ISO test method and results on sustained-load-cracking resistance of aluminum cylinders

摘要

Leak as well as rupture types of failures related to sustained-load-cracking (SLC) have been observed in high pressure gas cylinders fabricated from certain aluminum alloys. The stable crack growth mechanism observed primarily in the cylinder neck and shoulder area have been identified as the SLC mechanism occurring at room temperature without any environmental effect. The International Organization for Standardization (ISO) Sub-Committee 3, Working Group 16 has developed a test method to measurethe SLC resistance using fracture mechanics specimens along with an acceptance criterion for aluminum cylinders. The technical rationale for the proposed test method and the physical significance of the acceptance criterion to the cylinder performance interms of critical stress-crack size relationship is presented. Application of the developed test method for characterizing new aluminum alloy for manufacturing cylinders is demonstrated. SLC characteristics of several aluminum cylinders as well ason-board cylinders for natural gas vehicles assessed by the authors are discussed.