Tailor Rolled Blank Research Articles

Influence of thickness and strength on plastic instability in tailored steel structures

A mathematical model was intricately devised to explore the influence of continuous variations in thickness and mechanical properties on the performance of tailor rolled blanks (TRB) and tailor rolled tubes (TRT). Through the integration of analytical and numerical techniques, it was discerned that these variations play a pivotal role in modulating stress distribution and strain localization, thereby inducing a spectrum of plastic instability behaviors within the structures. The introduction of an ‘equivalent strength’ metric as a novel means to quantify structural performance shed light on strategic material distribution to enhance durability and mechanical efficiency. Moreover, the insights garnered from this research deepen the understanding of the mechanical responses of tailor-rolled constructs under varying loads, offering valuable perspectives for the development and fabrication of engineered materials with bespoke properties. This study not only contributes to bridging a knowledge gap in the realm of tailored material engineering but also fosters the advancement of design methodologies in the construction of high-performance engineered structures.

Mathematical modeling and analysis of the tailor rolled blank manufacturing process

A tailor rolled blank (TRB) is a plate of continuously varying thickness with the advantages of lightweight, high strength, and good surface quality. However, it is required that the roll gap can be adjusted online, and the plate and roll produce large elastic deformation in the TRB manufacturing process. These characteristics make the modeling of the force and deformation parameters more difficult. A new mathematical model of roll separating force in the TRB manufacturing process is established taking into account the feature of deformation in this research. The elastic deformation of the strip and the flattening deformation of the roll are considered in order to improve the prediction accuracy of the results. The roll separating forces of the entrance elastic compression region and the exit elastic recovery region are computed using the generalized Hooke's law. A new velocity field is proposed based on the deformation characteristics of the plastic region and velocity boundary conditions, and the power functionals of the internal deformation, shear, friction, and tension are calculated. The analytical models of force and deformation parameters combined the elastic and plastic deformation regions are obtained through iterative operation, which satisfies the convergence condition of the roll separating force and roll flattening. The roll separating force data obtained by the model in this research are compared with the actual measured values in the laboratory, and the deviation value is small, which proves the computational precision of the present model. Additionally, the variations of the entrance velocity and flow volume per second during the TRB manufacturing process are shown, and the influences of the tension and friction factor on the neutral angle and roll separating force are illustrated.

Topometry Optimization of Energy Absorbing Structure through Targeting Force-Displacement Method considering Tailor Rolled Blank Process

Inspired by topometry optimization, this work proposed a new design approach that mixed of targeting force-displacement (TFD) method and tailor rolled blank (TRB) process for thin-walled energy absorption structures, which has vast applied prospects in the aerospace and automotive industries. This method not only overcomes manufacturing difficulty caused by the TFD method based on topometry optimization but also provides a new idea for TRB energy absorption structure. The optimized results can be transferred to the computer aided design environment without additional postprocessing. Firstly, a uniform thickness constraint is introduced to make the designed structure have constant thickness distribution along desired direction; topometry optimization is carried out to use TFD method. Secondly, a method that can automatically divide the design domain is developed. The adjacent elements with smaller thickness differences are merged to form TRB subdomains based on the optimization results of forestep, and the TFD method is used again. Finally, TRB finite element modeling codes is developed. According to the second step, modeling of the transition zone is added to finally form the TRB structure that meets the requirements of manufacturing. This method is used to optimize the crashworthiness of the thin-walled tube under axial and oblique loading. Numerical results demonstrate the effectiveness of this method. Therefore, this method can be used to design high-efficiency energy absorber on aircraft or automobile, such as the strut of aircraft and energy absorption box of automobile.

Rule and optimization-based selection of car body parts for the application of tailor rolled blank technology

The majority of parts in modern car bodies is manufactured from sheet metal. Rarely these parts are fully stressed due to design space restrictions and complex requirements. The usage of tailor rolled blanks (TRB) enables the reduction of sheet thickness in areas less loaded and thus reduces part weight. Technically most sheet metal parts are potentially suited for the application of TRB. Economic circumstances like the additional flexible rolling process and technology-specific nesting constraints limit the application to a subset of parts. The search for the best candidate parts taking mass and cost into account is currently challenging. This article presents an optimization strategy for the selection of the parts in a vehicle structure that are best suited for the application of TRB. As a first step, a priori preferencing is performed to select parts based on engineering rules. Using a reduced number of candidate parts, high quality metamodels are trained to perform multiobjective optimizations of all possible combinations of remaining parts, revealing the most efficient part selection under consideration of mass and cost.

Formability evaluation of tailor rolled blank (TRB) with the forming limit margin field graph

Formability evaluation of tailor rolled blank (TRB) with the forming limit margin field graph

Analysis of tailor-rolled blanks having thickness distribution by finite element analysis

Tailored blanks have been widely applied in car body-in-white parts due to its ability to optimise weight for the purpose of reducing global emission. Tailor welded blanks are produced by joining sheets having different thicknesses by welding. However, stress concentration is induced due to sharp change in thickness and the heat affected zone has its microstructural and properties changed. Tailor rolled blanks on the other hand are semi-finished parts produced by rolling process where no joining is required. The continuous thickness transition reduces the sharp change in thickness. In this paper, the deformation behaviour of stainless-steel workpiece produced by rolling is being investigated under two different conditions using finite element analysis. Narrow profiled and grooved rolls were utilized for the production of tailored blanks with profile in width direction. The material flow and the thickness distribution were investigated during the rolling process for both sets of rolls.

On lower confidence bound improvement matrix-based approaches for multiobjective Bayesian optimization and its applications to thin-walled structures

In engineering practice, most design criteria require time-consuming functional evaluation. To tackle such design problems, multiobjective Bayesian optimization has been widely applied to generation of optimal Pareto solutions. However, improvement function-based expected improvement (EI) and the hypervolume improvement-based lower confidence bound (LCB) infill-criteria are frequently criticized for their high computational cost. To address this issue, this study proposes a novel approach for developing multiobjective LCB criteria on the basis of LCB improvement matrix. Specifically, three cheap yet efficient infill-criteria are suggested by introducing three different improvement functions (namely, hypervolume improvement, Euclidean distance and maximin distance) that assemble the improvement matrix to a scalar value, which is then maximized for adding solution points sequentially. All these criteria have closed-form expressions and can maintain the anticipated properties, thereby largely reducing computational efforts without either integration or expensive evaluation of hypervolume indicator. The efficiency of the proposed criteria is demonstrated through the ZDT and DTLZ tests with different numbers of design variables and different complexities of objectives. The testing results exhibit that the proposed criteria have faster convergence, and enable to generate satisfactory Pareto front with fairly low computational cost compared with other conventional criteria. Finally, the best performing criterion is further applied to real-life design problems of tailor rolled blank (TRB) thin-walled structures under impact loads, which demonstrates a strong search capability for with good distribution of Pareto points, potentially providing an effective means to engineering design with strong nonlinearity and sophistication.

Application of tailor rolled blanks in optimum design of pure electric vehicle crashworthiness and lightweight

At present, one of the promising solutions to the energy crisis and environmental protection is to widely use pure electric vehicles (PEV). It is noted that lack of range limits the wide use of PEV, in which lightweight can effectively improve the range of PEV. Lightweight and crashworthiness signify two main challenges facing in vehicle industry, which often conflict with each other. The tailor rolled blank (TRB) structure, as a novel configuration, has a great potential to achieve lightweight and improve the crashworthiness. In this study, a series of TRB structures are applied to the front-end components of PEV for the design optimization of vehicle crashworthiness and lightweight. A full-scale finite element (FE) model of PEV is first constructed and validated by physical test. Then the TRB FE models of vehicle front-end components are established to replace the corresponding conventional uniform thickness (UT) structures. Based on the vehicle model with TRB structures, the safety performance of vehicle in full frontal impact is analyzed by FE method. The results show that, compared with the UT design, the front-end components with TRB structures can improve the crashworthiness of vehicle to a certain extent. In order to determine the optimized geometric distribution of TRB structures, a multi-objective design optimization procedure is implemented for the vehicle crashworthiness and lightweight design with UT and TRB structures. On the basis of the Kriging (KRG) model and the multi-objective particle swarm optimization (MOPSO) algorithm, the weight of TRB structures is reduced and the energy absorption is increased relative to the UT design, which indicates the efficient improvement of the vehicle crashworthiness.

Experiment and simulation of variable thickness rolling for 3D-profiled blank

• A new method for rolling 3D-profiled blank is proposed. • Variable Thickness Rolling is modified for producing 3D-profiled blank. • 3D-profiled blank with thickness of 2.0 mm, 1.8 mm and 1.6 mm is obtained. A 3D profiled blank (3D-PB) is a variable thickness in both the rolling direction (RD) and transversal direction (TD). A novel method of manufacturing 3D-PB is proposed in this paper. The method combines two processes: first, the workpiece of a normal blank is rolled into a tailor rolled blank (TRB) through variable gauge rolling (VGR), then the TRB is rolled into a 3D-PB through variable thickness rolling (VTR). A significant modification was made to VGR as the original VTR could not be adapted to the production of 3D-PB. The metal flow of the thick and thin areas of the 3D-PB was investigated with finite element simulation. The metal in the thin area mainly flows in the TD. The deformation of the workpiece was studied during the process. The workpiece was first bent and then thinned, resulting in a different width between the thick and thin areas. The thickness difference between the thick and thin areas of the 3D-PB was explained through simulation and controlled rolling experiments. The final 3D-PB has a variable thickness in both the RD and TD with good shape.

Effects of annealing temperature on microstructure and properties of tailor-rolled blank of medium-manganese steel

The microstructure and mechanical properties of tailor-rolled blank (TRB) of medium-manganese steel during annealing were investigated. The annealing process of austenite-reverted transformation of the experimental steel was formulated. The effects of different morphologies on properties with different annealing temperatures in different thickness zones of TRB were analyzed. In the thin zone, the morphology is blocky, and in the thick zone, the morphology is lamellar. At the same annealing temperature, the tensile strength of the thick zone is lower than that of the thin zone, and the elongation and product of strength and elongation (PSE) of the thick zone are higher than those of the thin zone. With the increase in annealing temperature, the tensile strength increases, while the yield strength, the elongation and the PSE all decrease in the same thickness zone. Because the stability of lamellar austenite is higher than that of blocky austenite, the comprehensive mechanical properties in the thick zone are good. At the annealing temperature of 640 °C, the experimental steel has the best comprehensive mechanical properties, and the maximum PSE is more than 40.0 GPa% in different thickness zones. Particularly, PSE is up to 45.6 GPa% in the thickness zone of 2.0 mm.

Annealing of HC340LA tailor rolled blanks—Control of mechanical properties and formability

Abstract Tailor rolled blanks (TRB) have been extensively used in the automotive industry because of lightweight. Through the flexible rolling process and appropriate annealing treatment, the target geometry, required mechanical properties, and good formability of TRB can be achieved. In this study, two types of annealing processes were attempted, i.e. batch annealing and continuous annealing. The effects of annealing parameters on the microstructure, mechanical properties and formability of HC340LA TRB were investigated. First, a series of batch annealing and continuous annealing were conducted on cold rolled TRB. Next, the microstructure distribution of TRB was evaluated. The mechanical properties and formability of annealed specimens were tested through the uniaxial tensile test and Erichsen cupping test, respectively. The results showed that the mechanical properties and formability were controlled by reduction, annealing type and annealing parameters. During the batch annealing, mechanical properties along the rolling direction were influenced by the degree of recrystallization and the average grain size, the formability increased with the increase of annealing temperature. TRB annealed at 700 °C for 60 min showed relatively homogeneous mechanical properties and good formability in the reduction range of 36–54 %. During continuous annealing, the mechanical properties and formability were determined by the degree of austenitization and the average grain size. TRB annealed at 930–950 °C for 3 min showed homogeneous mechanical properties and good formability for the entire range of reduction.

Parallelized multiobjective efficient global optimization algorithm and its applications

In engineering practice, most optimization problems have multiple objectives, which are usually in a form of expensive black-box functions. The multiobjective efficient global optimization (MOEGO) algorithms have been proposed recently to sequentially sample the design space, aiming to seek for optima with a minimum number of sampling points. With the advance in computing resources, it is wise to make optimization parallelizable to shorten the total design cycle further. In this study, two different parallelized multiobjective efficient global optimization algorithms were proposed on the basis of the Kriging modeling technique. With use of the multiobjective expectation improvement, the proposed algorithm is able to balance local exploitation and global exploration. To implement parallel computing, the “Kriging Believer” and “multiple good local optima” strategies were adopted here to develop new sample infill criteria for multiobjective optimization problems. The proposed algorithms were applied to five mathematical benchmark examples first, which demonstrated faster convergence and better accuracy with more uniform distribution of Pareto points, in comparison with the two other conventional algorithms. The best performed “Kriging Believer” strategy approach was then applied to two more sophisticated real-life engineering case studies on the tailor-rolled blank (TRB) structures for crashworthiness design. After optimization, the TRB hat-shaped tube achieved a 3% increase in energy absorption and a 10.7% reduction in mass, and the TRB B-pillar attained a 10.1% reduction in mass and a 12.8% decrease in intrusion, simultaneously. These benchmark and engineering examples demonstrated that the proposed methods are fairly promising for being an effective tool for a range of design problems.

Study on geometric parameters affecting longitudinal bending performance for U-channel of Tailor rolled blank

Springback is a main defect of Tailor Rolled Blank(TRB) U-Channel in the course of longitudinal bending, and the bending springback performance of TRB can be affected by blank geometric parameters. The longitudinal bending performance of TRB U-Channel was studied through simulation and experiment in this paper. The springback distribution characteristics of TRB U-Channel during longitudinal bending were analyzed. The emphasis was put on discussing the influencing laws of TRB geometric parameters on springback. The research findings indicate that annealing can diminish springback of TRB, and make the springback distribution more uniform. Springback is in inverse proportion to thickness transition zone(TTZ) length and blank thickness, and is in proportion to blank size. As the ratio of the thinner side increases, springback of unannealed TRB increases, and springback of annealed TRB gradually decreases.

Springback Characteristics of Cylindrical Bending of Tailor Rolled Blanks

As a new type of variable thickness sheet structure, the TRB (tailor rolled blank) has good prospects for the development of lightweight materials in the automotive industry. However, springback is a key issue in production. Research on TRB springback characteristics has great significance for further applications due to variations in the sheet thickness and gradient distribution of the material mechanical properties. In this study, the springback characteristics of TRBs were investigated by means of the finite element code ABAQUS/USDFLD and experiments taking cylindrical bending as an example. The results showed that the cylindrical bending process of the TRB gradually evolved from three‐point bending to four‐point bending and, finally, to multipoint bending. At same time, the gradient of the thickness leads to the nonuniform longitudinal distribution of the von Mises stress. On the contrary, larger bending angles can be achieved by reducing R and improving Rd, but t/T has little effect on the bending angles. In terms of the influence of springback, increasing Rd and reducing R and t/T can lead to a smaller springback angle. This project provided an important opportunity to advance the understanding of TRB springback characteristics.

Real-time penetration state monitoring using convolutional neural network for laser welding of tailor rolled blanks

In this paper, an innovative monitoring system capable of diagnosing the penetration state during the laser welding process is introduced, which consists of two main blocks: a coaxial visual monitoring platform and a penetration state diagnosis unit. The platform can capture coaxial images of the interaction zone during the laser welding through a partially transmitting mirror and a high-speed camera. An image dataset representing four welding states was created for training and validation. The unit mainly consists of an embedded power-efficient computing TX2 and image processing algorithms based on a convolution neural network (CNN). Experiment results show that the platform can stably capture state-of-the-art welding images. The CNN used for a diagnosis of the penetration state is optimized using an optimal network structure and hyperparameters, applying a super-Gaussian function to initialize the weights of the convolutional layer. Its latency on TX2 is less than 2 ms, satisfying the real-time requirement. During the real laser welding of tailor-rolled blanks, a penetration state diagnosis with an accuracy of 94.6 % can be achieved even if the illumination changes significantly. The similar accuracy between the validating set and a real laser welding demonstrates that the proposed monitoring system has strong robustness. The precision and recall ratios of the CNN are higher than those of other methods such as a histogram of oriented gradients and local binary pattern.

Forming study on a tailor rolled blank (TRB) structure- formability evaluation and model verification

Tailor rolled blank (TRB) technique, as a relatively novel configuration, is of potential to fulfill the lightweight design. The examination of TRB defects in stamping process using traditional forming limit curve (FLC) is challenging. In this paper, the forming limit surface (FLS), which considers thickness changes, was used to evaluate the formability of front longitudinal beam (FLB) with TRB structure. A numerical model was developed to study the strain distributions and thickness transition zone (TTZ) movements during the TRB forming process. The effects of tool parameters (die clearance and draw-bead) on formability and TTZ movement were investigated. Results showed that the adaptive die gaps and segmented draw-beads were required in tool design to reach a better forming quality in the formed part. Besides, TTZ movement appears to be more structural dependent because the movements near the area with transition corner were larger and suffered smaller impact from parameter changes. The measured thicknesses of typical sections from formed part agree well with those predicted by simulation. This result confirms that the simulation strain used in formability evaluation was relatively reliable.

Mechanical Analysis of TRB Transition Region

In this paper, the mechanical properties of Tailor Rolled Blank (TRB) transition region was investigated By establishing a true stress-strain constitutive model of the TRB transition region. Firstly, the stress-strain curve obtained by uniaxial tensile test of 1mm, 2mm thick plates is subjected to regression analysis. Based on Ludwig equation, the true stress-strain constitutive equations of 1mm and 2mm thick plates were obtained. Then, The true stress-strain constitutive equation of TRB transition region was established by interpolation method combined with 1mm, 2mm thick plate constitutive equation, volume invariance theory and Von-Mises equivalent strain.Finally, the accuracy of the model is verified by simulation and experimental comparison. The results show: A new constitutive model of TRB was established, which is well responsed to the mechanical properties of the transition region.

Study on the Influence of Transition Zone Position on Bending Spring back of TRBs

In this paper, the crystal plastic finite element method is used to study the influence of the transition zone position of Tailor Rolled Blank (TRB) on the bending deformation behavior and spring-back from the mesoscale. The polycrystalline plastic finite element bending model of TRB is established and the bending forming process was simulated. The results show that the B-shaped blank (the blank consists of thick zone and transition zone) has a uniform plastic deformation and a smaller spring-back value than the A-shaped blank (the blank consists of thin zone and transition zone). The stress-strain zone of the B-shaped blank is uniform spread from the bend zone to both sides, but the stress-strain area of the A-shaped blank is transferred to the transition zone, which makes the blank exhibit poor forming properties. And this deformation ununiformity makes the spring-back angle of the A-shaped blank larger than that of the B-shaped blank.

Study on Process Parameters in Transverse Bending of Tailor Rolled Blanks

Study on Process Parameters in Transverse Bending of Tailor Rolled Blanks

Effect of Microstructure and Texture Evolution During Variable Gauge Rolling on Mechanical Properties of Tailor Rolled Blanks

In this study, anisotropic elastic and plastic mechanical properties of a tailor rolled blank (TRB) with thickness ratio of 0.52 (1 mm/1.9 mm), have been fully studied. To gain a deeper insight into anisotropic mechanical behavior of the studied TRB, continuous changes in microstructure and crystallographic texture of a dual phase steel caused by variable gauge rolling (VGR) were investigated on several points (on RD–ND plane) along longitudinal direction with the aid of EBSD observations. Analysis of grain boundary (GB) maps revealed that ferrite grain refinement is occurred during VGR so that the average ferrite grain size decreases from 4.1 µm for the thicker side to 2.2 µm for the thinner side. Furthermore, it was found out that substructure density is more intense within smaller ferrite grains. Evaluation of inverse pole figures as well as orientation distribution function maps showed that texture of thicker side comprises {001}〈110〉 and {112}〈110〉 components along $$ \alpha $$ -fiber. In addition, it was revealed that orientations of {111}〈110〉 and {111}〈112〉 along $$ \gamma $$ -fiber strengthen along VGR direction by further increase in thickness reduction near thinner side. Accordingly, unprecedented gradual changes in mechanical properties with respect to these changes in microstructure and texture, were obtained. Finally, the correlation between in-plane anisotropic mechanical properties [Young’s modulus (E), yield stress (YS), ultimate tensile stress (UTS) and total elongation] of the studied tailor rolled blank with microstructure and deformation texture was interpreted.