SIMULASI PERAMBATAN RETAK LELAH PADA POROS AISI 1045 YANG DIKENAI BEBAN DINAMIK LENTUR AMPLITUDO TEGANGAN KONSTAN
Abstract
The current research was carried out to study the change of stress intensity factor (KI) on the semielliptical cracked crank subject to a constant amplitude cyclic loading. This research was also carried out to find the fatigue crack propagation model, the critical crack depth and to predict the fatigue life. The study was performed by using computer modeling and simulation, verified by series of fatigue tests on 15 mm diameter rod specimens made of AISI 1045 steel. The crack (0.5 mm) was introduced on the specimen surfaces as a crack initiation site. The result shows that, for the same crack depth, the higher the loading magnitude, the higher the stress intensity factor, and also, at the end of the crack propagation, semi-elliptical crack tends to be semi-circular one, or a/c ratio approaching unity (1.0). The fatigue experiment has been successfully verified that the critical crack depth and the fatigue life lie within 89% to 92% accuracy, and 8% to 10% deviation , respectively, compared to those obtained by the computer simulation. Fractography study has also revealed that the fracture path consist of; i) crack initiation site, ii) crack propagation, as indicated by beach mark, and iii) the final fracture.
References
Spotts, M.F., Design of Machine Elements, 6th Edition, Prentice Hall, Englewood Cliffs, N.J., 1985.
H.O. Fuchs, and R.I. Stephens, Metal Fatigue in Engineering, John Wiley & Sons, New York and Singapore (1980).
H. P. Bloch and F. K. Geitner, Machinery Failure Analysis and Trobleshooting, Gulf Publishing Company, Houston and London, (1986).
W. S. Blackburn, Calculation of stress intensity factor for straight grooved and ungrooved shafts, Engng Fracture Mech. 8, 731-736, (1976).
H. Nisitani, Behavior of Small Cracks in Fatigue and Relating Phenomena in T. Tanaka, et.al. (ed), Current Research on Fatigue Cracks, Vol. 1, Elsevier Applied Science, London and New York, (1987).
T. Lorentzen, N.E.Kjaer and T.K. Hendrikson, The application of fracture mechanics to surface crack in shafts. Engng Fracture Mech. 23, 1005-1014 (1986).
K. D. Thompson and S. D. Sheppard, Stress intensity factors in shafts subjected to torsion and axial loading, Engng Fracture Mech. 42, 1019- 1034 (1992).
Encu Saifudin, Kaji Eksperimental Pengaruh Retak Melintang Buatan pada Poros Terhadap Prilaku Dinamika Rotor, Tesis Magister, Program Pascasarjana,Institut Teknologi Bandung, (1999).
ASM, Metal Handbook: Failure Analysis and Prevention, Vol.10, ASM, The Metal Park, (1992).
D. Broek, The Practical Use of Fracture Mechanics, Kluwer Academic Publishers, Dordrecht and London (1988).
R. C. Shah and A.S. Kobayashi, On the surface flaw problem in, The surface crack: physical problem and computational solution, J.L. Swedlow (ed.), ASME, New York, 1972.
Tokyo Fatigue Equipment, Pte. Ltd., Fatigue Rotating Bending Constan Amplitude Manuals, Tokyo Fatigue Equipment Ltd., Tokyo (1992).
