摘要：Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream *** paper presents a comprehensive review of the progress that has been achieved in the past years about cavitation in valves including both mechanical heart valves and control *** review is divided in the following parts,namely the location where there is a high possibility of the occurrence of cavitation,the parameters that affect cavitation intensity,and the methods to minimize cavitation *** should be noticed that although simulation has been widely used,advanced experiments are still needed in order to obtain accurate analysis of cavitation in valves and the cavitation model still needs to be improved.

摘要：Near net-shape production of complex parts with higher mechanical properties is one of the most important final goals of the recent researches on the semi-solid *** the knowledge of the influence of every parameter on the properties of final parts is the key in the production of high quality complex *** these parameters forming temperature and velocity,and reheating and holding times have the greatest effects on the final mechanical properties of the *** influence of the parameters of non-dendritic billet production,forming speed,temperature and holding time on the properties of semi-solid extruded parts were ***-slope method was employed in order to produce non-dendritic *** material used was A356 aluminum *** the number of the parameters influencing the final properties of the parts was high(these parameters include:cooling slope angle,ram velocity,temperature and holding time),the final number of the experiments required would be n4,in which n is the number of the states of the parameters(5 in our case).In order to reduce this amount,design of experiments Tachuchi method was employed(design L25).Using this method the number of required experiments was reduced to *** the experiments the prepared semi-solid samples were extruded under isothermal condition and with 5 different ram *** tensile tests were conducted on the extruded parts and the mechanical properties of the parts were *** obtained results analyzed with MiniTab and the influence of each of the parameters and also the percentage of its influence were *** an optimum region for the parameters was *** temperature,ram speed,slope angle and holding time have more important effects descendingly.

摘要：Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric ***,their densification during sintering still poses challenges for researchers,and their mechanical properties are rather *** this study,SrAl_(2)Si_(2)O_(8)(SAS),with low melting point and high strength,was introduced into the h-BN ceramics to facilitate the sintering and reinforce the strength and ***,BN-SAS ceramic composites were fabricated via hot press sintering using h-BN,SrCO_(3),Al_(2)O_(3),and SiO_(2) as raw materials,and effects of sintering pressure on their microstructure,mechanical property,and thermal property were *** thermal shock resistance of BN-SAS ceramic composites was *** show that phases of as-preparedBN-SAS ceramic composites are h-BN and h-SrAl_(2)Si_(2)O_(8).With the increase of sintering pressure,the composites’densities increase,and the mechanical properties shew a rising trend followed by a slight *** a sintering pressure of 20 MPa,their bending strength and fracture toughness are(138±4)MPa and(1.84±0.05)MPa·m^(1/2),*** sintered at 10 MPa exhibit a low coefficient of thermal expansion,with an average of 2.96×10^(-6) K^(-1) in the temperature range from 200 to 1200℃.The BN-SAS ceramic composites prepared at 20 MPa display higher thermal conductivity from 12.42 to 28.42 W·m^(-1)·K^(-1) within the temperature range from room temperature to 1000℃.Notably,BN-SAS composites exhibit remarkable thermal shock resistance,with residual bending strength peaking and subsequently declining sharply under a thermal shock temperature difference ranging from 600 to 1400℃.The maximum residual bending strength is recorded at a temperature difference of 800℃,with a residual strength retention rate of 101%.As the thermal shock temperature difference increase,the degree of oxida

摘要：Nano-SiO2 particles strengthened Ni-based composite coating was designed and prepared on steel substrate. The structures and nanoparticle content of the nano-SiO2/Ni composite coating were determined by SEM, EDS and TEM; and the micro mechanical properties were tested by nano-indentation technique. The results show that 56% of particles in the solution are dispersed in size of less than 100nm, the content of nanoparticles co-deposited in the coating doubles and structure of the coating is more compact and uniform than that of Ni coating. Nano-SiO2/Ni coating exhibits excellent micro mechanical properties, and the nanohardness and elastic modulus are 7.81GPa and 198GPa, respectively, which are attributed to finer crystal strengthening, dispersion strengthening and high-density dislocation strengthening of nano-SiO2 particles to the composite coatings.

摘要：Parameter optimization for a novel 3-DOF hybrid mechanical arm was presented by using a statistics method called the statistics parameters optimization method based on index *** kinematics and mechanics performance evaluation indices were proposed and discussed,according to the kinematics and mechanics analyses of the mechanical *** the assembly technique,a prototype of the 3-DOF hybrid mechanical arm was developed,which provided a basis for applications of the 3-DOF hybrid mechanical *** novel 3-DOF hybrid mechanical arm can be applied to the modern industrial fields requiring high stiffness,lower inertia and good technological efficiency.A novel 6-DOF hybrid humanoid mechanical arm was built,in which the present mechanical arm was connected with a spherical 3-DOF parallel manipulator.

摘要：研究使用mechanicalDesktop(MDT)软件对中国先进研究堆 (CARR)堆本体主要部件进行三维参数化建模 ,并通过尺寸及相关位置数值的变量驱动进行CARR堆本体初步设计及修改。三维参数化设计方法的应用大大提高了CARR堆本体的设计效率 ,缩短了设计周期 。

摘要：The design and implementation of mechanical domestic water meters in current industrial organization and intellectual properties have been registered as an invention to solve the problems of current meters. The device operation includes inquiry of printing, subscription connection and disconnection in an emergency. This system includes a software and hardware parts on the users and the control center connecting with two-way mobile phone. Central control software sends the message through the wireless telecommunication lines to the user’s software, requesting the desired information and also provides the commands needed to be sent through the same. The same information can also be submitted to the control center. Through the same way, some of advantages of this method are as follows: installing on existing meters, cheap cost of inquiry call meter, the possibility of declaring illegal manipulation to the control center, the exchange of information using information encoding, and manipulating digital meters applying minor changes.

摘要：文中通过对射流发电机工作原理、结构特点及作用荷载的分析，建立了射流发电机机械振动系统的动力优化设计数学模型，以结构尺寸为设计变量，使结构重量极小化，满足动力位移、应力响应、基频以及尺寸限等约束条件，利用振型迭加法和复合形法求解。优化和试验结果表明：经优化后，既减轻结构重量，又显著地提高了射流发电机的输出功率。

摘要：介绍了Autodesk AutoCAD mechanical软件的转动惯量和挠度线的计算功能,并以实例介绍其在货架横梁设计中的应用,对横梁的截面进行惯性矩的计算,并用惯性矩的计算结果计算挠度线和安全系数,提高了计算精度并加快了设计进度。

摘要：介绍了Autodesk公司的AutoCAD mechanical软件及其轴生成器和轴计算的基本功能,介绍了基于AutoCAD mechanical的轴的设计的基本步骤,并以实例介绍了轴的绘制和设计计算的方法,最后讨论了各个设计步骤的注意事项和优缺点。实践表明,采用AutoCAD mechanical可以快捷绘制出机械图样,直观、方便、准确实现轴的设计计算,减少了设计时间,大大提高工作效率,但存在一些缺陷,如强度校核点需要用户自己寻找,结果是否符合要求需要用户自己判断。