基于流体动压润滑理论的模具钢面微织构优化设计
发布时间：2019-04-18 13:59
【摘要】：摩擦与机械零件的可靠性、工作寿命以及能耗密切相关。合理的减小摩擦可使机械零件处于良好的工作环境,延长工作寿命,提高能量利用率,进而减小经济损失。自从表面微织构技术Laser Surface Texturing(LS T)作为一种新的改善摩擦副表面摩擦磨损性能的新方法问世后,便迅速受到国内外众多学者的青睐。如何设计出合理的微织构形貌和几何尺寸是发挥织构减摩性能的关键。本文结合理论、实验和模拟,对H13模具钢表面进行微织构优化和润滑机理研究,以满足该模具钢工况下的最佳摩擦学性能。主要研究成果如下:理论研究方面,分析了微凹坑改善润滑状态的原理,基于Reynolds方程建立了面面摩擦副表面织构的润滑模型,并探讨了模型的求解方法。然后采用计算流体动力学(CFD)中的FLUENT软件对润滑模型进行了数值分析,采用单因素法分析了微凹坑直径、深度、密度对润滑油膜的压力和压力分布的影响,结果表明,当凹坑直径为120μm时,具有最佳流体动压润滑效果的凹坑深度为13μm,凹坑直径100μm、深度10μm时,最佳面积占有率为13%。工艺实验方面,采用半导体泵浦YAG激光器在H13模具钢表面进行微造型加工。相同条件下,对比了连续加工方式与“单脉冲同点间隔多次”加工方式得到的凹坑二维形貌图,结果表明“单脉冲同点间隔多次”加工方式得到的凹坑形貌更好。研究了辅助气体种类对凹坑质量的影响,结果表明,氮气作为辅助气体时,加工表面的硬度增加的最大,凹坑质量也较好。影响微织构的激光工艺参数结果如下:泵浦电流主要影响凹坑直径、脉冲次数主要影响凹坑深度。重复频率和离焦量对凹坑几何形貌亦有影响,最佳加工重复频率范围为16 00Hz~2 000Hz、离焦量的最优值在0.5mm左右。试验设计和摩擦学方面,利用响应面法设计试验,用MWW-1A型万能摩擦磨损试验机模拟面面接触的摩擦试验,并用Design-Expert软件对实验数据进行了分析处理。结果表明,微凹坑确实可减小摩擦系数,微凹坑的几何参数中,直径对摩擦系数的影响最大,深度次之,密度最小;微凹坑几何参数间的交互作用对摩擦系数亦有影响,但影响程度不如各几何参数独立的影响大,直径与密度交互作用的影响最大,深度与密度交互作用的影响最小;在数据处理的过程中建立了微凹坑几何参数关于摩擦系数的数学模型,并验证了数学模型的准确性,其误差范围小于5%;最后在所建模型的基础上,对微凹坑几何参数进行了全面优化,得出了试验数据范围内的最佳凹坑参数组合:凹坑直径18 0μm、凹坑深度14μm、凹坑密度12%,该参数组合下的摩擦系数为0.083,与光滑试样相比,摩擦系数减小了近3倍。
[Abstract]:Friction is closely related to the reliability, working life and energy consumption of mechanical parts. The reasonable reduction of friction can make the mechanical parts in a good working environment, prolong the working life, improve the utilization rate of energy, and then reduce the economic loss. Since the appearance of Laser Surface Texturing (LS T) as a new method to improve the friction and wear properties of friction pairs, it has been favored by many scholars at home and abroad. How to design a reasonable micro-texture morphology and geometric size is the key to exert the antifriction property of texture. In this paper, the microtexture optimization and lubrication mechanism of H13 die steel surface are studied in combination with theory, experiment and simulation, in order to meet the best tribological performance of the die steel under the condition of this die steel. The main research results are as follows: in the aspect of theoretical research, the principle of improving lubrication state in micro-pits is analyzed. Based on the Reynolds equation, the lubrication model of surface texture of surface friction pairs is established, and the solution of the model is discussed. Then the lubrication model is numerically analyzed by using the FLUENT software of computational fluid dynamics (CFD). The effects of the diameter, depth and density of micropits on the pressure and pressure distribution of lubricating film are analyzed by single factor method. When the pit diameter is 120 渭 m, the optimum pit depth is 13 渭 m, the pit diameter is 100 渭 m and the depth is 10 渭 m, the optimum area share is 13%. In the aspect of process experiment, semiconductor pumped YAG laser was used to fabricate the surface of H13 die steel. Under the same conditions, the two-dimensional topography of the crater obtained by the continuous machining method and the "single pulse same point interval" machining method is compared. The results show that the crater morphology obtained by the "single pulse same point interval" machining mode is better than that obtained by the "single pulse same point interval" machining method. The effects of auxiliary gases on the quality of pits are studied. The results show that the hardness of the machined surface increases most and the quality of the pits is better when nitrogen is used as the auxiliary gas. The results of laser processing parameters affecting microtexture are as follows: pump current mainly affects pit diameter and pulse number mainly affects pit depth. The repetition rate and defocus amount also affect the geometry of the crater. The optimum machining repetition rate is 16 00Hz~2 000Hz, and the optimum defocus value is about 0.5mm. In the aspects of test design and tribology, the response surface method was used to simulate the friction test of surface contact with MWW- 1A universal friction and wear tester. The experimental data were analyzed and processed by Design-Expert software. The results show that the friction coefficient can be reduced by the micro-indentation. The diameter has the greatest influence on the friction coefficient, the depth is the second, and the density is the least among the geometric parameters of the pit. The friction coefficient is also affected by the interaction between geometric parameters of micro-pits, but the degree of influence is not as great as that of individual geometric parameters, the interaction between diameter and density is the largest, and the interaction between depth and density is the least. In the process of data processing, the mathematical model about friction coefficient of geometric parameters of micro-concave pit is established, and the accuracy of the mathematical model is verified. The error range is less than 5%. Finally, on the basis of the model, the geometric parameters of the micro pit are optimized, and the optimum combination of the pit parameters in the range of test data is obtained: pit diameter 180 渭 m, pit depth 14 渭 m, pit density 12%, the diameter of the pit is 180 渭 m, the depth of the pit is 14 渭 m, and the density of the pit is 12%. The friction coefficient under the combination of this parameter is 0.083, which is nearly three times lower than that of the smooth sample.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG178
本文编号：2460094
[Abstract]:Friction is closely related to the reliability, working life and energy consumption of mechanical parts. The reasonable reduction of friction can make the mechanical parts in a good working environment, prolong the working life, improve the utilization rate of energy, and then reduce the economic loss. Since the appearance of Laser Surface Texturing (LS T) as a new method to improve the friction and wear properties of friction pairs, it has been favored by many scholars at home and abroad. How to design a reasonable micro-texture morphology and geometric size is the key to exert the antifriction property of texture. In this paper, the microtexture optimization and lubrication mechanism of H13 die steel surface are studied in combination with theory, experiment and simulation, in order to meet the best tribological performance of the die steel under the condition of this die steel. The main research results are as follows: in the aspect of theoretical research, the principle of improving lubrication state in micro-pits is analyzed. Based on the Reynolds equation, the lubrication model of surface texture of surface friction pairs is established, and the solution of the model is discussed. Then the lubrication model is numerically analyzed by using the FLUENT software of computational fluid dynamics (CFD). The effects of the diameter, depth and density of micropits on the pressure and pressure distribution of lubricating film are analyzed by single factor method. When the pit diameter is 120 渭 m, the optimum pit depth is 13 渭 m, the pit diameter is 100 渭 m and the depth is 10 渭 m, the optimum area share is 13%. In the aspect of process experiment, semiconductor pumped YAG laser was used to fabricate the surface of H13 die steel. Under the same conditions, the two-dimensional topography of the crater obtained by the continuous machining method and the "single pulse same point interval" machining method is compared. The results show that the crater morphology obtained by the "single pulse same point interval" machining mode is better than that obtained by the "single pulse same point interval" machining method. The effects of auxiliary gases on the quality of pits are studied. The results show that the hardness of the machined surface increases most and the quality of the pits is better when nitrogen is used as the auxiliary gas. The results of laser processing parameters affecting microtexture are as follows: pump current mainly affects pit diameter and pulse number mainly affects pit depth. The repetition rate and defocus amount also affect the geometry of the crater. The optimum machining repetition rate is 16 00Hz~2 000Hz, and the optimum defocus value is about 0.5mm. In the aspects of test design and tribology, the response surface method was used to simulate the friction test of surface contact with MWW- 1A universal friction and wear tester. The experimental data were analyzed and processed by Design-Expert software. The results show that the friction coefficient can be reduced by the micro-indentation. The diameter has the greatest influence on the friction coefficient, the depth is the second, and the density is the least among the geometric parameters of the pit. The friction coefficient is also affected by the interaction between geometric parameters of micro-pits, but the degree of influence is not as great as that of individual geometric parameters, the interaction between diameter and density is the largest, and the interaction between depth and density is the least. In the process of data processing, the mathematical model about friction coefficient of geometric parameters of micro-concave pit is established, and the accuracy of the mathematical model is verified. The error range is less than 5%. Finally, on the basis of the model, the geometric parameters of the micro pit are optimized, and the optimum combination of the pit parameters in the range of test data is obtained: pit diameter 180 渭 m, pit depth 14 渭 m, pit density 12%, the diameter of the pit is 180 渭 m, the depth of the pit is 14 渭 m, and the density of the pit is 12%. The friction coefficient under the combination of this parameter is 0.083, which is nearly three times lower than that of the smooth sample.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG178
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