Numerical Simulation of the
Propagation of a Crack in Gearbox Crack
Lin Liu, Suri Ganeriwala
SpectraQuest Inc., 8201 Hermitage Road, Richmond, VA 23228
Published: Aug, 2005
Abstract
In this technical note, fracture propagation is
simulated using a finite element model for a gearbox which is
designed for a rotor dynamic test rig. The circumferential plates of
the gearbox are welded along the side as well as the bottom edges.
Micro-cracks are usually generated at weld toes and the welding
process will introduce residual stresses. The effect of the
locations of initial fracture on fracture propagation path is
studied.
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Introduction
SpectraQuest Inc. specializes in
design, development and fabrication of gearbox system for
diagnostics and prognostics researches. Upon request from a custom,
we have performed a numerical simulation of crack propagation in a
gearbox. The gearbox is installed in the Gearbox Dynamic Simulator.
The gearbox is made of six
aluminum plate. Each one of the four circumferential plates is
welded with one another. Furthermore, the circumferential plates are
welded to the bottom plate. The top plate is bolted to the
circumferential plates.
Gearbox Model
The end plate of the gearbox facing the direction
of the rotor "B" assembly is modeled in the work. The geometry of
the plate is a 14 by 14 inches square with a 3 inches radius hole in
the center. The thickness of the plate is 0.5 inches. Because of the
small thickness of the plate, it can be considered as a plane stress
problem and two dimensional finite element model is created using
FRANC2D software.
The finite element model is displayed in Figure
3. There are total of 800 Q8 quadrilateral elements. The bottom edge
is constrained both in the x and y directions. The
assumed load is a node load applied at the uppermost node in the
hole in the y direction with amplitude of 200 lb.
An edge fracture is introduced on the left side
of the plate with different initial locations. The three fracture
initial locations studied in the work are displayed in Figure 3. The
lengths of three initial fractures are all 0.21 inches. And the
initial crack direction is horizontal for all the three cases.
Fig 1:
Gearbox in Gearbox Dynamic Simulator
Fig 2: Finite Element Model of Plate
Fig 3: Deformed Mesh for First Crack
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