Accelerated Life Test Design for Tractor Powertrain Front Axle

MATEC Web of Conferences, Jan 2016

Accelerated Life Test (ALT) has been applied in the manufacturing for many years due to rapid changing technologies, more complex products, speedier product development, and more demanding customer requirements. These reasons have pushed the manufacturers to acquire reliability information faster. ALT allows reducing the time needed to show the reliability of the product. The purpose of this study is to design accelerated life testing which involved determination of normal test time, acceleration factor, acceleration test time, and finally experimental setup. This case study provides the basis for ALT designs for the tractor front axle based on customer usage and field failure analysis, which were conducted to estimate the current reliability, especially on the B10 life during the operational stage of the product. The accelerated life test conducted has guaranteed the B10 life of 4,000 hours with 90% confidence level for lesser time needed for testing to show the reliability of the front axle assembly.

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Accelerated Life Test Design for Tractor Powertrain Front Axle

MATEC Web of Conferences Accelerated Life Test Design for Tractor Powertrain Front Axle Azianti Ismail 1 Won Jung 0 Qiang Liu 0 0 Department of Industrial and Management Engineering, Daegu University , 712-714 Gyeongsan , South Korea 1 Faculty of Mechanical Engineering , Universiti Teknologi MARA Johor, Pasir Gudang campus, 81750 Johor , Malaysia Accelerated Life Test (ALT) has been applied in the manufacturing for many years due to rapid changing technologies, more complex products, speedier product development, and more demanding customer requirements. These reasons have pushed the manufacturers to acquire reliability information faster. ALT allows reducing the time needed to show the reliability of the product. The purpose of this study is to design accelerated life testing which involved determination of normal test time, acceleration factor, acceleration test time, and finally experimental setup. This case study provides the basis for ALT designs for the tractor front axle based on customer usage and field failure analysis, which were conducted to estimate the current reliability, especially on the B10 life during the operational stage of the product. The accelerated life test conducted has guaranteed the B10 life of 4,000 hours with 90% confidence level for lesser time needed for testing to show the reliability of the front axle assembly. 1 Introduction Engineers need to understand the usage environment, whereby the final product must endure to fulfil customer satisfaction. The response in an ALT is directly related to the lifetime of the product. Typically, ALT data is right censored because the test is terminated before all units fail. LuValle pointed out that it is likely to miss failure mode during accelerated testing efforts. This might happen if the true operating environments are not replicated during the test. It should be made to understand and to utilize the correct operating environment when planning and conducting accelerated testing to ensure minimum risk due to this consequence [1]. In the ALT, failures occurred more quickly from the actual environment in less time acquired. A controlled environment for the accelerated test was developed to simulate the use rather than testing in lengthy real-time tests. Important parameters for ALT are length of test, number of samples, confidence level, shape parameter (β), and acceleration factor. Campean et al. have discussed on a generic approach to life prediction modeling for automotive components, which aims to establish a correlation between the degradation mechanism, customer usage profile and rig life testing to design ALT [2]. Meeker et al. have mentioned that with good characterization of field use conditions, it may be possible to use ALT results to predict the failure distribution in the field [3]. On the other hand, Attardi et al. have presented case study regarding the reliability analysis of some automotive components based on field failure warranty data in which can be used to design ALT [4]. As for agricultural tractors, starting from the 1970s, studies were performed to estimate the fatigue life of a powertrain starting from a load spectrum derived from experimental measurements [5] and more recently, with the goal of estimating the loads during normal use of the tractor, defining the lifetime load spectra for agricultural transmissions [6]. The agricultural tractor market is constantly evolving, due to the changes caused by globalization that oblige farmers to reduce their production costs by using more specialized equipment and agricultural tractors. As a result, agricultural tractor manufacturers have to reduce time-to-market and development costs. Agricultural tractors are used for many kinds of farm work under various soil and field conditions. The most common tractor uses, however, are tillage and ploughing. To take into account of the workload in the design of the tractor powertrain, the operational characteristics of tractors such as annual working hours, working speed, engaged gears, and load distribution must be analyzed. It is particularly important to know the number of cycles of loads and their magnitudes under all working conditions. Furthermore, the agricultural environment adds additional factors that complicate the development of reliability improvement of agricultural vehicles; for example, the diversity of areas of operation, the presence of obstacles in fields, uneven terrains, and the varied number of tasks to be carried out. Equally, soil quality, variation of crop physical characteristics and environmental conditions such as rain, fog, and dust need to be considered [7]. Among the main components of the tractor, the powertrain manufacturing cost is one third of the total cost of the finished product. Therefore, a high percentage of cost reduction can be achieved through the improvement of the manufacturing process of the powertrain due to the re-evaluation of its reliability and durability, and through (...truncated)


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Azianti Ismail, Won Jung, Qiang Liu. Accelerated Life Test Design for Tractor Powertrain Front Axle, MATEC Web of Conferences, 2016, 74, DOI: 10.1051/matecconf/20167400020