人体腰椎模拟植入椎弓根螺钉的有限元分析

利用三维绘图软件构建人体腰椎L4-L5节段几何模型,并模拟植入椎弓根螺钉.通过UG与Ansys Workbench的无缝接口将所建模型导入后者,对模型赋值并进行有限元分析,得出在人体站立情况下腰椎的应力云图与位移云图.从云图中可看出正常腰椎模型的最大应力出现在L4下关节突附近,值为15.073 MPa;最大位移出现在椎间盘上表面前部,值为0.161 mm.植入椎弓根螺钉的腰椎模型最大应力出现在螺钉的中部,值为38.613 MPa;最大位移出现在第4腰椎上端的前部,值为0.136 mm.结果表明：植入的椎弓根螺钉可缓解椎体的承载负担,并且可使腰椎变形减小.该结论可为同类腰椎固定手术以及脊柱的生物力学分析提供理论参考.     

关于电磁场对单摆运动控制的研究

电磁控制单摆运动系统主要由控制模块、驱动模块、输入模块和显示模块四部分组成。控制模块采用STM32F103单片机作为核心元件,根据检测到的摆杆运动方向和位置判断出摆杆当前运动状态,采用PID算法控制驱动模块中的直流电磁铁,给摆杆输入相应动能,实现对摆杆摆动角度和摆动周期的综合控制。驱动模块主要利用L298N芯片实现对线圈电流的大小和方向的设定,进而产生相应大小的吸引力和斥力。同时该系统的输入和显示模块采用了彩色TFT触摸屏。利用触摸屏制作出的输入及显示界面,不但功能丰富、操作简便而且具有良好的视觉效果。     

基于稀疏强特征提取的三维地震数据完备方法

随着复杂储层地震资料特征筛选的机器学习技术的进步,如何有效地对参与地震属性优选和储层反演的地震样本进行采集和分析,成为目前智能地震预测领域的一个研究热点。目前的方法多着重于模型分类算法的改进,在标签的制作和采集方面不仅耗费大量时间进行人工标注,还存在标签不平衡情况下类内可靠性、类间平衡性不强等问题。为此,提出基于稀疏强特征提取的三维地震数据完备方法。首先,基于多数决原则的样本分割(Sample Segmentation Based on Majority Rule, SSMR)寻迹多尺度、多标签三维地震样本,进行采集、自动标注;然后,改进标签洗牌平衡方法(Improved Label Shuffling Balance Method, ILSB),通过“2+1”的样本增广平衡策略进行数据完备处理,改善样本采样不平衡性导致的模型训练偏向性;最后,利用基于最小L₁范数稀疏表示对奇异值分解结果进行强特征提取(Minimum L₁-norm Based Sparse Representation for Feature Extraction, L     

Wear mechanisms of PcBN tools when machining AISI 316L

This paper investigates the machinability of AISI 316L stainless steel without and with NMI treatment, when machined with three different PcBN tool grades: low cBN content (50% vol.), medium (65% vol.) and high (90% vol.). The NMI treatment consisted of resulfurized and Ca-treated steels with two different Si/Al ratio. The tool materials were evaluated in terms of tool life, showing the best performance for the medium cBN content grade. Results showed that the crater wear has a more significant effect on the tool performance than the standard wear criteria of maximum flank wear. The worn tools were examined using scanning electron microscopy (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM). In most cases, the crater exhibited three distinct regions from the edge to the end of the contact zone: the plateau, middle crater, and the upper region. Plateau and crater region displayed tool protective layer (TPL), consisting mostly of Al, Si, Mg and Ca-oxides; and some dimples in the tool from preferential wear of cBN grains. In the upper region of the best performing material, a ~1.5 μm thick TPL of mostly MnCr₂O₄ spinel was found, a result of the transfer of Mn- and Cr-rich oxide NMIs found in this material or oxidation of workpiece material, during the machining process.     

316L不锈钢激光快速成形过程中熔覆层的热裂机理

采用微观测试分析方法，针对316L不锈钢粉末，深入研究了激光快速成形过程中熔覆层的开裂行为及其形成机理，研究结果表明，316L不锈钢激光熔覆层裂纹多发生在树枝晶的晶界，呈现出典型的沿晶开裂特征，裂纹断面上有明显的氧化彩色，扫描电镜照片显示裂纹断面上树枝晶的方向与轮廓清晰可见，树枝晶晶界相当圆滑，表明裂纹是在高温下产生的，熔覆层中的裂纹是凝固裂纹，属于热裂纹范畴，裂纹产生的主要原因是熔覆层组织在凝固温度区间晶界处的残余液相受到熔覆层中的拉伸应力作用所导致的液膜分离的结果。     

Q235-304L电偶对在Na2S溶液中的电偶腐蚀行为研究

用电化学法和浸泡法研究了Q235-304L电偶对在3种不同浓度的Na2S溶液中的电偶腐蚀行为,用SEM观察试样的表面形貌.结果表明:在3种溶液中Q235钢的阳极过程均为混合控制,而304L的阴阳极过程均为电化学控制;偶接后Q235钢表面阳极金属的溶解过程与阴极过程同时进行,其阳极溶解电流大于电偶电流值;电偶腐蚀效应随阴阳极面积比的增大而增大;随着S2-浓度的升高,电偶对中Q235钢的腐蚀速率减小,电偶腐蚀效应也随之降低.     

纯铝累积叠轧焊高温力学性能与显微组织研究

室温条件下对退火态L2纯铝进行了6道次的累积叠轧焊试验,通过高温拉伸、透射电镜和扫描电镜实验,研究叠轧前后材料在高温拉伸过程中力学性能的变化、组织结构的演变以及拉伸后的断口形貌。结果表明,在高温拉伸过程中,叠轧后材料发生了动态回复,形成的亚晶组织随温度升高而长大;叠轧前后材料的抗拉强度随温度单调递减,延伸率则先升高,达到极值后降低;断口形貌显示,叠轧材料的高温断裂属于韧性断裂。     

电磁动态金属粉末注射成型型坯结构性能的研究

利用自行设计的电磁动态注射机DPII-90，对不锈钢金属粉末316L和粘结剂的混合喂料进行稳态和动态注塑成型实验，研究振动参数对金属粉末和粘结剂混合喂料的均匀化和密实机理的影响。实验结果表明，各动态成型条件下的型坯密度明显大于稳态成型条件下的密度。当振动频率（或振幅）不变时，随着振幅（频率）的增大，型坯密度呈非线性增大，达到最大值后缓慢下降，存在一个最佳值。在频率7Hz-10Hz，振幅50μm～150μm的范围内，注射出的型坯密度较高，密实性好。电镜扫描（SEM）发现，金属粉末与粘结剂的分散均匀和完善程度的变化规律和型坯密度随着振幅（频率）的变化规律基本一致。     

L12型Al3Ti合金室温变形超位错的分解及计算机图像模拟

利用透射电子显微镜和计算机图像模拟技术研究了ＬＩ２型Ａｌ３Ｔｉ合金室温变形的位错核心结构，结果表明：α（１１０）超位错在｛１１１｝面上分解成两个α／３｛１１２｝型超偏位错，其间为超点阵内禀层错。     

Comparative study in chemistry of microbially and electrochemically induced pitting of 316L stainless steel

Ennoblement of stainless steel (SS) by microbially deposited manganese oxides can lead to pitting corrosion at low chloride concentrations, causing unexpected material failures. We exposed 316L SS to manganese oxidizing bacteria Leptothrix discophora under well-defined laboratory conditions, and then placed the ennobled coupons in a 0.5 M sodium chloride solution until pitting developed. Using time-of-flight secondary ion mass spectroscopy we demonstrated that the pits and their immediate vicinity associated with microbial influenced corrosion had different chemical signatures than those associated with electrochemically induced pitting, suggesting a possibility that the microorganisms were directly involved in pit initiation. Based on the differences in the chemical signatures we were able to distinguish the microbially induced pits from those induced by anodic polarization.