Papers by Keyword: Contact Force

Abstract: Recent research on the progressive collapse of buildings has mainly focused on load redistribution following member failure, commonly referred to as “re-distributional progressive collapse”. However, “impact-type progressive collapse” remains less explored. This mechanism, often triggered by dynamic events such as falling debris or fire scenarios, introduces complex interactions that are difficult to capture using traditional quasi-static models, leaving a significant gap in our understanding of how impact-type progressive collapses occur. This study aims to bridge that gap by investigating the impact forces generated between concrete bodies of various geometries through an experimental campaign. Spherical, semi-spherical, and cubic concrete samples were dropped onto a fiber-reinforced concrete plate from controlled heights. A high-speed camera captured the impact for detailed analysis, while parameters such as impactor mass and velocity, contact radius, and concrete compressive strength were systematically varied. Using advanced data processing techniques, namely Variational Mode Decomposition (VMD), results showed that a 73% increase in impact velocity led to a 75% rise in maximum contact force. Geometry had a significant influence, with spherical and semi-spherical specimens generating up to 64% higher forces than cubes of equal mass. In contrast, compressive strength had a minor effect, raising contact force by only 9% despite a 50% strength increase. High-speed camera footage confirmed more concentrated impacts for spherical shapes, while no notable differences were found between spherical and semi-spherical specimens of equal weight but different contact radii.

Abstract: The variable pitch twin-screw vacuum pump has more advantage than the uniform pitch twin-screw vacuum pump. Its energy efficiency and volumetric compression ratio are specifically high. Under the cyclic gas pressure and working temperature, the rotors of vacuum pump often deform and interfere that lead to noise, vibration and rotor abrasion. In this paper, a 3D model of the variable pitch rotor generating by CNC turning process is constructed to reasonably estimate the rotor load and deformation in operation. The contact force have been analyzed to show the advantages of variable pitch rotors.

Abstract: In this paper, the influence of friction on static, dynamic characteristics, the strength and lifetime of a 3-axes flexible CNC machine tool are taken into account. The machine tool is first modelled by using finite element method (FEM) to perform static structural analysis. After that, the dynamic effects caused by the inertia forces and the displacement of moving part of the machine on contact stress are considered in this study. Then, the stress and contact force distributions on solid-flexible contact are also obtained. Finally, the influence of dynamic structure, cutting conditions and material properties on strength and lifetime of CNC machine tool are discussed by using fatigue analysis. Consequently, the proposed method can be used for efficient simulation of structural dynamics, lifetime assessment as well as interactions of the real CNC machine with the machine tool structure in a virtual environment.

Abstract: Space deployable mechanisms have been widely employed in aeronautic industry, and the dynamic performance of the space deployable mechanisms become increasingly important. In this paper, the model of space deployable mechanism with double clearances is established by the multi-body program ADAMS. The deployable mechanism with ideal joint, single clearance joint and double clearance joints are simulated to investigate the effects of double clearance on the dynamic performance of the deployable mechanism. The results reveal that the coupler of double joint clearance has significant influence on dynamic performance of deployable mechanism. The results of simulation could help to predict the joint vibration in space deployable mechanisms.

Abstract: The nonlinear behavior of a flapping-wing mechanism affected by revolute joint clearance is studied in this work. Considering the axial dimension of bearing, energy dissipation and the nonlinear power exponent from material, the nonlinear stiffness coefficient and an improved contact dynamic model in the joint clearance is established. A flapping-wing mechanism dynamic model with joint clearance is also established. Then embed the contact dynamic model and system dynamic model into the mechanical system simulation software package. From large numbers simulations performed, and the analysis of journal trajectories and Poincare maps under the different clearance sizes, it can be concluded that flapping-wing mechanism with joint clearance exhibit a chaotic response, and the more clearance size, the more obvious chaotic behavior.

Abstract: The matching status of wheel/rail affect the driving stability and safety directly. It could improve the dynamic behaviors by optimizing the matching status of wheel/rail. Taking the wheel rim tread named LMa as an object, the wheel diameter curve method was used to optimize the profile of tread LMa. Then the dynamic behaviors of the optimized profile (LMa-G) were obtained by the dynamic analysis. The results obtained indicate that the profile of tread LMa - G showing better contact performance.

Abstract: Elasticity variations in railway overhead contact line would lead to the fluctuation of contact force between pantograph and contact wire and produce a negative effect on the stability of current collection. Dropper distribution is one of the key factors affecting the elasticity of the contact wire. In this paper, the influence of dropper spacing on elasticity and quality of current collection have been studied using finite element analysis method by simulation. By analyzing the changes of elasticity value and contact force under different conditions of dropper distribution, the effect laws of dropper spacing on the contact wire elasticity and the quality of current collection under the speeds of 300km/h, 350km/h and 400km/h have been obtained.

Abstract: Kinetic characteristics of chain drive system were investigated in this paper and some corresponding mathematical models were established. In accordance with the theory of chain drive, based on the multi-body dynamics software platform, a dynamic analysis model of timing bushing chain system for diesel engine was established. Chain tension force, chain contact force and chain fluctuation in a rotation cycle at different running speeds were analyzed. By analysis and evaluation these results, the kinematic and dynamic characteristics of the chain drive system during the operation could be effectively recognized, this research results can provide a basis for production tests.

Abstract: In the present paper, the problem on normal low-velocity impact of a solid upon an isotropic spherical shell is studied without considering the changes in the geometrical dimensions of the contact domain. At the moment of impact, shock waves (surfaces of strong discontinuity) are generated in the target, which then propagate along the shell during the process of impact. Behind the wave fronts up to the boundary of the contact domain, the solution is constructed with the help of the theory of discontinuities and one-term ray expansions. The ray method is used outside the contact spot, but the Laplace transform method is applied within the contact region. It is assumed that the viscoelastic features of the shell are exhibited only in the contact domain, while the remaining part retains its elastic properties. In this case, the contact spot is assumed to be a plane disk with constant radius, and the viscoelastic features of the shell are described by the fractional derivative standard linear solid model. In the case under consideration, the governing differential equations are solved analytically by the Laplace transform technique. As a result, the exact solution of the contact force is determined as a function of time.

Abstract: Due to increasing traffic on long span bridges, behavior of expansion joints is believed to be largely influenced by pounding impact from passing vehicles. In order to precisely understand behavior of expansion joint under vehicle impact loading, a new analysis scheme is proposed which incorporates interaction between vehicle and expansion joint. Mathematical model of vehicle is established and solved with Newmark method. Expansion joint is modeled with refined solid element in Finite element software ABAQUS. The analysis indicates that vehicle loading can induce large dynamic response of expansion joint in long span bridges.