Papers by Keyword: Dynamic Stress

Abstract: This paper presents dynamic analysis of rheological behavior of materials modeled as a body under stationary harmonic dynamic action.Excitation force is inertial, because of rotation of eccentric mass, applied directly to the Maxwell rheological body.Based on theoretical and experimental results are highlighted functions for defining both the energy dissipated as hysteresis loops in physical conditions of linear behavior of the components of the Maxwell model.In this context are represented the representative sets of curves that outlines the progress of dissipation made in relation with the dynamic system parameters.

Abstract: Safety assessment of railway axles is based on fatigue strength design. During the design overall lifetime, railway axles undergo a very high number of loading cycles under rotating bending. Due to safety and reliability reasons, fatigue strength design has to be very carefully evaluated. Both theoretical modelling and extensive experimental fatigue testing including full scale tests have to be performed, whereas such tests have to be performed correctly with a high precision. In the paper, problems of dynamic forces during fatigue tests of railway axles are pointed out. Though static calibration can be carried out with a very high precision, dynamic forces can cause a significant redistribution of static stresses along the axle. An example is given and discussed.

Abstract: By introducing joint element with thickness, the joint element with thickness and non-thickness element were used to simulate the contact relationship between the concrete face and cushion and joints, for a certain CFRD for the three dimensional nonlinear finite element static and dynamic calculation and analysis. The results show that: using joint element with thickness is a good way to simulate the contact relationship between the concrete face and cushion, improve panel stress; Compared with non-thickness element, joint element with thickness can improve the dynamic stress of the CFRD better.

Abstract: Through analyzing slide-zone loess porosity microstructure and quantitative analysis, the article can obtain the relation between variational characteristics of slide-zone loess porosity micro-structure and dynamic stress. Experimental results show that slide-zone loess microstructural parameters with load increasing appears a certain laws, and we can use simple linear equation to stand for the relation between porosity quantity or porosity area or porosity morphology ratio and dynamic stress. There is a negative correlation between porosity quantity and dynamic stress, but to other microstructural parameters and dynamic stress, it is a positive correlation. All of these laws are closely related to porosity transformation that forming under axial dynamic stress. It is worth mentioning that porosity fractal dimension with increasing dynamic stress increases, appearing linear correlation. When the confidence coefficient is 0.05, their correlation is well. Synthesizing above study, there is some guiding significance for establishing loess microstructure mechanical model and soil mass microstructural mechanics.

Abstract: Cellular material such as aluminium foam has been considered as a potential material for energy absorption upon impact and blast loadings. One of the most important properties that contribute to this feature is the densification strain. At high impact velocity, prediction of the densification strain from quasi-static engineering stress-strain curve has been found inadequate. Furthermore, theoretical prediction using the equation proposed by Reid et al. always over-predicts the dynamic crushing stress. Formation of the shock wave at high impact velocity is believed to further increase the densification level of the foam. However, this effect is disregarded when determining the densification strain quasi-statically. The present study aims to address this issue by determining the densification strain experimentally from impact tests. Forty cylindrical aluminium foams with three different lengths were used as projectiles and were fired towards a rigid load cell by using a gas gun. The peak forces generated from the impact were recorded and analysed. The experimental densification strains were determined physically by measuring the deformation of the foam projectiles after the tests. It is concluded that, at high impact velocity, the densification strain varies with the initial impact velocity. Therefore an appropriate value of densification strain needs to be used in the equation of dynamic crushing stress for a better approximation.

Abstract: The biggest problems of online monitoring stress for crane currently are the signal stability problem and the high cost problem. Aiming at these problems, the authors design the stability monitoring project for shipbuilding portal crane. The project adopts the wired monitoring method and the strain signal is amplified preliminarily at the measuring point, the combination of both which overcomes the problems of strain signal attenuation and electromagnetic interferences. The acquisition box is reset punctually to avoid the drift problem. An experiment of online monitoring stress for shipbuilding portal crane used for 5 years is done in a shipyard, and the experiment proves that the effective relative error is less than 6%. Compared with the wireless monitoring way, the project costs lower and isnt subject to electromagnetic interferences. Moreover, compared with the traditional wired monitoring way, the program has more stability signal.

Abstract: This paper describes the CMM main error sources and their classification, Dynamic error of flotation blocks vibration due to a single degree of freedom is for analysis, the use of the Navier - Stokes equations and mathematical modeling equations of Newtonian mechanics, the establishment of finite element model and simulation analysis, the movement of the coordinate measuring machine in the dynamic stress and deformation and vibration conditions for the design of coordinate measuring machine provides a new approach.

Abstract: The Fenwei Basin can be the most developed area of ground fissures as well as the associated geo-hazard in China and even in the world .Considering the ground fissure disasters influence on site condition, especially on the dynamic characteristics and dynamic response of site soil, in this paper, under the condition of constant pressure consolidation, consolidated undrained dynamic triaxial tests are carried on Xi'an area ground fissures belt loess with different confining pressures and dynamical parameters are obtained. Based on the experimental results, the dynamic stress-strain relationship, the change laws of dynamic shear modulus and damping ratio are analyzed. The equivalent visco-elastic constitutive model is also established.

Abstract: The deformation of railway embankment is strictly controlled to ensure the safety of train running. In order to study the engineering behavior of railway embankment, simulation analysis on railway embankment with height of 8 m was carried out. Dynamic loads with amplitudes of 0~50 kPa and 0~100 kPa were imposed. The deformation behavior and dynamic stress response of embankment were studied. The results show that the embankment presents attenuation effect on dynamic stress. The static earth pressure near the top of embankment is enhanced, and the static earth pressure at the bottom of embankment is released. The increase of train load will change the failure mode of embankment. The deformation mode of embankment is in subsidence mode when the amplitude of dynamic load is 0~50 kPa, and deformation mode turns sliding mode when amplitude is 0~100 kPa.

Abstract: Finite element model of helical gear meshing of large burden marine is built based on explicit dynamics finite element method, dynamics stress variation of helical gear tooth is simulated under multiple working conditions, research is focused on the impact of changes in working conditions on the dynamic stress of the tooth root. The results show that helical gear pair speed and center distance error have great impact on dynamic stress of tooth root. The results provide reference for dynamic performance optimization of marine gears.