Study On Consistency Evaluation Method For Manufacturing Quality Of Launch Vehicle Tanks Under Small Sample Condition

Launch vehicle tank is the pressure vessel that store and supply propellants for aerospace power systems,thus its manufacturing quality directly affects the flight performance and reliability of launch vehicle.In recent years,the development of launch vehicle products has promoted the development of related fields in manufacturing industry,which proposed the quantitative and accurate evaluation requirements for the consistency of manufacturing quality of typical key products including tank,in order to assisting in guiding the adjustment of production systems,the requirements for evaluation method which would be for quantitatively evaluating the consistency of manufacturing quality of typical key products including tank is proposed.However,current quality control method in engineering practice cannot effectively assess the consistency of manufacturing quality of launch vehicle products,which brought inconveniences in control and improvement of the consistency of manufacturing quality.In this paper,the launch vehicle tank was taken as the research object to propose a consistency evaluation method for manufacturing quality of aerospace product.An evaluation system of tank was established according to the functional characteristics and technical requirements of launch vehicle tank,and the consistency evaluation index for single manufacturing quality indicator within the system was clarified.Owing to that the sample size of tank test data was small,a consistency evaluation method for single manufacturing quality indicator was proposed based on the method integration and optimization.By adopting multi-indicator weight analysis method,a consistency evaluation method for integral manufacturing quality of tank was proposed.A prototype system for quality data and information management of aerospace product was designed for timely and accurate evaluation of manufacturing quality consistency.Main contents and innovations of this dissertation can be explained as follows:(1)Consistency evaluation method for single manufacturing quality indicator of tankAccording to the functional characteristics and technical requirements of launch vehicle tank,a manufacturing quality evaluation system was established,and the consistency evaluation index for single manufacturing quality indicator within the system was clarified.Owing to that the sample size of tank test data is very small,a Bootstrap point estimation method for consistency evaluation index was proposed on the basis of Monte Carlo simulation.By analyzing the distribution characteristics of estimation results,an improved strategy for correcting the estimation results with unbiased standard deviation estimation formula was proposed,which furtherly formed a consistent evaluation method for single quality indicator of tank,and achieved the quantitative evaluation of manufacturing quality consistency for single indicator.With the usage of statistical confidence evaluation method,the confidence level of consistency evaluation result for single quality indicator under different sample size conditions was quantified.(2)Optimization of consistency evaluation method for single manufacturing quality indicator of tankAccording to the defect that consistency evaluation method for single manufacturing quality indicator is difficult to obtain evaluation result with high confidence level under extreme small sample condition,a confidence optimization strategy that using modified grey prediction model to generate prediction data and extend the sample size,then evaluating with the extended sample was proposed.Grey prediction model was modified with the combination of data preprocessing method and genetic algorithms,and the accuracy of model and the rationality of prediction data was improved.At last,Monte Carlo simulations were conducted to verify that the optimization strategy can effectively improve the confidence level of consistency evaluation results.(3)Consistency evaluation method for integral manufacturing quality of tankTaking an oxidizer tank as the research object,the Monte Carlo simulation analysis model was constructed with 3D deviation analysis software VSA to determine the weight of each quality indicator.A multiindicator weighted fusion approach was adopted to propose the consistency evaluation method for integral manufacturing quality of tank,and the consistency of integral manufacturing quality was effectively quantified.(4)A prototype system for quality data and information management of aerospace productTo implement the theoretical methods described in previous section into engineering practice,a prototype system for aerospace product quality data analysis and information management was designed,which could provide the software support for assisting the manufacturing quality control and improvement of aerospace products.And basing on test data of tanks,the practicability of consistency evaluation method and corresponding prototype system were verified.