Papers by Author: M. Abdul Razzaq

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Authors: M. Abdul Razzaq, Kamal A. Ariffin, Ahmed El Shafie, Shahrum Abdullah, Z. Sajuri, N.A. Akeel
Abstract: Artificial intelligence (AI) techniques and in particular, adaptive neural networks (ANN) have been commonly used in order to Fatigue life prediction. The aim of this paper is to consider a new crack propagation principle based on simulating experimental tests on three point-bend (TPB) specimens, which allow predicting the fatigue life and fatigue crack growth rate (FCGR). An important part of this paper is estimation of FCG rate related to different load histories. The effects of different load histories on the crack growth life are obtained in different representative simulation and experiments.
Authors: M. Abdul Razzaq, Ahmad Kamal Ariffin, Shahrum Abdullah, Z. Sajuri
Abstract: In this paper, fatigue crack growth rate (FCGR) analyses were conducted on compact specimens of an AISI 4340 alloy to study the behavior over a range in load ratios (0.1 ≤ R ≤ 0.95) and constant maximum stress intensity factor (Kmax) condition. Previous study had indicated that high R > 0.7 and constant Kmax test conditions near threshold conditions were suspected to be free of crack-closure and that any differences were caused by Kmax effects, from threshold to near fracture conditions. Cracks in high-cycle fatigue (HCF) components spend a large portion of their fatigue life near threshold conditions. In order to characterize the evolution of damage and crack propagation during these conditions, fatigue crack growth rate (FCGR) data at threshold and near-threshold conditions are essential in predicting service life and in determining the proper inspection intervals. Fatigue crack growth model, namely the Forman model were examined, this model implicit the effect of R ratio and ease of curve fitting to measured data. The Forman model may be suggested for use in critical applications in studying fatigue crack growth for different load ratios.
Authors: M. Abdul Razzaq, Ahmad Kamal Ariffin, Shahrum Abdullah, Z. Sajuri, A.E. Ismail, Azli Ariffin
Abstract: The life prediction information is useful for improving the component design methodology at the early developing stage. Many thick cylinders are subjected to complex cyclic loading spectrum ranging from small vibration to large load induction. This paper presents modeling of fatigue crack growth behavior in thick wall cylinder for outer surface cracked pipe subjected to internal pressure. There are many factors affecting fatigue crack growth such as; crack length, orientation of crack, thickens of the cylinder and the load ratio. Fatigue crack growth as consequence of service loads depends on many different contributing factors. With the help of a simulation fatigue crack growth in three-dimensional structures can either be predicted or explain for already existing failures. The simulation results showed that, more studies on the thick wall cylinder structure need to be performed in order to obtain more accurate fatigue life.
Authors: Al Emran Ismail, Ahmad Kamal Ariffin, Shahrum Abdullah, Mariyam Jameelah Ghazali, Ruslizam Daud, M. Abdul Razzaq, A. Zulkifli
Abstract: This paper presents a non-linear numerical investigation of surface cracks in round bars under tension stresses by using ANSYS finite element analysis (FEA). Due to the symmetrical analysis, only quarter finite element (FE) model was constructed and special attention was given at the crack tip of the cracks. The surface cracks were characterized by the dimensionless crack aspect ratio, a/b = 0.6, 0.8, 1.0 and 1.2, while the dimensionless relative crack depth, a/D = 0.1, 0.2 and 0.3. The square-root singularity of stresses and strains were modeled by shifting the mid-point nodes to the quarter-point locations in the region around the crack front. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under tension loading was assumed to follow the Ramberg-Osgood relation with n = 5 and 10. J values were determined for all positions along the crack front and then, the limit load was predicted using the J values obtained from FEA through the reference stress method.
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