共查询到20条相似文献,搜索用时 156 毫秒
1.
宋静亚 《现代制造技术与装备》2011,(2):60-61
通过ANSYS大型有限元软件对含不同尺寸沟槽型缺陷的注蒸汽管道进行应力场模拟计算。分析中选用实体单元建立含体积型缺陷管道的3D模型,考虑了几何非线性和材料非线性以及缺陷位置、尺寸和形状对应力场的影响规律,并通过塑性失效准则计算了含不同缺陷注蒸汽管道的极限载荷。 相似文献
2.
含周向面型缺陷管道的失效评定曲线 总被引:1,自引:1,他引:0
1 引言失效评定图技术理论严格,使用方便,已经广泛应用于含缺陷容器的安全评定中。由于含周向缺陷管道的承受载荷和容器有很大的不同,为将这一先进的方法引入含周向缺陷管道的安全评定技术中,有必要研究含周向缺陷管道的失效评定曲线。管道周向缺陷的型式有面型缺陷和体积型缺陷。体积型缺陷失效模式一般为塑性极限载荷控制,评定时采用塑性极限载荷评定,无需进行断裂分析。面型缺陷的失效模式可能为极限载荷控制也可能为断裂控制失效模式,采用能同时考虑这两种失效模式的失效评定图技术是非常便利的。面型缺陷可以表征为表面裂纹、… 相似文献
3.
本文提出了在轴向力、弯矩、扭转及内压联合载荷作用下含周向裂纹管塑性破坏载荷的力学模型。按VonMises准则可确定塑性跨塌时净截面上诸正应力值,进一步又给出了各种裂纹管道(诸如表面裂纹、穿透裂纹等)的诸塑性极限载荷表达式。本文对缺陷评定十分有用。 相似文献
4.
弯曲载荷作用下局部减薄管道的极限载荷分析 总被引:6,自引:1,他引:5
本文采用弹塑性有限元分析,计算了纯弯曲载荷作用下局部减薄管道的极限弯矩。结果表明,管道的极限弯矩不仅与局部减薄的宽度有关而且与局部减薄的轴向长度也有关。当减薄长度大于某一临界值,有限元结果与不考虑减薄长度影响的净截面跨塌准则(Net-SectionCollapse)所得到的结果一致。所以,可以保守地用净截面跨塌准则来评定受弯曲载荷作用的局部减薄管道的极限承载能力。 相似文献
5.
6.
7.
弯头是管道系统中最薄弱、最容易失效的管件。研究含缺陷弯头的塑性承载能力在整个压力管道系统安全评定中占有重要地位。利用求取直管极限载荷的鼓胀系数法建立不考虑直管影响的含缺陷弯头的塑性极限载荷估算式。采用三维弹塑性有限元技术,对内压载荷作用下含纵向穿透裂纹弯头的塑性极限载荷进行系统分析。结果表明,裂纹削弱系数(PL/P LO)与厚径比(t/rm)无关,在实际工程应用中可忽略厚径比对裂纹削弱系数的影响。裂纹对长半径弯头的塑性极限承载能力影响程度明显大于对短半径弯头的。 相似文献
8.
局部减薄缺陷会降低压力管道的承载能力,影响管道的安全运行。通过应力强度评定、极限载荷分析及安全评定标准三方面对含局部减薄缺陷压力管道的承载能力进行系统研究,研究了缺陷尺寸(缺陷相对轴向长度,缺陷相对环向角度,缺陷相对深度)对许用载荷、极限载荷和安全评定载荷的影响规律。结果表明,在内压作用下,缺陷相对深度对管道的承载能力影响最大,缺陷相对轴向长度次之,缺陷相对环向角度的影响最小。对比分析发现许用载荷和安全评定载荷基本吻合,极限载荷值高于许用载荷值34.92%左右;许用载荷与安全评定载荷的比值会在一定范围内波动,存在缺陷尺寸相关性;极限载荷值与许用载荷值的比值和局部减薄缺陷的尺寸无关。相对于极限载荷,许用载荷、安全评定载荷是安全的,符合工程应用的要求。 相似文献
9.
10.
含多局部减薄缺陷压力管道的安全评定方法讨论 总被引:2,自引:0,他引:2
局部减薄是压力管道常见的一种体积型缺陷,在管道的服役过程中不仅会出现单个局部减薄缺陷,甚至会有多个局部减薄缺陷。通过有限元方法模拟内压作用下含双局部减薄缺陷管道获得其极限载荷,讨论了在不同的轴向和环向排列方式以及不同的局部减薄相对深度下,两局部减薄缺陷间的距离对压力管道极限载荷影响程度的差异。然后对所计算模型应用API 579-1 ASMEFFS-1—2007《适合服役》与GB/T19624—2004《在用含缺陷压力容器安全评定》中对多局部减薄(凹坑)处理方法进行评定,并与有限元得到的结果进行比较,发现两评定规范既存在着保守性,也存在着不安全性。最后对两评定规范所论述的方法进行修正,提出了一种新的用于内压作用下含多局部减薄缺陷管道的多局部减薄处理方法。 相似文献
11.
工程管道会受到腐蚀,形成管壁局部变薄等缺陷,使承载能力降低。评定局部腐蚀缺陷所引起的管道承载能力降低对于确保管线的安全运行具有重要意义。现有的评价含缺陷管弯曲特性的NSC准则,将缺陷视为无限长,无从考虑缺陷长度的影响。改进的含缺陷管道抗弯准则采用了B31G的有效壁厚概念,以有效壁厚tcorr取代了NSC准则中的t,得到了包含缺陷长度的缺陷管极限弯矩新计算公式。本研究选用外径为73和114mm的两种J55管线,在外表面预制了人工缺陷,通过三点弯曲对称加载试验对修正的含缺陷管道抗弯准则进行试验检验。结果表明,缺陷长度较小(L/√Rt〈1.5)时,试验结果与NSC标准相差较大,但与改进的含缺陷管道抗弯准则接近。缺陷的长度越大(L/√Rt〉3),试验结果与NSC准则和改进的NSC准则趋于一致。在本试验范围内管线直径对测试结果的变化规律无明显影响。 相似文献
12.
In the case of reinforced concrete slabs fixed at the boundaries, considerable enhancement in the load carrying capacity takes place due to compressive membrane action. In this paper a method is presented to analyse the effects of membrane action in fixed orthotropic circular slabs, carrying uniformly distributed loads. Depending on the radial moment capacity being greater or less than the circumferential moment capacity, two cases of orthotropy have been considered. Numerical results are worked out for certain assumed physical parameters and for different coefficients of orthotropy. Variations of load and bending moments with the central deflection are presented. 相似文献
13.
I. P. Nikiforov I. V. Plokhov P. N. Mal’tsev V. V. Ivanov 《Russian Engineering Research》2017,37(6):530-535
The microstructure of spherical inclusions (globules) in grinding sludge is analyzed, and the inclusions are classified. Their basic defects are considered. The formation of the spherical inclusions and their defects is explained in terms of the theory of physicochemical combustion of metal. Typical stages of chip combustion in the course of grinding are identified. 相似文献
14.
R. A. Sadrtdinov V. G. Rybalko D. V. Novgorodov 《Russian Journal of Nondestructive Testing》2013,49(3):164-169
This paper is devoted to the problems of increasing the reliability of industrial pipelines of compressor stations (CSs) that are subjected to bending loads. The results of the bending load simulation at a tube test bench are presented and variations in the stressed state under load are analyzed. Practical methods for reducing and testing bending stresses in pipelines are considered in the second part for different designs of gas transporting apparatuses. 相似文献
15.
Hyeonki Choi 《Journal of Mechanical Science and Technology》2000,14(3):338-349
Neck muscle forces and spinal loads at the C4/5 level were estimated that result from isometric voluntary ramp efforts gradually developing to maximums in flexion, extension, left lateral bending and right lateral bending. Electromyographic (EMG) activities, a three-dimensional anatomic data of the neck and a hybrid model, EMG-assisted optimization (EMGAO) model, were used. The model computed the cervical loads at 25%, 50%, 75%, and 100% of peak moments. The highest model-predicted C4/5 joint compressive forces occured during flexion; 361 (±164) N, 811 (±288), N, 1207 (±491) N and 1674 (±319) N in 25%, 50%, 75% and 100% of peak moment respectively. Variations in load distribution among the agonistic muscles and co-contractions of antagonistic muscles were estimated during ramp effors. Results suggest that higher C4/5 joint loads than previously reported are possible during isometric, voluntary muscle contractions. These higher physiological loads at C4/5 level must be considered possible during orthopedic reconstruction at this level. 相似文献
16.
17.
以第三代轮毂轴承为研究对象,推导了弯矩作用下滚动体与内滚道、外滚道的接触变形与接触载荷,提出了更为准确的接触载荷分布计算模型,分析了不同工况下轮毂轴承内部接触载荷和接触角的周向分布规律。在轮毂轴承内部载荷分布的一次修正基础上,考虑不同位置角的滚道材料和滚动体的接触疲劳,利用乘积定律进行统计处理,得到了第三代轮毂轴承疲劳寿命的修正L-P模型。结合ISO281—2007寿命修正计算方法,针对润滑现象进行二次修正,得到了经过润滑修正的第三代轮毂轴承疲劳寿命模型。利用旋转弯曲疲劳试验机进行了轴承的弯曲疲劳试验,试验结果显示,该疲劳寿命模型计算得到的理论值与试验值的误差在10%以内,验证了模型的正确性。 相似文献
18.
制动盘螺栓对保证列车制动和运行安全具有十分重要的作用,掌握制动盘螺栓弯矩分布规律对确保其使用寿命具有重要意义。采用高速动车组制动盘螺栓弯矩载荷测试技术,对国内多条实际线路的制动盘螺栓弯矩进行测试,获得了制动盘螺栓弯矩与动车组运行速度的关系。依据轮装制动盘螺栓连接结构的尺寸和工作环境开展理论分析,获得了螺栓杆弯矩分布的理论值。建立轮装制动盘车轮结构有限元模型,模拟仿真车轮高速旋转过程中螺栓杆受力情况,得到不同速度下螺栓杆的弯矩分布有限元解。研究结果表明,螺栓杆上的弯矩与列车运行速度密切相关,且运行速度越大,螺栓杆上弯矩越大。理论推导和有限元仿真结果均表明螺栓杆上各截面的弯矩大小和方向并不一致,在内外侧截面和中间截面出现弯矩极值,且方向相反。由于车轮内外结构的不对称性,导致螺栓杆上靠近轮缘一侧的截面弯矩大于外侧截面弯矩。研究工作为进一步研究制动盘螺栓的结构可靠性奠定了基础。 相似文献
19.
A.K. Niyogi 《International Journal of Mechanical Sciences》1973,15(10):781-787
Approximate analysis of bending of a pin-pointed beam under distributed load resting on elastic foundation is considered. The supports are assumed to be immovable, thereby giving rise to the axial stretching of the neutral surface under lateral loads. The resulting problem is nonlinear since the axial force of constraint is dependent on the lateral displacements. Quantitative results of axial force, benidng moment and deflections are given in terms of two dimensionless parameters which depend on the load intensity, foundation modulus and properties of the beam. 相似文献
20.
M.D. Xue X.F. Wang F.W. Williams B.Y. Xu 《International Journal of Mechanical Sciences》1997,39(9):965-976
This paper is concerned with axisymmetric structures subjected to various combinations of steady and (irregularly) pulsating mechanical and thermal loads. The numerical method is based on the static shakedown theorem, which deals with elastic-perfectly-plastic bodies. Linear temperature dependence of the yield condition in a 4D stress space is considered. The pseudo-residual stress field is simulated by the Temperature Parameter Method and the yield surface is linearized, so that the shakedown analysis is transformed into a linear programming problem and hence the computational difficulties otherwise encountered are overcome. The shakedown analysis of cylinders and spherical shells with and without defects is presented in this paper. Results presented show that the method is beneficial for the shakedown analysis of complicated structures subjected to various combinations of loads. 相似文献