本文關(guān)鍵詞：分形結(jié)構(gòu)顆粒團(tuán)聚體分散行為的三維離散元法數(shù)值模擬研究　出處：《華南理工大學(xué)》2016年碩士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 顆粒團(tuán)聚體 凝聚機(jī)制 分形結(jié)構(gòu) 分散行為 離散元法

【摘要】：納米尺度填充顆粒在聚合物基體中的分散效果直接影響了聚合物基納米復(fù)合材料的綜合性能,由于納米顆粒表面能極高,并且在范德華力和靜電力的作用下極易團(tuán)聚形成顆粒團(tuán)聚體。因此,提高填充納米顆粒在聚合物基體中的分散均勻性對(duì)于聚合物加工領(lǐng)域來(lái)說(shuō)是一項(xiàng)十分重要的課題。目前,實(shí)驗(yàn)手段難以精確測(cè)得納米顆粒在加工過(guò)程中的位移、速度和接觸力等動(dòng)態(tài)信息,并且難以評(píng)估團(tuán)聚體結(jié)構(gòu)對(duì)顆粒分散效果的影響。隨著離散元法(Discrete Element Method,DEM)發(fā)展和逐漸成熟,許多學(xué)者開(kāi)始利用離散元法對(duì)團(tuán)聚體的分散過(guò)程展開(kāi)研究。但是以往所研究的團(tuán)聚體通常為簡(jiǎn)單結(jié)構(gòu)或是致密結(jié)構(gòu),與通過(guò)隨機(jī)運(yùn)動(dòng)凝聚形成的團(tuán)聚體的結(jié)構(gòu)存在一定差別,因此所得結(jié)果還不能夠完全反映出團(tuán)聚體的分散特征,同時(shí),未深入揭示團(tuán)聚體的分散機(jī)理,即顆粒究竟以何種分散方式脫離團(tuán)聚體沒(méi)有提出明確的判斷標(biāo)準(zhǔn)。隨著分形凝聚計(jì)算機(jī)模擬技術(shù)的發(fā)展完善,采用顆粒分形凝聚模型能夠生成與真實(shí)顆粒團(tuán)聚體結(jié)構(gòu)十分相似的分形結(jié)構(gòu)團(tuán)聚體,因此,對(duì)具有分形結(jié)構(gòu)的團(tuán)聚體在流場(chǎng)中的分散行為進(jìn)行研究,將有助于揭示團(tuán)聚體在真實(shí)加工流場(chǎng)中的分散機(jī)理。將顆粒分形凝聚計(jì)算機(jī)模擬技術(shù)和離散元法數(shù)值模擬技術(shù)相結(jié)合,在Visual Studio2010編程環(huán)境中,采用C++編程語(yǔ)言開(kāi)發(fā)顆粒凝聚與分散模擬軟件(Particles Aggregate and Disperse,PAD),利用OpenGL實(shí)現(xiàn)顆粒運(yùn)動(dòng)行為的可視化。利用PAD軟件模擬了分形結(jié)構(gòu)團(tuán)聚體凝聚過(guò)程,研究了分形結(jié)構(gòu)團(tuán)聚體在流場(chǎng)中的分散行為及其力鏈結(jié)構(gòu)演變規(guī)律。結(jié)果表明,相同凝聚體系條件下,團(tuán)聚體的分形維數(shù)隨著顆粒數(shù)量的增多而提高;擴(kuò)散指數(shù)的取值直接影響DLCA團(tuán)聚體的凝聚機(jī)制;強(qiáng)弱力鏈交織形成了團(tuán)聚體復(fù)雜的力鏈網(wǎng)絡(luò)形態(tài),分散過(guò)程中,團(tuán)聚體力鏈結(jié)構(gòu)的變化決定了顆粒的分散機(jī)制;DLCA團(tuán)聚體最終的碎片加權(quán)顆粒數(shù)隨著流場(chǎng)強(qiáng)度的增大以?xún)绾瘮?shù)規(guī)律降低;相同流場(chǎng)強(qiáng)度下,拉伸流場(chǎng)對(duì)DLCA團(tuán)聚體的分散效果優(yōu)于剪切流場(chǎng)。
[Abstract]:The nano scale dispersion effect of particles in the polymer matrix directly affects the performance of polymer nanocomposites, because nano particle surface energy is extremely high, and extremely easy in the van Edward force and electrostatic force under the effect of agglomeration of particles. Therefore, improving the filling nano particles in polymer matrix, the dispersion uniformity is a very important task for the polymer processing field. At present, it is difficult to accurately measure the displacement experiments of nano particles in the machining process, the speed and force of dynamic information, and it is difficult to assess the impact of aggregate structure on dispersing of particles. With the discrete element method (Discrete Element Method, DEM) development and gradually mature and many scholars have started research on the discrete element method of dispersion on aggregate. But previous studies usually aggregate simple structure or Compact structure, and there are some differences of structure formation of aggregates by the random motion of cohesion, so the results can not fully reflect the characteristics of dispersion, polymer group at the same time, did not reveal the dispersion mechanism of aggregates, namely the particle dispersion from the aggregates with what made no clear criteria. With the development of computer simulation of fractal aggregation the improvement of technology, adopting the particle fractal aggregation model to fractal structure formation and the real particle aggregates, aggregate structure is very similar to the result, to study the dispersion behavior of aggregates with fractal structure in the flow, will help to reveal the aggregates in the real processing flow field the dispersion mechanism of the particles. The computer simulation technology and discrete fractal aggregation finite element method combining numerical simulation technology in Visual Studio2010 programming environment, using C++ programming language development Particle agglomeration and dispersion simulation software (Particles Aggregate and Disperse, PAD), visualization of particle movement is simulated by OpenGL. The fractal structure of aggregates condensation process by using PAD software, the dispersion behavior and force chain structure evolution of the fractal structure of aggregates in the flow field. The results show that the same system under the condition of fractal dimension the aggregates increase with the number of particles; value of diffusion index directly affects the coagulation mechanism of DLCA aggregates; force chain intertwined to form the force chain network form aggregates complex, the process of dispersion, agglomeration changes in physical chain structure determines the mechanism of particle dispersion; DLCA aggregates the final weighted number of particles increases with debris flow intensity of power-law flow is reduced; the same strength, tensile flow of DLCA aggregates dispersed better than shear flow Field.

【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TB383.1

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本文編號(hào)：1376164