延迟焦化装置中带碟簧的管法兰接头三维数值分析

应用有限元法分析延迟焦化装置中焦炭塔和管道的受力和变形,并针对生焦高温工况,对带有碟形弹簧的管法兰接头进行三维数值模拟,分析碟形弹簧对垫片应力的影响。模拟结果表明,生焦时焦炭塔受高温膨胀,导致管道弯曲变形,而内压对此影响相对要小很多;高温下选用适当的碟形弹簧,有利于维持管法兰接头的垫片工作应力。     

工程球罐的实测应力分析

基于图解法测试原理，用二次加载法测取了球罐错边和角变形部位的附加弯曲应力，通过弯曲应力分布曲线得到内、外壁危险点的位置，并用屈服应力法测算了危险点第一主应力方向的残余应力，从而得到危险点的实际应力且对其进行了强度分析。分析结果表明，两种测试法的精度均可满足工程要求，而且用来分析危险点的测试数据十分便利。     

风电塔筒法兰焊接变形控制的工艺措施

风力发电塔架法兰焊接时需要控制三个指标：法兰平面度、法兰角变形（即内倾量）、法兰椭圆度。在焊接过程中采取相应的工艺措施保证这三个指标,具有重要的经济效益。本文重点介绍了法兰焊接变形成因及焊接变形控制措施等,且该方法在实践中得到广泛应用,取得很好的效果。     

基于MSC.Marc的多道焊数值模拟

桥梁和船舶制造业一直受到焊接残余应力和变形所导致的生产费用提高、延误工期问题的困扰，研究焊接残余应力和变形具有重要的工程实际意义。本文利用有限元分析软件MSC．Marc对平板对接多道焊进行了实时三维数值模拟，得到了焊接温度场、焊后残余应力分布以及变形，并对模拟计算结果进行了定性分析。     

大型焦炭塔的设计与制造

以某炼油厂的焦炭塔为实例,结合焦炭塔的低周热疲劳工况,对选材、结构设计、焊接、热处理、无损检测及压力实验等主要工艺过程进行了论述和总结。在制造焦炭塔容器时选用具有抗高温蠕变,抗高温硫腐蚀以及对裂纹敏感性小的材料,在裙座与塔体的连接处采用整体锻焊型结构,可有效降低低周热疲劳引起的裙座与塔体连接焊缝的应力。     

Plastic deformation analysis in machining of Inconel-718 nickel-base superalloy using both experimental and numerical methods

Surface region plastic deformation of Inconel-718 nickel-base superalloy workpieces was evaluated when machined under orthogonal cutting conditions at various cutting speeds. Plastic deformation analysis was accomplished by determining the residual stress and plastic strain distributions in the surface region. The residual stresses were tensile and maximum near the surface and decreased in magnitude with an increase in depth beneath the machined surface. Similarly, the plastic strains were maximum near the surface and decreased with an increase in depth beneath the machined surface. In addition, a finite element simulation of orthogonal machining was carried out for predicting the residual stress and plastic strain distribution. In general, the trend of the curves predicted by the finite element model was similar to those found experimentally.     

7075铝合金板淬火残余应力模拟及实验研究

铝合金板在淬火过程中产生较大的残余应力,导致构件出现变形、翘曲。采用准耦合法对7075铝合金板在淬火过程中的温度场和应力场进行数值模拟,利用盲孔法对淬火后的残余应力分布进行实验测量。结果表明,7075铝合金板淬火后残余应力呈现出外压内拉的分布状态,淬火过程中形成的较大温度梯度造成的不均匀塑性变形是应力产生的主要因素,铝板表层和心部冷却速度的变化导致了应力分布状态的转变。实验结果验证了准耦合模拟方法的可行性,研究结论为残余应力控制提供重要依据。     

Effect of optimum plastic depth on stresses and load-bearing capacity of autofrettaged cylinder

Autofrettage is an effective measure to even distribution of stresses and raise load-bearing capacity for (ultra-)high pressure apparatus. Currently, the research on autofrettage has focused mostly on specific engineering problems, while general theoretical study is rarely done. To discover the general law contained in autofrettage theory, by the aid of the authors’ previous work and according to the third strength theory, theoretical problems about autofrettage are studied including residual stresses and their equivalent stress, total stresses and their equivalent stress, etc. Because of the equation of optimum depth of plastic zone which is presented in the authors’ previous work, the equations for the residual stresses and their equivalent stress as well as the total stress and their equivalent stress are simplified greatly. Thus the law of distribution of the residual stresses and their equivalent stress as well as the total stress and their equivalent stress and the varying tendency of these stresses are discovered. The relation among various parameters are revealed. The safe and optimum load-bearing conditions for cylinders are obtained. According to the results obtained by theoretical analysis, it is shown that if the two parameters, namely ratio of outside to inside radius, k, and depth of plastic zone, kj, meet the equation of optimum depth of plastic zone, when the pressure contained in an autofrettaged cylinder is lower than two times the initial yield pressure of the unautofrettaged cylinder, the equivalent residual stress and the equivalent total stress at the inside surface as well as the elastic-plastic juncture of a cylinder are lower than yield strength. When an autofrettaged cylinder is subjected to just two times the initial yield pressure of the unautofrettaged cylinder, the equivalent total stress within the whole plastic zone is just identically equal to the yield strength, or it is a constant. The proposed research theoretically depicts the stress state of ultra-)high pressure autofrettaged cylinder more accurately and more reasonably and provides the reference for design of (ultra-)high pressure apparatus.     

浅谈炼油装置中焦炭塔工作特点及失效模式

焦炭塔使用过程中,从室温到高温周期性运行,承受循环载荷,温差应力。常见失效模式主要有：焦炭塔裙座焊缝开裂、堵焦阀焊缝及周围开裂、焦炭塔塔体焊缝内表面开裂;塔体鼓凸、偏斜;塔体材料内部组织出现球化、石墨化现象;下塔盖变形发生泄漏等。     

沟曲率半径系数对柔性轴承应力的影响

采用有限元分析方法,使用ANSYS Workbench建立了柔性轴承的参数化接触模型。对不同沟曲率半径系数的柔性轴承进行静力学接触分析,得到了不同参数的柔性轴承内外圈的变形、应力的分布规律。结果表明:内外圈的最大等效应力和最大径向应力发生在长轴处的钢球与内外滚道接触的区域;内外圈最大等效应力、钢球与沟道的最大接触压力随内外圈沟曲率半径的增加呈线性增大趋势。用该方法能准确得到柔性轴承最大的接触应力,可以用来对柔性轴承进行优化设计。     

Uncertainty of residual stresses measurement by layer removal

A model to evaluate the uncertainty in the measurement of the through-thickness residual stress distribution in plates by the layer removal technique is presented. Thin layers were chemically etched from a stripe on rectangular specimens cut from a low carbon cold-rolled steel sheet. Phase shifting laser interferometry was used to measure the ensuing curvature. Polynomials were least-squares adjusted to the curvatures as a function of the etched depth. The polynomials were inserted into an integro-differential equation relating the curvature to the residual stresses, which were assumed to be a function of depth only. A comparison with X-ray diffraction measurement of the surface residual stresses showed good agreement. The uncertainty was found to increase steeply at the surfaces and to depend mainly on the assumed value for the modulus of elasticity, on the curvature fit, and on the depth of etching.     

焦炭塔瞬态温度场及热应力分析

焦炭塔是典型的承受复杂热循环的设备,工作过程中温度急剧变化引起的热应力是导致塔体变形乃至失效的主要因素。根据焦炭塔的实测温度曲线,利用大型有限元分析软件ANSYS,模拟焦炭塔生焦和冷焦两个过程中的瞬态温度变化,分析计算焦炭塔在瞬态温度变化下塔体中相应的热应力。     

Investigation of the coupled distribution of initial and machining-induced residual stress on the surface of thin-walled parts

Residual stress on the machined surface and the subsurface is known to influence the distortion of thin-walled parts. Therefore, it is essential to predict the distribution of surface residual stress accurately. In this paper, the coupled distribution law of initial residual stress and machining-induced residual stress is investigated. Firstly, a model with initial residual stress is established and incorporated into thermal mechanical coupled finite element model of 2-D cutting. Then, a tensile fixture is designed to impose initial stress into a thin-walled part of Al-6061, and cutting experiments are carried out. The residual stress distribution is measured by X-ray diffraction/electropolishing method. The results of experiments and simulation show that in the plastic deformation zone, the initial residual stress has no significant influence on the distribution of the machining-induced residual stress. In the elastic deformation zone, the stress that linear grows along depth from zero to initial residual stress is superimposed on machining-induced residual stress. The mathematical model of stress coupling distribution on the surface of thin-walled parts is established by numerical method. Finally, it is found that the effect of coupled stress distribution on distortion is more significant with the decrease of thickness (from 3 to 0.5 mm) of the thin-walled parts.     

Slip-line solution for orthogonal cutting with a chip breaker and flank wear

A slip-line field model for orthogonal cutting with chip breaker and flank wear has been developed. For a worn tool, this slip-line field includes a primary deformation zone with finite thickness; two secondary shear zones, one along the rake face and the other along the flank face; a predeformation zone; a curled chip; and a flank force system. It is shown that the cutting geometry is completely determined by specifying the rake angle, tool-chip interface friction and the chip breaker constraint. The chip radius of curvature, chip thickness, and the stresses and velocities within the plastic region are readily computed. Grid deformation patterns, calculated with the velocity field determined, demonstrate that the predicted effects of changes in frictional conditions at the tool-chip interface and of the rake angle on chip formation are in accord with experimental observations. The calculated normal stress distribution at the tool-chip interface is in general agreement with previously reported experimental measurements. The model proposed predicts a linear relationship between flank wear and cutting force components. The results also show that non-zero strains occur at and below the machined surface when machining with a worn tool. Severity and depth of deformation below the machined surface increases with increasing flank wear. Forces acting on the chip breaker surface are found to be small and suggest that chip control for automated machining may be feasible with other means.     

基于多点调形原理的旋转曲面连续成形

提出采用连续多点成形方法来实现旋转曲面件的高效、柔性成形。阐述了连续多点成形原理,并与传统的旋转曲面加工方法相对比,分析其所具备的特点。以盘形件为研究对象,建立有限元模型,分析成形过程中的等效应力和塑性应变场分布,通过模拟结果和主应变状态来分析皱曲现象。最后,研制相应的成形装置并进行了实验。结果表明:定心装置和柔性辊作用区的等效应力超过了材料的屈服极限,最大值达到213 MPa;成形件中心区域塑性应变值最大,达到0.07;柔性辊作用区塑性应变值次之,为0.03;皱曲区域的壳单元产生的是切向压缩变形,实验结果和模拟结果基本相同,都介于605~615 mm。应力应变场和皱曲的模拟结果与实际情况吻合,表明成形装置能加工出效果良好的旋转曲面件。     

基于有限元方法的某水库输泄水塔静力性能研究？

输泄水塔为大体积混凝土结构,其结构形式复杂,常建于相对塔体刚度较小的泥岩上,水塔与基础共同作用力学机理较为复杂。根据输泄水塔设计方案运用空间有限元计算理论,建立了带基础输泄水塔的三维 ANSYS 有限元模型,计算了该输泄水塔连同基础在5种工况下的强度和变形。研究结果表明,各工况下输泄水塔塔体所受应力满足混凝土强度设计要求,基础所受应力满足泥岩试验确定值;各工况下输泄水塔塔体位移和基础位移不大,满足规范要求。本研究可为工程设计提供参考。     

Loss of plane form equilibrium stability during pure “edgewise” bending of a strip

The problem of curved strip pure bending under a two-dimensional stress has been considered. The values of stresses, the bending moment, and the curvature radius of the stress rupture surface have been obtained. Hoopential uniform compressive stresses causing the loss of the plane form equilibrium stability of the deformable strip act in the region adjacent to its internal surface. The problem has been solved using the principle of virtual work and the variational equation representing a sum of the work of external and internal forces delivered on the strip deflection variations. When the deflection takes place, ring-type fibers of the strip extend. This leads to additional ring deformations and stresses opposite in sign to momentless deformations and stresses. It results in unloading.     

复合材料密封圈非线性大变形的有限元分析

采用非线性接触模型,建立了复合材料密封圈的大变形有限元方程,分析了这种密封圈在不同压缩量,不同减压槽半径以及不同接触区域尺寸下的变形和接触压应力的变化规律,得出密封圈安装固定与其压缩量、减压槽半径、接触区域尺寸等因素之间的关系。结果表明:密封圈的接触压应力主要是发生在密封圈的一些关键部位,其中最大压力发生在角点,在安装定位面上存在小的接触压应力,并且认为有这种接触应力存在时,安装是到位的。综合考虑过盈量、减压槽半径及各点的接触压应力与减压槽的变形率之间的关系,推荐使用0.04~0.08 mm的径向安装过盈量,0.2~0.5 mm的减压槽半径,减压槽变形率在25%~30%之间的密封圈比较合适。     

Subsurface deformation and damage accumulation in aluminum–silicon alloys subjected to sliding contact

The study of plastic deformation and damage accumulation below the contact surfaces is important in order to understand the dry sliding wear behaviour of aluminum alloys. Experimental evidence exists for the nucleation of voids and microcracks around second phase particles in the material layers adjacent to the contact surface. Propagation of these cracks at a certain depth below the surface may lead to the creation of long, thin plate-like wear debris particles. This work studied the deformation processes during sliding wear by means of metallographic observations of subsurface layers in an Al–7% Si (A356 Al) alloy and by finite element analyses. Specifically, the accumulation of subsurface stresses and strains was investigated, using a coupled structural-thermal finite element model based on the Voce-type exponential stress–strain relationship obtained from the sliding wear tests. Additionally, temperature and strain rate effects were taken into account using a constitutive equation based on Johnson–Cook and Cowper–Symonds models.Accordingly during sliding, the flow stress in subsurface layers increased rapidly and reached a saturation stress after a finite number of sliding contacts. The variation of hydrostatic pressure for different loading conditions was also determined as a function of sliding passes: as the sliding process progressed from the first to the seventh contacts, the hydrostatic pressure at the surface increased from 1150 to 1300 MPa. A total temperature increase of 45 K occurred at the surface after the seventh sliding contact. A debris formation model was proposed in which the presence of a maximum damage gradient at critical depth was considered. The model showed that, with a sliding velocity of 10 m/s, and a normal load of 150 N per unit thickness in mm, the material location where the maximum rate of damage occurred corresponded to a normalized depth (depth/counterface diameter) of 0.060. Increasing the load to 250 N/mm caused an increase in the critical depth of damage (a normalized depth of 0.085). Comparisons with the experimental subsurface crack observations indicate that the proposed damage rate calculations provide a good estimation of the subsurface crack propagation depth.     

9800焦炭塔结构的模态分析和振型研究

某石化公司9800焦炭塔是国内最大的焦炭塔,塔裙连接处采用一种新型的板焊结构,投入使用的一年内,塔裙连接处的应力槽部位出现裂纹。由于生产工艺的要求,焦炭塔的操作条件特别苛刻,因此,对于塔的动力学分析,尤其是进行模态分析得到其固有频率和振型是非常必要的。针对该塔进行模态分析,求得相应的固有频率和振动形式,从而全面地了解结构在操作过程中的自振特性,为进一步分析焦炭塔的动力学响应奠定了基础。