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Monte-Carlo-Analysis of Minimum Burst Requirements for Composite Cylinders for Hydrogen Service
(2021)
For achieving Net Zero-aims hydrogen is an indispensable component, probably the main component. For the usage of hydrogen, a wide acceptance is necessary, which requires trust in hydrogen based on absence of major incidents resulting from a high safety level. Burst tests stand for a type of testing that is used in every test standard and regulation as one of the key issues for ensuring safety in use. The central role of burst and proof test is grown to historical reasons for steam engines and steel vessels but - with respect for composite pressure vessels (CPVs) - not due an extraordinary depth of outcomes. Its importance results from the relatively simple test process with relatively low costs and gets its importance by running of the different test variations in parallel. In relevant test und production standards (as e. g. ECE R134) the burst test is used in at least 4 different meanings. There is the burst test on a) new CPVs and some others b) for determining the residual strength subsequent to various simulations of ageing effects. Both are performed during the approval process on a pre-series. Then there is c) the batch testing during the CPVs production and finally d) the 100% proof testing, which means to stop the burst test at a certain pressure level. These different aspects of burst tests are analysed and compared with respect to its importance for the resulting safety of the populations of CPVs in service based on experienced test results and Monte-Carlo simulations. As main criterial for this the expected failure rate in a probabilistic meaning is used. This finally ends up with recommendations for relevant RC&S especially with respect to GTR 13.
The damage process of short glass fibre (30% weight) reinforced polyamide caused by mechanical loading was investigated from the beginning on micro cracking level to the incipient crack of mm-dimension. Based on high resolution computer tomography and the X-ray-refraction technique the inner surface due to micro-cracking at the short fibre ends and the fibre matrix debonding of the skin surface of the filament was determined quantitatively. With the knowledge of the fatigue crack propagation rate and fracture toughness of the material from former research projects, it was derived that the total inner surface due to micro cracks measured by X-ray refraction is much higher than the specimen could have withstand the load, supposed the surface is in a localized crack. Hence, the damage process could be described from micro to macro level. Accompanying fractographic investigations endorse the modelling based on the NDT-techniques.
Im Rahmen der Energiewende erfahren viele Produkte einen umfassenden Markthochlauf. Hierzu müssen neue Technologien entwickelt oder bestehende in kurzer Zeit angepasst werden. Das macht sie besonders anfällig für Zwischenfälle und nachfolgenden Akzeptanzverlust. Zu vermeidende Zwischenfälle hängen oft von den deterministischen Mindestanforderungen in Norm und Recht ab, die erfahrungsbasiert entwickelt wurden. Hier ist die Monte-Carlo-Simulation eine wertvolle Hilfe. Sie erlaubt, auf der Basis von wenigen ermittelten Daten zu bewerten, welche statistische Wirkung aus einer Mindestanforderung resultiert und was angepasst werden muss, um die im Zuge eines Markthochlaufes relevanten Zielgrößen zu erreichen. Ein Verfahren, das im Rahmen der Normung erlaubt, die Wirkung einer Mindestanforderung auf die Ausfallwahrscheinlichkeit zu bewerten, wird zurzeit im Rahmen des Projektes DIN/TS 19472 unter dem NA 016-00-03 AA ausgearbeitet und hier vorgestellt.