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The forming quality of Fiber metal laminates (FMLs) heavily depends on the material properties, fiber placing angles, blank holder force, and other process parameters. In some circumstances, the numerical perturbation of the key parameters has a potential impact on the mechanical properties of final products. To efficiently design a set of available system parameters to ensure the forming quality, a manifold learning-assisted approximate Bayesian computation (ABC) method is proposed to identify system parameters with uncertainties. In this study, the nonlinear manifold learning approach is employed to extract the feature vector of physical field information of sheet metal and composite core after hot forming. Furthermore, the mapping transformation of system parameters based on different modeling techniques is performed to shorten the time of obtaining feature vectors of new samples. The nested sampling method involving the wavelet mutation strategy is proposed to improve the sampling efficiency of the posterior distribution of system parameters while the tolerance criterion is guaranteed. Two hot stamp-forming cases are employed to validate the feasibility of the proposed approach. The numerical results show that the proposed method is effective in obtaining the system parameters necessary for achieving the high-quality forming of FMLs. [ABSTRACT FROM AUTHOR]

Increasing the service life and process reliability of systems plays an important role in terms of sustainable and economical production. Especially in the field of energy-intensive bulk forming, low scrap rates and long tool lifetimes are business critical. This article describes a modular method for AI-supported process monitoring during hot forming within a screw press. With this method, the following deviations can be detected in an integrated process: the height of the semi-finished product, the positions of the die and the position of the semi-finished product. The method was developed using the CRISP-DM standard. A modular sensor concept was developed that can be used for different screw presses and dies. Subsequently a hot forming-optimized test plan was developed to examine individual and overlapping process deviations. By applying various methods of artificial intelligence, a method for process-integrated detection of process deviations was developed. The results of the investigation show the potential of the developed method and offer starting points for the investigation of further process parameters. [ABSTRACT FROM AUTHOR]

A novel integrated constitutive equation of the flow curve for Ti--6Al--4V alloys is proposed by incorporating the effects of phase fraction in the hot-forging temperature range. The flow curve was obtained using hot-compression tests in the temperature range of 750-1 050°C and strain rate range of 1-25 s-1. The effects of friction and deformation heat generated during compression were corrected using the inverse analysis method to identify the ideal uniaxial flow curve. The obtained stress parameters were satisfactorily regressed using the rule of mixtures on the α and β phases considering changes in the phase fraction. The integrated flow curve equation incorporating the rule of mixtures of the two phases effectively expressed the flow curve throughout the investigated temperature range. The internal microstructural observation showed that the continuous dynamic recrystallization of the α phase is dominant in the α+ β two-phase region, while the deformation of the β phase becomes dominant just below the β transus. The constitutive equation presented here is in good agreement with the temperature dependence of the microstructure. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To accurately predict the behavior and mechanical damage of sheet metal during hot forming process, the use of advanced thermomechanical modeling and precise identification of the constitutive parameter are required. This paper proposes a novel identification approach for constitutive parameters that relies on multiple regression and the shape index of experimental data curves. This approach is used to determine the material constants associated with the Johnson-Cook material and failure models for steel and aluminum sheets. Therefore, the obtained results approve the applicability and high accuracy of the identification procedure for the damage and the constitutive parameters of sheet metal, which allows for substantial time savings. Furthermore, to evaluate the formability of sheet metal, experimental forming tests at various temperatures were conducted. The identification process enhances the prediction of forming results, as shown by the fact that the numerical simulation of Erichsen and square die hydroforming tests using identified Johnson-Cook parameters agreed with the results of these tests carried out at different forming conditions. Moreover, the thickness measurement shows the ability of the developed model to properly predict the thickness of deformed shapes.

Hot deformation and in-die quenching of aluminum components for the automotive industry is a cost and energy efficient technique that has been developed and thoroughly evaluated in recent years. The performance of this process is considered higher when compared to traditional cold metal forming due to shorter process times, low-cost machinery, and a high level of structural integrity in fabricated parts. The work presented in this paper provides several approaches for the formability of age hardenable 6xxx alloy sheets when forming at different temperatures. Warm tensile testing and formability cup testing were carried out to investigate the alloy formability at different temperatures. The results indicate that the formability of candidate alloys is not significantly affected by deformation temperatures or conditions, which provides great freedom when designing an automated production process with high productivity and minimal environmental impact. The candidate alloy can be deep drawn without severe thinning at the whole temperature range, from room temperature (RT) to solutionizing temperature. [ABSTRACT FROM AUTHOR]

The temperature of a forming region has a gradient distribution characteristic in the belt heating incremental sheet forming process, in which the relation between the heating power and the temperature distribution is ambiguous in the pre-heating stage. The setup of the heating power is therefore challenging, and the whole forming efficiency might decrease due to the above issue. Therefore, this paper proposes a belt heating method for electric conduction heating and presents a temperature calculation model for the forming region of the plate in the preheating state based on the heat conduction model. The calculated accuracy of the model is analysed through physical experiments, and the thermal transfer efficiency of heating tubes is analysed in detail. Based on the result, the thermal transfer efficiency value for heating tubes is determined to improve the accuracy of the suggested model. In addition, the effect of the model slope on the calculated result is further analysed, and the setting method of the slope value for the model is proposed according to different accuracy requirements. [ABSTRACT FROM AUTHOR]

The hot forming process allows to produce safety-relevant structural components in the automotive industry with strengths of 1500 MPa and higher. Generally, high strengths make material sensitive to hydrogen embrittlement. The heat treatment in the hot forming process chain is a potential source of diffusible hydrogen for hot-dipped aluminum-silicon coated boron-manganese steels. In the present work, the influence of different process gases and furnace dwell times during the heat treatment was investigated. Humidified process gases such as synthetic air, nitrogen, oxygen and carbon dioxide were used. The results of the thermal desorption mass spectrometry (TDMS) revealed a more pronounced hydrogen uptake for nitrogen and carbon dioxide gas atmosphere than for synthetic air and oxygen. Furthermore, different material conditions were investigated regarding their sensitivity to hydrogen absorption. The flat-rolled material tends to suffer a higher hydrogen absorption compared to the reference material when using humidified process gases. Materials being pretreated with dry synthetic air point at a relation between the duration time of the pretreatment and the content of absorbed hydrogen.

This paper presents a study of temperature conditions for the homogenization of a cast high-strength ZK60 alloy belonging to the Mg-Zn-Zr group of magnesium alloys. On the basis of a literature review, two-stage homogenization conditions were selected to improve the forgeability of the ZK60 casting. The effectiveness of this treatment was evaluated experimentally on the basis of structure and hardness tests and was found to be satisfactory. Plastometric tests were carried out for the samples made from the ingots after homogenization. These tests were performed in a compression test in hot forming conditions at three temperatures (350 ºC, 400 ºC and 450 ºC) and four strain rates (0,01; 0,1; 1,0 and 10 s-1). The determined flow curves will be used to develop a material model of the cast magnesium alloy ZK60 for numerical simulations.

The Collaborative Research Center 1153 is investigating an innovative process chain for the production of hybrid components. The hybrid workpieces are first joined and then formed by cross-wedge rolling. Pinion shafts were manufactured to investigate the behavior of the joining zone under increased complexity of the forming process. For this purpose, six types of workpieces produced by three types of joining processes were formed into pinion shafts. The reference process provides a shaft with a smooth bearing seat. It was found that the increased complexity did not present any challenges compared to the reference processes. A near-net shape geometry was achieved for the pinions made of steel. [ABSTRACT FROM AUTHOR]

Bi-axial state is the dominant stress state experienced by the sheet metal during various forming processes, which requires a thorough understanding and modelling for process designs. In this paper, effects of equal bi-axial stress-state on the hot deformation behavior of titanium alloys are thoroughly investigated using hot bulging tests, and is further compared to the uniaxial stress state. Firstly, a specific hot bulging test device enabling a uniform temperature field and constant control of strain rate was established, using which, systematic hot bulging tests at various temperatures (750–850 °C) and strain rates (0.001–0.1 s−1) of the near-alpha phase TA32 sheets were conducted to determine the hot equal bi-axial bulging behavior. Based on the testing data of force and geometry variations of bulged domes, the equivalent stress–strain curves were calculated. Secondly, a plane-stress visco-plastic plane-stress model of near-alpha TA32 sheets was developed for the first time, enabling both the uniaxial and biaxial flow behavior and forming limits to be precisely predicted. The prediction accuracies for uniaxial and biaxial cases are 93.5% and 89%, respectively. In the end, the uniform deformation resulting from the strain and strain rate hardening was determined, which contributes to the understanding of the stress-state effect on hardening preliminarily. The plane stress visco-plastic model provides an efficient and reliable material model for finite element (FE) simulations of hot forming titanium alloy sheets. [ABSTRACT FROM AUTHOR]

Since the hot forming of TC4 alloy after diffusion bonding has extensive applications in aerospace and medical industries, it is practically significant to explore the influence of diffusion bonding on the alloy's hot formability and identify the optimal forming parameters. Therefore, dual-stage diffusion bonding of aviation grade TC4 is carried out firstly at 900 °C for 1 h and then at 930 °C for 2 h under 2-MPa normal pressure in 5.0 × 10 - 3 -Pa vacuum atmosphere. Another block of the as-received alloy is subjected to the same thermal loading as the diffusion bonding process. The diffusion-bonded and heat-treated alloys are then subjected to uniaxial tensile tests at 750 - 900 °C and 0.0001 - 0.1 s - 1 . Based on the tensile test data, the constitutive and dynamic material models are developed to investigate diffusion bonding effects on the alloy's hot forming behavior and identify optimal forming conditions. The developed constitutive model showed good predictability. The apparent activation energy of diffusion bonded (440 - 510 kJ · mole - 1 ) and heat-treated (400 kJ · mole - 1 ) alloys indicated that dynamic recrystallization and recovery are the primary deformation mechanisms. The processing maps revealed that diffusion bonding expanded the instability domain and lowered the dissipation efficiency, limiting the safe working conditions of the alloy. The analysis of deformed microstructure validated the findings of processing maps. The optimal processing conditions of 800 °C /0.0001 s–1 and 850 °C /0.0001 s–1 are discovered for diffusion-bonded and heat-treated alloys, respectively. [ABSTRACT FROM AUTHOR]

For conventional sheet metal forming at room temperature, numerous tribometers have been developed in the 20th century. At the present state of the art, there are some challenges for tribometry in warm and hot forming processes of high‐strength aluminum (e.g., EN AW‐7075). Especially for nonisothermal processes with heated sheets and cooled dies, the tribological design is a major challenge, which needs to be addressed by investigations with adapted tribometers. Herein, the transferability of friction and wear behavior of three different lubricants and temperatures is investigated. Therefore, tribometer test results are compared with real forming trials in combination with thermomechanical finite element simulations. Both the behavior of different lubricant types and the characteristics of tool lubrication in sheet metal forming are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a study of temperature conditions for the homogenization of a cast high-strength ZK60 alloy belonging to the Mg-Zn-Zr group of magnesium alloys. On the basis of a literature review, two-stage homogenization conditions were selected to improve the forgeability of the ZK60 casting. The effectiveness of this treatment was evaluated experimentally on the basis of structure and hardness tests and was found to be satisfactory. Plastometric tests were carried out for the samples made from the ingots after homogenization. These tests were performed in a compression test in hot forming conditions at three temperatures (350 °C, 400 °C and 450 °C) and four strain rates (0,01; 0,1; 1,0 and 10 s-1). The determined flow curves will be used to develop a material model of the cast magnesium alloy ZK60 for numerical simulations. [ABSTRACT FROM AUTHOR]

Many modern automotive and aerospace components are heat-formed at temperatures up to 900 °C. Due to the high tool temperature, insulations are employed to reduce the heat loss and the energy consumption of the process. However, current insulation materials for the force flow of these processes still require active counter-cooling. In this study, the performance of a novel hybrid structure with improved insulation capability for such applications was investigated. It consisted of an outer frame made of an oxide fiber composite (OFC) and a paper-based ceramic (PBC) as a filler. The mechanical and thermal properties for both materials were determined and implemented in a finite element model (FEM) to numerically design the layout of a hybrid structure. Experimental load tests in process-oriented conditions validated the simulation results. The hybrid insulation appears promising, as mechanical stability and good insulation capabilities were confirmed.

In order to optimize the heat treatment process following hot induction forming, our study focused on investigating the impact of quenching and tempering temperature on the mechanical properties and microstructure of ASTM A860 Gr WPHY 65 hot formed 30-inch elbow steel, which is utilized in high strength low alloy (HSLA) pipelines for oil and gas applications. The desired properties for these steels include high mechanical strength, toughness, ductility, and weldability. Our experimental approach involved varying the soaking temperatures at 960 °C, 1000 °C, and 1050 °C, and subsequently cooling the samples in water at 20 °C, followed by tempering at 670 °C and 700 °C. Through the use of experimental design techniques, we determined the optimal heat treatment parameters. The results indicate that soaking at 1050 °C and tempering at 700 °C were the most effective treatment conditions in terms of mechanical strength. Furthermore, microstructural analysis revealed that heat treatment not only restored the microscopic structure of the base material, but also resulted in finer grain sizes.

Hot forming processes of complex parts with small cavities demand high-performance tools made of hardened steels. Their surface can be tribologically modified in order to control the material flow for improving the mold filling of functional elements. Surface structuring here offers great potential for adjusting the frictional properties and thus controlling the material flow in forming processes. In this study, high-feed milling (HFM) of surface structures in hot work tool steel (HWS) components is investigated. The process performance was determined by cutting force measurements and tool life tests. The achievable surface topography was measured and evaluated in terms of structure quality and roughness parameters, and friction properties were derived based on the results. In a hot ring compression test, the influence of certain structure variants on the material flow was analyzed. The results conclude that HFM is a suitable process for structuring HWS components with constant structure quality and low tool wear. In addition, a variety of structures showed significant influence on the hot ring compression test. This indicates a relevant potential of HFM for the modification of hardened tool surfaces to improve the performance of hot forming processes and increase the manufactural quality and productivity. [ABSTRACT FROM AUTHOR]

Hot forming process has been used more and more frequently in the production of body structures of modern ultralight passenger cars for several years. This, unlike the commonly used cold stamping, is a complicated process, combining heat treatment and plastic-forming methods. For this reason, permanent control at each stage is required. This includes, among others, measurement of the blank thickness, monitoring its heating process in the suitable atmosphere in the furnace, control of the forming process itself, measurement of shape-dimensional accuracy as well as mechanical parameters of the finished drawpiece. This paper discusses the method of controlling the values of production parameters during the hot stamping process of a selected drawpiece. For this purpose, digital twins of the production line and the stamping process, made in accordance with the assumptions of Industry 4.0, have been used. Individual components of the production line with sensors for monitoring process parameters have been shown. The system's response to emerging threats has also been described. The correctness of the adopted values is confirmed via tests of mechanical properties and the assessment of the shape-dimensional accuracy of a drawpiece test series. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V alloy is often preferred for high-performance components such as aerospace components due to its superior material properties and thermal resistance. In order to produce these components in the desired geometry, it is very important to determine the high-temperature thermomechanical properties of Ti-6Al-4V. In order to define these properties, uniaxial tensile tests at strain rates of 0.001, 0.01 and 0.1 s−1 at 700, 750 and 800 °C were applied in this study. In tests performed at a strain rate of 0.001 s−1 at 800 °C, an elongation at break above 0.8 representing a dominant ductile behavior is observed. It is clearly demonstrated that the initial 17.32% β phase reaches 31.02% at 800 °C, and the α grain size increases with temperature. Existence of dimples and voids in the fracture surfaces are an indicator of increased ductility behavior. In addition to the Modified Johnson–Cook model, which is widely used for modeling flow stress, the use of the extended Ludwik equation is suggested in this study. According to the correlation coefficient (R), it is claimed that the Extended Ludwik model is a more suitable approach for modeling the mechanical behavior for the studied forming temperature range. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hardening is the core factor to determine deformation uniformity in sheet metal forming. Hot deformation of titanium alloy sheets encounters the coupled effects of strain hardening, strain rate hardening and softening, which makes the determination of forming parameters aiming for an enhanced hardening very difficult in practical processes. This paper presents a new model to quantify the hardening of Ti-6Al-4 V titanium alloy sheets under hot forming conditions based on the underlying correlation between uniform strain and hardening. Firstly, to precisely determine hot deformation characteristics of titanium alloy sheets, hot tensile uniaxial tests using Gleeble systems at various strain rates of 0.01–1 s−1 and temperatures of 973–1123 K were performed systematically. A newly developed volume-based correction method for stress–strain curves of Gleeble thermo-mechanical testing was proposed to eliminate the damaging effect of temperature gradients on strain calculations, which enables the strain hardening, strain rate hardening and softening to be determined precisely. Then, a simple unified formula of hardening components (n, m and s) was proposed to predict the achievable uniform strain at certain conditions efficiently. Using which, occupation of each hardening can be quantified and compared to facilitate the determination of process parameters. Finally, a phenomenological model based on the hardening and softening components was developed to predict the hot flow behaviour. The proposed quantitative model can provide an efficient and useful approach for process designers to design process parameters driven by the objective of enhancing hardening to maximize uniform deformation during hot forming of titanium alloy sheets. [ABSTRACT FROM AUTHOR]

In this paper, the conventional hot forming and hybrid quenching hot forming processes of Al-Si-coated 22MnB5 steel sheet were investigated and compared at 0.5 s-15 s holding times in the press tool related to the mechanical properties, microstructure, and dimensional accuracy. The conventional hot forming method is classified as a direct method and an indirect method. Both methods have limitations due to processing time and cooling of the press tool. To speed up the process, an alternative cooling method based on spray or jet cooling was used outside of the die tool. The hybrid quenching method involves hot forming and spray cooling process. This method, using spray parameters, provides more effective control in mechanical properties and microstructure compared to the conventional method by using spray parameters. Vickers hardness tests and tensile tests were carried out to compare mechanical properties. Changes in the microstructure of the materials were investigated using an optical microscope. The results show that spray cooling can be used as part of quenching in the hot forming process by reducing the holding time in the press tool by 97%. However, the microstructure, mechanical properties, and geometry deviations of the stamped parts are still below tolerances after the hybrid quenching hot forming process. The use of the hybrid quenching method with multi-point nozzles in the hot forming process resulted in sheet hardness up to 470 HV1 and 8% elongation with tensile strength of 1500 MPa. [ABSTRACT FROM AUTHOR]

This paper presents a systematic study of heating effects on the hot deformation and microstructure of dual-phase titanium alloy Ti-6Al-4V (TC4) under hot forming conditions. Firstly, hot flow behaviors of TC4 were characterized by conducting tensile tests at different heating temperatures ranging from 850 °C to 950 °C and heating rates ranging from 1 to 100 °C/s. Microstructure analysis, including phase and grain size, was carried out under the different heating conditions using SEM and EBSD. The results showed that when the heating temperature was lower than 900 °C, a lower heating rate could promote a larger degree of phase transformation from α to β, thus reducing the flow stress and improving the ductility. When the temperature reached 950 °C, a large heating rate effectively inhibited the grain growth and enhanced the formability. Subsequently, according to the mechanism of phase transformation during heating, a phenomenological phase model was established to predict the evolution of the phase volume fraction at different heating parameters with an error of 5.17%. Finally, a specific resistance heating device incorporated with an air-cooling set-up was designed and manufactured to deform TC4 at different heating parameters to determine its post-form strength. Particularly, the yield strength at the temperature range from 800 °C to 900 °C and the heating rate range from 30 to 100 °C/s were obtained. The results showed that the yield strength generally increased with the increase of heating temperature and the decrease of heating rate, which was believed to be dominated by the phase transformation. [ABSTRACT FROM AUTHOR]

AA6010 in the F temper was investigated using a Gleeble 3800 test rig across a range of temperatures (350–550 °C) and strain rates (1 × 10−1 s−1 1 × 101 s−1) to identify optimal forming conditions. Post-forming electron back-scattered diffraction analysis was conducted to identify the mechanisms responsible for the material formability. Optimal forming conditions were observed to be 500 °C and a strain rate of 1 × 10−1 s−1, with clear evidence of dynamic recrystallisation observed, this being the dominant mechanism responsible for the increased formability. Peak yield strength of 335 MPa was achieved using a rapid aging treatment of 205 °C for one hour. [ABSTRACT FROM AUTHOR]

Hot deformation and in-die quenching of aluminum components for the automotive industry is a cost and energy efficient technique that has been developed and thoroughly evaluated in recent years. The performance of this process is considered higher when compared to traditional cold metal forming due to shorter process times, low-cost machinery, and a high level of structural integrity in fabricated parts. The work presented in this paper provides several approaches for the formability of age hardenable 6xxx alloy sheets when forming at different temperatures. Warm tensile testing and formability cup testing were carried out to investigate the alloy formability at different temperatures. The results indicate that the formability of candidate alloys is not significantly affected by deformation temperatures or conditions, which provides great freedom when designing an automated production process with high productivity and minimal environmental impact. The candidate alloy can be deep drawn without severe thinning at the whole temperature range, from room temperature (RT) to solutionizing temperature.

The combination of complex geometry and martensitic microstructure, characterized by ultrahigh strength and hardness, can be obtained in a single hot stamping process. However, this technology requires a multifaceted approach, allowing for an effective and efficient design process that will ensure the elements with the desired properties and shape are produced because of the high tool cost. This paper presents a comprehensive case study of the design process, simulation and experimental evaluation of the hot forming of an automotive door beam. The U-shaped beam designed with CAD was analyzed using the finite element method in the Autoform v.10 software. The modeling process included: a shape definition of the flat blank; a FEM analysis and design of the die, punches, and clamps; and a forming and quenching simulation. The results covered visualization of the forming and quenching stages for different variables including a forming limit diagram; a distribution of the drawpiece thinning; and a diagram showing the hardness of the drawpiece and its microstructure. Based on the results, a full-size tool for hot stamping was first modeled in the CAD and next manufactured. The tool was used to produce an initial sample series that was used to investigate the conditions for continuous use of the tool. One of the produced hot-stamped products was investigated for its hardness and microstructure, which exhibited a beneficial and fully martensitic microstructure with high hardness of above 400 HV1. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization is one of the main phenomena responsible for microstructure evolution during hot forming. Consequently, obtaining a better understanding of dynamic recrystallization mechanisms and being able to predict them is crucial. This paper proposes a full-field numerical framework to predict the evolution of subgrain structures upon grain growth, continuous dynamic recrystallization, and post-dynamic recrystallization. To be able to consider a subgrain structure, two strategies are proposed. One relies on a two-step tessellation algorithm to generate a fully substructured microstructure. The second strategy enables for the simulation of the formation of new subgrains during hot deformation. Using these tools, the grain growth of a fully substructured microstructure is modeled. The influence of microstructure topology, subgrain parameters, and some remaining stored energy due to plastic deformation is discussed. The results highlight that the selective growth of a limited number of subgrains is observed only when mobility is a sigmoidal function of disorientation. The recrystallization kinetics predicted with different criteria for discrimination of recrystallized grains are quantitatively compared. Finally, the ability of the framework to model continuous dynamic and post-dynamic recrystallization is assessed upon a case study representative of the hot extrusion of a zircaloy-4 billet ( T = 650 °C ; ε ˙ = 1.0 s − 1 ; ε f = 1.35 ). The influence of grain boundary properties and nucleation rules are quantified to evaluate the model sensitivity and suitability. Application of these numerical tools to other thermomechanical conditions and microstructures will be presented in an upcoming article. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel 316 L grade is a material having extraordinary mechanical properties, low cost and easily available. This is the reason it was used in various industrial and nuclear applications. In the present work, ASS 316L nakazima specimens are stretched under hot forming conditions (750°C, 825°C and 900°C) at a constant strain rate (0.1s-1) along with three different orientations. These six types of nakazima specimens were used to know the formability behaviour of the material with the help of forming limit diagrams (FLD) obtained by the stretch forming process. A smaller change in Punch load and an increase in displacement were observed, which indicates the formability improvement of ASS 316L sheet metal with the increase in temperature. In addition, ABAQUS 6.13 computer code was applied for the prediction of formability from 750°C to 900°C. To improve the accuracy of the simulation, a number of integration points were accrued within the thickness direction, limiting dome height (LDH). The ductile fracture was observed from SEM images for all the temperatures. A close agreement was found between experimental and simulated results. [ABSTRACT FROM AUTHOR]

This paper presents a detailed review of incremental sheet forming (ISF). The first part presents an introduction to the ISF technology based on the working principles, different variants of the technology, process parameters and process outputs commonly studied. New trends in ISF like hot forming, multi-point tool forming have been reviewed in detail. In this paper, the effect of different process parameters on the output responses are thoroughly reviewed. Moreover, existing literatures related to outputs like forming forces, geometric accuracy, surface finish and formability in ISF are studied and literature gaps are interpreted. Finally, concluding remarks on the literature gap identified from this review will provide the foundation to the researchers for future work. [ABSTRACT FROM AUTHOR]

The production of ultra-high strength automotive components requires a multi-directional approach. Hot stamping combines both forming and heat treatment processes to obtain a usually martensitic structure of complicated shaped automotive parts. The preparation for production using hot stamping must involve the latest methods of numerical analysis of both temperature changes and forming, which are applied for an increasing range of materials used. In this paper, the current state of knowledge about the basics of hot stamping, used technological lines, and the current state of material used with applied heat treatments and possible coatings have been reviewed. Moreover, the numerical modeling process has been described. The most important aspects of process automation, including the use of digital twins for simulation and optimization of operational kinetics of the robots accomplishing the production process, analysis and minimization of time of production cycles, and searching for weak operational points of the control systems and for real time visualization of operation of complete line, are considered. The digital twins and corresponding numerical models enable the symmetrical design of real production lines. The details of heat treatment profiles with so called tailored zone heat treatment are provided. Hot stamping is a dynamically developing technology as evidenced by the increasing range of materials used, also from the 3rd generation of advanced high strength (AHSS) steels. It starts to combine forming of symmetric or asymmetric elements with more complex heat treatment processes as required for dual phase (DP) stainless steels or the newest generation of high-strength and ductile medium-manganese steels. [ABSTRACT FROM AUTHOR]

The use of High Strength Steel (HSS) tubular components in structural frames allows a drastic increase of the stiffness-to-weight ratio and, therefore, may open new possibilities to the design lightweight components for the transport industrial sector. However, the diffusion of these elements is still limited by the lack of manufacturing technologies capable of efficiently forming and bending HSS hollow profiles. To overcome the limits of traditional room temperature processes, an innovative rotary draw bending process carried out at high temperature is proposed, in which the profile cross section is quickly heated to the target temperature and, then, bent and selectively cooled to induce controlled microstructure changes. The paper presents a fully coupled thermo-mechanical-metallurgical numerical model to support the process design, which was applied to 22MnB5 tubes. The model was used to identify the optimal thermal and mechanical parameters to increase the material formability and to obtain the target microstructure in the final part. All the process steps, namely heating, handling, forming, and cooling, were modelled, and the results were experimentally validated by industrial trials carried out on a bending pilot plant. The results prove the possibility of an accurate prediction of both the final shape and the distribution of the microstructural and mechanical properties along the bend. [ABSTRACT FROM AUTHOR]

Tailored properties hot forming of 38MnB5Nb by partition cooling can be configured on-demand. A gradient distribution microstructural characteristic can be generated by undertaking an appropriate cooling-tempering process for the regions with different properties requirements before forming. A unified viscoplastic constitutive model coupled with the primary cooling temperature and related material constants is established based on genetic algorithm. Meanwhile, the use of the mixture of jet air and dry ice particles to cool the partition region is essential to achieve different primary cooling temperatures. In this paper, the inverse heat conduction problem is solved to obtain the relationship between the interfacial heat transfer coefficient and different cooling conditions in the partition cooling process. The U-shaped part is taken as an example to simulate the change of temperature, stress-strain, thickness, and spring-back in the process of partition cooling and tailored hot forming properties. The results show that the gradient microstructural characteristic formed by partition cooling has a great influence on the stress field distribution. The maximum stress of 345 MPa can be reached after complete pressure holding in the partition slow cooling tailored properties of the hot forming process. The maximum stress can reach 743 MPa in the partition fast cooling tailored properties of the hot forming process due to the relatively high deformation resistance of the tempered martensite at the bottom center. The maximum residual stress in the two processes after spring-back drops to 305 MPa and 545 MPa, respectively. The spring-back is small under the two processes, with a maximum spring back angle of no more than 1°. [ABSTRACT FROM AUTHOR]