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Crashworthiness is a measure to ensure that a vehicle is able to absorb energy of impact in a crash and be safer for occupants. Generally, the experimental methods of crashworthiness are time consuming and expensive. This paper presents the simulations of crash tests based on the Federal Motor Vehicle Safety Standards that simulate a full frontal i...
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... Sun et al. [4] evaluated the global warming potential per kg of AHSS, Al alloy, and carbon-fiber-reinforced plastic and concluded that AHSS has the lowest carbon dioxide emissions. Additionally, Safari et al. [5] conducted simulations of full frontal impact, side-impact, and roof crush tests, which showed that AHSS materials exhibit superior crash safety performance. For these reasons, average usage of AHSS in vehicle automobile bodies has significantly increased in recent years due to its high strength-to-weight ratio, improved crash performance, and reduced environmental impact [6]. ...
The wear tests are conducted on bending punches deposited with PVD CrN and AlTiCrN coatings using the newly proposed progressive die. Then, the surface quality of the formed product is characterized through the surface roughness measurement after forming of TRIP1180 steel sheets. The correlation between the tool wear, in terms of wear depth and roughness and the product surface roughness can be quantitatively analyzed. The results show that the roughness remains comparable to that of the as-received surface before failure occurs, which represents smooth product surface without severe scratches and defects. While micro scratches on the punch surface have no effect on the quality of the product surface, severe fretting wear on the punch surface leads to a deterioration in the surface quality. Once initiated in the stamping process, the wear progresses exponentially within short time. The wear is also characterized as less than the coating thickness, but it results in complete removal of the coating layer. The partially worn punch plows the product surface, causing surface scratches with grooves and ridges, resulting in the roughness of 1.0 μm. In contrast, the surface with completely damaged coatings is extremely rough, with the roughness of 2.0 μm. This study presents the efficient method to evaluate the tool wear progression by indirectly measuring the product surface quality with reliably high precision.
Graphical abstract
... In recent years, AHSS parts have been employed in automobiles, guaranteeing crash safety and meeting the development trend of lightweight [1,2]. After the hot stamping process, 3D laser cutting technology is usually used to remove the workpiece material as the parts' strength usually reaches 1500 MPa. ...
Advanced high strength steel (AHSS) has been widely used in automobile components due to its good lightweight effect and high safety. 3D laser cutting is the most dominant method for removing material from AHSS. However, the springback in the whole manufacturing process severely causes 3D laser cutting path deviations. To improve the cutting accuracy, a novel 3D laser cutting path compensation method considering the springback transfer is proposed in this paper. The AHSS A-pillar is used to investigate the springback behavior in the whole process. The hot stamping finite element model and 3D laser cutting finite element model are established, respectively. Through the finite element simulation analysis, the accuracy evolution law of the part during the whole process is discussed. Based on the accuracy evolution law of the hot stamping and the accuracy evolution law of the laser cutting process, the proposed compensation method is employed to modify the laser cutting path. The modified path is then applied to a 3D laser cutting experiment. The experimental results show that the deviation value is reduced by about 15% compared with the conventional 3D laser cutting process. The proposed 3D laser cutting path compensation method shows the advantage of high accuracy, which can also effectively improve production efficiency.
... It is estimated that the strain rate during a crash event is in the range of ~10 1 -10 3 s -1 (Mahadevan et al., 2000). Thus, the high-strain-rate mechanical properties of PHS are of great interests for both academia and industry considering its real applications (Karbasian and Tekkaya, 2010;Safari et al., 2018). ...
The strain rate dependent mechanical properties of lath martensite are important for developing ultrahigh strength steels for automobile applications. Here, taken 2 GPa grade press hardening steel as a model material, we explored the strain rate sensitivity of lath martensite and the underlying physics. Uniaxial tensile tests were carried out over a wide range of strain rates from 10⁻³ to 1450 s⁻¹ to determine the rate dependent mechanical properties. Strain rate exerts minor effect on mechanical properties at strain rates below 10² s⁻¹. In contrast, both yield strength and work-hardening rate substantially increase with strain rate during high-strain-rate deformation. Microstructural evolution was characterized using electron backscatter diffraction and transmission electron microscopy. Particularly, synchrotron X-ray diffraction was used to measure dislocation density. The respective strengthening contributions from the friction stress, dislocations and high-angle block boundaries in lath martensite were evaluated on the basis of the measured microstructural parameters as well as related phenomenological models for predicting their strengthening effects. It is found that the enhanced yield strength during high-strain-rate deformation is due to a larger lattice friction for dislocation slip. The higher work-hardening rate is attributed to the enhanced mechanical heterogeneity within the current lath martensite microstructure at higher strain rates, which leads to larger strain gradient and thus promoted generation of geometrically-necessary dislocations.
... To achieve both light weight and crash safety, the application of advanced high strength steels (AHSS) is essential [3][4][5]. The reduction in sheet thickness by the use of high strength steels is being increasingly adopted as an effective means for weight reduction without compromising safety [6,7]. ...
Safety norms across the world are becoming more and more stringent posing new challenges to achieve lightweight vehicle structures. Structures made of advanced/ultra-high strength steels (AHSS) play a vital role in meeting the vehicle safety targets, by absorbing large amounts of impact energy, as well as by withstanding higher impact loads that occur due to vehicle collisions. Safety simulations usually take longer solution times due to their complexity and nonlinear nature. Engineers often encounter with a problem of quick evaluation of safety performance using different grades of materials to optimize the weight and cost. A new methodology—equivalent energy absorption (EEA)—has been proposed to do a quick trade-off study on performance versus weight for various thicknesses and material combinations. A relationship is established between the gauge and grade of a component to derive an equivalent safety performance so that engineers can make quick decisions by conducting minimal number of simulations. A simple rectangular crush box was considered for study to assess the energy absorption (EA) with various material and thickness combinations. A design of experiments (DOEs) study was done using simulations with many numbers of material grades and gauges to construct a 3D response surface between gauge grade and EA parameters to understand the relationship between each of these parameters. A case study has been discussed in the paper about application of this methodology on a vehicle to evaluate its safety performance. It was found that more than 80% evaluation time is reduced using this methodology.
... Although AHSS results in the least weight reduction among these lightweight materials, it is relatively inexpensive to produce AHSS automotive body components [1][2][3]. Furthermore, a vehicle structure composed of AHSS showed outstanding crash safety performance in a simulation of three crash tests: frontal wall impact, side barrier impact, and roof strength tests [4]. To reduce the cost and meet safety regulations, automakers have increased the proportion of AHSS used in vehicle structures [5]. ...
... In the case of the CrN-coated punches, the ( ) (red line) of the R3.0 punch is smaller than that (blue line) of the R5.5 punch at the same wear depth value. That is, for punches with the same surface hardness, to calculate the same wear depth, ( ) is inversely proportional to the contact pressure and sliding distance, which can be calculated from Equation (4). Therefore, the scale factor of the R5.5 punch, which has a smaller contact pressure, is larger than that of the R3.0 punch. ...
... In the case of the CrN-coated punches, the k(n) CrN (red line) of the R3.0 punch is smaller than that (blue line) of the R5.5 punch at the same wear depth value. That is, for punches with the same surface hardness, to calculate the same wear depth, k(n) is inversely proportional to the contact pressure and sliding distance, which can be calculated from Equation (4). Therefore, the scale factor of the R5.5 punch, which has a smaller contact pressure, is larger than that of the R3.0 punch. ...
In conventional wear simulation, the geometry must be updated for succeeding iterations to predict the accumulated wear. However, repeating this procedure up to the desired iteration is rather time consuming. Thus, a wear simulation process capable of reasonable quantitative wear prediction in reduced computational time is needed. This study aimed to develop an efficient wear simulation method to predict quantitative wear reasonably in reduced computational time without updating the geometry for succeeding iterations. The wear resistance of a stamping tool was quantitatively evaluated for different punch shapes (R3.0 and R5.5) and coating conditions (physical vapor deposition of CrN and AlTiCrN coatings) by using a progressive die set. To capture the nonlinear wear behavior with respect to strokes, a nonlinear equation from a modified form of Archard’s wear model was proposed. By utilizing the scale factor representing the changes in wear properties with respect to wear depth as input, the simulation can predict the behavior of rapidly increasing wear depth with respect to strokes after failure initiation. Furthermore, the proposed simulation method is efficient in terms of computational time because it does not need to perform geometry updates.
... In recent times, the automotive industries have prioritized the lightweight and durability of automotive parts to increase driving safety and reduce vehicle weights. It also helps in reducing fuel consumption and carbon emissions (Ref [1][2][3]. It promoted the use of high-strength and heat-treated steel sheets, which can meet such requirements ( . ...
Spheroidization is a common technique to improve the formability and machinability of material. Multiple combinations of deformation level and annealing time were employed to optimize the microstructure in 22MnB5 steel, aiming to achieve maximum spheroidization and keeping the process most economical. The critical annealing temperature for spheroidization was decided through differential scanning calorimetry measurement. Spheroidization was achieved by annealing of as-received and three different amounts of cold-rolled material, namely 10, 20, and 30% reduction in thickness. Annealing was done at 720 °C for four different times, 10, 20, 40, and 60 h, at all deformation levels. Convoluted multiple whole profile fitting technique of x-ray diffraction pattern was used to estimate the stored dislocation density in the material after different deformation levels. The microstructural investigation was performed using optical microscopy, scanning electron microscopy and EBSD techniques. The extent of spheroidization was measured through the average aspect ratio of cementite precipitate. Mechanical properties were measured through surface and core micro-hardness of initial and spheroidized samples. Microstructural characterization showed that deformation produced sub-grains and low angle grain boundaries, facilitating an easy path for diffusion of carbon. However, it was also found that a very high amount of pre-strain is also detrimental to the spheroidization process because it results in the formation of very long and sharp cementite lamella, which required more annealing time for spheroidization. The best processing parameter for spheroidization of 22MnB5 steel, considering the optimum spheroidization and minimum cost of the process, was found as 20% cold rolling reduction followed by 20 h annealing.
... The lightweight and crashworthiness design of the side body of an automobile can be taken as an example [15], [18], as shown in Fig. 1. Usually, the side body of an automobile consists of many parts, such as B-Pillar and side door impact beam [19], [20]. Both the structure and material of each part have a great influence on the mass and crashworthiness. ...
... An example in Fig. 2 is used to illustrate this issue. In Fig. 2, LSBT is used to approximate 20], and x ca ∈ {a, b}. The aim is to select the best solution from A, B, C, and D. Note that A has the best original objective function value, and A and B are better than C and D. According to the predicted values, the solution with good quality (i.e., A or B) will be selected. ...
... An example in Fig. 3 is used to illustrate this issue. In Fig. 3, RBF is used to approximate the following two functions: 20], and x ca ∈ {a, b} and b) f 2 (x cn , x ca ) (a, a, a, a, a, a, a, a, a). with n 1 = 1, n 2 = 9, x cn ∈ [−100, 100], and x ca j ∈ {a, b, c, d, e}(j = {1, . . . , n 2 }). ...
As an effective optimization tool for expensive optimization problems (EOPs), surrogate-assisted evolutionary algorithms (SAEAs) have been widely studied in recent years. However, most current SAEAs are designed for continuous/combinatorial EOPs, which are not suitable for mixed-variable EOPs. This article focuses on one kind of mixed-variable EOP: EOPs with continuous and categorical variables (EOPCCVs). A multisurrogate-assisted ant colony optimization algorithm (MiSACO) is proposed to solve EOPCCVs. MiSACO contains two main strategies: 1) multisurrogate-assisted selection and 2) surrogate-assisted local search. In the former, the radial basis function (RBF) and least-squares boosting tree (LSBT) are employed as the surrogate models. Afterward, three selection operators (i.e., RBF-based selection, LSBT-based selection, and random selection) are devised to select three solutions from the offspring solutions generated by ACO, with the aim of coping with different types of EOPCCVs robustly and preventing the algorithm from being misled by inaccurate surrogate models. In the latter, sequence quadratic optimization, coupled with RBF, is utilized to refine the continuous variables of the best solution found so far. By combining these two strategies, MiSACO can solve EOPCCVs with limited function evaluations. Three sets of test problems and two real-world cases are used to verify the effectiveness of MiSACO. The results demonstrate that MiSACO performs well in solving EOPCCVs.
... Duan et al. (2019) performed multi-objective reliability-based design optimization (RBDO) to the front longitudinal beam and make it more lightweight and crashworthy. With respect to other crashworthiness optimization, readers may refer to Gu et al. (2013), Sun et al. (2017), Lin et al. (2018), Safari et al. (2018), Gao et al. (2019), etc. ...
At present, the safety performance and lightweight of passenger car seat has become more and more important. The multi-objective lightweight optimization of the passenger car seat frame is carried out in this study. The novelty of this study is that we propose a detailed optimization design method and a design process in lightweight optimization for passenger car seat. In more detail, firstly, according to the ratio of energy absorption to mass method, the lightweight design components are selected. Secondly, different seat safety tests are conducted to optimize the corresponding components by considering both continuous thickness variables and discrete material variables. Thirdly, the strain index, the displacement of key points, the material cost, and the total mass of the components which need to be optimized (opti-components) are considered objectives. After that, the grey relational analysis (GRA) is adopted to optimize the material thickness scheme of the lightweight design components. Besides, the optimized coefficient of variation (OCV) method is applied to evaluate the corresponding weighting values of the objectives. Meanwhile, the availability of the grey relational analysis and optimized coefficient of variation (GRA&OCV) is assessed through comparing advantages among the method of GRA&OCV, the grey relational analysis and coefficient of variation (GRA&CV), the technique for order preference by similarity to ideal solution and coefficient of variation (TOPSIS&CV), as well as the technique for order preference by similarity to ideal solution and optimized coefficient of variation (TOPSIS&OCV) in the multi-objective lightweight optimization of passenger car seat frame. As a result, the total material cost and mass of the passenger car seat frame are reduced by 17.00% and by 2.08 kg (12.46%), respectively, with guaranteed vibrational and safety performance. Therefore, GRA&OCV can be effectively applied in multi-objective lightweight optimization of the passenger car seat frame.
... In order to reduce the structure's weight while retaining required strength, materials for the structure must be stronger and tougher [10][11][12]. Profound progress in automobile steel manufacturing has been achieved through the development of advanced high-strength steels (AHSS), fueled by the conflicting demands on the automotive industry to simultaneously improve crash safety and fuel economy [13][14][15]. ...
Dual phase steel generally has poor deep drawing property with a low r value less than 1.0, making it difficult to be used for deep drawing automotive parts. In order to improve the mechanical properties of the steel through heat treatment, effect of heat treatments with different conditions on a Fe-Si-Cr-Mo-C deep drawing dual-phase steel was investigated with the aim of identifying effective heat treatment parameters for effective modification towards optimal properties. Relevant thermal dilation and heat treatment experiments were performed. Corresponding characters were investigated. The results show that island martensite can be obtained at low cooling rate. With the increase of cooling rate, the formation of pearlite and bainite is favored. During annealing at low temperatures, recrystallization of the steel is incomplete with the presence of the shear bands. With the increase of annealing temperature, the recrystallization process is gradually complete, and the number of high angle grain boundaries increases significantly. The ratio of gamma orientation components to alpha orientation components decreases first and then increases with the increase of annealing temperature. The strain hardening exponent and r value show an upward trend with respect to annealing temperature, and the r value is as high as 1.15.
... Today's automotive industry prioritizes lightness and durability to increase driving safety and reduce vehicle weights to reduce fuel consumption and carbon emissions [1][2][3][4]. For this reason, in recent years, the use of ultra-highstrengthened and heat treatment capability developed sheets has become widespread [5][6][7]. ...
In this study, the microstructure and mechanical properties of the 22MnB5 steel sheet were investigated in different heat treatment conditions. The steel sheet heated to 700 °C, 800 °C, and 900 °C was subjected to air cooling, water quenching, and water quenching + tempering procedures. Microstructural properties post-heat treatment were analyzed under an optical microscope. To determine the mechanical properties, uniaxial tensile tests, and hardness measurements were performed. The highest mechanical properties were achieved with the water quenching from 800 °C and 900 °C. The elongation value was ranged of 2-4% with the water quenching. Also, the tempering process slightly increased the elongation value.
