Shape design sensitivity analysis (DSA) and optimization methods for the fatigue life of thermoelastic structural components are presented in this paper. A multiaxial fatigue life prediction method is used for crack initiation. The crack initiation life prediction is modeled using constant amplitude strain-life data and cyclic stress-strain curves. A hybrid DSA method is used for the fatigue life. The design sensitivities of the dynamic stress and the temperature field are obtained using analytical approaches. The design sensitivity is used to predict the dynamic stress and temperature of the perturbed design. Using predicted stress and temperature, the fatigue life of the perturbed structural design component is predicted. The predicted fatigue life is then used to obtain the design sensitivity of the fatigue life by utilizing the finite difference method. The proposed DSA method is applied to design optimization of an automotive exhaust manifold of an automotive vehicle, considering crack initiation lives as design constraints.

Issue Section:
Design Theory and Methodology
Topics:
Durability, Optimization, Shape design, Thermoelasticity, Design, Fatigue life, Fracture (Materials), Stress, Temperature, Analytical methods, Automobiles, Exhaust manifolds, Finite difference methods, Sensitivity analysis, Stress-strain curves, Structural design, Structural elements (Construction)
1.
Dems, K., “Sensitivity Analysis in Thermoelasticity Problems,” Computer Aided Optimal Design: Structural and Mechanical Systems, pp. 563–567, 1987.
2.
Tortorelli
D. A.
,
Subramani
G.
, and
Lu
S. C. Y.
, “
Sensitivity Analysis for Coupled Thermoelastic Systems
,”
Int. J. Solids and Structures
, Vol.
27
, No.
12
, pp.
1477
–
1497
,
1991
.
3.
Lee
B. Y.
, and
Kwak
B. M.
, “
Axisymmetric Thermoelastic Shape Sensitivity Analysis and its Application to Turbine Disc Design
,”
International Journal for Numerical Methods in Engineering
, Vol.
33
, pp.
2073
–
2089
,
1992
.
4.
Collins, J. A., Failure of Materials in Mechanical Design, John Wiley & Sons, 1993.
5.
Bannantine, J. A., Fundamentals of Metal Fatigue Analysis, Englewood Cliffs, N.J., 1990.
6.
DRAW Concept Manual, “Durability and Reliability Analysis Workspace,” Center for Computer-Aided Design, College of Engineering, The University of Iowa, Iowa City, IA, 1994.
7.
Choi
K. K.
, and
Haug
E. J.
, “
Shape Design Sensitivity Analysis of Elastic Structures
,”
J. of Struct. Mechanics
, Vol.
11
, No.
2
, pp.
231
–
269
,
1983
.
8.
Haug, E. J., Choi, K. K., and Komkov, V., Design Sensitivity Analysis of Structural Systems, Academic Press, New York, NY 1986.
9.
Choi
K. K.
,
Chang
K. H.
, “
A Study of Design Velocity Field Computation for Shape Optimal Design
,”
Finite Elements in Analysis and Design
, Vol.
15
, pp.
317
–
341
,
1994
.
10.
Chang
K. H.
,
Choi
K. K.
, “
A Geometry-Based Parameterization Method for Shape Design of Elastic Solids
,”
Mech. Struct. & Mach.
, Vol.
20
, No.
2
, pp.
215
–
252
,
1992
.
11.
Chang
K. H.
,
Yu
X.
,
Choi
K. K.
, “
Shape Design Sensitivity Analysis and Optimization for Structural Durability
,”
Int. J. of Numerical Methods in Engineering
, Vol.
40
, pp.
1719
–
1743
,
1997
.
12.
Reddy, J. N., Gartling, D. K., The Finite Element Method in Heat Transfer and Fluid Dynamics, CRC Press, 1994.
13.
DRAW User’s Reference, “Durability and Reliability Analysis Workspace,” Center for Computer-Aided Design, College of Engineering, The University of Iowa, Iowa City, IA, 1994.
14.
Sokolowski, J. and Zolesio, J. P., Introduction to Shape Optimization, Springer Verlag, 1992.
15.
Arpaci, V. S., Conduction Heat Transfer, Addison-Wesley Publishing Company, 1966.
16.
Bejan, A., Convection Heat Transfer, John Wiley & Sons, 1984,
17.
ANSYS User’s Manuals, Revision 5.2, Vol. I, II, III, IV, ANSYS, Inc., P.O. Box 65, Johnson Road, Houston, PA, 1995.
18.
ANSYS Heat Transfer User’s Guide, Revision 5.1, ANSYS, Inc., P.O. Box 65, Johnson Road, Houston, PA, 1995.
19.
P3/PATRAN User Manual, Vol. 1–4, PDA Engineering, 1994.
20.
Chang
K. H.
,
Choi
K. K.
,
Tsai
C. S.
,
Chen
C. J.
,
Choi
B. S.
, and
Yu
X.
, “
Design Sensitivity Analysis and Optimization Tool (DSO) for Shape Design Applications
,”
Computing Systems in Engineering
, Vol.
6
, No.
2
, pp.
151
–
175
,
1995
.
21.
Vanderplaats, G. N. and Hansen, S. R., DOT User’s Manual, VMA Engineering, 1992.
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