选择性激光烧结SLS的研究
选择性激光烧结SLS的研究 研究生论文 加入时间:2011-01-11 管理员 点击: 评论数: |

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摘要 选择性激光烧结SLS(Selective Laser Sintering)是一种基于离散材料堆积成型并能 进行先进产品研究与开发的新型激光快速成型技术。它集激光、新材料、数控加工、计 算机辅助设计和精密伺服驱动等最新技术于一体,摆脱传统的机械切、削、刨、磨等使 材料递减的方式,使用最短的时间更新产品的型号,制造出优良的塑料件、陶瓷件或金 属件。在选择性激光烧结快速成型系统中,是直接采用激光热源来烧结粉末材料成型零 部件的,故烧结过程的温度场分布直接影响烧结成型机制,进而影响烧结质量。因此, 对各种粉末材料在选择性激光烧结过程中温度场分布规律的确定,是合理选择烧结工艺 参数的基础。但是,选择性激光烧结过程中的瞬时烧结温度变化极快,同时又受到诸多 因素的影响,尤其受材料热物性和烧结参数的影响很大,如果瞬态烧结温度过高,引起 材料的碳化;如果瞬态烧结温度过低,会使成型后的工件力学性能达不到设计要求,由 于瞬态烧结温度情况较为复杂,所以很难直接用实验方法测定温度的分布。目前,在这 方面的研究大多是通过对烧结成型后试件的材料力学性能的分析,再间接的调节烧结工 艺参数,控制粉末的烧结温度来完成的,该方法生产时间长,加工效率低,分析不直观, 判断不准确;如果采用接触式测温的方法,这显然也有着诸多弊端存在。所以,瞬态温 度场的实时检测成为选择性激光烧结加工进程中急需解决的问题。 本文首先建立了二维非线性热传导数值传热模型,对选择性激光烧结瞬态温度场进 行了数值模拟,同时提出了基于红外测温原理实现瞬态烧结温度场实时检测的非接触测 温方法。根据红外辐射测温理论和被测对象的具体参数,选取相应的红外探测器,利用 红外热成像测试系统,实现了对扫描激光瞬态烧结点的实时跟踪。通过对采集热像图的 数字化处理,分析了三种不同材料下的瞬态温度随烧结参数的变化趋势。通过实验结果 和数值模拟的对比,分析了数值模拟与实测结果的异同。重点对瞬态烧结温度的测试方 法及温度随烧结参数的变化规律进行了分析,结果表明该测试方法较好的实现了瞬态温 度场的实时检测,为合理的选择烧结工艺参数提供了坚实的基础,对于选择性激光烧结 技术的完善及发展有积极的推动作用。 关键字: 选择性激光烧结,瞬态温度场,数值模拟,红外热成像,误差分析 南昌航空工业学院硕士学位论文 第IV 页 ABSTRACT Selective laser sintering (SLS) is a new laser rapid protyping technology, which is based on discrete powder deposited It syncretizes lots of new technologies such as laser, new materials, numerical control manufacture, computer aided design (CAD) and precision servo etc to research and develop novel productions Because the traditional mechanical chipping, chopping, digging and grinding are cast away, the finer plastic, potter or metal pieces are made using the SLS technic in shortest time to update model In the course of SLS protyping, laser heat resource has effect on sintering powder directly, so sintering temperature field influence immediately protyping quality Consequently the protyping temperature rules of all kinds materials are the base of selecting sinter technique parameter But the sintering temperature is transient,at the same time many factors affected it, especially materials thermal physical and sintering parameters If transient sintering temperature is too high, the materials is burned into charcoal; if too low, the mechanics capability of piece dose not agree with request of design As a result of complexity of transient sintering temperature, at present the monitor is absent, temperature parameter is adjusted after it is sintered according the mechanics capability, the way is not intuitionistic, efficient and accurate, error is obvious, if contact measurement is used So examining transient sintering temperature real-time is imperative problem of SLS In this paper, 2D non-line thermal conduction numerical model is set up at first, SLS transient temperature field is simulated;non-contact measurement method is proposed, which is based on infrared temperature testing According to infrared thermometer theory and parameter of object, the infrared detector is selective, infrared thermograph is utilized to make the transient temperature of selective laser sintering detected continuously reality The change trend of three kinds materials transient temperature is analyzed through collected and digital thermography The numerical simulation and measurement result is contrasted to explain the difference each other Mostly, the measure system and the rule of transient temperature with processing parameter are emphasized, the result indicates that the proposed test system can preferably realize the real-time monitor It provides steady base for selecting sinter parameter reasonable, meanwhile make SLS perfectly and accelerate SLS actively development Key words: selective laser sintering, transient temperature, numerical simulation, infrared thermograph, error analysis 目录 目 录I 摘 要 III 第一章 绪论 1 §11 选择性激光烧结成型原理 1 §12 研究的背景及目的 2 §13 SLS 成型温度场的研究进展 2 §14 SLS 成型温度场研究的发展趋势 6 §15 本文的主要研究内容 6 第二章 SLS 成型温度场的数值模拟 8 §21 引言 8 §22 SLS 成型温度场数学模型的建立 8 §23 SLS 成型温度的数值计算原理 11 §24 ANSYS 有限元分析软件的应用12 §25 不同烧结参数下的数值模拟结果14 §26 小结15 第三章 SLS 瞬态成型温度场的测试 16 §31 引言16 §32 SLS 瞬态成型温度场测试方法分析16 §33 SLS 瞬态成型温度场的测试23 §34 小结26 第四章 数据处理与分析 27 §41 引言27 §42 点温的数据处理27 §43 线温的数据处理33 §44 实际测试与数值模拟比较分析39 §45 采集时间间隔对点温测试的影响40 §46 小结41 第五章 误差分析 42 §51 引言42 §52 测温计算42 §53 热像仪测温误差计算分析44 §54 SLS 过程测温误差影响因素分析45 §55 小结47 第六章 结论与展望 48 §61 全文总结48 §62 研究展望49 南昌航空工业学院硕士学位论文 第II 页 致 谢 50 参考文献 51 硕士期间发表的论文 54 南昌航空工业学院硕士学位论文 第III 页 参考文献 [1] YH Chen, CT Ng Integrated reverse engineering and rapid prototyping[J] Computers ind 1997,33:481~484 [2] 胥橙庭,沈以赴,顾冬冬等 选择性激光烧结成型温度场的研究进展[J] 铸 造2004,53(7):511~514 [3] John D Williams, Carl R Deckard Advances in modelling the effects of selected parameters on the SLS process [J] Rapid Prototyping Journal 1998,4(2):90~100 [4] Simchi A, Pohl H Effects of laser sintering processing parameters on the microstructure and densification of iron powder[J] Materials and Engineering A 2003,359:119~128 [5] 罗 宁 , 吕 志刚, 崔旭龙等 快速成型及快速制造技术[J] 铸造技 术2003,24(2):118~119 [6] K Maeda, THC Childs Laser sintering(SLS) of hard metal powders for abrasion resistant coatings[J] Journal of Materials Processing Technology2004,149:609~615 [7] 杨世洲,周小俊 用于铸造金属功能件的快速原型模样的特点分析[J] 铸造技 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