Enhancement Of Crashworthiness Research Articles

Multi-Objective Robust Design Optimization for Crashworthiness Enhancement of Hybrid 2D Triaxially Braided Composite Tube Using Evolutionary Algorithms.

An innovative optimal design framework is developed aiming at enhancing the crashworthiness while ensuring the lightweight design of a hybrid two-dimensional triaxial braided composite (2DTBC) tube, drawing insights from the mesostructure of the composite material. To achieve these goals, we first compile the essential mechanical properties of the 2DTBC using a concentric cylinder model (CCM) and an analytical laminate model. Subsequently, a kriging surrogate model to elucidate the intricate relationship between design variables and macroscopic crashworthiness is developed and validated. Finally, employing multi-objective evolutionary optimization, we identify Pareto optimal solutions, highlighting that reducing the total fiber volume and increasing the glass fiber content in the total fiber volume are crucial for optimal crashworthiness and the lightweight design of the hybrid 2DTBC tube. By integrating advanced predictive modeling techniques with multi-objective evolutionary optimization, the proposed approach not only sheds light on the fundamental principles governing the crashworthiness of hybrid 2DTBC but also provides valuable insights for the design of robust and lightweight composite structures.

Development of Bi-hexagonal hybrid crash box subjected to axial loading for enhancement of crashworthiness

Crash box design had been developed to increase crashwortiness performance. The crash box cross section is one important parameter to increase the energy absorption as crashwortiness performance. In the previous study, hexagonal cross section provide the higher energy absorption than other cross section. One of strategy to increase cross section is using two cross section put together in one component of crash box design. Bi-tubular crash box shows higher energy absorption with easy manufacture opportunity. In other study, hybrid crash box is investigated to reduce crash box mass. In this study, development of bi-hexagonal hybrid crash box subjected to axial loading to enhance crashworthiness were investigated. Analysis of crash box design is developed by using computer simulation with ANSYS Workbench 19.2. The crash box materials used are Aluminum Alloy and carbon-epoxy woven. The material modeling in the crash box is assumed as deformable body while the impactor is a rigid body. The axial loading is modelled by setting impactor impact the crash box with a speed of 7.67 m/s. Fixed support is set on the bottom of crash box. Nine of frontal test models were simulated for the bi-hexagonal hybrid crash box with different layups orientation angle and composite hexagonal tube diameter. Energy absorption and deformation patterns were observed. The results indicated that the highest energy absorption and specific energy absorption is occured on the A60 model with layups orientation angle of [0/60/0/60] and composite hexagonal tube diameter of 41 mm are 3693.8 J and 19.121 kJ/kg. The deformation pattern in the aluminum part is diamond mode, while in the composite part, the deformation pattern produce transverse shearing, lamina bending, brittle fracturing and local buckling mode

Crashworthiness Enhancement of Aluminum Alloy Used for Leading Edges of Wing and Empennage Structures

Crashworthiness Enhancement of Aluminum Alloy Used for Leading Edges of Wing and Empennage Structures

Crashworthiness enhancement of thin-walled hexagonal tubes under flexural loads by using different stiffener geometries

Thin-walled structure tubes have been widely used in automotive applications as energy absorber members due to the excellent energy absorption ratio to the weights. The purpose of this study is to enhance the energy absorption of the thin-walled hexagonal tube by using different stiffeners geometries under the flexural impact. The structure has been subjected to an impact velocity of 50 km/h with a striker mass of 1500 kg at a 90-degree angle as recommended by the technical protocol section of the Insurance Institute for Highway Safety (IIHS) side-impact crash test. Besides the empty tube and the foam-filled tube, nineteen stiffeners were used in this study. A comparison between the reinforced and non-reinforced structure was made in terms of the specific energy absorption (SEA) and the crushing force efficiency (CFE). The numerical results have shown that stiffeners have improved the crashworthiness parameters when compared with the conventional empty tube. The numerical results have revealed that the introducing stiffeners to the structure have enhanced the structure performance since the stiffeners restrict the flattening of the upper side when subjected to compressive loadings and the SEA was improved for different wall thickness used. The results have shown that the H-5 stiffener was chosen as the best geometry since the SEA was increased up to 114%, the CFE was enhanced by 27% and the bending resistance was also improved.

Optimisation of thin-walled hybrid vertical struts for crashworthy aircraft designs

This research concerns the crashworthiness enhancement of a model of a Boeing 737-200 fuselage section. Using a validated numerical specimen, four thin-walled crushable hybrid energy absorbers are added to the aircraft to work as vertical struts. The absorbers are composed of a hollow aluminium tube, a star-shaped glass fibre–reinforced polymer inner matrix and foam extrusions. The absorbers—with variable tube edge and thickness, composite thickness and core height—are single- and multi-objectively optimised. Surrogate models and genetic algorithms are used for the minimisation of acceleration loads, injury levels and the strut’s weight. Results yield a more efficient frames’ collapse evolution with plastic dissipation increased by over 50%. Consequently, acceleration peaks are up to 50% lower at the two measured locations while maintaining low mass values. Injury levels were also reduced from severe to moderate according to an Eiband diagram.

Development of high-performance energy absorption component based on the structural design and nanocrystallization

Over the past decades, to meet the ever-increasing energy-saving and environmental-friendly needs, light-weight vehicles, e.g., electric cars, have been widely advocated. Due to significant deterioration in the capability of energy dissipation, crashworthiness enhancement becomes again the most critical issue for the light-weighted vehicles. However, the design based on conventional structure has been more difficult, and the employment of high-strength materials induces much higher cost. To achieve both large safety margin and low cost, this study implemented both material enhancement and structure optimization in the energy absorber design. Since most light-weight structures involve thin-walled frames, the surface mechanical attrition treatment (SMAT), able to induce nanostructures in metals for strength enhancement without sacrificing ductility, is the perfect choice. Based on the structure of energy absorber, SMAT technology was intensively improved to take full advantage of the excellent performance of the advanced steel material and fulfill real-life application. Structure optimization was also explored through extensive experiments and numerical simulations. The final products was examined by real tests, and the results revealed that it was lighter, stronger and have high-safety impact levels compared to similar products on the present market as expected.

Comparative Study of Trigger Configuration for Enhancement of Crashworthiness of Automobile Crash Box Subjected to Axial Impact Loading

An automobile crash box is a thin walled structure made of metal or composite material which is mounted on the front region of the vehicle. Its main purpose is to absorb the energy due to collision in the event of a crash. Crash boxes made of metals like steel and aluminum are widely used whereas use of composite crash boxes is in development phase in automobile industry. In automobile industry there is always a quest to reduce the mass of the vehicle for reduction of raw material usage and also to increase fuel efficiency. Composite crash boxes provide very good weight to stiffness ratio which makes them good contenders. But the behaviour of parts made of composite material in impact or collisions has to be understood for its usage in automobile structure. Crash box plays an important role in the event of a frontal collision of the vehicle. A crash box should absorb maximum possible energy and should deform sequentially so that the deformation pattern is not random. In this paper the effect of various types of triggers is investigated for GFRP composite crash boxes. Trigger is a geometrical feature applied to the crash box with the objective of achieving the desired energy absorption, deformation pattern and peak force. A comparative study of variation of peak forces, energy absorbed, S.E.A (specific energy absorbed) was done with the variation of triggers for crash box. Force vs. displacement curves were plotted for each case providing detailed insights into the force variation during deformation.

Prediction of Fracture Strains for DP980 Steel Sheets Using a Modified Lou–Huh Ductile Fracture Criterion

This paper is concerned with the prediction of fracture strains for DP980 steel sheets using a modified Lou–Huh ductile fracture criterion. The usage of DP980 steel is significantly increasing in the automotive industry for weight reduction, enhancement of crashworthiness and safety of car body. The material behavior of AHSS show unpredictable and sudden fracture during sheet metal forming process. A modified Lou–Huh ductile fracture criterion is utilized to predict the formability of AHSS because the conventional FLD constructed based on necking is unable to evaluate the formability of AHSS. Fracture loci were extracted from 3D fracture envelopes by assuming the plane stress condition to evaluate equivalent plastic strain up to the point of fracture at a wide range of loading paths. Three different types of specimens such as pure shear, dog-bone and plane strain grooved specimens were used for tensile tests to construct 3D fracture envelopes of DP980. Fracture strain of each loading path was evaluated to show that there is little deviation between predicted fracture strains and experimentally acquired ones. From the comparison, it is concluded that the 3D fracture envelopes can accurately predict the onset of the fracture of DP980 steel sheets in complicated loading conditions including the pure shear condition.

Development of a new crash/dynamics control integrated mathematical model for crashworthiness enhancement of vehicle structures

In this paper, a new crash/dynamics mathematical model is developed to optimise the crashworthiness using vehicle dynamics control systems (VDCS) in case of full frontal vehicle-to-vehicle crash scenario. In this model, the anti-lock braking system (ABS) and the active suspension control system (ASC) are co-simulated with the full car vehicle dynamics model and integrated with the front-end structure. The associated equations of motion of the model are developed and solved numerically. Validation of the vehicle crash structure of the proposed model is achieved to ensure that the modelling of the crumple zone and the dynamic responses are reliable. It is demonstrated from the numerical simulations that the vehicle dynamic responses are captured and analysed and the influence of VDCS is determined accurately. In addition, it is shown that the mathematical model is flexible, useful and can be used in optimisation studies. Furthermore, it is shown that the VDCS affect the crash characteristics positively.

Design of thin wall structures for energy absorption applications: Enhancement of crashworthiness due to axial and oblique impact forces

This paper describes a computationally aided design process of a thin wall structure subject to dynamic compression in both axial and oblique directions. Several different cross sectional shapes of thin walled structures subjected to direct and oblique loads were compared initially to obtain the cross section that fulfills the performance criteria. The selection was based on multi-criteria decision making (MCDM) process. The performance parameters used are the absorbed crash energy, crush force efficiency, ease of manufacture and cost. Once the cross section was selected, the design was further enhanced for better crash performances by investigating the effect of foam filling, increasing the wall thickness and by introducing a trigger mechanism. The outcome of the design process was very encouraging as the new design was able to improve the crash performance by an average of 10%.

REGRESSION MODEL FOR LIGHT WEIGHT AND CRASHWORTHINESS ENHANCEMENT DESIGN OF AUTOMOTIVE PARTS IN FRONTAL CAR CRASH

This paper deals with a regression model for light weight and crashworthiness enhancement design of automotive parts in frontal car crash. The ULSAB-AVC model is employed for the crash analysis and effective parts are selected based on the amount of energy absorption during the crash behavior. Finite element analyses are carried out for designated design cases in order to investigate the crashworthiness and weight according to the material and thickness of main energy absorption parts. Based on simulations results, a regression analysis is performed to construct a regression model utilized for light weight and crashworthiness enhancement design of automotive parts. An example for weight reduction of main energy absorption parts demonstrates the validity of a regression model constructed.

STUDY OF AN ENERGY DISSIPATING UNDER-RIDE GUARD USING HARDWARE-IN-THE-LOOP SIMULATION

Hardware-in-the-Loop (HIL) simulation technique is implemented to analyze the performance characteristics of an energy dissipative under-ride guard system for enhancement of crashworthiness of lightweight vehicles involved in coillisions with heavy freight vehicles. The experimental setup, software and hardware interface, and the test methodology used to perform the HIL simulation are briefly described. The energy dissipating under-ride guard, while impacted by a car body, is analytically modeled incorporating nonlinearities due to asymmetric damping in compression and rebound, restoring properties and kinematics of linkages, using the principles of conservation of momentum and Lagrangian dynamics. The performance characteristics of the under-ride guard are evaluated under direct impact at different speeds, and the results obtained from the HIL simulation are compared with those derived from the nonlinear analytical model. The study revealed very good correlation between the analytical and experimental findings in terms of the amount of energy dissipated, acceleration level, rebound velocity and the magnitude of intrusion. An analysis of the results showed that significant portion of the kinetic energy can be dissipated by the under-ride guard.

Post-impact crush of hybrid braided composite tubes

The effect of lateral impact simulating prior damage, on the progressive crush characteristics of 2D-braided composite tubes is investigated. The emphasis of the investigation is on hybridization through the combined use of carbon, glass and/or aramid yarns, as well as through changes in braid yarn yield, and the use of different braid patterns. It is shown that the use of hybrids can lead to significant enhancement of crash-worthiness, and to the development of stable and well-defined damage mechanisms and their influence on characteristics of crush response.

Study of an energy dissipative under-ride guard for enhancement of crashworthiness in a car-truck collision

The performance potentials of a concept of an energy dissipating under-ride guard are investigated under direct and oblique impacts to enhance the crashworthiness of automobiles involved in collisions with heavy freight vehicles. The under-ride guard is analytically modelled incorporating non-linearities due to asymmetric damping, stiffness, clearance spring and kinematics of linkages, using the principle of conservation of momentum and Lagrangian dynamics. Hardware-in-the-loop tests are performed to evaluate the impact energy dissipated by the damper and to verify the proposed model. The analysis is performed for different angles of impact and coefficients of friction between the automobile bumper and the under-ride guard. The performance benefits of the proposed guard at different impact angles are investigated using performance criteria based upon the magnitude of intrusion of the car mass, peak car mass acceleration, and dissipated energy. A multi-variable design optimisation is performed to minimise the magnitude of intrusion and peak acceleration, and maximise the energy dissipated by the damper. The results of the study show that the severity of a crash involving an automobile and a heavy vehicle can be significantly reduced by the proposed guard by: (1) limiting the magnitude of intrusion; and (2) dissipating the part of the crash energy through the damper.