激光快速成形正多边形格子扫描路径的生成算法

针对激光快速成形技术,提出并实现一种正多边形格子扫描路径的生成算法。首先根据STL模型数据获得每层切片信息和切片包围盒,并在包围盒内部均匀布置一组正多边形格子,然后通过多边形求交运算格子化离散切片,再针对每一离散格子区域求解内部扫描路径,最后按照一定加载策略排列格子区域内部路径。试验表明,该算法具有线性阶时间复杂度,且稳定可靠高效。     

曲面边缘均匀喷涂的路径分片规划方法

针对现有的切片法生成的喷涂路径在曲面边缘处喷涂不均匀的问题,提出一种基于点云模型的曲面边缘均匀喷涂的路径分片规划方法.该方法基于曲面点云模型,首先利用主成分分析法构建曲面外扩包围盒,基于外扩包围盒生成的主切片将曲面分片为一系列单条曲面,使得每一个单条曲面都对应于一条喷涂路径,再利用副切片将单条曲面分片为一系列单片曲面,...     

基于点云的汽车喷涂路径规划

针对切片法生成的喷涂路径在边缘处喷涂不均匀，且对汽车复杂曲面规划时存在喷涂路径间隔不均匀等问题，提出一种基于复杂点云的改进投影法的路径规划方法。首先，利用改造后的FCM算法将点云分割成较简单的点云集；其次，通过平均法矢量和边界连接方式构建有向包围盒，基于包围盒生成点云切片，再对各切片采用加权投影法生成路径节点；最后，通过蚁群算法生成连续完整路径。仿真结果表明，在期望喷涂厚度为45μm的情况下对汽车前杠和后盖进行路径规划，前盖采用切片法的厚度误差为16.4μm,采用本算法的厚度误差为4.12μm,误差减小了74.8%,后杠采用切片法的厚度误差为27.12μm,采用本算法的厚度误差为4.86μm,误差减小了82%。实验结果证明该方法能有效规划出完整喷涂路径，在喷涂均匀性相对切片法有明显提升。     

三维物体的准最小包围盒快速求解方法

针对现有求解精确三维物体最小包围盒算法的时间复杂度过高这一问题,提出一种基于物体表面采样点集的准最小包围盒快速求解方法。该方法首先提出一种增量式聚类简化算法对物体表面采样点集的非特征区域进行大幅简化,并将简化后点集的精确最小包围盒作为求解原始采样点集准最小包围盒的定位空间,以该空间下的最小轴向包围盒作为原始三维物体的准最小包围盒。试验结果表明,在满足求解精度要求的前提下,该方法与采样点集的精确最小包围盒求解方法相比,其计算效率提高90%左右,与基于遗传算法的求解方法相比,其计算效率最大可提高30%。     

机器人电弧熔丝增材制造扫描路径生成算法研究

针对快速成型中目前已有层片扫描路径生成算法的不足,在轮廓偏置扫描路径填充算法和分区扫描路径填充算法的基础上提出一种改良的基于偏置轮廓特征的分区扫描路径填充算法。首先判断层片轮廓环的内外性质,以此为依据获取边界处的偏置轨迹,并按分区扫描的方式得到偏置轮廓环内部待填充区域的轨迹,最终的成形路径中起停点明显减少且其中大多数扫描起点和终点位于制件内部。实验结果表明,在机器人电弧熔丝增材制造中,采用该算法的混合扫描方式可以有效改善成形质量,并在一定程度上提高成形效率。     

基于八叉树和方向包围盒的自由曲面加工干涉检查的简化算法

基于分层方向包围盒（OBB）和八叉树空问剖分法，采用分离轴理论，利用离散刀位点间的关联性。针对自由曲面五轴加工的全局干涉问题，给出了一种刀具干涉初步检测的简化算法。应用八叉树的分层结构，只有节点发生干涉，才需要对子节点进行进一步处理。由于刀具路径离散位置的连续性，采用设置缓冲区法来减少需要处理的节点数，从而有效降低了算法的复杂性。     

基于数控机床特性的碰撞检测算法研究

针对五轴数控加工过程中的碰撞检测问题,提出基于倾斜度包围盒分类选择法,传统的包围盒选择只是选择单一或者两种的包围盒,不能根据机床部件的特性针对性的构建包围盒。文章根据加工过程中各轴的运动状态实时的选择构建紧凑的包围盒,并通过紧密率来验证包围盒是否满足要求。在精确检测阶段,为避免分离轴定理的盲目性,提出选择包围盒的最近平面,通过包围盒与最近平面的位置关系来判断两模型是否相交,以提高检测效率。通过实例表明:相比于无包围盒碰撞检测本算法效率提升160%,与均采用OBB包围盒层次树来进行碰撞检测本算法检测效率提升40%,验证了算法的可行性。     

基于复合路径的连续纤维熔丝挤出成形轨迹优化研究

轨迹规划技术在复合材料熔丝挤出成形中非常关键,合理的轨迹可以提高增材制造成形零件的表面质量和强度。针对复合材料熔丝挤出成形的特点,结合多种路径规划算法,提出一种复合路径填充算法。引入NURBS曲线生成轮廓偏置路径,以保持切片轮廓的精度;在切片层的内部区域生成Zigzag填充路径,并在路径转折处进行圆弧优化,减少了约85%空行程,提高了成形效率;然后,基于生成的路径构建时间分析数学模型,以提前对整个制造过程所需的总体时间进行预估及分析,达到对制造过程的前馈控制;最后,使用复合路径填充算法对典型结构体进行模拟制造,相较传统算法减少了28.3%~36.2%制造时间,提高了制造效率。     

基于改进粒子群算法的线缆路径规划方法研究

针对复杂机电产品布线路径规划过程中存在的效率较低、可应用性差等问题,提出一种改进粒子群算法,使用栅格法对布线空间进行划分,对障碍物建模并进行方向包围盒处理。为了避免算法在迭代过程中陷入局部最优,引入非线性逐渐递减的惯性权重与异步变化的学习因子,并且将贴壁约束加入到路径规划的过程中,保证线缆在敷设时路径的合理性。最后在仿真试验中,与标准粒子群算法进行对比,验证了改进后算法的合理性与可行性。     

基于DirectX SDK 开发平台的虚拟装配碰撞检测

针对各企业采用的软件类型差异,提出了基于DirectX SDK的远程协同设计模型,用X文件作为虚拟装配统一的数据交换格式.根据X文件对三维模型数据的存储方式并结合AABB包围盒的检测算法原理,建立了以轴向投影节点为单元的包围盒二叉排序树,用中序遍历的方法,产生轴向检测表,提高了检测速度.在精确判断过程中,提出了以坐标系变换的方式,把三角形的空间求交问题简化为平面问题,简化了算法并提高了检测速度.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.