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Technical Paper

Development of Methodology to Perform Dual Side Roof Strength Analysis Using Virtual Tools

The purpose of Federal Motor Vehicle Safety Standard 216 is to reduce fatalities and serious injuries when vehicle roof crushes into occupant compartment during rollover crash. Upgraded roof crush resistance standard (571.216a Standard No. 216a) requires vehicle to achieve maximum applied force of 3.0 times unloaded vehicle weight (UVW) on both driver and passenger sides of the roof. (For vehicles with gross vehicle weight rating ≤ 6,000 lb.) This paper provides an overview of current approach for dual side roof strength Finite Element Analysis (FEA) and its limitations. It also proposes a new approach based on powerful features available in virtual tools. In the current approach, passenger side loading follows driver side loading and requires two separate analyses before arriving at final assessment. In the proposed approach only one analysis suffices as driver and passenger side loadings are combined in a single analysis.
Technical Paper

Evaluation of Cabin Comfort in Air Conditioned Buses Using CFD

The objective of the work presented in this paper is to provide an overall CFD evaluation and optimization study of cabin climate control of air-conditioned (AC) city buses. Providing passengers with a comfortable experience is one of the focal point of any bus manufacturer. However, detailed evaluation through testing alone is difficult and not possible during vehicle development. With increasing travel needs and continuous focus on improving passenger experience, CFD supplemented by testing plays an important role in assessing the cabin comfort. The focus of the study is to evaluate the effect of size, shape and number of free-flow and overhead vents on flow distribution inside the cabin. Numerical simulations were carried out using a commercially available CFD code, Fluent®. Realizable k - ε RANS turbulence model was used to model turbulence. Airflow results from numerical simulation were compared with the testing results to evaluate the reliability.
Technical Paper

Hardware-in-Loop for all Types of Hybrid Vehicles using Open Modular Hardware to Meet ISO 26262 Standard

Hardware-in-the-Loop (HIL) simulation is a technique used extensively in the development and testing of complex real-time embedded systems. Most of the HILs built around the world focus on specific part of a vehicle. This paper describes an in house HIL system developed for the complete hybrid car. In this HIL, the focus was to have HIL based on open hardware which is low cost and modular. It is customizable as per complex interdisciplinary vehicle requirements from Original Equipment Manufacturer that reduces dependency on suppliers and allows testing in an integrated vehicle environment. Code for operating HIL is developed in house. This HIL allows engineers to access ECU and plant model simultaneously and generate test report automatically. It consists of a vehicle plant model developed using MathWorks® Tool chain-MATLAB and Simulink. FPGA Plugin consist of software implementation of vehicle sensors in LabVIEW™ software from National Instruments (NI).
Technical Paper

Structural Evaluation of Ashcan and Performance Enhancement by Spring Optimization

Ashcan contributes to the aesthetics and elegance of the vehicle interiors. It is used to store the ash. Generally the ashcan is fitted on the console of the car. The operational requirement of ashcan is to open with minimum force but not at very low accelerations experienced during the vehicle bump event. Also closing force should be comparatively higher. The closing of the ashcan lid should ensure positive locking, which may be achieved by using cam and follower locking mechanism. The other requirement is that it should be structurally durable enough to sustain the repetitive loading during its operation. Ashcan may undergo severe abusive loading during its operation. To simulate these operations and understand the physics of the problem, a multi-step non-linear analysis involving a complex contact situation is carried out. The scope of this paper is to explain the procedure of calculating the force required for closing and opening of the ashcan lid.
Technical Paper

Development of Exhaust Silencer for Improved Sound Quality and Optimum Back Pressure

For an automotive exhaust system, noise level and back pressure are the most important parameters for passenger comfort and engine performance respectively. The sound quality perception of the existing silencer design was unacceptable, although the back pressure measured was below the target limit. To improve the existing design, few concepts were prepared by changing the internal elements of silencer only. The design constraints were the silencer shell dimensions, volume of silencer, inlet pipe and outlet tailpipe positions, which had to be kept same as that of the existing base design. The sound quality signal replaying and synthesizing was performed to define the desired sound quality. The numerical simulation involves 3D computational fluid dynamics (CFD) with appropriate boundary condition having less numerical diffusions to predict the back pressure. The various silencer concepts developed with this preliminary analysis, was then experimentally verified with the numerical data.
Journal Article

Influence of Vehicle Front End Design on Pedestrian Lower Leg Performance for SUV Class Vehicle

Accident statistics shows pedestrian accident fatalities as one of the important concerns globally. In view of this, new test protocols for pedestrian safety have been drafted in regulation as well as in consumer group. Also as per new ENCAP requirements, pedestrian safety assessment is used as one of the four assessment criteria's (Adult protection, child safety, pedestrian safety, safety assist) in deciding the overall vehicle safety. Hence today importance of pedestrian safety is perceived as never before in vehicle development program. Basically pedestrian safety evaluation involves subsystem level (head form, upper leg form and lower leg form) impact tests representing human body parts, at specific region on test vehicle with injury limits to decide the severity of impact. In general these injuries are governed by vehicle styling, vehicle stiffness, hard points clearances from vehicle exterior like bonnet, bumper etc.
Technical Paper

Pedestrian Head Form and Lower Leg Impact Sensitivity Study Through CAE Simulations

Pedestrian impact test procedures allow tolerances on test conditions of impact such as mass of the impactor, impactor position, impact speed etc. The variation in these parameters affects the injury measurements in a test. This paper focuses on sensitivity study of variations in these parameters, within specified tolerances, on head form impact and lower leg impact injury measurements. The aim of this sensitivity study is to find out the most influencing test parameter for the injuries. The exercise was carried out using Computer Aided Engineering (CAE) simulations.
Technical Paper

A Study on Improvements in Side Impact Test vs CAE Structural Correlation

Computer Aided Engineering (CAE) plays an important role in the product development. Now a days major decisions like concept selection and design sign off are taken based on CAE. All the Original Equipment Manufacturers (OEMs) are putting consistent efforts to improve accuracy of the CAE results. In recent years confidence on CAE prediction has been increased mainly because of good correlation of CAE predictions with the test results. Defining proper correlation criteria and using a systematic approach helps significantly in building the overall confidence level for predictions given by CAE simulations. Representation of manufacturing effects on material properties and material failure in the simulation is still a big challenge for achieving a good CAE correlation. This paper describes side impact test vs CAE correlation. The important parameters affecting the CAE correlation were discussed.
Technical Paper

CAE Simulation of Door Sag/Set Using Subsystem Level Approach

The performance of door assembly is very significant for the vehicle design and door sag/set is one of the important attribute for design of door assembly. This paper provides an overview of conventional approach for door sag/set study based on door-hinge-BIW assembly (system level approach) and its limitation over new approach based on subassembly (subsystem level approach). The door sag/set simulation at system level is the most common approach adopted across auto industry. This approach evaluates only structural adequacy of door assembly system for sag load. To find key contributor for door sagging is always been time consuming task with conventional approach thus there is a delay in providing design enablers to meet the design target. New approach of door sag/set at “subsystem level” evaluates the structural stiffness contribution of individual subsystem. It support for setting up the target at subsystem level, which integrate and regulate the system level performance.
Technical Paper

Development of Cost Effective Non-Permeable and Leak-Proof Air Inlet System Ducting for Turbocharged Intercooled Modern Diesel Engine

The modern trend of engine downsizing for CO₂ reduction coupled with stringent emission norms compel the engine air inlet system to outperform the conventional designs. Modern turbo diesel engine air inlet system handles higher & higher air flow, boost pressure and temperature. Air inlet system ducting designs have become complex due to oil particles (received through PCV system), engine movement and isolation for NVH. Air inlet ducting failures; like oil mist leakage through joints and seepage through hose wall cause high engine oil consumption and most predominantly environment damage. Also to some extent boost leakage in certain operating conditions. These failures reduce the reliability and performance of engine in certain conditions. This paper discusses design and development of cost-effective non-permeable and leak-proof hose-piping system for turbocharged diesel engine where PCV system was connected to air inlet system.
Technical Paper

Material Characterization of Polymers Using CAE and Correlation with Tests

Progress in material research is the driving force behind innovative ideas and characterising the newly invented material accurately is need of the hour. Increased use of polymers in automobile industry has led to the need for accurately capturing polymer material properties. In case of polymers, we generally observe negative slope in true stress strain curves due to inherent material behaviour. It is mainly because of polymer chains which realign/untangle in the direction of load. This is a challenge when we characterise polymers material properties to be used in LS_DYNA software, which is widely used in automotive applications to solve dynamic crash events. This software does not allow negative slope in stress strain curves in the plastic region and that causes model instabilities. This paper explains the methodology to avoid negative slope and still characterise the polymers without significantly loosing on the accuracy and correlation to physical tests.
Technical Paper

FE Prediction of Thermal Performance and Stresses in a Disc Brake System

The brake system is one of the most critical systems in the automotive vehicle. Its design is a challenging task since stringent performance and packaging requirements are to be fully met - optimizing the brake performance and weight of the brake system. The brake disc is an important component in the braking system which is expected to withstand and dissipate the heat generated during the braking event. Validation of brake disc design through CAE/FEA is presented in this paper. The procedure for prediction of thermal performance was developed in-house, tuned and verified by correlating with Test data available for existing-design and then applied to the new-design brake disc. The correlation achieved for the existing-design brake disc (both solid and ventilated), procedure for prediction of thermo-mechanical performance (heat transfer coefficient estimation, temperature distribution etc.) are also included.
Technical Paper

Vehicle Level Acoustic Sound Pack Sensitivity and Test Correlation by Utilizing Statistical Energy Analysis (SEA) Technique for Premium SUV

Due to increased awareness by customer perceived sound characteristics, advance simulation technique emerged in NVH domain for mid-high frequency like BEM, Hybrid and Statistical Energy Analysis (SEA). One of the most widely and accepted practice in high frequency NVH is SEA technique to assess and optimize acoustic sound pack for Air Borne Noise (ABN) in the range of 400 Hz to 6300 Hz typically for Powertrain and Tyre Patch Noise Reduction. As Prof. Lyon states that “The most obvious disadvantage of statistical approaches is that they give statistical answers, which are always subject to some uncertainty” [1]. It is always challenge for SEA engineer to get correlation for full vehicle level model for Tyre Patch Noise Reduction (TPNR) and Powertrain Acoustic Transfer Function (PT ATF) to acceptable level. Appropriate correlated SEA model is developed and few challenges associated with SEA modeling are also discussed in this paper.
Technical Paper

Mathematical Model to Evaluate and Optimize the Dynamic Performance of Pneumatic Brake System

Pneumatic brake system is widely used in heavy truck, medium and heavy buses for its great superiority and braking performance over other brake systems. Pneumatic brake system consists of various valves such as Dual Brake Valve (DBV), Quick release Valve (QRV), Relay Valve (RV), Brake chambers. Dynamics of each valve is playing a crucial role in overall dynamic performance of the braking system. However, it is very difficult to find the contribution of each valve and pipe diameters in overall braking performance. Hence, it is very difficult to arrive a best combination for targeted braking performance as it is not possible to evaluate all combination on the actual vehicle. Hence, it is very important to have a mathematical model to optimize and evaluate the overall braking performance in early design phase. The present study is focusing on the mathematical model of a pneumatic brake circuit.
Technical Paper

Reduce Cost of Product Design using Unit FE Simulation

The unit analysis methodology can be used for designing component or product in a product development process. This method may be used for designing the crush can, bumper beam, crush can long member, B-frame or A-pillar in frontal impact analysis. Unit assembly model technique can be effectively used in many CAE load cases to evaluate CAE simulations such as pedestrian impact analysis (ECE R78 / ENCAP), interior trim related head impact simulations (FMVSS201U), under run protection simulation for commercial vehicles (Front Underrun Protection Device ECE R93, Rear Underrun Protection Device ECE R58, Side Underrun Protection Device ECE R73), airbag deployment optimization etc. These CAE analyses correlate better with actual test. This paper gives idea about how the cost of product design can be reduced by using unit analysis. To reduce time of vehicle development such as cost of prototype, testing cost, optimization cost unit analysis is more economical.
Technical Paper

The Cyclic Strain Life Physical Test Correlation Using CAE

Fatigue life predictions using the strain-life method are used in the design of modern light weight vehicle, for the complex loading that occur with the structural durability tests that these vehicles undergo. The accuracy of these predictions is dependent upon the many factors; geometry, loads & materials etc. This paper details a new procedure to ensure the quality and accuracy of the material parameters for the fatigue life prediction software. The material parameters for the solver are obtained by performing strain-controlled fatigue tests. The geometry of the coupons tested is determined by size and thickness of the material specimen that they are machined from and the loading regime in the test. Detailed data analyzed is conducted on these tests and the parameters that are used as input into the CAE strain-life fatigue prediction software are generated.
Technical Paper

Sensitivity Analysis of Windshield Defrost Characteristics Impact on Occupant Thermal Comfort

During cabin warm-up, effective air distribution by vehicle climate control systems plays a vital role. For adequate visibility to the driver, major portion of the air is required to be delivered through the defrost center ducts to clear the windshield. HVAC unit deliver hot air with help of cabin heater and PTC heater. When hot air interacts with cold windshield it causes thermal losses, and windshield act as sink. This process may causes in delay of cabin warming during consecutive cabin warming process. Thus it becomes essential to predict the effect of different windscreen defrost characteristics. In this paper, sensitivity analysis is carried for different windscreen defrosts characteristics like ambient conditions, modes of operation; change in material properties along with occupant thermal comfort is predicted. An integrated 1D/3D CFD approach is proposed to evaluate these conditions.
Technical Paper

Optimization of Sheet Metal Bracket by Use of Thermoplastics

Reducing overall weight of the vehicle is one of the main areas of research in automotive industries. Current trend, CO2 reduction, is a major incentive for this process. For this, engineers are finding out various ways to reduce weight to strength ratio of the different components. The immediate pay-off of such developments is lower fuel consumption, which is followed by lower CO2 emissions. For this engineers opt for, use of low-density and high-strength materials, along with optimization of the geometry of the components. One of the solutions is to convert metal parts to plastics which have desired properties. The main focus of this paper is to convert the sheet metal brackets to plastic brackets which will ultimately reduce weight and production cost associated with automobile. In this paper, an optimum process, using Topology optimization and Mold Flow Analysis, is developed to convert sheet metal bracket to plastic bracket.
Technical Paper

Adhesive Failure Prediction in Crash Simulations

Structural adhesive is a good alternative to provide required strength at joinery of similar and dissimilar materials. Adhesive joinery plays a critical role to maintain structural integrity during vehicle crash scenario. Robust adhesive failure definitions are critical for accurate predictions of structural performance in crash Computer Aided Engineering (CAE) simulations. In this paper, structural adhesive material characterization challenges like comprehensive In-house testing and CAE correlation aspects are discussed. Considering the crash loading complexity, test plan is devised for identification of strength and failure characteristics at 0°, 45°, 75°, 90°, and Peel loading conditions. Coupon level test samples were prepared with high temperature curing of structural adhesive along with metal panels. Test fixtures were prepared to carryout testing using Instron VHS machine under quasi-static and dynamic loading.
Technical Paper

An Analysis on Automotive Side Window Buffeting Using Scale Adaptive Simulation

Automotive window buffeting is a source of vehicle occupant’s discomfort and annoyance. Original equipment manufacturers (OEM) are using both experimental and numerical methods to address this issue. With major advances in computational power and numerical modelling, it is now possible to model complex aero acoustic problems using numerical tools like CFD. Although the direct turbulence model LES is preferred to simulate aero-acoustic problems, it is computationally expensive for many industrial applications. Hybrid turbulence models can be used to model aero acoustic problems for industrial applications. In this paper, the numerical modelling of side window buffeting in a generic passenger car is presented. The numerical modelling is performed with the hybrid turbulence model Scale Adaptive Simulation (SAS) using a commercial CFD code.