Search Results

With the stringent legislative requirements for noise in automobiles, gensets etc., the concern for properly designed silencers for specific applications is increasing. Optimized design of silencer requires an integrated study of acoustical and engine performance viz. Insertion loss and backpressure. However, the insertion loss itself depends upon engine characteristics geometry indicated by the transmission loss, flow induced noise, type of silencer - reactive, absorptive, hybrid, etc. Most of the work till date covers the acoustical and engine performance in isolation rather than in an integrated fashion due to the multidisciplinary nature of the problem. The objective of this study is to develop an integrated methodology to predict the performance of the silencer at the design stage resulting in an optimized time and cost effective design. In the present study, the acoustical and engine performance of silencer was predicted using FEM/BEM and CFD techniques.

Ever increasing demands for NVH related comfort have substantially reduced the exterior and interior noise of automobiles worldwide. This involves identification of the noise sources, paths of vibro-acoustic transfer paths and their reduction measures. Many a time, NVH is looked at after the product has been designed and even prototypes have been fabricated. The major source of noise in a vehicle is the driveline. Any changes in the driveline for noise optimization affect the performance as well as exhaust emissions of the vehicle. This makes the changes for improvement of NVH limited. One of the important criteria for the marketability of the vehicle is NVH. Hence, lot of development work is going on for noise reduction. The diesel engine plays a vital role in automobiles and agricultural equipments in the Indian scenario due to economic considerations.

Performance and emission tests have to be carried out on range of engines having wide applications and varied specifications. In this context situation compels to adopt critical measures and revamp the methodologies in the area of design and development / matching of cardon shafts, rubber couplings and development of test bed systems for testing of single / two cylinder engines. Considering this need, a new strategic design approach has been formulated, which have reduced cost, loss of time and serious damages. This paper outlines a modern and practical approach used along with in-house available tools for controlling various dynamic behavioral issues involved. Redesign of shafts and couplings is done based on the comprehensive mass elastic data obtained from variety of engines. Apart from conventional torsional and bending vibration theories, FE and experimental tools are used to understand the modal behavior of engine coupled systems.

The latest requirements for automotive cabin comfort require lower sound levels inside the cabin. There are many sources contributing to this noise of which fan is an important one. The blade passage noise of the cooling fan is often unpleasant and it is generally expensive to build and test different prototypes for optimum noise performance. Also, traditional unsteady computational approaches for predicting the fan noise are time and resource consuming and do not fit within the design cycle time. This paper proposes use of a steady state computational technique to predict the fan noise performance which provides for effective design study with optimum resources. The steady state data is used with the wave analogy to predict the overall sound pressure level. First, the computational results were validated with the experimental data for a base case and then parametric study was carried out to have optimum design.

With a number of vehicles being developed in the country and implementation of safety standards becoming mandatory, proving of a vehicle for safety is becoming an area of high priority in India. Keeping this in view, a gravity sled facility has been established at ARAI for simulated crash testing. This paper describes the facility and its establishment as well as the development of suitable stopping devices to meet various applications. The risk of injury to the occupants in the event of crash is severe when structural deformation/breakage occurs in the vehicle interior, seat anchorages and the restraint systems. A simulated crash test facility such as sled is used for the development of these systems and their evaluation. This is the prescribed procedure for certification. Instead of using a complete vehicle crash facility, use of a simulated crash facility becomes cost effective. The simulated crash facility described here uses the gravity principle for acceleration of sled.

The duration for the development of a new vehicle model is continuously decreasing. This does not permit adequate time for proving component assemblies and vehicles to be evaluated for durability by conventional measures. However, increasing competition and quality consciousness calls for an assured life with a high degree of confidence. This has forced the test engineers to look for techniques for accelerating the durability evaluation. The technique calls for concepts for compressing the evaluation time. This can be achieved by compression in both time as well as frequency domain. Further, it also calls for correct techniques for the mixing of roads, extrapolation of data acquired over a small distance to the vehicle life, evaluation and elimination of non or less damaging inputs, etc. This paper reviews some of the existing techniques and describes case studies of how accelerated testing can be applied in vehicle development.

One of the primary concern during assessment of structural integrity of vehicle bodies is the quality of joints used therein. The increased trend in vehicle weight reduction (through use of thin sheet panels) calls for more critical evaluation of the quality of such joints. The electric Resistance Spot Welding (RSW) is one of the largely used joining process for vehicle body structure. Besides the quality of sheet metal, the quality of RSW joints is largely governed by the process parameters e.g. weld current, hold time, squeeze time etc. The quality of RSW joints for durability can be assessed by mechanical strength and fatigue life. The paper presents a methodology for durability assessment of such joints using laboratory specimens and arriving at optimum values of process parameters to maximise the fatigue life. The methodology presented makes extensive use of Design of Experiment (DOE) techniques for better reliability of the results.

With increasing competition and number of global players entering the Indian market, the Indian tractor scenario is as hot and fluid as that of the passenger car. Tractor manufacturers are under tremendous market pressure to become internationally competitive and bring out new tractor models in the shortest time possible as well as keeping the validation costs to a minimum. This is making them to look for advanced techniques for reducing the development time such as service load data acquisition and analysis, life prediction and accelerated simulation tests for design validation. This paper presents such an effort by an Indian tractor manufacturer along with ARAL Design validation of the chassis was carried out as a complete structure instead of carrying out on individual components.

For high degree of engine performance, it is imperative that all critical parts are designed and optimised through durability assessment. The conventional engine development programme based on actual engine test on test bed is time consuming and expensive, and is being replaced by use of simulation tools and accelerated component testing. The present work is a systematic fatigue strength evaluation programme for connecting rod of an up-rated Naturally Aspirated, Direct Injection, Inline Diesel Engine The established staircase method of fatigue test is slightly modified to minimise the effect of scatter in the results and to arrive at a consistent and dependable factor of safety. Also analytical tools like Finite Element Analysis (FEA) and Statistical Techniques were used; which helped to keep design and tooling iterations to a minimum and facilitated connecting rod development in the given time frame.

With ever-increasing concern for the occupant safety, it is desirable that the design of truck cab should meet the safety requirements specified in ECE R-29. The cab must be designed in such a way that, sufficient survival space to be guaranteed in the event of accident for the safety of the driver and co-driver. It was found that there are some areas, which are not covered by the standard or the standard is not very clear. This paper discusses about the practical problems incurred during implementation of the standard in Indian scenario and also suggests possible practical solutions.

Strain controlled tests were performed on 35 C8 steel specimens (IS 3930-1979) to determine cyclic stress-strain curve (CSSC) by Companion Specimens Test (CST), Multiple Step Test (MST) and Incremental Step Test (IST) procedures. A good agreement was found between the CSSCs obtained by CST and MST procedures. The CSSCs obtained by IST procedure using Incremental Step Loading Blocks (ISLB) of different maximum strain amplitude indicate that the parameters of CSSC depend on the maximum strain amplitude in the ISLB and resulted in a family of CSSCs. The dependence of CSSC parameters on the maximum strain amplitude in the ISLB are approximated by polynomials. Fatigue lives estimated based on IST results for irregular strain-time histories were found to be comparable with the experimentally evaluated fatigue lives.

With increasing competition and globalization, the Indian Tractor Industry is gearing up to develop new proven design of tractors. The conventional methodology of trial and error design and its proving is becoming obsolete and practically too time consuming to meet the demands. Many designers are already in need of field data as the base for design. Prototype proving and reliability testing of the components and tractors in the laboratory has become the need of the day. All these requires quantification of service loads in the Laboratory. This paper describes in brief the methodology of these exercises, selection of instrumentation and data acquisition systems, typical problems of data acquisition on the tractors, based on the experience. This paper also provides illustrative examples of data acquisition and typical applications of the acquired data.

The acceptance criterion of any vehicle in terms of user comfort invariably depends on the vehicle interior noise and vibration characteristics. The levels of sound energy and structural excitation inside the vehicle compartment measures the amount of annoyance in terms of quality and comfort. For vehicle interior noise abatement and noise treatment, it is desirable to quantify the noise sources by determining the sound power contribution from each vehicle component/panel, acoustic leakages inside the vehicle, body panel vibrations, gearshift lever and steering wheel vibrations. Many a times, it is necessary to arrive at benchmarks or targets for the various sources of noise in order to refine the systems. The present paper describes a methodology for interior noise source identification and its analysis for benchmarking. Two different vehicles of the same class but of different makes were compared and evaluated for interior noise and vibration levels.

The transportation noise is one of the major sources of noise exposure in residential areas and causes substantial annoyance particularly during night. Considering this, many countries have enacted legislation limiting the noise levels in residential areas and also the noise levels emitted by vehicles. In India also, the Ministry of Environment and Forests enacted Environment (Protection) Rules through Air Pollution Act in 1986. Various international as well as Indian standards for vehicles consider two types of noise measurement viz., Pass-By Noise (PBN) and Stationary Noise (SN). There is a debate going on whether in-use vehicle noise should be considered as a parameter for the Inspection and Maintenance (I&M) regime, which is to be introduced shortly in India. A detailed study was conducted to understand the relation between PBN and SN for both new and in-use vehicles.