检索结果-内蒙古大学图书馆

Stress analysis of perforated composite plates reinforced with carbon nanotubes with different distributions

EMERGENT MATERIALS 2021年第6期4卷 1711-1723页

作者： Zeighami, Vahid Jafari, Mohammad Shahrood Univ Technol Fac Mech & Mechatron Engn Shahrood Iran

This study deals with calculating the resultant moments and forces around an elliptical and circular holes in a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates. Various distributions of the reinforcement materials aligned uni-axially are investigated considering three functionally graded and uniform distributions of carbon nanotubes along thickness direction. The mechanical properties of CNTs (carbon nanotube-reinforced) are temperature- and size-dependent and are calculated by molecular dynamics simulations. Based on the gradual changes in the thickness direction and the established rule of the mixture, the effective mechanical properties of the FG-CNTRC plates are approximated. complex variable technique is used to estimate the resultant moments and forces around the elliptical and circular holes in the FG-CNTRC plate. The impacts of CNT distribution shape, the aspect ratio of hole shape, the volume fraction of CNTs, temperature dependence, and hole orientation on the resultant moments and forces around the elliptical and circular holes are investigated in detail. The highest resultant moment and force do not necessarily reduce with increasing the volume fraction of CNT;hence, the volume fraction should increase purposefully. Aligning the CNT axis with applied loading will lead to the lowest values of the highest resultant moments and forces in the holes with less elongation in a vertical direction to the nanotube axis. According to the results, the above parameters have a significant impact on the distribution of stress resultants and moments around the cutout in CNTRC plates, and the load-bearing capacity of these plates with cutouts can be improved by careful selection of these parameters.

关键词： complex variable method Potential functions Functionally graded carbon nanotube-reinforced composite The subsequent forces and moments

来源：评论

学校读者我要写书评

暂无评论

Displacements and stresses around a circular tunnel in an elastic medium with pseudo-static horizontal earthquake body forces

引用

COMPUTERS AND GEOTECHNICS 2023年第1期162卷

作者： Jain, Hemant Kumar, Jyant Indian Inst Sci Dept Civil Engn Bengaluru 560012 India

This manuscript presents an analytical solution based on the complex variable approach for computing dis-placements and stresses around a single circular tunnel in a linear elastic medium in the presence of pseudo-static horizontal earthquake body forces. The solution has been obtained with the imposition of uniform as well as non-uniform radial displacement boundary conditions along the tunnel's periphery taking the ground volume loss (GVL) as a governing input parameter. The non-uniform radial displacements' boundary condition along the tunnel periphery has been modelled by using the Gaussian distribution function. The effects of the distribution of the tunnel's peripheral displacements, Poisson's ratio of the continuum and the depth to radius of the tunnel on the results have been examined. Necessary validation exercise, in the presence of horizontal earthquake accel-eration, has also been carried out by comparing the obtained results with that computed on the basis of the finite element method. The results were also compared with that reported in literature. It was observed that with an increase in the pseudo static acceleration, there is (i) a significant increase in the horizontal displacements, (ii) a generation of non-symmetric displacement and stress pattern, (iii) an increase in the shear stresses, and (iv) the development of high deviatoric stress zones around the tunnel periphery.

关键词： Ground settlements Elastic analysis Tunnels Earthquakes complex variable method

来源：评论

学校读者我要写书评

暂无评论

Minimization of thermal stress in perforated composite plate using metaheuristic algorithms WOA, SCA and GA

引用

COMPOSITE STRUCTURES 2023年第Part2期304卷

作者： Jafari, Mohammad Chaleshtari, Mohammad Hossein Bayati Khoramishad, Hadi Altenbach, Holm Shahrood Univ Technol Fac Mech & Mechatron Engn Shahrood Iran Iran Univ Sci & Technol Sch Mech Engn Tehran 16846 Iran Otto von Guericke Univ Inst Mech Tech Mech Fak Maschinenbau D-39106 Magdeburg Germany

In this study, an attempt is made to achieve optimal thermal stress distribution in symmetric composite plates with non-circular holes under uniform heat flux by using metaheuristic optimization algorithms. The analytical solution is based on the thermo-elastic theory and the complex variable method. In addition, the stress analysis of laminated composite plates with circular holes is extended to non-circular holes using the appropriate mapping function. To determine the optimum thermal stress, the whale optimization algorithm (WOA) which is inspired by the lifestyle of humpback whales in nature, the sine cosine algorithm (SCA) that is inspired by the calculation of sine and cosine functions and the genetic algorithm (GA) are utilized. The effect of hole orientation, stacking sequence of laminates, bluntness and hole shape as significant parameters on optimum thermal stress distribution around the holes are studied. The laminate is made of graphite/epoxy material with stacking sequences of [0/ 90]s, [45/-45]s and [30/0/-30]s. The cost function is considered as the maximum value of thermal stress surrounding the hole. The performance of optimization algorithms is examined. It is found out that the circular shape for hole may not necessarily be the optimum geometry for all stacking sequences.

关键词： Thermal stress complex variable method Perforated laminated composites Whale optimization algorithm (WOA) Sine cosine algorithm (SCA) Genetic algorithm (GA)

来源：评论

学校读者我要写书评

暂无评论

Failure behavior of horseshoe-shaped tunnel in hard rock under high stress:Phenomenon and mechanisms

引用

Transactions of Nonferrous Metals Society of China 2022年第2期32卷 639-656页

作者： Hao WU Guo-yan ZHAO Shao-wei MA School of Mines China University of Mining and TechnologyXuzhou 221116China School of Resources and Safety Engineering Central South UniversityChangsha 410083China

A particle flow code(PFC) was first applied to examining the mechanical response of a horseshoe-shaped opening in prismatic rock models under biaxial compression. Next, an improved complex variable method was proposed to derive the stress distribution around the opening. Lastly, a case study of tunnel failure caused by rock burst in Jinping Ⅱ Hydropower Station was further analyzed and discussed. The results manifest that a total of four types of cracks occur around the opening under low lateral confining stress, namely, the primary-tensile cracks on the roof-floor, sidewall cracks on the sidewalls, secondary-tensile cracks on the corners and shear cracks along the diagonals. As the confining stress increases, the tensile cracks gradually disappear whilst the spalling failure becomes severe. Overall, the failure phenomenon of the modelled tunnel agrees well with that of the practical headrace tunnel, and the crack initiation mechanisms can be clearly clarified by the analytical stress distribution.

关键词： horseshoe-shaped tunnel fracture behavior rock burst stress distribution complex variable method particle flow code

来源：评论

学校读者我要写书评

暂无评论

Theoretical study on residual thermal stresses caused by the brazing process in annular and bilayer structures

引用

ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK 2023年第1期74卷 36-36页

作者： Song, Kun Li, Nian Ling, Xiang Schiavone, Peter Nanjing Tech Univ Sch Mech & Power Engn 30 Puzhu South Rd Nanjing Jiangsu Peoples R China Univ Alberta Dept Mech Engn Edmonton AB Canada

It is well-known that residual thermal stress poses a significant threat to the stability and reliability of brazed structures. However, theoretical studies focusing on the effects of residual thermal stress on even simple brazed structures remain largely absent from the literature. In this paper, we use complex variable methods to derive theoretical solutions characterizing residual stress fields for annular and bilayer structures. In addition, using a series of numerical examples, we investigate the main factors determining residual thermal stress in brazing. Our results show that both radial and hoop stress are present in the annular structure while the stress component parallel to the interface is the unique principal stress in the bilayer structure. In an annular structure in which the total thickness of materials coincides with the length of the inner radius, the residual thermal stress in the outer base material is four times higher than that of the inner base material. This is attributed to the fact that the two materials have different curvatures. In the case of a thin-wall structure in which the inner radius is ten times that of the total thickness of materials, the corresponding residual thermal stress has no more than 15% error when compared to that from the bilayer structure. Since the distortion of brazed structures is due mainly to the effects of residual thermal stress within the corresponding base materials, it would seem practical to minimize the thickness of the solder used in the brazing process.

关键词： Brazing process Residual thermal stress Analytical solution complex variable method

来源：评论

学校读者我要写书评

暂无评论

A complex variable Solution for Shallow Rectangular Tunnel in Semi-Infinite Plane

引用

JOURNAL OF ENGINEERING MECHANICS 2022年第4期148卷

作者： Tong, Longyong Zhou, Hang Shen, Hang Liu, Hanlong Chongqing Univ Coll Civil Engn Key Lab New Technol Construct Cities Mt Areas Chongqing 400045 Peoples R China

The rectangular pipe jacking method, as a new type of shallow tunnel excavation technology, is increasingly widely used in practical engineering due to its advantages of higher space utilization and fewer impacts on the surrounding environment. The construction process of pipe jacking will cause stress change and deformation of the surrounding soil. In this paper, on the basis of the complex variable elasticity, an analytical solution for a shallow rectangular pipe jacking tunnel under the action of rectangular cavity contraction and inner uniform pressure is proposed. Through the conformal mapping technique, the rectangular cavity in a semi-infinite plane is first transformed as a unit concentric ring. Then, the stress functions for the stress and displacement around the rectangular cavity under two types of boundary conditions are derived, which allows the stress change and deformation of the surrounding soil to be determined. The proposed analytical solutions are verified by comparison with the results of finite-element numerical simulations. Parametric studies are conducted to investigate the influence of the Poisson's ratio effects of soil, tunnel aspect ratio, and tunnel burial depth on the stress and displacement of soil. The proposed analytical solution can be potentially applied to the problem of a rectangular tunnel using pipe jacking.

关键词： Shallow rectangular pipe jacking tunnel Stress Displacement complex variable method Conformal mapping

来源：评论

学校读者我要写书评

暂无评论

Thermal stress analysis of perforated unsymmetric FG-CNTRC plate using a general analytical solution

引用

THIN-WALLED STRUCTURES 2022年 173卷 108956-108956页

作者： Zeighami, V Jafari, M. Shahrood Univ Technol Fac Mech & Mechatron Engn Shahrood Iran

In this study, based on the development of the complex variable method, a general solution is presented to calculate thermal stresses in unsymmetric functionally graded carbon nanotube-reinforced composite (FGCNTRC) plates weakened by a hole under uniform heat flux. The extracted equations can also be used for thermal analysis of perforated FGM plates and unsymmetric composites laminates. Due to the fact that size and temperature affect the mechanical properties of carbon nanotubes (CNT), the material properties of the unsymmetric FG-CNTRC plates are approximated based on gradual changes in the direction of thickness and extended rule of the mixture. The present analysis considers the effect of important parameters such as CNT volume fraction, CNT angle, hole aspect ratio, hole orientation, and heat flux angle on the distribution of thermal stresses and moments around elliptical and circular holes. The present comprehensive parametric study shows that the aforementioned variables have a significant effect on the thermal stresses in perforated FG-CNTRC plates. Therefore, by properly selecting their values in the design of such plates, thermal stresses can be significantly reduced.

关键词： Perforated FG-CNTRC plate complex variable method Uniform heat flux Thermal stress Unsymmetric nanocomposite plates

来源：评论

学校读者我要写书评

暂无评论

A finite Zener-Stroh crack interacting with a blunt crack under in-plane deformations

引用

EUROPEAN JOURNAL OF MECHANICS A-SOLIDS 2022年 92卷 1页

作者： Wang, Xu Schiavone, Peter East China Univ Sci & Technol Sch Mech & Power Engn 130 Meilong Rd Shanghai 200237 Peoples R China Univ Alberta Dept Mech Engn Donadeo Innovat Ctr Engn 10 203 Edmonton AB T6G 1H9 Canada

A Zener-Stroh crack is the name given to a microcrack resulting from the coalescence of edge dislocations along a slip plane. The process by which the crack is initiated was proposed in the first instance by Zener and later examined in detail by Stroh. The Zener-Stroh crack can be thought of as being equivalent, in some sense, to the Griffith crack in classical linear elastic fracture mechanics. We study a finite mode I and II Zener-Stroh crack interacting with a nearby mode I and II blunt crack represented by a parabolic cavity. In this respect, the ZenerStroh crack can be considered as a coalescence of edge dislocations emitted from the blunt crack. A conformal mapping function is introduced which maps the parabolic boundary onto a straight line in the image plane. By treating the Zener-Stroh crack as a pileup of edge dislocations, two Cauchy singular integral equations are constructed in the image plane. The Gauss-Chebyshev integration formula is applied to numerically solve the resulting singular integral equations. The local mode I and II stress intensity factors at the two tips of the ZenerStroh crack are determined. We establish conditions on the propagation direction of the Zener-Stroh crack away from or toward the blunt crack. Also established are the conditions for the emission of an edge dislocation from the blunt crack by treating the edge dislocation as a Zener-Stroh crack with infinitesimal length. The dislocation emission criteria from the blunt crack are established here in elementary closed form and will thus be particularly convenient for application in engineering practice.

关键词： Blunt crack Zener-stroh crack Edge dislocation complex variable method Singular integral equation Stress intensity factor Material force

来源：评论

学校读者我要写书评

暂无评论

Analytical stress solution for rock mass containing two holes based on an improved Schwarz alternating method

引用

THEORETICAL AND APPLIED FRACTURE MECHANICS 2021年 116卷 103092-103092页

作者： Tan, Lihai Ren, Ting Dou, Linming Yang, Xiaohan Cai, Xin Qiao, Ming China Univ Min & Technol Sch Mines Xuzhou 221116 Jiangsu Peoples R China Univ Wollongong Sch Civil Min & Environm Engn Wollongong NSW 2522 Australia Cent South Univ Sch Resources & Safety Engn Changsha 410083 Hunan Peoples R China

In this study, the accuracy and generality of stress calculation for a plate containing double holes via Schwarz alternating method was investigated. The original Schwarz alternating method with inverse mapping function shows a good performance in terms of the stress solution for a plate containing two arched holes. However, for a plate containing two holes with corners, evitable error may be produced during the calculation because of the unsatisfying accuracy of inverse mapping function. This error is particularly obvious in the stress calculation for a plate containing two triangular holes. To address the problem, an improved Schwarz alternating method without the consideration of inverse mapping function was proposed in this study. The coordinate transformation of points around hole boundaries is realized by an optimization method instead of the inverse mapping function, which leads to little error during the calculation and thus improves the stress solution accuracy especially for plates containing holes with corners. With the employment of the improved method, the influences of connecting angle and lateral pressure coefficient on stress solutions for plates containing double U-shaped holes were discussed. In addition, DEM simulations were further conducted to study the influence of stress characteristics on the failure patterns of rock mass. The result shows that the hoop stress linearly relates to lateral pressure coefficient in the elastic plate and fractures always initiate around hole boundaries where high stress concentrates.

关键词： complex variable method Conformal mapping Schwarz alternating method Stress analytical solution DEM numerical simulation

来源：评论

学校读者我要写书评

暂无评论

Scattering of harmonic P1 and SV waves by a shallow lined circular tunnel in a poroelastic half-plane

引用

SOIL DYNAMICS AND EARTHQUAKE ENGINEERING 2022年 158卷 1页

作者： Liu, Qijian Yue, Cheng Zhao, Mingjuan Hunan Univ Coll Civil Engn Changsha 410082 Hunan Peoples R China Hunan Univ Key Lab Bldg Safety & Energy Efficiency Minist Educ Changsha 410082 Hunan Peoples R China Delft Univ Technol Fac Civil Engn & Geosci NL-2600 GA Delft Netherlands

An analytical solution for the scattering of harmonic P1 and SV waves in a poroelastic half-plane with a shallow lined tunnel is obtained using the plane complex theory in elastodynamics. In light of the wave function expansions, the wave fields of the poroelastic medium and the liner with unknown coefficients are obtained based on Biot's theory and Helmholtz decomposition. complex-valued expressions of the effective stresses, the fluid stress, and the displacements of the poroelastic medium and the liner are expressed by the complex variable function method and the conformal transformation technique. With the boundary conditions and the continuity of the medium-liner interface, the boundary value problem results in a series of algebraic equations. The unknown coefficients in the infinite set of algebraic equations can be solved numerically by truncating the series number. A parametric study for the incident SV waves is performed to investigate dynamic stress concentrations and fluid stress of the medium and the liner. Numerical results show that the embedment depth of the tunnel, the incident angle of the excitations, and the porosity of the medium have considerable influence on the dynamic responses of the medium and the liner. The shielding effect of the tunnel on the incident SV waves is obvious. For the big embedment depth of the tunnel, the scattered waves contribute little to the displacements and dynamic stress concentration of the medium and the liner. For a high porosity close to the critical value, the response of the medium-liner system to the incident waves is great.

关键词： Wave scattering Poroelastic half-plane Lined tunnel complex variable method Conformal mapping

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：