Page 260 - Handbook of Materials Failure Analysis

256 CHAPTER 10 A reliable analysis method

5 CONCLUSION
A comprehensive approach to predict the structural strength of large excavators is
introduced. The method is validated by employing a heavy mining shovel. The
shovel front-end flexible FEA model is created. The loads applied on the model
are determined from the external loading and acceleration. The stress-time history
of each structural element is obtained using transient dynamic analysis. The case
analyses are presented to validate the method, where comparisons of equivalent
SRs between the dynamic analysis with the static analysis or field test are conducted.
The fatigue lives at hot spots are predicted.
It can be concluded that the dynamic analysis gives a more economic, reliable,
and safety confidence in the shovel front-end stress simulation. The front-end struc-
ture has created a flexible multi-body virtual prototype. The dynamic stress-time
history has been captured during the simulating virtual reality shovel operation.
Comparing the methods between the virtual prototype analysis and the physical
prototype analysis, it can be seen that the former spends less money and time than
the latter. Comparing the hot spot SRs from dynamic analysis and static analysis, it
can be seen that the dynamic character is missed and not reflected from the static
analysis. Comparing the hot spot SRs from dynamic analysis and field test, it can
be seen that the former gives larger SR than the latter. With the validated model,
the fatigue lives at hot spots are calculated, which is useful to determine design
change in the front structure.
This research provides an efficient method for the investigation of mining equip-
ment structural strength. Future research will create submodels for further structural
fatigue life evaluation.

NOMENCLATURE

D damping
DASR dynamic analysis stress range
λ Lagrange multipliers
FEA finite element analysis
ı ˆ generalized coordinates
K generalized stiffness matrix
m crack growth rate constant
M generalized mass matrix
n i number of cycles accumulated at stress range σ i
N i number of stress cycles to failure at stress range σ i
n v equivalent number of stress cycles at equivalent stress range σ v
N v equivalent number of stress cycles to failure at equivalent stress range σ v
ξ kinematic constraint equations applied to the flexible body
Q generalized applied forces
SASR static analysis stress range