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)