주파수와 진폭에 따른 비선형 동특성 예측을 위한 현가장치 부시 모델에 대한 연구

현민수(Minsu Hyun),윤재민(Jaemin Yoon),이광우(Gwang-woo Lee),박순철(Sooncheol Park),강대오(Daeoh Kang),허승진(Seung-Jin Heo) 한국자동차공학회 2020 한국 자동차공학회논문집 Vol.28 No.9

In this paper, we study the modeling method for a suspension bush with frequency and amplitude-dependent nonlinear dynamic characteristics. The proposed bush model adds amplitude-dependent cells to the generalized Maxwell model, the most general form of force element model for viscoelasticity. A frictional Maxwell model is used as the amplitude-dependent cell in which the damper element is replaced with a friction element in the Maxwell model. We establish a parameter identification process for this bush model and apply it to the front Mcpherson suspension. To verify the accuracy of the proposed bush model at the system level, half-car durability simulation based on multibody dynamics is performed on the suspension model equipped with the bush model. The results are compared with the accuracy of the suspension model using the Kelvin-Voight model, which is commonly used as a bush model.

이상물체를 이용한 암반의 동결융해 Modeling

한희수(Han Heuisoo) 한국지반환경공학회 2010 한국지반환경공학회논문집 Vol.11 No.12

동절기에 암반의 절리면 내의 지하수의 동결 시 부피팽창으로 인해 절리면내 응력이 증가할 것이며, 융해 시 부피감소로 인해 응력이 감소되어 원상태로 회복된다. 동결융해과정이 지속적으로 반복되면서 발생되는 응력이력현상으로 인해 암반사면 내의 피로현상이 누적되면서 암반사면 절리면 내 누적 변위가 증가할 뿐만 아니라 전단강도 역시 지속적으로 감소될 것이다. 동결융해로 인한 응력의 이력현상은 대기의 온도의 영향에 의한 것으로, 일반적으로 점탄성 거동을 하게 된다. 그러므로, 일반적으로 점탄성 거동해석에 사용되는 Kelvin 모델을 적용할 수 있다. 동절기의 동결융해에 따른 암반사면의 거동을 해석하기 위하여, 계측깊이에 따라 얕은 절리면 깊이의 3지점과 깊은 절리면의 2지점으로, 총 5곳의 실측자료를 분석하였다. 얕은 절리면의 경우 많은 절리면을 가져, 다수의 Kelvin model이 연결된 상태이므로 거동이 복잡한 형태로 나타났다. 암반이 양호한 깊은 절리면의 경우 단순한 Kelvin model이 연결된 상태이므로, 절리면 거동이 단순한 형태로 나타남을 볼 수 있다. If the groundwater in rock joint is changed into ice, it induces the stress increment by volume increase. Also, if the ice is changed into groundwater again, the stress in joint decreases by volume decrease. The accumulated displacement and fatigues of joints are increased by the stress-hysterisis, induced from the continuous frost-thawing. Also the shear strength is decreased by them continuously. The stress-hysterisis is affected by the atmospheric temperature changes, whose behavior is visco-elasticity, usually. Therefore, Kelvin model could be used to analyze the frost-thawing behavior in winter. The measured data of total 5 points are examined, which are composed of 3 points of shallow joints and 2 points of deep joints. Because shallow weathered rocks have many joints, a lot of Kelvin model are connected and the behaviors are complicated. In case of deep joints, simple Kelvin model is applied and the behaviors are also simple.

Dimensional pounding response analysis for adjacent inelastic MDOF structures based on modified Kelvin model

Xuyong Chen,Xuehao Xiao,Xixuan Bai,Qiaoyun Wu 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.3

The dimensional analysis method is used to study the pounding response of two inelastic MDOF (multi-degree-offreedom) structures under simplified earthquake excitation. The improved Kelvin pounding model is adopted to simulate the force and deformation of the collisions during the contact process. The bilinear interstory resistance model is used to describe the inelastic characteristics of the MDOF structures. The expression of dimensionless pounding force and the equation of dimensionless motion during the collision process are derived. Based on the above theoretical derivation, the accuracy of the improved Kelvin model is verified by comparing the pounding responses in the form of spectra between the improved Kelvin model and Kelvin model. The effects of the pounding on the response of the left structure (with a smaller mass and stiffness) are analyzed in different trend (amplification region, suppression region and unaffected region), and the self-similarity of the pounding response for the two inelastic MDOF structures is revealed. The effects of the story mass ratio, post-yield stiffness ratio, yield displacement and structure spacing on the pounding response are studied. The peak displacement response of the left side structure increases with the increasing of story mass ratio and decreases with the increasing of yield displacement and postyield stiffness ratio. With the increasing of structure spacing, the peak displacement decreases in the first spectrum region, and in the second spectrum region, the peak displacement increases. Moreover, the change of the parameters has little effect on the response of the right structure (with a larger mass and stiffness).

교량 상부구조물의 탄성받침 설치에 따른 충돌특성 분석

최형석,김정우,공영이,정진환,김인태 한국지진공학회 2011 한국지진공학회논문집 Vol.15 No.4

지진하중으로 인해 교량상부구조 간에 발생하는 충돌은 교량상부구조의 낙교, 교각의 파괴와 같은 국부적인 손상뿐만 아니라 교량전체시스템의 붕괴를 유발할 수 있다. 이와 같은 충돌의 영향은 신축이음부의 재질, 형태 및 교대부의 여유간격과 관계가 있는 것으로 알려져 있다. 본 논문에서는 교량상부구조 간에 발생하는 충돌에 대한 특성을 분석하기 위해 충돌해석 이론 중 가장 널리 활용되고 있는 접합요소 접근법(Linear Spring Model, Kelvin-Voigt Model, Hertz Model)에 대해서 고찰 하고 이를 실험적으로 검증하기 위해 탄성받침이 설치된 교량상부구조를 모형화한 콘크리트 교량모델에 대한 진동대 실험을 실시하였다. 기존의 충돌모델을 적용한 이론 해는 실험결과와 잘 부합되지 못하였으며, 이에 본 논문에서는 충돌강성에 적절한 적용계수 ?? 를 이용하여 충돌 후 거동을 잘 모사할 수 있는 충돌강성 수준을 산출하였다. 충돌발생시 적절한 강성 및 재료의 동적특성, 충돌면의 형상 등에 따라 발생하는 충돌력의 크기가 달라지므로 이에 대한 추가적인 연구가 필요한 것으로 판단된다. Seismic structure pounding between adjacent superstructures may induce the destruction of pier and bridge superstructures and cause local damage that leads to the collapse of the whole bridge system. The pounding problem is related to the expansion of joints, gap distance and seismic response of the abutments. In this research, methods of the contact element approach, the linear spring model, the Kelvin-Voigt model and the Hertz model were studied to analyse the pounding characteristics. The shaking table test for a model specimen such as a bridge superstructure with elastomeric bearings was performed to evaluate the contact element approach methods. Relationships between the time history response from the numerical analysis results and the measured response from the shaking table test are compared. The experimental results were not well matched with the numerical analysis results using the existing pounding stiffness models. Therefore, in this study, coefficients are proposed to calculate the appropriate pounding stiffness ratio.

Dynamic analysis of sandwich plate with viscoelastic core based on an improved method for identification of material parameters in GHM viscoelastic model

Mojtaba Safari,Hasan Biglari,Mohsen Motezaker 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.6

In this paper, the dynamic response of a simply-supported composite sandwich plate with a viscoelastic core based on the Golla-Hughes-McTavish (GHM) viscoelastic model is investigated analytically. The formulation is developed using the three-layered sandwich panel theory. Hamilton's principle has been employed to derive the equations of motion. Since classical models, like kelvin-voigt and Maxwell models, cannot express a comprehensive description of the dynamic behavior of viscoelastic material, the GHM method is used to model the viscoelastic core of the plate in this research. The main advantage of the GHM model in comparison with classical models is the consideration of the frequency-dependent characteristic of viscoelastic material. Identification of the material parameters of GHM mini-oscillator terms is an essential procedure in applying the GHM model. In this study, the focus of viscoelastic modeling is on the development of GHM parameters identification. For this purpose, a new method is proposed to find these constants which express frequency-dependent behavior characterization of viscoelastic material. Natural frequencies and loss factors of the sandwich panel based on ESL and threelayered theories in different geometrics are described at 30°C and 90°C; also, the comparisons show that obtained natural frequencies are grossly overestimated by ESL theory. The argumentations of differences in natural frequencies are also illustrated in detail. The obtained results show that the GHM model presents a more accurate description of the plate's dynamic response by considering the frequency dependency behavior of the viscoelastic core.

Kelvin-Voigt Model for Dynamics of Crack Opening in Shrinkage Cracking

Tuk-Ki Min,Nhat Vo-Dai 대한토목학회 2008 KSCE JOURNAL OF CIVIL ENGINEERING Vol.12 No.3

According to an exhibition of clay soils consisting of not only elastic but also viscous properties, we present Kelvin-Voigt modelcombined by an elastic spring and a damper in parallel to investigate the dynamics of crack opening. The equation of motion of crackopening is derived mathematically from the equilibrium equation; that means the frictional shear stress is equal to the tension in thesoil. After obtaining the equation of motion, the experiments were carried out in laboratory on Kaolin to validate the proposed modelthrough cracks. The obtained experimental data were fitted results indicate that the proposed model yields a good correlation between the experiment data and the computed values with thefairly high coefficient of regression (=0.98). Therefore, it is concluded that the proposed Kelvin-Voigt model can be usedappropriately for describing the dynamics of crack opening in clays.

Material model for load rate sensitivity

Kozar, Ivica,Ibrahimbegovic, Adnan,Rukavina, Tea Techno-Press 2018 Coupled systems mechanics Vol.7 No.2

This work presents a novel model for analysis of the loading rate influence onto structure response. The model is based on the principles of nonlinear system dynamics, i.e., consists of a system of nonlinear differential equations. In contrast to classical linearized models, this one comprises mass and loading as integral parts of the model. Application of the Kelvin and the Maxwell material models relates the novel formulation to the existing material formulations. All the analysis is performed on a proprietary computer program based on Wolfram Mathematica. This work can be considered as an extended proof of concept for the application of the nonlinear solid model in material response to dynamic loading.

Equivalent Stiffness Modeling Method of a Battery System for Evaluating Vehicle Rear-End Collision Performance

이재준,김흥규,허승진,이상진 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.5

The battery system of a vehicle is critical for its good operation, and in the event of vehicle collision, damage to the parts or displacement of the battery can significantly affect performance. Nonlinear characteristics must be considered when designing elastic parts for vehicle’s collision analysis, and nonlinear dynamic finite element analysis simulations should be used to derive dynamic responses through collision simulations. Existing models examine the overall behavior without specifically configuring each part, and therefore, we need a model that can derive dynamic responses through collision simulations at the part level. Thus, we propose an equivalent stiffness model for a battery system to evaluate the vehicle’s rear-end collision performance in the early design stage. The model showed errors of 7.54 % and 6.12 % in the peak-to-peak values for the x-axis and z-axis acceleration responses, respectively, on the upper part of the battery; the root mean square value was within the margin of error. Simulation results confirmed that the proposed model is as accurate as the real vehicle test and nonlinear dynamic finite element analysis model. Thus, it can be used in the early design stage to predict system performance for collision test in a system whose geometry has not been determined.

Parametric study on earthquake induced pounding between adjacent buildings

Sadegh Naserkhaki,Farah N.A. Abdul Aziz,Hassan Pourmohammad 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.4

Pounding between closely located adjacent buildings is a serious issue of dense cities in the earthquake prone areas. Seismic responses of adjacent buildings subjected to earthquake induced pounding are numerically studied in this paper. The adjacent buildings are modeled as the lumped mass shear buildings subjected to earthquake acceleration and the pounding forces are modeled as the Kelvin contact force model. The Kelvin model is activated when the separation gap is closed and the buildings pound together. Characteristics of the Kelvin model are extensively explored and a new procedure is proposed to determine its stiffness. The developed model is solved numerically and a SDOF pounding case as well as a MDOF pounding case of multistory adjacent buildings are elaborated and discussed. Effects of different separation gaps, building heights and earthquake excitations on the seismic responses of adjacent buildings are obtained. Results show that the seismic responses of adjacent buildings are affected negatively by the pounding. More stories pound together and pounding is more intense if the separation gap is smaller. When the height of buildings differs significantly, the taller building is almost unaffected while the shorter building is affected detrimentally. Finally, the buildings should be analyzed case by case considering the potential earthquake excitation in the area.

Numerical study for nonlocal vibration of orthotropic SWCNTs based on Kelvin's model

Hussain, Muzamal,Naeem, Muhammad N.,Tounsi, Abdelouahed Techno-Press 2020 Advances in concrete construction Vol.9 No.3

This research deals with the study of the orthotropic vibrational features of single-walled carbon nanotubes according to Kelvin's model and to check the accuracy of the models, the results have been compared with earlier modeling/simulations. Obtaining rough approximations of the natural frequencies of CNTs using continuum equations are still a common procedure, even at high harmonics. The effects of different physical and material parameters on the fundamental frequencies are investigated for zigzag and chiral single-walled carbon nanotubes invoking Kelvin's theory. By using nonlocal Kelvin's model, the fundamental natural frequency spectra for two forms of single-walled carbon nanotubes (SWCNTs) have been calculated. The influence of frequencies with nonlocal parameters and bending rigidity are investigated in detail for these tubes. Computer software MATLAB is utilized for the frequencies of SWCNTs and current results shows a good stability with comparison of other studies.