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柴油机关键件螺栓连接组合结构非线性力学特性研究

发布时间:2019-01-08 14:14
【摘要】:由于垫片材料的非线性及组合结构各部件之间接触的非线性等多重非线性特性的影响,使得螺栓连接组合结构的力学特性变得较为复杂。为了研究组合结构整体力学特性,本文对螺栓法兰垫片连接组合结构的非线性静动力学建模方法、组合结构的准静态密封特性和动力学响应机理等进行了研究,具体研究内容包括:1)考虑垫片材料非线性及各部件之间的接触非线性,建立了组合结构非线性静力学有限元模型。得出了不同装配连接工艺下螺栓残余预紧力及垫片接触压力仿真计算结果。与试验测试结果进行了对比,验证了仿真计算模型及计算结果的正确性,得到了满足组合结构密封特性要求的最优螺栓装配连接工艺。2)考虑气缸垫材料非线性及接触非线性,建立了柴油机关键件组合结构非线性静力学有限元模型。研究了不同装配连接工艺对柴油机气缸密封特性的影响,得到了满足该高强化柴油机气缸密封特性要求的最好缸盖螺栓装配连接工艺,为高强化柴油机关键件组合结构气缸密封特性的现代设计提供了指导。3)提出了无垫片及采用不同材料垫片的螺栓法兰连接组合结构,计算了不同组合结构的预应力模态响应频率与振型。通过与相应的组合结构模态试验进行对比,确定了模态仿真计算结果的准确性。计算结果表明:与采用线弹性材料的铝合金垫片相比,采用石墨填充金属缠绕垫片,组合结构前两节弯曲模态频率分别减小了13.5%和13.7%;组合结构轴向具有不同的拉压模态。4)发现了组合结构轴向整体刚度具有明显的拉压非线性特性;提出将组合结构的螺栓连接部位简化等效为轴向双弹簧-弯曲梁解析模型,发现了组合结构螺栓连接部位在轴向也具有拉压非线性刚度特性;当组合结构无垫片或者采用线弹性材料的铝合金垫片时,其轴向拉压刚度都呈双线性关系;当采用非线性材料的石墨缠绕金属垫片时,其轴向拉压刚度呈现很强的非线性关系。5)将组合结构简化为弹簧-质量系统,建立系统的振动控制方程,求解振动方程可知:在轴向载荷作用下,组合结构只产生轴向振动。在横向载荷作用下,当弹簧轴向刚度分别为常数或者刚度为位移的一次函数且振动控制方程的质量矩阵耦合时,组合结构只产生横向转角振动,当弹簧轴向刚度分别为位移的一次函数且振动控制方程的质量矩阵不耦合、弹簧刚度为双线性和刚度为位移的二次函数时,组合结构产生横纵耦合振动。在轴向和横向耦合冲击作用下,组合结构也产生横纵耦合振动。6)将垫片材料非线性及各部件之间的接触非线性转化为弹簧的轴向刚度非线性,建立了螺栓法兰垫片连接组合结构的轴向拉压非线性刚度简化动力学有限元模型;在轴向和横向载荷分别作用下,对组合结构简化动力学模型进行了有限元仿真计算,得到了组合结构轴向及横向振动特性。结果表明:简化动力学模型的有限元计算结果与机理模型的解析分析结果具有较好的一致性。设计了组合结构瞬态动力学冲击试验,验证了所提出的组合结构非线性简化动力学模型和机理分析模型的正确性,并在现象上验证了动力学机理模型的理论预测。7)采用非线性弹簧单元,对某高强化柴油机关键件组合结构的缸盖螺栓连接部位进行重新建模,将弹簧单元的轴向刚度非线性纳入到柴油机关键件组合结构的整体动力学分析中;对该柴油机关键件组合结构进行了整体动力学计算;首次预测出在轴向冲击下组合结构只出现较大的轴向位移,在横向冲击下组合结构产生横纵耦合振动;验证了本文的提出的非线性简化动力学建模方法更为安全可靠。
[Abstract]:The mechanical properties of the bolt-connecting composite structure become more complex due to the influence of the non-linearity of the gasket material and the non-linearity of the contact between the components of the combined structure. In order to study the overall mechanical properties of the composite structure, this paper studies the nonlinear static dynamic modeling method of the bolt flange gasket joint structure, the quasi-static sealing property and the dynamic response mechanism of the combined structure, and the specific research contents include: 1) Considering the non-linearity of the gasket material and the contact non-linearity between the components, the nonlinear static finite element model of the composite structure is established. The residual pre-tightening force of the bolt and the simulation result of the contact pressure of the gasket are obtained. compared with the test results, the correctness of the simulation calculation model and the calculation result is verified, and the optimal bolt assembling and connecting process satisfying the requirements of the sealing property of the combined structure is obtained. The nonlinear static finite element model of the key combination structure of the diesel engine is established. The influence of the different assembly connection technology on the sealing property of the cylinder of the diesel engine is studied, and the best cylinder head bolt assembling and connecting process which meets the requirements of the sealing property of the cylinder of the high-strength diesel engine is obtained. This paper provides the guidance for the modern design of the cylinder sealing property of the key parts of the high-strength diesel engine. 3) The combination structure of the bolt flange with the gasket and the gasket with different materials is put forward, and the response frequency and the vibration mode of the pre-stressed mode of the different combined structure are calculated. The accuracy of the modal simulation results is determined by comparing the modal test with the corresponding combination structure. The results show that the two bending mode frequencies of the composite structure are reduced by 13. 5% and 13. 7%, respectively, compared with the aluminum alloy gasket using the linear elastic material. the axial integral stiffness of the combined structure is found to have obvious pull-and-pressure non-linear characteristics, and the simplified equivalent of the bolt connection part of the combined structure is an axial double-spring-bending beam analysis model, and when the composite structure is not provided with a gasket or an aluminum alloy gasket with a wire elastic material is adopted, the axial tensile and pressing rigidity of the composite structure bolt is in a bilinear relation, and when the graphite of the non-linear material is used for winding the metal gasket, The axial tensile and compressive stiffness of the system presents a strong nonlinear relation. 5) The combined structure is simplified as a spring-mass system, and the vibration control equation of the system is established. under the action of transverse load, when the axial stiffness of the spring is constant or the stiffness is a displacement function of the displacement and the mass matrix of the vibration control equation is coupled, the combined structure only generates transverse angular vibration, When the axial stiffness of the spring is a displacement function and the mass matrix of the vibration control equation is not coupled, and the spring rate is a quadratic function of the linear and the stiffness as the displacement, the combined structure generates transverse and longitudinal coupling vibration. under the action of axial and lateral coupling impact, the combined structure also generates transverse and longitudinal coupling vibration. The simplified dynamic finite element model of the axial pull-and-pressure nonlinear stiffness of the bolt-flange gasket-connection composite structure is established, and the simplified dynamic model of the combined structure is calculated by the finite element simulation under the action of the axial and transverse loads respectively, and the axial and lateral vibration characteristics of the combined structure are obtained. The results show that the finite element calculation results of the simplified dynamic model and the analytical results of the mechanism model have good consistency. The transient dynamic impact test of the combined structure is designed, and the correctness of the proposed nonlinear simplified dynamic model and the mechanism analysis model of the combined structure is verified, and the theoretical prediction of the dynamic mechanism model is verified. The cylinder head bolt connection part of the key part combination structure of a high-strength diesel engine is re-modeled, and the axial stiffness non-linearity of the spring unit is taken into the integral dynamic analysis of the key component combination structure of the diesel engine, and the integral dynamic calculation of the key component combination structure of the diesel engine is carried out; For the first time, a large axial displacement of the combined structure under the axial impact is predicted, and the horizontal longitudinal coupling vibration is generated by the combined structure under the transverse impact, and the proposed nonlinear simplified dynamic modeling method is more safe and reliable.
【学位授予单位】:北京理工大学
【学位级别】:博士
【学位授予年份】:2015
【分类号】:TK421

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