压力容器机座焊缝开裂原因及应对措施

为探讨某压力容器的振动原因及机座与上封头连接焊缝的开裂原因,采用电测方法对压力容器振动频谱及动应力进行了现场测量,建立了压力容器流固耦合系统的有限元分析模型并进行了模态分析。分析结果表明,系统主振频率与系统某一阶固有频率相同,但与激励频率无关,系统发生了流固耦舍自激振动。应力测试结果表明,最大动应力位于机座与上封头连接的焊缝处,为正常工作应力的4—6倍;流固耦合引发系统自激振动使上封头出现局部弯曲振动,产生振动疲劳,导致机座与上封头连接焊缝开裂。分析认为对上封头进行补强可消除局部弯曲振动且能防止机座焊缝开裂。     

新型复合材料圆环联轴器膜片应力分析

针对当前的圆环金属膜片联轴器基本性能参数及特点，研制出一种新型各向异性材料的圆环金属联轴器膜片。利用ANSYS有限元程序对该膜片进行了应力计算及分析，并求出膜片3种工况及其组合引起的最大应力的大小及位置。结果表明，该新型复合材料膜片的最大应力明显小于金属膜片的最大应力。同时分析得出安装误差（尤其是轴向误差）所产生的应力是对膜片产生的主要应力，因而在实际安装当中，应尽可能提高安装精度，减少偏差。     

磁致伸缩效应在生物传感器中的应用

我们致力于无线磁传感技术的研究,该技术基于磁致伸缩原理设计。在外加交变磁场中,磁性膜片受磁场激发产生磁矩,将磁能转换为机械能,并产生沿长度方向伸缩振动,即磁致伸缩。当交变磁场频率与磁性膜片机械振动频率相等时,磁片产生共振,具有最大振幅,此时振动频率为磁性膜片共振频率。当磁性膜片传感器表面负载质量发生变化时,其共振频率也会随之改变。由于磁性膜片本身是磁性的,其伸缩振动产生磁通,产生的磁通可由检测线圈检测,信号经放大后由外部仪器测定。磁弹性传感器中信号的激发与传送是通过磁场进行的,传感器与检测仪器之间没有任何物理连接,属于无线无源传感器。磁弹性传感器的无线无源特征使其在活体、在体分析、密闭容器中的无损检测等领域具有广泛的应用前景。如pH传感器、免疫传感器。     

基于齿科隐形正畸材料力学性能的比较研究

通过测试不同厚度热压膜材料的拉伸性能及应力松弛性能,为选适宜的热压膜材料制备隐形矫治器提供指导。利用0.5、0.75、1 mm厚度的Erkodur、Biolon、Scheu、DR膜片,在多功能静力学试验机上测试应力/应变,并测试厚度1.0 mm四种膜片的应力松弛。每种材料随着厚度的增大,其弹性模量及最大应力均随之增加。其中Scheu1.0 mm膜片的弹性模量和最大应力最大,DR 0.5 mm膜片弹性模量和最大应力最小。Scheu膜片应力松弛性能优于其他三种热压膜片。在厚度小于1.0 mm的情况下,同种膜片的不同厚度具有不同的力学性能,材料的力学性能受厚度的影响。厚度越厚,材料的弹性模量和最大应力越大。在预设1.25 mm位移量下,热压膜片产生的回复力随时间衰减。     

硫化机全焊接横梁振动时效数值分析

采用ANSYS有限元分析软件,通过模态分析和谐响应分析,对1665型双模定型硫化机全焊接横梁的振动时效工艺关键参数（激振力、激振频率及激振点等）进行预测.由模态分析可知,横梁前10阶振动4个优选固有频率中318 Hz的波浪振型较为合理,并据此确定其激振点.通过谐响应分析获得一定激振频率、不同激振力时横梁所受最大动应力分布,并根据国家标准确定激振力取值范围为[300,690] kN.     

高温浓硫酸液下泵振动分析及处理

正江西铜业公司贵溪冶炼厂硫酸一系统长轴浓酸泵运转几年来,整体振动大,尤其是出口管弯头的最大振动幅值为180μm。停车检查泵时发现:刚性联轴器连接螺栓出现断裂,膜片有破损现象。由于泵振动大而导致系统停车的情况时有发生,为此贵溪冶炼厂技术人员进行了全面分析,并进行了针对性的改进措施。     

压力容器消除应力技术评述（二）

（续上期）３振动消应处理３．１振动消应的原理及方法振动消应的实质就是通过振动的形式施于工件一个动应力，当动应力与工件内部的残余应力叠加后达到材料的屈服极限时，工件便会产生微观的、局部的、甚至是宏观的、整体的塑性变形，从而达到降低并均化工件内部残余应力...     

汽轮发电机组的防振对策

振动是评价汽轮发电机组运行状况的重要指标。一定程度是振动是允许的,振动过大,将使部件承受过高的动应力,使紧固部件松驰,滑动部件磨损或小间隙配合的动静部件间发生摩擦,甚至会造成汽轮机叶片因动应力过高而疲劳折断。     

振动对往复式压缩机出口管系动力特性影响分析

往复式压缩机出口管系振动会引发重大安全事故,影响压缩机等设备的正常运行,给企业造成巨大的经济损失。往复式压缩机和输送管系的振动均能传递到出口管系上,引发出口管系振动,因此对往复式压缩机和输送管系振动原因进行分析,在此基础上运用ANSYS软件对某化工厂往复式压缩机出口管系进行模态分析。分析结果显示:整段出口管系的位移变形量均是以最大位移变形量为中心向三端逐渐减小,低模态阶数时最大位移变形发生在压缩机出口法兰和管道连接处附近,高模态阶数时最大位移变形发生的位置逐渐远离压缩机出口法兰和管道连接处;随着模态阶数的增加,最大位移变形发生的部位逐渐扩大,四阶模态振型时最大位移变形部位达到最大,证明管道固有频率在激发的同时管道也在进行固有振动,此时固有频率和振动频率相近或相等。该结果对往复式压缩机出口管系消振改造措施的研究具有十分重要的指导意义。     

膜盒变送器膜片内部点蚀现象产生原因分析

通过采用扫描电镜-EDS能谱联用及离子色谱等分析方法,对某煤化工装置发生膜片内部点蚀的膜盒变送器内的硅油及膜片进行了分析,通过综合比较分析结果,对膜盒内出现点蚀现象的可能原因进行了推测。     

Mechanical properties and morphological behavior of calcium carbonate‐filled polypropylene in dynamic injection molding

A custom‐made electromagnetic dynamic injection molding machine was adopted to study the mechanical properties and morphological behavior of calcium carbonate‐filled polypropylene (PP) in a dynamic injection molding process. The influence of vibration amplitude and frequency on the mechanical properties and morphological behavior of samples was investigated using tensile tests, notched Izod impact tests, differential scanning calorimetry, and scanning electronic microscopy. The tensile stress and the impact stress for all samples investigated were found to increase in a nonlinear manner with increasing vibration amplitude and frequency. The tensile stress reached a maximum value at about 8 Hz and 0.15 mm for neat PP and PP filled with 3, 20, and 30 wt% CaCO₃. For PP filled with 40 wt% CaCO₃, the tensile stress reached a maximum value at about 12 Hz and 0.2 mm. The impact stress reached a maximum value at about 12 Hz. From DSC experiments it was shown that the melting temperature slightly increased, but no new polymeric crystalline peak appeared under the vibration force field. The CaCO₃ particles were diffused easily and distributed evenly in the PP melt under the vibration force field, so it is very useful in improving the quality of injection products. Copyright © 2006 Society of Chemical Industry     

不同含水率下赤泥改良土的动弹模及阻尼比研究

为研究不同初始含水状态下赤泥改良土的动力学参数,利用GDS动三轴仪对不同含水率下改良土进行了不同频率下的循环加载试验,研究分析了振次、含水率、加载频率对改良土动弹性模量和阻尼比的影响.试验结果表明:动应力幅值一定时,动弹模随振次增加基本无变化,阻尼比随振次增加呈波动变化,且提出并证明了可用第10振次下的动弹模阻尼比值代表各级荷载下的动弹模阻尼比值;动弹模随动应变幅值的增加先增大后减小,并用二次函数对其进行了拟合,阻尼比随动应变的增加先减小后增大;改良土动弹模在其最优含水率处达到最大,较高的含水率使改良土动弹模明显下降;较小应变幅下动弹模随频率增加而减小,较大应变幅时动弹模随频率增加而增大,阻尼比在加载频率较高时较大.     

Fast-flowing LBE corrosion of the SiC pump impeller: Numerical and experimental investigations

In order to determine the stress state and the specific dynamic corrosion behaviors of the cooling pump impeller in the liquid lead-bismuth eutectic alloy (LBE), the numerical and the experimental investigations on the fast-flowing LBE corrosion behaviors of the SiC impeller were conducted. The distributions of stress and displacement of the SiC impeller were simulated, and then the microstructure and mechanical properties of the corroded impeller were characterized. The results indicated that the SiC impeller met the strength requirement of 1000 rpm in LBE, and the dynamic LBE corrosion had little effect upon structure safety of the SiC impeller. The maximum stresses of the SiC impeller without and with LBE loading were .452 and 9.736 MPa, respectively. The maximum displacements of the SiC impeller without and with LBE loading were 76.385 and 4.096 μm, respectively. The LBE loading reduced the axial displacement of the impeller and acted as an impeller stabilizer to some extent. Blade elongating and flapping were the main vibration mode of the SiC impeller. The mechanical properties of the SiC impellers before and after corrosion were basically the same.     

振动注塑PP/CaCO3的拉伸蠕变研究

采用自制的机械振动注塑机,在不同振动频率和振动压力下成型PP/CaCO3试样.考察了试样的拉伸蠕变.结果表明,当振动压力一定时,PP/CaCO3的拉伸应变随着振动频率的增加先增大后减小,当振动频率为15 Hz时达最大;而当振动频率一定时,材料的拉伸应变随着振动压力的增大而减小.通过对不同成型条件下注塑的PP/CaCO3材料进行了短时拉伸实验和动态力学性能测试,从材料柔性和刚性分析其蠕变原因.     

Analysis of the Ripple Current in a 5 kW Polymer Electrolyte Membrane Fuel Cell Stack

Polymer electrolyte fuel cell systems are increasingly being used in applications requiring an inverter to convert the direct current (DC) output of the stack to an alternating current (AC). These inverters, and other time‐varying inputs to the stack such as the anode feed pressure, cause deviations from the average stack current, or ripple currents, which are undesirable for reasons of performance and durability. A dynamic fuel cell model has been developed and validated against experimental data for a 5 kW fuel cell stack, examining in detail the ripple current behaviour. It was shown that the ripple currents exceed the 2% maximum recommended value, and may lead to long‐term degradation of the fuel cell stack.     

脉动注射对模腔压力的影响

介绍了立式液压振动注射机的工作原理.在立式液压振动注射机上进行传统注射成型及动态注射成型,制取低密度聚乙烯(LDPE)圆盘试样,利用自制的压力传感器及数据采集系统对模腔压力进行实时采集.实验结果表明,传统注射成型与动态注射成型的模腔压力随时间的变化趋势基本相同;模腔压力波动频率与柱塞杆振动频率相同;随着柱塞杆振动频率、振幅的增大,模腔压力的波动幅度增大,平均模腔压力增大,最大模腔压力也增大.     

The stress relaxation behavior and mechanical properties of polypropylene and polypropylene/CaCO3 in mechanical vibration injection molding

The influence of vibration pressure and frequency on the mechanical properties and stress‐relaxation was investigated via stress‐relaxation test and tensile test. First, it had been observed in the tensile test that the tensile fracture elongation reached the maximum at 20 Hz for polypropylene (PP) and 15 Hz for polypropylene/calcium carbonate (PP/CaCO₃), respectively. With the increasing vibration pressure, the tensile fracture elongation would decrease. Second, the dynamic mechanic analysis has been used to test loss angle tangent value of the material. After the dynamic mechanic analysis, the simples have been installed in the universal tensile testing machine which applies the 2% strain on the simples. From these experiments, it has been discovered that the trend of the changes of stress‐relaxation is similar with the trend of the changes of loss angle tangent value. When the vibration frequency reaches the 20 Hz for PP and 15 Hz for PP/CaCO₃, the stress‐relaxation is larger than that of other materials prepared at the same pressure (10 Mpa); meanwhile, the stress‐relaxation of these materials, which has been prepared at the same frequency (10 Hz), decreases with the increasing vibration pressure. According to above tests, it is also very useful to improve the stress relaxation properties via changing the condition of the vibration field. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Cavity Pressure Response and Melt Flow Length During Dynamic Injection Molding

Employing a spiral channel mold and a set of cavity pressure measurement equipments from Kistler, the cavity pressure response and the maximum flow length during dynamic injection molding were studied. The processing conditions include injection velocity, injection pressure, mold temperature, vibration frequency, and vibration amplitude. The result shows that the maximum flow length can be improved by the dynamic injection molding. Especially at the lower injection pressure, the maximum flow length can be improved about 15%. From the curves of cavity pressure, we found that the cavity pressure undulated regularly in the dynamic filling phase, which is conduced by the screw vibration. During dynamic injection molding, the viscosity of the polymer flow reduces, and the capability of mold filling improves.     

商用车驱动桥壳的有限元分析

针对东风汽车某商用车驱动桥壳结构上存在壁厚、质量重、成本高等不足,提出了用Pro/E软件对商用车驱动桥壳进行参数化建模,运用ANSYS有限元分析软件进行强度、刚度和动态特性分析,计算出桥壳在最大载荷下的应力分布以及在自由状态下的固有频率和振型。由此分析该桥壳是否符合桥壳结构强度与刚度要求,是否与路面引起共振。为后面能否进行轻量化研究提供依据。