Free Vibration Analysis of Rectangular Plate with Cutouts under Elastic Boundary Conditions in Independent Coordinate Coupling Method

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.

Free Vibration Analysis of Functionally Graded Plates with Multiple Circular and Non-circular Cutouts

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.

Effects of Boundary Conditions on Postbuckling Strengths of Composite Laminate with Various Shaped Cutouts under In-Plane Shear

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.

Mechanical Buckling Analysis of Composite Panels with/without Cutouts

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.

基于Cutout-ResNet50的野外环境水稻病害识别系统

针对水稻病害图像在野外环境下存在的光照不均、明暗变化明显、因遮挡导致目标特征缺失和噪声重叠,以及野外环境的水稻数据集少且质量差等问题,提出一种基于改进ResNet50算法的野外环境水稻病害识别方法,并设计识别系统.在传统ResNet50算法的基础上采用迁移学习技术对学习知识跨领域迁移,缓解数据集样本不足和不均衡造成的过拟合现象;利用Cutout增强方法对特征信息随即筛选,模拟复杂的野外环境,加强算法的泛化能力;对学习率采用余弦退火优化策略,提高算法的稳定性.结果表明:改进的ResNet50算法在小型水稻病害数据集上的识别准确率达97.24%,明显高于传统ResNet50算法,且该改进方法亦能提升VGG16、GoogLeNet和MobileNetV3-large等其他卷积神经网络算法的模型识别性能.将该模型部署于系统,可为水稻病害识别在实际应用工程中的发展提供技术参考.

Special hybrid stress element for stress analyses around circular cutouts in laminated composites

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.

Experimental and numerical investigation of buckling in rectangular steel plates with groove-shaped cutouts

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.

Influence of local stiffeners and cutout shapes on the vibration and stability characteristics of quasi-isotropic laminates under hygro-thermo-mechanical loadings

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.

Analysis on the Effects of Cut-Outs in Hollow Inconel 718 Gas Turbine Shafts

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.

Thermoelastic Stress Analysis of a Finite Structure Containing an Asymmetrical-Oriented, Arbitrarily-Shaped Hole

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.

Does proximal femoral nail antirotation achieve better outcome than previous-generation proximal femoral nail?

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.

STRESS CONCENTRATIONS IN CYLINDRICAL SHELLS WITH LARGE OPENINGS

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.

The Effect of Cutout on Natural Frequencies of Thin Plate

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.

DYNAMIC STRESS CONCENTRATIONS IN AMBARTSUMIAN'S PLATE WITH A CUTOUT

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.

Thermal stress distribution around a thermally-insulated polygonal cutout in graphite/epoxy composite laminates under heat flux

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.

ON THE STRESS CONCENTRATION IN THICK CYLINDRICAL SHELLS WITH AN ARBITRARY CUTOUT

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.

THE GENERAL SOLUTION FOR THE STRESS PROBLEM OF CIRCULAR CYLINDRICAL SHELLS WITH AN ARBITRARY CUTOUT

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.

Efficient Video Cutout by Paint Selection

Video cutout refers to extracting moving objects from videos, which is an important step in many video editing tasks. Recent Mgorithms have limitations in terms of efficiency interaction style and robustness. This paper presents a novel method for progressive video cutout with less user interaction and fast feedback. By exploring local and compact features, an optimization is constructed based on a graph model which establishes spatial and temporal relationship of neighboring patches in video frames. This optimization enables an efficient solution for progressive video cutout using graph cuts. Furthermore, a sampling-based method for temporally coherent matting is proposed to further refine video cutout results. Experiments demonstrate that our video cutout by paint selection is more intuitive and efficient for users than previous stroke-based methods, and thus could be put into practical use.

Unsteady separation of jet branch by cutout of rotating Pelton bucket

As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bucket unsteadily separates a free jet into two branches in both space and time:the impinging branch landing on the relevant bucket surface,and the flow-off branch separated by the cutout toward the preceding bucket.In order to investigate the unsteady jet separation by the cutout three-dimensionally,a semicircular free jet was discretized into 641 nodes of boundary-fitted grids.The position P of impinging jet branch landing on the bucket surface was acquired with the relative velocity W and the water depth D at each node.The trailing edge surface of the flow-off jet branch was simultaneously computed unsteadily.The complicate unsteady interaction of the bucket cutout with the branched free jets was clarified visually with the 3D view of illustrations in order to research the unsteady hydraulic performance of Pelton turbines in space and time.