软固结磨粒群微观力学特性分析与试验研究
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摘要
针对软固结磨粒气压砂轮加工过程中磨粒群内部发生剪胀效应,造成磨粒群表面局部堆积,进而引起工件表面产生划痕、降低二次精加工效率和表面质量的问题,建立磨粒群内部微观接触力学模型,揭示磨粒群内部力链传递过程。采用Li-Dafalias弹塑性剪胀本构模型,来反映磨粒群内部微观力-位移的关系。通过颗粒流三维分析PFC3D软件数值模拟具有不同孔隙率的磨粒群力链网络演化过程,以及加工件表面压强分布,结果表明:当孔隙率超过44%后,磨粒群内部力链传递路径消失;工件表面压强呈周期分布,随着孔隙率增大,压强幅值减小。搭建试验平台,通过光整加工试验得到孔隙率和磨粒目数对工件表面粗糙度的影响规律,结果显示:当采用磨粒目数800、孔隙率24%时加工得到的工件表面粗糙度较小,表面粗糙度轮郭算术平均偏差从313. 74 nm降低到67. 11 nm.
A model of microscopic contact mechanics inside abrasives group is established to analyze the force chain transfer process. The Li-Dafalias elastoplastic dilatant constitutive model is used to reflect the relationship between micro-force and displacement within the abrasives group. The evolution of force chain network of abrasives group with different porosities and the pressure distribution on workpiece surface were simulated using the three-dimensional particle flow code( PFC3D) software. The simulated results show that,when the porosity exceeds 44%,the internal force chain transmission path of abrasives group disappears; the surface pressure of workpiece exhibits a periodic distribution,and the pressure amplitude decreases with the increase in porosity. A test platform was set up,and the influence laws of porosity and abrasive mesh on the surface roughness of workpiece can be concluded after a series of polishing experiments by pneumatic grinding wheels with softness consolidation abrasives. The experimental results show that the contour arithmetic mean deviation of workpiece surface roughness is small and decreases from 313. 744 nm to 67. 11 nm when the abrasive mesh is 800 and the porosity is 24%.
A model of microscopic contact mechanics inside abrasives group is established to analyze the force chain transfer process. The Li-Dafalias elastoplastic dilatant constitutive model is used to reflect the relationship between micro-force and displacement within the abrasives group. The evolution of force chain network of abrasives group with different porosities and the pressure distribution on workpiece surface were simulated using the three-dimensional particle flow code( PFC3D) software. The simulated results show that,when the porosity exceeds 44%,the internal force chain transmission path of abrasives group disappears; the surface pressure of workpiece exhibits a periodic distribution,and the pressure amplitude decreases with the increase in porosity. A test platform was set up,and the influence laws of porosity and abrasive mesh on the surface roughness of workpiece can be concluded after a series of polishing experiments by pneumatic grinding wheels with softness consolidation abrasives. The experimental results show that the contour arithmetic mean deviation of workpiece surface roughness is small and decreases from 313. 744 nm to 67. 11 nm when the abrasive mesh is 800 and the porosity is 24%.
引文
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[20] ISHIHARA K,TATSUOKA F,YASUADA S. Undrained deformation and liquefaction of sand under cyclic stress[J]. Soils and Foundations,2008,15(1):29-44.
[21] LI X S,DAFALIAS Y F. Dilatancy for cohesionless soils[J].Geotechnique,2000,50(4):449-460.
[22]沈珠江.理论土力学[M].北京:中国水利水电出版社,2000.SHEN Z J. Theoretical soil mechanics[M]. Beijing:China Water Conservancy and Hydropower Press,2000.(in Chinese)
[23]计时鸣,许亚敏,金明生,等.软固结磨粒气压砂轮的力学特性分析[J].中国机械工程,2012,23(19):2366-2372.JI S M,XU Y M,JIN M S,et al. Mechanical analysis of pressure grinding wheel with soft abrasive consolidation[J]. China Mechanical Engineering,2012,23(19):2366-2372.(in Chinese)
[2]王卓.光学材料加工亚表面损伤检测及控制关键技术研究[D].长沙:国防科学技术大学,2008.WANG Z. Research on key technologies of subsurface damage detection and control in optical materials processing[D]. Changsha:National University of Defense Technology,2008.(in Chinese)
[3]蔡立,田守信.光学元件加工技术[M].武汉:华中工学院出版社,1987.CAI L,TIAN S X. Optical component processing technology[M].Wuhan:Huazhong Institute of Technology Press,1987.(in Chinese)
[4] WALKER D D,BALDWIN A,EVANS R,et al. A quantitative comparison of three grolishing techniques for the precessions[J].Proceedings of SPIE,2007,6671:66711H-1-66711H-9.
[5]朱传睿.基于五轴混联气囊抛光机的气囊抛光工艺研究[D].哈尔滨:哈尔滨工业大学,2016.ZHU C R,Research on bonnet polishing process based on five axis hybrid machine[D]. Harbin:Harbin Institute of Technology,2016.(in Chinese)
[6] CHEUNG C F,KONG L B,HO L T,et al. Modelling and simulation of structure surface generation using computer controlled ultra-precision polishing[J]. Precision Engineering,2011,35(4):574-590.
[7] JAKOBSEN P D,LANGMAACK L,DAHL F,et al. Development of the soft ground abrasion tester(SGAT)to predict TBM tool wear,torque and thrust[J]. Tunnelling and Underground Space Technology,2013,38(9):398-408.
[8] SONG J F,YAO Y X,DONG Y G,et al. Prediction of surface quality considering the influence of the curvature radius for polishing of a free-form surface based on local shapes[J]. International Journal of Advanced Manufacturing Technology,2017,95(1):1-15.
[9] HUAI W B,TANG H,SHI Y Y,et al. Prediction of surface roughness ratio of polishing blade of abrasive cloth wheel and optimization of processing parameters[J]. International Journal of Advanced Manufacturing Technology,2016,90(1/2/3/4):1-10.
[10]曾晰,潘烨,计时鸣.芳纶浆粕纤维增强均质气压砂轮特性[J].复合材料学报,2017,34(10):2321-2329.ZENG X,PAN Y,JI S M. Characteristic of AFRP pneumatic wheel[J]. Acta Materiae Compositae Sinica,2017,34(10):2321-2329.(in Chinese)
[11]郑颖人,沈珠江,龚晓南.岩土塑性力学原理[M].北京:中国建筑工业出版社,2003.ZHEN Y R,SHEN Z J,GONG X N. Principle of rock mechanics[M]. Beijing:China Building Industry Press,2003.(in Chinese)
[12] CHRISTOFFERSEN J,MEHRABADI M M,NEMAT-NASSER S. A micromechanical description of granular material behavior[J]. Journal of Applied Mechanics,1981,48(2):339-344.
[13] KRUYT N P,ROTHENBURG L. Micromechanical definition of the strain tensor for granular materials[J]. Journal of Applied Mechanics,1996,63(3):706-711.
[14] BAGI K. Stress and strain in granular assemblies[J]. Mechanics of Materials,1996,22(3):165-177.
[15] LI X,YU H S,LI X S. Macro-micro relations in granular mechanics[J]. International Journal of Solids and Structures,2009,46(25/26):4331-4341.
[16] JOHNSON K L,KENDALL K,ROBERTS A D. Surface energy and the contact of elastic solids[J]. Proceedings of the Royal Society of London,1971,324(1558):301-313.
[17] THORNTON C. Interparticle sliding in the presence of adhesion[J]. Journal of Physics D:Applied Physics,1991,24(11):1942-1946.
[18]迟杰明,赵成刚,李小军.砂土剪胀机理的研究[J].土木工程学报,2009,42(3):99-104.CHI J M,ZHAO C G,LI X J. Study on the mechanism of sand dilatancy[J]. Journal of Civil Engineering,2009,42(3):99-104.(in Chinese)
[19]迟杰明,赵成刚,李小军.剪胀性砂土本构模型的研究[J].岩土力学,2008,29(11):2939-2944.CHI J M,ZHAO C G,LI X J. Study on constitutive model of dilatancy sand[J]. Rock and Soil Mechanics,2008,29(11):2939-2944.(in Chinese)
[20] ISHIHARA K,TATSUOKA F,YASUADA S. Undrained deformation and liquefaction of sand under cyclic stress[J]. Soils and Foundations,2008,15(1):29-44.
[21] LI X S,DAFALIAS Y F. Dilatancy for cohesionless soils[J].Geotechnique,2000,50(4):449-460.
[22]沈珠江.理论土力学[M].北京:中国水利水电出版社,2000.SHEN Z J. Theoretical soil mechanics[M]. Beijing:China Water Conservancy and Hydropower Press,2000.(in Chinese)
[23]计时鸣,许亚敏,金明生,等.软固结磨粒气压砂轮的力学特性分析[J].中国机械工程,2012,23(19):2366-2372.JI S M,XU Y M,JIN M S,et al. Mechanical analysis of pressure grinding wheel with soft abrasive consolidation[J]. China Mechanical Engineering,2012,23(19):2366-2372.(in Chinese)
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