Page 249 - Handbook of Materials Failure Analysis

1 Introduction 245

FIGURE 10.2
Simulated shovel boom failure.

efficient analysis technologies to monitor the overall stress loading of front-end struc-
ture to avoid fatigue failure.
The typical analysis methods used for mining excavator structural strength are the
field test, static analysis, and dynamic analysis [10–16]. Yin et al. [12] have analyzed
the fatigue life of cable shovel boom by employing field test data and finite element
analysis (FEA). Some researchers have identified the field test and static FEA as
valuable tools in fatigue evaluation of dragline boom. Using measured boom stress
data, Dayawansa et al. [13] have studied how the cracks grow in the weld joints in
order to protect booms from future catastrophic collapse. Using strain gage measure-
ments and static FEA model, Joshi et al. [11] have analyzed boom hot spot stresses to
monitor structural health. For the front-end structure, Li and Liu [14] have developed
a dynamic flexible model to detect component fatigue failure using multi-body
dynamics and the FEA method. This research demonstrates that the dynamic analysis
method can be less costly and more time efficient than the field test method, and also
can reflect the dynamic character of a structure, which is missed and not reflected
from static analysis. However, the research is focused on system dynamics modeling.
The structural dynamics modeling of dragline front-end was still in the preliminary
stage and the model validation was not addressed, which is necessary to verify the
simulation results.
The objective of this research is to apply the latest technological advances of
dynamic analysis to predict the large excavator fatigue life. As a case study, cable
shovel front-end strength analysis is addressed. First, the structural components
are described and the operation process is introduced. Second, a front-end flexible
model is created to calculate component stress-time histories by inputting a working
cycle loading. Third, the dynamic model is simulated and validated by comparing
the stress range (SR) with static analysis results and field testing results. Fourth,
the structural fatigue lives at hot spots are evaluated.