bluuebunny/crossref_metadata_2025 huggingface dataset:
A new dieless forming method for metal bellows induced by local thermal buckling
Authors: Zhang T Y , Li D Q , Xu T J , Sui Y F , Han X H
Published: December 2022

A new dieless forming method is proposed to produce metal bellows induced by local thermal buckling. The thermal buckling forming process is realized according to the local deformation behavior of metal tubes under the action of high temperature softening and axial pressure. In this paper, a forming device is designed and it is capable to produce metal bellows in two forming modes of a discontinuous bellow forming process and a continuous bellow forming process. FEM simulations are used to analyze this thermal buckling forming process and its product performance. The results show that the presented process can increase wall thickness and improve the energy absorption performance of metal bellows. Meanwhile, some thermal buckling forming cases of metal bellows of different materials and different sizes are presented.
Circumferential pure shear test of thin-walled aluminum alloy tubes
Authors: Zhang S N , Wang X S , Lin Z Y , Liu G
Published: December 2022

In order to obtain the pure shear deformation characteristics along the circumferential direction of tubes, a circumferential shear test for thin-walled tubes is proposed in this paper. The experimental device consists of a tubular sample and two cylindrical mandrels with shear plates. The torque along the circumferential direction was applied to the tubular sample by the two shear plates to make the pre-set shearing zone of the sample under a circumferential pure shear stress state. The two cylindrical mandrels support the inner wall of the tube to avoid buckling so that the pure shear stress state can be maintained during the whole deformation process. A 5052 aluminum alloy tube with an outer diameter of 50 mm and a wall thickness of 1.2 mm was used in the test. It is shown through simulation and experiment that shear deformation is concentrated in the pre-set shearing zone. This test can be used to obtain the circumferential pure shear stress-strain relationship.
Investigation on the influence of grinding parameters on surface integrity of substrate in metal additive forging
Authors: Feng J , Zhao Y , Feng D J , Jin Z J , Guo J
Published: December 2022

Additive forging technology is an innovative method for manufacturing heavy forgings by using multi-layer hot-compression bonding. To achieve better bonding performance, the surface of the metal substrate needs to be ground and cleaned before hot-compression bonding. However, the process is less automated in factory production which tremendously hinders the increase of productivity. This paper presents an automatic grinding scheme and the experimental device were designed to verify the feasibility of the scheme. The effects of contact pressure, spindle speed and feed speed on the grinding effect of 316H stainless steel were studied. The results show that the best grinding effect can be obtained when the contact pressure is 25 N, the spindle speed is 8000 rpm, and the feed rate is 30 mm/s, which can significantly improve the product quality and production efficiency.
Effect of loading-path on the elastic modulus degradation of high strength steels
Authors: Yu H Y , Wu H Y , Chu Z K
Published: December 2022

Experiments of repetitive uniaxial tension are performed for DP590, TRIP590, TRIP780, and BH220 steels. Variation of chord modulus of the four materials with accumulated plastic strain is discussed. Large specimens of uniaxial tension, wide plate tension and cruciform tension are prestrained in different plastic strain. Uniaxial tension of sub-size samples which are machined from the prestrained large specimens is performed. Dependence of the normalized chord modulus of the four metals on strain path is discussed in detail. The results show that elastic modulus degradation is dependent on the material strength, accumulated plastic strain and strain path. At the same equivalent strain, the chord modulus degradation of TRIP780, TRIP590, DP590, BH220 steels decreases in turn. The chord modulus of TRIP780 steel at 0.24 equivalent strain reaches 20.5%. The chord modulus of DP590 steel is more sensitive to strain path change than the other three metals. The path of biaxial stretching combined with uniaxial tension provides the greatest chord modulus degradation among the six loading paths. Each material should have the most suitable loading path under which the elastic modulus variation can be minimized so springback can be easily controlled.
Numerical simulation of extrusion of FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube based on finite element method and cellular automaton
Authors: Jiang S Y , Sun D
Published: December 2022

FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube is firstly put forward and it can be fabricated by means of isothermal extrusion. Based on Arrhenius constitutive model of FeMnSiCrNi and NiTiNb shape memory alloys, isothermal extrusion of FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube is simulated by rigid viscoplastic finite element method. It can be found that the deformation zone of the dissimilar shape memory alloy composite tube is always in a three-dimensional compressive stress state during extrusion, and the deformation of the inner tube is obviously higher than that of the outer tube. It is necessary to guarantee the interface compatibility between the inner tube and the outer tube during isothermal extrusion of FeMnSiCrNi/NiTiNb dissimilar shape memory alloy composite tube. The relationship between macroscopic process variables and microscopic variables during plastic deformation of FeMnSiCrNi shape memory alloy tube at high temperature is established by coupling finite element simulation and cellular automaton simulation. The microstructural evolution of FeMnSiCrNi shape memory alloy in different deformation zones during isothermal extrusion of dissimilar shape memory alloy composite tube is simulated. It can be concluded that the grain size of dynamic recrystallization is reduced with the increase of plastic strain in the deformation zone.
Multi-scale simulation of deformation and recrystallization of austenitic stainless steels with solidified columnar crystal structures
Authors: Zhu X T , Zhu H , Chen J , Chen H Q
Published: December 2022

Columnar grain structures (CCS) often distinct in steel ingots, which have to be refined and homogenized during forging. In this investigation, simulation of deformation and dynamic recrystallization of austenitic stainless steels with CCSs were carried out by macroscopic, mesoscopic (microscopic) and nanoscale simulation techniques. (1) Using molecular dynamics simulation method, the nano-CGSs model with different loading directions was simulated. The results show that the deformation stresses are anisotropic with variation of angles between the loading direction and the columnar crystal growth direction. The higher stresses present at the 0° and 90° angles due to higher dislocation density; However, the lower stresses present at the angles from 30° to 60° due to higher stacking faults and twins. (2) The cellular automata (CA) fractal rules were proposed to simulate nucleation and grain growth of dynamic recrystallization by introducing weighted variables considering Σ3 twin nucleation rate for the twinning-promoted recrystallization. The CA method of nucleation at primary columnar crystal boundaries, secondary dendrites and deformation bands was proposed to simulate the joint nucleation. (3) The coupling simulation of macroscopic thermal parameters by finite element method, solidification of columnar structures and hot deformation dynamic recrystallization by CA was realized.
Study on the key process parameters of hydrodynamic deep drawing on the stainless steel single sink with countertop
Authors: Wu F , Hong Y H , Zhao S Q , Chen J , Liang Q J , Mo B J , Zhang Z R , Xiao X T , Zhou F Q
Published: December 2022

Stainless steel single sink with countertop (SC) has the characteristics of large depth and asymmetric countertop. Its traditional stamping process is mainly realized by the combination of multi-stage deep drawing and annealing process, which leads to the complex manufacturing process, long production chain and poor consistency of products. Based on finite element analysis software (Dynaform) with nonlinear dynamic display algorithm, numerical simulation analysis and research are carried out on the parameters of hydrodynamic deep drawing. First, the sink and the part of countertop are preformed into a cylinder shell, and then the excess of the cylinder shell is drawn back to the countertop. The research results show that the hydrodynamic deep drawing process can effectively improve the flow uniformity of stainless steel sheet, increase the forming of stainless steel tank, drawing a more uniform wall thickness, thus effectively improve the quality of single tank with countertop by setting up reasonable preform structure, controlling the liquid pressure and its loading paths and blank-holder force.
Research on forming limit of Ni-based superalloy during spinning under complex strain path
Authors: Xiao G F , Xia Q X , Chang Y , Zhou H Y
Published: December 2022

Ni-based superalloy components with complex shape, such as conical-cylindrical parts, are one of the most important structural components widely used in aviation and aerospace fields. Composite spinning process, consisting of shear spinning and deep drawing spinning, is the most effective method to manufacture this complex component. However, the fracture and wrinkling defects usually occur due to the severe work hardening and complex strain path. Therefore, in order to evaluate the forming limit of Ni-based superalloy during spinning under complex strain path at room temperature, the finite element model of the shear-deep drawing composite spinning was established. The strain path during the shear-deep drawing composite spinning was analysed. The forming limit of Ni-based superalloy was also studied. Then the forming limit diagram of Ni-based superalloy during the shear-deep drawing composite spinning was established. The results show that the limit half cone angle of Ni-based superalloy for shear spinning is 30°; and the limit deep drawing spinning coefficient is 0.63. The strain path can be approximately the superposition of two linear strain paths during shear-deep drawing composite spinning. The safety zone is “wing shaped” in tension-compression strain zone during the shear-deep drawing composite spinning. The experimental results show that the limit diagram can accurately predict the forming defects.
Intelligent template based die face design method for process reuse of automotive panel
Authors: Kong H J , Zhang Z B , Liu Y Q , Wei Y , Wang Z
Published: December 2022

Die face design of automotive panel is a tedious repeated process and depends heavily on experience of engineers, which leads to increase of lead time and production costs. An intelligent template based die face design method is presented for process reuse of automotive panel. In this method, the new part is extracted as feature parameters to match the existing process in the template library automatically and the similar process model is applied to the new part adaptively. Finally, a process reuse system for die face is developed and a typical automotive panel is employed to verify the effectiveness of the proposed method. The results show a favourable effectiveness and practicability in reducing design period and reliance on experience.
Titanium clad plate forming: critical consideration and how different it is from solid titanium forming
Authors: Parmar T , Bangar V , Gupta R , Bhatt K P
Published: December 2022

Titanium offers exceptional corrosion resistance both in organic & inorganic acid media. Thus, it is a preferred material by various industries such as Oil and Gas refining, Petrochemical (PTA Plant) including Nickel refining by Hydrometallurgy. These equipment are operated at high temperature and pressure, necessitating the use of higher thickness for safety and efficient functioning. Therefore, use of solid titanium is not economical, and often substituted with explosion bonded Ti-Clad steel. Fabrication of certain components of this equipment like Dished heads are required to be made by forming with options of cold, warm or hot forming. Selection of forming method for Ti-clad steel component is often governed by its effect on Clad-Base metal bond integrity and reduction shear strength unlike other commonly used Stainless steel or Ni-based alloy clad material, wherein thickness of the base metal is major deciding factor. In case of Ti-Clad steels both cladding and base metal are not metallurgically compatible as well as differs significantly in their physical properties, forming temperature plays a crucial role. This paper describes the effect of various Dished heads forming methodology on integrity of clad plate. Also, it brings out how the Ti-clad steel forming is critical than the forming of solid Titanium.
Simulation and experimental study of GGG70L laser quenching
Authors: Ding H Y , Guan Y J , Li Y Q , Zhai J Q , Lin J , Ren Q H , Li X J
Published: December 2022

GGG70L is a kind of cold-working die steel widely used in large automobile cover parts die. In order to ensure the life of the die, laser quenching process is usually used to form a certain hardened layer at a specific part of the die. In this paper, the changes of microstructure and hardness of ductile iron GGG70L after laser quenching were studied through a large number of process experiments, and the influence of quenching process parameters on the microstructure and properties of GGG70L was obtained. The relationship between the depth of hardened layer and the laser energy density is established and a quadratic function relationship was found between the two. It is found that both higher hardness and deeper hardening depth can be obtained when the energy density is 24-28 (J/mm2). The finite element model of the laser quenching process of GGG70L was established, and the temperature of the hardened zone and its evolution law during the laser quenching process were studied numerically.
Influence of cold rolling process on the Lankford coefficient, drawability and texture of AISI 430 ferritic stainless steel
Authors: Vaughan L L T , Gonzalez B M , Sousa J A G , Cangue F J R , Saraiva I Z , Rocha S H F S
Published: December 2022

The following paper addresses the large demand for further comprehension of the ferritic AISI 430 steels owing to deep drawing processes and accompanying forming technologies, such as rolling. Their good corrosion resistance and relative low cost, make them reasonably well competitors in a great deal of applications. There has been thus evaluated in a pilot mill the influence of three different cold rolling passes with 76% thickness reduction to the drawability and mechanical properties of stainless steel plates. Erichsen, Nakazima and tensile tests were complemented with ODF, pole figure, SEM-FEG observations. It was believed that changes on the cold rolling passes, which alters the anisotropy of materials, would favorably influence deep drawing applications. Experiments revealed, however, that changes defining the deep drawing parameters from 15, 20 and 24 passes, were not statistically significant after rolling. Notwithstanding, texture gradients are reported.
Strain distribution at the transition from bent to unbent regions in tube rotary draw bending: an in-situ, real-time measurement study
Authors: He X , Ma J , Welo T
Published: December 2022

In tube bending processes, accurate control of springback is of crucial importance as this affects the dimensional accuracy of the final product and overall equipment efficiency. The distribution of stress and strain during bending is one of the most fundamental issues determining the springback magnitude of the product. In conventional analyses of rotary draw bending, the deformation behaviour along the bending direction is normally assumed to be uniform for constant-radius bends, following the contour of the die configuration. In practice, however, the stress-strain distribution is non-uniform, particularly at the transition between the bent and unbent regions of the formed component. The distribution makes a significant contribution to springback and its variations, especially for low bend-angle components. This research focuses on exploring the strain distribution at the end transition of the bend of aluminium tubes in rotary draw bending. An experimental test setup for strain measurements with a strain gauge glued to the unbent area has been designed and conducted to measure the strain distribution during bending. The characteristics of non-uniform strain distribution during tube bending, including the evolving transition behaviour at the transition between bent and unbent areas, are studied. The results enhance the understanding of deformation characteristics of bent tubes, and contribute to improved physically-based models and springback control routines in industrial practice.
Virtual rolling automation and setup calculations for six stands FEM finishing mill
Authors: Ilmola J , Seppälä O , Pohjonen A , Larkiola J
Published: December 2022

Digitalization is becoming increasingly common in the steel industry. Formerly developed models of individual phenomenon or separate sub-processes are being further developed into wider complexes where multiple models are coupled together. Virtual rolling automation, which can be used to control a finite-element rolling model, is a new element in these complexes. The automation enables to model the variations caused by the process adjustment. It must be taken in the account that neither the model nor the industrial process are ideal, but there are limitations in the attainable accuracy in both cases. Inclusion of the new automation control in the FE-model introduces new requirements: the setup calculations for all six rolling stands and the automation logic adjustments must perform within the model. The focus of the current article is prediction of the roll force and the virtual rolling automation of six stand finishing mill.
Development of a multi-container extrusion method for extruding lightweight wide plates and sheets
Authors: Li W , Yu J , Lv J , Shi Z , Lin J
Published: December 2022

Extrusion of wide plates and sheets of light alloys has been studied over a long period of time, yet the extrudable width of the material is still limited due to high extrusion force requirement. To overcome this drawback, a new multi-container extrusion process is proposed in the research, which allows the production of lightweight plates and sheets with less force compared to that of existing extrusion methods. A lab scale feasibility study system with three containers has been designed and built and tested for AA1060 billets. Experimental work has been carried out with the extrusion temperature of 450°C and extrusion speed of 0.5 mm/s. Optical microscopy observation and tensile tests have been performed for the extruded materials at different positions to investigate the extrusion welding quality between the three extrusion billets. The test results show that the welding quality improves as extrusion progresses and the overall welding quality is stable. This study demonstrates the feasibility of the new multi-container extrusion method.
Effect of process parameters on forming quality of hollow axle blank with rotary piercing
Authors: Ye C Q , Shu X D , Lin F , Wang J T , Xia Y X , Zhang S
Published: December 2022

At present, hollow axles are mostly manufactured by precision forging and then deep processing, which has long technological process and high cost. In order to realize the integrated forming of hollow axles with short process and low cost piercing and skew rolling, a method of piercing billet by two-roll skew rolling is proposed in this paper, and the finite element model of the forming process is established by using SimufactForming software. The effects of roll feed angle, roll speed and plug advance on the wall thickness uniformity of piercing tube billet are explored, and the process parameters with the best wall thickness uniformity are obtained. It lays a technical foundation for the blank guarantee and the realization of the integrated forming process of hollow axle.
Ti6554 titanium alloy electrically assisted compression: modelling and simulation based on dislocation density theory
Authors: Zhou Y , Wu C , Qu Z , Lin B
Published: December 2022

Electrically assisted compression experiments were conducted on Ti6554 titanium alloy to investigate the electroplasticity behavior under different process parameters (current density, duty cycle) and to analyze the effect of pulsed current on flow stress and temperature. An electroplasticity constitutive model based on dislocation density theory was developed and using ABAQUS subroutine secondary development for electrically assisted compression simulation. The results show that the established electroplasticity constitutive model can better predict the true stress-strain curves under different process parameters, and the average error is controlled at 6%. The evolution law of dislocation density reveals that α, which characterizes the dislocation strength, is smaller with the increase of current density, n and K2, which characterize the dynamic recovery mechanism of the material, increase with the increase of current density, and the dislocation density ρ decreases with the increase of deformation temperature.
Wall thickness control in multi-stage hydroforming of multiwave seal ring with small diameter
Authors: Yan B Y , Meng B
Published: December 2022

Thinning rate is a crucial factor in forming quality of the thin-walled seal ring with complex features. To control the excessive thinning by altering the stress state during the material deformation, a new multi-stage three-dimensional (3D) hydroforming technology was proposed in this work. Based on the characteristics of the seal ring and the used superalloy strip, a multi-stage internal pressure forming process was established through finite element analysis (FEA) and forming experiment verification. In addition, the distribution of wall thickness in every stage was discussed. And the influence of the width of deformation zone and the pressure loading path in the cavity on the wall thickness of the part in each step was studied. Finally, the optimal forming parameters of each step that can achieve a stable state of metal flow were obtained. The experimental results demonstrated that the developed 3D hydroforming technology can accurately control the material flow in the multi-stage forming of the multi-wave seal ring with small-diameter and ultrathin wall thickness. For the optimized parameter combination, the blank dimensions of deformation zone are 8 mm in the first step and 18 mm in the second step, while the pre-bulging pressure is 9 ~ 12 MPa and the maximum pressure is 100 MPa in the two steps.
Strength of nano-twinned gradient nano-grained copper: Molecular dynamic simulation
Authors: Tian Y , Chen F
Published: December 2022

Molecular dynamics simulations are performed to reveal the underlying deformation mechanisms of gradient nano-grained materials with different-sized twins. The results indicate that the critical twin boundary spacing where the strength begins to soften decreases and the maximum strength of the material increases with the declining of the gradient. Below the critical value, the plastic deformation mechanism is dominated by the partial dislocations paralleling to the twin boundary, but when the twin boundary spacing exceed the critical value, the dislocation moved by the way of intersecting to the twin boundary.
Dimensional optimization of variable thickness tube in T-shaped tube hydroforming using response surface methodology
Authors: Chen M T , Xiao X T , Tong J H , Guo H , Zhou F Q , Zhou F
Published: December 2022

In this work, a variable thickness tube blank geometry is proposed to be used in T-shaped tube hydroforming. The dimensions of the tube blank are optimized by the response surface method (RSM) linked with finite element simulation during T-shaped tube hydroforming. The influence of the wall thickness, angle and length of the tube blank are discussed on the thinning ratio and branch height. Multi-objective functions that relate objectives and design variables are formulated. Furthermore, the design variables having greatest impact on the objectives are obtained by sensitivity analysis. The optimal the geometric dimensions are determined within the given criterion by RSW and desirability approach. The optimized results have good agreement with the obtained results by finite element simulation and experiment.
Simulation of edge cracking using shear GTN damage model during hot plate rolling of magnesium alloys
Authors: Zhao C C , Liu J L , Li Z X , Jia R , Huang Z Q , Wang T
Published: December 2022

Edge cracks are a more prominent problem during the rolling process of magnesium alloy sheets. The hexagonal structure of magnesium alloys and the product defects caused by the second phase impurities mixed in the sheets are the main causes of edge cracking. Conventional hot-rolled edge cracking simulations can only characterize the edge damage of the sheets numerically, however, the actual crack morphology is ignored. In this paper, the Gurson-Tvergaard-Needleman (GTN) damage model coupled with a continuous medium shear damage model was developed for improving the applicability of the model at low-stress triaxiality. Powell’s “Dogleg” method was used in the numerical solution of the damage model instead of the traditional Newton-Raphson method and the Vumat subroutine was written for the finite element simulation by the stress return algorithm. The damage model parameters were calibrated by a shear specimen. The results showed a good agreement between the simulated crack morphology and the experiment.
Modelling in materials behavior of strength differential effect and yield locus evolution with non-associated flow rule
Authors: Zhou Y , Hu Q , Chen J
Published: December 2022

During numerical simulation of sheet metal forming, the accurate models to describe material yielding and hardening behavior by considering the anisotropy, non-uniform evolution of the yield surface and strength differential effect are vital to predict complicated deformation and forming defects such as fracture and springback. In the present work, a novel yield model with non-associated flow rule is proposed based on the frame of S-Y2009 criterion and coupled with normal stress components and the second deviatoric stress invariants, where the former is used to describe the anisotropy and non-uniform evolution of yield loci, and the later enables the description of SD effect. Different from some other models which identify the parameters via optimization algorithms, the proposed model adopts an analytical identification method from the stress-strain curve in various loading conditions, including uniaxial tension and compression along 0°, 45°, 90° to the rolling direction, and equi-biaxial tension and compression. The flexibility of the proposed model is validated for high strength steels, aluminum alloys and titanium alloys.
Central defects control of Ti-6Al-4V alloy with heavy section reduction during flat cross wedge rolling
Authors: Shi M J , Cheng M , Zhang S H , Tan H , Chen M , Petrenko V , Kozhevnikova G V
Published: December 2022

Cross wedge rolling (CWR) process is expected as an efficient and innovative preforming process for the forged aero-engine blades. But it is still a grand challenge to control the process defects and the performance of the rolled parts. According to the requirements of an aero-engine Ti-6Al-4V (TC4) blade billet with heavy section reduction up to 83%, flat CWR tools were designed and optimized by the thermal-mechanical coupling finite element (FE) method. The metal flow, damage evolution, and the distribution of stress and strain during the forming process were analysed. Then, the CWR experiments were carried out on IM500 flat CWR mill under different technological conditions. The obtained rolled parts were subjected to non-destructive testing (NDT), tension tests and microstructure analysis. The results showed that the central defects, such as micropores and voids, which seriously reduce mechanical properties, occurred in some of the rolled parts more or less. The volume of central defects was closely related to the initial rolling temperature of the billets. When the heated temperature of the TC4 billet was higher than 850°C, the target rolled part without central defects can be obtained. This research work can be a reference for the single-wedge CWR forming of titanium alloy with heavy section reduction, promoting the application of CWR in the aero-engine blade preforming process.
Effect of asymmetric rolling on microstructure and mechanical properties of aluminum matrix composites
Authors: Luo K G , Yu H L
Published: December 2022

The lightweight of structural materials was an important research focus for reduced energy consumption and transport efficiency. Aluminium matrix composites (AMCs) had the advantages of high specific strength and good wear resistance, so they were widely used in automobile, aerospace and other fields. At present, the deformation mechanism of AMCs reinforced by high-entropy alloy particles (HEAp) in asymmetric rolling was not clear. In this work, AMCs ingot reinforced with 6 wt% HEAp was prepared by stir casting process. Then the mechanical properties of HEAp/AMCs under different rolling processes were studied by asymmetric rolling (AR) and asymmetric cryorolling (ACR) processes. High-entropy alloy (HEA) had excellent strength and toughness, which imparted good deformation ability when added to AMCs as reinforcement. The microstructure of AMCs reinforced by HEAp was refined by ACR. At the same time, the HEAp/AMCs obtained by ACR displayed a higher ultimate tensile strength (UTS) than that obtained by AR. The study of ACR shows that AMCs reinforced with HEAp have good toughness. ACR can reduce the thickness of HEAp/AMCs to a greater extent so as to produce AMCs strip with excellent mechanical properties.
Effect of surface roughness on strain distribution during bending
Authors: Kaijalainen A , Pokka A-P , Jaskari M , Kömi J
Published: December 2022

The limited formability of ultra-high strength steels (UHSS) poses some challenges for the bending process in the form of strain localisation, surface defects and pseudo-polygonal “nut-like” shape of the bend. Bendability is well known to be affected by surface quality, and especially shot blasting. Therefore, in this study, the effect of surface roughness on bendability of UHSS grade is investigated with 3-point bending tests, utilising Digital Image Correlation (DIC) for measuring the strain distributions on the outer curvature. Investigated bending samples of 4 mm thick commercial martensitic were tested in different surface conditions: As-rolled (with scale), “lightly” shot blasted (SB I), “roughly” shot blasted (SB II), dry electropolished (As-rolled P) and a combination of “rough” shot blasting and dry electropolishing (SB II P). Shot blasting increased the surface roughness and subsurface hardness. Utilizing a commercial dry electropolishing process reduced the surface roughness, although this also had major effect on the hardness. Bending results showed that coarser surface roughness decreased the bending capacity, i.e. reduced maximum bending angle and critical strain. A strong correlation between surface roughness (with Rv: the maximum valley depth below the mean surface) and critical bending angle was found, likewise with the subsurface hardness and critical bending angle.
Simulation study on the texture evolution mechanism of magnesium alloy cylindrical parts with inner ribs during hot power spinning
Authors: Yuan S , Xia Q X , Cheng X Q , Xiao G F
Published: December 2022

Grasping the mechanism of texture evolution during hot power spinning of magnesium alloy cylindrical parts with inner ribs, which have the dual lightweight advantages of material and structure, can provide a theoretical basis for texture regulation in the preparation of high-performance magnesium alloys. Based on the crystal plastic finite element method, the macro-meso coupled model was constructed and the simulation study of magnesium alloy cylindrical parts with inner ribs during hot power spinning was carried out. The texture evolution mechanism at the position of cylindrical wall (CW) and inner rib (IR) was revealed by tracking the change of grain orientation and the analysis of Schmid factor (SF). The results show that the c-axis of grains of magnesium alloy extruded blank gradually deflects from parallel to tangential direction (TD) to parallel to radial direction (RD). Under the action of radial compressive stress, the formation of texture at CW is attributed to the orientation deflection of grains which have larger SF of basal slip system and locate in the region of the maximum texture strength of blank, while the origin of the texture at IR mainly comes from the orientation deflection of grains with a smaller (0.1~0.2) SF of basal slip system.
An application exploration of flexible skew rolling a rail car axle
Authors: Lin L F , Wang B Y , Liu J P , Zheng Z H , Zhu C B
Published: December 2022

This paper presents a new method in axles manufacturing called flexible skew rolling (FSR) process and its application exploration was conducted in laboratory by producing a rail car axle. The FSR rolling path for rail car axle was designed and calculated and then programmed into the FSR mill. The material of the rolled shafts was LZ50 steel and its diameter is 60 mm. By conducting experiments, a rail car axle with multistep was rolled successfully. There is no central crack in the rolled piece, and the outer grain is refined into 22.23μm from 76.45μm and the inner grain is refined into 38.94 μm from 83.47 μm. This study results verified that the FSR process is positive and the rail car axle can be rolled by FSR process.
Forming limit of AZ31B magnesium alloy under in-plane complex biaxial loading paths with cruciform specimens
Authors: Wang H B , Liu Z C , Deng X Z
Published: December 2022

This paper focused on the forming limit curves (FLC) of the AZ31B magnesium alloy sheet metal under different complex loading paths in-plane. Compared with simple loading paths, the study of forming limit of sheet metal under complex loading paths was more practical. In this study, biaxial tensile test of the cruciform specimen was utilized to acquire the FLC after the cruciform specimen was subjected to uniaxial pre-tensile process along rolling direction, which experimentally characterize the forming limits under different pre-strain values of 1.15%, 2.34%, 4.0%, and 5.4%. Subsequently, based on the constitutive model, Hill48 yield criterion and shear failure criterion, the theoretical FLCs of AZ31B magnesium alloy sheet metal was be calculated. Meanwhile, the normal biaxial tensile tests were also simulated by Abaqus to obtain the limit strains by Finite Element Analysis (FEA). Extracting limit strains from the fracture region in FEA model when the first derivative of the strain difference with respect to time reached the maximum value between the first principal strain of necked element and the first principal strain of the element adjacent to the necked zone. As a result, the experimental FLCs was qualitatively consistent with the result of theoretical model and FEA model. In addition, the FLCs of AZ31B magnesium alloy sheet moved to the upper left of forming limit diagram with the increase of the pre-strain, which indicated that the pre-strain process along the rolling direction could significantly improve the formability of the sheet metal.
Numerical and experimental investigation of the thermal behavior and microstructure of wire arc additive manufactured 316L stainless steel straight wall part
Authors: Di Y Y , Zheng Z Z , Pang S Y , Li J J
Published: December 2022

The heat transfer behavior during wire arc additive manufacturing is closely related to the dimensional accuracy and performance of the formed part. To investigate the thermal behavior of stainless steel 316L straight wall part fabricated by the wire arc additive manufacturing process, a three-dimensional transient finite element model is established based on the double elliptic heat source model. At the same time, the temperature measurement experiment on the characteristic position of the substrate is carried out. The thermal cycle curve obtained by the finite element model is in good agreement with the measured result. By analyzing the simulation results, the finite element model established can effectively reveal the thermal behaviors such as melting, solidification, heat accumulation and remelting during the forming process of the straight wall part. In addition, the solidification parameters obtained by the model are correlated with the microstructure. High G/R induces the production of cellular crystals and columnar dendrites, on the contrary, the formation of equiaxial crystals, which provide guidance for the prediction of the morphology of the microstructure.
Multi-scale modelling of deformation heterogeneities in explosively welded layered sheets
Authors: Mojzeszko M , Perzynski K , Madej L , Majta J
Published: December 2022

A multi-scale numerical investigation of local heterogeneities in the strain and stress fields occurring during forming of explosively welded layered metallic sheets is the main goal of the research. Explosive welding is a complex process involving various phenomena occurring in materials during an impact at high velocities and pressures, especially at the interfaces of colliding metals. As a result, the interface of the layered metallic sheets is often highly heterogeneous at the microscale level, what directly affects the sheet behaviour under subsequent forming conditions. To investigate this issue, the mesh-free numerical model of the explosive welding process is used first to recreate the characteristic features of the interface morphology. Various detonation velocities are used to provide diversified morphological features at the interface. Obtained results are then used as input data to develop the concurrent multi-scale finite element model of material behaviour under deformation conditions. The multi-scale modelling concept with explicit representation of the interface region is used. The highly refined heterogeneous FE mesh was generated in the interface region to capture local heterogeneities occurring at the microscale. Particular attention is put on numerical investigation of an influence of interface morphology in the welding zone on the development of the stress localisation that may directly lead to fracture initiation during forming.
Influence of mechanical properties and alloying elements of low carbon steels on fine blanking and heat treatment processes response
Authors: Chiavazza T , Marnier M , Achille A , Woimbee V , Even D , Colasse C , Osmond D , Eve S , Hug E
Published: December 2022

The effect of the negative clearances between punch and die of a flange with different fine blanking half-cutting depths was investigated for two low carbon steels with various elongation rates, C18E (0.18%C) and 20MnB5 steels (0.2%C, with upper mechanical properties than the carbon steel), industrially used for forming car seat parts. A specific tool adaptable on a tensile machine was built to determine the force needed to fine blank a simple geometry, in the objective to further transpose the obtained results to the complex geometry of industrial parts. Heat treatment was carried out to optimize the microstructure, hardness and dimensional modifications for the combination material/clearance/half-cutting height tested. Increasing the elongation rate of the raw material allows to reach a better formability and reduces the force needed to create a given geometry, but cracks were detected for the extreme deformation rate. Moreover, after fine blanking and heat treatment operations, different microstructures were observed according to the material grade, stable for low alloy 20MnB5 steels (martensitic microstructure) while non reproducible for the low carbon steel (mix of ferrite, bainite and martensite).
Investigation of the influence of material and sheet thickness on a three-stage process chain for cold forming of micro gears with a module of 0.1 mm
Authors: Leicht M , Rohrmoser A , Kraus M , Merklein M
Published: December 2022

In many industries, there is a trend towards miniaturization of technical components, such as drive systems, which enable the solution of high-precision positioning tasks because of their low volume and high dynamics. Geared micro parts are currently mainly produced by cutting and LIGA processes, but in mass production cold forming offers ecological and economic benefits. However, the cold forming of micro gears is restricted to a lower module limit of m = 0.2 mm due to high tool stresses, size effects and handling difficulties. To solve these challenges, in this contribution a three-stage forming process chain for the manufacturing micro gears (m = 0.1 mm) is investigated. In the first stage, a pin as wheel blank is extruded from sheet metal, which is geared subsequently by lateral extrusion. Finally, the micro gear is separated from sheet by shear cutting. The aim of this study is to demonstrate the applicability of the process chain for the materials Cu-OFE and CuZn30. In addition, the influence of the sheet thickness, which has a major impact on the forming process and the material efficiency, is analyzed. The geometrical and mechanical component properties as well as the machine data are evaluated to assess the variables.
Forgeability characterization of multi-material based functionally graded materials manufactured through friction stir consolidation
Authors: Latif A , Ingarao G , Buffa G , Fratini L
Published: December 2022

Solid state recycling allows direct recycling of metal chips into semi-finished products. This process category proved to lower the environmental impact of metals recycling. Friction stir consolidation (FSC) is a new solid-state technique taking advantage of friction heat generation and severe plastic deformation to consolidate chips into billets. The new frontier of FSC process could be its evolution from recycling techniques towards the concept of upcycling technique: reuse (discarded objects or material) in such a way as to create a product of higher quality or value than the original. The authors have recently successfully applied FSC for producing multi-material based functionally graded materials (FGM). In this paper, the forgeability of the billet consolidated out of two dissimilar aluminium alloys AA 7075 and AA 2011-T3 chips, was analyzed. A proper forging test was designed, and mechanical and metallurgical properties of the forged parts were assessed through Vickers hardness measurements.
Experimental study on friction stir modification of LA103Z Mg-Li alloy
Authors: Chen F J , Zhai J Q , Guan Y J , Li Y , Chen H , Hu K , Lin J , Ren Q H , Li X J
Published: December 2022

Friction stir processing (FSP) is a method to produce severe plastic deformation (SPD) of materials, which can well improve and optimize the microstructure and mechanical properties of Mg-Li alloy. In this paper, the FSP experiment of LA103Z Mg-Li alloy was conducted, and the influence of process parameters on the microstructure, tensile strength, elongation after fracture and fracture morphology of the material was studied. The microstructure of the Mg-Li alloy after FSP was significantly refined. With the increasing rotational speed of the stirring head, the grain boundaries became clearer and more distinguishable, and the low angle grain boundaries transformed into the high angle grain boundaries. With the increasing feed speed of the stirring head, the grain refinement became more pronounced, and the dispersion of α-Mg phase in the stir zone became more uniform and distributed at the grain boundaries. When the rotational speed and the feed speed of the stirring head were 800-1000 r/min and 100-200 mm/min respectively, the comprehensive performance of the Mg-Li alloy plate after FSP was expected to be optimal.
A unified model to predict the hot stamping and subsequent stress-relaxation process of a Ti-6Al-4V alloy
Authors: Chen H S , Du L H , Khan M Shahzad , Zhang T , Mu Y H , Zhang Y , Li Y
Published: December 2022

Isothermal hot stamping process, which is composed of stamping and subsequent stress-relaxation steps, is an important technology to form complex thin-walled titanium components in the aerospace industry. It is a key issue to enable the accurate simulations of these two steps simultaneously for the process design and optimization. In this study, a unified constitutive model connecting both the plastic flow behaviour in stamping and the stress-relaxation behaviour in subsequent step is developed by considering the continuous evolution of key microstructures, i.e., dislocation density, in the whole process. A series of basic mechanical tests, including tensile and stress-relaxation tests, of a typical titanium alloy Ti-6Al-4V at 750°C was performed to calibrate the developed model. The unified model was then implemented into the commercial software ABAQUS via the VUMAT subroutine, and simulations of the complete hot stamping process were done, including stamping, stress-relaxation and final springback. In addition, a typical curve-shape component was hot-stamped at 750°C and stress-relaxation for 5 minutes was performed. The predicted result from the developed constitutive model and FE model shows a good agreement of the springback with the corresponding experimental result, verifying the effectiveness of the developed model for the further applications in hot stamping process design and optimization in the industry.
Crystallographic aspect of shear bands formation in pure iron deformed at high strain rates
Authors: Mania I , Paul H , Chulist R , Petrzak P , Prażmowski M
Published: December 2022

In this paper results on shear bands developed in pure iron are presented. The main focus was put on microstructural characterization and crystal lattice rotation in sheared regions. The hat-shaped samples were deformed at a high strain rate of 560 s−1 using a drop-hammer. The microstructure of deformed specimen was investigated by optical microscopy and scanning electron microscopy equipped with a high-resolution electron backscattered diffraction facility. The changes of mechanical properties in the band area and neighbouring matrix were investigated using nano-indentation test. This paper clearly shows that initial stages of shear bands formation are associated with the formation of kink-type bands. The orientation maps revealed the crystallographic determination of the shear band formation. During deformation in each grain located within the sheared region, one of the {110}-type planes situate along the macro-shear band plane and <111> direction situates along the shear direction. In consequence, the formation of specific texture components within the shear band region was observed, different from texture observed in deformed matrix. In micro-scale no effects of dynamic recrystallization were observed. Nano-hardness tests indicated that notable increase of strain hardening is related to the strain localization in narrow shear band’ regions, while the matrix undergoes almost no deformation.