# Analysis of Powertrain Loading Dynamic Characteristics and the Effects on Fatigue Damage
## 1 Introduction  
With the improving of testing and simulation techniques and the rising demands for the vehicle durability and economy, the fatigue damage analysis technique based on loading spectrum is widely used in reliability and lightweight design. [PERSON] et al. [1] examined the effects of the material fatigue properties, stress, or strain results in predicting fatigue life and discussed various mean stress corrections and different methods of accelerating fatigue analysis, along with their advantages and disadvantages. [PERSON] et al. [2] analyzed the operation conditions and working load on the transmission input shaft of an agricultural tractor and discussed the severereness to the transmission of the loading spectra obtained from the different operations. [PERSON] et al. [3] represented the relative fatigue damage analysis technique with the loads of the powertrain system obtained from measurement to analyze the revolution counting for the endurance. Loading spectrum for fatigue damage analysis is mainly obtained from durability test and computer simulation. In the aspect of durability tests, [PERSON] [4] described the criteria and the main parameters of loading spectrum used for design and testing and discussed the procedures to determine these spectra and the requirements concerning the reliability. [PERSON] et al. [5] discussed the analytical methodology and fundamental technical information useful in vehicle powertrain durability testing. [PERSON] et al. [6] presented the multi-criteria decision-making technology to estimate the minimum sample size of the load on a wheel loader transmission under multiple operating conditions. [PERSON] et al. [7] developed a complete vehicle loading spectrum test and data processing method based on the specific circumstances of the Indian market. [PERSON] et al. [8] defined a methodologyto reproduce of real customer tractor usage of tractors in accelerated structural tests. [PERSON] et al. [9] detailed the formulation of the method used by ArvinMeritor for developing a vehicle drive train component test bogey to support product design and development. In general, obtaining loading spectra by testing requires lots of time and cost. How to predict the fatigue loading spectrum accurately and efficiently by simulation has drawn the attention of researchers. At present, the studies on load spectrum simulation can be mainly divided into two methods: one based on virtual prototype and the other based on available data, which are usually typical condition testing loads or the data of similar models from database. In the case of simulation methods based on virtual prototype, [PERSON] et al. [10] developed a virtual powertrain model to simulate the powertrain endurance driving cycle, and the correlation between the predictions and test data collected on a vehicle that was driven through the same driving cycle at PG was made. [PERSON] et al. [11] predicted driveline component loading based on a complete PG schedule with a simulation model. [PERSON] et al. [12] presented a simple driveline model that was capable of simulating the accelerated endurance cycles as they ran on the PG or on the dynamometer. Then, the simulation results were compared with results of several real world drive cycles for the same vehicle category. In the case of the simulation method based on available data, [PERSON] et al. [13] presented a cyclic simulation approach to generate of the non-stationary loading histories of engineering vehicles based on the Markov chain Monte Carlo method. [PERSON] et al. [14] extrapolated the Rainflow matrix based on a multi-criteria decision-making method with which the proper upcrossing of the high and low levels was determined. [PERSON] et al. [15] compared two data reduction methods based on a simulated staircase test data and two extrapolation methods from shorter fatigue lives, and the results of simulated test were statistically evaluated. A powertrain system has assorted parts that form a complicated chain through various sorts of connections.