Investigation of Creep Fatigue Crack Propagation In Aluminium Tube K. A. Mohammad 1,a , Aidy Ali 1,b , A. Oshkour 1,c , B. B. Sahari 1,2,d and S. Abdullah 3,e 1 Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang Selangor, Malaysia. 2 Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 UPM, Serdang Selangor, Malaysia. 3 Department of Mechanical and Materials Engineering, Universiti Kebangsaan Malaysia, Bangi, 43600 UKM Bangi, Selangor, Malaysia. a k.amohd@yahoo.com, b aidy@eng.upm.edu.my, c azim_120@yahoo.com, d barkawi@eng.upm.edu.my, e shahrum@eng.ukm.my Keywords: Aluminium Alloys, Creep Crack Growth, Creep Fatigue, Pressure Tube Surface Flaw Abstract. Tubular structure is extensively used from domestic to aviation kind of applications. Life and safety are most considered in designing tube structure that against failure. For the last 200 years of research output and understanding, it was estimated that about 90% of metal failures were due to the external or surface defect and environmental attacks. The present work had focused on damage tolerant fatigue life prediction on aluminium cylindrical structures. Endurance tests were conducted with a constant amplitude repetitive loading at both, in room and high temperatures. A notch is introduced by wire cut machined on external surface and in a straight line with circumferential orientation to represent an external defects and flaws. Crack growth rates were measured by imaging technique. The experimental results suggested that the creep fatigue life is shorter than conventional fatigue life. The effect of stress ratio is also presented. The fully reversed with high temperature results registered the most severe damage with tremendous of life reduction. Introduction In many engineering components thermo-mechanical loading does occur, e.g. turbines blades, cylinder heads, pipes, exhaust manifolds in combustion engines. Indeed, many methods have been developed to describe the life time behavior under thermo-mechanical, especially with the latest, thermo-mechanical fatigue life assessment of aluminium components using Sehitoglu model [1]. However, in this fatigue model, oxidation and creep damage were considered with approximately 20 parameters involved. Yet again, the model was originally developed for 1070 steel, it shows the robustness for predicting life of aluminium alloy. Environment assisted fatigue crack growth mechanics that analyse the environmental effects during creep fatigue crack growth in aluminium alloy for supersonic aircraft was recently performed by Henaff et al. [2]. On the other hand, since 1988, Srivatsan [3] highlight that for aluminium alloy that subjected to high temperature low cycle fatigue exhibits a nonlinear plastic strain fatigue life relationship. The creep was registered for responsible to the reduction in fatigue life. Furthermore, the work suggested that the contribution to fatigue life reduction by creep and environmental effects was magnified by the applied stress. In short, it is evident that the temperature is one of the major factors that affect the fatigue characteristic specifically the fatigue strength of low carbon steel or any other materials. The method to determine fatigue strength of any mechanical parts that are subjected to cyclic stresses depends on the nature or the intended purpose of their utilization. In other word it relied on their design philosophy. The finite life or stress-life (S-N) approach is the most common in applications, which require live span of the parts to fall in high-cycle fatigue (HCF) region, compared to the Key Engineering Materials Vols. 462-463 (2011) pp 541-546 © (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.462-463.541 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 119.40.118.243-14/12/10,08:53:06)