Papers by Keyword: Dynamic Load

Abstract: There is a need for railway systems and upgrade their infrastructure to meet the future growing demand. This would expand the railway network by planning new track routes to increase the efficiency of railway transportation by running behavior of high train speeds between urban cities. The track/ballast; sleepers; and subgrade foundation system are important superstructure parts that need to be upgraded and improved to withstand high train speeds. A numerical finite element technique significantly benefits in simulating the impact of the dynamic response and predicting the deformation and stress distribution in the railway ballasted system. A three-dimensional finite element program PLAXIS ver. (20) have been utilized in this research to analyze the track of complex behavior under train loading. The vertical displacement of 3.8 mm was obtained at the rail/wheel contact point and greater than at the ballast embankment by about (19%) and (37%) for the subgrade foundation. Also, the maximum value of vertical displacement corresponds with the movement path of the train load is reduced laterally as the distance from the track centerline increases. The maximum vertical acceleration of 15.2 m/s² was obtained at surface points under track loading and decreased gradually with increased depth below the ballast embankment layer to reach a minimum value of 1.2 m/s². The vertical deformation was 1.3 mm, 2 mm, and 3.9 mm for 40 km/hr, 50 km/hr, and 60 km/hr respectively, and increased rapidly to 15 mm for train velocity greater than 70 km/hr due to the significant increase in train vibration level at higher speed. A critical train speed of 70 km/hr was observed that promoted the level of vibration and magnified the area of influence.

Abstract: The paper presents technological schemes of hybrid and combined operations performed through the action on a workpiece by several sources of loading (static and dynamic). Multiple or single dynamic action is performed during action of static loading. Use of pulsed magnetic fields is treated as the dynamic action. The brief description of the presented schemes, needed for understanding of the new technical decisions, their features and advantages, is available. The proposed technical decisions are innovative, they are protected by patents and are tested in respect of their reality and efficiency. Standard-type parts have been obtained which were made with the help of the proposed technologies of sheet stamping, assembling, welding, casting, rolling, etc. The paper defines a new scientific-technical direction in processing of metals which is aimed at increase in productivity of production processes.

Abstract: Upgrading the quality of compaction of powder materials is achieved by the use of hybrid technologies when the powders are acted upon by two or more sources of loading. The present paper describes compaction of a powder under the action of static and dynamic loads. A pulse-magnetic field is used as a dynamic load. The procedure and technique of experimental researches are described. Porosity (compactness) and structure of the material are evaluated for various combinations of loads, geometrical sizes and shapes of products. The conclusion is made about significant upgrading of quality of the powder material when used the hybrid technology compared to the static compaction.

Abstract: A large number of accidents involving damage of temporary grandstands during different types of events were observed in the past. The aim of the paper is to analyse numerically the effectiveness of a polymer damper in damage reduction of a temporary steel scaffolding grandstand exposed to dynamic load due to jumping. The element has been installed as a diagonal one at the back part of the structure. The method has been compared with the typical solution of strengthening the grandstand with the diagonal stiffener of tubular cross section. The results of the study clearly show that the response of a temporary steel grandstand equipped with a diagonal damper as well as with the diagonal stiffener is substantially different. The application of the polymer damper leads to considerable reduction in the level of measured accelerations due to the increased structural damping preventing from damage.

Abstract: Various types of sleepers from different materials are used in railroad tracks, therefore nowadays prestressed concrete sleepers are the most common type of sleepers. High strength concrete and prestressing reinforcement are used in concrete sleepers. These railroad members are stiff, durable and can withstand heavy loads. However replacement of the cracked or damaged sleepers are expensive and it is necessary to properly design and test them before exploitation. Experimental research of prestressed concrete sleepers under static and dynamic loads are described in this article. Sleeper rail seat section is a support for the rails and various types of heavy loads are affecting this part of the sleeper. Therefore analysis of experimental results on sleeper rail seat bearing capacity and cracking are provided. Sleepers must meet certain cracking requirements and residual crack width must not exceed design value. Experimental residual crack widths are compared with design values. Influence of different diameter and strength reinforcement is analyzed on the behaviour of sleeper rail seat section.

Abstract: Structure and properties of cement composite are time-varying characteristics, depending among others on environmental conditions. The key idea of the project is a struggle for complex research of joint effect of physical, chemical and dynamic loads on the internal structure [8] of cement composite and understanding the correlation between changes in microstructure and macro-scale properties [5]. During the experimental program, specimens will be exposed to combined influence of freeze-thaw cycles [9], aggressive chemical agents and dynamic loading [7]. The aim is to create a theoretical basis for design of effective cement composites meant to be used in severe environmental conditions. Results of first dynamic load tests carried out on prismatic specimens (100x100x400 mm) are presented in this paper. The results are supplemented by ultrasonic measurement.

Abstract: The dynamic load strength test of automotive BIW is an important parameter for vehicle passive safety, but different test standards, different test requirements, which caused much trouble to the test authority. To solve the shortcomings of the traditional machines, such as low automation, poor universality and weak ability of data processing, this paper designs a new test machine for the dynamic load strength trials of automotive BIW on the basis of three typical standards. The test results indicated that this test machine embodies the characteristic of easy operation, stable function, and wide suitability, which improves the measurement accuracy and efficiency, at the same time, solves the problem of the database construction.

Abstract: Dynamic reactive power optimization of power system is an important means to ensure grid economic safety. Unlike static reactive power optimization, dynamic reactive power optimization has to consider the reactive power compensation devices switches and number of constraints of transformer tap stalls. The number of constraints undermine the independence of each period, each time reactive power optimization scheduling interrelated, so dynamic reactive power optimization must be considered from the entire period of time to compensate the number of constraints of the devices, and how to deal with action number of constraints is difficulty and focus of solving dynamic reactive power optimization of the power system.

Abstract: The hybrid bus frame is a vehicle’s main bearing component, in which bearing stress state is very complex. In this article, the virtual prototype vehicle model is established to extract dynamic loads between each key connecting parts and the hybrid bus frame. At the same time, the hybrid bus frame finite element model is established to make strength and stiffness analysis with dynamic loads as boundary conditions. The results verify that the strength and stiffness can meet the hybrid bus frame requirement, and the largest deformation and stress area is found. The results also can provide an important basis for correcting the frame structure. What’s more, this paper makes a comparison between the method of the frame finite element analysis based on dynamic loads and the method of the frame finite element analysis based on the statics, concluded a result that the frame finite element analysis based on dynamic loads can more accurately describe the real stress state of the frame and the analysis result is more reliable.

Abstract: For socked and non-socketed piles in the different mechanical behavior under static and dynamic loads, the paper use ABAQUS to model, simulate the pile , the soil interlayer thickness between the bottom of the pile and bedrock are 2m, 4m under vertical load and Earthquake, cushion cap, pile and pile soil stress situation found non-socketed piles when the soil interlayer thickness within a certain range, the composite pile small subside under dynamic, static loads, the non-socketed piles can better take advantage of the pile soil has a good seismic performance in the earthquake.