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1.
厚壁圆筒在实际工程领域中应用广泛,若能精确计算出极限内压,对预防事故发生,降低风险有重要意义.工程中存在许多材料,其拉压强度和拉压模量均存在差异,这些差异对极限内压的大小有显著影响.以往研究表明,仅考虑拉压强度与拉压模量的一个方面,计算结果与实际情况存在一定的误差.本文基于双剪统一强度理论,综合考虑中间主应力效应及材料拉压强度和拉压模量的不同,推导了内压作用下厚壁圆筒的弹、塑性状态的应力分布及弹性极限内压、塑性极限内压与安定极限内压的统一解,通过与其他文献对比分析验证了本文计算结果的正确性,分析了半径比、统一强度理论参数、拉压强度比与拉压模量系数对弹性极限内压、塑性极限内压及安定极限内压的影响.结果表明:统一解均随半径比和统一强度理论参数的增大而增大,随拉压强度比的增大而减小,弹性极限内压随材料拉压模量系数的增大而减小,当壁厚增加到一定值后,安定极限内压随材料拉压模量系数的增大而减小;材料的拉压模量不同、拉压强度差异对厚壁圆筒的安定性影响显著,考虑中间主应力效应可使材料的潜能得到更充分发挥,极限内压随半径比的变化规律可为选择合理壁厚提供参考,该结论可为厚壁圆筒的工程应用提供理论依据.  相似文献   

2.
推导出了楔形矩形变截面双模量梁的截面高度表达式,利用静力平衡方程确定了楔形矩形变截面双模量梁弯曲时的中性层位置,得到了楔形矩形变截面双模量梁的弯曲剪应力计算公式.在考虑剪切变形影响的基础上,利用楔形矩形变截面双模量梁的弯曲剪应力计算公式,推导出了楔形矩形变截面双模量梁弯曲正应力计算公式.通过算例分析,讨论分析了楔形矩形变截面双模量梁的楔度比、剪力、长高比等对矩形截面双模量梁弯曲正应力的影响.研究结果表明:随着楔度比的增大,楔形矩形变截面梁弯曲拉、压正应力绝对值逐渐减小.当矩形截面双模量梁的长高比小于一定比值,剪力会对楔形矩形变截面双模量梁弯曲正应力产生较大的影响.得到了拉压弹性模量相差较大的情况,采用经典材料力学理论进行楔形矩形变截面双模量梁的弯曲应力计算分析是不合适的,应该采用双模量材料力学理论对梁弯曲应力进行分析计算的结论.  相似文献   

3.
岩石拉压弹性常数并不相同.基于拉压不同模量理论,考虑衬砌和围岩模量差异性,推导了压力隧洞的应力、位移新解及围岩弹性抗力表达式,并分析了模量差异对压力隧洞力学行为的影响.结果表明,新解可退化为经典解答;径向应力新解大于经典解,而切向应力则反之,位移经典解小于新解;围岩弹性抗力系数随压拉模量比增大呈抛物线变化.衬砌和围岩模...  相似文献   

4.
苏琼  程月华  吴昊 《爆炸与冲击》2023,(12):125-140
为构建爆炸荷载作用下超高性能混凝土(UHPC)板弯曲损伤等级评估的p-I(压力-冲量)曲线:采用条带法进行截面分析,建立了考虑UHPC材料拉/压软化和塑性铰影响的UHPC简支单向板的非线性抗力方程和等效单自由度(ESDOF)理论模型;通过与六炮次爆炸实验中UHPC板的挠度时程,以及UFC 3-340-02和FHWA规范推荐方法的计算结果对比,验证了本文理论模型的可靠性;基于验证的ESDOF模型,构建了评估UHPC板的不同弯曲损伤等级的p-I曲线并开展了参数影响分析,提出并验证了UHPC板弯曲损伤评估的p-I曲线经验公式。结果表明:提高混凝土强度等级和钢筋屈服强度、增加受拉钢筋配筋率和板厚,以及减小净跨均可提升UHPC板的抗爆性能。  相似文献   

5.
陶瓷材料动态抗弯性能测试   总被引:1,自引:0,他引:1  
用改装的Hopkinson压杆试验装置测试了陶瓷材料3点弯曲动态力学性能;定义了量纲一挠度和挠度变化率,给出了几种陶瓷材料在不同挠度变化率下的挠度-最大拉应力曲线,从而给出其抗弯强度。测试结果说明,陶瓷材料的动态抗弯强度具有挠度变化率效应。分析了3点弯曲动态测试的有效性和动态损伤,分析表明,动态损伤因子临界值具有挠度变化率效应。  相似文献   

6.
王苏  赵均海  姜志琳  朱倩 《力学季刊》2019,40(3):603-612
采用统一强度理论并考虑材料拉伸与压缩弹性模量的差异性,建立均匀内压作用下双层厚壁圆筒的应力表达式,获得了其内压相应的弹性极限解答、塑性极限解答,并分析拉压强度比、拉压模量系数、统一强度理论参数、半径比及分层半径对弹性、塑性极限内压的影响规律.研究结果表明:弹性、塑性极限内压随拉压强度比的增加而减小,但随统一强度理论参数、半径比的增加而增大;弹性极限内压随分层半径的增加呈现先增大后减小变化,随拉压模量系数的增加而一直减小;塑性极限内压与拉压模量系数、分层半径无关.应用于实际工程时,可根据所得结果选择合理的壁厚及分层半径,再根据材料特性确定其他参数,以便更加准确地计算结构的受力状况.  相似文献   

7.
拉压异性材料含受压圆孔大平板的极限分析   总被引:2,自引:0,他引:2  
探讨了广义双剪应力强度理论在平面应力状态下的屈服轨迹及其方程式,并用于拉压异性材料圆孔受内压的极限分析,得到了与拉压比有关的弹性极限内压力,弹塑性区的应力、塑性内压力与弹塑性分界半径之间的关系、塑性区的最大半径和最大内压力,所得极值均高于用莫尔强度理论分析的结果。  相似文献   

8.
复杂加载下混凝土的弹塑性本构模型   总被引:1,自引:0,他引:1  
万征  姚仰平  孟达 《力学学报》2016,48(5):1159-1171
混凝土材料在不同应力路径下或复杂加载条件下会表现出差异性显著的应力应变关系,在小幅循环加载条件下,其应力应变关系会表现出类似于弹性变形的滞回曲线.在不同应力水平下,混凝土的应力应变关系以及破坏特性都具有静水压力相关特点,即随着静水压力增大,各向异性强度特性弱化.此外,混凝土受压及受拉破坏机理不同,因而对应于混凝土硬化损伤亦有不同,即可分为受压硬化损伤,受拉硬化损伤及两者的混合硬化损伤类型.基于Hsieh模型,对该模型进行了三点改进.(1)针对小幅循环加载下混凝土无塑性变形的试验规律,而模型中在应力水平较低的循环加载条件下始终存在塑性变形的预测问题,采用在边界面模型框架下,设置了应力空间的弹性域,初始屈服面与后续临界状态屈服面几何相似的假定.(2)基于广义非线性强度准则将原模型采用变换应力方法将其推广为三维弹塑性本构模型,采用变换后模型可合理的考虑不同应力路径对于子午面以及偏平面上静水压力效应形成的影响,并避免了边界面应力点奇异问题.(3)分别对拉压两种加载损伤模式建议了相应的硬化参数表达式,可分别用于描述上述加载中产生的应变软化及强度退化行为.基于多种加载路径模拟表明:所建立的三维弹塑性本构模型可合理地用于描述混凝土的一般应力应变关系特性.   相似文献   

9.
混凝土分段曲线损伤模型   总被引:1,自引:0,他引:1  
在对比分析国内外现有的混凝土受拉损伤模型基础上,结合素混凝土受拉应力应变曲线的试验结果,提出了一个新的混凝土分段曲线损伤模型,并利用应力连续条件确定了损伤模型中各系数的值。运用该模型到力学分析中,推导了矩形截面的混凝土梁在纯弯矩作用下,在损伤较小和损伤较大时的力学方程,算出了梁的最大承载能力,并与材料力学计算的梁承载能力进行了对比。详细分析了损伤区域及损伤应力在横截面上的变化过程,确定了极限状态下含损伤混凝土梁的应力分布和相应的承载能力,画出了损伤状态梁截面的应力分布图。  相似文献   

10.
孔婷婷  杨骁 《力学季刊》2022,43(3):700-711
针对新型连续窄幅钢箱梁-混凝土组合桥梁,研究了该桥型桥梁的桥面板拉应力控制方法与措施.将该桥型组合桥梁等效为可变刚度的Euler梁,给出任意横向荷载作用下变刚度梁的静力弯曲解析通解,并得到三跨连续阶梯型变刚度梁变形及其内力分布特征.在此基础上,以三跨连续窄幅钢箱梁-混凝土组合桥梁为研究对象,考虑下部钢箱梁与上部混凝土桥面板完全剪力连接,通过改变负弯矩区钢箱梁壁厚、内部充填混凝土的强度、长度与高度等参数,分析得到可有效控制桥面板拉应力的关键因素.结果显示:在负弯矩区段内的钢箱梁内部充填混凝土对控制该区域混凝土桥面板拉应力效果明显,但混凝土强度影响较弱.混凝土桥面板开裂区域随钢箱梁中充填混凝土长度的增加而减少,但桥面板顶部拉应力会随混凝土充填高度的增加呈现先减小后增大的趋势,在充填高度为箱梁内部净高的20 %~30 %左右时效果较为显著,此时经济效益最佳.  相似文献   

11.
吴晓 《力学季刊》2016,37(3):581-589
采用弹性理论研究了拉压不同弹性模量薄板上圆孔的孔边应力集中问题.采用广义虎克定律推导出了拉压不同弹性模量薄板上圆孔边的应力平衡方程,并联合利用应力函数及边界条件得到了拉压不同弹性模量薄板上圆孔边的应力表达式.算例分析表明,当薄板材料的拉压弹性模量相差较大时,采用经典弹性理论研究薄板上圆孔的孔边应力是不合适的,当经典弹性理论与拉压不同弹性模量弹性理论的计算结果间的差别超过工程允许误差5%时,应该采用拉压不同弹性模量弹性理论进行计算.  相似文献   

12.
???????????????????????   总被引:1,自引:0,他引:1  
对具有不同拉压模量的厚壁球壳,采用双剪统一强度理论推导了其扩张问题的应力及位移的 统一解. 分析了不同模量、不同模型控制参数对厚壁球壳扩张时的扩张压力和应力场的影响. 结果表明:厚壁球壳弹性极限压力、应力场、位移场等均随着模量控制参数、模型参数的变 化而变化,在$\alpha<1$的情况下(即$E^ + < E^ - $),可以明显提高球壳的弹 性极限压力$p_e $; 厚壁球壳塑性极限压力与材料的拉压模量无关,与模型参数$\eta $有关,且随$\eta$的增加,先增大后减小. 因此若采用经典的弹性理论和单一的 模型参数对厚壁球壳进行设计计算,会带来较大的误差.  相似文献   

13.
含微裂纹材料的损伤理论   总被引:5,自引:1,他引:5  
本文从含微裂纹材料的变形能出发引出了裂纹的方位张量。在考虑裂纹受压闭合与滑动摩擦的基础上,给出了损伤张量、损伤应变及有效弹性常数。文中给出了损伤机构离散化的方法,并对方位密度给出了演化方程。最后给出一个单向拉压的应力应变关系例子,并揭示了裂纹扩展时的应力突跌现象。  相似文献   

14.
The investigated cantilever beam is characterized by a constant rectangular cross-section and is subjected to a concentrated constant vertical load, to a concentrated constant horizontal load and to a concentrated constant bending torque at the free end. The same beam is made by an elastic non-linear asymmetric Ludwick type material with different behavior in tension and compression. Namely the constitutive law of the proposed material is characterized by two different elastic moduli and two different strain exponential coefficients. The aim of this study is to describe the deformation of the beam neutral surface and particularly the horizontal and vertical displacements of the free end cross-section. The analysis of large deflection is based on the Euler–Bernoulli bending beam theory, for which cross-sections, after the deformation, remain plain and perpendicular to the neutral surface; furthermore their shape and area do not change. On the stress viewpoint, the shear stress effect and the axial force effect are considered negligible in comparison with the bending effect. The mechanical model deduced from the identified hypotheses includes two kind of non-linearity: the first due to the material and the latter due to large deformations. The mathematical problem associated with the mechanical model, i.e. to compute the bending deformations, consists in solving a non-linear algebraic system and a non-liner second order ordinary differential equation. Thus a numerical algorithm is developed and some examples of specific results are shown in this paper.  相似文献   

15.
吴晓 《力学季刊》2023,44(1):210-217
利用高阶剪切变形理论研究了双模量梁的弯曲变形问题,推导出了双模量梁的挠曲线方程及弯曲正应力公式.讨论分析了翘曲函数的指数n对挠度、正应力的影响.研究结果表明:拉压弹性模量的差异对梁的弯曲应力有较大影响.把高阶剪切变形理论的计算结果与弹性理论计算结果进行比较,可知该方法计算精度非常高.  相似文献   

16.
In this study, a simplified theory for functionally graded thin plates with different moduli in tension and compression is proposed. Based on the classical Kirchhoff hypothesis, a mechanical model concerning tension-compression subzone is established, first. Using the geometrical and physical relations and equation of equilibrium, all stress components are expressed in terms of the deflection, in which modulus of elasticity in tensile and compressive zone are regarded as two different functions while Poisson's ratios are taken as two different constants. Via the equilibrium conditions and continuity conditions, the governing equation expressed in terms of the deflection as well as the unknown neutral layer are derived, respectively. Moreover, the application in polar coordinates, the strain energy and the perturbation solution for the unknown neutral layer, are discussed in detail. The results indicate that the bending stiffness derived in this study play an important role while contacting the classical problem and this problem. The analytical solutions from equilibrium conditions and continuity conditions are consistent. Analyses of more general cases for modulus of elasticity and Poisson's ratio also show the applicability of the simplified theory. This study provides a theoretical basis for the subsequent work.  相似文献   

17.
The materials with different moduli in tension and compression are called bi-modulus materials. Graphene is such a kind of materials with the highest strength and the thinnest thickness. In this paper, the mechanical response of the bi-modulus beam subjected to the temperature effect and placed on the Winkler foundation is studied. The differential equations about the neutral axis position and undetermined parameters of the normal strain of the bi-modulus foundation beam are established. Then, the analytical expressions of the normal stress, bending moment, and displacement of the foundation beam are derived. Simultaneously, a calculation procedure based on the finite element method(FEM) is developed to obtain the temperature stress of the bi-modulus structures. It is shown that the obtained bi-modulus solutions can recover the classical modulus solution, and the results obtained by the analytical expressions, the present FEM procedure, and the traditional FEM software are consistent, which verifies the accuracy and reliability of the present analytical model and procedure. Finally, the difference between the bi-modulus results and the classical same modulus results is discussed, and several reasonable suggestions for calculating and optimizing the certain bi-modulus member in practical engineering are presented.  相似文献   

18.
对具有不同拉压模量的厚壁球壳,采用双剪统一强度理论推导了其扩张问题的应力及位移的统一解. 分析了不同模量、不同模型控制参数对厚壁球壳扩张时的扩张压力和应力场的影响.结果表明:厚壁球壳弹性极限压力、应力场、位移场等均随着模量控制参数、模型参数的变化而变化,在$\alpha<1$的情况下(即$E^ + < E^ - $),可以明显提高球壳的弹性极限压力$p_e $; 厚壁球壳塑性极限压力与材料的拉压模量无关,与模型参数$\eta$有关,且随$\eta$的增加,先增大后减小. 因此若采用经典的弹性理论和单一的模型参数对厚壁球壳进行设计计算,会带来较大的误差.  相似文献   

19.
Analyzed in this work is the four-point bending of a concrete slab supported by a steel beam. An edge crack is assumed to prevail on the tension side of the concrete that would grow gradually while the overall stiffness and local fracture toughness of the concrete would also degrade as damage accumulates. The latter two quantities are assumed to decrease with increasing deflection of the composite system. These effects are incorporated into the strain energy density criterion that can simultaneously predict crack initiation and growth including the event of final termination. Numerical results on load and deflection are obtained for two different composite concrete/steel beam systems such that the prevailing geometric material and loading parameters are accounted for as a combination. The distances between the local and global stationary values of the volume energy density are also determined as an indication of fracture instability. An edge crack tends to extend more stably as the compressive zone ahead increases with deflection of the composite beam.  相似文献   

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