Crack Paths 2009

leaking however was observed on a limited ark of the outer cylinder perimeter, an

indication that possibly crack growth patters resembled the semi-elliptical surface crack

propagation schematically shown in Fig. 8b.

Figure 8. a) assumed crack propagation in cylinder,

b) semi-elliptical crack propagation.

C O N C L U S I O N S

A case of unexpected service failure of a heavy-duty hydraulic cylinder motivated the

present investigation and subsequent redesign activity. Fatigue fracture mechanics

concepts supported by finite element analysis were used to demonstrate that the in

service failure could have been predicted although the required methodologies are not

widespread among designers in industry. The same comcepts and tools were then

successfully used to develop and propose a re-design of the hydraulic cylinder requiring

limited modification to the original solution that increased the predicted service life of

almost an order of magnitude.

R E F E R E N C E S

1. Dowling, N.-E. (1993), Mechanical Behavior of Materials, Prentice Hall. 2. Suresh, S. (1998), Fatigue of Materials, 2nd Ed., Cambridge University Press

3. Liaw, P. K., Leaux, T.R., Logsdon, W.A. (1983), Near Threshold Fatigue Crack

Growth Behavior in Metals”, Acta Metallurgica, 31, 1581-7.

4. Fulland, M. , Sander, M., Kullmer, G., Richard H.A. (2008), Analysis of fatigue

crack propagation in the frame of a hydraulic press, Engineering Fracture

Mechanics 75 892–900

5. Ingraffea, A. R., Wawrzynek, P. A., "Finite Element Methods for Linear Elastic

Fracture Mechanics", Chapter 3.1 in Comprehensive Structural Integrity, R. de

Borst and H. Mang(eds), Elsevier Science Ltd., Oxford, England, 2003.

6. Qian, J., Fatemi, A. (1996) Mixed Mode Fatigue Crack Growth: A Literature

Survey, Engineering Fracture Mechanics, 55, 969-990.

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