Showing papers in "International Journal of Vehicle Structures & Systems in 2010"

Thermal Analysis of a Disc Brake Model Considering a Real Brake Pad Surface and Wear

Abstract: Vehicle braking system is considered as one of the most fundamental safety-critical systems in modern vehicles as its main purpose is to stop or decelerate the vehicle. The frictional heat generated during braking application can cause numerous negative effects on the brake assembly such as brake fade, premature wear, thermal cracks and disc thickness variation (DTV). In the past, surface roughness and wear at the pad interface have rarely been considered in studies of thermal analysis of a disc brake assembly using finite element method. This paper attempts to consider these two aspects to predict temperature distributions in a reduced disc brake model. First, two different brake pad interface models, i.e., smooth and rough surfaces are modelled and simulated. Temperature distributions in these two models are then compared. Next, the thermal analysis is performed with the effect of wear at three different braking applications.

Behaviour of an Impact Attenuator for Formula SAE Car under Dynamic Loading

Abstract: A Formula SAE car must have structural devices that able to absorb most of the kinetic energy by means of progressive crushing therefore minimizing the forces and decelerations transferred to the occupant during frontal collisions. This paper presents the prediction of dynamic behaviour of an impact attenuator for a Formula SAE car under frontal impact conditions by using numerical and experimental approaches. The impact attenuator construction is a combination of sandwich panels and aluminium inner sheets. Firstly, the analysis of sandwich structures is carried out to better understand their behaviour and model them properly in the numerical simulation using LS-DYNA. In order to obtain the best configuration for the impact attenuator in terms of maximum absorbed energy, minimum deceleration and weight saving, its length and the number of inner sheets are optimised. Finally, a crash-test is performed on the impact attenuator to compare the experimental results with the numerical ones. The results obtained show that the impact attenuator is able to absorb the total impact energy with progressive and plastic deformation to contain the average deceleration as below 20 g.

Load Transfer in Truck Cab Structures under Initial Phase of Frontal Collision

Abstract: A new parameter U** that represents load paths in structures is applied to a truck cab under collision. Since the main part of a compartment should be maintained in a linear elastic condition, a linear U** analysis can be applied. U** for the deformed body is statically calculated from the extracted deformation results of a crash simulation. A substitution-modulus method is applied to reproduce the material and geometrical nonlinearities. An index "m2-4msU**" is proposed as a standard condition for the truck cab. The predominant load paths along the floor member and the shear effect of the floor panel are demonstrated.

Bus Structure Behaviour under Driving Manoeuvring and Evaluation of the Effect of an Active Roll System

Abstract: One of the main causes of traffic accidents in which heavy vehicles are involved is lateral stability loss. It is well known that heavy vehicles have relatively high centres of gravity and narrow track widths and can lose roll stability at moderate levels of lateral acceleration. The influence of several parameters (i.e. height of the centre of gravity, weight distribution between axles, chassis torsional stiffness, etc.) on bus roll stability during a lane change manoeuvre, as well as the bus structure stress level has been analyzed by means of a six degrees of freedom beam finite element model. In addition, due to the use of active systems to prevent excessive roll motions in heavy vehicles, the effect of an active system based on anti-roll bars in a bus structure under a lane change manoeuvre is carried out by means of a bus dynamic finite element model. Results show that the fuzzy logic controller implemented in the anti-roll bar system significantly reduces both the vertical displacements at the corners of the bus structure and the stress level.

A Combined Subdivision and Advancing Loop-Front Surface Mesher (Triangular) for Automotive Structures

Abstract: In this paper, a new, hybrid, 2D meshing algorithm, CSALF-T, is proposed for boundary-structured triangular meshes used for the analyses of automotive structures. The algorithm is based on the understanding of boundary loops. All mesh area boundary loops are initially meshed recursively with a new, loop-based advancing ?loop-front? technique that produces high-quality boundary-structured meshes. The remaining interior domain is filled out by a recursive subdivision technique. Both approaches are driven by a background sizing function. The mesh is finally smoothed by a variational smoother. Loop-fronts are classified and rule sets are defined for each, to aid optimum point placement. Stencils used for loop-closure are presented. Results show examples of meshes used for the crash analyses of automotive body panels with large mesh size transition generated on complex 2D domains. Comparisons are made to pronounce the merits of the hybrid algorithm with respect to both traditional advancing front and subdivision based meshing techniques.

Weight Reduction in an Indian Railway CASNUB Bogie Bolster Considering Fatigue Strength

Abstract: Weight and strength are critical measures in the design of a railway bogie. The present work deals with the design of CASNUB bogie bolster of freight rolling stock in Indian Railways. The bogie is modelled using NX3, UGS software. Finite element analysis of the model is performed using MSC Patran/Nastran. Natural frequencies obtained from free vibration analysis are compared with those obtained experimentally using a Rap-Test. Effort has been made to reduce the weight of bogie bolster considering fatigue strength. Bogie loading includes vertical forces, longitudinal emergency brake force and vertical as well as lateral track excitations. Transient analysis of bogie is performed to identify the critical areas and surfaces relevant for weight reduction. Thicknesses of the bolster top, bottom and side surfaces are subsequently identified as design variables. These parameters are optimized using artificial neural network and genetic algorithm techniques. Such optimization has resulted in approximately 7.6% reduction in weight of the bolster. The optimal bogie bolster has been verified for its fatigue strength using Goodman diagram.

Effects of Hand-Arm and Whole-Body Vibrations on Heart of Motorcycle Rider

Abstract: Motorcycle riders are subjected to hand arm and whole body vibrations. Both these vibrations affect the health of the rider. This paper attempts to analyze the effects of these vibrations on heart using finite element simulation and experiments. Firstly, the hand arm and whole body vibration forces are measured by conducting experiments on different motorcycles and for various road conditions. These measured forces are applied to the finite element model of a motorcycle rider to predict the distribution of Von mises stress around heart. Secondly, the average relative heart rate, the hand arm and whole body vibration accelerations are measured with by conducting experiments on different riders with typical body mass index and for various road conditions. The variations in the vibrations magnitude and the Von mises stress around heart correlate well. The Von mises stress and heart rate are more sensitive to the hand arm vibrations than the whole body vibrations. This effect on the heart may cause a cardiac problem in the long run.

Synthesis of Equivalent Load Conditions for Military Vehicles

Abstract: The aim of this paper was the identification of the load conditions to consider during the design and assessment of military vehicles. This meant identifying test tracks and their corresponding ground speeds and track lengths, and to define their combinations that are useful to simulate the load spectrum representing the system/component life in an accelerated way. The result of this activity was the development of a formulation for the synthesis of a single power spectrum density function (PSD) representing multiple load conditions expressed by a set of PSD functions. This function is equivalent in terms of damage to the given PSD functions set. Another important result was the definition of a virtual test ring, equivalent to those defined in standards for equipment and supplies, but useful for the virtual check of the military vehicle integrity. This new formulation and the proposed test ring intend to supply tools that would be very useful in the early phases of vehicle design and assessment. In order to verify these results, numerical and experimental analyses of a generic military vehicle were undertaken. Results demonstrated the validity of the load synthesis formulation and the load combination that are useful for the assessment of military vehicle durability.

Modeling Abstractions of Vehicle Suspension Systems Supporting the Rigid Body Analysis

Abstract: It is possible to use architecture concept models for CAE analyses supporting the design and optimization of a vehicle's general layout prior to the time consuming and expensive preparation of detailed models. Suspension system, including kinematic linkages, compliance and damping elements, wheels, tires, and brakes, plays a key role in determining whether the basic layout of a vehicle is suitable for given application. This paper presents an appropriate set of architecture level abstractions for suspension systems that can be incorporated into full vehicle concept models. These modeling abstractions provide abstract representations of a wide variety of suspension system configurations that illustrate both geometric and functional properties without resorting to high-fidelity solid model renderings of parts using details that simply do not exist this early in the design process. The architecture concept suspension model presented in this study can be used for vehicles rigid body analysis.

Influence of Air Conditioning Characteristics on Vehicle Interior Noise

Abstract: Reduction of Heating, Ventilation and Air Conditioning (HVAC) systems and other components such as engine and exhaust system has resulted the study on the vehicle noise as an increasingly important aspect for the automotive industry in meeting the passenger comfort requirements. In this paper, the influence of vehicle air conditioning characteristics such as the fan speed, engine speed and air conditioning positions (i.e., ON or OFF) on the vehicle interior Sound Pressure Level (SPL) is presented. The generation of noise and its transmission mechanisms are studied. The major contributors to the HVAC system airborne noise are the aerodynamic, mechanical and hydraulic noises from the compressor and handling units. Since the HVAC's fan is driven directly by the vehicle battery that is separated from the HVAC, the noise generation due to the fan speeds or positions can be directly obtained by turning the compressor to OFF and the fan to ON positions. Meanwhile, the mechanical and hydraulic noises can be obtained by extracting the airborne noise by turning the compressor to OFF and the fan to ON positions from those obtained by turning both the compressor and fan to ON position. The experimental results indicate that the principal source of vehicle noise is related to the aerodynamic noise and the noise level has shown considerable increase when both the fan and compressor units are turned to ON positions. For a specific fan speed, an increase in the noise due to the mechanical and hydraulic sources is observed for an increase in the engine speed.

Effects of lining thickness on squeal in drum brake assembly: experimental investigations

Abstract: This paper presents the effects of brake lining thickness due to wear on drum brake squeal. Brake lining will be worn out and subsequently its thickness will be reduced after a few number of braking applications. Hence dynamic properties of the lining, such as its natural frequency, might be changed. In this work, two different sets of brake lining, i.e., new and worn lining are used to investigate its effect on squeal generation. First, modal testing is performed to determine natural frequencies of those brake linings at free-free boundary condition. Later, squeal tests are carried out using brake dynamometer and squeal frequency is measured up to 10 kHz. Several squeal results are plotted over brake operating conditions to observe the influence of different lining thickness. In addition to these, squeal mechanisms, i.e., modal coupling due to closeness of the natural frequency between drum brake components and negative damping due to negative friction-velocity slope that contribute to the squeal generation are also investigated and discussed.

Neural Networks Based Fatigue Life Prediction of Multi Walled Carbon Nano Tubes Doped E-Glass/Epoxy Laminates

Abstract: In recent years, carbon nano tubes and their applications have been the prime focus of research in the field of nanotechnology. In this paper, the fatigue life prediction of multi walled carbon nano tubes (MWCNT) doped E-Glass/Epoxy laminates is presented. Two different doping ratios of MWCNT (0.2% and 0.4%) are considered to demonstrate the improvement in fatigue life of the composite laminate. The fatigue tests are undertaken on an Instron 8802 universal testing machine using a uni-directional (UD) Glass/Epoxy laminate specimen fabricated as per the ASTM standard - ASTM D 3039. An artificial neural network (ANN) based approach with a back propagation algorithm is used to predict the fatigue life cycles. The proposed neural network is trained using the fatigue test data set. The predicted fatigue results from the ANN are in good agreement with the experimental results. The proposed approach can be utilised to predict the fatigue life of Glass/Epoxy laminates for varied MWCNT doping ratios.

Heavy Truck Occupant Safety Analysis Using Finite Element Simulation

Abstract: This paper discusses how numerical simulation of automotive crashes play an important role in reducing the cost and time taken for predicting the results of a collision. The subject of interior crash protection has received much more attention for automobiles than commercial vehicles like heavy trucks. This paper presents a finite element simulation of a heavy truck cab for safety analysis of its occupant during frontal collisions. The dashboard of the cab is modelled along with a steering column, floor and a roof top. Two type of acceleration pulses are used to calculate the Head Injury Criteria, Neck Injury and chest injury levels of the occupant. Three different scenarios of occupant namely without seatbelt, with seatbelt, and with both airbag and seatbelt are detailed. The results of simulation have demonstrated that the use of safety restraints has reduced the occupants injury to considerable levels.

Vibration Isolation of a GA Optimized Biomechanical Model of a Railway Passenger Using Magneto Rheological Damper Seat Suspension

Abstract: Driver tiredness during long term travel might result in many unwilling accidents. Hence, isolating the vibration transmitted to the driver plays a major role in keeping the driver restful and consequently having a safe trip. In this study, the transmitted vibration of a wagon suspension to a passenger model is isolated by a semi active control strategy using a magneto rheological (MR) damper. First, a revised linear lumped parameter biomechanical model of seated human body exposed to vertical vibrations is optimized. To this end, the parameters of the human body model, including mass, damper and stiffness coefficients are simultaneously optimized using genetic algorithm by employing a multi-objective function. Next, the optimized human body model is integrated on a nonlinear seat suspension model. This integrated model is excited by a sinusoidal frequency range as applicable to railway vehicles. The responses in time and frequency domains are derived. Finally, by using a MR damper instead of conventional dampers in the seat suspension, it is shown that the transmitted acceleration from the rail to the driver is reduced. Finally, a comparison of the performances of passive conventional dampers, semi-active MR dampers and active actuator assisted dampers is presented in detail.

Parametric Study on Transverse Vibration of Thin Rectangular Plate with Bonded Elastic Patch

Abstract: In this work, transverse vibration of a thin rectangular plate with bonded high density and high modulus patch has been undertaken with simply supported boundary conditions at its edges. Plate material properties, patch thickness and patch area influence the transverse vibration of the host plate. Therefore, these effects must be accounted to correctly determine the natural frequencies of the plate in transverse vibration. The equation of motion for transverse vibration of the plate has been derived by taking into account of the patch material elasticity in the moment and force equations. The displacement function of the transverse vibration has been represented by a double Fourier series to solve the equation of motion for a composite plate with bonded elastic patch. Influence of dimensionless material and geometry parameters on the natural frequencies of the composite plate have been investigated. For material parameters, the flexural rigidity ratio and density ratio of the patch and the host plate have been considered. For geometrical parameters, area ratio and thickness ratio of the patch and the host plate have been considered. The location of the bonded elastic patch has been offset to study the influence of geometry on the modal frequencies. It has been found that these parameters significantly influence the modal frequencies. The results have shown that the shift in the fundamental mode frequency for the case of a central patch is larger than that of the offset patch. For a given area of the patch, the modal frequencies first increase and then decrease for an increase in the patch thickness.