Papers by Keyword: Impact Force

Abstract: The conventional milling process is difficult due to the high strength and hardness of Cr12MoV, which can cause the rapid tool wear, premature failure,and poor milling quality of work platform. The ultrasonic vibration machining technology has been founded to be effective in the milling process of hard-to-cut materials like die tool steel and nickel alloys. The ultrasonic vibration assisted milling (UVM) technology is carried out the axial milling of Cr12MoV in this paper, and the average impact force F_i is influenced by the vibration amplitude A, the vibration frequency f, and equivalent mass of the vibrating part M. The mean value of cutting force F_x, F_y, and F_z decreases by 25%, 15.04%, and 17.46%, respectively. With the increase of vibration amplitudes, the value of surface roughness firstly decrease and then increase, and it is obviously lower than conventional milling. The experimental results demonstrated that the UVM technology is a feasible method for the low cutting force and high quality process of cutting Cr12MoV.

Abstract: Currently, significant part of advanced air transport structural elements is made of fiber-reinforced polymer composite materials (PCM), in particular, carbon plastics. In order to increase the resistance of these materials to static electricity and lightning discharges while air transport passes through lightning fronts, lightning protection coatings in the form of copper grids are incorporated into PCM structure . For load-bearing structures and aircraft shells, the influence of dynamic loads in the form of low-cycle high-amplitude loading and hitting by solid objects is typical. The presence of inbuilt metal structure introduces additional uncertainty into the anisotropic PCM perception of these loads. Studies of the strength of carbon-fiber-reinforced plastics with built-in LPC at low-cycle loading and their perception of shock load has been carried out. It is established that short-term processing in the microwave electromagnetic field leads to an increase in the strength of the samples under low-cycle loading by 210%. CFR with LPC absorbs a part of the shock impulse and does not transfer it completely to subsequent structures. The microwave electromagnetic field helps to improve the damping properties of materials by 19.5% in average with a low impact energy. With an increase in the impact force energy, the effect of the microwave electromagnetic field is manifested to a less extent; further improvement of the damping properties does not occur. It increases the elastic characteristics of the material and practically does not lead to cracking and exfoliation of the surface layer in the impact area. The results can be used in the development of technologies for final processing of the products made of PCM in order to increase their resistance to dynamic loads.

Abstract: Dynamic force that strains on the rail and the wheel occurs. In case of wheel flats, during wheel and rail interaction, exposure time of dynamic forces acting in contact is very short and depends on the railway vehicle speed and the length of flat.Results obtained from a method that uses mathematical model of a system “Railway Vehicle Wheel-Track” and the simplified method to determine a vertical impact force of wheel with flat and rail interaction are presented in this article.The results of the mathematical and physical results of this system are analysed and presented.

Abstract: Bamboo shinai is a practice sword for kendo which is the Japanese traditional fencing. The effectiveness of the shock absorption of the bamboo shinai has been shown in our previous study. Although shinai is usually made of bamboo, it is also made of carbon fiber reinforced plastic (CFRP). The impact response of bamboo shinai and CFRP shinai is compared. As a result, the difference of peak value of impact force between bamboo shinai and CFRP shinai against similar initial velocity is small. Impact response measurement of each shinai has been carried out using the Levitation Mass Method (LMM) which has been proposed by us. In this method, a mass, which is levitated with a pneumatic linear bearing and hence affected by negligible friction, is made to collide with a shinai under test. Because bamboo is natual product, resource of suitable bamboos for shinai is limited. On the other hand, carbon-fiber-reinforced-plastic (CFRP) can be designed to be suitable for a shinai, which has a fixed shock absorption characteristic for an application to the structure of robot arms. Therefore, if the shock absorption characteristic of CFRP shinai is the same as that of bamboo shinai, CFRP shinai is more suitable for the structure of robot arms.

Abstract: Since 1950, the use of water jets has grown in the field of cleaning pipes and sewers. The regular cleaning of the materials deposed in sewer networks is realised especially with equipment that uses high pressure water jets. The functioning of this equipment is dependent on certain process parameters that can vary, causing variations of the impact forces. The impact force directly affects the cleaning of sewer systems. This article is a part of research activity what is centered on the study of the cleaning head - sewer system. The purpose of this research is to determine an equation of the impact forces of the water jet that depend on process parameters. The research method used is that of the full factorial plan. For the experimental determination of the impact forces a stand for generating water jets and a device for measuring the forces of impact are used. The equation of the impact forces measured is determined using the software Minitab 17.

Abstract: The impact process of 50000t ship and steel sheet pile bulkhead is simulated by finite element software ANSYS/LS-DYNA. This article acquires the impact force-time curve, equivalent force-time curve of steel sheet pile and the pressure-time curve of breast wall. Comparing the impact force of numerical simulation with the result of ship-bridge collision specifications, and general rules and characteristics are obtained. At the same time, put forward some measures to prevent the damage of wharf structure under the ship of large velocity impact, which provide theoretical references during the design, maintenance, and transformation of similar wharf.

Abstract: Concrete filled double skins steel tube is a new components which is based on concrete filled steel tubular and use inner steel tube instead of core concrete. The components have many advantages such as little weight, good resistance for earthquake, good stiffness for resist bending and good performance for resist fire, and has been used in bridge pier, high-rise buildings, power transmission tower and so on. While these structures may inevitably suffer impact which comes from vehicles, ships, aircraft, etc. the structures which is impacted have taken much attention. This article will analysis dynamic behavior of concrete filled double steel tube under impact with simply supported, and propose formula of dynamic bearing capacity, laid the foundation for the analysis of impact performance of CFDST.

Abstract: Industrial cleaning is a classic application of water jets technology. In the late 1950s, when reliable high pressure pumps were built, the usage of water jets spread widely in the field of pipes and sewerage cleaning. In our particular case, water jets with less than 340 bar pressure are being used. The experiment is the research method used in the study of the impact forces that occur in the sewerage cleaning head system. In order to measure the impact forces between the water jet and a flat and rigid surface, we designed and built a stand for generating pressure jets, as well as a device to measure the impact force. Using the impact forces measured were calculated the coefficients of discharge, speed and contraction of water jet at the outlet of nozzle.

Abstract: In this article impact loading of concrete slabs has been presented. Different methods for calculate impact force have been considered. Numerical models of two slabs with different boundary condition have been solved while using finite element method in ANSYS software. In the final part of the paper, z-direction displacements and bending moments of models have been compared.

Abstract: Drilling jar is widely used to solve the stuck pipe incidents in the drilling process. Impact force which is being made during the jarring operation is acting on stuck point to achieve unfreezing effect. Conventional hydraulic dynamic load calculation method is not considering the impact of friction force on stress wave spreading in drill string. In actual process, friction and viscous resistance caused by the movement of drill string in drilling fluid, making drill string acceleration process exhibiting damped vibration characteristics. Therefore, with the drill string damping vibration theory, analysis of dynamics of acceleration process can be made, and displacement and velocity equation in longitudinal acceleration process can be deduced. Thus the maximum velocity of drill string before collision has been calculated, and impact force acting on the stuck point has been deduced with the law of conservation of energy and momentum. The model of impact force calculation is more satisfied with actual environment in the wellbore during jarring operation.