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The increasing demand for high-strength lightweight hollow shafts in transportation highlights the need for advanced fabrication techniques. Al–Zn–Mg–Cu alloys, noted for their superior properties, are selected for three-roll skew rolling (TRSR). In TRSR, the material undergoes combined axial tensile and radial compressive stresses. This study evaluates the feasibility of TRSR for producing high-strength lightweight hollow stepped shafts from Al–Zn–Mg–Cu alloy. An integrated approach, including constitutive modeling, hot processing map development, and TRSR numerical simulations/experiments, is employed to optimize the TRSR forming process. The constitutive model was established based on 300°C–450 °C & 0.01–10 s−1 hot compression and 350°C–430 °C & 0.1–5 s−1 high-temperature tensile test data. The established Johnson-Cook optimization by genetic algorithms (GA-JC) model and unified viscoplastic constitutive model, accurately capture the alloy's hot deformation behavior, exhibiting minimal average absolute relative errors (AARE) of 5.431% and 5.808%, respectively. Microstructure evolution analyses shed light on the predominant softening mechanisms, emphasizing dynamic recovery (DRV) at elevated strain rates and diminishing texture intensity with escalating deformation temperatures. The composite hot processing map delineates optimal process parameters (400°C–450 °C & 0.1s−1-1s−1), facilitating informed decision-making in manufacturing practices. The validation of numerical simulations through TRSR forming experiments with initial temperature of 450 °C for the billet and axial moving speed of 10 mm/s for the chuck in affirms the feasibility of producing hollow stepped shafts from high-strength Al–Zn–Mg–Cu alloy. Close agreement was found between simulated and experimental wall thickness variations. This study enhances understanding and optimization of TRSR forming for high-strength lightweight alloys, advancing industrial manufacturing methodologies.

This paper presents selected results of theoretical and experimental research into the manufacture of axisymmetric bimetallic components using three-tool skew rolling technology. In the tests, it was assumed that the outer layer would be a material intended for heat treatment. However, low-carbon steel was used for the core. Experimental investigations were carried out in an innovative CNC skew rolling mill. Tests were carried out at different technological parameters of the process. In addition, the geometric parameters of the billet and the way it was heated were analyzed in relation to the quality of the resulting weld between the two materials. The quality of the weld was assessed based on metallographic observation and on strength tests (shear method). On the other hand, theoretical studies were based on numerical modeling (FEM). The numerical analysis made it possible to determine the distribution of temperature, deformation and stress in the rolling bimetallic component. The results obtained indicated that it is possible to produce bimetallic materials from the proposed steel grades. In addition, a significant effect of the method of heating the billet in the chamber furnace on the microstructure in the joining zone and the shear strength was found. There was an increase in Rc strength of about 35% when using oxidation protection. The results indicated better strength when the billet is rolling with a smaller outer layer thickness (about 50 MPa). This was confirmed by the results obtained from the FEM analysis, which indicated higher values of plastic strain and the occurrence of higher compressive stresses in the near-surface zones of the rolled bimetallic forging, both of which facilitate the welding process. From the temperature distribution (in the range of (600–1200) °C) obtained during the rolling of the bimetal forging, it can be seen that contact with cold tools does not affect the temperature in the welding zone.

Skew rolling with three rolls is used for producing axisymmetric parts. In this method, the tools are spaced every 120° on the circumference of the workpiece. They are also set askew relative to the rolling axis. Cross sectional reduction is made effective by moving the tapered rolls closer to or away from the center line of the workpiece. Experiments were conducted with variable initial conditions of the rolling process to examine surface topography of rolled parts. Obtained experimental results were then analyzed using machine learning methods in order to determine the most effective regression model with the highest coefficient of determination R2 for waviness prediction.

This study investigates the cross wedge rolling (CWR) process for manufacturing a rail axle in a scale of 1:6. Three cases of the rolling process are modelled numerically: standard rolling, wasteless rolling and rolling from a preform. The rolling cases under analysis are compared in terms of material and energy consumption, forming loads as well as propensity to internal and external defect formation. Using the Cockcroft-Latham criterion and the limits of this criterion determined by the rotary compression test, an assessment was made of the propensity of the material to fracture during the rolling processes analysed. Based on numerical results, standard CWR is selected for experimental verification. Obtained experimental results confirm that CWR is an effective method for producing railcar axles that are free from both internal and external defects. The experimental and numerical results obtained confirm that cross wedge rolling technology can be successfully used under industrial conditions for the production of long axles or shafts.

To solve the problem of the long forming process for hollow shafts with constant wall thickness (HSCWT), a new process for forming HSCWT, namely three-roll skew rolling, has been proposed. First, the working principle of the three-roll skew rolling process is presented. Then, the finite element model (FEM) of the three-roll skew rolling HSCWT is established. The strain-stress field and temperature field distribution rules of the three-roll skew rolling HSCWT are analyzed with FEM. The stress-strain field of the rolled piece is distributed uniformly along the axial direction but not uniformly along the radial direction. The variation of the temperature field is related to the axial traction velocity. The greater the axial traction velocity, the smaller the variation of the temperature field. The temperature of rolled pieces varies within 100 °C during rolling. Finally, the three-roll skew rolling experiment of the HSCWT is carried out. The results show that the three-roll skew rolling process can form HSCWT. The temperature field of the three-roll skew rolling HSCWT is evenly distributed. The selection of larger axial traction velocity is conducive to the forming of rolled pieces. The three-roll skew rolling technology has achieved near constant temperature forming of HSCWT.

This article presents a new calibration test for damage functions that uses the cross-wedge rolling method (CWR). In this test, the forming conditions were altered by applying wedges with decreasing forming angle on conical-cylindrical samples. The conditions worsened as the distance from the centre of the sample increased. At a certain point, the conditions became sufficiently unfavourable that the material cracked. To determine the critical values of material damage, the location of cracking in the sample was determined. Then, based on a numerical simulation, the value of the damage function in this area was determined and assumed to be the critical damage value. Using the presented method and normalised Cockcroft–Latham criterion, critical damage values for C45 grade steel in the temperature range 900–1100 °C were determined. It was observed that the critical material damage was highly dependent on the forming temperature. The determined critical damage value was used to model material fracture in a CWR process that was performed using parameters ensuring that this internal defect would occur. A comparison of the numerical and experimental crack lengths showed that they were in perfect agreement, which confirms that the developed calibration test can be used for modelling damage in CWR processes.

This study investigates the problem of predicting material cracking in cross-wedge rolling (CWR). Fifty-four cases were analyzed using the finite element method (FEM), and maximum values of the damage function were determined. Based on the results obtained from simulations, nomographs were created to allow for quick and easy determination of the maximum damage function values depending on the basic CWR parameters, mainly the forming angle, spreading angle of the wedge, and deformation ratio. The rotary compression test of a cylindrical sample was used to determine the critical damage values for the C45 grade steel formed in the temperature range 950–1150 °C. For the fracture condition to occur, it was assumed that the damage value should be higher than the critical damage value given by the damage function. This hypothesis was experimentally validated. The results of the experiments show good agreement with the numerical results of material fracture obtained with the method described in this study.

The paper focuses on a new method for forming axisymmetric parts of considerable length in a CNC skew rolling mill. The laboratory rolling mill was used to conduct rolling tests for car axles (in scale 1:5). Although produced parts are free from internal defects such as fracture and shrinkage porosity, there occurs a local pile-up of the material leading to an increase in the workpiece diameter, as well as spiral grooves are formed, predominantly on conical surfaces. The impact of basic parameters of the skew rolling process on the formation of identified internal defects is assessed analytically and numerically. Experimental tests are performed to determine the effect of spiral grooves on the quality of final products, particularly forgings produced from skew rolled preforms.

The article presents the problem of ductile fracture of metals and metal alloys formed in hot working conditions. The basic damage criteria used in modelling fracture as well as calibrating tests used to determine the critical damage values were discussed. A concept of a new calibrating test based on rotary compression of a disc or a cylinder was presented. Using the proposed calibrating test along with nine damage criteria the critical damage values for 50HS (1.5026) grade steel, formed in the temperature range 950 °C to 1150 °C were determined. A significant dependency of the critical damage value on temperature was observed. The stress states occurring in rotary compression and the cross-wedge rolling, skew rolling in a two-roll rolling mill and helical-wedge rolling processes were compared. On the basis of the results obtained it was advised to apply rotary compression of a cylinder samples to determine the critical damage values used in the analyses of cross- and skew rolling.

The paper deals with the problem of material fracture prediction in metal forming processes. It has been found that the application of well-established solutions for ductile fracture prediction to the modelling of cross rolling processes leads to serious errors. These errors result from the fact that the limit value of the damage function determined via uniaxial tensile and compression tests is too low. Therefore, it is necessary to devise a new test in which the state of stress is similar to that in a cross wedge rolling process characterized by the occurrence of alternating compressive and tensile stresses.

The paper reports the results of a numerical analysis of helical-wedge rolling (HWR), a new metal forming method developed at the Lublin University of Technology. The numerical analysis was performed for three axisymmetric parts: a rotary cutter body, a stepped shaft and a ball pin. The numerical modeling was performed using the commercial simulation software Forge NxT 1.0. The paper examines changes in workpiece shape as well as variations in effective strains, temperatures, damage function, force parameters (on the rolls and guides), and torques acting on the rolls. It has been found that due to its advantages (low material losses and high efficiency), the new helical-wedge rolling process can be used as an alternative to currently employed methods for producing axisymmetric products.

The article presents the results of model tests with which a comparative analysis of two methods of ball separation during the skew rolling process was carried out. A verification of the results obtained in the physical modelling process with the results obtained in the real process of skew ball rolling was also carried out. During the physical modelling, the effect of changing the ball separation method on the quality of the products obtained, variations in maximum torque values and maximum radial forces were analyzed. In the case of real tests, the results were verified with the results of physical modelling, in which the surface quality and torque values for one of the tool sets were compared. Physical modelling was used to verify the differences between the two methods of ball separation. Commercial plasticine based on synthetic wax from the manufacturer PRIMO was used as a model material for physical analysis. The plasticine used for testing was cooled to 0 °C and the cooling process took 24 h. The tools used for the physical modelling were 3D printed and the material used was ABS. The method of physical modelling using plasticine as a model material allows for a correct analysis of hot metal forming processes.

The paper presents a new extrusion process for producing twist drills using split dies. The design of the dies is described, where the profile of the flute-forming element is the same as the profile of the flute on the plane inclined to the drill axis at an angle equal to the helix angle. The proposed method for the extrusion of twist drills by the new type of dies is verified by numerical modeling. Three cases of the extrusion process are modelled, each with a different position of the flute-forming element relative to the axis of the drill. The paper investigates the effect of the position of the flute-forming element on the angle of inclination of the flutes and the cross-section shape of the drill. Numerical modeling is performed using DEFORM-3D.

This paper presents the chosen results of ball pins hollow forgings forming by means of rotary compression. Theoretical research was based on numerical simulations, conducted using finite element method. The software Simufact was applied for calculations needs. During simulations, kinematics of material flow, strain intensity distribution, damage criterion according to Cockroft-Latham and temperature distributions were determined. Force parameters in the process were also determined and limiting phenomena were identified. Results from FEM modeling were verified in laboratory conditions. Ball pins hollow forgings forming tests were performed in a special forge aggregate. The obtained results fully confirmed the possibility of ball pins hollow forgings manufacturing by means of rotary compression.

This paper presents the results of numerical modeling of skew rolling process of twist drills in four-segments configuration. On the basis of the conducted numerical simulation the results were obtained in a form of distributions: stress intensity, strain intensity, temperature and damage. The energetic parameters of the process were also given on the example of a drill Ø10 mm from high-speed steel HS6-5-2. The conducted numerical simulation confirmed the usefulness of the graphic method based on envelope theory in tools designing for skew rolling of twist drills.

This study investigates the problem of material fracture in cross wedge rolling (CWR). It was found that this problem could be analysed by means of well-known phenomenological criteria of fracture that are implemented in commercial FEM (Finite Element Method) simulation programs for forming processes. The accuracy of predicting material fracture depends on the critical damage value that is determined by calibration tests in which the modelled and real stresses must be in good agreement. To improve this accuracy, a new calibration test is proposed. The test is based on the CWR process. Owing to the shape of the tools and test piece used in CWR, the forming conditions in this process deteriorate with the distance from the centre of the test piece, which at a certain moment leads to fracture initiation. Knowing the location of axial crack initiation in the specimen, it is possible to determine the critical value of material damage via numerical simulation. The new calibration test is used to determine the critical damage of 42CrMo4 steel subjected to forming in the temperature range of 900–1100 °C. In addition, 12 criteria of ductile fracture are employed in the study. The results show that the critical damage significantly increases with the temperature.

This paper presents selected numerical and experimental results of a study investigating the process of forming hollow stepped gear shafts from tubes by rotary compression. The objective of the study was to determine whether the rotary compression process is an effective method of producing hollow stepped gear shafts and to identify limitations of this manufacturing method. A theoretical analysis involved the numerical modeling of the proposed process by the finite element method (FEM). 3D simulations were performed using the commercial simulation software package Simufact Forming. The analysis involved examining the material flow pattern along with thermal and force parameters of the process. The FEM results were verified with experimental tests conducted under laboratory conditions. The experiments were performed on a machine specially designed for the rotary compression of hollow parts. Results demonstrate that it is difficult to form a stepped gear shaft in one operation. For this reason, such parts should be formed in two operations. The first operation involves the forming of a hollow stepped shaft by rotary compression, while in the second operation, a gear is formed on one of the steps of the shaft.

The present article reports selected results of a preliminary study of the process of skew rolling of bimetallic rods. The experiments were conducted using a numerically controlled three-roller skew rolling mill. During the tests, bimetallic rods were rolled from billets whose cores and outer sleeves (bushings) were made of different types of steel. The results demonstrate that the proposed method can be successfully used in the production of bimetallic rods. However, proper fastening of the two materials depends on the geometrical parameters of the billets, and the quality of bimetallic rods depends on the heating method used. When the rods are heated without protective atmospheres, the surface layer of the core gets decarburized and the surfaces of the materials being joined together are oxidized, which hinders the welding process and adversely affects the physical and chemical properties of such products. The results of numerical modeling indicate that the material near the surface tends to flow, which may have a negative impact on the welding process. In addition, the distribution of stress in the tool–workpiece contact zone may make welding of the materials difficult. The results reported in this paper are preliminary and constitute a prelude to a more detailed analysis of bimetallic rod rolling.

Magnesium alloys are highly strain rate sensitive and exhibit good workability in a narrow forging temperature range. Consequently, parts made of these materials are usually forged with low-speed hydraulic presses, using specially designed tool heating systems in order to ensure near-isothermal conditions. This study investigates whether popular magnesium alloys such as Mg-Al-Zn can be forged in forging machines equipped with high-speed forming tools. Experimental upset forging tests on AZ31B, AZ61A and AZ80A specimens were conducted, using a screw press with a ram speed of 0.5 m/s and a die forging hammer with a ram speed at stroke of about 5 m/s. Test specimens were preheated to 350 °C, 410 °C and 450 °C. After the upset forging process, they were air- or water-cooled and then examined for their workability, hardness and grain size. To validate the results, a forging process for a producing handle was designed and modelled by the finite element method. Distributions of strain, temperature and fracture criterion were analysed, and energy and force parameters of the forging process were calculated. After that, experimental tests were performed on AZ31B and AZ61A specimens in order to determine mechanical properties of forged parts and examine their micro- and macrostructure. Results have demonstrated that AZ80A is not suitable for forging with either the screw press or the die forging hammer, that AZ61A can be press- and hammer-forged but to a limited extent, and that AZ31B can be subjected to forging in both forging machines analysed in the study.

The paper describes a new method for forming grinding media balls from scrap rail heads. This forming method involves the following operations: cutting the rail head to the desired length combined with lateral pressing of the produced workpiece; flashless die forging and sizing of balls in a helical impression. The proposed method was verified by numerical simulation which involved the modeling of a forming process for producing 80 mm diameter balls. As a result of the modeling, it was possible to examine the changes in the workpiece shape during each forming operation, the variations in loads and torques, as well as the distribution of temperatures enabling performing another forming operation, i.e. quenching. The results confirm that the designed method can be used to produce balls.

The subject-matter of the article is the ductile fracture of materials—A phenomenon occurring in numerous metal forming processes. In order to prognosticate the possibility of a fracture, damage criteria are employed. Their effectiveness, however, depends on the accurate determination of the critical values of damage. These values are obtained through calibrating tests, where the stress state has to be as similar to the actual process as possible. The currently employed calibrating tests do not enable one to determine the limit values of the damage function when the Mannesmann effect occurs. Therefore it was not possible to effectively prognosticate the material fracture in the processes of cross- and skew-rolling. A new calibrating test, based on rotational compression of a cylindrical sample, in which the fractures are caused by the Mannesmann effect, was developed at the Lublin University of Technology. This test was discussed in the article, with a particular focus on the stress and strain state in the sample. A practical use of the test was presented on the example of C45 grade steel, formed in the temperature equal 1150 °C. In the research ten material damage criteria were adopted.

This article presents the results of model tests aiming to verify the possibility of applying commercial plasticine as a model material for modelling the limits to the cross-wedge rolling process. This study presents a comparison of the results of laboratory testing and physical modelling of cross-wedge rolling (CWR) processes. Commercial plasticine was the model material used in the research to model 50HS grade steel formed in 1150 °C. The model material was cooled to 0 °C, 5 °C, 10 °C, 12,5 °C, and 15 °C. Physical modelling of neckings and slippages is only possible when the plasticine is heated to 12.5 °C prior to forming. Commercial plasticine does not enable one to model the cracking process inside the rolled element.

This paper begins with a brief overview of the methods for producing balls. It then discusses the rolling processes for producing balls in helical passes. Next, a method for designing tools for helical rolling (HR) is described. Six different cases of rolling using tools with helical passes of different lengths are modeled by the finite element method (FEM). The simulations are performed with the use of Simufact Forming version 13.3. Based on the 3D simulations, the distributions of effective strain, damage criterion, and temperature, as well as the variations in loads and torques, are determined. This study also predicts the rate and manner of wear of the helical tools, depending on the tool design. As a result, it has been found that an increased length of the helical forming passes is advantageous in terms of tool service life. It has also been found that excessive elongation of the forming zone is not cost-effective.

This paper presents the results of theoretical and experimental investigations of a new process of rolling rods from scrap rail heads. First, the industrial applications of scrap railway rails and methods of their recycling are discussed, and then the concept of two-stage rolling of rods from heads cut off from scrap rails is proposed. In the first stage of the process, a rail head preform was rolled in a hexagonal pass of a longitudinal rolling mill. Then in the second stage, the hexagonal bar was skew rolled into a rod in a helical roll pass. Theoretical considerations were based on finite element numerical modelling. The rolling process was simulated under 3D deformation using Forge NxT v.1.1 software developed by Transvalor Company. Calculations were carried out to determine the material flow kinematics, strength, and thermal parameters of the process and to identify the phenomena that might constrain its implementation. The numerical results were verified in experimental tests, during which preforms and rods were formed from scrap rail heads. The tests were conducted in longitudinal and skew rolling mills. The results indicate that rods can be effectively formed from scrap rail heads in just two steps. Rods obtained using the proposed method can be used as full-featured, semifinished products for the manufacture of various types of machine parts.

This paper presents two rolling technologies: cross-wedge rolling (CWR) and helical-wedge rolling (HWR). The two rolling processes were compared using the example of rolling a ball stud forging. The technologies were modeled in the finite element model (FEM) environment. Calculations were performed to obtain distributions of strain and the Cockcroft−Latham damage criterion. The investigated processes were also performed under real-life conditions. The results of the experiments were used to compare the force and energy parameters of the rolling technologies. Tests were also carried out to investigate the microstructure of the studs and a grain size after rolling. The state of the macrostructure, i.e., the grain flow lines, was also compared. The experiments showed that HWR was a more energy-efficient process.

This article presents the results of theoretical−experimental testing of the process of rotational compression of hollow stepped shafts. The advantages of the technology and the potential area of its application were discussed. Further on, the limits of the rotational compression technology, preventing the manufacturing of high-quality products, were presented. The research was conducted on the basis of numerical modelling using the finite element method in Simufact Forming, as well as the results of experimental tests performed in a forging machine for rotational compression. On the basis of the results obtained, it can be stated that the process of rotational compression of hollow stepped shafts can be hindered by the following phenomena: uncontrolled slip, deformation of the semi-finished product wall, twisting of the formed steps, material cracking, and deformation of the cross-section of the formed steps. The possibility of those hindrances occurring depends heavily on the assumed technological parameters of the process. For this reason, knowledge of the cause of occurrence of those limitations is vital for the development of the technology and the choice of the process parameters.

The article presents the issue of material fracture during the process of cross-wedge rolling (CWR). The object of the research was the process of forming a harrow tooth preform. In the conducted analysis nine damage criteria were applied. The critical value of damage was determined with a new calibrating test, basing on rotational compression of a sample in a channel. The results of calculations were compared to the results of experimental testing performed in laboratory conditions in Lublin University of Technology. On the basis of the obtained results an assessment of the applied damage criteria and their applicability in the analysis of CWR processes was conducted.

The objective of the article was to present the state of the problem of physical modelling of the hot-working processes with plasticine as the model material. It was stated that the aforementioned method can prove helpful in analyzing complex plastic forming processes such as cross rolling and helical rolling of balls. In order to confirm this hypothesis, an attempt at forming steel balls with diameters of 40 mm (cross rolling) and 57 mm (helical rolling) under laboratory conditions was made. Further on, these processes were conducted in model form using special model rolling mills and 3D printed acrylonitrile butadiene styrene (ABS) tools. The comparison of the test results regarding shape and manufacturing accuracy, as well as force parameters, confirmed the validity of using physical modelling in the investigation of the process of cross rolling and helical rolling of balls.

This paper presents selected numerical and experimental results of a skew rolling process for producing balls using helical tools. The study investigates the effect of the billet’s initial temperature on the quality of produced balls and the rolling process itself. In addition, the effect of billet diameter on the quality of produced balls is investigated. Experimental tests were performed using a helical rolling mill available at the Lublin University of Technology. The experiments consisted of rolling 40 mm diameter balls with the use of two helical tools. To determine optimal rolling parameters ensuring the highest quality of produced balls, numerical modelling was performed using the finite element method in the Forge software. The numerical analysis involved the determination of metal flow kinematics, temperature and damage criterion distributions, as well as the measurement of variations in the force parameters. The results demonstrate that the highest quality balls are produced from billet preheated to approximately 1000 °C.

The paper presents a complete numerical model of a helical-wedge rolling process for producing balls. The model was designed in Finite Element Method (FEM)-based Forge NxT v.1.1 that enables the simulation of both forming and separating balls. A comparison of numerical results with experimental findings revealed a very high agreement in both qualitative and quantitative terms. The developed numerical model was used to investigate the effect of flange shape on the helical-wedge rolling process for producing balls with a diameter of 125 mm. Three types of flange tools were investigated, and the best results were obtained for a wedge-shaped flange.

The paper describes an innovative cross rolling method that enables the production of six balls at the same time, each ball with a diameter of 100 mm. The principle of the proposed rolling technique is discussed and the tools used in this forming process are described. Two variations of the proposed method for producing balls were investigated, one performed with the use of flat tools and the other with the use of two rolls. Results of the numerical modelling are discussed. They clearly demonstrate that the proposed method can be used to produce balls with large diameters. Rolling experiments were performed under laboratory conditions to produce 40 mm diameter balls, i.e., in the 1:2.5 scale. The experimental findings show a good qualitative agreement with the numerical results.

This paper presents results of numerical analysis of rolling process of internal toothing. Numerical simulations of the rolling process were made basing on finite element method (FEM), using commercial software DEFORM-3D in version 10.0. Geometrical models applied in FEM calculations were discussed in details. Calculations were made in three dimensional state of strain with consideration of thermal phenomena. During research works, geometrical parameters of obtained parts were analyzed, distributions of effective strain, effective stress and temperatures as well as the process force parameters were given. Next, the influence of particular process parameters on tools durability and the possibility of presence of phenomena disturbing the process stability were discussed. Described results of numerical research confirm the possibility of forming of internal toothing by means of rolling methods and constitute the introduction for a more complex analysis of metal forming processes of internal toothing.