Hyie, Koay Mei, Fracture Mechanics and Materials Integrity Research Group, College of Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia; Centre for Mechanical Engineering Studies, Universiti Teknologi MARA, Cawangan Pulau Pinang, Permatang Pauh Campus, 13500 Pulau Pinang, Malaysia, Malaysia