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Friction stir welding (FSW), a solid-state joining process, is commonly used to join Aluminum alloys in aerospace, marine, car industry, and numerous industrial applications. Lightweight materials are commonly used in the transport industry to minimize component weight, and thin-walled structures are increasingly being used as energy-absorbing components in the industry. Even though FSW of plates is well established, FSW of pipe is still at the laboratory level. In this work, FSW for 6063 aluminum alloy pipe has been experimented through a novel procedure and it’s flexural and crashworthiness studies are carried out. The attempt of FSW is performed with a unique welding fixture mounted on a traditional milling machine. The crashworthiness test is conducted to analyze the ability of the structure to nullify the life loss during impact and the crash force efficiency of the pipe is identified. It is further analyzed for the flexural test to identify the bending load of welded aluminum alloy pipes. This study also exposes the basic understanding of the FSW procedure and its metallurgical implications of a friction stir welded pipe.

To better evaluate the crash performance of the guardrail and reduce the number of actual vehicle crash tests, this paper uses mechanical analysis and finite element simulation technology to evaluate the typical movable guardrail and optimize the structure. It’s of great significance for improving the crashworthiness of this type of guardrail and enhancing its safety performance. Firstly, the vehicle-barrier mechanical model was established to calculate the vehicle collision force on the barrier. Secondly, the collision force model was used to calculate the collision of a 10-ton truck, and a finite element model of a typical movable barrier was established for a collision simulation. Finally, the wall thickness and column spacing were optimized according to the results. The simulation results show that the maximum lateral dynamic deformation of the barrier was 1,818 mm, which agrees with the actual vehicle test results (1,600 mm). When the wall thickness of the barrier increases by 2 mm, the maximum lateral dynamic deformation was 1,419 mm; When the spacing of strengthened columns was reduced to 15 m, the deformation was 1,364 mm; After optimization, the deformation was reduced by more than 20%, and the crashworthiness of barrier was improved obviously.

Finite element-based crashworthiness optimization is extensively used to improve the safety of motor vehicles. However, the responses of crash simulations are characterized by a high level of numerical noise, which can hamper the blind use of surrogate-based design optimization methods. It is therefore essential to account for the noise-induced uncertainty when performing optimization. For this purpose, a surrogate, referred to as Non-Deterministic Kriging (NDK), can be used. It models the noise as a non-stationary stochastic process, which is added to a traditional deterministic kriging surrogate. Based on the NDK surrogate, this study proposes an optimization algorithm tailored to account for both epistemic uncertainty, due to the lack of data, and irreducible aleatory uncertainty, due to the simulation noise. The variances are included within an extension of the well-known expected improvement infill criterion referred to as Modified Augmented Expected Improvement (MAEI). Because the proposed optimization scheme requires an estimate of the aleatory variance, it is approximated through a regression kriging, which is iteratively refined. The proposed algorithm is tested on a set of analytical functions and applied to the optimization of an Occupant Restraint System (ORS) during a crash.

An explicit dynamic simulation of the vertical crash of a regional airliner’s middle fuselage section has been conducted to investigate its crashworthiness. The simulation result shows that there a...

For structural bending crashworthiness, previous studies mostly focused on thin-walled tubes with multi-cell cross-sections, while the double-tube configuration was seldom studied. In this paper, the bending crashworthiness of thin-walled tubes with multi-cell and double-tube configurations was compared based on three-point bending tests conducted using the ABAQUS/Explicit code. The numerical results reveal that the reinforcements significantly improve the bending crashworthiness beyond the conventional empty tube according to the two indicators: specific energy absorption (SEA) and crash load efficiency (CLE). For the ratio of cross-sectional width to wall thickness b/t = 100, the double-tube configuration has a similar bending crashworthiness performance to the multi-cell configuration. The asymmetric multi-cell configurations are found to demonstrate more excellent SEA performance than their symmetric counterparts in most cases. For the case b/t = 50, the double-tube configuration significantly prevails over the multi-cell configuration.

Tubular thin-walled structure has attracted more and more attention because of its light weight and energy absorption characteristic, and has been widely applied to the fields of aerospace and auto...

Objective The objective of this study was to generate functional forms of brain injury risk curves using the National Automotive Sample System Crashworthiness Data System's (NASS-CDS) database for the years of 2001-2015. The population of interest was near-side occupants who experienced a direct head impact with an injury source located lateral to a typical seated position. Methods Brain injuries were restricted to Abbreviated Injury Scale (AIS) 2005 Update 2008 defined concussions and internal organ injuries of the head. Near-side occupants comprised two major groups, both of which were required to have evidence of head contact (i.e., a head injury with DIRINJ = 1 and SOUCON = 1 or 2): brain injured occupants (MAIS1, MAIS2, MAIS3+) and non-brain injured occupants with some other direct contact head injury (MAIS0). Analyzed cases were required to have an indication of a reasonable crash reconstruction. Injury sources allowed within the final sample consisted of A-pillars, B-pillars, roof/roof rails, impacting vehicles/exterior objects, other components of the vehicle's side interior, and other occupants or otherwise unspecified interior objects. Risk curves for occupants with brain injury severities of MAIS0, MAIS1+, MAIS2+, and MAIS3+ were generated using multivariate stepwise logistic regressions. Investigated predictors involved vehicle change in velocity, seat belt use, principal direction of force (PDOF), and injury source type (B-pillar and side window). Results Multivariate stepwise logistic regressions identified significant predictors of lateral change in velocity (dvlat) for all injury severity categories, and side window injury source (INJSOU = 56, 57, 58, 106, and 107) for MAIS0 and MAIS1+ risk curves. Although model sensitivity decreased for more severe injury predictions, risk curves dependent on only dvlat yielded accuracies of 70% for all presented models. Conclusions Real world crashes are often complex and lack the benefit of real time monitoring; however, NASS-CDS post-crash investigations provide data useful for injury risk prediction. Further analysis is needed to determine the effect of data confidence, injury source, and accident sequence restrictions on NASS-CDS sampling biases. The presented models likely favor a more conservative risk prediction due to the limitations of NASS-CDS data collection, AIS code conversion, and unweighted sample analysis.

Many hierarchical structures have good mechanical properties, which can better improve the energy absorption characteristics and achieve lightweight. This article proposed a novel circumferential s...

The battery packs are crucial components of electric vehicles and may severely affect the continue voyage course and vehicle safety. Therefore, design optimization of the battery-pack enclosure (BPE) is critical for enhanced mechanical and crashwrothiness performances. In this study, a lightweight design of an automotive BPE under the loading conditions is presented based on the advanced high-strength steels (AHSSs) and size optimization. A numerical analysis procedure is also introduced for the lightweight design. First of all, a nonlinear finite element (FE) BPE model was established and validated through the modal test. Secondly, the random vibration simulation was performed based on the sensitivity analysis to initially determine the AHSSs and thickness for the components of the BPE. Next, the material and thickness were determined by the fixed-frequency vibration analysis. Moreover, the mechanical shock and fatigue life were analyzed numerically. Finally, the crashworthiness of the optimized BPE model was verified by crash and crush simulations. The results show that the optimized BPE structure has a 10.41 % lightweight gain, while assuring enhanced dynamic performances. The introduced numerical procedure could be used to quickly determine the material and thickness of each component of BPE. The design optimization process was found beneficial to reduce the number of physical tests and product development cost and shorten product development cycles.

Frontal impacts are the most frequent crash types and may generate extreme body in white (BIW) deformations. Vehicles are subjected to impact evaluation rating protocols such as 100 % Front Rigid Barrier (FRB) impact, 40 % Offset Deformable Barrier (ODB) impact and 25 % overlap (small overlap) impact. This paper proposes a collaborative optimization process using optimal Latin hypercube design (Opt LHD) and response surface methodology (RSM), to improve the vehicle crashworthiness in the frontal impacts, by considering displacement oriented structure (DOS). Upper and lower engine bay structure were considered herein to increase the lateral vehicle displacement during small overlap impact and decrease the impact force that transferred to the passenger compartment in the frontal impacts. The optimal results indicated that the acceleration of the B-pillar was reduced 0.4g in the FRB impact, the intrusion of the firewall was reduced by 55.13 % in the ODB impact, and the intrusion of passenger compartment during small overlap impact was decreased by an average of 53.88 %, with a maximum percentage of 71.41 % around left toepan, leading to an IIHS rating to acceptable from poor. The proposed crashworthiness design approach is effective in vehicle structure optimization for better frontal impacts performance.

In the automotive structure, there are different components that utilise aluminium alloy (AA) sheets and it is used widely in the car body-in-white which comprise bumpers and the crash box structure at the front end of the car which specifically designed to withstand the event of collision. As the structures are also experiencing dynamic loading, it were also a concern for the structures to show satisfied modal properties. In this study, the modal properties of the crash box structures are investigated along with the effect of the modal properties towards the crashworthiness behaviour of the structure itself with the approach of finite element analysis. Experimental modal analysis was also done to further validating the finite element analysis of the modal properties. Three different designs of trigger mechanisms are applied towards the crash box structure to observe on both findings. For the connector element, equivalent nodes of both parts of the crash box structures are used. For the results, the correlation from both findings did show that the presence of trigger mechanism did decreased the magnitude of natural frequencies as well as the mode shape as shown by crash box type 3 by 9.50% and for the crashworthiness output, the crashworthiness behaviour of the crash box with trigger mechanisms were better in term of the collisions phases indicated by the primary peak force and the secondary peak force from the force-displacement curve as also shown by crash box structure type 3 with the percentage of 22.59%. The study does shows that the stiffness and mass distribution due to the presence of trigger mechanism do affect the modal properties of a structure as well as its crashworthiness output.

The continuing efforts of automotive technology aim to deliver even greater safety benefits and reduce the weight of a vehicle. Thin-walled beams (TWB) are widely used as strengtheners or energy absorbers in vehicle bodies due to their lightweight and excellent energy absorption capacity. Thus, researchers are interested in the collapse behaviour and mechanical properties of thin-walled beams under static and dynamic loadings. Circular TWB is commonly used in vehicle side doors. In the event of a side collision, this beam deforms and absorbs the greatest amount of impact energy. In this study, the energy absorption capability and crashworthiness of polygonal cross-section TWBs subjected to lateral impact was investigated using numerical simulations. Polygonal TWB ranging from square to dodecagon, as well as circular cross section, were selected for this study. Energy absorption (EA), specific energy absorption (SEA) and crash force efficiency (CFE) crashworthiness indicators are employed to evaluate the bending collapse performance. Because TWB thickness and weight have a greater impact on bending performance, they were kept constant across all polygons. In ABAQUS explicit dynamic software, finite element simulations are performed, and plastic hinges and flattening patterns of all polygons are examined. The results show that heptagon, octagon, and nonagon cross-section TWB perform better in crashworthiness than square and circular TWB.

Porous aluminum (Al) composites are lightweight and high-strength materials composing of Al as a matrix material with some strengthening reinforcements and pore-forming agents that result in the formation of new material with superior physical properties and energy absorption capacities. This work gives an overview of the porous Al-foams developed thus far, including the foaming agents and space holders, their properties, production techniques, and applications. First, it deliberates the foaming agents and space holders responsible for the foaming and formation of pores in the composites followed by the mechanical properties of the foams. Al has huge potential for applications that require lightweight, high-strength, and high-energy absorption capacity materials, especially in structural construction and automobile manufacturing. Although Al-foams have been successfully used in automobiles for crashworthiness, lightweight structure, and other functional applications, the development of Al foams with enhanced characteristics and properties has limitations. This review discusses various reinforcements used for improving the characteristics of Al-foams. This review also provides an overview of various commercial foams and their contribution to several applications. Finally, it attempts to reveal impediments in foam production with suggested solutions for overcoming the problems in this area.

Due to the low manufacture cost and easy installation, tubal structures are common utilized as energy absorbers in automotive and other engineering industries. In the present work, four novel reinf...

Thin-walled tubes are widely used as energy absorbers due to their high crashworthiness performance. This study aims to evaluate the effect of plastic forming history carried out for thickness optimization on crashworthiness performance of thin-walled square tube (TWST). Within the scope of the study, a series of numerical analyses were conducted for the TWST using a commercial finite element (FE) software. In order to determine individual effect of optimization, FG thickness of TWST was first obtained using LS-OPT software. Later, thickness gradient was achieved by performing rolling process to consider individual plastic forming effect Afterwards, deep drawing process was carried out to shape TWST by considering springback and trimming effects. Finally, crash responses were obtained under axial high velocity impact loading to determine the coupled effect of optimization and plastic forming on the crashworthiness performance of the TWST. It was determined that the coupled effect, which takes plastic forming and optimization effects into account, reduced the peak crush force of the TWST by 24% and increased the absorbed energy value by 39%. The results obtained from this study showed that coupled effect of optimization and plastic forming processes has significant effect on the crashworthiness performance of the TWST and otherwise either overestimated or underestimated results are obtained.

Objective: Automated driving systems (ADS) are actively being deployed within the driving fleet. ADS are designed to safely navigate roadways, which entails an expectation of encountering varying degrees of potential conflict with other road users. The ADS design and evaluation process benefits from estimating injury severity probabilities for collisions that may occur. Current regression models in the literature are typically bespoke analyses involving targeted principal directions of force (PDOFs) and occupant positions. It is preferable to rely on injury severity models derived from a single source to provide a continuous function of risk for all planar collisions, while also accounting for specific vehicle and occupant characteristics. The novel feature of the proposed models is continuous, parametric injury risk surfaces that encompass the full spectrum of available United States field data. Methods: We used years 2001���2015 of the National Automotive Sampling System, Crashworthiness Data System (NASS-CDS) and years 2017���2019 of the Crash Investigation Sampling System (CISS) to estimate injury risk at the maximum abbreviated injury scale (MAIS) 3 and higher (3+) and 5 and higher (5+) levels for all adult occupants traveling in 2002 or newer passenger vehicles which were less than 10 years old at the time of the crash. The models account for occupant, vehicle, and crash characteristics. Interactions with vulnerable road users (e.g., pedestrian, bicyclist) were not considered. Results: We present statistical models suitable to predict injury in all non-rollover crashes at the maximum MAIS3+ and 5+ levels, and show that these models can be comparable to similar single scenario (e.g., frontal) crash models. We discuss challenges with imputing missing field data, and discuss handling of covariates that may not be known at the time of the crash. Conclusions: Collision severity assessment is a vital component of the ADS design process. We developed a novel injury risk function that can assess occupant injury risks across the spectrum of foreseeable planar collisions. These models can provide insight on potential outcomes of counterfactual simulations, injury risk and crashworthiness considerations for human driven vehicles, and provide an evaluation tool that can be applied in ADS safety impact evaluation.

OBJECTIVE The Insurance Institute for Highway Safety (IIHS) introduced its side impact ratings test in 2003. Despite manufacturers' improvements to airbags and vehicle structures, 45% of 2018 side crash fatalities on U.S. roadways were in good-rated vehicles, suggesting that more crashworthiness improvements are necessary. Crash trends indicate that the most promising avenue to address the remaining real-world injuries is a higher severity vehicle-to-vehicle test using a barrier to represent a striking sport-utility vehicle (SUV). Laboratory tests comparing striking SUVs with the current IIHS moving deformable barrier (MDB) showed discrepancies in damage patterns and injury measures. The current study outlines the characteristics of a multi-stiffness aluminum honeycomb barrier to represent a modern SUV-striking vehicle in side impact crash tests. METHODS Barrier size and shape were determined from a series of measurements taken from 21 modern SUVs. Barrier honeycomb stiffness characteristics were derived by comparing the damage profile of six different barrier prototypes against a baseline profile obtained from a high-severity SUV crash into a midsize car. Tests were conducted at 60 km/h with a 1,900 kg MDB. The best honeycomb design was tested against four additional vehicles to ensure it was representative of striking SUVs of different sizes and types. RESULTS The final barrier has a 1,700-mm width by 600-mm height and 500-mm depth multi-stiffness design, with less stiffness on the top and more stiffness in the lower outside sections compared with the original IIHS barrier. For three struck vehicles, the redesigned barrier matched all performance criteria set by the striking-SUV tests. For two additional struck vehicles, there were some differences in intrusion patterns but overall, these matched the test trends of the striking SUVs. The new barrier in a higher severity test mode resulted in a range of performance for these good-rated vehicles. CONCLUSION A multi-stiffness aluminum honeycomb barrier was developed to represent the characteristics of striking SUVs in 60 km/h perpendicular side impact crash tests focusing on the occupant compartment. The redesigned barrier differentiates between currently good-rated vehicles, which will promote structural and restraint system improvements to the fleet relevant to the remaining real-world injuries.

An energy absorbing tube combining multi-corner and multi-cell configurations was designed in this study. Machine learning was adopted to predict and optimize the crashworthiness of the proposed tu...

The bending crashworthiness performance of thin-walled structures is affected by several factors such as the end-clamping constraints. The end-clamping configuration should be carefully investigated since it is an important part of the real working condition of a structure under bending loading. End-clamping fixtures (pads) can be used intentionally as complementary energy dissipating mechanisms to trigger new plastic deformation. The present article explores the use of pads to improve the crashworthiness of square tubes under lateral loads. For this purpose, internal, external, and combined pads were located at the profile ends which were subjected to a modified three-point bending test using finite element simulations. The effect of assembly force (fN) and pad length (lp) on the energy absorption was investigated. The structures were made of aluminum 6063-T5 and modeled with elasto-plastic properties considering ductile and shear damage criteria with evolution. Additionally, the numerical results were validated by an experimental three-point bending test on a square profile with constrained and free ends. Our results for a structure with end-clamping fixtures show an improvement of crashworthiness performance in a range from 42.38 – 57.89% relative to a structure with free-ends. The best crush force efficiency (CFE) of 0.78 was obtained when external pads were implemented. Moreover, the importance of fN on the end-clamping pads was noticed since CFE is increased by 9.30% when a normalized force of 0.109 is applied. The importance of pad length was also demonstrated. An improvement of 69.38% in CFE was achieved when a normalized length $$ {\overline{L}}_p $$ = 0.138 was implemented. Finally, with the findings of our work, a design of end-clamping fixtures for an automobile’s side-door impact beam is presented and analyzed.

In this paper, the effects of various design options for improving the crashworthiness performance of a rectangular crash absorber with diaphragms are explored. These design options include (i) optimal tube and diaphragm dimensioning, (ii) optimal diaphragm placement, and (iii) tapering of the crash absorber. The wall thicknesses of the absorber and the diaphragms, the locations of the diaphragms, and the taper angle are taken as design variables to optimize the crashworthiness performance of the absorber. Before the optimization study, a finite element model is generated and validated with experimental results available in the literature. The effect of each design variable on crashworthiness performance is evaluated by solving a series of design optimization problems, and compared with the baseline design. A successive iterative approach is used in this study, where the optimum design variables obtained from a previous optimization problem are used as the initial design of the next optimization problem. Maximum specific energy absorption (SEA) is sought in these optimization problems. A surrogate-based optimization approach is used, where radial basis functions and response surface models are utilized. Optimal tube and diaphragm dimensioning resulted in 59.2% increase, optimum diaphragm placement led to 7.7% additional increase, and tapering resulted in 2.5% further increase in SEA. Overall, the design changes considered in this paper provided 69.4% increase in SEA.

This paper takes into consideration the excellent energy absorption ability of hierarchical honeycombs and auxetic structures and proposes a novel auxetic hierarchical crash box assembled by the auxetic hierarchical filling cores and the outer square thin-walled tube. The crushing performance of the auxetic hierarchical crash box is systematically investigated. The comparisons of energy absorption ability are made among the auxetic hierarchical crash box, aluminum foam-filled crash box, and the traditional crash box. In addition, a multi-objective optimization design is conducted based on the surrogate model with higher accuracy. The non-dominated sorting genetic algorithm (NSGA-II) and archive-based micro genetic algorithm (AMGA) are, respectively, employed to obtain the pareto sets. The results show that the optimum solution with AMGA has a smaller relative error, and the multi-objective optimization successfully improves the crushing performance of the auxetic hierarchical crash box. The electric vehicle crashworthiness is remarkably improved by the application of the auxetic hierarchical crash box. The conclusions of this paper can provide a new solution for the design of the crash box.

New products based on a structure that represents a combination of known elements in a higher quality set, as well as products that refer to new shapes, new curves, new surfaces can be obtained logically - analytically - deductively or by methods specific to the optimal calculation. The present paper focuses on the method of analyzing tridimensional morphology, some possible solutions being evaluated on value criteria. Of course, these methods can be applied in the field of engineering with very good results. The focus of this study is to obtain new thin walled tubular structures - such as car crash members - which in the case of axial shock loads have a higher predictable behavior compared to those already used in various technical fields. Following the study, it can be said that depending on the amount of absorbed energy in the case of axial collisions and the absorption of kinetic energy developed at the time of impact, the optimal crashworthiness solution could be tubular structures with a circular support base and rectangular deformable area for impact.

Multi-wall profile as one of the most widely approaches can enhance the crashworthiness properties in thin-walled tubular structures. In actual application process as energy absorbers, there may be...

Introduction: With the growing older adult population due to the aging baby-boom cohort, there was concern that increases in fatal motor-vehicle crashes would follow. Yet, previous analyses showed this to be untrue. The purpose of this study was to examine current trends to determine if previous declines have persisted or risen with the recent increase in fatalities nationwide. Methods: Trends among drivers ages 70 and older were compared with drivers 35–54 for U.S. passenger vehicle fatal crash involvements per 100,000 licensed drivers from 1997 to 2018, fatal and all police-reported crash involvements per vehicle miles traveled using the 1995, 2001, 2009, and 2017 National Household Travel Surveys, and driver deaths per 1,000 crashes. Results: Since the mid-1990s, fatal crashes per licensed driver trended downward, with greater declines for drivers ages 70 and older than for middle-aged drivers (43% vs. 21%). Fatal crash rates per 100,000 licensed drivers and police-reported crash rates per mile traveled for drivers ages 70–79 are now less than those for drivers ages 35–54, but their fatal crash rates per mile traveled and risk of dying in a crash remain higher as they drive fewer miles. As the economy improved over the past decade, fatal crash rates increased substantially for middle-aged drivers but decreased or remained stable among older driver age groups. Conclusions: Fatal crash involvements for adults ages 70 and older has recently increased, but they remain down from their 1997 peak, even as the number of licensed older drivers and the miles they drive have increased. Health improvements likely contributed to long-term reductions in fatal crash rates. As older drivers adopt vehicles with improved crashworthiness and safety features, crash survivability will improve. Practical Application: Older adults should feel confident that their independent mobility needs pose less risk than previously expected.

During a side impact accident of an automobile, the automobile threshold plays an important role in maintaining the living space of passengers, and thus the crashworthiness design of thresholds may...

This paper proposes a new type of energy absorber with combined shrinking circular tubes for a high-speed train. An impact experiment is conducted to investigate the dynamic crushing performance of this energy absorber with combined shrinking circular tubes. The results show that the combined tubes experience steady dynamic shrinking deformation. Finite element (FE) models of the energy absorber are then developed, and the dynamic crushing forces are in good agreement with the impact test. A theoretical solution for the dynamic shrinking crushing load is derived. Based on the validated FE models, the effects of the friction coefficient, wall thickness and die radius on the dynamic crushing force and energy absorption are investigated. An increase in the wall thickness leads to a substantial growth in the maximum crushing force (Fmax) and specific energy absorption (SEA), but the growth rate of Fmax is much larger than that of the SEA as the wall thickness increases. In addition, comparing theoretical and FE results demonstrates that predictions of the dynamic steady-state forces for the combined shrinking circular tubes with different friction coefficients, wall thicknesses (t) and die radius (Rdie) are satisfactory. Finally, to improve the crashworthiness of the expanding circular tubes, Sobol’ sensitivity analysis is employed to analyze the effects of the design parameters (t and Rdie) on the objective responses (SEA and Fmax) using the Kriging model. A Pareto front of double optimization objective SEA and Fmax was obtained after being optimized by multiobjective particle swarm optimization (MOPSO). The results show that SEA and Fmax are positively correlated, and a balance between the SEA and Fmax was obtained at optimal point C (SEA = 13.09 kJ/kg, Fmax = 581.11 kN).

The proportion of electric vehicles in vehicle manufacturing is increasing, but with the endurance mileage of the battery improved, the collision safety problem of electric vehicles is becoming more prominent. To solve a multi-objective robust design problem with discrete variables for vehicle collision design, we propose the Grey-Taguchi robust optimization method. The Grey-Taguchi method transforms the multi-objective functions into a single grey relation grade sequence instead of the signal-noises ratio used in Taguchi and selects the optimal combination of design variables predicted by the minimum design of experimental and the analysis of means. For the vehicle crashworthiness problem, the Grey-Taguchi method can converge to the Pareto front with several iterations. The mass of frame, maximum lateral intrusion, and peak deceleration after the optimization are decreased 14.5 %, 32.3 %, and 17.8 %, respectively. The Grey-Taguchi robust optimization method can not only enhance the robustness of the optimization design but also improve the lightweight design performance and crashworthiness. The proposed method is considered promising for complex engineering design problems with multi-objectives and discrete design variables.

Advanced high-strength steels have been widely used to improve the crashworthiness and lightweight of vehicles. Different from the popular cold stamping, hot forming of boron-alloyed manganese steels, such as 22MnB5, could produce ultra-high-strength steel parts without springback and with accurate control of dimensions. Moreover, hot-formed medium-Mn steels could have many advantages, including better mechanical properties and lower production cost, over hot-formed 22MnB5. This paper reviews the hot forming process in the automotive industry, hot-formed steel grades, and medium-Mn steel grades and their application in hot forming in depth. In particular, the adaptabilities of medium-Mn steels and the presently popular 22MnB5 into hot forming were compared thoroughly. Future research should focus on the technological issues encountered in hot forming of medium-Mn steels to promote their commercialization.

A novel two-dimensional (2D) mechanical metamaterial with highly programmable mechanical response under compressive load is presented in this paper by introducing hierarchical rotating structures, in which flexible structures are used to replace the rigid part in conventional rotating rigid structures. Multi-step deformation pathways and negative Poisson’s ratio were observed in in situ compression experiments and finite element simulations, suggesting that the mechanical behavior of the hierarchical metastructure is highly ordered and can be programmed by constraining angles of the proposed metamaterial. This work offers new insights to create mechanical metamaterial using hierarchical rotating structures for flexible devices and crashworthiness applications.

Aiming at reducing the energy absorption of the hydrogen cylinder for fuel cell vehicles in collision, which may lead to fierce explosion, this paper introduces an energy-absorbing protective shell combining with negative Poisson’s ratio (NPR) structure to the hydrogen cylinder. It adopts three honeycomb structures of the same mass and three kinds of aluminum alloy to determine the optimal structure and material scheme of the protective shell. Besides, sensitivity analysis is selected to screen the design parameters of the optimal structure scheme. Based on this, the overall mass of the designed protective shell, the specific energy absorption of NPR structure, the maximum impact force of rigid wall, and the maximum stress of the liner are taken to establish the optimization mathematical model. Furthermore, adaptive mutation genetic algorithm (AMGA), non-dominated sorting genetic algorithm-ii (NSGA-II), and adaptive simulated annealing algorithm (ASA) are exerted as the optimization algorithms separately to conduct optimization design and a comparison is made between the optimization results. The results show that the optimized energy-absorbing protective shell has better crashworthiness and energy absorption effect, which can effectively improve the collision safety of the hydrogen cylinder. It provides a new idea for the protection design of hydrogen storage system in fuel cells in the future.

In this paper, the crashworthiness characteristics of tapered structures with the uniform cells in cross-section subjected to oblique impacts are theoretically and numerically investigated. Benefit...

This study focuses on the axial and oblique low-velocity impact response of thin-walled aluminium conical frusta with circular cutouts at two different locations through experimental and finite ele...

This work deals with the development of an improved numerical model, based on the explicit finite element method, aimed at investigating the energy absorption capabilities of a full-scale composite...

Recently, multi-cell structures have received increased attention for crashworthiness applications due to their superior energy absorption capability. However, such structures were featured with high peak collapsing force (PCL) forming a serious safety concern, and this limited their application for vehicle structures. Accordingly, this paper proposes windowed shaped cuttings as a mechanism to reduce the high PCL of the multi-cell hexagonal tubes and systemically investigates the axial crushing of different windowed multi-cell tubes and also seeks for their optimal crashworthiness design. Three different multi-cell configurations were constructed using wall-to-wall (WTW) and corner-to-corner (CTC) connection webs. Validated finite element models were generated using explicit finite element code, LS-DYNA, and were used to run crush simulations on the studied structures. The crashworthiness responses of the multi-cell standard tubes (STs), i.e., without windows, and multi-cell windowed tubes (WTs) were determined and compared. The WTW connection type was found to be more effective for STs and less favorable for WTs. Design of experiments (DoE), response surface methodology (RSM), and multiple objective particle swarm optimization (MOPSO) tools were employed to find the optimal designs of the different STs and WTs. Furthermore, parametric analysis was conducted to uncover the effects of key geometrical parameters on the main crashworthiness responses of all studied structures. The windowed cuttings were found to be able to slightly reduce the PCL of the multi-cell tubes, but this reduction was associated with a major negative implication on their energy absorption capability. This work provides useful insights on designing effective multi-cell structures suitable for vehicle crashworthiness applications.

Hot stamping, also known as press hardening in the context of sheet steel, has steadily gained relevance in the automotive industry, starting off as a specialist application and turning into a staple technique in the production of safety cage products in little more than a decade. However, despite the weight reduction offered by martensitic steels, further improvement could be obtained by substituting these components by high-performance aluminium. In this regard, the very same process of hot stamping could be employed to attain the required combination of shape complexity and mechanical properties at a reasonable cost for mass-market application, if the limitations imposed by cycle time and process window could be overcome. In this work, the feasibility of hot stamping of 6000-series aluminium alloy sheet is studied, first in dilatometry experiments and later in semi-industrial conditions in a pilot facility. A cycle time shortening strategy is employed, and compared to the conventional thermal cycle in terms of implementation and obtained results. In addition to basic characterization, aluminium thus processed is studied in terms of fracture toughness, in order to obtain data relevant to crashworthiness that can be readily compared with alternative materials.

Energy absorbers are deformable or made to deform, they are considered important so that they absorb the impact energy. In case of frontal collisions, it is expected to deform and absorb crash energy which can be transferred to other parts is minimized. Hence, designing process of such energy absorbers should maintain the peak force below an allowable threshold. Various materials for energy absorbers are explored and their energy absorption ability and geometry is studied. Experimental analysis includes tests on various machines and its S.E.A is done. In order to improve overall design specifications biomimetic concepts are utilized. Biomimetic structures are also are confronted. According to requirement design and analysis of energy absorbers in the vehicle is done using the computational simulation software’s

Glass fabric epoxy polymer composites are recognized as one of the efficient material for energy absorbing components, owing to their extremely dissipative crushing mechanisms involved during collisions. As a result, in addition to their light weight characteristics combined with attractive mechanical properties, they are employed in various domains such as automobile, railway, aerospace and marine industries etc. The present research paper aims to present the axial crashworthiness performance of thin-walled bi-tubular composite structures under impact load. The successfully manufactured composite bi-tubular components were imposed to axial impact loading with varied impact velocity of 8 m/s and 10 m/s. The SEA of eight layered glass fabric epoxy polymer composite square tubes are 5–35% significantly higher than the four layered glass fabric composite square tubes and can be used as a good alternative to the conventional single square tubes.

The proportion of motor vehicle crash deaths involving a collision with fixed objects is not decreasing. To address this issue and consequently to decrease transportation hazards, a novel crash cushion comprised of load-bearing blocks was introduced. Its alpha version is easily and inexpensively obtainable; the beta version is suitable for use in harsh environments. In this contribution, the effect of the collision on imaginary vehicle passengers is examined. Besides, the effect of impact velocity on collision severity is discussed and both versions of crash cushions are compared in occupant injury potential. The effect of a combination of crash cushions with different crashworthiness measures is also studied. Inferences drawn from this study can be used by designers and contractors to assess the collision severity and optimize the use of the cushioning elements. The presented cushioning elements can replace stones and solid blocks in cross-drainage culverts, but hypothetically they could also be used in other structures which pose risks around traffic lanes or in underwater protection of bridge piers.

Highlights Rollovers are the leading cause of injury and fatality in farm all-terrain vehicle (ATV) incidents. Engineering technologies to prevent rollovers or protect the operator in ATV crashes were reviewed in this study. The advances in safety for ATVs are correlated with improvements in stability, handling, and crashworthiness. Operator protection devices and crash notification systems can protect the operator in ATV rollover incidents. Abstract . All-terrain vehicles (ATVs) are the second most common source of injury, following tractors, in U.S. agriculture. Rollovers are the leading cause of death in farm ATV incidents, constituting about 85% of ATV-related deaths. There is neither a significant practical solution for ATV rollover crashes in the U.S. nor standards and rules for implementing such a solution. Behavior-based control methods have been used for several decades but have reached their limit of success. Hence, engineering controls are needed to significantly decrease the severity of injuries in ATV rollover incidents (as in tractor incidents). In this study, engineering technologies to protect the operator in agricultural ATV crashes were reviewed. The discussion includes improving crash testing and stability ratings, evaluating static stability of ATVs, dynamic handling tests of ATVs, using automatic systems to notify first responders of a crash, and testing and applying operator protection devices. The available standards, rules, and recommendations related to these technologies around the world are also discussed. Keywords: . Agriculture, All-terrain vehicle, ATV, CPD, Crush protection device, OPD, Quad bike, Safety.

The results of the crashworthiness assessment under grounding scenarios are presented in the previous part of this two-part companion paper. This part presents results from numerical analyses with focus on structural performance accounting for seabed topology, and investigation of energy formulae for application in calculation of grounding damage. Study in this work is divided into three stages, i.e. finite element method (FEM) verification using laboratory experiment, numerical calculation of ship grounding using FEM, and comparison of the FEM results with empirical formulae of damage-energy calculation. Fundamental formula of Minorsky is considered with other improvement expression, such as Woisin and Zhang. Investigation suggested that the recent-developed expression produces the closest estimation to the verified FEM results. On the other hand, fundamental formulae of Minorsky is the farthest compared to the FEM, which indicates constant value in the expression needs to be more specific as improved in the Woisin formula.

Composite materials are being widely used in automobile industry in order to meet the ever increasing demand to achieve significant weight reduction by maintaining the performance levels. Additiona...

In crash event, aerospace structures are designed to collapse progressively, dissipating high kinetic energy and protecting the passengers against abrupt decelerations. To achieve this goal, a bett...

With the development of aircraft industry, there is an urgent demand for pursuing higher crashworthiness design standard of fuselage. However, there is a challenge for improving the crush performan...

A constitutive damage model is proposed in order to investigate the crushing response of crossply and 0 ° plies composite laminates, using a VUMAT subroutine implemented in ABAQUS/Explicit. This da...