纸质机械运动机构设计研究

目的 实现玩具类产品的机械运动机构的纸质化.结合纸材料的力学特性,探索纸材料应用于机械产品制作的可行性,以及基于纸材料的机械零件结构的设计方法.方法 依据纸材料本身的特性,结合机械运动机构的传动方式,思考纸质机械机构设计的方式,总结出转动副、移动副、齿轮等各类典型机械运动机构纸质化设计方法,在实现运动功能的基础上确保运动零件的力学强度.同时以纸质齿轮设计为例,利用CorelDraw作为二次开发平台开发插件,降低纸质机械机构设计的操作难度.结论 以机械玩具产品为案例,对纸质材料力学特性的机械机构设计方法进行实践,论证了低成本机械玩具创意设计方法的可行性,为机械产品创意设计探索了新的材料选择,也为纸产品创新发展提供了更多的设计概念.     

Dynamic mechanical integrity of cylindrical lithium-ion battery cell upon crushing

Lithium-ion batteries are currently widely used in various industries, including automotive industry. Thus, the study of battery mechanical integrity subject to dynamic loading is critical for vehicle safety, which still remains rare. In this paper, first of all, by taking the advantage of previous efforts on quasi-static mechanical experiments on lithium-ion batteries, a new battery mechanical integrity criteria is suggested based on the mechanical strength theory. Further, by considering the strain rate and inertia effect of the battery structural and material, the dynamic mechanical behavior of lithium-ion battery is investigated. Different mechanical failure behaviors are obtained through the combination of numerical simulation and the suggested battery mechanical integrity criteria. Finally, parametric studies are carried out to further comprehensively reveal the battery dynamic mechanical integrity behavior. Results may shed lights on the lithium-ion battery dynamic mechanical behavior and safety research.     

面向维修的机械系统可靠度预测与仿真研究

机电产品在服役期间因零件失效而产生故障,重组维修破坏了原有的系统可靠性模型,因而需要对设备可靠性问题重新进行研究和评价。基于机电系统中零件的失效时间分布密度函数,研究了在重组维护过程中机电系统服役期间零件年龄结构的分布规律,发展了机电系统可靠性数学模型。通过仿真研究,探讨了系统服役期间年龄结构、可靠度和失效率的发展规律,定量地研究了失效时间分布密度函数的参数对系统可靠度的影响。这对于评估机械系统的可靠性和全生命周期的失效率,制定合理的维修策略具有重要意义。     

Optimization of noisiness of mechanical system by using a pneumatic tuner during a failure of piston machine

The stage of construction and operation of the machines requires monitoring of the steps causing negative effects on humans and environment in the form of noise during their use. Current technologies allow for appropriate optimization of mechanical systems as part of these machines. One possible optimization of the mechanical systems is considered to be the use of pneumatic tuners. The aim of this article is to demonstrate the effect of the pneumatic tuner on noisiness of mechanical system even in case of failure of mechanical drive part. Performed experimental measurement presents the change of noise in mechanical system by changing a pressure of gaseous medium in pneumatic tuner's compression space. The solution is an issue of appropriate mechanical tuning system when there is a change of dynamic parameters of the system and thus to change the entire mechanical system noise. Subsequent obtained results set out suggestions for the use of pneumatic tuners in mechanical systems in order to achieve the lowest possible noise during their operation mode.     

Mechanical reliability,how do we advance?

The development of theory and practice for electronic and mechanical reliability is described, and mechanical reliability is seen to be lagging in practice. Theory and practice are described for a project from conception to market feedback for mechanical as well as for electronic reliability. It is noted that for each phase theoretical and practical methods exist for mechanical as well as for electronic reliability analysis. Activities are listed which can strengthen mechanical reliability theory and practice.     

高聚物粘弹性力学模型的等当性

以描述高聚物粘弹性的三元件模型之一的弹簧与沃-开氏并联单元串接的为例,通过运动方程式从而推导出应力松弛模量G(t)的表达式,用初级的数学替代就可把这个G(t)转换为另一个形式,正好对应于弹簧与麦氏串联单元并联的关系,说明弹簧与伏-开氏并联单元串接的和弹簧与麦氏串联单元并联的力学模型互为等当,它们描述的是同一个高聚物粘弹性现象。模型的这种等当性为人们提供了很大的方便,我们可以根据使用的方便而任意选择其中的任一个模型。     

Mechanical control of nanomaterials and nanosystems

In situations of power outage or shortage, such as periods just following a seismic disaster, the only reliable power source available is the most fundamental of forces i.e., manual mechanical stimuli. Although there are many macroscopic mechanical tools, mechanical control of nanomaterials and nanosystems has not been an easy subject to develop even by using advanced nanotechnological concepts. However, this challenge has now become a hot topic and many new ideas and strategies have been proposed recently. This report summarizes recent research examples of mechanical control of nanomaterials and nanosystems. Creation of macroscopic mechanical outputs by efficient accumulation of molecular-level phenomena is first briefly introduced. We will then introduce the main subject: control of molecular systems by macroscopic mechanical stimuli. The research described is categorized according to the respective areas of mechanical control of molecular structure, molecular orientation, molecular interaction including cleavage and healing, and biological and micron-level phenomena. Finally, we will introduce two more advanced approaches, namely, mechanical strategies for microdevice fabrication and mechanical control of molecular machines. As mechanical forces are much more reliable and widely applicable than other stimuli, we believe that development of mechanically responsive nanomaterials and nanosystems will make a significant contribution to fundamental improvements in our lifestyles and help to maintain and stabilize our society.     

Design of mechanical clinching tools for joining of aluminium alloy sheets

The purpose of this study is to propose the design method of mechanical clinching tools, which is used to join aluminium alloy sheets in automobiles. Based on the analytical model used to predict the strength of the mechanical clinched joint, the design method of clinching tools that can satisfy the required joint strength is proposed. The analytical model has been defined as a function of the neck-thickness and the undercut, which are the presented mechanical clinched joint geometry. And joint geometry is defined by the shape parameters of the clinching tools. To obtain the desired joint strength, the required neck-thickness and undercut are inversely calculated from the analytical model. The mechanical clinching tools that join Al6063 alloy sheets are designed by the proposed method. FE-analysis and mechanical clinching test were performed for optimal conditions obtained from the proposed design method. The result of the FE-analysis and that of the mechanical clinching test showed good agreement of the clinched joint geometry. The H-type tensile test for mechanical clinched joint was carried out to evaluate the strength of the mechanical clinched joint designed by the proposed design method. The result of the tensile test showed that the fracture load satisfied the required joint strength. Also, the top-hat impact test was performed to evaluate the feasibility of using mechanical clinching for automotive component assembly. The result of impact test showed that mechanical clinching was able to produce similar crash resistance as self-piercing riveting.     

Characterization of the mechanical dissipation in shape-memory alloys during stress-induced phase transformation

The high reversibility of the martensitic transformation occurring in shape-memory alloys (SMAs) is at the origin of the mechanical performance of these materials. Infrared thermography is employed in this study to measure the mechanical dissipation produced by Cu–Zn–Al SMA specimens during stress-induced phase transformation. In practice, temperature change is first measured on the surface of a specimen subjected to cyclic mechanical loading at constant ambient temperature. The heat produced by the material can then be deduced from the temperature change by using the heat diffusion equation. The heat associated to mechanical irreversibility is expected to be very low compared to the other heat quantities produced by the material (such as the latent heat due to phase change and the heat due to thermoelastic coupling), so measuring this quantity requires special attention, as emphasized in this paper. The procedure which enables us to extract the mechanical dissipation from the measured heat source is first presented. The technique is then applied to two types of specimens: martensitic and austenitic. Different values of mechanical dissipation were measured, thus revealing different levels of mechanical irreversibility.     

Fe-Ni机械合金化过程中马氏体的形成及相变

研究了Ni含量、机械合金化工艺参数对Fe-Ni机械合金化过程中马氏体相变的影响及其机理.结果表明:在Fe-Ni机械合金化过程中存在着马氏体相变,但继续机械合金化马氏体是否会发生逆转变主要由Ni含量决定.当Ni≤30%(质量分数,下同)时,机械合金化引起的材料局部温度未达到形变促使马氏体相变逆转变开始温度,因此继续机械合金化马氏体不转变.对于Fe-35Ni,形变促使逆转变的开始温度低于局部温升,马氏体将向奥氏体转变.当Ni含量为35%时,随着机械合金化时间的延长、球磨速度和球料比的提高,机械合金化可以提供的相变驱动力增大导致奥氏体的量逐渐增多.     

Bioinspired Materials with Self-Adaptable Mechanical Properties

Natural structural materials, such as bone, can autonomously modulate their mechanical properties in response to external loading to prevent failure. These material systems smartly control the addition/removal of material in locations of high/low mechanical stress by utilizing local resources guided by biological signals. On the contrary, synthetic structural materials have unchanging mechanical properties limiting their mechanical performance and service life. Inspired by the mineralization process of bone, a material system that adapts its mechanical properties in response to external mechanical loading is reported. It is found that charges from piezoelectric scaffolds can induce mineralization from surrounding media. It is shown that the material system can adapt to external mechanical loading by inducing mineral deposition in proportion to the magnitude of the stress and the resulting piezoelectric charges. Moreover, the mineralization mechanism allows a simple one-step route for fabricating functionally graded materials by controlling the stress distribution along the scaffold. The findings can pave the way for a new class of self-regenerating materials that reinforce regions of high stress or induce deposition of minerals on the damaged areas from the increase in mechanical stress to prevent/mitigate failure. It is envisioned that the findings can contribute to addressing the current challenges of synthetic materials for load-bearing applications from self-adaptive capabilities.     

2219铝合金搅拌摩擦焊接头组织和性能的不均匀性研究

目的 针对2219铝合金搅拌摩擦焊接头受焊接热作用和机械搅拌作用的影响,极易产生组织和力学性能不均匀的情况,深入研究接头的局部力学性能,为焊接工艺优化提供理论指导.方法 采用显微组织分析与数字图像相关(DIC)技术测试相结合的方法,对2219铝合金搅拌摩擦焊接头的组织和局部力学性能进行表征,并建立搅拌摩擦焊接头各区域的局部力学性能模型.结果 2219铝合金搅拌摩擦焊接头的力学性能薄弱区为热机影响区.试样断裂前该区域局部应力达到345 MPa,局部应变为18.9％,而此时母材应变仅为1.91％.结论 热机影响区的组织在焊接热作用和机械搅拌的双重作用下发生了粗化和软化,导致该区的力学性能降低,是整个焊接接头的薄弱区域.     

多失效模式机械系统可靠性稳健设计方法研究

将机械系统可靠性设计理论和稳健设计方法相结合,讨论了多失效模式机械系统可靠性稳健设计问题,提出了多失效模式机械系统可靠性稳健设计的计算方法．把可靠性灵敏度融入可靠性优化设计模型之中,将机械系统可靠性稳健设计归结为满足可靠性要求的多目标优化问题．在基本随机参数的前二阶矩已知的情况下,可以迅速准确地得到机械系统可靠性稳健设计信息．     

高聚物粘弹性力学模型计算中容易被忽视的一个基本问题

在应用粘弹性力学模型模拟线形高聚物应力松弛现象时,不能忽视一个基本问题:在维持总形变不变的情况下,总应力是在逐渐衰减的,即应力不是恒定值。本文对高聚物力学松弛及粘弹性的本质进行了讨论。     

On-line mechanical unbalance estimation for permanent magnet synchronous machine drives

An on-line mechanical unbalance estimation for permanent magnet synchronous machine (PMSM) drives is presented. At high speeds, either rotor or mechanical load unbalance generates vibration that can cause mechanical failure such as a defect of a bearing or shaft. To prevent failure and minimise mechanical vibration, the amount of the rotating unbalance should be detected in real time. The information of the estimated unbalance can be utilised to manage an operation to achieve the durability of mechanical parts. The dynamic nature of a mechanical system with a PMSM with regard to unbalance is investigated. From this examination, the models of the stator current in time and frequency domains for PMSMs are presented to develop a robust real-time unbalance estimation scheme. Based on the modelling and analysis of a rotating mechanical system using a PMSM drive, a compact unbalance estimation algorithm is proposed. The algorithm is combined with an open-loop torque observer and an unbalance estimator using a filter. Experimental results show the validation of the developed model and the proposed on-line unbalance estimation scheme.     

膨胀岩力学性质试验与巷道支护参数的预测研究

试验研究膨胀岩的物化和力学性质,建立力学模型,分析预测巷道的力学行为是研究的主要目的。首先建立了膨胀岩的分析试验模型,对膨胀岩的物化和力学性质进行了试验,总结出深度与密度、孔隙比、吸水率与膨胀率、膨胀力、强度、弹性模量的关系;其次建立了膨胀岩的力学模型,通过理论模型与工程模型的耦合分析,提出了巷道底臌、应变及支护应力的预测计算方法;最后通过工程试验的分析对比,验证了理论计算和工程实测具有较高的拟合性。研究成果为同类或相近条件下膨胀岩巷道支护参数的预测计算提供了依据。     

Tailoring the Mechanical Properties of 3D Microstructures Using Visible Light Post‐Manufacturing

The photochemistry of anthracene, a new class of photoresist for direct laser writing, is used to enable visible‐light‐gated control over the mechanical properties of 3D microstructures post‐manufacturing. The mechanical and viscoelastic properties (hardness, complex elastic modulus, and loss factor) of the microstructures are measured over the course of irradiation via dynamic mechanical analysis on the nanoscale. Irradiation of the microstructures leads to a strong hardening and stiffening effect due to the generation of additional crosslinks through the photodimerization of the anthracene functionalities. A relationship between the loss of fluorescence—a consequence of the photodimerization—and changes in the mechanical properties is established. The fluorescence thus serves as a proxy read‐out for the mechanical properties. These photoresponsive microstructures can potentially be used as “mechanical blank slates”: their mechanical properties can be readily adjusted using visible light to serve the demands of different applications and read out using their fluorescence.     

静不稳定机械式衡重台力学分析和校准方法

为解决机械式衡重台因静不稳定性难以校准的问题，分析机械式衡重台的测量原理和力学特点，提出机械式衡重台校准方法，通过减少机械式衡重台非平衡状态下载重架的最大偏转角度，实现校准时的测量不确定度控制，保障校准结果的准确性。利用该方法对机械式衡重台进行校准，并开展测量不确定度分析，结果表明扩展不确定度U = 84 g（k = 2），验证了该方法的有效性。研究成果对于促进水下航行体产品力学计量领域的发展具有积极作用，为水下航行体产品试验研究提供了有力支撑。     

船用高压组合机械密封装置的设计

水下舰艇武器推进泵的机械密封装置的工作压力波动、使用频率小,并要求可靠性高。根据这些使用要求和技术要求,对高压组合机械密封装置进行研究,分析了关键技术,给出结构设计方法、关键参数的选择以及设计计算方法,并对密封环受力变形问题采用有限元法分析。介绍了专门针对船用高压机械密封进行可靠性试验的试验装置,并对所设计的机械密封装置进行了试验,试验结果表明该密封装置能够很好地满足使用要求。     

机械力活化合成AIN粉末

机械力活化由于能大幅度地降低AIN粉末反应合成温度,缩短反应时间,是制备A1N粉末经济有效的实用化途径之一,简要介绍了机械力活化合成A1N粉末的反应机制,并分析了机械力活化对A1N粉末合成过程的促进作用。