【作者】 王健；

【导师】 张俊红；

【作者基本信息】 天津大学 ， 动力机械及工程， 2017， 博士

【摘要】 “节能”与“环保”是21世纪汽车工业发展道路上两大重要而紧迫的课题;塑料零部件成为发动机减振降噪和轻量化设计的双重利器。柴油机工作粗暴、热负荷大,对零部件结构强度和疲劳寿命提出了更高的要求,成为塑料零部件在柴油机上应用的主要瓶颈。因此,开展柴油机塑料零部件性能优化设计研究对塑料零部件长远发展具有重要意义。本文以纤维增强塑料各向异性建模为基础,从材料特性、振动噪声性能、疲劳可靠性以及注塑工艺参数多方面对塑料零部件性能进行系统研究,并进行相应的优化设计,全文主要研究工作如下:以单向板为研究对象,进行玻璃纤维增强PA66塑料材料特性研究;通过材料拉伸试验获取各向异性材料参数,通过构建各向异性材料弹性本构方程和模流分析,分别对材料参数和纤维取向进行定义;进行各向同性材料和各向异性材料性能对比分析,研究不同材料定义方式对结构性能和振动特性的影响;对塑料零部件结构设计要求进行介绍与分析,为接下来零部件设计与优化提供指导。基于EEMD(Ensemble Empirical Mode Decomposition)、相干功率谱和改进AHP(Analytic hierarchy process)方法进行柴油机噪声源识别,通过多转速、多测点、多频段的高精度系统识别研究,确定柴油机辐射噪声较大的零部件,结合零部件工作环境与工程塑料材料特性进行可塑化分析,最终确定柴油机塑料零部件优化设计的主要研究对象。以塑料机油冷却器罩盖为例,基于CFD(Computational Fluid Dynamics)分析结果,进行流体压力、温度场和耦合载荷场作用下的结构性能分析,对不同边界条件对塑料零部件结构性能的影响进行研究。通过模态试验结果验证模型构建的正确性,基于各向异性材料模型进行塑料零部件振动噪声特性研究,对不同预应力作用下的振动噪声预测结果进行仿真计算,从响应幅值、峰值频率和最大响应位置多方面进行对比分析,确定压力、热应力及耦合载荷对塑料零部件振动噪声特性的影响大小以及影响规律,根据分析结果进行多目标拓扑优化设计,取得了显著的降噪效果。此外,结合模态参与因子进行油底壳多目标形貌优化设计,采用多目标拓扑优化对塑料齿轮室罩盖进行低噪声设计,与金属材质零部件相比,在减重的同时有效降低了辐射噪声。根据柴油机塑料零部件强度低、易发生疲劳失效的特点,进行塑料零部件振动疲劳特性研究,通过计算不同预应力作用下的塑料零部件结构传递函数和振动疲劳寿命,分析了不同预应力对塑料零部件振动疲劳特性的影响;进行柴油机振动疲劳试验测试,从失效位置和疲劳寿命两方面验证塑料零部件振动疲劳预测结果的准确性;对失效位置进行结构优化设计,提升了零部件使用寿命。基于Opt LHD(Optimal Latin Hypercube Design)和EBFNN(Ellipsoid Basis Function)进行注塑系统浇口正时优化,通过方差分析对注塑工艺参数进行主效应分析、贡献度分析和交互效应分析,分析不同参数对注塑结果的影响,确定优化变量,进行基于MOPSO(Multiple Objective Particle Swarm Optimization)的注塑工艺参数多目标优化设计,确定了最佳注塑工艺参数,减小了产品变形量、降低了能耗并缩短了生产周期,综合提升了塑料零部件性能。更多还原

【Abstract】 “Energy conservation” and “environmental protection” are the two important and urgent major issues of the automobile industry development in twenty-first century.Plastic parts are the dual weapon for the vibration and noise reduction and lightweight design of the engine.As diesel engine works rough and the heat load is high,the plastic parts should have the high strength and long life.The high performance requirement comes to be the bottleneck of the plastic part application.Therefore,the research on the performance analysis and optimization design of low noise diesel engine plastic parts is significant to the application of plastic parts in the long-term development.Based on the anisotropic model of the fiber reinforced plastic,this paper carries out the systematic study and corresponding optimization in aspects of the material performance,vibration and noise characteristics,fatigue reliability and the injection molding process parameters.The main works can be concluded as follows:In the study on the material characteristics of the glass fiber reinforced PA66,the unidirectional plate is taken as the research object.The anisotropic material parameters are obtained through the tensile test of the material.The elastic constitutive equation of the anisotropic glass fiber reinforced plastic is constructed and the mould flow analysis of the square plate is carried out.Based on the above analysis,the material parameters and fiber orientation are defined.Then the performances of the isotropic materials and anisotropic materials are compared.The influence of the different material definition methods on the structural performance and vibration characteristic is analyzed.The structural design requirements of plastic parts are analyzed and introduced to provide guidance for the design and optimization of partsThe diesel engine noise source identification based on the EEMD,coherent power spectrum and improved AHP are proposed.Through the high precision and systematic identification research based on multiple speeds,measuring points and frequency bands,the main noise parts of the diesel are identified.Combined the components working environment and engineering plastics material characteristics,the feasibility of plastic parts is analyzed.The main research object of the optimization design of low noise diesel engine is finally determined.Based on the CFD analysis results,the structural performances of the plastic oil cooler cover under the pressure,the temperature and the coupled load are computed and the influences of the different boundary conditions are studied.Based on the anisotropic material model,the vibration and noise characteristics are researched.The vibration and noise results with different prestress are computed and they are compared in aspects of the response amplitude,peak frequency,and maximum response position.The effects and the influence rules of the pressure,thermal stress and coupled load are determined.According to the results,the multi-objective topology optimization design is performed and the good noise reduction results are obtained.Combined with the modal participation factors,the multi-objective morphology optimization design of plastic gear chamber cover is performed to reduce the radiated noise.The noise reduction of the plastic gear cover is realized with the multi-objective topology optimization.Compared with the metal parts,the radiation noise is reduced effectively while the weight is reduced.As the diesel engine plastic parts have the low strength and are prone to fatigue failure,the vibration fatigue characteristics of plastic parts are studied.Through the computations of the structure transfer function and vibration fatigue life with different prestress,the influence of different prestress on the vibration fatigue characteristics of plastic parts is analyzed.The engine vibration fatigue test is performed to vertified the prediction results in the two aspects of failure location and fatigue life.According to the fatigue prediction results,the corresponding structure optimization is conducted and the life of the plastic part is enhanced.Based on the Opt LHD and EBFNN method,the gate timing of injection system is optimized.Through variance analysis,the main effect,contribution and interactive effect of injection process parameters are analyzed and the optimization variables are determined.The multi-objective optimization design of injection process parameters based on MOPSO is conducted and the optimum process parameters are determined.The multi-objective optimization problem of the deformation reduction,low energy consumption and short production period is solved,and the comprehensive performance of the plastic parts is improved.更多还原