Nonlinear Dynamic Responses of Shear-Deformable Composite Panels under Combined Supersonic Aerodynamic, Thermal, and Random Acoustic Loads

이홍범,김영남,최인준,박재상,김인걸 한국항공우주학회 2020 International Journal of Aeronautical and Space Sc Vol.21 No.3

The skin panel structures of vehicles in supersonic flights are subjected to combined thermal, acoustic, and aerodynamic loads. These combined loads may cause a nonlinear dynamic response of the high-speed flight vehicle’s panel structures. Among these nonlinear dynamic responses, the snapthrough and limit cycle oscillation response seriously affect the fatigue failure of the panel structures. This work investigates the nonlinear dynamic responses using the numerical method, when combined supersonic aerodynamic, thermal, and random acoustic loads are applied to the panel structures simultaneously. To consider the thin and thick composite panels, the first-order shear deformation plate theory (FSDT) and the von Karman nonlinear displacement–strain relationship are applied. The aerodynamic load in the supersonic flow is modeled using the first-order piston theory. The thermal load distribution is assumed constant in the thickness direction of the composite panel. The random acoustic load is represented as stationary white-Gaussian random pressure with zero mean and uniform magnitude over the panels. The nonlinear equations of motion of the composite panel under combined loads are derived using the principle of virtual work and the finite element method. The static displacement, which is the solution of the nonlinear static equation, is calculated using the Newton–Raphson method, and the nonlinear dynamic equation is solved using the Newmark-β time integration method. Using these numerical methods, the nonlinear dynamic analyses are conducted under various loading conditions such as thermal–random acoustic loads, thermal–supersonic aerodynamic loads, and supersonic aerodynamic–thermal–random acoustic loads. Numerical results show the nonlinear dynamic response of the composite thin and thick panels such as snapthrough and limit cycle oscillation responses. Particularly, the snapthrough response is caused when the random acoustic load is applied appropriately to the thermally buckled composite plate when the aerodynamic load is not applied or applied with the relatively small magnitude of the dynamic pressure.

Noise reduction for fatigue crack growth test data under random loading

Choi, J.M.,Kim, C.Y.,Song, J.H. Elsevier Sequoia 2009 Materials science & engineering. properties, micro Vol.505 No.1

The noise included in electrical signal significantly influences on the estimating results of crack length and crack opening point. The noise can be effectively reduced by averaging some consecutive loading cycles without distortion of the signal for constant amplitude loading tests, whereas the averaging technique cannot be applied to random loading tests due to the variation of load. In this study, a noise reduction technique was developed by using a load-based averaging technique, which can be applied to fatigue crack growth test data under random loading. Additionally, the developed noise reduction method was applied to random loading test data to verify the effectiveness of the method.

미소균열과 긴균열의 랜덤하중하의 피로균열진전과 닫힘거동

김정엽(Chung Youb Kim),송지호(Ji Ho Song),이신영(Shin Young Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Crack growth and closure behavior of physically short and conventionally long cracks under random loading are extensively investigated, utilizing test results of 2024-T351 aluminum alloy obtained by performing narrow and wide band random loading tests for various stress ratios and random loading block lengths. Crack growth rates are analyzed mainly in terms of the stress intensity factor range estimated by 2/PI correction proposed by Donald and Paris. The long and short cracks are very different in characteristics of closure behavior under random loading. Crack growth of short and long cracks under random loading can be well described by the crack closure concept. The effects of random spectrum or random block length on crack opening load and crack growth are not significant.

랜덤하중에서의 균열전파속도 추정법에 관한 연구

표동근(D. K. Pyo),안태환(T. H. An) 한국해양공학회 1994 韓國海洋工學會誌 Vol.8 No.2

Under variable amplitude loading conditions, retardation or accelerated condition of fatigue crack growth occurs with every cycle, Because fatigue crack growth behavior varied depend on load time history.<br/> The modeling of stress amplitude with storm loading acted to ships and offshore structures applied this paper.<br/> The crack closure behavior examine by recording the variation in load-strain relationship. By taking process mentioned above, fatigue crack growth rate, crack length, stress intensity factor, and crack closure stress intensity factor were obtained from the stress cycles of each type of storm : A(6m), B(7m), C(8m), D(9m), E(11m) and F(15m) which was wave height.<br/> It showed that the good agreement with between the experiment results and simulation of storm loads.<br/> So this estimated method of crack propagtion rate gives a good criterion for the safe design of vessels and marine structure.

Experiment study of structural random loading identification by the inverse pseudo excitation method

Guo, Xing-Lin,Li, Dong-Sheng Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.18 No.6

The inverse pseudo excitation method is used in the identification of random loadings. For structures subjected to stationary random excitations, the power spectral density matrices of such loadings are identified experimentally. The identification is based on the measured acceleration responses and the structural frequency response functions. Numerical simulation is used in the optimal selection of sensor locations. The proposed method has been successfully applied to the loading identification experiments of three structural models, two uniform steel cantilever beams and a four-story plastic glass frame, subjected to uncorrelated or partially correlated random excitations. The identified loadings agree quite well with actual excitations. It is proved that the proposed method is quite accurate and efficient in addition to its ability to alleviate the ill conditioning of the structural frequency response functions.

Random vibration of multispan Timoshenko frames due to a moving load

Wang, Rong-Tyai,Lin, Jin-Sheng Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.6

In this paper, an analytic method to examine the random vibration of multispan Timoshenko frames due to a concentrated load traversing at a constant velocity is presented. A load's magnitude is a stationary process in time with a constant mean value and a variance. Two types of variances of this load are considered: white noise process and cosine process. The effects of both velocity and statistical characteristics of load and span number of the frame on both the mean value and variance of deflection and moment of the structure are investigated. Results obtained from a multispan Timoshenko frame are compared with those of a multispan Bernoulli-Euler frame.

Vibratory loads and response prediction for a high-speed flight vehicle during launch events

Jinhyeong Kim,Seoryong Park,Wonjong Eun,Sangjoon Shin,Soogab Lee 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.4

High-speed flight vehicles (HSFVs) such as space launch vehicles and missiles undergo severe dynamic loads which are generated during the launch and in in-flight environments. A typical vehicle is composed of thin plate skin structures with high-performance electronic units sensitive to such vibratory loads. Such lightweight structures are then exposed to external dynamic loads which consist of random vibration, shock, and acoustic loads created under the operating environment. Three types of dynamic loads (acoustic loads, rocket motor self-induced excitation loads and aerodynamic fluctuating pressure loads) are considered as major components in this study. The estimation results are compared to the design specification (MIL-STD-810) to check the appropriateness. The objective of this paper is to study an estimation methodology which helps to establish design specification for the dynamic loads acting on both vehicle and electronic units at arbitrary locations inside the vehicle.

Vibratory loads and response prediction for a high-speed flight vehicle during launch events

Kim, Jinhyeong,Park, Seoryong,Eun, Wonjong,Shin, Sangjoon,Lee, Soogab The Korean Society for Aeronautical and Space Scie 2016 International Journal of Aeronautical and Space Sc Vol.17 No.4

High-speed flight vehicles (HSFVs) such as space launch vehicles and missiles undergo severe dynamic loads which are generated during the launch and in in-flight environments. A typical vehicle is composed of thin plate skin structures with high-performance electronic units sensitive to such vibratory loads. Such lightweight structures are then exposed to external dynamic loads which consist of random vibration, shock, and acoustic loads created under the operating environment. Three types of dynamic loads (acoustic loads, rocket motor self-induced excitation loads and aerodynamic fluctuating pressure loads) are considered as major components in this study. The estimation results are compared to the design specification (MIL-STD-810) to check the appropriateness. The objective of this paper is to study an estimation methodology which helps to establish design specification for the dynamic loads acting on both vehicle and electronic units at arbitrary locations inside the vehicle.

Hybrid Model for Renewable Energy and Load Forecasting Based on Data Mining and EWT

Zhang Jinjin,Zhang Qian,Li Guoli,Wu Junjie,Wang Can,Li Zhi 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.3

Accurate renewable resource (RES) and load prediction play key roles in the power grid planning schemes, eff ective dispatch, and stable operation of power systems. The proportions of wind and solar energy continue to increase, leading to wind and light abandonment. Thus, the absorption of wind and photovoltaic power is particularly important. On the basis of accurately predicting load, wind power and photovoltaic output, the accommodation capacity of wind and photovoltaic power is analyzed. The work contains fi ve parts, as follows: (1) empirical wavelet transform (EWT) is used to decompose wind power and load. At the same time, isolated forest (iForest) and fuzzy C-means clustering (FCM) are used to process photovoltaic data. (2) Low frequency and intermediate frequency components of load are predicted by improved random forest (IRF). High frequency component of load is clustered by improved density-based spatial clustering of applications with noise (IDBSCAN). The processing model is selected on the basis of the characteristics of each class sample. Each component of wind power are predicted by IRF. (3) Photovoltaic power of each category is predicted by IRF. (4) Diff erent components of load and wind power data are added. The photovoltaic power forecast data are synthesized according to the time point. (5) The forecast value of load, wind power, and photovoltaic output of a city are comprehensively evaluated by the summarized prediction level indicators. Three accommodation indicators are used for analyzing the accommodation capacity of wind power and photovoltaic. Results show that the forecasting methods of load, wind power, and photovoltaic power can generate better forecasting results than conventional methods. The analysis results of supplementary prediction level and accommodation indices provide reference for eff ective grid dispatching, sustainable, and healthy energy development.

Research on Calculation Method of Suspension Bridge Internal Force under Random Traffic Load

Pengfei Wu,Zhichun Fang,Xue Wang,Renyuan Wang,Qiang Xu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.11

Suspension bridge is a flexible structure. The weight, location and number of traffic on the bridge will affect the geometric alignment of the bridge. Although the finite element software can analyze the geometric nonlinearity of the bridge, the calculation of random load combination in finite element software is huge. In this paper, based on the deformation coordination, static equilibrium and constitutive model of the bridge, the force expression considering the geometric nonlinearity of the bridge is derived. Finite element software is used to simulate the internal force of components of suspension bridge under train load and vehicle load. The accuracy is verified by comparing the finite element results. Considering the random number of traffics, the random location of traffics, and the random weight of traffics, this paper analyzes the stress state of bridge under the random process of train load and vehicle load respectively. The method in this paper can be well used to analyze the actual stress state of the bridge, and provide a theoretical basis for related calculations.