually using the Hall-effect sensor and the sheet metal of different thicknesses. Further, the various experimentations are carried out on the complete CNC machine-based incremental sheet metal forming setup to examine the effectuality of the proposed design. Moreover, the evaluation of the manufactured ISF part has been carried out using the image processing technique. It is observed that the proposed approach can be used efficiently in the application such as the incremental sheet metal forming (ISF) process in real-time for thickness measurement.

Overview on massive forming processes, future and their challenges

The massive shaping processes (forging, rolling, extrusion, wire and bar drawing) play an important role to fabricate metal products. These forming processes undergo plastic deformations of the metal and acquire required shapes and sizes by application of suitable stresses such as tension, compression and shear. Thus due to the characteristics such as cost effectiveness, good mechanical properties of the product, flexible operations, higher productivity, no wastage of the raw material and faster production rate, the work on metals in effective way becomes highly important. Bulk forming and severe deformation process result in massive shape change. The surface area-to-volume of the work is relatively small and mostly done in hot working conditions. The broad topic of bulk metal forming includes many processes both as classical and modified categories. These classical bulk metal forming processes are still in great demand in many industry sectors. It does not seem that this trend will slow down as new technologies have been developed over recent years. These technologies are continuously modified for new demands, such as higher precision (near-net shape) forming, micro-/nano-forming for micro-components, and bulk-sheet metal forming processes for complex workpieces. Thus, it is important to have a broad knowledge of the classical theories of metal forming which was mainly an overview of metal forming processes and their fundamentals. With the growing competitive industrial vibe, it is important to develop into cost-effective production processes. Especially for some automotive components, it is suggested to incorporate bulk metal forming processes into sheet metals to produce high-quality sheet metal components commercially. Sheet-bulk metal forming (SBMF) processes are defined as sheet metal forming where the flow occurs in three dimensions similar to bulk metal forming. After computer-aided design of the tool geometry, the bulk metal forming tools are usually fabricated by machining processes. The main die manufacturing process may be divided into die design, rough machining, heat treatment, finish machining, manual finishing (polishing), or benching and hard coating. The main characteristic of these processes is that the final product has the dimensions of a magnitude similar to the sheet thickness, projecting out of the plane of the sheet. Based on this characteristic, only some special bulk forming processes can be applied on sheet metals. In this review paper, the authors describe the working of various types of bulk metal forming processes, historical development, importance, future scope and challenges, so that this paper may serve as a good reference for forming process selection and identification for researchers, engineers and students.

Fuzzy logic model-based punch force prediction for deep drawing of high strength steel

The process of sheet metal forming is referred to as Deep Drawing. It is applied to make hollow–curved metal surfaces using a die and punch which creates the hollow burrow. This process is widely used in various industries to form sheet metals into automatic parts of certain requirements. The punch force applied in the die depends upon various parameters. The punch force is also responsible for the effective outcome of the deep drawing of the metal sheet. Thus, a set of process parameters that majorly affects the punch force is decided and those experiments were done to obtain the punch force at different values for different input parameters. Producing punch force requires huge energy expenditure. Hence, for the process to be both economical and efficient – lower punch forces are preferred. But when multiple parameters are considered, it becomes difficult to obtain the lowest punch force value. Hence, with the L27 orthogonal array, the number of combinations of the experiments that need to be done is reduced phenomenally. These experimental data were used to create a fuzzy logic model using MATLAB software. Therefore, a Fuzzy Logic Model was generated with the considered parameters being the input and the punch force being the output. This model will be used for punch force prediction as well as finding the optimized input parameters to achieve the lowest punch force.

Application of intelligently controlled technologies in designing of technological processes for explosive forming of shell parts

The object of research is the processes of pulse metalworking (hydroexplosive, magnetic pulse, electrohydraulic, gas detonation forming, etc.). Among these methods of forming for the production of aircrafts engines parts from cylindrical and conical blanks, the most efficient in terms of its energy capabilities and overall dimensions is explosive. The modern level of theory and practice of metal forming processes allows, on the basis of a systematic approach and control theory, to determine the optimal parameters of plastic forming processes, select the best technical solutions, and create a precondition for the transition to complex automation. The most difficult task of metals forming methods optimizing is to find the best solution among many potentially possible ones, considering the introduced restrictions and efficiency criteria, environmental, economic, technical, ergonomic, and other requirements. The most problematic is that it is impossible to optimize the process of forming post-factum (finishing works, elimination of defects in shape and size, welding of cracks, etc. are required), therefore, when solving optimization problems, the implementation of the feedback principle is required - comparison of the value of the controlled variable, determined by the control program, with the desired value. In general, the processes of metal forming by pressure are characterized by a variety of problems of the theory of optimal control, the solution of which is carried out by methods of mathematical programming. And, although the equipment for pulse processing can have a different design, it necessarily includes structural elements that make it possible to convert the energy of the source and with its help (through the action of a solid body, transmitting medium, or field) to deform the metal of the workpiece. Due to this, in this work, it is proposed to control the quality of the obtained parts by varying the degree of deformation of the workpiece in the process of forming. The result of the work is the development of an integrated intelligent system, with the help of which it is possible to carry out the computer-aided design of almost all pulse-action processes based on the intelligent selection of suitable forming parameters.

A nonlinear process monitoring strategy for a Metal Forming process

The article deals with the development of a nonlinear statistical process monitoring strategy for a metal forming process. The developed strategy is based on Kernel Principal Component Analysis (KPCA) and has been adopted to address the issue of inherent nonlinearity amongst the measured characteristics. Fault Detection has been carried out by the employment of KPCA score based Hotelling T2 chart. The devised strategy was applied over a Rolling Mill Unit (RMU) which comes under Bulk Metal Forming process. Observations pertaining to the Process and Feedstock Characteristics (PFC) of the RMU have been considered for the analysis. The devised monitoring strategy has been found to be efficient in carrying out the fault detection.

A new void coalescence mechanism during incremental sheet forming: Ductile fracture modeling and experimental validation

• Investigated a new void coalescence mechanism and its effect on ductile fracture of ISF. • Improved formability of ISF is attributed to closely-packed void cluster. • Proposed extended GTN model for ISF by considering oriented void cluster. • Validated proposed model with various process conditions and deformation states. The forming limit of sheet metal can be significantly improved by incremental sheet metal forming(ISF) process, however lacks of relevant fundamental researches. Besides, accurate prediction of formability based on deeper understanding of deformation mechanism is beneficial for the evaluation of ductile failure behavior in ISF process. In the present work, a new void coalescence approach, that voids coalesce closely along meridianal direction rather than conventional thickness direction, is proposed and its influence on formability is investigated. The improved formability is attributed to the formation of closely-packed void clusters along meridianal direction, and these void clusters can stably exist inside the sheet metal even after void coalescence. By introducing two independent parameters into classic GTN model, an extended GTN damage model is developed to describe this new void coalescence mechanism in ISF process, and is validated through a series of experiments. Through investigations in this work, the fundamental understanding of improved formability in ISF is revealed, and the extended GTN model shows its comprehensive capability in predicting ductile fracture behavior with a satisfactory accuracy.

Efficient Computation of the Sharpest Bounds on the Probability of Failure of a Sheet Metal Forming Process

AbstractThe determination of the sharpest bounds on the probability of failure (PoF) based on the Optimal Uncertainty Quantification (OUQ) framework relies on the solution of non‐convex global optimization problems. These problems are subjected to non‐linear constraints to reflect moment constraints from available data, which impedes the numerical efficiency of the method. A different parameterization approach of the optimization problem utilizing canonical moments allows the transformation to only bound constraints and hence, an improved numerical efficiency can be reached. The performance of this new approach is contrasted with the performance of the original approach on the basis of a numerical simulation of a sheet metal forming process.

An Experimental and Numerical Evaluation of Steel A105 Friction Coefficient Using Different Lubricants at High Temperature

The coefficient of friction plays a key role in the metalforming process, especially at high temperatures, to reduce the required energy for material forming. In this study, compression ring test was carried out to determine the shear friction coefficient of the hot-working steel alloy A105 at 1050 °C. The friction coefficient was evaluated for specimens without lubrication and graphite, mica, and glass powder lubricants. The variations in specimen inner diameter during the deformation process were then calculated at several coefficients of friction using the finite element analysis. By employing experimental and numerical results, the coefficient of friction for each lubricant was determined. The results showed that the predicted coefficient of friction for dry samples was 0.62. Moreover, the friction coefficient values obtained using graphite, mica, and glass powder were 0.46, 0.29, and 0.18, respectively.

A COMPARATIVE STUDY ON DEEP DRAWING PROCESS AND AUTOFORM SIMULATIONS OF DX54D + Z and DX56D + Z STEELS

A Sheet Metal Forming (SMF) process, especially deep drawing, is one of the manufacturing processes that commonly used in the automotive industry. Compared with casting and forging, the SMF process has several advantages, including lesser weight materials and broader variations in shape that can be made. The most important of the problems in the SMF process is the wrinkling phenomenon and tearing of sheet products. The wrinkle and tear occurs because of the mechanical properties of the material, product geometry, and blank holder force. The finite element based Computer-Aided Engineering (CAE) program AutoForm Plus R7 used in this article was used for analysis. Solidworks software was used during mold design. AutoForm is a highly productive software that provides high accuracy and reliable results, specially developed for the sheet metal forming mold industry, especially for the automotive industry. With AutoForm, multiple analyses were made by computational calculations, even before the mold production started, and with the help of these analyses, the closest to perfect mold outputs were obtained. In addition, optimum drawbead geometry and springback effect were analysed. The most suitable material was selected for the deep drawing product. DX54D + Z and DX56D + Z from continuously hot-dip coated steel flat products selected as analysis materials. As a result, the simulation reports obtained from this study were compared with many results in the literature. It is concluded that DX56D + Z sheet material can be used in deep drawing products without negative consequences such as tearing, wrinkling and shrinkage marks.

Emerging Trends in Single Point Incremental Sheet Forming of Lightweight Metals

Lightweight materials, such as titanium alloys, magnesium alloys, and aluminium alloys, are characterised by unusual combinations of high strength, corrosion resistance, and low weight. However, some of the grades of these alloys exhibit poor formability at room temperature, which limits their application in sheet metal-forming processes. Lightweight materials are used extensively in the automobile and aerospace industries, leading to increasing demands for advanced forming technologies. This article presents a brief overview of state-of-the-art methods of incremental sheet forming (ISF) for lightweight materials with a special emphasis on the research published in 2015–2021. First, a review of the incremental forming method is provided. Next, the effect of the process conditions (i.e., forming tool, forming path, forming parameters) on the surface finish of drawpieces, geometric accuracy, and process formability of the sheet metals in conventional ISF and thermally-assisted ISF variants are considered. Special attention is given to a review of the effects of contact conditions between the tool and sheet metal on material deformation. The previous publications related to emerging incremental forming technologies, i.e., laser-assisted ISF, water jet ISF, electrically-assisted ISF and ultrasonic-assisted ISF, are also reviewed. The paper seeks to guide and inspire researchers by identifying the current development trends of the valuable contributions made in the field of SPIF of lightweight metallic materials.

APPLICATION OF CURRENT LINES IN DETERMINING KINEMATIC CHARACTERISTICS IN STATIONARY PROCESSES OF PLASTIC FLOW OF METAL

Methods of theoretical solution of problems in the processing of metals by pressure are insufficiently developed for practical use in the development and implementation of new technologies and improvement of existing ones. To meet the stringent requirements for the accuracy of determining the stress-strain state, it is necessary to have reliable information about the evolution of the development of the plastic deformation process at each point of the metal from the very beginning of the deformation. This will allow to obtain with high accuracy the important characteristics of the technological heredity of the products that they acquire as a result of their plastic processing. The first and important step in the calculations of the stress-strain state is to obtain the kinematic characteristics of the plastic flow of metal in the form of analytical dependences, which will formulate the patterns of deformation in the technological processes of metal forming. The article considers the possibility of applying the method of current functions to determine the components of the strain rate tensor in established stationary processes of plastic deformation. It is assumed that in the case of axisymmetric plastic deformation of a metal in a channel with curvilinear boundaries, the kinematics of the process is similar to a plane flow. In obtaining the equations, the differential equation of current lines taking into account the incompressibility condition was used to determine the components of the strain rate tensor. To explain the physical meaning of the current functions, two infinitely close current lines were considered in the flow plane, and an expression was obtained for the flow through a finite transverse current tube. In the absence of radial velocity components at the boundaries, constraints are obtained that are imposed on derivatives of current functions at these boundaries. The developed method of calculating the kinematic characteristics of plastic deformation for established axisymmetric stationary processes will simplify the mathematical processing of the obtained results and increase the reliability of the determination of the stress-strain state.

Blank Shape Optimization Considering 3D Space Targets for External and Internal Boundaries in Sheet Metal Forming Processes

Optimum design of the shape of the initial blank is an important task before sheet metal forming processes. It reduces production costs, material waste and improves the quality of the product significantly. In the present work, the blank shape optimization problem is considered based on the 3D space target contours and moreover the sheet metal can have an internal boundary. In other words, the shape optimization process can be applied on the internal boundary, external boundary or both. To the best knowledge of the authors, there are no published works in this subject. Using the iterative simulation-based optimization process, a special shape error index and also updating algorithm were proposed to modify the blank geometry in each iteration until capturing the optimum shape. The sheet forming process is highly nonlinear in nature due to plastic behaviors, large deformations and frictional contact surfaces. Therefore, the updating formula should be robust enough to have less sensitivity with respect to the initial guess. To evaluate the proposed updating formula and its robustness, some numerical examples were considered and the effects of different tools geometries, 2D and 3D target contours, internal and external boundaries and different initial guesses were examined.

Corrosion Resistance of Open Die Forged Austenitic Stainless Steel Samples Prepared with Different Surfaces

The use of corrosion-resistant metal materials in highly aggressive environments contributes to the preservation of the environment because it reduces the use of protective agents and coatings. Most metal objects are produced by some metal-forming process. It is well-known that plastic deformation affects the corrosion resistance of different metal materials in different ways. As a rule, austenitic stainless steels show a positive impact of plastic deformation on corrosion resistance, especially when hot deformed with protective surface oxide layers. However, most research carried out on these metals involves a carefully prepared surface which is either finely ground or polished. This paper investigates the corrosion resistance of cold-formed (open die forged) austenitic stainless steel in three different surface states for three different degrees of deformation. In doing so, we simulate possible damage to the treated surface and evaluate the stability of the material with respect to corrosion. Good corrosion resistance is shown for all three stages of deformation and for all three surface states, with some differences in the obtained results. Although the polished surface shows the highest corrosion resistance, as expected, the other two surfaces also demonstrate good results when exposed to aggressive environments. All of the results were statistically processed and presented. The results demonstrate the high usability of such materials in corrosion-aggressive environments with minimal danger of corrosion and minimal need to include additional surface protection agents, even against possible surface damage.