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Accelerated life evaluation of vehicle has become the order of the day with the continuously decreasing development time for product development. With the rapid progress in the computer aided design area, today it is possible to feed-in virtual test tracks so that even before a prototype is made, a life estimate could be arrived at. Further, the advent of rapid prototyping has also resulted in reducing the time required for development of prototypes considerably. This has put the proving engineers under tremendous pressure in reducing the time required for design validation. This has resulted in a number of techniques being developed for reducing number of tests required as well as test duration in validation of the prototypes. One such technique is non-square matrix simulation. This technique can also be used for the investigation of failures and validation of the modifications.

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.

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.

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.