【摘要】：選擇性激光燒結(Selective Laser Sintering,SLS)是增材制造技術的一個重要分支,通過逐層鋪粉、逐層掃描燒結的方式來直接制造零件。鋪粉作為SLS的中間工序,對燒結成形后成型件的質(zhì)量有著至關重要的影響。鋪出均勻、無缺陷且具有高密度的粉末層是進行良好燒結的前提條件之一,即粉體的流動性越好,粉體的鋪展性能也就越好,后續(xù)的燒結質(zhì)量也就越好。因此,開展粉體流動性影響因素的研究對粉體鋪展性能、燒結質(zhì)量有著至關重要的影響。本文以SLS的原料——尼龍粉末為研究對象,采用實驗和數(shù)值仿真相結合的方法來研究尼龍粉末及碳纖維/尼龍復合粉末的流動性,探索環(huán)境溫度、粉體自身物性參數(shù)以及添加劑等對粉末流動性的影響規(guī)律。具體內(nèi)容包括以下幾個方面:(1)通過超景深顯微鏡和激光粒度分析儀觀測尼龍粉末的微觀形貌與粒徑分布,采用粉體綜合測試儀和直剪儀測定表征尼龍粉末流動性的各項物理指標。實驗研究并分析了粉末樣本容量、粉末溫度及添加劑對尼龍粉末流動性的影響。同時,通過實驗研究了碳纖維含量、溫度等對碳纖維/尼龍復合粉末流動性的影響規(guī)律。(2)在離散元軟件PFC5.0中建立了粉體顆粒模型,選取滾動阻尼模型作為尼龍粉末顆粒間以及碳纖維/尼龍復合粉末顆粒間的接觸模型,并在此接觸模型的基礎上,通過編寫FISH函數(shù)加入范德華力。建立了尼龍粉末及復合粉末的休止角模型與直剪試驗模型,并通過數(shù)值仿真與實驗結果對比,校準了前述接觸模型的各個微觀參數(shù)。(3)通過離散元仿真分析了粒徑、粒徑分布、溫度對尼龍粉末流動性的影響規(guī)律。仿真結果表明:單粒徑分布與均勻分布的顆粒大小對尼龍粉末的流動性都有一定的影響,而呈高斯分布的尼龍顆粒大小對流動性的影響規(guī)律不明顯。同時,對不同溫度下的尼龍粉末的休止角進行仿真與實驗對比,其結果吻合較好,從而進一步驗證了選取的接觸模型的可行性及接觸參數(shù)的合理性。(4)根據(jù)對SLS鋪粉時粉體所受的應力狀態(tài)進行分析,設計并制作了與鋪粉時具備相似應力狀態(tài)的滾筒實驗臺,并通過實驗研究分析了環(huán)境溫度、滾筒轉速及粉體填充率對尼龍粉末流動性的影響。結果表明,粉體填充率、環(huán)境溫度以及滾筒轉速過高都會不同程度地導致粉體流動性變?nèi)酢?br/>[Abstract]:Selective laser sintering (Selective Laser Sintering,SLS) is an important branch of material augmentation technology. It can be directly manufactured by layer powder and layer by layer scanning sintering. As an intermediate process of SLS, powder laying plays an important role in the quality of sintered forming parts. The uniform, non-defective and high-density powder layer is one of the prerequisites for good sintering, that is, the better the fluidity of the powder, the better the spreading performance of the powder, and the better the subsequent sintering quality. Therefore, it is very important to study the influencing factors of powder fluidity on the properties of powder spreading and sintering quality. In this paper, the flow of nylon powder and carbon fiber / nylon composite powder were studied by using the method of experiment and numerical simulation, and the ambient temperature was explored, taking the raw material of SLS, nylon powder, as the research object, and the method of numerical simulation was used to study the fluidity of nylon powder and carbon fiber / nylon composite powder. The effect of physical parameters and additives on the fluidity of powder. The main contents are as follows: (1) the microstructure and particle size distribution of nylon powder were observed by means of hyperfield microscope and laser particle size analyzer. The physical indexes of nylon powder fluidity were measured by powder comprehensive testing instrument and direct shearing instrument. The effects of powder sample size, powder temperature and additives on the fluidity of nylon powder were studied and analyzed experimentally. At the same time, the effects of carbon fiber content and temperature on the fluidity of carbon fiber / nylon composite powder were studied experimentally. (2) the powder particle model was established in discrete element software PFC5.0. The rolling damping model is selected as the contact model between nylon powder particles and carbon fiber / nylon composite powder particles. On the basis of the contact model, the van der Waals force is added by writing the FISH function. The angle of repose model and the direct shear test model of nylon powder and composite powder were established, and the microscopic parameters of the contact model were calibrated by comparing the numerical simulation with the experimental results. (3) the particle size and particle size distribution were analyzed by discrete element simulation. The effect of temperature on the fluidity of nylon powder. The simulation results show that the particle size of single particle size distribution and uniform distribution have some influence on the flowability of nylon powder, while the size of nylon particle distributed by Gao Si has no obvious effect on the flow rate of nylon powder. At the same time, the simulation and experimental comparison of the angle of repose of nylon powder at different temperatures show that the results are in good agreement with each other. The feasibility of the selected contact model and the reasonableness of the contact parameters are further verified. (4) according to the analysis of the stress state of the powder when the powder is laid by SLS, a roller test bench with similar stress state to the powder laying is designed and made. The effects of ambient temperature, drum speed and powder filling ratio on the fluidity of nylon powder were studied. The results show that the fluidity of the powder is weakened to some extent due to the powder filling ratio, ambient temperature and the rotating speed of the roller.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB332

【參考文獻】

相關期刊論文 前10條

1 譚援強;鄭軍輝;張浩;高偉;姜勝強;肖湘武;;基于離散元法的錐形筒倉中顆粒流體的數(shù)學模擬[J];過程工程學報;2015年06期

2 郭曉鐳;陸海峰;龔欣;;粉體流變儀動態(tài)表征煤粉的流動性[J];中國粉體工業(yè);2015年06期

3 史玉升;閆春澤;魏青松;文世峰;朱偉;;選擇性激光燒結3D打印用高分子復合材料[J];中國科學:信息科學;2015年02期

4 賈富國;韓燕龍;劉揚;曹銀平;史宇菲;姚麗娜;王會;;稻谷顆粒物料堆積角模擬預測方法[J];農(nóng)業(yè)工程學報;2014年11期

5 姜勝強;譚援強;張高峰;彭銳濤;;基于離散元法預測碳化硅陶瓷的高溫力學性能[J];機械工程材料;2014年01期

6 祁萌;李曉紅;胡曉睿;茍桂枝;黃秋實;王召陽;;增材制造技術在國外國防領域的發(fā)展現(xiàn)狀與趨勢[J];國防制造技術;2013年05期

7 杜焰;趙立杰;熊耀坤;李曉海;王松濤;馮怡;徐德生;;藥用粉體流動性的多元分析方法表征[J];藥學學報;2012年09期

8 ;Flow properties of three fuel powders[J];Particuology;2012年04期

9 漆海峰;郭曉鐳;陸海峰;吳福玉;龔欣;;煤粉的流動性測試及評價方法[J];化工學報;2012年02期

10 郭偉;郭曉鐳;吳躍;黃斌;龔欣;;煤粉流動性對GSP氣化爐氣力輸送的影響研究[J];煤化工;2011年05期

相關會議論文 前2條

1 閆春澤;史玉升;魏青松;徐林;張升;;碳纖維/尼龍復合粉末選擇性激光燒結工藝參數(shù)研究[A];第13屆全國特種加工學術會議論文集[C];2009年

2 王泳嘉;;離散單元法——一種適用于節(jié)理巖石力學分析的數(shù)值方法[A];第一屆全國巖石力學數(shù)值計算及模型試驗討論會論文集[C];1986年

相關碩士學位論文 前4條

1 鄭軍輝;尼龍粉末選擇性激光燒結鋪粉工藝數(shù)值模擬研究[D];湘潭大學;2016年

2 吳福玉;粉體流動特性及其表征方法研究[D];華東理工大學;2014年

3 徐林;碳纖維/尼龍12復合粉末的制備與選擇性激光燒結成形[D];華中科技大學;2009年

4 陳淑花;粉體流動的塑粘性模型及對粉體在管道中流動速度分布的模擬[D];大連理工大學;2001年

，

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