In order to improve the bending load-carrying capacity (BLCC) of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors (SCF) at the wel...In order to improve the bending load-carrying capacity (BLCC) of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors (SCF) at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.展开更多
The New Holland TT75 tractors currently in service in Chad use a tractor arm with three holes, the middle one of which has recurrent failures due to traction. The purpose of this work is to use a finite element model ...The New Holland TT75 tractors currently in service in Chad use a tractor arm with three holes, the middle one of which has recurrent failures due to traction. The purpose of this work is to use a finite element model to provide an improvement by modifying the geometric parameters to avoid premature failure of the tractor arms of the New Holland TT75. The ultimate force formula of Eurocode 3 was used to determine the maximum pressure to be applied and. A comparative traction study between the current arm and the proposed arm was performed, taking into account the variation in hole size, arm width and applied pressure for the determination of the stress concentration factor Kt. With the determination of Kt and for the arm width (w) less than or equal to 85 mm;the results showed that the proposed arm geometry is better.展开更多
The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the appr...The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the approach,the notch stress concentration factors for three typical fatigue-cracking modes(i.e.,root-toe,root-deck,and toe-deck cracking modes)were thoroughly investigated in this study.First,we developed a model for investigating the effective notch stress in rib-deck welds.Then,we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib-deck weld on the notch stress concentration factors.On this basis,the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors.Finally,we employed the proposed formulas in a case study.The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results.The results of the case study demonstrate the feasibility and reliability of the proposed formulas.It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib-deck welds.展开更多
A reasonably, simply and accurately modified shear-lag model was proposed. Based on the model, the stress redistributions due to the failure of some fibers in an intraply hybrid composite under tension were analyzed. ...A reasonably, simply and accurately modified shear-lag model was proposed. Based on the model, the stress redistributions due to the failure of some fibers in an intraply hybrid composite under tension were analyzed. The results show that the present calculating stress concentration factors very coincide with Fukuda and Chou's results, thus verifying the reasonableness and correctness of the present model and methods.展开更多
In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stre...In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.展开更多
Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and...Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and semi-empiricai method. Accuracy of the results obtained from these expressions is better, and application scope is wider, than the results of Durelli's photo-elastic experiment and Isida's formula. When eccentricity of the elliptical hole is within a certain range, the error is less than 8%. Based on the relation between the stress concentration factor and the stress intensity factor, a stress intensity factor expression for tension strips with a center or an eccentric crack is derived with the obtained stress concentration factor expressions. Compared with the existing formulae and the finite element analysis, this stress intensity factor expression also has sufficient accuracy.展开更多
Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on ...Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.展开更多
The method of wave-function expansion in elliptical coordinates,elliptical cosine half-range expansion and Mathieu function were applied to obtain an exact analytical solution of the dynamic stress concentration facto...The method of wave-function expansion in elliptical coordinates,elliptical cosine half-range expansion and Mathieu function were applied to obtain an exact analytical solution of the dynamic stress concentration factor(DSCF)around an elliptical cavity in a shallow,semi-elliptical hill.An infinite system of simultaneous linear equations for solving this problem was established by substituting the wave expression obtained by the Mathieu function including the standing wave expression of elliptical lining given herein into the boundary condition obtained by the region-matching method.The finite equations system with unknown coefficients obtained by truncation were solved numerically,and the results in the case of an ellipse degenerating into a circle were compared with previous results to verify the accuracy of the method.The effects of different aspect ratios,incident wave angles and aperture ratios on the dynamic stress concentration around the elliptical cavity were described.Some numerical results,when the elliptical hill was changed into a circular one,were analyzed and compared in detail.In engineering,this model can be regarded as a semi-cylindrical hill with an elliptical cylindrical unlined tunnel under the action of SH waves,and the results are significant in aseismic design.展开更多
The three-dimensional stress concentration factor (SCF) at the edge of elliptical and circular holes in infinite plates under remote tension has been extensively investigated considering the variations of plate thickn...The three-dimensional stress concentration factor (SCF) at the edge of elliptical and circular holes in infinite plates under remote tension has been extensively investigated considering the variations of plate thickness, hole dimensions and material properties, such as the Poisson’s coefficient. This study employs three dimensional finite element modeling to numerically investigate the effect of plate width on the behavior of the SCF across the thickness of linear elastic isotropic plates with a through-the-thickness circular hole under remote tension. The problem is governed by two geometric non-dimensional parameters, i.e., the plate half-width to hole radius (W/r) and the plate thickness to hole radius (B/r) ratios. It is shown that for thin plates the value of the SCF is nearly constant throughout the thickness for any plate width. As the plate thickness increases, the point of maximum SCF shifts from the plate middle plane and approaches the free surface. When the ratio of plate half-width to hole radius (W/r) is greater than four, the maximum SCF was observed to approximate the theoretical value determined for infinite plates. When the plate width is reduced, the maximum SCF values significantly increase. A polynomial curve fitting was employed on the numerical results to generate empirical formulas for the maximum and surface SCFs as a function of W/r and B/r. These equations can be applied, with reasonable accuracy, to practical problems of structural strength and fatigue, for instance.展开更多
The formulations of analytic-numerical method for the stress analysis of non-concurrent spatial tubular joints are introduced in the paper. The spatial DT joints with different eccentricity in the vertical diametrical...The formulations of analytic-numerical method for the stress analysis of non-concurrent spatial tubular joints are introduced in the paper. The spatial DT joints with different eccentricity in the vertical diametrical plane of chord are computed. Finally the influence of eccentricity on the stress at possible hot spots is discussed.展开更多
The compression of soil grain and pore fluid as well as viscid coupling of pore fluid and soil skeleton is considered, the scattering problem of incident plane P1 wave (fast compressional wave) by an infinite cylind...The compression of soil grain and pore fluid as well as viscid coupling of pore fluid and soil skeleton is considered, the scattering problem of incident plane P1 wave (fast compressional wave) by an infinite cylindrical shell deeply embedded in isotropic saturated soils is studied by adopting the amended Biot model, amplitude equations about potential functions of scattering and refracting fields are obtained, and the effect of dimensionless frequencies and shell thickness on the back-scattering spectra and dynamic stress concentration factors of two types of cylindrical shells with high and low rigidity are numerically computed and analyzed.展开更多
A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated ones.Eleven specimens were cut from a steel box girder,w...A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated ones.Eleven specimens were cut from a steel box girder,which was initially corroded in real seawater conditions.The surface of all corroded specimens was analysed applying photogrammetry techniques,and a statistical description of an idealised corroded surface of each specimen was established.Fatigue lives of specimens are determined from the fatigue tests.Based on experimentally obtained fatigue lives,the stress concentration factors are calculated concerning the ideally smooth specimens.The correlation between the statistical parameters of the corroded specimen surfaces and the estimated stress concentration factors is analysed.Idealised corroded surfaces,converted in graphical format,are then used for the finite element modelling in ABAQUS software,and stress concentration factors are estimated from the finite element results.A convergence study is performed to determine the appropriate finite element mesh density.Comparison between experimentally obtained and numerically estimated stress concentration factors is performed as well as correlation analysis between actual and finite element predicted crack locations.展开更多
This paper studies a numerical solution of multiple hole problem by using a boundary integral equation.The studied problem can be considered as a supposition of many single hole problems.After considering the interact...This paper studies a numerical solution of multiple hole problem by using a boundary integral equation.The studied problem can be considered as a supposition of many single hole problems.After considering the interaction among holes,an algebraic equation is formulated,which is then solved by using an iteration technique.The hoop stress around holes can be finally determined. One numerical example is provided to check its accuracy.展开更多
A major obstacle to achieving reasonable strength prediction of a composite only from its constituent information is in the determination of in situ strengths of the matrix. One can measure only the original strengths...A major obstacle to achieving reasonable strength prediction of a composite only from its constituent information is in the determination of in situ strengths of the matrix. One can measure only the original strengths of the pure matrix, on the basis of which the predicted transverse strengths of a unidirectional (UD) composite are far from reality. It is impossible to reliably measure matrix in situ strengths. This paper focuses on the correlation between in situ and original strengths. Stress concentrations in a matrix owing to the introduction of fibers are attributed to the strength variation. Once stress concentration factors (SCFs) are obtained, the matrix in situ strengths are assigned as the original counterparts divided by them. Such an SCF cannot be defined following a classical approach. All of the relevant issues associated with determining it are systematically addressed in this paper. Analytical expressions for SCFs under transverse tension, transverse compression, and transverse shear are derived. Closed-form and compact formulas for all of the uniaxial strengths of a UD composite are first presented in this paper. Their application to strength predictions of a number of typical UD composites demonstrates the correctness of these formulas.展开更多
Complex function and general conformal mapping methods are used to investigate the scattering of elastic shear waves by an elliptical cylindrical cavity in a radially inhomogeneous medium. The conformal mappings are i...Complex function and general conformal mapping methods are used to investigate the scattering of elastic shear waves by an elliptical cylindrical cavity in a radially inhomogeneous medium. The conformal mappings are introduced to solve scattering by an arbitrary cavity for the Helmholtz equation with variable coefficient through the transformed standard Helmholtz equation with a circular cavity. The medium density depends on the distance from the origin with a power-law variation and the shear elastic modulus is constant. The complex-value displacements and stresses of the in.homogeneous medium are explicitly obtained and the distributions of the dynamic stress for the case of an elliptical cavity are discussed. The accuracy of the present approach is verified by comparing the present solution results with the available published data. Numerical results demonstrate that the wave number, inhomogeneous parameters and different values of aspect ratio have significant influence on the dynamic stress concentration factors around the elliptical cavity.展开更多
In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters...In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters have a considerable impact on the variation of stress concentration factors on tubular TY-joints under axial loads.Thus,the highest stress concentration factor values are observed on the vertical brace than on the inclined one.The finite element results of the tubular structures were verified by parametric equations and experimental data.A parametric study was carried out by analyses using the nonlinear regression method to obtain parametric equations.These equations are used to calculate stress concentration factors and to analyse the fatigue resistance of TY-joints due to axial loads.展开更多
Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated. The solution of dynamic stress concentration factor is given using the Green's function an...Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated. The solution of dynamic stress concentration factor is given using the Green's function and the method of complex variable functions. First, the space is divided into upper and lower parts along the interface. In the lower half space, a suitable Green's function for the problem is constructed. It is an essential solution of the displacement field for an elastic half space with a semi-cylindrical hill of cylindrical elastic inclusion while bearing out-plane harmonic line source load at the horizontal surface. Thus, the semicircular disconnected curve can be constructed when the two parts are bonded and continuous on the interface loading the undetermined anti-plane forces on the horizontal surfaces. Also, the expressions of displacement and stress fields are obtained in this situation. Finally, examples and results of dynamic stress concentration factor are given. Influences of the cylindrical inclusion and the difference parameters of the two mediators are discussed.展开更多
The scattering of shear waves (SH waves) by nano-scale arbitrary shape inclusion in infinite plane is studied by complex variable function theory. Firstly, the governing equation and the relationships between stress a...The scattering of shear waves (SH waves) by nano-scale arbitrary shape inclusion in infinite plane is studied by complex variable function theory. Firstly, the governing equation and the relationships between stress and displacement are given by classical elastic theory. Secondly, the arbitrary shape inclusion in the two-dimensional plane is transformed into a unit circle domain by conformal mapping, the incident wave field and the scattered wave field are presented. Next, the stress and displacement boundary conditions are established by considering surface elasticity theory, The infinite algebraic equations for solving the unknown coefficients of the scattered and standing waves are obtained. Finally, the influence of surface effect, non-dimensional wave number, Shear modulus and hole curvature on the dynamic stress concentration factor are analyzed by some examples, the numerical results show that the surface effect weakens the dynamic stress concentration. With the increase of wave number, the dynamic stress concentration factor (DSCF) decreases. Shear modulus and hole curvature have significant effects on DSCF.展开更多
Scattering of the shear waves by a nano-sized cylindrical hole embedded the inhomogeneous is investigated in this study. The Helmholtz equation with a variable coefficient is transformed the standard Helmholtz equatio...Scattering of the shear waves by a nano-sized cylindrical hole embedded the inhomogeneous is investigated in this study. The Helmholtz equation with a variable coefficient is transformed the standard Helmholtz equation by the complex function method and the conformal mapping method. By wave function expanding method, the analytical expressions of the displacement field and stress field in the inhomogeneous medium are obtained. Considering the surface effect and using the generalized Young-Laplace equation, we obtain the boundary conditions at nano arbitrary-shaped hole, then the field equations satisfying boundary conditions are attributed to solving a set of infinite algebraic equations. Numerical results show that when the radius of the cylindrical cavity shrinks to nanometers, surface energy becomes a dominant factor that affects the dynamic stress concentration factor (DSCF) around the cylindrical cavity. The influence the density variation of the inhomogeneity on the DSCF is discussed at the same time.展开更多
基金The authors are grateful to be financially supported by Projects of Natural Science Foundation of Heilongjiang Province (No. E201458) , State Key Lab of Advanced Welding and Joining, Har- bin Institute of Technology (AWJ-M13-14) and Hei longjiang Prov- ince Department of Education (12541679).
文摘In order to improve the bending load-carrying capacity (BLCC) of undermatched butt joint under three-point bending load, the influence of joint geometric parameters on stress concentration factors (SCF) at the weld bottom center and the weld toe of uudermatched butt joint with single V-groove are studied respectively based on the finite element method in this paper. Results show that the reinforcement height and the cover pass width play decisive role in the BLCC for undermatched butt joint. BLCC of undermatched butt joint can be improved by choosing the appropriate joint geometric parameters.
文摘The New Holland TT75 tractors currently in service in Chad use a tractor arm with three holes, the middle one of which has recurrent failures due to traction. The purpose of this work is to use a finite element model to provide an improvement by modifying the geometric parameters to avoid premature failure of the tractor arms of the New Holland TT75. The ultimate force formula of Eurocode 3 was used to determine the maximum pressure to be applied and. A comparative traction study between the current arm and the proposed arm was performed, taking into account the variation in hole size, arm width and applied pressure for the determination of the stress concentration factor Kt. With the determination of Kt and for the arm width (w) less than or equal to 85 mm;the results showed that the proposed arm geometry is better.
基金This study was sponsored by the National Key Research and Development Project(No.2017YFE0128700)the Fundamental Research Funds for the Central Universities(B200203006).
文摘The effective notch stress approach for evaluating the fatigue strength of rib-deck welds requires notch stress concentration factors obtained from complex finite element analysis.To improve the efficiency of the approach,the notch stress concentration factors for three typical fatigue-cracking modes(i.e.,root-toe,root-deck,and toe-deck cracking modes)were thoroughly investigated in this study.First,we developed a model for investigating the effective notch stress in rib-deck welds.Then,we performed a parametric analysis to investigate the effects of multiple geometric parameters of a rib-deck weld on the notch stress concentration factors.On this basis,the multiple linear stepwise regression analysis was performed to obtain the optimal regression functions for predicting the notch stress concentration factors.Finally,we employed the proposed formulas in a case study.The notch stress concentration factors estimated from the developed formulas show agree well with the finite element analysis results.The results of the case study demonstrate the feasibility and reliability of the proposed formulas.It also shows that the fatigue design curve of FAT225 seems to be conservative for evaluating the fatigue strength of rib-deck welds.
基金theNationalNaturalScienceFoundationofChina( 1 990 2 0 0 4) theNaturalSci enceFoundationofGuangdongProvince China
文摘A reasonably, simply and accurately modified shear-lag model was proposed. Based on the model, the stress redistributions due to the failure of some fibers in an intraply hybrid composite under tension were analyzed. The results show that the present calculating stress concentration factors very coincide with Fukuda and Chou's results, thus verifying the reasonableness and correctness of the present model and methods.
基金The research work was financially supported by the National Natural Scientice Foundation of China(Grant No.10142001)by the Shandong Provincial Natural Scientice Foundation(Grant No.Y2006F46)
文摘In engineering practice, tubular X-joints have been widely used in offshore structures. The fatigue failure of tubular X-joints in offshore engineering is mainly caused by axial tensile stress. In this study, the stress concentration factor distribution along the weld toe in the hot spot stress region for tubular X-joints subject to axial loads have been analyzed by use of finite element method. Through numerical analysis, it has been found that the peak stress concentration factor is located at the saddle position. Thereafter, 80 models have been analyzed, and the effect of the geometric parameters of a tubular X-joint on the stress concentration factor has been investigated. Based on the experimental values of the numerical stress concentration factor, a parametric equation to calculate the stress concentration factor of tubular X-joints has been proposed. The accuracy of this equation has been verified against the requirement of the Fatigue Guidance Review Panel, and the proposed equation is found capable of producing reasonably accurate stress concentration factor values for tubular X-joints subject to axial loads.
基金supported by the National Natural Science Foundation of China (No. 51179115)
文摘Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and semi-empiricai method. Accuracy of the results obtained from these expressions is better, and application scope is wider, than the results of Durelli's photo-elastic experiment and Isida's formula. When eccentricity of the elliptical hole is within a certain range, the error is less than 8%. Based on the relation between the stress concentration factor and the stress intensity factor, a stress intensity factor expression for tension strips with a center or an eccentric crack is derived with the obtained stress concentration factor expressions. Compared with the existing formulae and the finite element analysis, this stress intensity factor expression also has sufficient accuracy.
基金Supported by National Defense Preliminary Research Project of China(Grant No.104010205)
文摘Neuber rule and Arola-Ramulu model are widely used to predict the stress concentration factor of rough specimens. However, the height parameters and effective valley radius used in these two models depend strongly on the resolution of the roughness-measuring instruments and are easily introduce measuring errors. Besides, it is difficult to find a suitable parameter to characterize surface topography to quantitatively describe its effect on stress concentration factor. In order to overcome these disadvantages, profile moments are carried out to characterize surface topography, surface topography is simulated by superposing series of cosine components, the stress concentration factors of different micro cosine-shaped surface topographies are investigated by finite element analysis. In terms of micro cosine-shaped surface topography, an equation using the second profile moment to estimate the stress concentration factor is proposed, predictions for the stress concentration factor using the proposed expression are within 10% error compared with the results of finite element analysis, which are more accurate than other models. Moreover, the proposed equation is applied to the real surface topography machined by turning. Predictions for the stress concentration factor using the proposed expression are within 10% of the maximum stress concentration factors and about 5% of the effective stress concentration factors estimated from the finite element analysis for three levels of turning surface topographies under different simulated scales. The proposed model is feasible in predicting the stress concentration factors of real machined surface topographies.
基金Fundamental Research Funds for Central Universities under Grant No.3072019CF0205。
文摘The method of wave-function expansion in elliptical coordinates,elliptical cosine half-range expansion and Mathieu function were applied to obtain an exact analytical solution of the dynamic stress concentration factor(DSCF)around an elliptical cavity in a shallow,semi-elliptical hill.An infinite system of simultaneous linear equations for solving this problem was established by substituting the wave expression obtained by the Mathieu function including the standing wave expression of elliptical lining given herein into the boundary condition obtained by the region-matching method.The finite equations system with unknown coefficients obtained by truncation were solved numerically,and the results in the case of an ellipse degenerating into a circle were compared with previous results to verify the accuracy of the method.The effects of different aspect ratios,incident wave angles and aperture ratios on the dynamic stress concentration around the elliptical cavity were described.Some numerical results,when the elliptical hill was changed into a circular one,were analyzed and compared in detail.In engineering,this model can be regarded as a semi-cylindrical hill with an elliptical cylindrical unlined tunnel under the action of SH waves,and the results are significant in aseismic design.
基金the support of the National Council for Scientific and Technological Development(CNPq)for this work.
文摘The three-dimensional stress concentration factor (SCF) at the edge of elliptical and circular holes in infinite plates under remote tension has been extensively investigated considering the variations of plate thickness, hole dimensions and material properties, such as the Poisson’s coefficient. This study employs three dimensional finite element modeling to numerically investigate the effect of plate width on the behavior of the SCF across the thickness of linear elastic isotropic plates with a through-the-thickness circular hole under remote tension. The problem is governed by two geometric non-dimensional parameters, i.e., the plate half-width to hole radius (W/r) and the plate thickness to hole radius (B/r) ratios. It is shown that for thin plates the value of the SCF is nearly constant throughout the thickness for any plate width. As the plate thickness increases, the point of maximum SCF shifts from the plate middle plane and approaches the free surface. When the ratio of plate half-width to hole radius (W/r) is greater than four, the maximum SCF was observed to approximate the theoretical value determined for infinite plates. When the plate width is reduced, the maximum SCF values significantly increase. A polynomial curve fitting was employed on the numerical results to generate empirical formulas for the maximum and surface SCFs as a function of W/r and B/r. These equations can be applied, with reasonable accuracy, to practical problems of structural strength and fatigue, for instance.
文摘The formulations of analytic-numerical method for the stress analysis of non-concurrent spatial tubular joints are introduced in the paper. The spatial DT joints with different eccentricity in the vertical diametrical plane of chord are computed. Finally the influence of eccentricity on the stress at possible hot spots is discussed.
文摘The compression of soil grain and pore fluid as well as viscid coupling of pore fluid and soil skeleton is considered, the scattering problem of incident plane P1 wave (fast compressional wave) by an infinite cylindrical shell deeply embedded in isotropic saturated soils is studied by adopting the amended Biot model, amplitude equations about potential functions of scattering and refracting fields are obtained, and the effect of dimensionless frequencies and shell thickness on the back-scattering spectra and dynamic stress concentration factors of two types of cylindrical shells with high and low rigidity are numerically computed and analyzed.
基金The work is supported by the Croatian Science Foundation within the projects IP-2013-11-8658 and lP-2019-04-2085This work is also performed within the scope of the Strategic Research Plan of the Centre for Marine Technology and Ocean Engineering(CENTEC)which is financed by the Portuguese Foundation for Science and Technology(Fundação para a Ciência e Tecnologia-FCT)under contract UIDB/UIDP/00134/2020.
文摘A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated ones.Eleven specimens were cut from a steel box girder,which was initially corroded in real seawater conditions.The surface of all corroded specimens was analysed applying photogrammetry techniques,and a statistical description of an idealised corroded surface of each specimen was established.Fatigue lives of specimens are determined from the fatigue tests.Based on experimentally obtained fatigue lives,the stress concentration factors are calculated concerning the ideally smooth specimens.The correlation between the statistical parameters of the corroded specimen surfaces and the estimated stress concentration factors is analysed.Idealised corroded surfaces,converted in graphical format,are then used for the finite element modelling in ABAQUS software,and stress concentration factors are estimated from the finite element results.A convergence study is performed to determine the appropriate finite element mesh density.Comparison between experimentally obtained and numerically estimated stress concentration factors is performed as well as correlation analysis between actual and finite element predicted crack locations.
文摘This paper studies a numerical solution of multiple hole problem by using a boundary integral equation.The studied problem can be considered as a supposition of many single hole problems.After considering the interaction among holes,an algebraic equation is formulated,which is then solved by using an iteration technique.The hoop stress around holes can be finally determined. One numerical example is provided to check its accuracy.
文摘A major obstacle to achieving reasonable strength prediction of a composite only from its constituent information is in the determination of in situ strengths of the matrix. One can measure only the original strengths of the pure matrix, on the basis of which the predicted transverse strengths of a unidirectional (UD) composite are far from reality. It is impossible to reliably measure matrix in situ strengths. This paper focuses on the correlation between in situ and original strengths. Stress concentrations in a matrix owing to the introduction of fibers are attributed to the strength variation. Once stress concentration factors (SCFs) are obtained, the matrix in situ strengths are assigned as the original counterparts divided by them. Such an SCF cannot be defined following a classical approach. All of the relevant issues associated with determining it are systematically addressed in this paper. Analytical expressions for SCFs under transverse tension, transverse compression, and transverse shear are derived. Closed-form and compact formulas for all of the uniaxial strengths of a UD composite are first presented in this paper. Their application to strength predictions of a number of typical UD composites demonstrates the correctness of these formulas.
基金National Science&Technology Pillar Program under Grant No.2015BAK17B06Natural Science Foundation of Heilongjiang Province,China under Grant No.A201310+1 种基金Scientific Research Starting Foundation for Post Doctorate of Heilongjiang Province,China under Grant No.LBH-Q13040the Fundamental Research Funds for the Central Universities of China under Grant No.HEUCF150203
文摘Complex function and general conformal mapping methods are used to investigate the scattering of elastic shear waves by an elliptical cylindrical cavity in a radially inhomogeneous medium. The conformal mappings are introduced to solve scattering by an arbitrary cavity for the Helmholtz equation with variable coefficient through the transformed standard Helmholtz equation with a circular cavity. The medium density depends on the distance from the origin with a power-law variation and the shear elastic modulus is constant. The complex-value displacements and stresses of the in.homogeneous medium are explicitly obtained and the distributions of the dynamic stress for the case of an elliptical cavity are discussed. The accuracy of the present approach is verified by comparing the present solution results with the available published data. Numerical results demonstrate that the wave number, inhomogeneous parameters and different values of aspect ratio have significant influence on the dynamic stress concentration factors around the elliptical cavity.
文摘In this paper,the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied.Our results reveal that,geometric parameters have a considerable impact on the variation of stress concentration factors on tubular TY-joints under axial loads.Thus,the highest stress concentration factor values are observed on the vertical brace than on the inclined one.The finite element results of the tubular structures were verified by parametric equations and experimental data.A parametric study was carried out by analyses using the nonlinear regression method to obtain parametric equations.These equations are used to calculate stress concentration factors and to analyse the fatigue resistance of TY-joints due to axial loads.
基金Project supported by the Natural Science Foundation of Heilongjiang Province (No.A0206)
文摘Scattering of SH wave from an interface cylindrical elastic inclusion with a semicircular disconnected curve is investigated. The solution of dynamic stress concentration factor is given using the Green's function and the method of complex variable functions. First, the space is divided into upper and lower parts along the interface. In the lower half space, a suitable Green's function for the problem is constructed. It is an essential solution of the displacement field for an elastic half space with a semi-cylindrical hill of cylindrical elastic inclusion while bearing out-plane harmonic line source load at the horizontal surface. Thus, the semicircular disconnected curve can be constructed when the two parts are bonded and continuous on the interface loading the undetermined anti-plane forces on the horizontal surfaces. Also, the expressions of displacement and stress fields are obtained in this situation. Finally, examples and results of dynamic stress concentration factor are given. Influences of the cylindrical inclusion and the difference parameters of the two mediators are discussed.
文摘The scattering of shear waves (SH waves) by nano-scale arbitrary shape inclusion in infinite plane is studied by complex variable function theory. Firstly, the governing equation and the relationships between stress and displacement are given by classical elastic theory. Secondly, the arbitrary shape inclusion in the two-dimensional plane is transformed into a unit circle domain by conformal mapping, the incident wave field and the scattered wave field are presented. Next, the stress and displacement boundary conditions are established by considering surface elasticity theory, The infinite algebraic equations for solving the unknown coefficients of the scattered and standing waves are obtained. Finally, the influence of surface effect, non-dimensional wave number, Shear modulus and hole curvature on the dynamic stress concentration factor are analyzed by some examples, the numerical results show that the surface effect weakens the dynamic stress concentration. With the increase of wave number, the dynamic stress concentration factor (DSCF) decreases. Shear modulus and hole curvature have significant effects on DSCF.
文摘Scattering of the shear waves by a nano-sized cylindrical hole embedded the inhomogeneous is investigated in this study. The Helmholtz equation with a variable coefficient is transformed the standard Helmholtz equation by the complex function method and the conformal mapping method. By wave function expanding method, the analytical expressions of the displacement field and stress field in the inhomogeneous medium are obtained. Considering the surface effect and using the generalized Young-Laplace equation, we obtain the boundary conditions at nano arbitrary-shaped hole, then the field equations satisfying boundary conditions are attributed to solving a set of infinite algebraic equations. Numerical results show that when the radius of the cylindrical cavity shrinks to nanometers, surface energy becomes a dominant factor that affects the dynamic stress concentration factor (DSCF) around the cylindrical cavity. The influence the density variation of the inhomogeneity on the DSCF is discussed at the same time.