Coupled Dynamic-Fatigue Analysis of a Haulpak 730E

Coupled Dynamic-Fatigue
Analysis of a Haulpak 730E
load box
for Kumba Resources
by Alex Veldtman
of Investmech (Pty) Ltd
Background: What is a Haulpak ?
Payload: 230 000 kg
Fly wheel power: 1388 kW
The goal of the project
• What we needed to do:
– A structural integrity assessment the load box to
determine if the aluminium floor structure of the load
box could be replaced with a steel plate
The scope of the project
• This is what we did:
– Accelerations at the chassis interface points were
recorded during normal operation
– The data was analyzed to obtain the dynamic loading
– A durability mission profile was defined
– Dynamic analysis
– Fatigue analysis
A closer look at the load box
The recorded data
• Accelerometers were placed at the various
interface points with the load box
– Vertical accelerations of the chassis near the two rear
hinge points of the load box were recorded
– Vertical accelerations near the front load box contact
pads
• Why not measure strain?
Data analysis
• The accelerations were analyzed:
Data analysis (continued)
• And analyzed…
Data analysis (continued)
• And analyzed…
The mission profile
7 min 30s
Receiving
payload
8 min 20s
Driving with
no payload
14 min 54 s
Duty cycle
Driving with
payload
30 s
Emptying of
payload
Number of cycles = 37,000
Structural inputs
h2
36˚
36˚
A
D
E
B
h1
68˚
9.5˚
C
Side view of load box
Max( 0, 4280*9.81*( 'Z + min( ((3.14-abs('X))*tand(36)),((3.41-abs('Y))*tand(31)) ) ))
h2
h1
b
Front view of load box
Breakdown of the analysis procedure
• Coupled dynamic-static stress analysis:
– The finite element model was created in MSC.Patran
– A flex body was generated with MSC.Nastran
– The load vs. time history was determined using
MSC.Adams
– The fatigue damage was calculated using
MSC.Fatigue
Breakdown of the analysis procedure
The finite element model
First stage of improvements to the model
• Some results from the finite element model
The dynamic model
Side view of the load box
Gravity
Load box centre of
gravity
Contact Plane
Revolute joint
Z
X
Rigid bodies subjected to
forced displacement input
Dynamic Loading
• The model is loaded using a modal load
– The load is scaled by the centre of mass acceleration
Results from the dynamic analysis
Fatigue analysis
Load versus
time history
Mission profile
Stress versus time
data
Mode 1
Fatigue
Analysis
Rainflow cycle
counting
And damage
summation
Mode 1
S-N data
Modal stress
characterization
Life in
repeats
Use of the mission profile in MSC.Fatigue
Mission profile event
Duration of time signal
Duration of the event
Amount of repeats
Receiving of the load
2s
-
5
Driving with the payload
2s
894 s
447
Tipping of the load
Static load case
-
1
Driving without the payload
2s
500 s
250
Conclusion
• Very low fatigue damage!