颗粒接触摩擦系数空间变异性对颗粒流双轴数值试验的影响

提出了考虑颗粒摩擦系数空间变异性的砂土双轴剪切响应分析方法。采用随机场模型表征颗粒摩擦系数空间变异性,通过Karhunen-Loève展开方法离散接触摩擦系数随机场,编写了基于颗粒流程序PFC2D和MATLAB的随机模拟耦合分析程序。研究了摩擦系数空间变异性对密砂试样的双轴剪切响应影响规律。结果表明:1)提出方法可有效地考虑颗粒间接触摩擦系数变异性对土体材料双轴压缩宏观力学行为影响;2)密砂试样在剪切过程中的应力-应变关系曲线、体积-应变关系曲线的变化规律与颗粒间接触摩擦系数不确定性密切相关,在初始加载阶段随机模拟的偏应力曲线、体积应变曲线基本重合,继续加载后曲线开始发散;3)垂直相关距离对峰值偏应力均值与标准差影响明显大于水平相关距离。颗粒接触摩擦系数的均值对峰值偏应力的影响大于摩擦系数空间分布的影响。摩擦系数的空间分布会影响剪切带的形成位置。

摩擦系数对5083铝合金热压缩试验变形行为影响的有限元模拟研究

在热模拟试验机上对5083铝合金进行热压缩试验,并利用有限元分析软件DEFOM-3D研究了不同接触摩擦系数0、0.2、0.4和0.6对5083铝合金在热压缩试验中的试样形态、载荷力、应变速率以及应变分布的影响规律。研究表明:接触摩擦系数对载荷力基本没有影响,但对应变速率和应变的分布影响显著,随着接触摩擦系数的增加,变形不均匀性增大,应变速率和应变量从试样两端面到心部逐渐增大,且接触摩擦系数越大,鼓肚现象越明显。

考虑摩擦接触的沥青路面坑槽补缝处力学响应研究

为了给沥青路面坑槽结构修补设计提供科学的理论支持,针对坑槽补缝处力学响应的影响因素修补厚度和修补料与原路面材料的模量比,采用Goodman零厚度单元模型,运用非线性有限元软件ABAQUS计算了不同修补厚度、不同模量比与荷载耦合作用下补缝处的力学响应,分析了补缝处力学指标随接触摩擦系数的变化规律.研究结果表明:不同接触模型对补缝最大拉应力和最大剪应力计算结果影响较大;不同修补厚度和模量比条件下,横缝最大拉应力无显著变化;而纵缝处,一定修补厚度和模量比条件下最大拉应力出现峰值,且由顶部到底部呈先减小后增大趋势,各补缝处最大剪应力关系是纵缝顶部>补块表面>橫缝底部,模量比为0.5时出现峰值0.32MPa.

桥梁结构地震响应的接触效应及影响因素分析

为研究桥梁上部结构关键部位界面接触效应及其对结构的地震响应影响规律,基于接触面对法建立了非线性地震响应分析模型,利用ANSYS进行数值计算,对Goodman单元的切向与法向刚度进行率定,通过模型的位移云图及相对位移时程以及从地震动峰值加速度、材料的弹性模量、接触摩擦系数3个方面以接触面滑移距离为评价指标进行分析。结果表明:相对位移的总体趋势为先增大后减小至零,大小变化随时间无明显规律;接触面滑移程度随着地震动峰值加速度的增大而逐渐增大,随着材料弹性模量的增大而呈线性变小,随着接触界面摩擦系数的增大而逐渐减小。

Effect of flank angle and friction coefficient on contact stress of turbine rotor

In order to simulate the stress of turbine rotor in aeroengine, based on the ANSYS, the simplification model of the turbine rotor was built up. By applying the simplification model, the contact stress of turbine rotor was computed. The maximum contact stress appears at the chamfer below the flank, which agrees with experiment result. At the same time, the contact stress changing with the flank angle and friction coefficient was calculated, The results show that the contact stress in the flank increases slowly with the increase of flank angle; with the friction coefficient increasing, the contact stress in flank length decreases; the contact stress will not change when the friction coefficient is over 0.25.

Friction Characteristics of Space Lubricating Oil No.4129 in Rolling and Sliding Contact

The friction coefficients between the surfaces of a ball and a disc lubricated by a space lubricating oil No.4129 were measured at various operating conditions on a ball-disc friction test rig. Friction characteristic curves were obtained under sliding and rolling movements at point contact. A new model for calculation of the friction coefficient was presented. The results show that the bigger the load is, the larger the friction coefficient becomes. The rolling speed ranging from 1 m/s to10 m/s has an important effect on the friction coefficient. The friction coefficient increases with the increase in sliding speed and the decrease in rolling speed. The linear variation region of the friction coefficient versus the sliding speed at high rolling speed is wider than that at low rolling speed. The model for calculation of the friction coefficient is accurate for engineering use.

Research on stress distribution between wires of single thigh steel strand

A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.

Wear and Contact Temperature on Steel Surface in Linear Dry Friction Contact with Polimers with SGF

In this paper, we tried to present a qualitative correlation, based on extensive experimental trials between the value and the evolution of the friction coefficient, wear and contact temperature in the case of linear dry contact, thermoplastic material reinforced with SGF （short glass fibres） and various steel surfaces. We tried, believing successfully, the graphic illustration of the evolution of the steel surface wear and of the contact temperature, depending on the friction coefficient. It was analyzed in detail the influence of the normal load and sliding speed, but also of the metallic surface roughness on the friction coefficient.

枪弹穿甲过程仿真的有限元接触模型与分区并行计算误差特性

为了提高小口径普通钢芯弹和穿甲燃烧弹侵彻均质钢靶板的仿真分析精度,分析了接触力罚函数算法的接触刚度参数和接触摩擦系数对弹道极限速度计算值的影响,分析了通过不同的并行计算系统得到的弹道极限速度计算值的差异及其统计规律。研究结果表明:多部件间的接触力罚函数的接触刚度参数分别设置与优化方法可以提高弹道极限速度值的计算精度;接触摩擦系数的不同设置值对穿甲燃烧弹侵彻较厚靶板的弹道极限速度计算值有显著影响,需探索多部件间的接触摩擦系数的准确定义方法;由于分区并行计算过程中多个区域的数据交换及参与计算的顺序的随机变化会导致计算结果的不一致,并行计算的弹道极限速度值存在离散性,需在同一入射速度下进行多次重复计算,并基于统计分析确定可靠的弹道极限速度值。