Anti-collision Beam Research Articles

Fracture Resistance Biomechanisms of Walnut Shell with High-Strength and Toughening.

Walnut shell is lightweight material with high-strength and toughening characteristics, but it is different from other nut shells' microstructure with two or three short sclerotic cell layers and long bundle fibers. It is essential to explore the fracture resistance biomechanism of lightweight walnut shell and how to prevent damage of bionic structure. In this study, it is found that the asymmetric mass center and geometric center dissipated impact energy to the whole shell without loading concentration in the loading area. Diaphragma juglandis is a special structure improved walnut shell's toughening. The S-shape gradient porosity/elastic modulus distribution combined with pits on single auxetic sclerotic cells requires higher energy to crack expansion, then decreases its fracture behavior. These fantastic findings inspire to design fracture resistance devices including helmets, armor, automobile anti-collision beams, and re-entry capsule in spacecraft.

Meta-structure with stable isotropic negative Poisson’s ratio based on the cube-framework stacked by Kirigami units

Negative Poisson’s ratio (NPR) metamaterials have excellent mechanical properties due to auxetic characteristics. However, the existing anisotropic NPR structures lead to non-uniform enhancement that limits their applications. Thus, a meta-structure with isotropic NPR is proposed here, in which Kirigami units is stacked in three-axis symmetrical cube-frameworks. The stable NPR is related to the degradability of the Hessian matrix in Hilbert-Einstein action of the Kirigami unit. With such structures, the specific modulus of thermoplastic polyurethane (TPU), silica gel, and acrylonitrile-butadiene-styrene (ABS) increase by 907.6%, 610.9%, and 210.5%, respectively. Finite element analysis further proves that improvement is associated with face constraint effects, which is from a moderate modulus of materials. Meanwhile, the isotropic meta-structures are introduced into anti-collision beams, energy-absorbing boxes, and protective helmets, proving their excellent application potential.

Study on the forming limit of rectangular-ribbed profile (日-shaped section) in rotary bending with flexible core die

The profile with rectangular ribbed (日-shaped) section is applied to the anti-collision beam of commercial vehicles, which not only improves the anti-collision performance but also improves the lightweight of the car. With the gradual decrease of the bending radius of the profile, the profile is prone to defects such as wrinkling of the inner wall or fracture of the outer wall. In this paper, the ABAQUS, a finite element simulation software, is used to establish the simulation model of the profile with rectangular ribbed section during the process of rotary draw bending, and the stress and strain laws are analyzed. The bending forming limit of the profile with rectangular ribbed section is studied by choosing the fracture of the outer wall as the evaluation standard. And the influences of bending speed, friction coefficient, and thickness on the forming limit are obtained. The minimum bending radius decreases as the bending speed increases and increases with increasing of friction coefficient and thickness.

Experimental study on cold forming process of 7075 aluminum alloy in W temper

7075 aluminum alloy (AA7075) in W temper, owning lower strength and higher elongation, demonstrates better formability at room temperature than the material in peak-aged T6 temper. In this work, post-forming artificial aging is used to restore the comprehensive mechanical properties of AA7075 in W-temper. A shortened artificial aging process with lower cost than the common peak aging process is proposed with the consideration of paint baking in automotive manufacturing. The effects of shortened artificial aging, peak aging, and paint baking on the mechanical properties of AA7075 are studied. Results show that the ultimate tensile strengths of AA7075 with peak aging (120 ℃/24 h) and shortened artificial aging (120 ℃/5 h) followed by paint baking (180 ℃/20 min) are both 540 MPa, and the fracture elongation is 15% and 16% respectively. Compared with peak aging, the overall mechanical property of AA7075 with shortened artificial aging treatment is slightly improved after paint baking, while the aging time is shortened by 79%, which greatly improves the production efficiency. A case study of W-temper forming of an anti-collision beam in vehicle side door is conducted. Cold forming experiments, post-forming heat treatments, and mechanical testing such as three-point bending and uniaxial tensile testing of sub-sized specimens are carried out. After paint baking, the tensile strength and maximum bending load of the AA7075 anti-collision door beams with peak aging and shortened artificial aging treatments are comparable, and a higher product of strength and elongation (about 7% increase) is achieved by shortened artificial aging. In addition, the related mechanism is discussed in terms of precipitation during peak aging, shortened artificial aging and paint baking.

Improving aero-thermal environment in vehicle under-hood through small modification upstream the cooling module

The control of vehicle cooling airflow is one of the key issues of under-hood thermal management as well as the reduction of cooling drag. Aerodynamic analysis using full vehicle CFD method was conducted to further improve the cooling efficiency of a production vehicle equipped with an air-guide. Existing under-hood airflow problem of the original vehicle was first analyzed, and then several modified schemes using various deflectors in the area between the front bumper and the condenser were proposed. The comparison of the under-hood airflow characteristics of each modified scheme and the original model was carried out. The simulation results revealed that sealing the cavity between the front bumper and the anti-collision beam could improve the airflow rate through the cooling module with a reduction in the total air intake volume from the grilles, while blocking the channel from the upper grille opening to the cavity could increase the airflow evenness through the cooling module. The aerodynamic and thermal tests in wind tunnels demonstrated that, for the best scheme with three deflectors at 40 km/h, the temperature of the coolant and the exhaust pipe were reduced by 6.6°C and 15°C, respectively, with a minor reduction in Cd,grilleopen, compared to those of the original vehicle. With less cooling airflow rate, the scheme with a single deflector blocking the upper channel of the cavity achieved similar cooling effect as the best scheme, the reductions of the coolant temperature and the exhaust temperature at 40 km/h were around 6.6°C and 13°C, respectively, with a similar value of Cd,grilleopen, compared to those of the original vehicle.

Large Torsion Deformation: Centrosymmetric Reentrant Honeycomb

There exist some problems in the crash box and anti-collision beam sandwich structure, such as monotone deformation pattern and uneconomical energy absorption performance. In order to raise the deformation capacity and energy absorption performance of sandwich structure, centrosymmetric reentrant honeycomb (CRH) and hexagonal centrosymmetric reentrant honeycomb (HCRH) are proposed based on auxetic reentrant honeycomb (ARH) in this work. Based on HCRH, four kinds of transverse combination structures and two kinds of longitudinal combination structures are obtained. The results of specific energy absorption show that the energy absorption capacity of the angular contact homodromous combination structure (ACOC) is about 3 times that of the other three transverse combination structures. Compared with longitudinal heterodromous combination structure (LHEC), the energy absorption capacity of longitudinal homodromous combination structure (LHOC) is improved by 72.7%.

Method for Controlling Edge Wave Defects of Parts during Roll Forming of High-Strength Steel

Cold roll forming is suitable for sheet metal processing and can provide a new method for the production and processing of anti-collision beams for commercial vehicles. In order to accurately control the edge wave defects of the parts in the roll forming process, we used the professional roll design software COPRA to design the roll pattern and used the professional finite element analysis software ABAQUS to establish a three-dimensional finite element analysis model of the “b”-shaped cross-section. We analyzed the factors affecting the edge wave by controlling different process parameters (the thickness of the sheet, the height of the flange, and the forming speed), and the best process parameter combination was determined. The results showed that the thickness of the sheet, the height of the flange, and the forming speed all had an effect on the edge wave defects of the “b”-shaped cross-section. The influence of sheet thickness was the greatest, followed by flange height and then forming speed. The final selected parameter combination was a sheet thickness of 3 mm, a flange height of 100 mm, and a forming speed of 150 mm/s. This work provides a theoretical basis for actual production.

Design and experimental validation of a new condenser of an automotive air conditioning unit to address non-uniform air velocity distributions

• The front anti-collision beam in a car leads to air maldistribution. • A six-path condenser is an optimization of the traditional four-path condenser. • The new condenser shows better capacity with the anti-collision beam. • The cooling performance of automobile air conditioning system is improved. To improve the efficiency of automobile air conditioning and reduce the impact of non-uniform air velocity distributions caused by the front anti-collision beam on automobiles, we designed a new six-process condenser and tested it under different working conditions. A baffle was positioned to simulate the anti-collision beam during the experiment. We analyzed the condenser by itself and the system level performance of this newly designed condenser under three working conditions compared to a traditional four-process condenser. Condenser heat exchange capacity, condenser inlet pressure, system refrigerant flow rate, refrigerant flow resistance, thermal imaging of condenser outlet air, overall system cooling capacity, and coefficient of performance were compared. The coefficient of performance of the system with this new condenser improved by 8.5%, 7.8%, and 10.3% for the three tested working conditions.

Optimized Design of Aluminium Bumper by Impact Test and Computer Simulation Analysis

Aiming at target steel car bumper new lightweight design, with a target vehicle steel bumper static crushing, three static pressure and impact test and simulation analysis based on the performance parameters, design targets bumper car aluminum alloy box, the section size of anticollision beam and the energy absorption and the materials they need to determine the aluminum bumper performance. The three-point static pressure method is used to optimize the design of the anti-collision beam. Because the loading condition is relatively simple, the optimization function of optistruct is used to optimize it to determine the cross-section shape and size of the anti-collision beam.

Research on low-speed collision performance of Collision resistance of different materials

In order to explore the impact of lightweight materials and structures on the performance of anti-collision beams, this paper selects aluminum alloy and carbon fiber as the research objects, and analyzes the difference in low-speed impact performance of open and closed anti-collision beams for these two materials. Based on the structure of carbon fiber materials, the mechanical properties of carbon fiber materials are analyzed. At the same time, a low-speed collision model is established using numerical simulation to study the maximum intrusion amount, intrusion acceleration and intrusion force changes with time during the collision of aluminum alloy and carbon fiber anti-collision beams, And finally use experiments to verify. The research results show that the impact of the open aluminum alloy anti-collision beam and carbon fiber anti-collision beam on the fluctuation range of the collision acceleration is less than that of the closed aluminum alloy anti-collision beam; at the same time, compared with the closed aluminum alloy anti-collision beam, the open aluminum alloy anti-collision beam and carbon fiber, the maximum intrusion of the anti-collision beam is reduced by 8.2% and 18.6%; the carbon fiber anti-collision beam has the greatest force during the collision, followed by the closed anti-collision beam and the open anti-collision beam. The test results are consistent with the numerical simulation, which further illustrates the rationality of the exploration results.

Damaged and failure characterization of 7075-T6 Al alloy based on GISSMO model

Failure simulation of 7075-T6 Al alloy is very important due to its relatively low ductility compared to conventional steel. A hybrid numerical-experimental method was developed to determine plastic strains at fracture as a function of triaxiality. The uniaxial tension tests were performed by using the specimens including pure shear, 45° shear, smooth, R5 notch and R15 notch. The fracture locus was established by calibrating the parameters of the Hosford-Coulomb fracture model and was implemented into the GISSMO damage model. The results showed that the predicted force-displacement data were in good agreement with the experimental results. The results of the mesh dependence showed that the mesh size in the range of 0.5–5 mm did not have much influence on the damage results. To assess the accuracy of the damage model, three-point bending tests of the anti-collision beam were performed. The calibrated GISSMO damage model could accurately predict the load-displacement data.

Simulation and Tests on Hot Forming Process Optimization for Door Anti-collision Beams

Simulation and Tests on Hot Forming Process Optimization for Door Anti-collision Beams

Novel flexible cores in rotary draw bending forming: applied for the commercial vehicle anti-collision beam with rectangular ribbed (日-shaped) section

In this paper, rotary draw bending (RDB) process is used to bend the rectangular ribbed (日-shaped) section profiles into commercial vehicle anti-collision beams. But the bottom plate of the profile will inevitably produce wrinkling defects in the actual processing. Therefore, ABAQUS finite element (FE) software is used to simulate the profile with no mandrel in RDB process to obtain the formation mechanism of the defects. Based on the above result, a novel type of mandrel-novel flexible cores (NFC) is designed. Its innovation is not only perfect for RDB of the rectangular ribbed (日-shaped) section profile but also can play a good role in occasions where the use of ordinary mandrels is limited. All in all, the working occasions are not limited. Moreover, changing the parameters of the mandrel core can achieve any angle bending under the premise of ensuring accuracy, and the cross-sectional distortion is small. Finally, the wrinkling rate at the bending area of the actual anti-collision beam product is measured and calculated, and the result shows that the wrinkling rate Q is less than the standard value that defines the presence or absence of wrinkling, which is regarded as no-wrinkling. And there is a good agreement between simulation and experimental results.

Effect of hot/warm rolling on the microstructures and mechanical properties of medium-Mn steels

This study provides processing strategies for the Fe-0.20C-11.0Mn-4.0Al steel to meet the requirements of different automobile parts by using hot rolling + intercritical hardening + tempering (HR) and warm rolling + tempering (WR). The mechanical properties and microstructure evolution were investigated. Due to a mild transformation-induced plasticity (TRIP) effect, twinning-induced plasticity (TWIP) effect and strain anisotropy during deformation, the HR sample showed the best product of tensile strength and elongation, which was above 70 GPa·% (strength: 889 MPa, total elongation: 79.6%); such a steel can be used in manufacturing complex-shaped automotive components such as anti-collision beams, C pillars and bumpers and even for cold working. The WR sample also achieved excellent mechanical properties, with a product of tensile strength and elongation of 45.8 GPa·% (strength: 1171.5 MPa, total elongation: 39.1%). Furthermore, the WR sample exhibited an increased dislocation density, fresh martensite formation and reduced high temperature ferrite phase, leading to a high yield strength of 938.7 MPa, which can be used in B pillars and floors for the prevention of intrusion in case of car collision.

Applying Baydur Composite Material in Designing Automotive Door Beams

This work studied the application of Baydur pultrusion composite material to the side door anti-collision beams of cars. The beams are currently made of high-strength steel materials and arranged inside the door to meet the requirements of road safety laws and regulations. The Baydur pultrusion composite material has many advantages that metal steel does not have. Based on the characteristics of the composite materials and safety standards for vehicle side collisions, we proposed a design to use Daybur composite material instead of steel as the anti-collision beam material in automobile side doors. The structural design of the beam with the composite material is optimized so that it can effectively improve the safety performance during side collisions and reduce the body weight to save fuel consumption. The feasibility of the design has been investigated from three aspects of technical manufacturing, safety performance and market application. The application of the composite material in the anti-collision beams will provide new options for the safety and energy efficiency of civil vehicles.

Reliability-based optimization of a novel negative Poisson's ratio door anti-collision beam under side impact

Anti-collision beam of front door has significant influence on occupant protection and side crashworthiness. In order to improve the comprehensive side impact performance of vehicle, this work proposes a novel negative Poisson's ratio (NPR) door anti-collision beam based on star-shaped cellular structural material, and optimizes it by a reliability-based optimization scheme. First, the parametric model of NPR anti-collision beam, vehicle model assembling NPR beam, occupant restraint system model and side collision model are established. Then, the basic mechanical properties of the NPR structure are investigated under considering the axial normal force, transverse shear force and bending moment of each rod, and the macro performance of NPR beam are analyzed. Next, a deterministic optimization integrating optimal Latin hypercube sampling (OLHS) method, response surface model (RSM) and NSGA-II algorithm is conducted to improve the performance of novel NPR beam. Finally, considering the uncertainties of design variables, a reliability-based optimization is further executed to enhance the robustness of the deterministic optimization by using Design for Six Sigma (DFSS) method. Simulation results show that the ultimate optimized NPR anti-collision beam can not only ameliorate driver's protection and side crashworthiness, but also ensure the reliability and lightweight effect. • An NPR beam is proposed to protect occupant safety and structural integrity. • The performance of star-shaped NPR beam is investigated. • Reliability-based optimization is conducted to improve the overall performance.

Analysis of lower limb injury mechanism of an average Chinese pedestrian lower limb FE model in lateral impact

According to the statistics, lower limb injuries are the second most frequent region of traffic injuries. For the in-depth study of the biomechanical response and injury mechanism of pedestrian lower limb, the pedestrian lower limb biomechanical Finite Element (FE) model with high biological fidelity was developed and verified. By applying the proposed model, simulation studies were conducted to investigate pedestrian lower limb dynamic responses and injuries under different bumper foam filling structures and bumper collision heights during lateral impact. Simulation results demonstrated that filling the cushion foam between the bumper cover and the anti-collision beam can effectively reduce the injury index of pedestrian's lower limbs, and the trapezoidal foam structure gives better protection effect. In addition, appropriately lowering the bumper collision height can improve the car's friendliness to pedestrian's lower limbs.

Analysis of lower limb injury mechanism of an average Chinese pedestrian lower limb FE model in lateral impact

According to the statistics, lower limb injuries are the second most frequent region of traffic injuries. For the in-depth study of the biomechanical response and injury mechanism of pedestrian lower limb, the pedestrian lower limb biomechanical Finite Element (FE) model with high biological fidelity was developed and verified. By applying the proposed model, simulation studies were conducted to investigate pedestrian lower limb dynamic responses and injuries under different bumper foam filling structures and bumper collision heights during lateral impact. Simulation results demonstrated that filling the cushion foam between the bumper cover and the anti-collision beam can effectively reduce the injury index of pedestrian's lower limbs, and the trapezoidal foam structure gives better protection effect. In addition, appropriately lowering the bumper collision height can improve the car's friendliness to pedestrian's lower limbs.

Experimental study and a damage model approach to determine the effect of hot forming deformation on the service performance of 22MnB5 steel

Forming damage affects the service performance of hot stamped components such as A-pillars, B-pillars and anti-collision beams. Existing constitutive models are not suitable for predicting this problem. This research aimed to experimentally and numerically study the effect of forming damage caused by hot stamping on the service performance of quenched 22MnB5 steel. The pre-forming defects were introduced into samples at 850 °C, and then the samples were quenched, cut, and stretched to fracture to ascertain the relationship between the forming strain, ultimate stress and failure strain. X-ray diffraction (XRD) tests and microstructure tests were conducted to investigate the phase composition and microdefects, respectively. A Damage-Coupled Pre-forming Constitutive Model (DCPCM) was proposed and embedded into ABAQUS by the VUMAT interface to simulate the service performance of quenched 22MnB5 steel. The results showed that the main reason for the reduced mechanical properties of the quenched 22MnB5 steel with pre-strain was increases in the number of microvoids and microcracks rather than changes in phase composition. The prediction by the proposed constitutive model agreed with the experimental results. These predictions are important for the performance design of hot stamped components.

One-Time Roll-Forming Technology for High-Strength Steel Profiles with “日” Section

Roll forming is an important processing method for the production of commercial vehicle anticollision beams, and edge buckling is one of the common defects in roll-forming process. In this paper, the “日” shape section of roll forming is studied, and first the b-shaped section is formed by roll forming, and the internal weld line is automatically welded while forming; then the long side of the b-shaped section is bent into the “U” shape, and the external weld line is welded while forming. The profile is cut off and then bent at both ends to form a commercial vehicle anticollision beam. The ABAQUS finite element software is used to model and analyze the factors affecting the “edge buckling” defect of roll-formed products. This paper uses three factors and three levels of orthogonal simulation experiments to study the problem. The results show that the effect of the factors of flange height, sheet thickness, and forming speed on the formation of edge buckling is in the order of sheet thickness > flange height > forming speed. The edge buckling size of the vertical edge of b-shaped tube decreases with the increase of sheet thickness and increases with the increase of flange height.