发动机排气岐管疲劳强度及试验研究

发布时间：2018-01-16 11:38

本文关键词：发动机排气岐管疲劳强度及试验研究　出处：《重庆交通大学》2016年硕士论文　论文类型：学位论文

【摘要】：发动机排气歧管的工作条件非常恶劣,歧管表层气体温度与内腔中气体的温度相差很大,并且长期处于循环交变载荷作用下,非常容易导致疲劳失效等现象的出现,继而促使发动机废气排放的增多、功率波动、噪声变大、甚至引起发动机失效。本文采用理论分析、仿真分析及发动机总成台架实验验证相结合的方法,对发动机排气歧管的热疲劳、振动以及疲劳强度问题进行了研究,从而找出发动机排气歧管寿命薄弱处并对其进行结构优化。本文的主要内容如下:(1)根据前期工程试验的结果,结合基本疲劳强度理论,判断出发动机排气歧管破坏的可能方式与位置,根据判断结果有侧重的,忽略对分析结果影响很小的次要结构,建立发动机排气歧管模型用于分析。(2)利用CATIA软件对发动机排气歧管进行三维模型的建立,结合HYPERMESH软件对发动机排气歧管划分网格模型进行自由模态分析,根据结构的模态分析对比结果,排除共振对排气歧管寿命的影响,找出影响疲劳强度的关键因素。(3)利用ABAQUS软件对发动机排气歧管有限元模型进行热应力分析,基于应力分析结果,找出发动机排气歧管结构的应力集中处和最大应力大小。之后以降低结构应力集中现象为目的对模型进行修改,修改后再次进行仿真分析。(4)利用CATIA软件,根据HYPERMESH的模态分析结果和ABAQUS的热应力分析结果对排气歧管进行结构上的优化,建立优化后的有限元模型。对优化后的模型施加与优化前相同的边界条件再次进行模态分析和热应力分析。最终排除了排气歧管因共振引起断裂的可能,判断为因局部应力集中而引起排气歧管断裂。仿真分析发现结构优化后的排气歧管应力值比之前降低了8.7%,修改后的模型理论上满足强度条件。利用Ncode软件对结构修改前后的模型进行寿命分析,对两次分析结果进行对比,发现修改后的排气歧管寿命相比之前提高了大约34%,满足试验要求的疲劳条件。(5)根据国家标准GB/T 18297-2001《汽车发动机性能试验方法》、GB/T19005-2003《汽车发动机强度试验方法》,某集团企业标准《发动机性能试验大纲》、《发动机测试规范》等相关技术要求搭建试验台架,进行400h的可靠性试验并采集相关数据,同时进行30000km路试试验,最后对实验结果进行分析。
[Abstract]:The engine exhaust manifold working conditions are very bad, the gas manifold surface temperature and air temperature in the inner cavity of the difference, and in the long-term effect of alternating load, very easily lead to fatigue failure phenomenon, and then make the engine exhaust emissions increased, power fluctuation, noise and even cause engine failure. This paper uses the theoretical analysis, simulation analysis method and engine assembly bench experiments combined with the thermal fatigue on the engine exhaust manifold, vibration and fatigue strength are studied, so as to find out the weak point and the life of the engine exhaust manifold to optimize the structure of it. The main contents of this paper are as follows: (1) according to the pre engineering test the results, combined with the basic theory of fatigue strength, determine the possible ways of engine exhaust manifold and the failure position, according to the judgment result and focuses. Just a small effect on the secondary structure analysis results, the establishment of engine exhaust manifold model used for the analysis. (2) the establishment of the engine exhaust manifold three-dimensional model using CATIA software, the free modal analysis of the engine exhaust manifold mesh model with the HYPERMESH software, according to the analysis results of the modal structure, eliminate the resonance effect on the exhaust manifold life, to find out the key factors affecting the fatigue strength. (3) the finite element model of the engine exhaust manifold for thermal stress analysis using ABAQUS software, based on the result of stress analysis, find out the motivation of exhaust manifold structure stress concentration and the maximum stress. After the structure to reduce the stress concentration phenomenon for the purpose of amendment the model simulation analysis again revised. (4) by using CATIA software, according to the stress analysis results of modal analysis results of HYPERMESH and ABAQUS heat To optimize the structure of the exhaust manifold, the established finite element model after optimization. Applying the same before optimization of boundary conditions on the optimized model is again analyzed. Modal analysis and thermal stress eventually ruled out the exhaust manifold caused by resonance fault may judge due to local stress concentration caused by the exhaust manifold fault simulation analysis. The exhaust manifold found the optimized structure of the stress value was 8.7% lower than before, the modified model theory to meet the strength conditions. For life analysis on the structure of the model before and after modification by Ncode software, the two analysis results were compared, found that the modified exhaust manifold life increased by about 34% compared to the previous meet the conditions, the fatigue test requirements. (5) according to the national standard GB/T 18297-2001< automobile engine performance test methods ", test method of automobile engine strength GB/T19005-2003< >, a set of Group enterprise standard, engine performance test outline, engine test specification and other related technical requirements, build the test bench, carry out 400H reliability test and collect relevant data, and do 30000km road test at the same time. Finally, the experimental results are analyzed.

【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.134.4

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