| Institution: | 1. Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore 117576, Singapore;2. MHP Systems Engineering, 4718 Hallmark Drive, Suite 702, Houston, TX 77056, USA;1. VTT Technical Research Centre of Finland Ltd., P. O. Box 1000, FI-02044 VTT, Kemistintie 3, Finland;2. Aalto University, Department of Mechanical Engineering, Otakaari 4, Espoo, Finland;1. School of Materials Science and Engineering, Shandong University, Jinan 250061, China;2. School of Materials Science and Engineering, Shandong Jianzhu University, Jinan 250101, China;1. Instytut Spawalnictwa Gliwice, Electronic Welding Devices Department, B?. Czes?awa 16-18, 44-100 Gliwice, Poland;2. Wroc?aw University of Technology, Faculty of Mechanical Engineering, Institute of Machine Technology and Automation, ?ukasiewicza 5, 50-371 Wroc?aw, Poland |
| Abstract: | This paper reports a new incidence of brittle failure by lamellar splitting in a large-scale tubular X-joint and examines the possible causes of this failure. The X-joint, with multiple pre-existing fatigue cracks at the weld toe along the brace-to-chord intersection, experiences brittle failure during a monotonic in-plane bending test. Post-test sectioning of the material around the brace-to-chord intersection reveals lamellar splitting in the mid-thickness of the chord wall instead of rapid extensions of the fatigue cracks in the through-thickness direction. The lamellar splitting observed in this test differs from the conventional lamellar tearing both in its appearance and in its causes. The elongated nonmetallic inclusions concentrated at the mid-thickness, as revealed by the microscopic scanning, leads to delamination cracking near the mid-thickness and subsequently to the brittle failure of the joint. The material requirements in prevailing engineering codes do not suffice to prohibit the lamellar splitting failure observed in this study, which may cause catastrophic failures in engineering structures designed with insufficient redundancy. |
