Durability improvement method for plastic spur gears

An experimental investigation of power-transmission plastic spur gears was performed by inspecting both the characteristics of wear and durability, and a durability improvement method is proposed that either drills an internal hole or inserts a steel-pin in the internal hole of the gear tooth, and this proposed method was verified. In the case of acetal gears, the amount of wear was observed to increase with the development of plastic deformation, and an increase in tooth stiffness occurred due to the brittle material property of acetal. On the other hand, in the case of nylon gears, the proposed method was shown to reduce the tooth temperature compared to the original gear, thus reducing the amount of wear and prolonging service life. Hence, the proposed method was proven to be practically applicable to plastic gears made from soft polymers that show visco-elastic properties such as nylon.     

Joint optimization of interrelated thermophysical processes in metal working systems based on system quality criteria

A method is proposed to solve the joint optimization problem based on system quality criteria for the thermophysical processes of preheating and subsequent plastic deformation of metal semi-finished products in industrial metal working systems with a free choice of the admissible initial temperature states before plastic deformation that integrate these processes in a single process system. Potentials for practical applications of the method is illustrated by the example of a process system for forming pressed articles from aluminum alloys.     

Improved methodology for determining tensile elastic and plastic strain components of alloy 617

This paper presents an improved methodology for calculating tensile elastic and plastic strain components in total creep strain, which are needed in the generation of the isochronous stress-strain curves (ISSC). The procedures for the RCC-MR code and Blackburn’s methods to determine the total strain are analyzed in detail, and a new method is proposed to determine the tensile elastic and plastic strain components. To practically obtain the tensile elastic and plastic strain components for Alloy 617, high-temperature tensile tests were conducted at 800, 850, 900, and 950°C. Using the tested data, three methods of the RCC-MR code, Blackburn, and the newly proposed method were applied and compared. In the elastic regime, the three methods were identical in the tensile curves, but in the plastic regime, Blackburn’s method was higher in the stress-strain curves than the RCC-MR code. The difference gap for the two methods was larger with an increase in the plastic strain. In addition, the proposed new method revealed almost midway values for the two methods. It was suggested that the proposed method is useful to determine tensile and plastic strain components.     

飞机管路连接件装配偏差对密封性影响的仿真分析与试验验证*

为研究管道装配偏差对管路连接件密封性能的影响规律,建立管道连接件模型,提出有效密封的判定条件,并通过静力学仿真分析管接头接触面摩擦因数、管道装配偏差(轴向、径向及角度)对管接头连接件密封性能的影响。结果表明:拧紧力矩的增加会使密封性能增强,但超过某一极限值,管路连接件可能发生破坏;管接头与管道接触面的摩擦因数增加,密封性能降低;装配过程中的轴向偏差会降低密封性,甚至失去密封性;径向偏差和角度偏差会稍稍降低密封性,但管道会出现塑性变形。建立管道密封试验系统,试验验证了仿真分析的正确性。     

考虑硬度变化的结合面法向接触刚度分形模型*

基于分形几何理论,考虑微凸体因应变硬化而造成弹塑性变形阶段硬度随变形量变化而变化,建立结合面第一、第二弹塑性变形阶段单次加载刚度分形模型。推导出在计入硬度变化的情况下,单个微凸体在弹塑性变形阶段法向接触刚度与接触面积之间的关系式,进而得出结合面在弹塑性变形阶段法向接触刚度与接触面积、接触载荷之间量纲为一的关系式,并通过仿真分析得出相关参数对结合面法向接触刚度的影响。仿真结果显示:考虑硬度变化时,结合面量纲一法向接触刚度的值与法向实际接触载荷、实际接触面积之间存在关系;结合面法向接触刚度随着分形维数D的增大而增大;分形维数一定时,结合面法向接触刚度随表面长度尺度参数G值增大而增大。     

碳纤维增强复合材料的超声无损检测

本文介绍了通过对超声信号的频谱分析,利用超声信号的频谱特征参数无损测量碳纤维增强树脂基层压板复合材料微气孔含量、纤维体积含量的新方法。     

含裂纹强度失配焊接接头弹塑性变形分析

采用有限元方法对平面应变条件下含裂纹不同强度失配的平板拉伸焊接接头的弹塑性变形进行了分析,研究了焊缝与母材强度失配系数、焊缝硬化性能、裂纹长度等对接头塑性变形的影响。结果表明：强度失配系数对接头塑性变形有显著影响。低匹配时,变形首先集中在焊缝中,而高匹配则对焊缝起到了一定的保护作用。失配系数一定时,不同焊缝硬化性能接头的塑性变形发展趋势是一致的;但当外载较大时,局部塑性变形程度不同,焊缝的硬化性能降低,裂尖塑性变形增大。
     

力学性能不均匀性对焊接接头三点弯曲试样塑性区发展规律的影响

利用弹塑性有限元方法对焊接接头试样在三点弯曲试验中塑性区的发展情况进行了计算。分析了不同的裂纹深度、强度组配，焊缝宽度以及不同位置裂纹的焊接接头试样对塑性区形状发展的影响规律。分析结果显示，不同强度组配和几何特征的焊接接头试样对裂纹尖端塑性区的发展规律有较大的影响，由于裂纹尖端拘束程度的不同会造成塑性区的形状和尺寸的改变，因此在做焊接接头试样三点弯曲试验时，可能会得出与均质材料试样不同的驱动力曲线     

Artificial lubrication of joint prostheses

The great success of total joint replacement in surgery has been disturbed mainly by the later loosening of the prostheses and wear of the plastic components. In an attempt to improve long term performance, and to eliminate the adverse effects of wear debris, the concept of artificial lubrication and encapsulation of the joint articulating parts has been proposed by a number of workers in recent years^1–3. This paper covers the selection of a lubricant candidate and a tribological study on both all-metal and metal/plastic combinations.     

螺栓法兰接头用碟形弹簧压缩回弹性能研究

为研究螺栓法兰接头用碟形弹簧压缩回弹性能,建立碟形弹簧力学性能分析的弹塑性有限元模型,并通过试验验证其可靠性。应用ABAQUS软件对碟形弹簧压缩回弹过程进行分析,讨论碟簧外内径比、倾角和厚度对碟簧压缩回弹性能的影响。结果表明:碟簧的压平载荷随厚度、倾角的增加呈上升趋势,随外内径比的增加呈下降趋势;回弹率随厚度、倾角、外内径比的增加均呈下降趋势。基于正交试验分析方法,结合量纲分析,建立螺栓法兰接头用碟形弹簧压平载荷和回弹曲线的预测模型,并验证其可靠性。     

碳纤维平纹机织复合材料低速冲击及冲击后压缩性能多尺度分析

构建了多尺度模型对碳纤维平纹机织复合材料低速冲击及冲击后压缩性能进行预测分析,该多尺度模型包括微观、细观和宏观模型三部分。构建“碳纤维基体”的微观代表性体积单元模型,用于预测纤维束等效力学参数。根据平纹机织复合材料内部几何构型及求得的纤维束等效力学参数,构建“纤维束基体”的细观单胞模型,并通过周期性边界条件对其施加不同的位移载荷,预测细观单胞模型的等效力学性能。基于局部均匀化方法将细观单胞模型简化为含有0°和90°单层的等效交叉层合板模型,并将其阵列扩展为宏观模型,以分析低速冲击及冲击后压缩性能。通过对比不同冲击能量下的低速冲击及冲击后压缩的试验与仿真结果,验证了模型的有效性。      

圆柱面过盈连接的应力分析

综合以往轴毂过盈连接分析中,只考虑了弹性变形的问题,在此基础上,进一步分析轴毂结构及配合过盈量对应力的影响,以及在怎样的条件下导致其发生塑性变形。根据屈瑞斯卡塑性条件,找出过盈连接由弹性变形过渡到塑性变形的条件,推导了在弹性与塑性情况下连接体内的应力计算公式,完善和丰富过盈配合的应力分析理论。计算实例分析了轴毂结构参数对许用过盈量的影响规律,并通过对毂内应力的分析,发现随着过盈量的增加,毂内塑性区变大,按弹性变形和按弹塑性变形计算的应力结果的差异变大。     

25 Cr2 Ni2 MoV钢焊接接头循环变形行为的有限元模拟与分析

以25Cr2Ni2MoV汽轮机转子钢V形平板焊接接头为研究对象,考虑不同热影响区材料与母材的弹性模量比值、坡口角度及载荷特性（包括不同应力比、平均应力和应力幅值）等因素的影响,采用大型有限元软件ABAQUS和Chaboche循环本构模型对接头的循环变形行为、局部塑性变形分布及其随循环周次的演化特性进行了有限元模拟与分析。结果表明,随着热影响区材料与母材的弹性模量比值的增大,焊接接头整体抗拉和抗棘轮变形能力增强,发生局部破坏的可能性也随之增大;随着坡口角度的增加,焊接接头的抗拉性能和抗棘轮变形能力降低;应力比、平均应力和应力幅值越大,焊接接头越容易发生破坏。研究成果实现了对平板焊接接头结构及性能的初步优化,为提高该类焊接接头的设计水平提供了参考。     

基于接触分析的气缸盖/气缸套密封性能研究

针对某160型柴油机的单体缸盖-气缸垫-气缸套密封系统,建立了装配体的有限元模型。采用接触分析法,研究了发动机功率提升前后,在预紧加爆压工况下原紧固螺栓对气缸垫密封性能的影响,并对气缸垫密封面的变形状态进行了弹塑性分析,对结构的密封性能进行了评价。结果表明,发动机功率提升后气缸垫发生了塑性屈服,但轴向应力仍均为负值(即压应力),轴向变形量亦均为负值(即压变形),说明提升功率后发动机工作过程中气缸垫仍然密封良好。较以往将气缸密封垫假设为弹性体相比,采用摩擦接触边界条件进行塑性有限元分析,更能体现缸盖与气缸垫接触面的真实应力与变形状态,因此接触分析法是研究缸盖/缸套密封结构的一种较佳途径。     

汽轮机膨胀节塑性变形损伤后结构力学性能分析

汽轮机金属膨胀节在制造、安装和运行阶段常发生塑性变形,影响其服役工况下达到设计膨胀补偿量和安全运行性能的要求。目前,核电厂关键设备主要设计参考规范(RCC-M、ASME规范第Ⅲ和ⅩⅢ卷等)正逐步发展为基于弹塑性理论的分析方法。针对某核电厂汽轮机膨胀节发生的塑性变形损伤,基于ASME规范和有限元软件ANSYS进行了膨胀节塑性变形损伤后结构力学性能分析,包含基于材料真实应力-应变数据的不同工况组合下塑性损伤分析及结构塑性损伤后疲劳寿命的校核。     

塑料光学透镜的磁悬浮检测

考虑传统的塑料透镜检测方法操作繁琐、耗时长,本文提出了一种针对小型塑料光学透镜的磁悬浮检测理论与方法,并设计制造出了相关检测装置。该方法利用磁场对顺磁溶液的磁化作用,将逆磁性被测样品(塑料透镜)在溶液中悬浮起来,通过观察透镜在装置中的高度、中心位置和平衡状态下与水平面的偏斜程度,检测透镜是否存在外观不完整和内部存在气泡等不均匀性的缺陷,并确定出透镜缺陷存在的位置。通过合格透镜、外形不完整透镜、内部存在气泡透镜和功能不合格透镜开展了多项实验研究来验证该方法的可行性与有效性。结果显示,该方法的检测精度高、灵敏度高、操作简便且适应性广,在0.5mm的测量误差下,密度的测量精度高达0.003g/cm3;对直径小于10mm的透镜,可检测出总体积在0.017mm3的内部气泡缺陷。提出的方法在塑料光学透镜的检测方面很有应用潜力。     

激光直写中S曲线光强控制模型的参数优化方法

为了进一步提高激光直写封闭线条时的对接质量,本文提出一种S曲线光强控制模型的参数优化方法。建立了S曲线光强控制模型的参数变化和线条闭合质量之间的关系,优化了光强控制函数中的圆弧弧度θ和曲率半径R,并推导了优化后的对接区域长度模型,优化后的对接区域长度可由圆弧弧度θ唯一确定。实验结果表明,本文提出的优化方法进一步增加了对接区域曝光量分布的有效过渡长度,减缓了曝光量在路径方向上的变化速率,且当圆弧弧度θ较小时,优化后的对接长度大小仅为斜线段光强控制方法的2倍,从而在保证直写效率的同时提高了线条对接质量,该方法有效地解决了激光直写中线条质量和直写效率之间的矛盾     

塑性管材测压试验排气式管端堵头的设计

介绍了一种用于塑性管材在进行测压试验时的排气式管端堵头的设计方法。这种堵头的特点是先排气后密封。在设计中运用了快换接头，整个堵头具有使用方便、排气彻底、密封牢固的效果。     

球笼式等速万向节结构轻量化设计

为了实现球笼式等速万向节的结构轻量化设计,以球笼式等速万向节最大接触应力、接触总变形和塑性变形为依据,分别对钢球数量为6和8的两种结构的球笼式等速万向节进行了初步研究.对球笼式等速万向节的主要结构尺寸即钢球中心圆直径与钢球直径之比、万向节外径与内套花键分度圆直径之比,以及球笼式等速万向节的偏心距与钢珠中心圆半径之比进行了优化选择和比较.研究结果初步表明,对于球笼式等速万向节,当钢球数量由6增加为8时,由于钢球直径的减小,不但其外形尺寸可以减小12%、质量可以减少近20%,而且万向节的承载能力反而可以得到少许提高.因此,增加球笼式等速万向节的钢球数量是实现其结构轻量化设计的一种有效方法.     

Ultrasonic based structural damage detection using combined finite element and model Lamb wave propagation parameters in composite materials

This paper presents a combined finite element and model Lamb waves propagation parameters method as a tool for structural health monitoring in composite materials. Modal analysis allows identifying the mode conversions induced by the defects. A simulation combining a lossless finite element approach and Lamb wave propagation parameter for finding natural frequencies and mode shapes of the structures in undamaged and damaged condition is proposed. This analysis is performed on two carbon-fiber-reinforced plastic bars in both undamaged and damaged state, where the two damaged states are (1) having a cut partway through the bar, perpendicular to the long axis of the bar and (2) having a circular hole. The lamb wave propagation parameters are calibrated using the ultrasonic pulse generator test setup. The natural frequencies for the theoretical, finite element and experimental results are compared and close agreement is found between the frequencies obtained experimentally and computationally.