【摘要】：摩擦與機械零件的可靠性、工作壽命以及能耗密切相關。合理的減小摩擦可使機械零件處于良好的工作環(huán)境,延長工作壽命,提高能量利用率,進而減小經(jīng)濟損失。自從表面微織構技術Laser Surface Texturing(LS T)作為一種新的改善摩擦副表面摩擦磨損性能的新方法問世后,便迅速受到國內外眾多學者的青睞。如何設計出合理的微織構形貌和幾何尺寸是發(fā)揮織構減摩性能的關鍵。本文結合理論、實驗和模擬,對H13模具鋼表面進行微織構優(yōu)化和潤滑機理研究,以滿足該模具鋼工況下的最佳摩擦學性能。主要研究成果如下:理論研究方面,分析了微凹坑改善潤滑狀態(tài)的原理,基于Reynolds方程建立了面面摩擦副表面織構的潤滑模型,并探討了模型的求解方法。然后采用計算流體動力學(CFD)中的FLUENT軟件對潤滑模型進行了數(shù)值分析,采用單因素法分析了微凹坑直徑、深度、密度對潤滑油膜的壓力和壓力分布的影響,結果表明,當凹坑直徑為120μm時,具有最佳流體動壓潤滑效果的凹坑深度為13μm,凹坑直徑100μm、深度10μm時,最佳面積占有率為13%。工藝實驗方面,采用半導體泵浦YAG激光器在H13模具鋼表面進行微造型加工。相同條件下,對比了連續(xù)加工方式與“單脈沖同點間隔多次”加工方式得到的凹坑二維形貌圖,結果表明“單脈沖同點間隔多次”加工方式得到的凹坑形貌更好。研究了輔助氣體種類對凹坑質量的影響,結果表明,氮氣作為輔助氣體時,加工表面的硬度增加的最大,凹坑質量也較好。影響微織構的激光工藝參數(shù)結果如下:泵浦電流主要影響凹坑直徑、脈沖次數(shù)主要影響凹坑深度。重復頻率和離焦量對凹坑幾何形貌亦有影響,最佳加工重復頻率范圍為16 00Hz~2 000Hz、離焦量的最優(yōu)值在0.5mm左右。試驗設計和摩擦學方面,利用響應面法設計試驗,用MWW-1A型萬能摩擦磨損試驗機模擬面面接觸的摩擦試驗,并用Design-Expert軟件對實驗數(shù)據(jù)進行了分析處理。結果表明,微凹坑確實可減小摩擦系數(shù),微凹坑的幾何參數(shù)中,直徑對摩擦系數(shù)的影響最大,深度次之,密度最小;微凹坑幾何參數(shù)間的交互作用對摩擦系數(shù)亦有影響,但影響程度不如各幾何參數(shù)獨立的影響大,直徑與密度交互作用的影響最大,深度與密度交互作用的影響最小;在數(shù)據(jù)處理的過程中建立了微凹坑幾何參數(shù)關于摩擦系數(shù)的數(shù)學模型,并驗證了數(shù)學模型的準確性,其誤差范圍小于5%;最后在所建模型的基礎上,對微凹坑幾何參數(shù)進行了全面優(yōu)化,得出了試驗數(shù)據(jù)范圍內的最佳凹坑參數(shù)組合:凹坑直徑18 0μm、凹坑深度14μm、凹坑密度12%,該參數(shù)組合下的摩擦系數(shù)為0.083,與光滑試樣相比,摩擦系數(shù)減小了近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.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG178

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本文編號：2460094