波形套工作特性的理论与试验研究

设计与试制了不同规格的波形套试件,测试了其工作特性。建立了波形套工作状态下的数学-力学模型,求解了理论特性,并用ANSYS进行了数值模拟,理论解、模拟解与试验结果吻合。揭示了波形套的定量工作特性以及几何参数对其特性的影响规律:在最大外径不变时,随着波纹圆角半径的增大,特性曲线中弹性区的斜率增大,进入塑性变形所需要的压力亦增大;在波纹圆角半径不变时,随着波形套最大外径的增大,特性曲线中弹性变形区的斜率减小,进入塑性变形所需要的压力亦减小。波形套工作特性的理论与试验研究,为确立其设计方法,促使该类零件广泛应用奠定了基础。     

条件参数对拉伸翻管成形力的影响规律

拉伸翻管精密成形易于实现双层管零件精确、高效、灵活的制造而具有广阔的应用前景,然而拉伸翻管精密成形过程的成功实施受到变形区失稳破裂的制约,而成形力与其密切相关。因此,采用有限元数值模拟对拉伸翻管精密成形过程中成形条件参数对成形力的影响规律进行了研究,结果表明,当芯棒圆角半径大于某一值时,在整个成形过程中管坯形状基本保持不变,从而较好地实现了精确成形;对于给定的芯棒圆角半径与管坯外径之比r/d0或管坯壁厚与外径之比δ0/d0,r/δ0对成形力影响很大。并且存在着一个临界参数k,当r/δ0k时,F随着r/δ0值的增大而增大;硬化指数对成形力影响较大,硬化指数越小成形力越大,摩擦因数对成形力的影响则相对较小,而接触面良好的润滑有助于改善成形件的表面质量。     

弹性隔套轴向受压仿真与参数优化研究

针对弹性隔套结构优化设计问题,对弹性隔套进行了有限元仿真与压缩实验,对在轴向受压过程中弹性隔套轴向力-压缩量特性曲线及性能进行了研究,提出了一种基于组合优化软件Isight的隔套设计方法。通过建立正交试验组,分析了弹性隔套的结构参数对弹性隔套特性曲线斜率和最大mises应力的影响,并构造了弹性隔套特性曲线斜率和最大mises应力的二阶响应面模型;最后,利用第二代非劣遗传算法对弹性隔套的特性曲线斜率和最大mises应力的二阶响应面进行了多目标优化。研究结果表明:优化后的弹性隔套特性曲线斜率和最大mises应力的响应结果与有限元计算得到的结果相对误差均在4%以下,说明利用响应面法可近似代替有限元法对弹性隔套进行分析,计算得到的结果是可靠的;该分析方法及结果可为实际工程中轮毂单元轴承弹性隔套的设计提供参考。     

排水车三通管结构优化分析

旨在评估不同过渡圆角半径对三通管压头损失的影响。针对4种不同过渡圆角半径的三通管,采用数值模拟方法分析三通管的局部压头损失与内部流场特性。计算结果表明:随着过渡圆角半径增大,三通管压头损失逐渐减小,流体流动性能逐渐改善;弯道曲率半径R/D=0时三通管过渡处末端存在负压现象,形成二次流,局部水头损失最大;弯道曲率半径R/D=2的三通管管道具有较小的局部水头损失。     

管材弯曲最小半径

<正> 金属材料在弯曲时,其圆角区上外层受拉伸,内层受压缩,内圆半径r越小,圆角区的变形越大。当外层圆角区的拉伸应力超过材料的强度极限,外层材料发生断裂;而内层材料丧失稳定起皱,致使工件报废。据资料介绍,管材弯曲的最小弯曲半径R=3D_0 D_0:管材外径生产中需将φ48×δ2.5的拉制硬铜管弯曲成蛇形管,要求弯曲半径为76mm,内壁不起皱,外壁不开裂。根据技术要求自制弯管机试弯,发生管材外壁开裂和内壁起皱现象。经过分析和对最小弯曲半径的计算,认为原因是材料硬而塑性差,弯曲半径太小     

径向弹簧蓄能密封结构最大接触应力的有限元分析

为研究径向弹簧蓄能密封结构的密封特性，针对典型径向弹簧蓄能密封结构，分析其密封机制以及O形弯曲金属螺旋弹簧的弹性特性；采用ANSYS有限元分析软件，建立典型弹簧蓄能密封结构的非线性有限元分析模型，对弹簧蓄能密封圈在不同压缩率、不同介质压力下的接触应力进行分析，研究在多种工况下最大接触应力的变化情况。结果表明：压缩率保持不变时，最大接触应力随着介质压力的增大而增大；介质压力保持不变时，随着压缩率的增大，最大接触应力先增大再减小。对压缩率、介质压力与最大接触应力的关系进行曲线拟合，可用于指导弹簧蓄能密封结构的精确设计。     

滑片式压缩机卸荷过程的静态特性建模与仿真

为研究滑片压缩机卸荷过程的静态特性,建立了流体进入进气口及卸荷阀的流量模型。通过压力一流量特性分析发现,量纲一流量与压力成抛物线关系,并随着压力的增大而减小;通过压力增益特性分析发现,增益曲线的斜率随出口与进口流量系数的比值增大而增大;通过位移一流量特性分析发现,流量随滑柱位移的增大而增大。22kW滑片压缩机的静态特性测试验证了仿真结果。     

杂质颗粒对油水两相润滑轧机油膜轴承弹流润滑的影响

以轧机油膜轴承为研究对象,建立了油水两相流的弹流润滑模型,分析了润滑液中杂质颗粒对轧机油膜轴承润滑性能的影响。结果表明:存在杂质颗粒时,杂质颗粒接触区压力增大,入口区压力及最大压力变化不大,膜厚减小;随着杂质颗粒半径的增大,入口区压力增大,颗粒接触区压力增大,最大压力减小,膜厚减小;随着杂质颗粒浓度的增加,入口区压力减小,杂质颗粒接触区压力增大,最大压力增大,膜厚减小;随着杂质颗粒流速的增加,入口区压力及最大压力变化不大,而颗粒接触区域压力增大,膜厚减小;随着油水两相流体中含水量的增加,入口区压力减小,最大压力增大,杂质颗粒接触区压力增大,膜厚增大。     

新型等通道转角挤压模具优化设计

设计出一种新型的等通道转角挤压模具,推导出该模具下工件变形等效应变值的理论表达式,并应用3D有限元分析技术,分析了模具转角区的外倒角半径R和内倒角半径r的变化对工件变形的变形行为、应变分布和挤压所需的最大栽荷的影响.研究结果表明,R和r的增大都可以减小变形死区面积,但r影响更显著;R的增大将导致最大载荷的迅速减小,而r对其影响甚微.     

轴压翻管力及其影响因素的分析

根据金属成形理论和圆管在外翻管变形过程中，壁厚保持不变、翻管力恒定等实验现象，志出在圆角模上外翻管的翻管力Ｐ、最佳圆角半径ｒｉ的表达式，论述翻管模具半径等对翻管力的影响。确定了在轴压力作用下，圆管发生失稳，翻转、端部撕裂３种变形模式的模具半径范围。     

地铁轨道曲线半径与钢轨波磨的相关性研究

现有地铁线路钢轨波磨80%以上出现在小半径曲线轨道内股钢轨上,而大半径曲线和小半径曲线外股钢轨几乎没有出现钢轨波磨。为了探索这一现象深层次的原因,基于摩擦自激振动导致钢轨波磨的机制,分别建立Simpack车辆多体动力学曲线通过模型和轮轨系统ABAQUS有限元摩擦自激振动模型,采用复特征值分析法对不同曲线半径轨道的钢轨波磨进行研究。结果表明:随着曲线轨道半径增大,摩擦自激振动产生的概率减小,即钢轨波磨发生概率下降,且钢轨波磨主要出现在低轨上而高轨较少;随着曲线半径增大,在曲线半径400~450 m范围内,轮轨蠕滑力逐渐由饱和状态变为不饱和状态;蠕滑力饱和时轮轨系统有可能出现摩擦自激振动,即产生钢轨波磨,当蠕滑力不饱和时,轮轨系统就不会出现摩擦自激振动,因而大概率不会发生钢轨波磨。     

斜接管道结构在内压作用下塑性极限载荷的有限元分析方法研究

采用有限元方法,建立了斜接管压力容器结构在内压作用下的数值模型,并将不同载荷下管道的热点应力分布与现有文献实验结果进行了比较,两者吻合较好,验证了该计算方法的可靠性。对于正交接管利用两倍弹性斜率、切线交点和零曲率极限载荷准则获得斜接管道失效的极限内压;并将正交接管的极限内压与Cloud以最大有效应力达到屈服时对应的理论上极限内压值进行比较,结果表明：两倍弹性斜率与切线交点极限载荷准则在预测极限内压时偏于保守,零曲率准则对确定斜接管压力容器的极限载荷比较恰当。然后利用零曲率准则确定斜接管压力容器的极限载荷,采用控制单变量变化的方法,分别分析了接管中心线与简体中心的夹角、接管与筒体直径之比和筒体厚度与直径之比对极限载荷的影响,最后综合考虑这些因素的影响,得出了斜接管压力容器极限载荷的近似计算式。提供的分析方法为压力容器的设计及安全性评定提供了一种新途径。     

Deformation characteristics of corrugated composites for morphing wings

To meet the needs of morphing and withstand aerodynamic loads of a morphing wing skin, a corrugated glass fabric-epoxy laminated composite is prepared and investigated in this paper. This composite is flexible in the corrugated direction and stiff in the transverse direction to the corrugation. FEM models are established and solved to predict the characteristics of the composites by the commercial FEM software ANSYS. The relationship between the configuration of elongation and tensile load along the corrugation direction is obtained through numerical simulation. To reflect the stretching superiority of the configuration, the elongation of corrugated and flat composites is calculated and compared under the same tensile load. The linear cumulative effect of corrugated composites deformation is proved by calculating the elongation of the composites with several different corrugation numbers. Several corrugated composite specimens were manufactured and tested to verify the results of numerical analysis and the equivalent elastic modulus of the composites were also evaluated through the specimen tests. Results of simulation and experiments show that the corrugated composite provided in this paper can afford obviously larger deformation than the flat one. The corrugated composite can provide a possible choice for morphing wing skin.     

Probing model tumor interfacial properties using piezoelectric cantilevers

Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G/E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The piezoelectric cantilever used had two lead zirconate titanate layers to facilitate all-electrical elastic (shear) modulus measurements using one single device. We constructed model tissues with tumors by embedding one-dimensional (1D) corrugated inclusions and three-dimensional (3D) spiky-ball inclusions made of modeling clay in gelatin. We showed that for smooth inclusions, G/E was 0.3 regardless of the shear direction. In contrast, for a 1D corrugated rough inclusion G/E was 0.3 only when the shear was parallel to corrugation and G/E increased with an increasing angle between the shear direction and the corrugation. When the shear was perpendicular to corrugation, G/E became >0.7. For 3D isotropic spiky-ball inclusions we showed that the G/E depended on the degree of the roughness. Using the ratio s/r of the spike length (s) to the overall inclusion radius (r) as a roughness parameter, we showed that for inclusions with s/r larger than or equal to 0.28, the G/E ratio over the inclusions was larger than 0.7 whereas for inclusions with s/r less than 0.28, the G/E decreased with decreasing s/r to around 0.3 at s/r=0. In addition, we showed that the depth limit of the G/E measurement is twice the width of the probe area of the piezoelectric cantilever.     

防止承压设备总体塑性变形的5%最大主应变准则

提出了按5%应变确定塑性载荷的最大主应变准则。该准则可以用来防止承压设备的总体塑性变形。5%最大主应变准则只需要经过弹塑性分析,求出承压设备在载荷作用下产生的最大主应变,当最大主应变达到5%时,作用在承压设备上的载荷就是塑性载荷。与其它已有确定塑性载荷的准则相比较,5%最大主应变准则不需要预先画出载荷—变形(应变)曲线,因而,就不需要选择变形参数(选择变形点的位移,或者容器体积的变化等)。例子分析给出了5%最大主应变得到的塑性载荷,并与应力分类方法、两倍弹性斜率准则和双切线准则作了比较。     

Deformation characteristics of corrugated composites for morphing wings

To meet the needs of morphing and withstand aerodynamic loads of a morphing wing skin, a corrugated glass fabric-epoxy laminated composite is prepared and investigated in this paper. This composite is flexible in the corrugated direction and stiff in the transverse direction to the corrugation. FEM models are established and solved to predict the characteristics of the composites by the commercial FEM software ANSYS. The relationship between the configuration of elongation and tensile load along the corrugation direction is obtained through numerical simulation. To reflect the stretching superiority of the configuration, the elongation of corrugated and flat composites is calculated and compared under the same tensile load. The linear cumulative effect of corrugated composites deformation is proved by calculating the elongation of the composites with several different corrugation numbers. Several corrugated composite specimens were manufactured and tested to verify the results of numerical analysis and the equivalent elastic modulus of the composites were also evaluated through the specimen tests. Results of simulation and experiments show that the corrugated composite provided in this paper can afford obviously larger deformation than the flat one. The corrugated composite can provide a possible choice for morphing wing skin.     

柔性石墨波齿复合垫片结构性能试验研究

在有限元应力分析[1]的基础上,对不同结构参数的柔性石墨金属波齿复合垫片进行压缩回弹性能试验.结果表明:在45 MPa的压紧力和相同密封面宽度及一定波齿深度的条件下,压缩率随波齿数的增加而减小(即随波齿圆弧半径的减小而减小),回弹率则相对增大,这一结果与弹性有限元应力分析结果基本一致.     

基于LMTO算法磁记忆屈服信号的定量化分析

磁记忆法对铁磁性金属构件的应力集中区域具有很好检测效果。但是,目前构件在弹性阶段和塑性阶段的磁记忆信号特征很难被区分,从而无法对构件的应力集中程度和使用寿命进行有效评估。基于固体电子理论建立了磁记忆效应的边界滑移模型,利用线性化M-T轨道算法(LMTO)计算了固体在弹性、塑性阶段,系统的能量变化、不同轨道电子的自旋态密度的变化情况,进而定量分析了构件发生屈服后的磁记忆信号变化规律。研究结果表明,应力集中程度与系统边界滑移能量呈线性正比例关系,与电子自旋态密度峰峰值、磁记忆信号呈线性反比例关系;构件发生塑性形变后,体系能量和电子自旋发生不可逆的变化,磁记忆信号曲线出现转折点;构件每发生一次塑性变形,磁记忆信号初始值都会变小,曲线斜率变小。     

Study on the Effect of Track Curve Radius on Friction-Induced Oscillation of a Wheelset–Track System

Abstract

The purpose of this article is to investigate the correlation between the friction-induced oscillation of a wheelset–track system and curve radius and to explain a general phenomenon of rail corrugation based on the viewpoint of friction-induced oscillation. The typical phenomenon of rail corrugation in metros is that corrugation generally arises when the curve radius is quite small, whereas it rarely occurs when the curve radius is larger or on a straight track. Different multibody models of the vehicle–track system and finite-element models of the multiple-wheelset–track system with different curve radii are established, respectively. According to the creep force analyses and unstable vibration analyses, the correlation between the creep force and friction-induced oscillation can be identified. Then the effect of the track curve radius on the friction-induced oscillation of the wheelset–track system can be summarized, which provides an explanation of the typical phenomenon of corrugation.