FEM analyses of stress and deformation of a flexible inner pressure bolt

The flexible inner pressure bolt is a new kind and new structural bolt (anchor rod). A number of structural improvements and performance test have been carried out. The bolt has superior compatibility to the soft crag and the large distortion tunnel with its flexibility. In order to study its stress, deformation and interaction mechanism thoroughly, a number of large distortion calcula- tions and analyses have been carried out on the bolt by FEM (finite element method), especially with the ANSYS software, based on the updated Lagrangian law. The results show that the maximum stress of the inner wall of the bolt is consistent with an elastic analytic solution. The maximum stress on the body occurs in the vicinity of the enhancement material. The link enhancement of the body seems to be quite essential. The experimental results indicate that the maximum injection pressure in the bolt is 2.5 MPa without link enhancement and 8.3 MPa with the enhancement. This link enhancement effect is highly significant. These results provide some basis for the design, application and anchoring stress analysis of the bolt.

An Experimental Study on Distribution of Vertical Stress in a Silo with a Central Inner Downcomer

The distribution of vertical stress for both active and passive state in the silo with a central innerdowncomer is reported in this paper. Experimental measurement of the axial distribution of vertical stress for bothactive and passive state in the silo are in good agreement with that predicted by theoretical analysis. The meanaxial stress is reduced due to the presence of the inner downcomer in the silo.

Stress characteristics of surrounding rocks for inner water exosmosis in high-pressure hydraulic tunnels

Seepage and stress redistribution are the main factors affecting the stability of surrounding rock in high-pressure hydraulic tunnels.In this work,the effects of the seepage field were firstly simplified as a seepage factor acting on the stress field,and the equilibrium equation of high pressure inner water exosmosis was established based on physical theory.Then,the plane strain theory was used to solve the problem of elasticity,and the analytic expression of surrounding rock stress was obtained.On the basis of criterion of Norway,the influences of seepage,pore water pressure and buried depth on the characteristics of the stress distribution of surrounding rocks were studied.The analyses show that the first water-filling plays a decisive role in the stability of the surrounding rock; the influence of seepage on the stress field around the tunnel is the greatest,and the change of the seepage factor is approximately consistent with the logarithm divergence.With the effects of the rock pore water pressure,the circumferential stress shows the exchange between large and small,but the radial stress does not.Increasing the buried depth can enhance the arching effect of the surrounding rock,thus improving the stability.

Study on Eco-environmental Stress Trend of Inner Mongolia Based on Ecological Stress Index

[Objective] The study aimed to analyze the eco-environrnental stress trend of Inner Mongolia using ecological stress index method. [Methed] On the basis of the improved ecological stress index （ESI） analysis method, the eco-environmental stress trend of Inner Mongolia from 1996 to 2009 was analyzed, as well as the changes of eco-environmental stress in major industrial cities of Inner Mongolia in 2008. [ Result] With the economic development of Inner Mongolia from 1996 to 2009, the U-shape change could be found in the eco-environmental stress, showing an upward trend on the whole, especially since 2003, and there was a sharp raise in the environmental pollution index. In addition, the eco-enviren- mental stress lessened in most major cities of Inner Mongolian in 2008, but it was in a polarization state, that is, Baotou, Wuhai and Hohhot biased resource and energy consumption, while Ordos and Chifeng biased environmental pollution. [ Conclusion] The research could provide scientific ref- erences for the protection of ecological environment and the adjustment of industrial structure in Inner Mongolia.

聚乙醇酸退火工艺研究

聚乙醇酸(PGA)热加工过程中,因冷却速率过快而存在内应力,需要进行退火处理,本文研究了退火温度对PGA性能的影响。采用差示扫描量热仪(DSC)和热台偏光显微镜(POM)研究了PGA的冷结晶性及结晶结构,采用X射线衍射仪(XRD)、DSC和万能材料试验机研究了不同退火温度对PGA的结晶性、热性能及力学性能的影响。实验结果表明,PGA在熔融冷却过程中先形成针状晶核,并逐渐成长为球晶,且随着降温速率的增加,冷结晶温度降低,结晶时长变短。随退火温度的升高,PGA的松弛峰值温度升高,松弛焓增大,应变减小,弹性模量增大,结晶度和应力先增大后减小。

圆柱滚子轴承滚子对数修形优化研究

为了提高轴承的疲劳寿命,采用Romax Designer工程分析软件,在充分考虑径向游隙和内外圈相对倾斜量(影响轴承寿命的主要因素)对修形效果影响的基础上,对某大兆瓦风电机组齿轮箱输出轴轴承进行了对数修形优化分析。首先,对国际标准ISO/TS 16281寿命计算方法进行了简要分析;然后,对不同径向游隙情况下对数修形的效果进行了分析;最后,对不同内外圈相对倾斜量情况下对数修形的效果进行了分析。研究结果表明:以轴承最大接触应力最小为优化目标和以国际标准ISO/TS 16281寿命最长为优化目标的轴承对数修形,其最佳修形量不同,相应的ISO/TS 16281寿命有很大不同;在该轴承的具体条件下,以ISO/TS 16281寿命最长为优化目标的最佳修形凸度量对应的ISO/TS 16281寿命比以最大接触应力最小为优化目标的最佳修形凸度量对应的ISO/TS 16281寿命长2.39%~10.63%;以ISO/TS 16281寿命最长为优化目标的最佳修形凸度量对应的ISO/TS 16281寿命比未修形的ISO/TS 16281寿命长111.47%~1054.88%,建议以ISO/TS 16281寿命最长为优化目标对轴承进行修形优化设计。该研究结果可为滚子类轴承的优化设计提供参考。

内外圈相对倾斜对圆柱滚子轴承寿命的影响

采用Romax Designer工程分析软件对某大兆瓦风电机组齿轮箱进行整体建模,应用经典滚动轴承理论和“切片法”基本思想,对齿轮箱输出轴圆柱滚子轴承在不同内外圈相对倾斜情况下的接触应力、修形效果和轴承寿命进行大量分析计算;重点对轴承ISO/TS 16281寿命进行分析,分析内外圈相对倾斜量对ISO/TS 16281寿命的影响以及对未修形和对数修形最佳修形凸度量时两种情况下寿命的影响;还将ISO 281寿命和ISO/TS 16281寿命进行对比。研究结果表明,无论轴承是否修形,内外圈相对倾斜对轴承ISO/TS 16281寿命影响非常大,倾斜量越大,ISO/TS 16281寿命越短,对应的最佳修形凸度量越大,相应修形效果越好,ISO/TS 16281:2008额定寿命提高得越大;在内外圈相对倾斜量相同的情况下,ISO/TS 16281寿命与ISO281寿命相差非常大。研究结果可为圆柱滚子轴承优化设计提供参考。

Numerical Simulation of the Whole Three-Dimensional Flow in a Stirred Tank with Anisotropic Algebraic Stress Model

In accordance to the anisotropic feature of turbulent flow, an anisotropic algebraic stress model is adopted to predict the turbulent flow field and turbulent characteristics generated by a Rushton disc turbine with the improved inner-outer iterative procedure. The predicted turbulent flow is compared with experimental data and the simulation by the standard κ-ε turbulence model. The anisotropic algebraic stress model is found to give better prediction than the standard κ-ε turbulence model. The predicted turbulent flow field is in accordance to experimental data and the trend of the turbulence intensity can be effectively reflected in the simulation. The distribution of turbulent shear rate in the stirred tanks was simulated with the established numerical procedure.

STRESS RATE INTEGRAL EQUATIONS OF ELASTOPLASTICITY

The stress rate integral equations of elastoplasticity are deduced based on Ref. [1] by consistent methods. The point at which the stresses and/or displacements are calculated can be in the body or on the boundary, and in the plastic region or elastic one. The existence of the principal value integral in the plastic region is demonstrated strictly, and the theoretical basis is presented for the paticular solution method by unit initial stress fields. In the present method, programming is easy and general, and the numerical results are excellent.

The principle of stability control of surrounding rock-bearing structures in high stress soft rock roadways

Through the description of the deformational features of the surrounding rockaround high stress engineering soft rock roadways,the coupling stabilization principle ofinner and outer structures in surrounding rock was put forward.The supporting principlesof high stress engineering soft rock roadway (high resistance and yielding support,timelysupport,high strength and high stiffness supports) were proposed,which were applied inengineering practices,and obtained better achievements.

Base Stress of the Opened Bottom Cylinder Structures

The base stress of the opened bottom cylinder structure differs greatly from that of the structure with a closed bottom. By investigating the inner soil pressure on the cylinder wall and the base stress of the cylinder base, which were obtained from the model experiments, the interactions among the filler inside the cylinder, subsoil and cylinder are analyzed. The adjusting mechanism of frictional resistance between the inner filler and the wall of the cylinder during the overturning of the cylinder is discussed. Based on the experimental study, a method for calculating the base stress of the opened bottom cylinder structure is proposed. Meanwhile, the formulas for calculating the effective anti-overturning ratio of the opened bottom cylinder are derived.

深基坑开挖与内支撑调节对邻近沉井影响规律试验研究

为了探明基坑开挖以及内支撑伸缩调控下基坑与邻近沉井受力特性变化规律,采用室内“基坑-沉井”模型试验,研究了沉井侧壁土压力、内力、周边地表沉降、墙背土压力等变化规律。结果表明:基坑开挖过程中,墙背土压力减小,沉井侧壁水平弯矩由正转负,最大弯矩值位置随开挖深度的增大逐渐下移,周边地表沉降呈三角形分布;内支撑伸缩调节时,当前支撑深度附近墙背土压力受到的影响最明显,调节第3道支撑时局部土压力变化率最大,调节第4道支撑时局部土压力值达到最大值;多道支撑同时调节综合影响范围大于单支撑调节;支撑伸缩可能造成沉井发生一定转动,对靠近基坑侧沉井侧壁土压力影响大于远离基坑一侧;伸长内支撑可以一定程度减小基坑围护结构和邻近沉井位移,但是会导致沉井局部弯矩和土压力急剧增大,工程中应加强土压力和结构变形监测。

套筒截面尺寸对套筒灌浆搭接接头拉伸性能影响试验

为研究套筒截面尺寸对套筒灌浆搭接接头受力性能的影响,进行了39个套筒厚度、内径不同试件的单向拉伸试验,研究了其破坏形态、极限承载力、延性、钢筋和套筒应变等性能.结果表明:试件的破坏形式有钢筋拉断破坏和钢筋拔出破坏;由于加载偏心影响,试件的有效搭接长度约为设计搭接长度的81%;套筒内径相同时,在一定厚度范围内,随壁厚增加,套筒约束增强,试件承载力增大;套筒壁厚相同时,壁厚较小(1.5 mm)时,约束较弱,内径(类似保护层厚度)越大,试件承载力越大,壁厚大于等于2.0 mm时,约束增强,试件发生拉断破坏,内径的增加对承载能力影响小;在弹性阶段,套筒壁厚比套筒内径对钢筋-灌浆料黏结力的影响更明显;套筒中部截面的纵向应变在加载前期为拉应变,随荷载增大逐渐向压应变转化;套筒中部截面的环向应变在加载前期为压应变,随荷载增大逐渐转变为拉应变.提出的接头极限黏结应力和钢筋临界搭接长度计算公式,适用性较好,可供实际工程参考.

基于裂缝诱导应力场的套管应力影响因素分析

水平井分段压裂形成人工裂缝,产生的裂缝诱导应力场影响套管应力分布。为研究在裂缝诱导应力场作用下套管应力影响因素,基于理论公式和有限元分析方法,建立套管应力力学模型和裂缝-地层-水泥环-套管三维有限元模型,借助力学模型验证有限元模型的可行性,模拟岩石弹性模量、套管内壁压力、水泥环弹性模量、地应力变化和施工排量对套管应力的影响,并针对徐深气田实际压裂段进行实例分析。研究结果表明:当岩石弹性模量低于15 GPa时,套管发生塑性形变,套管内壁无压力加剧了套管塑性变形程度;当套管内壁压力为100 MPa时,水泥环软硬程度对套管应力基本无影响;套管应力随着水泥环弹性模量的增大呈现增大的趋势,水泥环泊松比和软硬地层不改变套管应力变化趋势;随着地应力差值的增大,套管应力呈现减小的趋势;施工排量为16 m^(3)/min时,套管存在塑性变形,达到极限施工排量18 m^(3)/min时,套管完全失效。研究成果对压裂段套管的损坏防治具有一定的指导意义。

45钢工件正火开裂原因分析

某45钢工件正火后发现开裂。采用直读光谱仪、金相显微镜、布氏硬度计和扫描电镜等对开裂工件进行了宏观检验、化学成分分析、硬度测定、金相检验、断口分析和能谱分析。结果表明:工件中有粗大的网状和针状铁素体,夹杂物较多,因此脆性较大;由于正火升温过快,内应力较大。正是这两个因素导致工件正火开裂。

内、外圈相对倾斜对圆柱滚子轴承负荷和接触应力的影响

应用经典的滚动轴承理论以及“切片法”的基本思想,采用Romax Designer工程分析软件对某大兆瓦风电机组齿轮箱圆柱滚子轴承负荷分布和接触应力分布进行分析,重点研究了内、外圈相对倾斜对轴承负荷分布和接触应力的影响。研究结果表明:随着内、外圈相对倾斜量的增大,最大载荷减小,负荷分布趋于均匀,同时滚子与套圈间的最大接触应力随之增大。

航空轴承内圈滚道磨削残余应力的工艺优化及试验研究

对国内外8Cr4Mo4V钢制航空轴承套圈滚道磨削残余应力进行了对比试验,根据航空轴承内套圈滚道磨削工艺特点,基于ABAQUS建立轴承内套圈滚道磨削残余应力的有限元分析模型并进行了数值计算,对内套圈滚道的残余应力进行了检测、分析及验证,进而优化了轴承内套圈滚道磨削工艺。结果表明:通过增加喷丸工序、适当提高进给速度和终磨采用220目白刚玉砂轮替代石墨砂轮可有效提高轴承内圈滚道残余压应力。

液压缸往复密封圈表面接触应力监测研究

在液压缸中,往复动密封圈表面接触应力是决定其密封有效性的关键,但由于在工作过程中对往复密封表面接触状态进行监测的难度很大,因此对其变化规律仍缺乏深入了解。针对这一问题,以液压缸活塞杆Y形密封圈为对象,通过有限元仿真分析密封圈内唇磨损对密封圈表面接触应力的影响,确定密封圈表面接触应力的最佳监测部位;采用光纤光栅传感器(FBG)进行密封槽表面接触应力监测试验,通过铺设于密封槽的FBG传感器采集应力数据,得出密封圈周向和轴向接触应力均随内唇磨损增加呈现先增大后减小的趋势,与仿真结果一致;接触应力对密封磨损程度变化的响应灵敏度会随密封压力的增加而增大。研究结果为液压缸实际运行过程中往复动密封状态的监测提供了依据。

内外上模镶嵌三件式分流挤压模

当前新能源电动汽车发展迅猛,水冷式电动机是其核心部件之一。电动机外壳材料采用的是铝合金挤压型材,这种型材在生产中容易出现诸如内孔椭圆及壁厚差异大等形状与尺寸精度不达标的问题。解决这些问题的关键是模具。通过分析水冷式铝合金电动机外壳的结构特征及传统的模具现状,针对上述问题提出了一种内外上模镶嵌三件式分流挤压模,其主要部件包括分流板、上模和下模,而与传统分流模不同的是上模由一个外上模和一个内上模镶嵌组成。介绍了这种新型模具的组成以及主要部件的结构参数选择。采用分流板可以合理调配金属流量和降低挤压力。采用内、外上模镶嵌结构形式可以解决制造精度低及制造误差积累大的问题,使模具具有互换性,并且可节约材料和缩短加工周期。设计应力空间则可以保护内上模,解决壁厚严重不均的问题。实践表明,这种新型模具解决了传统模具在挤压时出现的问题,是一种值得复制和推广的新型模具。

发动机一级静子内环挡块断裂失效分析

对某型航空发动机故障一级静子内环挡块进行外观检查、断口分析、表面微观检查和材质分析,并对其进行应力分布计算,确定了故障一级静子内环挡块断口性质为高周疲劳,明确了挡块矩形凸块与细端的转接部位上表面前视侧的倒角处存在机械加工痕迹造成的应力集中,是导致内环挡块过早产生疲劳裂纹、发生断裂故障的主要原因,并提出了相应的改进建议。