A new quadrilateral finite element IQ4 is developed for the free vibration of carbon nanotube-reinforced composite(CNTRC)perforated plates with a central cutout.By enriching the membrane part and incorporating a proje...A new quadrilateral finite element IQ4 is developed for the free vibration of carbon nanotube-reinforced composite(CNTRC)perforated plates with a central cutout.By enriching the membrane part and incorporating a projected shear technique,the IQ4 element is proposed to address the known limitations of the standard Q4 element,such as shear locking and limited consistency in the coupling ofmembrane-bending components.The proposed element is formulated within the FSDT-based framework and assessed through benchmark tests to verify its convergence and accuracy.The governing equations are obtained via theweak formofHamilton’s principle.Particular attention is given to the influence of carbon nanotube volume fraction,distribution patterns,and boundary conditions on the fundamental frequency response of CNTRC plates with cutouts.In addition,a parametric study is conducted to assess the influence of cutout geometric configuration,shape,and size ratios on the vibrational response of the CNTRC plate.The numerical results demonstrate that the formulated IQ4 element provides stable and accurate estimations of natural frequencies,even in the presence of a cutout and the coupled effects of the non-uniform distribution of reinforcement through the plate thickness.The developed formulation is expected to contribute to the structural design and optimization of advanced lightweight systems,particularly in aerospace and mechanical engineering applications.展开更多
Based on Kirchhoff plate theory and the Rayleigh-Ritz method,the model for free vibration of rectangular plate with rectangular cutouts under arbitrary elastic boundary conditions is established by using the improved ...Based on Kirchhoff plate theory and the Rayleigh-Ritz method,the model for free vibration of rectangular plate with rectangular cutouts under arbitrary elastic boundary conditions is established by using the improved Fourier series in combination with the independent coordinate coupling method(ICCM).The effect of the cutout is taken into account by subtracting the energies of the cutouts from the total energies of the whole plate.The vibration displacement function of the hole domain is based on the coordinate system of the hole domain in this method.From the continuity condition of the vibration displacement function at the cutout,the transition matrix between the two coordinate systems is constructed,and the mass and stiffness matrices are completely obtained.As a result,the calculation is simplified and the computational efficiency of the solution is improved.In this paper,numerical examples and modal experiments are presented to validate the effectiveness of the modeling methods,and parameters related to influencing factors of the rectangular plate are analyzed to study the vibration characteristics.展开更多
Cutouts are inevitable in structures due to practical consideration.In order to investigate the free vibration of functionally graded plates with multiple circular and non-circular cutouts,finite element method is use...Cutouts are inevitable in structures due to practical consideration.In order to investigate the free vibration of functionally graded plates with multiple circular and non-circular cutouts,finite element method is used.The volume fraction of the material constituents is assumed to follow a simple power law distribution.The parameters considered in this paper are as follows：cutout size,cutout location,number of cutouts and different boundary conditions.It should be mentioned that free vibration for FG plates（such as rectangular？skew？trapezoidal？circular plates） with multiple cutouts has not been studied yet and hence the results out coming from this paper may be used as bench marks for future works.展开更多
Cutouts are often provided in composite structural components for practical reasons. For instance, aircraft components such as wingspar, fuselage and ribs are provided with cutouts for access, inspection, fuel lines a...Cutouts are often provided in composite structural components for practical reasons. For instance, aircraft components such as wingspar, fuselage and ribs are provided with cutouts for access, inspection, fuel lines and electric lines or to reduce the overall weight. This paper addresses the effect of boundary condition on buckling and postbuckling responses, failure loads, and failure characteristics of composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) and having different lay-ups under in-plane shear (positive and negative) load, using finite-element method. The FEM formulation is based on the first order shear deformation theory in conjunction with geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that the effect of boundary condition on buckling, first-ply failure and ultimate failure loads of a quasi-isotropic laminate with cutout is more for positive shear load than that for the negative shear load for almost all cutout shapes. It is also noted that under in-plane shear loads postbuckling stiffness of (0/90)4s laminate with circular cutout is maximum, while it is minimum for (45/—45)4s laminate with circular cutout, irrespective of boundary conditions.展开更多
A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing...A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the accuracy of the method and even more, allows us to validate the nu- merical analysis. Therefore, two important results are obtained： a simplified analytical solution for the buckling problem and validation of the numerical results. Another important and novel finding is related to the influence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90~ oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the ma- terial reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under cer- tainply orientation angles.展开更多
Steel plates are widely used in various structures, such as the deck and bodies of ships and bridges, and in the aerospace industry. In many instances, these plates are subjected to axial compression loads that predis...Steel plates are widely used in various structures, such as the deck and bodies of ships and bridges, and in the aerospace industry. In many instances, these plates are subjected to axial compression loads that predispose the sheets to instability and buckling. In this study, we investigate the buckling and post-buckling behaviors of steel plates having groove-shaped cutouts of various dimensions and angles using finite element method (FEM) (by ABAQUS software) and experimental tests (by an Instron servohydraulic machine). Boundary conditions were clamped by supports at upper and lower ends and free supports at the other edges. The results of both numerical and experimental analyses are compared, which show a very good agreement between them. Finally, based on the experimental findings, formulas are presented for the determination of the buckling load of such plates.展开更多
A 3-dimensional hybrid stress element with a traction-free cylindrical surface based on amodified complementary energy principle has been derived for efficient and accurate analysis of stressconcentration around circu...A 3-dimensional hybrid stress element with a traction-free cylindrical surface based on amodified complementary energy principle has been derived for efficient and accurate analysis of stressconcentration around circular cutouts in thin to thick laminated composites. New expressions of sixstress components are developed by using three stress-functions in cylindrical co-ordinates, so that thehomogeneous equilibrium equations, the interlayer surface transverse-stresses and the traction-freeboundary condition on the cylindrical surface are satisfied exactly, while the interelement traction conti-nuity has been relaxed via the Lagrange multiplier method. Transverse-shear deformation effects areincorporated in each layer with displacement continuity enforced along interlayer surface. Selected ex-amples are used to demonstrate the efficiency and accuracy of the present special element.展开更多
The perforated stiffened panel is generally found as a sub-component of sophisticated structures.The fundamental purpose of this panel is to withstand against buckling under complicated loading and environmental condi...The perforated stiffened panel is generally found as a sub-component of sophisticated structures.The fundamental purpose of this panel is to withstand against buckling under complicated loading and environmental conditions.Hence,an accurate knowledge of critical buckling behaviour of stiffened panels is very much essential for a reliable and lightweight structural design.In this paper,the focus is on quasi-laminated panels with different cutout shapes of various sizes and their responses to hygrothermal environments under nonlinearly varying edge loads and is compared with the locally stiffened panels.Towards this,the modelling of the panel and stiffener is done by adopting nine-noded heterosis plate elements and three noded beam elements respectively.The stiffener formulation is suitably modified in order to take the torsional effect also into consideration along with the effect of shear deformation.Initially,the plate and the stiffener elements are treated separately,and then the displacement compatibility is maintained between them by using the transformation matrix.For a given loading and geometric discontinuity,the stress distribution within the perforated panel is highly non-uniform in nature and hence a dynamic approach has been used to calculate buckling loads by adopting two sets of boundary conditions,one set for pre-buckling stress analysis and the second set for buckling analysis.Four different quasi-isotropic stacking sequences are deliberated in this work by varying different ply-orientation in each scheme.The study also addresses the effect of various parameters such as nonlinear loads,hygro-thermal loads,cutout size and shapes,position of cutout,stiffener parameters,stacking sequences,thickness of plate and boundary conditions.展开更多
Gasturbines are provided with cut-outs for minimizing vibrations. Round cut-outs are usually favored but there are various designs which offer more advantages over the circular shape. The objective of this work was to...Gasturbines are provided with cut-outs for minimizing vibrations. Round cut-outs are usually favored but there are various designs which offer more advantages over the circular shape. The objective of this work was to compare stress reduction during the induced vibration in the hollow gas turbine shafts by introducing different cut-outs. Round, square and elliptical cut-outs under different orientations were compared. It is observed that a square cutout at 45°?orientation has the least stress concentration. This is due to the effective orientation of plastic strains along the principal axis.展开更多
Stresses, particularly those at geometric discontinuities, influence the structural integrity of engineering components. Motivated by the prevalence of complicated-shaped perforated components, the objective of this p...Stresses, particularly those at geometric discontinuities, influence the structural integrity of engineering components. Motivated by the prevalence of complicated-shaped perforated components, the objective of this paper is to demonstrate the ability to stress analyze loaded finite members containing asymmetrical, irregularly-shaped cutouts. Recognizing the difficulties in obtaining purely theoretical or numerical solutions for these situations, the paper presents an expeditious means of experimentally stress analyzing such structures. Processing the load-induced temperature information with a series representation of a stress function provides the independent stress components reliably full-field, including on the edge of a hole. The stresses satisfy equilibrium and strains satisfy compatibility. In addition to being able to stress analyze complicated shapes using real, rather than complex variables, the technique is significant in which it smooths the recorded thermal information, is widely applicable, and requires neither differentiating the measured data nor knowing the elastic properties or external boundary conditions. The latter is extremely important since the external loading is often unknown in practice. That the approach provides the independent stresses is also significant since fatigue analyses and strength criteria typically necessitate knowing the individual components of stress. Present results are supported by those from a finite element analysis, strain gage measurements and load equilibrium.展开更多
BACKGROUND There are few studies in the literature comparing the clinical outcomes and radiographic results of proximal femoral nail(PFN)and proximal femoral nail antirotation(PFNA)for pertrochanteric femoral fracture...BACKGROUND There are few studies in the literature comparing the clinical outcomes and radiographic results of proximal femoral nail(PFN)and proximal femoral nail antirotation(PFNA)for pertrochanteric femoral fracture(PFF)in elderly patients.AIM To evaluate both clinical and radiographic outcomes after fixation with PFN and PFNA in an elderly patient population.METHODS One hundred fifty-eight patients older than 65 years with PFF who underwent fixation with either PFN or PFNA were included.Seventy-three patients underwent fixation with PFN,whereas 85 were fixed with PFNA.The mean follow-up was 2.4 years(range,1-7 years).Clinical outcome was measured in terms of operation time,postoperative function at each follow-up visit,and mortality within one year.Radiographic evaluation included reduction quality after surgery,Cleveland Index,tip-apex distance(TAD),union rate,time to union,and sliding distance of the screw or blade.Complications including nonunion,screw cutout,infection,osteonecrosis of the femoral head,and implant breakage were also investigated.RESULTS Postoperative function was more satisfactory in patients who underwent PFNA than in those who underwent PFN(P=0.033).Radiologically,the sliding difference was greater in PFN than in PFNA patients(6.1 and 3.2 mm,respectively,P=0.036).The rate of screw cutout was higher in the PFN group;eight for PFN(11.0%)and two for PFNA patients(2.4%,P=0.027).There were no differences between the two groups in terms of operation time,mortality rate at one year after the operation,adequacy of reduction,Cleveland Index,TAD,union rate,time to union,nonunion,infection,osteonecrosis,or implant breakage.CONCLUSION Elderly patients with PFF who underwent PFNA using a helical blade demonstrated better clinical and radiographic outcomes as measured by clinical score and sliding distance compared with patients who underwent PFN.展开更多
Based on Donnell's shallow shell equation, a new method is given in this paper to analyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With the method of complex var...Based on Donnell's shallow shell equation, a new method is given in this paper to analyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With the method of complex variable function, a series' of conformal mapping functions are obtained from different cutouts' boundary curves in the developed plane of a cylindrical shell to the unit circle. And, the general expressions for the equations of a cylindrical shell, including the solutions of stress concentrations meeting the boundary conditions of the large openings' edges, are given in the mapping plane. Furthermore, by applying the orthogonal function expansion technique, the problem can be summarized into the solution of infinite algebraic equation series. Finally, numerical results are obtained for stress concentration factors at the cutout's edge with various opening's ratios and different loading conditions. This new method, at the same time, gives a possibility to the research of cylindrical shells with large non-circular openings or with nozzles.展开更多
In this study,the effect of influencing parameters on the stress distribution around a polygonal cutout within a laminated composite under uniform heat flux was analytically examined.The analytical method was develope...In this study,the effect of influencing parameters on the stress distribution around a polygonal cutout within a laminated composite under uniform heat flux was analytically examined.The analytical method was developed based on the classical laminated plate theory and two-dimensional thermo-elastic method.A mapping function was employed to extend the solution of a perforated symmetric laminate with a circular cutout to the solution of polygonal cutouts.The effect of significant parameters such as the cutout angular position,bluntness and aspect ratio,the heat flux angle and the laminate stacking sequence in symmetric composite laminate containing triangular,square and pentagonal cutouts was studied.The Neumann boundary condition was used at the edges of the thermally insulated polygonal cutout.The laminate was made of graphite/epoxy(AS/3501) material with two different stacking sequences of [30/45]sand[30/0/-30]_(s).The analytical solutions were well validated against finite element results.展开更多
The laws that natural frequencies of rectangular plate with a cutout will change with size and position of cutout are obtained by analytic, numerical and experimental methods.
Based on the motion equations of flexural wave in Ambartsumian' s plates including the effects of transverse shear deformations,by using perturbation method of small parameter,the scatter- ing of flexural waves an...Based on the motion equations of flexural wave in Ambartsumian' s plates including the effects of transverse shear deformations,by using perturbation method of small parameter,the scatter- ing of flexural waves and dynamic stress concentrations in the plate with a cutout have been studied. The asypmtotic solution of the dynamic stress problem is obtained.Numerical results for the dynamic stress concentration factor in Ambartsumian's plates with a circular cutout are graphically presented and discussed.展开更多
Given the significant potential of multi-directional functionally graded materials(MFGMs)for customizable performance,it is crucial to develop versatile material models to enhance design optimization in engineering ap...Given the significant potential of multi-directional functionally graded materials(MFGMs)for customizable performance,it is crucial to develop versatile material models to enhance design optimization in engineering applications.This paper introduces a material model for an MFGM plate described by trigonometric functions,equipped with four parameters to control diverse material distributions effectively.The bending and vibration analysis of MFGM rectangular and cutout plates is carried out utilizing isogeometric analysis,which is based on a novel third-order shear deformation theory(TSDT)to account for transverse shear deformation.The present TSDT,founded on rigorous kinematics of displacements,is demonstrated to surpass other preceding theories.It is derived from an elasticity formulation,rather than relying on the hypothesis of displacements.The effectiveness of the proposed method is verified by comparing its numerical results with those of other methods reported in the relevant literature.Numerical results indicate that the structure,boundary conditions,and gradient parameters of the MFGM plate significantly influence its deflection,stress,and vibration frequency.As the periodic parameter exceeds four,the model complexity increases,causing result fluctuations.Additionally,MFGM cutout plates,when clamped on all sides,display almost identical first four vibration frequencies.展开更多
In this paper, based on the theory of thick shells including effects of transverse shear deformations, a complex variables analytic method to solve stress concentrations in circular cylindrical shells with a small cut...In this paper, based on the theory of thick shells including effects of transverse shear deformations, a complex variables analytic method to solve stress concentrations in circular cylindrical shells with a small cutout is established A general solution and expression satisfying the boundary conditions on the edge of arbitrary cutouts are obtained. The stress problem can be reduced to the solution of an infinite algebraic equation series, and can be normalized by means of this method. Numerical results for stress concentration factors of the shell with a small circular and elliptic cutout are presented.展开更多
In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic e...In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic equation series. The solution can be normal and effective by means of this method. Numerical results for stress concentrations in the shell with a circular, elliptic cutout are graphically presented.展开更多
文摘A new quadrilateral finite element IQ4 is developed for the free vibration of carbon nanotube-reinforced composite(CNTRC)perforated plates with a central cutout.By enriching the membrane part and incorporating a projected shear technique,the IQ4 element is proposed to address the known limitations of the standard Q4 element,such as shear locking and limited consistency in the coupling ofmembrane-bending components.The proposed element is formulated within the FSDT-based framework and assessed through benchmark tests to verify its convergence and accuracy.The governing equations are obtained via theweak formofHamilton’s principle.Particular attention is given to the influence of carbon nanotube volume fraction,distribution patterns,and boundary conditions on the fundamental frequency response of CNTRC plates with cutouts.In addition,a parametric study is conducted to assess the influence of cutout geometric configuration,shape,and size ratios on the vibrational response of the CNTRC plate.The numerical results demonstrate that the formulated IQ4 element provides stable and accurate estimations of natural frequencies,even in the presence of a cutout and the coupled effects of the non-uniform distribution of reinforcement through the plate thickness.The developed formulation is expected to contribute to the structural design and optimization of advanced lightweight systems,particularly in aerospace and mechanical engineering applications.
基金support of this work by the National Natural Science Foundation of China(No.51405096)the Fundamental Research Funds for the Central Universities(HEUCF210710).
文摘Based on Kirchhoff plate theory and the Rayleigh-Ritz method,the model for free vibration of rectangular plate with rectangular cutouts under arbitrary elastic boundary conditions is established by using the improved Fourier series in combination with the independent coordinate coupling method(ICCM).The effect of the cutout is taken into account by subtracting the energies of the cutouts from the total energies of the whole plate.The vibration displacement function of the hole domain is based on the coordinate system of the hole domain in this method.From the continuity condition of the vibration displacement function at the cutout,the transition matrix between the two coordinate systems is constructed,and the mass and stiffness matrices are completely obtained.As a result,the calculation is simplified and the computational efficiency of the solution is improved.In this paper,numerical examples and modal experiments are presented to validate the effectiveness of the modeling methods,and parameters related to influencing factors of the rectangular plate are analyzed to study the vibration characteristics.
文摘Cutouts are inevitable in structures due to practical consideration.In order to investigate the free vibration of functionally graded plates with multiple circular and non-circular cutouts,finite element method is used.The volume fraction of the material constituents is assumed to follow a simple power law distribution.The parameters considered in this paper are as follows：cutout size,cutout location,number of cutouts and different boundary conditions.It should be mentioned that free vibration for FG plates（such as rectangular？skew？trapezoidal？circular plates） with multiple cutouts has not been studied yet and hence the results out coming from this paper may be used as bench marks for future works.
文摘Cutouts are often provided in composite structural components for practical reasons. For instance, aircraft components such as wingspar, fuselage and ribs are provided with cutouts for access, inspection, fuel lines and electric lines or to reduce the overall weight. This paper addresses the effect of boundary condition on buckling and postbuckling responses, failure loads, and failure characteristics of composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) and having different lay-ups under in-plane shear (positive and negative) load, using finite-element method. The FEM formulation is based on the first order shear deformation theory in conjunction with geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that the effect of boundary condition on buckling, first-ply failure and ultimate failure loads of a quasi-isotropic laminate with cutout is more for positive shear load than that for the negative shear load for almost all cutout shapes. It is also noted that under in-plane shear loads postbuckling stiffness of (0/90)4s laminate with circular cutout is maximum, while it is minimum for (45/—45)4s laminate with circular cutout, irrespective of boundary conditions.
文摘A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the accuracy of the method and even more, allows us to validate the nu- merical analysis. Therefore, two important results are obtained： a simplified analytical solution for the buckling problem and validation of the numerical results. Another important and novel finding is related to the influence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90~ oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the ma- terial reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under cer- tainply orientation angles.
文摘Steel plates are widely used in various structures, such as the deck and bodies of ships and bridges, and in the aerospace industry. In many instances, these plates are subjected to axial compression loads that predispose the sheets to instability and buckling. In this study, we investigate the buckling and post-buckling behaviors of steel plates having groove-shaped cutouts of various dimensions and angles using finite element method (FEM) (by ABAQUS software) and experimental tests (by an Instron servohydraulic machine). Boundary conditions were clamped by supports at upper and lower ends and free supports at the other edges. The results of both numerical and experimental analyses are compared, which show a very good agreement between them. Finally, based on the experimental findings, formulas are presented for the determination of the buckling load of such plates.
基金The work was supported by the National Natural Science Foundation of China (Grant No. 100Tz064) .
文摘A 3-dimensional hybrid stress element with a traction-free cylindrical surface based on amodified complementary energy principle has been derived for efficient and accurate analysis of stressconcentration around circular cutouts in thin to thick laminated composites. New expressions of sixstress components are developed by using three stress-functions in cylindrical co-ordinates, so that thehomogeneous equilibrium equations, the interlayer surface transverse-stresses and the traction-freeboundary condition on the cylindrical surface are satisfied exactly, while the interelement traction conti-nuity has been relaxed via the Lagrange multiplier method. Transverse-shear deformation effects areincorporated in each layer with displacement continuity enforced along interlayer surface. Selected ex-amples are used to demonstrate the efficiency and accuracy of the present special element.
文摘The perforated stiffened panel is generally found as a sub-component of sophisticated structures.The fundamental purpose of this panel is to withstand against buckling under complicated loading and environmental conditions.Hence,an accurate knowledge of critical buckling behaviour of stiffened panels is very much essential for a reliable and lightweight structural design.In this paper,the focus is on quasi-laminated panels with different cutout shapes of various sizes and their responses to hygrothermal environments under nonlinearly varying edge loads and is compared with the locally stiffened panels.Towards this,the modelling of the panel and stiffener is done by adopting nine-noded heterosis plate elements and three noded beam elements respectively.The stiffener formulation is suitably modified in order to take the torsional effect also into consideration along with the effect of shear deformation.Initially,the plate and the stiffener elements are treated separately,and then the displacement compatibility is maintained between them by using the transformation matrix.For a given loading and geometric discontinuity,the stress distribution within the perforated panel is highly non-uniform in nature and hence a dynamic approach has been used to calculate buckling loads by adopting two sets of boundary conditions,one set for pre-buckling stress analysis and the second set for buckling analysis.Four different quasi-isotropic stacking sequences are deliberated in this work by varying different ply-orientation in each scheme.The study also addresses the effect of various parameters such as nonlinear loads,hygro-thermal loads,cutout size and shapes,position of cutout,stiffener parameters,stacking sequences,thickness of plate and boundary conditions.
文摘Gasturbines are provided with cut-outs for minimizing vibrations. Round cut-outs are usually favored but there are various designs which offer more advantages over the circular shape. The objective of this work was to compare stress reduction during the induced vibration in the hollow gas turbine shafts by introducing different cut-outs. Round, square and elliptical cut-outs under different orientations were compared. It is observed that a square cutout at 45°?orientation has the least stress concentration. This is due to the effective orientation of plastic strains along the principal axis.
文摘Stresses, particularly those at geometric discontinuities, influence the structural integrity of engineering components. Motivated by the prevalence of complicated-shaped perforated components, the objective of this paper is to demonstrate the ability to stress analyze loaded finite members containing asymmetrical, irregularly-shaped cutouts. Recognizing the difficulties in obtaining purely theoretical or numerical solutions for these situations, the paper presents an expeditious means of experimentally stress analyzing such structures. Processing the load-induced temperature information with a series representation of a stress function provides the independent stress components reliably full-field, including on the edge of a hole. The stresses satisfy equilibrium and strains satisfy compatibility. In addition to being able to stress analyze complicated shapes using real, rather than complex variables, the technique is significant in which it smooths the recorded thermal information, is widely applicable, and requires neither differentiating the measured data nor knowing the elastic properties or external boundary conditions. The latter is extremely important since the external loading is often unknown in practice. That the approach provides the independent stresses is also significant since fatigue analyses and strength criteria typically necessitate knowing the individual components of stress. Present results are supported by those from a finite element analysis, strain gage measurements and load equilibrium.
文摘BACKGROUND There are few studies in the literature comparing the clinical outcomes and radiographic results of proximal femoral nail(PFN)and proximal femoral nail antirotation(PFNA)for pertrochanteric femoral fracture(PFF)in elderly patients.AIM To evaluate both clinical and radiographic outcomes after fixation with PFN and PFNA in an elderly patient population.METHODS One hundred fifty-eight patients older than 65 years with PFF who underwent fixation with either PFN or PFNA were included.Seventy-three patients underwent fixation with PFN,whereas 85 were fixed with PFNA.The mean follow-up was 2.4 years(range,1-7 years).Clinical outcome was measured in terms of operation time,postoperative function at each follow-up visit,and mortality within one year.Radiographic evaluation included reduction quality after surgery,Cleveland Index,tip-apex distance(TAD),union rate,time to union,and sliding distance of the screw or blade.Complications including nonunion,screw cutout,infection,osteonecrosis of the femoral head,and implant breakage were also investigated.RESULTS Postoperative function was more satisfactory in patients who underwent PFNA than in those who underwent PFN(P=0.033).Radiologically,the sliding difference was greater in PFN than in PFNA patients(6.1 and 3.2 mm,respectively,P=0.036).The rate of screw cutout was higher in the PFN group;eight for PFN(11.0%)and two for PFNA patients(2.4%,P=0.027).There were no differences between the two groups in terms of operation time,mortality rate at one year after the operation,adequacy of reduction,Cleveland Index,TAD,union rate,time to union,nonunion,infection,osteonecrosis,or implant breakage.CONCLUSION Elderly patients with PFF who underwent PFNA using a helical blade demonstrated better clinical and radiographic outcomes as measured by clinical score and sliding distance compared with patients who underwent PFN.
文摘Based on Donnell's shallow shell equation, a new method is given in this paper to analyze theoretical solutions of stress concentrations about cylindrical shells with large openings. With the method of complex variable function, a series' of conformal mapping functions are obtained from different cutouts' boundary curves in the developed plane of a cylindrical shell to the unit circle. And, the general expressions for the equations of a cylindrical shell, including the solutions of stress concentrations meeting the boundary conditions of the large openings' edges, are given in the mapping plane. Furthermore, by applying the orthogonal function expansion technique, the problem can be summarized into the solution of infinite algebraic equation series. Finally, numerical results are obtained for stress concentration factors at the cutout's edge with various opening's ratios and different loading conditions. This new method, at the same time, gives a possibility to the research of cylindrical shells with large non-circular openings or with nozzles.
文摘In this study,the effect of influencing parameters on the stress distribution around a polygonal cutout within a laminated composite under uniform heat flux was analytically examined.The analytical method was developed based on the classical laminated plate theory and two-dimensional thermo-elastic method.A mapping function was employed to extend the solution of a perforated symmetric laminate with a circular cutout to the solution of polygonal cutouts.The effect of significant parameters such as the cutout angular position,bluntness and aspect ratio,the heat flux angle and the laminate stacking sequence in symmetric composite laminate containing triangular,square and pentagonal cutouts was studied.The Neumann boundary condition was used at the edges of the thermally insulated polygonal cutout.The laminate was made of graphite/epoxy(AS/3501) material with two different stacking sequences of [30/45]sand[30/0/-30]_(s).The analytical solutions were well validated against finite element results.
文摘The laws that natural frequencies of rectangular plate with a cutout will change with size and position of cutout are obtained by analytic, numerical and experimental methods.
基金the National Natural Science Foundation of China.
文摘Based on the motion equations of flexural wave in Ambartsumian' s plates including the effects of transverse shear deformations,by using perturbation method of small parameter,the scatter- ing of flexural waves and dynamic stress concentrations in the plate with a cutout have been studied. The asypmtotic solution of the dynamic stress problem is obtained.Numerical results for the dynamic stress concentration factor in Ambartsumian's plates with a circular cutout are graphically presented and discussed.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(2021B0301030001)the National Key Research and Development Program of China(2021YFA0716304)+3 种基金the project supported by the Space Utilization System of China Manned Space Engineering(KJZ-YY-WCL03)the National Key Laboratory Foundation of Science and Technology on Materials under Shock and Impact(6142902210109)Independent Innovation Projects of the Hubei Longzhong Laboratory(2022ZZ-32)the National Natural Science Foundation of China(Nos.11902232,51972246,and 51521001).
文摘Given the significant potential of multi-directional functionally graded materials(MFGMs)for customizable performance,it is crucial to develop versatile material models to enhance design optimization in engineering applications.This paper introduces a material model for an MFGM plate described by trigonometric functions,equipped with four parameters to control diverse material distributions effectively.The bending and vibration analysis of MFGM rectangular and cutout plates is carried out utilizing isogeometric analysis,which is based on a novel third-order shear deformation theory(TSDT)to account for transverse shear deformation.The present TSDT,founded on rigorous kinematics of displacements,is demonstrated to surpass other preceding theories.It is derived from an elasticity formulation,rather than relying on the hypothesis of displacements.The effectiveness of the proposed method is verified by comparing its numerical results with those of other methods reported in the relevant literature.Numerical results indicate that the structure,boundary conditions,and gradient parameters of the MFGM plate significantly influence its deflection,stress,and vibration frequency.As the periodic parameter exceeds four,the model complexity increases,causing result fluctuations.Additionally,MFGM cutout plates,when clamped on all sides,display almost identical first four vibration frequencies.
文摘In this paper, based on the theory of thick shells including effects of transverse shear deformations, a complex variables analytic method to solve stress concentrations in circular cylindrical shells with a small cutout is established A general solution and expression satisfying the boundary conditions on the edge of arbitrary cutouts are obtained. The stress problem can be reduced to the solution of an infinite algebraic equation series, and can be normalized by means of this method. Numerical results for stress concentration factors of the shell with a small circular and elliptic cutout are presented.
文摘In this paper a complex variable analytic method for solving stress concentrations in the circular cylindrical shell is proposed. The problem to be solved can be summarized into the solution of an infinite algebraic equation series. The solution can be normal and effective by means of this method. Numerical results for stress concentrations in the shell with a circular, elliptic cutout are graphically presented.
