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2017-03-28
Technical Paper
2017-01-1473
Ling Zheng, Yinan Gao, Zhenfei Zhan, Yinong Li
Abstract Several surrogate models such as response surface model and radial basis function and Kriging models are developed to speed the optimization design of vehicle body and improve the vehicle crashworthiness. The error analysis is used to investigate the accuracy of different surrogate models. Furthermore, the Kriging model is used to fit the model of B-pillar acceleration and foot well intrusion. The response surface model is used to fit the model of the entire vehicle mass. These models are further used to calculate the acceleration response in B-pillar, foot well intrusion and vehicle mass instead of the finite element model in the optimization design of vehicle crashworthiness. A multi-objective optimization problem is formulated in order to improve vehicle safety performance and keep its light weight. The particle swarm method is used to solve the proposed multi-objective optimization problem.
2017-03-28
Technical Paper
2017-01-1468
Do Hoi KIm
Previous work identified a relationship between vehicle drop and dummy injury under the high-speed frontal impact condition [1]. The results showed that vehicle drop greater than 60mm made the dummy injury worse. Moreover, that work identified the front side member as the crucial part affecting the vehicle drop. In this study, the body structure mechanism was studied to reduce vehicle drop by controlling the front side member, shotgun, and A-pillar. By analyzing full vehicles, it was recognized that the arch shape of the front side member was very important. Furthermore, if the top of the arch shape of front side member, shotgun, and A-pillar were connected well, then the body deformation energy could lift the lower part of A-pillar, effectively reducing vehicle drop. This structure design concept is named “Body Lift Structure” (BLS). The BLS was applied to B and C segment platforms. Additionally, a “Ring” shape was defined by the front side member, dash panel, and A-pillar.
2017-03-28
Journal Article
2017-01-1463
Xianping Du, Feng Zhu, Clifford C. Chou
Abstract A new design methodology based on data mining theory has been proposed and used in the vehicle crashworthiness design. The method allows exploring the big dataset of crash simulations to discover the underlying complicated relationships between response and design variables, and derive design rules based on the structural response to make decisions towards the component design. An S-shaped beam is used as an example to demonstrate the performance of this method. A large amount of simulations are conducted and the results form a big dataset. The dataset is then mined to build a decision tree. Based on the decision tree, the interrelationship among the geometric design variables are revealed, and then the design rules are derived to produce the design cases with good energy absorbing capacity. The accuracy of this method is verified by comparing the data mining model prediction and simulation data.
2017-03-28
Technical Paper
2017-01-1466
Claudia De La Torre, Ravi Tangirala, Michael Guerrero, Andreas Sprick
Abstract Studies in the EU and the USA found higher deformation and occupant injuries in frontal crashes when the vehicle was loaded outboard (frontal crashes with a small overlap). Due to that, in 2012 the IIHS began to evaluate the small overlap front crashworthiness in order to solve this problem.A set of small overlap tests were carried out at IDIADA’s (Institute of Applied Automotive Research ) passive safety laboratory and the importance of identifying the forces applied in each structural element involved in small overlap crash were determined. One of the most important structural elements in the small overlap test is the wheel. Its interaction in a small overlap crash can modify the vehicle interaction at the crash, which at the laboratory the interaction is with a barrier. That interaction has a big influence at the vehicle development and design strategy.
2017-03-28
Technical Paper
2017-01-0476
Seiji Furusako, Masatoshi Tokunaga, Masanori Yasuyama
Abstract To reduce the weight of automobile bodies, application of high-strength steel sheets is expanding. Furthermore, middle and high carbon steels are expected to be used to lower the environmental impact and cost in the automobile steel sheet industry. However, it is necessary to enhance the joint strength of the steel sheets. In this study, hat-shaped components were made using resistance spot (RS) welding or arc spot (AS) welding on S45C steel sheets (including 0.44% carbon), 1.4 mm thickness and strength of 1180 MPa grade. A dynamic three-point bending test was conducted on the components and their crashworthiness was compared. Some RS welds fractured (separated) during the three-point bending test even though the diameter of the weld metal was increased to 5√t (t means thickness of the sheet); however, AS welds did not fracture.
2017-03-28
Technical Paper
2017-01-0264
Venkatesh Babu, Ravi Thyagarajan, Jaisankar Ramalingam
Abstract In this paper, the capability of three methods of modelling detonation of high explosives (HE) buried in soil viz., (1) coupled discrete element & particle gas methods (DEM-PGM) (2) Structured - Arbitrary Lagrangian-Eulerian (S-ALE), and (3) Arbitrary Lagrangian-Eulerian (ALE), are investigated. The ALE method of modeling the effects of buried charges in soil is well known and widely used in blast simulations today [1]. Due to high computational costs, inconsistent robustness and long run times, alternate modeling methods such as Smoothed Particle Hydrodynamics (SPH) [2, 9] and DEM are gaining more traction. In all these methods, accuracy of the analysis relies not only on the fidelity of the soil and high explosive models but also on the robustness of fluid-structure interaction. These high-fidelity models are also useful in generating fast running models (FRM) useful for rapid generation of blast simulation results of acceptable accuracy.
2017-03-28
Technical Paper
2017-01-1272
Nick Parson, Jerome Fourmann, Jean-Francois Beland
Abstract One of the main applications for aluminum extrusions in the automotive sector is crash structures including crash rails, crash cans, bumpers and structural body components. The objective is usually to optimize the energy absorption capability for a given structure weight. The ability to extrude thin wall multi-void extrusions contributes to this goal. However, the alloy used also plays a significant role in terms of the ability to produce the required geometry, strength - which to a large extent controls the energy absorption capability and the “ductility” or fracture behavior which controls the strain that can be applied locally during crush deformation before cracking. This paper describes results of a test program to examine the crush behavior of a range of alloys typically supplied for automotive applications as a function of processing parameters including artificial ageing and quench rate.
2017-03-28
Technical Paper
2017-01-1301
Deepak A. Patil, Hrishikesh Buddhe
Abstract Frontal collisions account for majority of car accidents. Various measures have been taken by the automotive OEMs’ with regards to passive safety. Honeycomb meso-structural inserts in the front bumper have been suggested to enhance the energy absorption of the front structure which is favorable for passive safety. This paper presents the changes in energy absorption capacity of hexagonal honeycomb structures with varying cellular geometries; under frontal impact simulations. Honeycomb cellular metamaterial structure offers many distinct advantages over homogenous materials since their effective material properties depend on both, their constituent material properties and their cell geometric configurations. The effective static mechanical properties such as; the modulus of elasticity, modulus of rigidity and Poisson’s ratio of the honeycomb cellular meso-structures are controlled by variations in their cellular geometry.
2017-01-10
Technical Paper
2017-26-0017
Celine Adalian, Alba Fornells, Núria Parera
Abstract In the 70’s, to reduce vehicle crash fatalities, NHTSA launched a Program, called NCAP, to compare the safety of cars. This Program was copied in Europe and around the world. It has been demonstrated that this kind of public assessment has forced OEM’s to invest in safety and to develop safer vehicles. Nowadays, NCAPs exist for nearly all regions around the world; all of them with the aim of improving vehicle safety. They apply the philosophy of an “overall rating”. In that way the information aims to be clearer and more general and will help to compare cars. Nevertheless, even though in every NCAP the overall assessment is given by a unique star rating, the specifications and requirements in each protocol are different. Each NCAP has been adapted to each region’s conditions, accidentology and traffic and therefore assessment criteria have their own peculiarities.
2017-01-10
Technical Paper
2017-26-0009
Abhinab Mohanty, Rajasekar Ramaraj, Prashant Dhage, Alok Kumar Ray
Abstract Today’s automotive world has moved towards an age where safety of a vehicle is given the topmost priority. Many stringent crash norms and testing methodology has been defined in order to evaluate the safety of a vehicle prior to its launch in a particular market. If the vehicle fails to meet any of these criteria then it is debarred from that particular market. With such stringent norms and regulations in place it becomes quite important on the engineer’s part to define the structural requirements and protect the space to meet the same. If the concept level platform definition is done properly it becomes very easy to achieve the crash targets with less cost and weight impact.
2017-01-10
Technical Paper
2017-26-0019
Kantilal P. Patil, Viswanatha Saddala
Abstract The objective of this paper is to minimize occupant injuries in offset frontal crash with pulse characterization, by keeping vehicle front crush space & occupant survival space constant. Crash pulse characterization greatly simplifies the representation of crash pulse time histories. The parameters used to characterize the crash pulse are velocity change, time & value of dynamic crush, and zero cross-over time. The crash pulse slope, peaks, average values at discrete time intervals have significant role on occupant injuries. Vehicle crash pulse of different trends have different impact on occupant injury. The intension of crash pulse characterization study is to come out with one particular crash pulse which shows minimum occupant injuries. This study will have significant impact in terms of front loading on crash development of vehicle.
2016-11-07
Technical Paper
2016-22-0012
Tony R. Laituri, Scott Henry, Kevin Pline, Guosong Li, Michael Frankstein, Para Weerappuli
The National Highway Traffic Safety Administration (NHTSA) recently published a Request for Comments regarding a potential upgrade to the US New Car Assessment Program (US NCAP) - a star-rating program pertaining to vehicle crashworthiness. Therein, NHTSA (a) cited two metrics for assessing head risk: Head Injury Criterion (HIC15) and Brain Injury Criterion (BrIC), and (b) proposed to conduct risk assessment via its risk curves for those metrics, but did not prescribe a specific method for applying them. Recent studies, however, have indicated that the NHTSA risk curves for BrIC significantly overstate field-based head injury rates. Therefore, in the present three-part study, a new set of BrIC-based risk curves was derived, an overarching head risk equation involving risk curves for both BrIC and HIC15 was assessed, and some additional candidate-predictor-variable assessments were conducted. Part 1 pertained to the derivation.
2016-04-05
Technical Paper
2016-01-1538
Vaibhav V. Gokhale, Carl Marko, Tanjimul Alam, Prathamesh Chaudhari, Andres Tovar
Abstract This work introduces a new Advanced Layered Composite (ALC) design that redirects impact load through the action of a lattice of 3D printed micro-compliant mechanisms. The first layer directly comes in contact with the impacting body and its function is to prevent an intrusion of the impacting body and uniformly distribute the impact forces over a large area. This layer can be made from fiber woven composites imbibed in the polymer matrix or from metals. The third layer is to serve a purpose of establishing contact between the protective structure and body to be protected. It can be a cushioning material or a hard metal depending on the application. The second layer is a compliant buffer zone (CBZ) which is sandwiched between two other layers and it is responsible for the dampening of most of the impact energy.
2016-04-05
Technical Paper
2016-01-1541
Zuolong Wei, Hamid Reza Karimi, Kjell Gunnar Robbersmyr
Abstract The analysis of the vehicle crash performance is of great meaning in the vehicle design process. Due to the complexity of vehicle structures and uncertainty of crashes, the analysis of vehicle crashworthiness is generally depending on the researchers' experiences. In this paper, different deformation modes of energy absorption components are studied. More specifically, the bumper, crash box, the front longitudinal beam and the engine/firewall have different frequency characteristics in the deformation process. According to these characteristics, it is possible to identify the performance of each component in the crash process of assembled structures. To achieve this goal, the crash response of the passenger cabin is decomposed by the time-frequency transformation. Different frequency components exist mainly in a specified period of the crash process.
2016-04-05
Technical Paper
2016-01-1523
Libo Cao, Changhai Yao, Hequan Wu
Abstract The traditional deterministic optimal design is mostly based on meeting regulatory requirements specified in impact standards, without taking the randomness of the impact velocity and angle at the real world situation into consideration. This often leads to the optimization results that converge to the boundary constraints, thus cannot meet the reliability requirements of the product design. Structure members of B-pillar (e.g. inner panel, outer panel, and the reinforcing plate) play a major role in the side impact safety performance. This paper dealt with optimization of B-pillar by considering its dimensions and materials as the design variables, and the impact velocity and angle from real-world traffic accident conditions as the random variable inputs. Using a combination of design of experiment, response surface models, reliability theory and the reliability of design optimization method, a B-pillar was constructed based on the product quality engineering.
2016-04-05
Technical Paper
2016-01-1524
Feng Zhu, Binhui Jiang, Clifford C. Chou
Abstract This paper represents the development of a new design methodology based on data mining theory for decision making in vehicle crashworthy components (or parts) development. The new methodology allows exploring the big crash simulation dataset to discover the underlying complicated relationships between vehicle crash responses and design variables at multi-levels, and deriving design rules based on the whole vehicle safety requirements to make decisions towards the component and sub-component level design. The method to be developed will resolve the issue of existing design approaches for vehicle crashworthiness, i.e. limited information exploring capability from big datasets, which may hamper the decision making and lead to a nonoptimal design. A preliminary design case study is presented to demonstrate the performance of the new method. This method will have direct impacts on improving vehicle safety design and can readily be applied to other complex systems.
2016-04-05
Technical Paper
2016-01-1534
Rudolf Reichert, Pradeep Mohan, Dhafer Marzougui, Cing-Dao Kan, Daniel Brown
Abstract A detailed finite element model of a 2012 Toyota Camry was developed by reverse engineering. The model consists of 2.25M elements representing the geometry, thicknesses, material characteristics, and connections of relevant structural, suspension, and interior components of the mid-size sedan. This paper describes the level of detail of the simulation model, the validation process, and how it performs in various crash configurations, when compared to full scale test results. Under contract with the National Highway Traffic Safety Administration (NHTSA) and the Federal Highway Administration (FHWA), the Center for Collision Safety and Analysis (CCSA) team at the George Mason University has developed a fleet of vehicle models which has been made publicly available. The updated model presented is the latest finite element vehicle model with a high level of detail using state of the art modeling techniques.
2016-04-05
Technical Paper
2016-01-1535
Linli Tian, Yunkai Gao
Abstract Based on equivalent static loads method (ESL), a nonlinear dynamic topology optimization is carried out to optimize an automotive body in white (BIW) subjected to representative legislative crash loads, including frontal impact, side barrier impact, roof crush and rear impact. To meet the crashworthiness performances, two evaluation indexes are defined to convert the practical engineering problems into mathematic optimization problems. The strain energy is treated as the stiffness evaluation index of the BIW and the relative displacement is employed as the compliance index of the components and parts.
2016-04-05
Journal Article
2016-01-0519
Xiaoqing Xu, Bohan Liu, Yan Wang, Yibing Li
Abstract The mechanical behavior of polyvinyl butyral (PVB) film plays an important role in windshield crashworthiness and pedestrian protection and should be depth study. In this article, the uniaxial tension tests of PVB film at various strain rates (0.001 s-1, 0.01 s-1, 0.1 s-1, 1 s-1) and temperatures (-10°C, 0°C, 10°C, 23°C, 40°C, 55°C, 70°C) are conducted to investigate its mechanical behavior. Then, temperature and strain rate dependent viscoelastic characteristics of PVB are systematically studied. The results show that PVB is a kind of temperature and strain rate sensitive thermal viscoelastic material. Temperature increase and strain rate decrease have the same influence on mechanical properties of PVB. Besides, the mechanical characteristics of PVB change non-linearly with temperature and strain rate.
2016-04-05
Journal Article
2016-01-0497
Brian Falzon, Wei Tan
Abstract The development of the latest generation of wide-body carbon-fibre composite passenger aircraft has heralded a new era in the utilisation of these materials. The premise of superior specific strength and stiffness, corrosion and fatigue resistance, is tempered by high development costs, slow production rates and lengthy and expensive certification programmes. Substantial effort is currently being directed towards the development of new modelling and simulation tools, at all levels of the development cycle, to mitigate these shortcomings. One of the primary challenges is to reduce the extent of physical testing, in the certification process, by adopting a ‘certification by simulation’ approach. In essence, this aspirational objective requires the ability to reliably predict the evolution and progression of damage in composites. The aerospace industry has been at the forefront of developing advanced composites modelling tools.
2016-04-05
Journal Article
2016-01-0407
Da-Zhi Wang, Guang-Jun Cao, Chang Qi, Yong Sun, Shu Yang, Yu Du
Abstract The increasing demand for lightweight design of the whole vehicle has raised critical weight reduction targets for crash components such as front rails without deteriorating their crash performances. To this end the last few years have witnessed a huge growth in vehicle body structures featuring hybrid materials including steel and aluminum alloys. In this work, a type of tapered tailor-welded tube (TTWT) made of steel and aluminum alloy hybrid materials was proposed to maximize the specific energy absorption (SEA) and to minimize the peak crushing force (PCF) in an oblique crash scenario. The hybrid tube was found to be more robust than the single material tubes under oblique impacts using validated finite element (FE) models. Compared with the aluminum alloy tube and the steel tube, the hybrid tube can increase the SEA by 46.3% and 86.7%, respectively, under an impact angle of 30°.
2016-04-05
Technical Paper
2016-01-0398
Yuqing Zheng, Xichan Zhu, Xueqing Dong
Abstract To overcome some drawbacks of using AHSS (Advanced High Strength Steel) in vehicle weight reduction, like brittleness, spot weld HAZ (Heat Affected Zone) softening and high cost, a new ridgeline strengthening technology was introduced and applied to the thin-walled structure in this paper. The energy absorption mechanism of thin-walled box structure with selective strengthened ridgelines under axial compressing load was discussed in first section. After this, the formulas of mean crushing force and corresponding energy absorption for square tube were theoretically discussed. To demonstrate prediction capabilities of formulas, a set of FE simulations of square tubes were conducted. Simulation results show that energy absorption capacity of square tube under quasi-static axial crushing load is dramatically improved by selectively strengthening their ridgelines.
2016-04-05
Technical Paper
2016-01-0401
Yucheng Liu
Abstract In this paper, a new beam element is developed for the purpose of capturing thin-walled beam’s collapse mechanisms under dynamic load such as impact load and will be validated in the next phase. Such beam element can be used to create simplified finite element models for crashworthiness analysis and simulation and, therefore, will significantly reduce the modeling effort and computing time. The developed beam element will be implemented into LS-DYNA and validated through crashworthiness analysis and simulation. This paper introduces the approach of deriving the new element formulation.
2016-04-05
Technical Paper
2016-01-0402
Eric S. Elliott, Christopher Roche, Jashwanth Reddy
Since the inception of the IIHS Small Overlap Impact (SOI) test in 2012, automotive manufacturers have implemented many solutions in the vehicle body structure to achieve an IIHS “Good” rating. There are two main areas of the vehicle: forward of vehicle cockpit and immediately surrounding the vehicle cockpit, which typically work together for SOI to mitigate crash energy and prevent intrusion into the passenger zones. The structures forward of vehicle cockpit are designed to either 1) absorb vehicle energy from impact to the barrier, or 2) provide enough strength and rigidity to aid deflection of the vehicle away from the barrier. The structures which are immediately surrounding the vehicle cockpit (known as pillars and rocker/sills) are traditionally components designed to be highly rigid sheet metal panels to protect the occupant during crash events.
2016-04-05
Journal Article
2016-01-0404
Qianqian Du
Abstract Crashworthiness is one of the most important performances of vehicles, and the front rails are the main crash energy absorption parts during the frontal crashing process. In this paper, the front rail was simplified to a thin-walled beam with a cross section of single-hat which was made of steel and aluminum. And the two boards of it were connected by riveting without rivets. In order to optimize its crashworthiness, the thickness (t), radius (R) and the rivet spacing (d) were selected as three design variables, and its specific energy absorption was the objective while the average impact force was the constraint. Considering the error of manufacturing and measurements, the parameters σs and Et of the steel were selected as the uncertainty variables to improve the design reliability. The algorithm IP-GA and the approximate model-RBF (Radial Basis Function) were applied in this nonlinear uncertainty optimization.
2016-04-05
Technical Paper
2016-01-1396
Kai Liu, ZongYing Xu, Duane Detwiler, Andres Tovar
Abstract This work proposes a new method to design crashworthiness structures that made of functionally graded cellular (porous) material. The proposed method consists of three stages: The first stage is to generate a conceptual design using a topology optimization algorithm so that a variable density is distributed within the structure minimizing its compliance. The second stage is to cluster the variable density using a machine-learning algorithm to reduce the dimension of the design space. The third stage is to maximize structural crashworthiness indicators (e.g., internal energy absorption) and minimize mass using a metamodel-based multi-objective genetic algorithm. The final structure is synthesized by optimally selecting cellular material phases from a predefined material library. In this work, the Hashin-Shtrikman bounds are derived for the two-phase cellular material, and the structure performances are compared to the optimized structures derived by our proposed framework.
2016-02-01
Technical Paper
2016-28-0254
Nitin Tekavde, Srikari Srinivas, Vinod Banthia, Suman Mittemari
Abstract Design of vehicle structure to provide safe structural environment for occupants of vehicles involved in high speed (> 15 km/h) collisions has drawn considerable resources as safety of humans is at stake. Low speed impacts, since these do not cause severe injuries to the occupants, do not generate much concern. However, structural design for this situation has generated a lot of interest among insurance companies as the structural damage caused by these types of collisions is substantial, requiring significant payments by the insurance companies. In this work alternative designs for crash-box have been assessed for RCAR (Research Council of Automotive Repairs) requirement for frontal crash. Using structural details of an existing sedan, various designs of crash-box that can be fitted within the packaging space have been assessed for low speed impact.
2016-02-01
Technical Paper
2016-28-0050
Deepak Agrawal, Sharad Rawat, A. K. Upadhyay
Abstract Corrugated tubes are one among the different types of energy absorbers being used for the protection of passengers during impact /crash events of vehicles. Present work is primarily focused to analyze the effect of the variations of wavelength and amplitude of corrugation along the length of the tube on the crashworthiness of the tube. The circumferential corrugations in the tubes are graded by varying two parameters - wavelength and amplitude individually as well as simultaneously using different sinusoidal corrugation functions. The dynamic impact analysis has been carried out using LS-DYNA FEM code using shell elements for meshing and Magnesium alloy AZ31 as material. Energy absorbed, initial peak force, mean force and stroke length are the parameters used in this comparative study. It is observed that the initial reaction forces as well as the ratio of the mean reaction force to peak load changes with the grading of corrugation.
2015-09-15
Technical Paper
2015-01-2461
Enrico Troiani, Maria Pia Falaschetti, Sara Taddia, Alessandro Ceruti
Abstract The high number of hull losses is a main concern in the UAV field, mostly due to the high cost of on-board equipment. A crashworthiness design can be helpful to control the extent and position of crash impact damage, minimizing equipment losses. However, the wide use of composite materials has recently put the accent on the lack of data about the behavior of these structures under operative loads, such as the crash conditions. This paper presents the outcome of a set of tests carried out to achieve a controlled crush of UAV structures, and to maximize the Specific Energy Absorption. In this work, a small-scale experimental test able to characterize the energy absorption of a Carbon-fiber-reinforced polymer under compression was developed introducing self-supporting sinusoidal shape specimens, which avoid the need for complex anti-buckling devices.
2015-04-14
Technical Paper
2015-01-1352
Ashish Kumar Sahu, Abhijit Londhe, Suhas Kangde, Vishal Shitole
Abstract Body in White (BIW) is one of the major mass contributors in a full vehicle. Bending stiffness, torsional stiffness, durability, crashworthiness and modal characteristics are the basic performance parameters for which BIW is designed. Usually, to meet these parameters, a great deal of weight is added to BIW. Sensitivity analysis helps to identify the critical panels contributing to the performance while BIW optimization helps to reduce the overall mass of the BIW, without compromising on the basic performances. This paper highlights the optimization study carried out on the BIW of a Sports Utility Vehicle (SUV) for mass reduction. This optimization was carried out considering all the basic performance parameters. In the initial phase of BIW development, optimization helps to ensure minimum BIW weight rather than carrying out mass reduction post vehicle launch.
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