Research On The Evaluation Technology Of Manufacturing Process Reliability For Weak-rigid Marine Diesel Engine Block

As one of the key structures of marine diesel engine,the processing quality of engine block directly affects the performance and service life of diesel engine.With the increasing demand of diesel engine performance,the requirement of quality for diesel engine block is higher and higher.However,the complex structure of the body of the diesel engine makes some positions appear weakly rigid,which leads to the phenomenon of flutter and knife jump.In order to better guarantee the machining quality of diesel engine block,the research on the process reliability of block is becoming more and more important.At present,the research on reliability mainly focuses on the design and service of diesel engine,and there is little research on the reliability of machining process,and the research on analyzing the machining process of block from the perspective of process reliability to ensure the quality of diesel engine block processing is lacking.In view of the above problems,this paper comprehensively analyzes the machining process of diesel engine blocks from the point of view of reliability.Firstly,the key processes of the blocks were analyzed qualitatively by using PFMECA method.For the weak links of blocks which can be quantifiable analyzed,the process weak links were analyzed by finite element method and orthogonal test design to screen the key factors affecting machining quality,and the prediction models of machining quality were established by using BP neural network.Then,on the basis of establishing the evaluation index of the reliability of machining process,the processing reliability of process weak links was evaluated by Monte Carlo method,and the mathematical model of the reliability of machining process for whole block was established by the reliability block diagram method to evaluate the reliability of machining process of block.Finally,the analysis and optimization system of the reliability of machining process for diesel engine blocks was developed.The specific research contents are as follows:(1)The machining process of marine diesel engine block was analyzed to determine the key processes of blocks,and carried out the PFMECA analysis to determine the process weak links of engine block.Fuzzy comprehensive evaluation is used in PFMECA analysis to solve the problem of low resolution of traditional PFMECA analysis results.(2)For the process weak links which can be quantifiable analyzed,the DEFORM-3D software and ABAQUS software was used to establish the simulation models of processweak links,and the factors that have significant influence on the machining quality of process weak links were screened through orthogonal test analysis.Then,the prediction models of machining quality were established by using BP neural network.(3)According to the actual situation of the machining process of diesel engine blocks,the process reliability indexes of block were established,and the processing reliability of the process weak links of block was evaluated by Monte Carlo simulation and probability statistics theory,and the error-free judgment probability of feature was introduced to correct the influence of the inspection misjudgment.The mathematical model of the reliability of machining process for whole block was established by the reliability block diagram method to evaluate the reliability of machining process for whole block.(4)The feasibility analysis and requirement analysis of the analysis and optimization system of the reliability of machining process for diesel engine blocks were carried out.Then,according to the theoretical research results,the structure and the database of the system were designed,and the theory and technology were applied to the system,which provides guidance for better ensuring the machining quality of the blocks.