반강성 이론을 적용한 목재 볼트 결합부의 거동 해석

이전제 서울대학교 농업개발연구소 2000 농업생명과학연구 Vol.4 No.-

Attempts were made to analyze the behavior of single and multiple-bolted connections through theoretical methods such as European yield theory, empirical approaching method, and semi-rigid theory instead of many experimental methods that have been actually inefficient and non-economical. In the case of a single-bolted connection, if accurate characteristic values of a material could be guaranteed, it would be more convenient and economical to perform the behavior analysis using a model based on the semi-rigid theory, instead of the existing complex yield model, or the empirical formula which produces errors, giving different results from the actual ones. If the variables of equation determining the load and deformation could be appropriately controlled, the analytical method in conjunction with a semi-rigid theory could be effectively applied to obtain the desirably predicted value, considering that the appropriate solution could be derived through a simpler equation using a less difficult method compared to the existing yield model. It is concluded that analytical method with semi-rigid theory can be used in the behavior analysis of bolted connection because our developed method showed excellent analysis ability of behavior until number of bolt is two. Although our analytical method has the disadvantage that the number of bolt is limited to two, it is concluded that it has the advantage than numerical method which complicated and time-consuming.

Sensitivity analysis based on complex variables in FEM for linear structures

Azqandi, Mojtaba Sheikhi,Hassanzadeh, Mahdi,Arjmand, Mohammad Techno-Press 2019 Advances in computational design Vol.4 No.1

One of the efficient and useful tools to achieve the optimal design of structures is employing the sensitivity analysis in the finite element model. In the numerical optimization process, often the semi-analytical method is used for estimation of derivatives of the objective function with respect to design variables. Numerical methods for calculation of sensitivities are susceptible to the step size in design parameters perturbation and this is one of the great disadvantages of these methods. This article uses complex variables method to calculate the sensitivity analysis and combine it with discrete sensitivity analysis. Finally, it provides a new method to obtain the sensitivity analysis for linear structures. The use of complex variables method for sensitivity analysis has several advantages compared to other numerical methods. Implementing the finite element to calculate first derivatives of sensitivity using this method has no complexity and only requires the change in finite element meshing in the imaginary axis. This means that the real value of coordinates does not change. Second, this method has the lower dependency on the step size. In this research, the process of sensitivity analysis calculation using a finite element model based on complex variables is explained for linear problems, and some examples that have known analytical solution are solved. Results obtained by using the presented method in comparison with exact solution and also finite difference method indicate the excellent efficiency of the proposed method, and it can predict the sustainable and accurate results with the several different step sizes, despite low dependence on step size.

Semi-Analytical Methods for Different Problems of Diffraction-Radiation by Vertical Circular Cylinders

Malenica, Sime Korean Society of Ocean Engineers 2012 International journal of ocean system engineering Vol.2 No.2

As in the other fields of mechanics, analytical methods represent an important analysis tool in marine hydrodynamics. The analytical approach is interesting for different reasons : it gives reference results for numerical codes verification, it gives physical insight into some complicated problems, it can be used as a simplified predesign tool, etc. This approach is of course limited to some simplified geometries (cylinders, spheres, ...), and only the case of one or more cylinders, truncated or not, will be considered here. Presented methods are basically eigenfunction expansions whose complexity depends on the boundary conditions. The hydrodynamic boundary value problem (BVP) is formulated within the usual assumptions of potential flow and is additionally simplified by the perturbation method. By using this approach, the highly nonlinear problem decomposes into its linear part and the higher order (second, third, ...) corrections. Also, periodicity is assumed so that the time dependence can be factorized i.e. the frequency domain formulation is adopted. As far as free surface flows are concerned, only cases without or with small forward speed are sufficiently simple to be solved semi-analytically. The problem of the floating body advancing in waves with arbitrary forward speed is far more complicated. These remarks are also valid for the general numerical methods where the case of arbitrary forward speed, even linearized, is still too difficult from numerical point of view, and "it is fair to say that there exists at present no general practical numerical method for the wave resistance problem" [9], and even less for the general seakeeping problem. We note also that, in the case of bluff bodies like cylinders, the assumptions of the potential flow are justified only if the forward speed is less than the product of wave amplitude with wave frequency.

A semi-analytical method of time-varying mesh stiffness in concentric face gear split-torque transmission system

Jianxiong Dong,Jin-Yuan Tang,Zehua Hu,Yi Wang 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

Concentric face gear split-torque transmission system (CFGSTTS) has great applied value in the field of aeronautical transmission due to the characteristic of high integration. Mesh stiffness, as one of the most primary sources of vibration, is vitally important for the dynamic performances of gear transmission system. The existing finite element method (FEM) and analytical method (AM) are not suitable for tackling the mesh stiffness calculation of closed-loop multi-branch system such as CFGSTTS. Thus, a semi-analytical method (SAM) is presented and verified, which combines the high precision of FEM with the high efficiency of AM. Additionally, the differences between the mesh stiffness of independent face gear drive and that of the same gear pair in CFGSTTS under accordant load is researched by applying SAM. The influence rules of distribution angle and load condition on the mesh stiffness of gear pairs considering system structure are also studied. Results demonstrate that the mesh stiffness of gear pairs in CFGSTTS is time-varying and tends to be consistent with each other by adjusting load parameters.

보조변수법과 복소변수를 연동한 설계 민감도 해석 연구

김현기(Hyungi Kim),조맹효(Maenghyo Cho) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

Among various sensitivity evaluation techniques, semi-analytical method is quite popular since this method is more advantageous than analytical method and global finite difference method. However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, the adjoint variable method combined with complex variable is proposed to obtain the shape and size sensitivity for structural optimization. The complex variable can present accurate results regardless of the perturbation size as well as easy to be implemented. Through a few numerical examples of the static problem for the structural sensitivity, the efficiency and reliability of the adjoint variable method combined with complex variable is demonstrated.

멀티스테이지 호모토피 섭동법을 이용한 얕은 정현형 아치의 근사-해석적 해

손수덕(Shon, Su-Deok),이승재(Lee, Seung-Jae) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.4

The purpose of this study is to investigate the applicability of multistage homotopy perturbation method (MHPM) to shallow sinusoidal arches in order to obtain a semi-analytical solution. For this research purpose, a nonlinear governing equation of the arches was formulated and a homotopy equation was derived using the formulated differential equation. The result of a dynamic analysis on a symmetric mode and an asymmetric one was compared with the classical homotopy perturbation method and the 4<SUP>th</SUP> order Runge-Kutta method. From the comparison results, it was found that the dynamic response by MHPM concurred with the numerical results. Besides, the pattern of the response and the attractor by semi-analytical solution could delineate the dynamic snapping of the arches under excitations, and the attraction of the model in consideration of damping reflected the convergence and asymptotic stability well.

Cut geometry calculation for the semifinish five-axis milling of nonstraight staircase workpieces

Hendriko Hendriko 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3

The cut geometry prediction, especially the issue regarding computational time, of a complex part surface in five-axis milling remains as a challenge. In this study, the analytical boundary method, which was developed to predict the cut geometry during semifinish milling, was extended by adding a curve boundary algorithm. The extended algorithm made the method applicable not only for workpieces with a straight staircase profile but also for those with a nonstraight one. The proposed method was tested using two parts with different surface shapes. Results demonstrated that the proposed method is applicable for defining instantaneous cut geometry. The verification test proved that the method was accurate when the engagement point was on the top and straight wall surfaces. Relatively small errors were observed when the engagement point was on the nonstraight surface. Moreover, the test on computational time verified the efficiency of the developed method.

A semi-analytical mesh-free method for 3D free vibration analysis of bi-directional FGP circular structures subjected to temperature variation

Mahnaz Shamshirsaz,Shahin Sharafi,Javad Rahmatian,Sajad Rahmatian,Naserodin Sepehry 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.4

In this present paper, a semi-analytical mesh-free method is employed for the three-dimensional free vibration analysis of a bi-directional functionally graded piezoelectric circular structure. The dependent variables have been expanded by Fourier series with respect to the circumferential direction and have been discretized through radial and axial directions based on the mesh-free shape function. The current approach has a distinct advantage. The nonlinear Green-Lagrange strain is employed as the relationship between strain and displacement fields to observe thermal impacts in stiffness matrices. Nevertheless, high order terms have been neglected at the final steps of equations driving. The material properties are assumed to vary continuously in both radial and axial directions simultaneously in accordance with a power law distribution. The convergence and validation studies are conducted by comparing our proposed solution with available published results to investigate the accuracy and efficiency of our approach. After the validation study, a parametric study is undertaken to investigate the temperature effects, different types of polarization, mechanical and electric boundary conditions and geometry parameters of structures on the natural frequencies of functionally graded piezoelectric circular structures.

An integral equation formalism for solving the nonlinear Klein-Gordon equation

Elsevier [etc.] 2014 Applied Mathematics and Computation Vol.243 No.-

In the paper, a new method for solving the nonlinear Klein-Gordon equation is proposed. To this end, the nonlinear partial differential equation of Klein-Gordon is transformed into an equivalent non-linear integral equation through a transformation. Here, a hyperbolic type of Green's function is newly incorporated into the transformation in such a way that nonlinearities due to large wave motion are effectively taken into account. Based on the equivalent integral equation, a functional iteration procedure is constructed for solving the equation. The method proposed here is a semi-analytical one, not only fairly simple but straightforward to apply. Mathematical analysis is performed on the method's convergence and uniqueness. An illustrative example of a solitary wave (or soliton) is presented to investigate the validity of the method, resulting in numerical solutions, appearing to be higher accurate compared to the usual 2nd order centered difference scheme in a stable manner. In fact, just a few iterations are enough for the numerical solution.

Component method model for predicting the moment resistance, stiffness and rotation capacity of minor axis composite seat and web site plate joints

Aleksander Kozlowski 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.3

Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics (<i>M</i>-<i>φ</i>relationship), or at least three basic joint properties, namely the moment resistance <i>M_R</i>, the rotational stiffness <i>S_j</i> and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance <i>M_R</i>, initial stiffness <i>S_j.ini</i> and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.