Vehicle Body Structure Research Articles

Study on Radiated Noise of a Panel under Fluctuating Surface Pressure Due to an Idealized Side Mirror

As traditional automobiles develop towards new energy vehicles, the noise, vibration and harshness (NVH) performance of automobiles is facing new challenges. Without the cover of the traditional engine noise and inlet and exhaust noise, the high-speed wind noise becomes more prominent. Thus, research on the calculation method of vehicle interior noise in high-speed driving condition is needed. However, vehicle body structure is complex, and the external excitation components are complicated. In order to analyze the method of predicting the vehicle interior noise at high speed, an idealized side mirror model is taken as the research object in this paper and the radiated noise of a panel under the fluctuating surface pressure (FSP) due to the idealized side mirror is studied. The FSP of the panel is first studied by the numerical simulations of incompressible and compressible flow field. For the incompressible flow field, the Corcos turbulent boundary layer (TBL) model is established to simulate the convective component and the boundary element method (BEM) is used to extract the acoustic component. Subsequently, the Corcos model coupling BEM method, the random modal force coupling BEM method and the deterministic modal force coupling BEM method are used separately to calculate the noise of the panel under the FSP. For the compressible flow field, the convective and acoustic component in the fluctuating pressure are separated by the wavenumber-frequency spectrum (WFS) method. The radiated noise of the panel under the FSP is calculated again by using the WFS, the method of random modal force and the method of deterministic modal force, respectively. Then, the computational time of the six methods of incompressible and compressible calculation is compared. Finally, a fast and accurate method of calculating the panel radiated noise under FSP is obtained by comparing the computational accuracy with the experimental results and combining the computational time: the method of incompressible random modal force. This method can be used to quickly and accurately analyze the vehicle interior noise at high speed, and to optimize the exterior protrusions and the vehicle sound package for improving the vehicle NVH performance at high speed.

The Welding Processes of Rolled Homogeneous Armour Steel

Rolled Homogeneous Armour (RHA) steel is known as protective steel and it is utilized in a military vehicle, For example tanks, howitzers, heavily clad battle vehicles just as developments in armament. Weld quality straight forwardly decides the entire mechanical properties of the protective steel in vehicle body structures. Hybrid Optical Maser Arc welding (HOMAW) has a decent mechanical property and focal point of this exploration is considered to recover more energy than laser and Metal Active Gas Welding (MAGW) process. Manual Metal Arc Welding (MMAW) with low hydrogen ferritic filler (LHF) which performs better weldability on Armour steels with comparing MMAW with Austenitic stainless steel (ASS), and Flux cored arc welding (FCAW) with ASS/LHF. MMAW procedure is considered to reduce the expense through LHF consumable in workplace. The examination of MAGW method, a welding fringe of 54o V-narrow cut geometry has better mechanical property for tensile strength and also the welding narrow cut point of 48o X-trench cut geometry has better solution for compression strength of butt-joint Armour steel. This survey was embraced to grant a top-level view of the various categories of welding process and mechanical properties in welding of RHA steels.

Improving weldability of Al-Si coated press hardened steel using stepped current pulse schedule

Al-Si coated press hardened steel (PHS) were introduced into vehicle body structures for a balance of lightweighting and crashworthiness. However, the weldability of PHS is relatively poor, due to its high carbon equivalent and high strength and is characterized by severe heat affected zone, HAZ softening, and interfacial fracture. The interfacial fracture mode is defined in part by the presence of retained Al-Si coating as a sharp notch at the faying interface following the welding process, which limits the mechanical performance of the joint. To improve the weldability of PHS, a stepped current pulse schedule was proposed for the resistance spot welding (RSW) of 1.5 mm Al-Si coated PHS as a means to effectively promote nugget growth, inhibit expulsion and eliminate the residual Al-Si layer. In this manner the mechanical performance of joints were significantly improved and the desirable button pullout fracture mode was realized.

Study of structural optimization design on a certain vehicle body-in-white based on static performance and modal analysis

Abstract The intensity analysis was proposed for a certain all-aluminum vehicle body-in-white, and an optimistic method of the vehicle body was carried out based on lightweight target. The finite element model of vehicle body-in-white was established, and the flexural rigidity and torsional rigidity of the vehicle body are calculated according to the actual operating conditions of the vehicle. The flexural rigidity and torsional rigidity of the vehicle body are calculated, and the main opening deformation of the vehicle body under these two working conditions was studied. Finally, based on the thickness of the body panel, the structural sensitivity analysis of the vehicle body was carried out. According to the sensitivity analysis data, the optimization variable is determined with lightweight as the target, and the vehicle body structure is optimized. The results showed that the static and dynamic performance indexes of the white body were higher than the standards of similar motorcycle type at home and abroad, the bending stiffness of the structurally improved basic model after sensitivity optimization was reduced by 2.1% compared with before optimization, but still much higher than the target reference value (122,000 N/mm). And the quality of the vehicle body was reduced, which met the lightweight requirements of optimized design after the optimization of the thickness of the improved basic model.

A multi-view optical technique to extract the operating deflection shapes of a full vehicle using digital image correlation

Abstract The automotive and aerospace industries are increasingly using light-weight material to improve vehicle performance while reducing fuel consumption. However, using light-weight material can increase the air-borne and structure-borne noise. Thus, special attention needs to be paid in designing the vehicle body structure and evaluating its dynamics. In order to accomplish this, modal analysis is conventionally used. In this technique, the structure is excited using an impulse hammer or a mechanical shaker, and the response is measured using accelerometers. However, using contact-based transducers can mass-load the structure and can only provide data at a few discrete points. In the last decade, stereo-photogrammetry and three-dimensional digital-image correlation have received special attention in collecting operating data for structural analysis. These non-contact optical techniques provide a wealth of distributed data over the entire structure. However, the stereo-camera system is limited by the field of views of the cameras and can only measure the response on the parts of a structure for which cameras have lines of sight. Therefore, a single pair of DIC cameras may not be able to provide deformation data for an entire structure. A multi-view 3D DIC approach, however, can be used to predict the vibrational characteristics of a full vehicle. A pair of DIC cameras is passed over the entire vehicle to capture the deformation data of each field of view. The measured data includes the geometry and displacement data, which is mapped into a global coordinate system using 3D transformation matrices. The obtained data in the time domain for each field of view is transformed to the frequency domain using a Fast Fourier Transformation (FFT) to extract the operational deflection shapes and resonant frequencies for each field of view. The obtained deflection shapes are scaled and stitched in the frequency domain to extract the operating deflection shapes of the entire vehicle.

Dissimilar metal joining of aluminium to zinc-coated steel by ultrasonic plus resistance spot welding – microstructure and mechanical properties

Vehicle body structures are increasingly utilising multi-materials designs with advanced high strength steels (AHSS) and aluminium alloys. A robust process for joining aluminium alloys to AHSS based on resistance spot welding (RSW) is essential to widespread application of such bi-metallic structures in fuel-efficient vehicles. In this study, ultrasonic plus RSW was applied to join AA6022 to Zn-coated dual-phase steel DP980. During solid-state ultrasonic spot welding, an interface structure comprising multilayer, Al–Zn and Zn–Fe intermetallics formed due to alloying of aluminium with steel coating. Such structure was subsequently melted into the aluminium nugget, and new Al–Fe intermetallics formed during RSW. Ultrasonic plus resistance spot-welded joints had superior fracture energy than direct resistance spot-welded joints.

Necking-induced fracture prediction using an artificial neural network trained on virtual test data

The imperfection-based necking model by Marciniak and Kuczyński (MK) is frequently used for predicting the onset of localized necking under proportional and non-proportional loading, which can be considered a lower limit for the occurrence of fracture in a vehicle body structure subjected to crash loading. A large number of virtual imperfection lines at different orientation angles have to be analysed simultaneously in order to find the critical imperfection causing necking under arbitrary loading. This, and the continuous computation of a “distance to necking” quantity, representing a crucial output quantity for the simulation engineer, makes the model computationally expensive and limits industrial use in full-scale vehicle crash simulations.In this work, an extended MK model is used for creating a virtual test data base under proportional and non-proportional loading for training of a computationally more efficient simple feed-forward neural network (NN). Both models are implemented in a User Material routine of an explicit crash code, where the predictions of the NN are in good agreement with the predictions of the MK reference model, however at a significantly reduced computational cost. Besides a pure numerical validation study, an experimental validation study has been performed, imposing biaxial tension loading followed by plane strain tension loading until necking using a special punch test apparatus. Whereas MK and NN are in good agreement with the experimental observations, the agreement of classical necking models, applied in conjunction with a linear damage accumulation (forming severity) concept was less accurate.

A multi-objective optimization approach for simultaneously lightweighting and maximizing functional performance of vehicle body structure

This study presents a hybrid approach to integrate the comprehensive sensitivity analysis method, support vector machine technology, modified non-dominated sorting genetic algorithm-II method and the technique for order preference by similarity to ideal solution, which have been applied to multi-objective lightweight optimization of the B-pillar structure of an automobile. First, numerical models of the static–dynamic stiffness and the crashworthiness performance of automobile are established and validated by experimental testing. Then, the comprehensive sensitivity analysis method is used to define the final optimization variables. Experimental design and support vector machine based surrogate model techniques are introduced to establish the approximate model; subsequently, the modified non-dominated sorting genetic algorithm-II algorithm is applied to the multi-objective lightweight optimization design of the B-pillar structure, and the non-dominated solution set is determined. The principal component analysis method is applied to determine the weight of each objective. Finally, the technique for order preference by similarity to ideal solution method is used to rank Pareto front from best to worst to obtain the optimal solution; furthermore, a comparison between the original model and optimized design denotes that the mass of the B-pillar being reduced by 22.55% under the other impacting indicators is well guaranteed. Therefore, the proposed hybrid approach provided promising prospects in the lightweight and crashworthiness optimization application of the B-pillar.

The Effect of Variation of Nano SiC Reinforcement Particle Addition to Mechanical Properties of Mg/Nano SiC Composite by Stir Casting Method

Composites are advanced material which is being developed that contains of two materials or more in order to improve the mechanical properties. Magnesium composite is a suitable material beside aluminium and its alloy to be applicated as vehicle body structure due to its lightweight and its low density. Thus, the vehicle body structure with lightweight and good mechanical properties can be achieved. In this research, magnesium composite is fabricated by mixing magnesium as composite matrix and nano SiC as reinforcement particle with the variation of the volume fraction 0.05 %vf, 0.10 %vf, 0.15 %vf, 0.20 %vf, and 0.25 %vf with stir casting as fabrication methods. To characterize the composite product, several testing were done, which were chemical composition characterization, metallographic observation, SEM-EDS characterization, XRD characterization, hardness testing, wear testing, and impact testing. The result of this research shows that with nano SiC addition as reinforcement particle will increase mechanical properties of magnesium composite. The best mechanical properties of magnesium composite is shown by the addition of 0.15 %vf nano SiC. The result shows the brinnel hardness number of this composition is 39 HB and 0.0052 mm3/m wear rate. Mechanical properties of magnesium composite are increased due to several strengthening mechanism such as grain size reduction and Orowan strengthening mechanism.

Nondestructive evaluation of resistance spot-welded Al-steel joints

Abstract

Approach to the systematic categorization and qualitative evaluation of multi-material designs for use in vehicle body structures

Multi-material designs are characterized by the use of different materials within a technical system and may require different understandings depending on the level from which they are viewed. The aim of this paper is to present the understanding of multi-material design in the context of vehicle body development and to categorize the different vehicle body design principles particularly in multi-material design. On the basis of the developed categories, a qualitative evaluation of the design methods will be carried out with regard to development, production and manufacturing effort. The purpose is to provide an approach for the qualitative evaluation of multi-material designs in the early concept development phase.

Advances in Automotive Conversion Coatings during Pretreatment of the Body Structure: A Review

Automotive conversion coatings consist of layers of materials that are chemically applied to the body structures of vehicles before painting to improve corrosion protection and paint adhesion. These coatings are a consequence of surface-based chemical reactions and are sandwiched between paint layers and the base metal; the chemical reactions involved distinctly classify conversion coatings from other coating technologies. Although the tri-cationic conversion coating bath chemistry that was developed around the end of the 20th century remains persistent, environmental, health, and cost issues favor a new generation of greener methods and materials such as zirconium. Environmental forces driving lightweight material selection during automobile body design are possibly more influential for transitioning to zirconium than the concerns regarding the body coating process. The chemistry involved in some conversion coatings processing has been known for over 100 years. However, recent advances in chemical processing, changes in the components used for vehicle body structures, environmental considerations and costs have prompted the automobile industry to embrace new conversion coatings technologies. These are discussed herein along with a historical perspective that has led to the use of current conversion coatings technologies. In addition, future directions for automobile body conversion coatings are discussed that may affect conversion coatings in the age of multi-material body structures.

Uncertainty Optimization Design of a Vehicle Body Structure Considering Random Deviations

In vehicle body manufacturing, there are small differences between the actual value and design value of, for example, plate thickness and material characteristics. This is caused by the processing technology, environment and other uncertain factors. Therefore, the performance of the vehicle body processed according to the deterministic optimization solution fluctuates. The fluctuations may make structural performance fail to meet the design requirements. Thus, in this study, an optimization design is executed with 6 $$ \sigma $$ robustness criteria and a Monte Carlo simulation single-loop optimization strategy based on the radial basis function neural network approximate model considering deviations in plate thickness, elastic modulus, and welding spot diameter, which is called the uncertainty optimization design method. As an example, considering the bending stiffness, torsion stiffness, and first-order frequency as constraints, the method is applied to the lightweight design of a car body structure, and the reliability of deterministic optimization design and uncertainty optimization design is compared. The results demonstrate that the uncertainty optimization design solution is effective and feasible without lowering the static stiffness and modal performance, and the weight is reduced.

A new methodology to determine the design sensitivity of critical automotive body joints for basic design cycle

As a result of more stringent requirements for improved fuel economy and emissions, there has been an increasing research activity to make vehicles lighter weight under some predetermined structural performance targets such as the stiffness of the vehicle body. The vehicle body structure is one of the most significant contributors to the weight of an automotive. Therefore, understanding the automotive joint properties on vehicle body performance is of significant importance as they are closely linked to structural integrity and weight of the vehicle body. In this paper, we develop a new methodology to quantify the sensitivity of critical joints of an automotive on the key performance indices. Torsional stiffness is chosen as static key performance index, while vehicle body modes are selected as dynamic key performance indices. Lower and upper sections of the A-pillar, B-pillar, C-pillar, and D-pillar of an automotive body are replaced by bushing elements having appropriate stiffness properties in the simplified model. Stiffness of bushing elements is tuned by minimizing the error between the original and simplified models on the aforementioned key performance indices. Once a satisfactory correlation is achieved between the simple model and the original model, bushing stiffness for each section is varied to determine the sensitivity of each joint. The proposed approach is demonstrated on a finite element model of 2010 Toyota Yaris. Finally, a design study is presented to improve the body key performance indices using the sensitivity results. The simulation results show that the methodology has a potential for the basic design cycle, where the targets for section properties need to be defined and at later design cycles, where the joints can be realized in design using the sensitivity of joints resulting in more efficient body structure considering the trade-offs between structural integrity and weight.

Full-field deformation and strain measurement of vehicle body under high-speed impact

A crash test is a common method to evaluate passive vehicle safety, but its full-field deformation and strain is difficult to measure due to instantaneous large deformation during the intense impact process. By means of high-speed cameras, a full-field deformation and strain measurement under high-speed impact is presented based on digital image correlation and binocular stereo vision. To deal with weak correlation in image matching caused by optical noise and large deformation, a controllable Gaussian filter and adaptive light intensity coefficients are used to suppress image intensity interference introduced by optical noise. In addition, based on deformation continuity of the neighboring states, images before and after large deformation are matched by the minimization of reference datum and transfer of deformation coefficients. Finally, full-field deformation and strain data are obtained from an impact test on an engine cover made from DC04 steel. Results show that the deformation measurement accuracy of the method can achieve 0.03 mm within a 500 × 400 mm2 field of view. This study solves the problems of limited measurement points and low efficiency both in the contact measurement method by displacement sensors and traditional optical measurement by the detection of artificial target points, and provides a scientific basis for quantitative analysis of vehicle impact safety, vehicle body structure and material improvement, and finite element simulation of impact theory.

Development of a Lightweight Third-Generation Advanced High-Strength Steel (3GAHSS) Vehicle Body Structure

Development of a Lightweight Third-Generation Advanced High-Strength Steel (3GAHSS) Vehicle Body Structure

Aerodynamic Analysis of Flat Solar Panel Mounted Mini Bus Model With Different Yaw Angles

The aerodynamic analysis of automotive vehicle play a vital role in deciding its overall performance and stability. The change in exterior vehicle body structure, affect drag and lift coefficient significantly. Also the variation of yaw angle affect vehicle performance significantly in terms of fuel consumption and stability. In the view of environmental concern and limitation of conventional fuel forced researchers to think about environment friendly alternatives. Using rooftop solar panel is an easy and convenient way to address this issue up to a certain extent. The objective of present work is to perform computational aerodynamic analysis of flat solar panel mounted mini bus model with 150 mm mounting height from roof at speed of 80 kmph. Also to investigate the effect of variation in yaw angles from 0 to 180 degree on vehicle performance. First numerical investigation is carried out to assess the impact of flat solar panel on the coefficient of drag of vehicle. To validate numerical result, the wind tunnel test is performed on scaled prototype model. The result shows the close correlation between experimental and numerical analysis. Further investigation carried out by considering variation of yaw angle. The result shows significant changes in drag and lift coefficient with respect to yaw angle.

Subjective absolute discomfort threshold due to idle vibration in passenger vehicles according to sitting posture

Idle vibration, occurring when a vehicle comes to a stop while the engine is on, is known to be a main cause of discomfort for passengers, and the customer effect has been recently growing. The frequency of idle vibration is determined by the engine type. To lower the vibration, various technologies have been applied to optimize the engine mount and vehicle body structure. In addition to the technological developments, research on human response with a consideration of idle vibration is needed to effectively reduce the level of discomfort experienced by passengers. Seats aimed at enhancing static comfort influence the sitting posture of passengers; sitting posture is a factor affecting human body characteristics that response to idle vibration. This study examined the absolute discomfort threshold of idle vibration according to the sitting postures of 13 taxi drivers. The four sitting postures of subjects on a rigid-body seat without a backrest were variables in the determination of absolute discomfort threshold of idle vibration. The absolute discomfort threshold curves obtained in this experiment were less sensitive to frequency changes than the frequency weighting function of ISO 2631-1.

A new design of friction test rig and determination of friction coefficient when warm forming an aluminium alloy

Abstract To facilitate reduced fuel consumption and increase environmental friendliness, in recent years, demands for lightweight vehicles have been increasing, and interest in hot or warm forming of sheet aluminium alloys for use in vehicle body structures, has grown. For better understanding and optimisation of the forming processes, knowledge of friction coefficient between tooling and work-piece, at elevated temperature, is critical. However, because of difficulties with measurement at elevated temperature, most studies on friction are limited to room temperature. In this study, a friction rig was designed for isothermal tests at elevated temperature. The test rig enables pure sliding between pins (made of a tool steel) and a metal sheet. The friction behaviour of Forge Ease 278, a water based solid lubricant pre-applied to aluminium alloy AA5754, was investigated, under isothermal warm forming conditions, using the test rig. The effects of testing temperature, sliding speed and applied pressure on the friction coefficient were studied. It was found that Forge Ease produced a low friction coefficient of around 0.05, above room temperature and below 250 °C. The lubricant performance degrades at 350 °C and the friction coefficient increases markedly. Both sliding speed (up to 150 mm s-1) and applied pressure (up to 12.8 MPa) had no significant effect on friction coefficient of Forge Ease.

Development of Vehicle Model Test for Road Loading Analysis of Sedan Model

Simple Structural Surfaces (SSS) method is offered as a means of organizing the process for rationalizing the basic vehicle body structure load paths. The application of this simplified approach is highly beneficial in the design development of modern passenger car structure especially during the conceptual stage. In Malaysia, however, there is no real physical model of SSS available to gain considerable insight and understanding into the function of each major subassembly in the whole vehicle structures. Based on this motivation, a physical model of SSS for sedan model with the corresponding model vehicle tests of bending and torsion is proposed in this work. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results show that the proposed vehicle model test is capable to show that satisfactory load paths can give a sufficient structural stiffness within the vehicle structure. It is clearly observed that the global bending stiffness reduce significantly when more panels are removed from a complete SSS model. It is identified that parcel shelf is an important subassembly to sustain bending load. The results also match with the theoretical hypothesis, as the stiffness of the structure in an open section condition is shown weak when subjected to torsion load compared to bending load. The proposed approach can potentially be integrated with FEM to speed up the design process of automotive vehicle.