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Eingeladener Vortrag
- nein (148)
The objective of this work is to find a method that describes the degree of damage from an impact experiment. This experiment was performed on Composite Pressure Vessels (CPV) in order to find the correlation of impact damage to the residual burst pressure. Computed Tomography (CT) approach was used to capture the before and after impact condition of the CPVs. The Wasserstein function was used to calculate how much the after impact image has differed from the original one. In the end, a good correlation was obtained to the residual burst pressure.
The reduced volume method has found a particular zone to be used for evaluating the strength of unidirectional composite materials. To validate the method, modelling an experimental test where it has the same basic assumption of the model had been carried out. The result was favourable as the model can predict the average value from the experiment and also the time dependent effect.
The developed model has certain limitations of the element size to be used in the simulation to characterise the strength of composite materials. A reduced volume method is proposed in order to reduce the number of degree of freedom of the finite element simulation.This study has revealed certain configuration to be followed to speed up the computation time.
Defining a Reduced Volume Zone for the Simulation of Burst Test on a Composite Pressure Vessels
(2018)
The random nature of fibre break in composite materials has to be modelled in all part of the structure as it may contain millions of fibres. The reduced volume method was introduced to determine a smaller zone where we could characterise the strength based on the accumulation of fibre break, hence increasing the computation time
It is pertinent to have a correct description of fibre strength described by the twp parameter Weibull distribution when evaluating a type Iv pressure vessel using the fibre break multiscale model developed at Mines ParisTech. Earlier studies have shown a positive comparison result when T600S fibre strength were used. This study has discovered what would be the effect on the predicted strength when T700S strength is used.
The Reduced Volume Method (RVM) has been used to evaluate the multiscale fibre break model developed at Mines ParisTech. It allows the model to be assigned only at certain part of the structures without necessarily compromising the final prediction. An attempt to model a simple unidirectional composite structure has also been carried out and gave a satisfying result. This paper deals with the application of the RVM to real scale type IV composite cylinders, where its stacking sequence was evaluated through micro-CT scans conducted with the collaboration of the University of Southampton. Two modelling geometries were evaluated and compared with the corresponding experimental results.
The test data for static burst strength and load cycle fatigue strength of pressure vessels can often be well described by Gaussian normal or Weibull distribution functions. There are various approaches which can be used to determine the parameters of the Weibull distribution function; however, the performance of these methods is uncertain. In this study, six methods are evaluated by using the criterion of OSL (observed significance level) from Anderson-Darling (AD) goodness of Fit (GoF), These are: a) the norm-log based method, b) least squares regression, c) weighted least squares regression, d) a linear approach based on good linear unbiased estimators, e) maximum likelihood estimation and f) method of moments estimation. In addition, various approaches of ranking function are considered. The results show that there are no outperforming methods which can be identified clearly, primarily due to the limitation of the small sample size of the test data used for Weibull analysis. This randomness resulting from the sampling is further investigated by using Monte Carlo simulations, concluding that the sample size of the experimental data is more crucial than the exact method used to derive Weibull parameters. Finally, a recommendation is made to consider the uncertainties of the limitations due to the small size for pressure vessel testing and also for general material testing.
Determination of Distribution Function used in MCS on Safety Analysis of Hydrogen Pressure Vessel
(2019)
The test data of static burst strength and load cycle strength of composite pressure vessels are often described by GAUSSian normal or WEIBULL distribution function to perform safety analyses. The goodness of assumed distribution function plays a significant role in the inferential statistics to predict the population properties by using limited test data. Often, GAUSSian and WEIBULL probability nets are empirical methods used to validate the distribution function; Anderson-Darling and Kolmogorov-Smirnov tests are the mostly favorable approaches for Goodness of Fit. However, the different approaches used to determine the parameters of distribution function lead mostly to different conclusions for safety assessments. In this study, six different methods are investigated to show the variations on the rates for accepting the composite pressure vessels according to GTR No. 13 life test procedure. The six methods are: a) Norm-Log based method, b) Least squares regression, c) Weighted least squares regression, d) A linear approach based on good linear unbiased estimators, e) Maximum likelihood estimation and f) The method of moments estimation. In addition, various approaches of ranking function are considered. In the study, Monte Carlo simulations are conducted to generate basic populations based on the distribution functions which are determined using different methods. Then the samples are extracted randomly from a population and evaluated to obtain acceptance rate. Here, the “populations” and “samples” are corresponding to the burst strength or load cycle strength of the pressure vessels made from composite material and a plastic liner (type 4) for the storage of hydrogen. To the end, the results are discussed, and the best reliable methods are proposed.
Schrankenlos im Seeverkehr
(2014)
Aufgrund der wachsenden Internationalisierung des Flaschenparks stieg das Volumen im internationalen Gefahrguttransport in den letzten Jahren stark an. Gleichzeitig traten besonders im Mittelmeerraum Unwägbarkeiten im Landtransport durch politische Krisen auf. Das auf See gestiegene Transportvolumen und die verstärkte Beachtung der Rechtslage führte auch zu Fällen, bei denen deutlich wurde, dass ohne IMDG-Code-Zulassung kein Beförderungsanspruch ableitbar ist. Die zuständige Behörde - in Deutschland die BAM - bietet Lösungen mit erweitertem Nutzen an. Hier kann für Bestandsflaschen mit Landzulassung eine Verwendungserweiterung für den Seeverkehr beantragt werden.