低电导率工质中气泡的极化运动实验研究

为探讨电场作用下气泡在低电导率工质中的极化运动特性,采用高速数码摄像技术对气泡在正庚烷溶液中的生长和分散过程进行了可视化研究,并结合无量纲数分析了不同气体流量和施加电压下的气泡演变特征以及极化力主导的气泡运动规律。结果表明,增大电场强度可导致气泡生长周期缩短,气泡尺寸显著减小,产生频率加快。在低电场强度下,气泡运动主要表现为流体动力学特性;而在强电场作用下,气泡首先受极化力主导而表现为电流体动力学特性,其直线轨迹高度随Bo_E增大而增大。但随着电场强度在竖直方向上的衰减以及液相阻力影响,气泡运动速度不断减小;当气泡脱离极化力主导区域后,其运动再次表现为流体动力学特性,受尾迹诱导和气泡间相互作用影响,气泡在竖直方向上沿毛细管轴向四周扩散。     

乘用车尾门密封条的压缩仿真分析

先对乘用车尾门密封条三元乙丙橡胶密实胶和海绵胶进行力学性能试验,确定2种材料的本构模型,然后采用Abaqus有限元分析软件对尾门密封条的压缩过程进行仿真分析。结果表明:尾门密封条的海绵胶泡管应力、应变和应变能均较大,海绵胶与密实胶接触部位有较大的应变和应变能;尾门密封条的仿真与试验压缩力-压缩量曲线拟合良好,试验压缩力平均误差不超过10%,仿真与试验结果一致性好。     

钢丝帘布的剥离测试方法研究

针对钢丝帘布剥离测试结果的系统性不稳定情况,研究剥离力测试结果的影响因素。结果表明:利用夹持端包布提高夹持摩擦力不能改善剥离测试效果,反而导致试样水平端面硫化压力分布不均造成剥离力下降;帘布间敷贴带束胶片虽然能大幅提高剥离力,但从剥离后覆胶状态来看更多反映的是帘布间胶料的撕裂强度;剥离拉伸速率越大,胶料破坏方向越平直,剥离力有下降趋势;硫化时间太长导致的硫化返原可明显降低剥离力。     

正交并联六轴力传感器耦合误差测量模型及实验分析

为解决并联六轴力传感器量程提升受限问题,设计了一种正交构型并联六轴力传感器。正交并联六轴力传感器是基于并联六轴力传感器的一种构型上的改进,具有承载能力强、解耦性能良好的优势,但同时该力传感器的耦合误差输出具有自身的特点。考虑该力传感器测量分支间摩擦以及正交结构自身特点引起的耦合误差输出,建立了正交并联六轴力传感器耦合误差测量模型。基于所建立的测量模型,通过数值算例分析探讨了传感器设计参数与两种耦合误差输出之间的影响关系,据此研制了一种正交并联六轴力传感器。最后对传感器样机进行了实验,得到其误差分布及检验测量精度。实验所得传感器各维力/力矩在各方向误差分别为0.43%/0.31%,0.18%/0.68%,0.80%/1.28%。     

基于活动拉深筋过拉深工艺的高强钢S梁扭曲回弹控制研究

采用CAE分析与现场调试相结合的方法,研究了高强钢变截面S梁拉延后的扭曲回弹规律,发现拐角特征是S梁发生扭曲回弹的关键影响因素。通过对拐角截面的应力和变形分析,解释了拐角造成扭曲回弹的原因,并设计了成形筋,以控制拐角造型引起的扭曲回弹。在设计成形筋的基础上,比较了变压边力和活动拉深筋过拉深两种工艺方案对S梁扭曲回弹的改善效果。研究结果表明活动拉深筋过拉深工艺对S梁扭曲回弹的改善更有效。     

靶准直器悬臂Y向调整机构受力和变形研究

靶准直器是惯性约束核聚变靶场中的重要部件,其在靶室中的位姿是保证靶定位瞄准精度的主要因素之一。为了实现微米级的定位瞄准精度,需要利用调整机构对靶准直器位姿进行调整。本文采取理论分析、有限元仿真和实验验证相结合的方法对靶准直器悬臂Y向调整机构的受力变形和稳定性进行了研究。根据对Y向调整机构的受力变形分析,得到结构受力变形的理论关系式,可从理论上优化Y向调整机构的刚度和稳定性;基于有限元仿真对Y向调整机构进行相应约束条件下的稳定性分析和结构优化;利用实验装置对靶准直器整体稳定性进行实验测试。实验结果表明:Y向调整机构优化后,靶准直器静态Y向变形由原来的7.9μm减小至小于2μm,动态稳定性满足系统2μm/2h的稳定性要求。同时,试验、仿真和理论分析结果的变化趋势一致,验证了理论和仿真分析的正确性。     

How cryogenic techniques help in machining of nickel alloys? A review

Nickel alloys are extensively used in aerospace, automotive, marine, nuclear, petro-chemical and food processing industries due to properties like high strength, resistance to heat, resistance to corrosion, etc. However, machining of these alloys pose many challenges in machining such as: work hardening, high temperatures at the cutting zone, rapid tool wear, reduced tool-life, etc. Attempts are made to overcome these challenges by using various cryogenic techniques. This paper, therefore discusses different techniques such as cryogenic cooling, cryogenic treatment of tool and simultaneous use of cryogenic cooling of tool and heating of workpiece (hybrid technique) and their effects on machinability of Nickel alloys with the help of indicators like tool-life, surface roughness, residual stresses, etc. It is concluded that cryogenic techniques are helpful in improving the machining performance by way of improvement in tool-life and surface quality. This happens due to better cooling by cryogen and improved tool properties after cryogenic treatment. However, based on the published works, it is not possible to decide about the following: correct amount of cryogen required for cooling, appropriate cryogenic tool treatment cycle to be used and the best parameters for machining of Nickel alloys. Therefore, future research should focus on these aspects.     

A real time machining error compensation method based on dynamic features for cutting force induced elastic deformation in flank milling

During the machining process, cutting forces cause deformation of thin-walled parts and cutting tools because of their low rigidity. Such deformation can lead to undercut and may result in defective parts. Since there are various unexpected factors that affect cutting forces during the machining process, the error compensation of cutting force induced deformation is deemed to be a very difficult issue. In order to address this challenge, this article proposes a novel real time deformation error compensation method based on dynamic features. A dynamic feature model is established for the evaluation of feature rigidity as well as the association between geometric information and real time cutting force information. Then the deformations are calculated based on the dynamic feature model. Eventually, the machining error compensation for elastic deformation is realized based on Function Blocks. A thin-walled feature is used as an example to validate the proposed approach. Machining experiment results show that the errors of calculated deformation with the monitored deformation is less than 10%, and the thickness errors were between ?0.05 mm and +0.06 mm, which can well satisfy the accuracy requirement of structural parts by NC (Numerical Control) machining.     

电磁驱动式无针注射器设计及力学和运动仿真

针对目前广泛使用的机械式和气动式无针注射器存在的不能持久使用和结构笨重等缺点,设计了基于使用直流电电源的电磁驱动无针注射装置,介绍了一种新的设计方案。将电磁式无针注射系统按电磁动力部分和流体部分分别建立数学模型,推导出相应的公式。分别对电磁动力部分及流体部分进行仿真分析,绘制了电流、铁芯相对位置及其所受电磁力大小的关系图,安瓿杆推力与喷射口压力、流体速度的关系图。结果表明：无针注射器的动力部分符合推力的设计要求,安瓿的喷射压力与射流速度达到了刺入人体表层皮肤的要求。     

Direct manipulation of metallic nanosheets by shear force microscopy

Micro/nanomanipulation is a rapidly growing technology and holds promising applications in various fields, including photonic/electronic devices, chemical/biosensors etc. In this work, we present that shear force microscopy (ShFM) can be exploited to manipulate metallic nanosheets besides imaging. The manipulation is realized via controlling the shear force sensor probe position and shear force magnitude based on our homemade ShFM system under an optical microscopy for in situ observation. The main feature of the ShFM system is usage of a piezoelectric bimorph sensor, which has the ability of self‐excitation and detection. Moreover, the shear force magnitude as a function of the spring constant of the sensor and setpoint is obtained, which indicates that operation modes can be switched between imaging and manipulation through designing the spring constant before experiment and changing the setpoint during manipulation process, respectively. We believe that this alternative manipulation technique could be used to assemble other nanostructures with different shapes, sizes and compositions for new properties and wider applications.