| Modern vehicle design must take market as guidance, the product of design life excessive or insufficient is usually uneconomical and lacks market competition. So no matter in process of the vehicle design, development or test stage, should consider customer field usage. The vehicle reliability test is one important method, which inspects and evaluates whether the vehicles are durable or not. The traditional test basis is partial to the strength test, but not the life test. They are all in order to guarantee vehicle components haven't fracture under the worst operating condition, and also can satisfy the general project requirement. Obviously, these tests basically rely on the experience or custom, mainly depend on the extrapolation, but not base on the scientific principle. The domestic present reliability test specifications of automotive proving grounds are partial to simple, and the testing eligible products on proving ground can not guarantee satisfaction to customers, and neglected the influence of the operating order of the road categories on the structural fatigue life, so as to the failure regularity difference is obvious between the test results of proving ground and customer actual usage, separately fits the different probability distribution.In view of the above questions,the customer correlation reliability test technique was proposed, the technique considered real world customer field usage, compared with the traditional test method. Through the optimization and calculation of the correlation model between the customer and proving ground, can establish the reliability test specifications, which reflected the customer actual operating conditions, and provide a new method for vehicle reliability test.Combined with the Formulating Method of the Customer's Relevant Test Specifications of the Motor Truck Load Carrying Proving Ground and Formulation of the Reliability Test Specifications of the Main Automotive Assemblies in Nong'an Automotive Proving Ground, the key research projects of the Technological Center of China FAW Group Corporation, the research is carried out in the paper. A new method for customer correlation reliability test was proposed based on automotive proving ground, and the method can combine the real customer field usage to the vehicle with the enhancement test on proving ground, and avoid the test blindness. Aiming at the data that were tested on the typical road surfaces of the customer and enhancement roads of proving ground, the rain-flow counting method was used to obtain the load distribution matrixes , according to the correlation equation, the cumulative fatigue damage and loading spectrums of the 90% customer and proving ground were optimized and calculated. Through the correlation analysis of the test data, the road surface enhancement coefficient and the reliability test specifications of proving ground were obtained. The test results indicate that the new specifications can predict the potential failures of the load carrying structures quickly, shorten the test cycles, and reduce the test cost and new product development expense, compared with the existing test method.1. Research of the Customers Target Mileage CorrelationIn order to make the formulated test specifications able to truly reflect the customer's use, the on-site investigation of the actual use of the national relevant vehicles. According to the customer's data investigated, the MLE technique is applied to evaluate the Weibull parameters of the three typical road surfaces. The determined Weibull parameters and Miner cumulative damage rule are used to calculate the customer's total fatigue failure mileage of the load carrying structures of the even, moderately uneven and extremely uneven road surfaces. With the Monte-Carlo simulation, 90% of the customer's target mileage of the load carrying structures is available.2. Research of the Customer Correlation Reliability Test ProjectWith the analysis of the model stress and limit elements of the load carrying structures and experience, the critical dangerous positions of the structures. ADAMS and limit element fatigue software are used to carry out the fatigue analysis of the weigh beam and determine its weak position. According to the stress centralization principle of the electric resistance strain gage, stress, displacement and acceleration sensors of the loading structures are laid out. Considering the demand of the measuring precision, the engine suspension is designed and modified again to make it play the roles of suspension and sensor simultaneously.3. Research of the Correlation Test Model of Automotive Load Carrying System between Proving Ground and Customers UsageIn application of the least square method and combination with the fatigue cumulative damage and Basquin relation, the linear fitting of the fatigue life discrete data is made and the mathematical model of the S-N curve is obtained. The Goodman experience fatigue formula is used to equivalently transform the non-zero average stress to the zero average stress. The modified Neuber method and Manson-Coffin strain life curve equation are used to transform the nominal strain-time course to the local strain-time course and draw the double-log strain-fatigue life curve of the load carrying structures.4. Analysis and Disposal of the Customer Correlation Reliability test Data between Proving Ground and Customers UsageAccording to the principle of the customer's use correlation reliability test technology, the rain-flow matrix equivalent loading spectrum method is used to build the customer's use and proving ground correlation mathematical model, treat the test data of the customer and the proving ground and optimally calculate the proving ground strengthened road cycle indexes of the rain-flow matrix loading spectrum of 90% of the customer's and proving ground data. In line with the problems existing in the technical specifications of the traditional reliability test, according to the road loading spectrum correlation mathematical model of the customer and proving ground, the automotive load carrying reliability test specifications related to the customer's use are scientifically formulated, which provides the new test method for the determination of the new automotive products and reliability test.5. Simulation Analysis and Test Validation of the Customer Correlation Reliability Test MethodThe special test clamp is used to carry out the loading calibration of the key examined load carrying structures (front and rear axles, front and rear suspensions and weigh beams of the cabin). According to the equivalent life method of the fatigue test, the mathematical model of the acceleration coefficient of the key structures. The calculating procedure of the acceleration coefficient is used and the S-N curve is combined to calculate all the strengthened roads and the acceleration coefficient of the combined comprehensive road. The Visual C++ language is applied to formulate the automotive load carrying proving ground reliability life mileage evaluation software. The life evaluation software is used to evaluate the actual used life mileage of the automotive proving ground and the customer. The results show that the life mileage evaluated by the simulation evaluation software is basically consistent with the test results of use of the proving ground and the customer.
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