Papers by Keyword: Dynamic Stiffness

Abstract: Elaboration analytical and computer modeling, changing dynamic parameters of short-term and long-term loaded nonlinearly deformable large-span spatial shell structures are investigated in this research paper. The proposed physical and geometrically nonlinear models of deformation and computational algorithms for solving dynamic problems are applied to assess the stress-strain state of smooth and ribbed spatial systems with variable stiffness caused by the accumulation of damage and the orthotropic structure reinforced by the ribs of the structures of the studied systems. The possibility of using the proposed method of accounting for variable dynamic stiffnesses in calculations for solving problems of dynamic strength and stability of spatial large-span shells of complex geometry is shown.

Abstract: This research investigated the effect of the thickness of adhesive to the stiffness (Young’s modulus) of adhesive butt joint at high strain rate loading. A split Hopkinson pressure bar (SHPB) test is used to obtain the stress-strain response of join specimen at strain rate of 530±10 s^-1. The joint is composed of aluminum adherend bonded by epoxy adhesive with 0.5, 1, 2, and 3 millimeter of thickness variation. The results show that the joint deformed elastically and the stiffness increases with the increase of adhesive thickness. However, the rate at which the stiffness increases with thickness decreases at thick adhesive layer. The facts of this research are important for the improvement of the crashworthiness of structure such as automobile structures.

Abstract: Floor impact sound is one noise in apartment houses that cannot be avoided. In order to reduce floor impact sound, a floating floor system using resilient materials has been generally applied. Floor impact sound insulation performance of the floating floor system is dependent on the physical property (dynamic stiffness) of resilient materials. This study investigated the effect of temperature changes on resilient materials used in the floating floor system and on dynamic stiffness. Ethylene vinyl acetate (EVA) and expanded polystyrene (EPS) were used as resilient materials, and dynamic stiffness was measured during three stages of temperature change condition. The measurement result showed that as the temperature decreased, dynamic stiffness also increased. This study also analyzed the effect of changes in outdoor temperature on the heavyweight impact sound level with respect to concrete buildings with wall slabs. The floor impact sound level tended to increase during the winter season, when the outdoor temperature was low.

Abstract: To avoid the influence of column vibration on machining precision, it is necessary to simulate the stiffness characteristics of the columns for CNC grinding machine, and to optimize the structure of the column by using sensitivity method. Based on structural characteristics of the grinding machine and structural characteristics of the columns, a finite element model is established to simulate and calculate the first-four models of the columns. In order to optimize the structure of the column, a sensitivity analysis is made to calculate the sensitivity of natural frequencies and mass of the column to each panel and ribbed plate. Considering a weighting factor and taking integrated natural frequency of the column as an optimization objective, the mass of the column as a constraint, an optimization equation is established. By a quadratic programming method, the parameter optimization of the column is got as follows: the mass decreased by 4%, integrated natural frequency increased by 2%. Dynamic stiffness of the column has been optimized by harmonic response analysis, the results showed that the largest column in the Z resonance peak reduced by 8.44%.

Abstract: The paper describes the possibility of using textile fibers (natural and synthetic) for the production of thermal insulation materials in the form of mats using in construction. The paper deals mainly with soft thermal insulation mats and the factors that affect the thermal insulation properties of the insulating material in its manufacture and subsequent incorporation into the structure.

Abstract: In this paper a model of the feed drive system with disturbance force for High Speed Cutting (HSC) linear motor machine is given. The dynamic stiffness for the proposed model is analysed. A simulation of the influence of some parameters on feed drive dynamic stiffness is performed with the simulation program MATLAB & SIMULINK. Correctness of the proposed model is verified with an experimental measurement of the dynamic stiffness of the feed drive on the prototype HSC linear motor machine (HSC 11).

Abstract: Floating floor structures installed with resilient materials are commonly used to reduce sound from floor impacts. Resilient materials minimize the transmission of vibrations by absorbing shock vibrations occurring on the upper part. The floor impact sound reduction performance of resilient materials is related to the dynamic stiffness, which is a physical characteristic of materials. However, the dynamic stiffness varies according to the increase in the loading time of the load that is installed on the upper part of resilient materials. The dynamic stiffness values increase with an increase in the loading time; an increased dynamic stiffness value decreases the vibration reduction effect. The present study focuses on a floor structure installed with resilient materials, and identifies the degree of reduction in floor impact sound insulation performance with the elapse of time. The insulation of sound from lightweight impact sound decreased with the elapse of time, whereas the heavyweight impact sound did not show significant changes.

Abstract: In order to improve the vibration isolation performance of engine mount, a new type of magneto-rheological semi-active mount with multiple inertia tracks is designed based on the existing magneto-rheological semi-active mount . The mechanical model is established according to the mount. The expression of the dynamic stiffness and damping lag angle is deduced, then the dynamic characteristics is simulated in the simulation software. At the same time, verify this model correct by the experiments.

Abstract: In the case of the column materials to determined, the lower natural frequency of column is determined by the number of coupling bolts and bolt arrangement. In this paper, by three-dimensional modeling software of Solidwork column model of hobbing is set up, then by using ANSYS finite element analysis software. The initial four order natural frequency to the different number of connection bolts and the different arrangement of bolt are respectively calculated. After the initial four order natural frequency are contrasted, we conclude that in the case of merely considering dynamic stiffness this study reach it is the most reasonable to select 8-12 bolts in the hobbing of YKQ31300, and different bolt arrangement of effects on the dynamic stiffness of the column is very small and can be ignored.

Abstract: Impact sound transmission loss is the ability of structure to absorb impact noise, which is formed by mechanical impulses (steps, falls). The impact noise is then spread to the elements connected to the floor structure, such as the ceiling and surrounding wall. Dynamic stiffness is one of the important parameters that affect the sound insulation of ceiling structures with floating floors. The article deals with the optimal design of acoustic insulation to the floor composition, combining different materials of various thicknesses with various characteristic properties.