Friction in femoral prosthesis and photoelastic model cone taper joints

Static axial push-on and lift-off, and push-on and twist-off experiments were designed and performed to measure the effective, room-temperature coefficient of friction mu for different design femoral prosthesis cone taper joints comprising a universal head on a stem spigot. Alumina and metal heads were tested on metal spigots using either distilled water, Ringer's solution, blood or no lubricant. Complementary push-on and lift-off friction tests of Araldite model joints for subsequent frozen-stress, photoelastic stress analysis were performed at 130 degrees C. It was found that lubricant caused little decrease in the values of the coefficient of friction in prosthesis tapers. The values measured were typically mu = 0.2 for an alumina head on a Co-Cr-Mo or Ti-6Al-4V spigot, mu = 0.15 for a Co-Cr-Mo head on a Co-Cr-Mo or Ti-6Al-4V spigot and mu = 0.13 for a stainless steel head on a stainless steel spigot. For Araldite photoelastic models of an alumina head on a Vitallium spigot, as-cast taper surfaces lubricated with silicone grease gave consistent friction of typically mu = 0.14. The axial displacement of model heads on their spigots were compared with predicted values and previously measured values for prosthesis heads.     

Structural analysis and testing of a miniature flexible joint under pressure and vector loading

The structural characteristics of a miniature tactical motor flexible joint subjected to pressure and vector loading were investigated using finite element analysis and bench test. Three-dimensional non-linear finite element analysis was conducted using ANSYS Code Version 11.0. The axial deflection, vectoring torque, and stress distributions in elastomeric and reinforcement rings were presented. The predicted values were consistent with the test data. Results indicate that the axial compressive stiffness increased gradually and nonlinearly with pressure, while the angular stiffness remained nearly constant in the vectoring angle range from 0° to 6°. Under pressure loading, the elastomeric shear stress was negative, high at both sides, and low at the center of the cross-section, while the reinforcement hoop stress was compressive at the inner radius and tensile at the outer radius. The compressive stress was also high. The flexible joint exhibited higher stress level with altered stress distribution when subjected to additional vector loading. Existing empirical formulas for reinforcement hoop compressive stress were determined to be not applicable to the miniature flexible joint, which significantly overestimated the stress caused by pressure and underestimated the stress caused by vectoring.     

截割头几何因素影响下的巷道表面形貌特征与建模

考虑到纵轴式掘进机截割头运动轨迹直接影响巷道成形表面形貌特征,分析了截割头截割巷道得到的巷道外轮廓的创成机理,运用机器人运动学分析方法确定掘进机截割头在巷道空间坐标系内的坐标,构建截割头截割巷道外轮廓的数学模型;通过数值计算分析截割进给量、截割角度、截割头形状、截割头半径及截割头锥角等参数对截割表面形貌特征的影响规律。研究结果表明：“球冠+圆柱”式截割头截割得到的巷道表面最不平整,“球冠+圆锥+圆柱”式截割头截割得到的巷道表面最为平整;随着截割升降角度和截割进给量的减小、截割头球冠半径和截割头圆锥角的增大,截割得到的巷道平整度提高;截割升降角度越大,越需要对巷道平整度进行精确控制。     

深孔内轮廓尺寸光学测量系统

针对深孔类零件对内轮廓尺寸的检测要求较高,而目前所采用的测量方法不是分辨率太低就是测量效率较低的问题,研究了一种用于深孔内轮廓尺寸的光学测量系统,该系统主要由环形激光发生器、扩束锥镜、成像锥镜和CCD相机组成。环形激光发生器发出的环形激光照射到扩束锥镜上,经反射后投影到深孔内轮廓某断面处形成一个环形光斑,该环形光斑的形状反映了深孔内轮廓某一处断面的形貌,并经过扩束锥镜反射后在CCD相机的光敏面上成像,经过处理和计算可以得到深孔内轮廓的尺寸。试验证明,该系统可以有效快速地实现对深孔内轮廓尺寸的测量,并能够保证较高的测量精度,在改善误差影响因素和采取相应的误差补偿办法后,可以进一步提高测量精度。     

旋转控制头密封胶芯性能三维有限元分析与结构优化

为提升带压起下钻过程中旋转控制头胶芯密封性能,基于虚功原理得到动态密封过程的有限元控制方程,并进行橡胶单轴压缩试验确立胶芯变形过程中的Yeoh本构模型;运用ABAQUS试验平台建立胶芯三维有限元模型,通过模拟起下钻过程中胶芯动态密封过程,得出密封面上受力分布规律;研究胶芯内锥角、外锥角、内径等结构参数对密封性能的影响....     

多层压配组合冷挤压凹模和高压容器的优化设计

本文对多层压配冷挤压凹模和高压容器的应力和应变以及优化设计的原理进行了系统的论述。优化条件分为：（一）内圈内壁在工作内压作用下允许出现拉应力和（二）内圈内壁在工作内压作用下不出现拉应力两种情况。文章提出根据所选材料和工作内压来确定各层组合圈壁厚和过盈量的计算公式。     

膨胀管实体膨胀锥受力分析与膨胀试验验证

膨胀管技术主要应用在油气田开发领域,膨胀锥是膨胀管技术主要工具之一,在工作时受到极大的界面应力,因此膨胀锥表面过快磨损是制约膨胀管技术发展的主要问题之一。为探究膨胀过程中膨胀锥体表面受力和应力分布,结合弹塑性理论推导膨胀锥接触应力和摩擦力计算模型,采用有限元方法模拟膨胀管膨胀过程,研究膨胀锥表面应力、接触摩擦应力和膨胀推力变化情况,并通过膨胀试验验证了有限元模拟结果的合理性。结果表明：影响膨胀锥接触应力和摩擦力的主要因素是膨胀管屈服强度和膨胀锥锥角;膨胀锥的最大等效应力集中在大径圆角处,最大摩擦应力集中在膨胀锥小径和大径处;膨胀锥膨胀区只有部分与膨胀管内壁接触,膨胀锥小径处受拉应力,大径处受压应力,最大接触压应力集中在大径处。     

Shape control of near-field probes using dynamic meniscus etching

Dynamic etching methods for fabricating fibre optic tips are explored and modelled. By vertically translating the fibre during etching by an HF solution under an organic protective layer, a variety of tip shapes were created. The probe taper lengths, cone angles and geometrical probe shapes were measured in order to evaluate the dynamic meniscus etching process. Fibre motion, etching rate, meniscus distortion and etching time were all found to be important variables that can be used to control the final probe shape.     

圆锥滚子超精研导辊的精确辊形及其磨削分析

确定了圆锥滚子超精研导辊的精确辊形,并进行了数值分析,结果表明,辊形锥角对滚子锥角最敏感,对接触角较敏感,对滚子直径不敏感;辊形凹度对滚子锥角较敏感,对接触角和滚子直径均不敏感。提出了导辊磨削辊形表达式并进行了数值分析,分析表明砂轮半锥角和砂轮架垂直摆角是两个关键参数,对其合理取值可实现辊形精确磨削;给出的分析实例中,在0.1μm精度范围,内磨削辊形与精确辊形相同。     

On high explosive launching of projectiles for shock physics experiments

The hydrodynamic operation of the "Forest Flyer" type of explosive launching system for shock physics projectiles was investigated in detail using one and two dimensional continuum dynamics simulations. The simulations were numerically converged and insensitive to uncertainties in the material properties; they reproduced the speed of the projectile and the shape of its rear surface. The most commonly used variant, with an Al alloy case, was predicted to produce a slightly curved projectile, subjected to some shock heating and likely exhibiting some porosity from tensile damage. The curvature is caused by a shock reflected from the case; tensile damage is caused by the interaction of the Taylor wave pressure profile from the detonation wave with the free surface of the projectile. The simulations gave only an indication of tensile damage in the projectile, as damage is not understood well enough for predictions in this loading regime. The flatness can be improved by using a case of lower shock impedance, such as polymethyl methacrylate. High-impedance cases, including Al alloys but with denser materials improving the launching efficiency, can be used if designed according to the physics of oblique shock reflection, which indicates an appropriate case taper for any combination of explosive and case material. The tensile stress induced in the projectile depends on the relative thickness of the explosive, expansion gap, and projectile. The thinner the projectile with respect to the explosive, the smaller the tensile stress. Thus if the explosive is initiated with a plane wave lens, the tensile stress is lower than that for initiation with multiple detonators over a plane. The previous plane wave lens designs did, however, induce a tensile stress close to the spall strength of the projectile. The tensile stress can be reduced by changes in the component thicknesses. Experiments verifying the operation of explosively launched projectiles should attempt to measure porosity induced in the projectile: arrival time measurements are likely to be insensitive to porous regions caused by damaged or recollected material.     

准双曲面齿轮的修正节锥设计方法及切齿试验

为了提高准双曲面齿轮的强度和耐磨性,提高准双曲面齿轮的使用寿命,提出准双曲面齿轮的修正节锥设计方法。在不改变大轮外径和中点工作齿高的的情况下,令大轮的齿顶高系数fa≤ ,从而可以导出新的节锥参数,此时新的节锥与面锥重合或在准双曲面齿轮实体之外。利用齿面接触分析(TCA)、齿面承载接触分析(LTCA)和有限元法(FEM),分析齿轮副的啮合性态、齿面接触应力、齿根最大拉伸应力和齿根最大压缩应力。计算机模拟显示,采用修正节锥设计方法设计的准双曲面齿轮的齿面接触应力、齿根最大拉伸应力和齿根最大压缩应力显著减少,采用修正节锥设计方法设计的准双曲面齿轮在加工过程中可用一般的刀具,不需要特殊的工具。     

Friction in orthopaedic zirconia taper assemblies

The torque resistance of zirconia ceramic heads/titanium taper trunnion junctions was tested in accordance with ISO 7206-9:1994(E); using twelve modified heads of 32 mm diameter under representative physiological conditions. Test parameters studied included assembly force, vertical load during test (test load) and head length. Mean torque resistances measured were 8.9 N m for a 1 kN test load and 15 N m at 4 kN test load. Coefficients of friction calculated for the torsional stability ranged from 0.06 to greater than 1.0. Multiple regression analysis confirmed that the failure torques measured were significantly dependent on test load (beta = 0.77; P < 0.001) whereas assembly force and head length played a lesser, insignificant, part in the variation. Data from push-on/pull-off tests were used to calculate coefficients of friction under axial loading, which were significantly correlated with taper angle and material. Torque testing shows greater variability than push-on/pull-off tests for similar combinations, and for zirconia heads on other tapers. The coefficients of friction measured (0.16-0.31) are significantly different from values typically used in stress analyses.     

钢丝缠绕予应力高压容器和冷挤压凹模在内压作用下内壁不出现拉应力的设计原理

钢丝或钢带缠绕予以应力高压容器或模具由芯筒和缠绕层两部分组成。缠绕层采用等剪应力方法充分利用了钢丝的强度,比采用等张或等切应力方法能承载更大的工作内压。芯筒多采用高强材料。为使芯筒不易开裂并提高疲劳寿命,要求在工作内压载荷下内壁不出现拉应力。本文提出满足这一要求的最佳设计方法和计算公式。     

锥套装置的设计及应用分析

为提高机械传动联接部件的定心精度及在重载、冲击性载荷作用下不会产生切键现象,设计制造了锥套装置,锥套外锥面与锥孔内锥面与轴线均呈4°夹角。安装后,在锥孔锥面的作用下,锥套将产生形变而夹紧锥套轴孔内的传动轴。     

Shape control in micro borehole generation by EMM with the assistance of vibration of tool

Electrochemical micromachining (EMM) is gaining importance day by day due its advantages that include no tool wear, absence of stress/burr, high MRR, bright surface finish and ability to machine complex shapes regardless of hardness. Overcut and taper formation is the main problem during micro borehole machining. In this paper, an electrical circuit model of EMM is presented for better understanding of the process and experimental MRR is found to be in good agreement with theoretical MRR. In the present set up variation of overcut with voltage, pulsed frequency, vibration amplitude of tool and vibration frequency of tool are investigated. To reduce overcut and taper angle of micro borehole, machining zone is simulated with a reversed taper tool and verified by practical experiments for proper shape control during micro borehole generation. Variation of micro nozzle angle with different feed rates and different times of machining are also investigated for the shape control during micromachining with conical tool. Finally, it has been shown that both reversed taper and forward taper tool can be used for generation of taper less micro features i.e. boreholes.     

后锥角对串联空化腔室的空化特性的数值研究

针对串联式空化腔室的空化强度和效率存在的问题,展开了对其影响较大的后锥角β值的数值研究,为今后的空化腔室设计提供理论依据。采用Mixture多相流模型,以及k-?两方程湍流模型,在Fluent软件中仿真模拟后锥角β值连续变化的多种串联空化腔室流体域模型,抽取分析计算结果中的压力,速度及空泡体积分数的云图,进而研究后锥形角β值对空化流场的影响。研究结果表明:在后锥形角β值取15?附近能够获得强度相对较高的空化现象;产生空泡体积的大小、负压力的区域大小以及沿中轴线维持恒定速度的能力三者成正相关关系;后锥角β值直接影响着空化流场的分布情况,决定着最终喷射到工件表面的作用范围。     

高压聚乙烯反应管自增强残余应力的无损检测

针对超高压聚乙烯反应管内径小,壁厚大,内部介质压力为超高压等特点,。开发出一套管内壁应变片粘贴装置和引线密封装置,从而保证了内压达550MPa以上时应变片及引线的密封与绝缘性,基于内壁应变－压力关系曲线与残余应力之间的对应关系,成功地测取了反应管内壁残余应力。本方法可推广应用于小管径管道内壁应变和自增强残余应力的测试。     

正弦规测量内、外锥直径尺寸公式的建立与分析

<正>弦规一般用于测量外锥面的角度,将其用于测量外锥体和内锥孔的直径值,是正弦规的一种扩大使用技术。本文建立了一套公式,对外锥体和内锥孔的直径值进行分析并用正弦规进行实践性测量,可保证锥套配合直径尺寸的测量精度。     

圆锥滚子定姿态贯穿式超精研凸度形成机理分析

圆锥滚子无心贯穿式超精研中,滚子以某种定姿态沿直线贯穿时,在锥面上可以形成一种大致对称的光滑曲线凸度,其凸度形成机理尚未揭示。针对滚子轴线只在贯穿方向铅垂平面倾斜某一固定角度这种定姿态,基于超精研工艺特性及滚子与油石之间的几何和相对运动关系,建立滚子-油石接触线方程和滚子纵向截形方程,推导出各超精研区宽度计算公式。将这种超精研过程看作滚子与油石的接触磨损过程,将凸度看作滚子不均匀磨损的结果,依据磨损基本原理,揭示出凸度形成机理：滚子-油石接触线呈“几”字形,形成8个不同的超精研区,使滚子两端磨损量大于中部;接触线各点的滚子纵向截形倾斜程度存在差异,使滚子磨损深度从两端向中部逐渐非线性减小,从而形成光滑曲线凸度。得出如下结论：只有滚子上素线小端向上倾斜某一适当角度时,才可以形成比较对称的曲线凸度;滚子锥角是基础,其值不为零才能形成凸度;所能形成的最大凸度受锥角大小制约,锥角越大,所能形成的凸度越大。推导出滚子上素线小端向上适当倾斜角度范围的计算公式。     

Calibration of hoop stress in ring tensile test with Zircaloy-4 tube

Since Zirconium (Zr) alloys have been widely used as cladding material in a nuclear fuel rod, material properties of Zr are essential in prediction of failure and undesirable deformation. This paper mainly concerns calibration procedure to obtain the hoop stress of Zircaloy-4 tube with a simple ring tensile (RTT) test linking with a Digital image correlation (DIC) technique since it is substantially difficult to obtain, directly, with specialized experiment such as burst test with internal pressure. The uniaxial tensile tests along the axial and RTT along the hoop directions were conducted with Zircaloy-4 tube in which anisotropic stains were analyzed with a DIC technique to validate appropriate deformation history. Anisotropic yield criterion based on the measured R-values (R _θ = 1.88 and R _z = 0.814) is able to capture the precise deformation mode in the ring tensile test. The flow curve along the hoop direction is calibrated by converting F, G, and H material parameters based on the R-values to the function of stress ratios.