Effect of softening of cement asphalt mortar on vehicle operation safety and track dynamics
16 Dec 2015-Journal of Zhejiang University Science (Zhejiang University Press)-Vol. 16, Iss: 12, pp 976-986
TL;DR: In this paper, a 3D coupling dynamic model of a vehicle and a China railway track system I (CRTS-I) slab track is developed to study the effect of CAM softening on track damage.
Abstract: Cement asphalt mortar (CAM) softening is a common phenomenon that results from aging and rain soaking when a high-speed railway is in service. CAM softening seriously affects vehicle operation safety and track dynamics. In this paper, a 3D coupling dynamic model of a vehicle and a China railway track system I (CRTS-I) slab track is developed. By using the proposed model, the wheel-rail contact forces, derailment coefficient, wheelset loading reduction ratio, and the track displacements are calculated to study the influences of CAM softening on the dynamic characteristics of a vehicle-track system. A track-subgrade finite difference model is developed to study the effect of CAM softening on track damage. The results show that track interface shear failure develops when the CAM softening coefficients reach 10–100. The CAM softening coefficient should not be less than 1000, otherwise a high-speed running vehicle may risk derailment.
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References
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TL;DR: In this paper, a comparison of alternative Creep Force Models for rail vehicle dynamic analysis is presented, and the results show that the alternative models are less accurate than the original models in terms of acceleration and acceleration.
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TL;DR: A new simple explicit two-step method and a new family of predictor–corrector integration algorithms are developed for use in the solution of numerical responses of dynamic problems, avoiding solving simultaneous linear algebraic equations in each time step.
Abstract: A new simple explicit two-step method and a new family of predictor–corrector integration algorithms are developed for use in the solution of numerical responses of dynamic problems. The proposed integration methods avoid solving simultaneous linear algebraic equations in each time step, which is valid for arbitrary damping matrix and diagonal mass matrix frequently encountered in practical engineering dynamic systems. Accordingly, computational speeds of the new methods applied to large system analysis can be far higher than those of other popular methods. Accuracy, stability and numerical dissipation are investigated. Linear and nonlinear examples for verification and applications of the new methods to large-scale dynamic problems in railway engineering are given. The proposed methods can be used as fast and economical calculation tools for solving large-scale nonlinear dynamic problems in engineering.
337 citations
"Effect of softening of cement aspha..." refers methods in this paper
...The vehicle-track coupling system equations are solved by means of a new explicit integration method (Zhai, 1996)....
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TL;DR: In this article, a three-dimensional finite element model was proposed to investigate the interface damage occurred between prefabricated slab and CA (cement asphalt) mortar layer in the China Railway Track System (CRTS-II) slab track system.
Abstract: This paper presents a three-dimensional finite element model to investigate the interface damage occurred between prefabricated slab and CA (cement asphalt) mortar layer in the China Railway Track System (CRTS-II) slab track system. In the finite element model, a cohesive zone model with a non-linear constitutive law is introduced and utilized to model the damage, cracking and delamination at the interface. Combining with the temperature field database obtained from the three-dimensional transient heat transfer analysis, the interface damage evolution as a result of temperature change is analyzed. A three-dimensional coupled dynamic model of a vehicle and the slab track is then established to calculate the varying rail-supporting forces which are utilized as the inputs to the finite element model. The non-linearities of the wheel–rail contact geometry, the wheel–rail normal contact force and the wheel–rail tangential creep force are taken into account in the model. Setting the maximum interface damaged state calculated under temperature change as the initial condition, the interface damage evolution and its influence on the dynamic response of the slab track are investigated under the joint action of the temperature change and vehicle dynamic load. The analysis indicates that the proposed model is capable of predicting the initiation and propagation of cracks at the interface. The prefabricated slab presents lateral warping, resulting in severe interface damage on both the sides of the slab track along the longitudinal direction during temperature drop process, while the interface damage level does not change significantly under vehicle dynamic loads. The interface damage has great effects on the dynamic responses of the slab track.
157 citations
"Effect of softening of cement aspha..." refers background in this paper
...Zhu and Cai (2014) investigated interface damage and its effect on vibrations of a slab track under different temperature and vehicle dynamic loads....
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TL;DR: Based on the theory of vehicle-track coupling dynamics, a new wheel/rail spatially dynamic coupling model is established in this article, in which the assumption that wheel contacts rail rigidly and wheel always contacts rail is eliminated.
Abstract: Based on the theory of vehicle-track coupling dynamics, a new wheel/rail spatially dynamic coupling model is established in this paper. In consideration of rail lateral, vertical and torsion vibrations and track irregularities, the wheel/rail contact geometry, the wheel/rail normal contact force and the wheel/rail tangential creep force are solved in detail. In the new wheel/rail model, the assumption that wheel contacts rail rigidly and wheel always contacts rail is eliminated. Finally, by numeric simulation comparison with international well-known software NUCARS, comparison with vehicle-track vertical coupling model, and comparison with running test results by China Academy of Railway Sciences, the new wheel/rail spatially dynamic coupling model is shown to be correct and effective.
118 citations
"Effect of softening of cement aspha..." refers methods in this paper
...In this paper, when calculating the dynamic response of the vehicle-track, the tracing-curve-method (Chen and Zhai, 2004) is adopted to locate the wheel-rail spatial contact geometry....
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Journal Article•
TL;DR: In this paper, the stiffness matrix and damp matrix of the 2D consistent viscous-spring artificial boundaries were deduced by comparing the matrices of the general finite element and the consistency of viscous spring boundary elements.
Abstract: The concept of the consistent viscous-spring artificial boundaries and viscous-spring boundary elements was proposed.The stiffness matrix and damp matrix of the 2D consistent artificial boundaries were deduced.The equivalent viscous-spring artificial boundary elements were developed by comparing the matrix of the general finite element and the consistent viscous-spring artificial boundaries.This method was applied to the uniform and layered half space problems.It was shown that the precision of viscous-spring boundary elements was the same as that of lumped viscous-spring artificial boundaries.The viscous-spring boundary elements were efficient and could be applied simply.
93 citations