Papers by Keyword: Overload

Abstract: Polyurethane foam has the properties of energy absorption and mitigating the impact, it has been used in internal protection head cap of cylindrical objects as cushion material, its theory and simulation has been widely discussed by the domestic and foreign scholars, but little experimental research is involved. In this paper, a dynamic loading water-entry impact experiment was designed for polyurethane foam plastics with different densities. In addition, ANSYS/LS-DYNA finite element analysis software was used to simulate water-entry process of cushion materials with different densities. The experimental and simulation results show that the 0.18 g/cm³ polyurethane material can effectively protect the cylindrical head, reduce the stress and have a good cushion effect on it.

Abstract: A hydraulic system simulation model was established suitable for space launch tower’s cable pendulum. And the influences between hydraulic system parameters with working performances were analyzed base on the model. The results show that the interactivity of load, internal leakage of cylinder, characteristics of control valve and relief valve have great effects on the system. Single or combined action of several typical factors can cause abnormal motions of the system. According to the pressure, flow, load and velocity of the system or relative signals in the input and output ports of one valve, some existed problems can be identified compared with the theoretic normal value. This work mainly presents a conduct for the characteristic analysis of the hydraulic system. By selecting appropriate parameters, checking the load and the working performances of some key components, it is effective to master the operation condition.

Abstract: Railway axles are subjected to cyclic amplitude loading which can lead to fatigue failure. For safe operation of railway axles a damage tolerance approach taking into account a possible defect in railway axle is often required. Because of different operation regimes of trains (fast/slow ride, ride on straight track, on curved track, over switches etc.) the load amplitude of axle is not constant. The variability of load is defined by a load spectrum, which is determined experimentally by measuring of load in service conditions. Even though the load spectrum is measured on several hundreds or thousands of operation kilometres, the railway axles are in operation much longer time (often tens of years). Therefore, some load amplitudes higher than ones measured in the test can occur during a long-term axle service. The contribution presented deals with the effect of extension of load spectrum by rare high load amplitudes, which can occur during long-term operation, on residual fatigue lifetime of railway axles.

Abstract: Research on the power flow transferring identification method based on DC sensitivity factors is carried out. According to the analysis of transfer power flow sensitivity factors matrix, the disadvantage of this method is proposed that it may identify incorrectly due to the only criterion of active power when fault occurs. In order to improve its performance, the criterion of impedance angle is put forward. The combination of the two criteria is applied to the improved flow transferring identification scheme. The improved scheme can identify non-faulted overload reliably and block zone 3 distance protection to prevent cascading trips effectively. The simulation results of IEEE 10-machine 39-bus system have proved its superiority and practicality.

Abstract: An intelligent protection system of electromagnetic starter in coal mine was designed. Its controller core is PLC LM3108K. The voltage rank of protection system is 660V and the electric current rank is 400A. It has protection functions for overload, short circuit, break phase and three-phase imbalance. The system achieved overload protection by using the method of inversing time overload. Greater the overcurrent is, Shorter the time of protective action is. The system achieved short circuit protection by using phase sensitive protection method, which improves sensitivity and reliability of short circuit protection. The system can display work status parameters and fault types timely by text LCD. It has the advantages of hardware circuit structure flexibility and automatically reset after fault relieved.

Abstract: In order to guarantee the safety of the highway transportation and the durability of road use, reducing vehicle overloading transfinite damage to roads and dangerous driving influence on transportation security, curb corruption in traffic law enforcement, our team is based on vehicle networking technology, the video monitoring technology, RFID radio frequency technology, geographic information platform, information fusion technology, 3G network, the organic combination of GPS positioning technology, developed a freight vehicle supervision assistant system. System can not only achieve dynamic measuring weight, illegal vehicle information acquisition and processing, and also can realize illegal vehicle directional interception, dangerous driving warning and drivers complaint report law enforcement behavior, to reduce overload the accident happened at the same time, also reduce the waste of traffic administration human and financial resources, realize the driver and two-way supervision and law enforcement personnel, make the law enforcement process more fair, just and open, thus further improving the overall quality of traffic law enforcement.

Abstract: Concrete blocks were arranged on both sides of the strip foundation to simulate overload. Model tests with overload or not were conducted, for four test programs including pure sand ground, single plate reinforced ground, double plates reinforced ground and single plate with two anchorage ends reinforced ground. The influence of overload on bearing capacity and settlement of ground, earth pressure and strain of FRP was analyzed. The test results showed that overload can enhance the bearing capacity, and reduce the ground settlement in a certain extent, with the beneficial effects of overload on reinforcement effect being decreased while the amount of reinforcement was increased.

Abstract: In power system, flow transferring can cause non-fault overload. Traditional zone 3 distance relays cannot distinguish overload caused by faults or by transferred power flow and may operate incorrectly, thus cause cascading trips, even blackout. Based on wide area measurement system (WAMS), this paper proposes two criteria to realize flow transferring identification function. First, three-phase voltages and currents are measured and compared with those calculated before fault, which should be applied to the given identification criteria. Then, the logical relationship for flow transferring identification are put forward to prevent distance relays from incorrect behavior caused by non-fault overload and unblock zone 3 distance relays when fault occurs. Through the simulation results, the effectiveness of the proposed method is verified.

Abstract: The 15-5PH (precipitation-hardened) martensitic stainless steel is prone to embrittlement following ageing during service at temperatures between 300°C and 350°C. This results in an increase in strength and a decrease in elongation and fracture toughness. However little information is available on the consequences of long term ageing on fatigue crack growth resistance. In the present study this issue is precisely addressed at room temperature and 300°C, with different load ratio under constant amplitude loading and under variable amplitude loading.At room temperature, the results indicate a marginal effect of the load ratio, regardless of ageing conditions and temperature. While the Paris regime is not affected by ageing, a significant drop in the critical stress intensity value before unstable fracture is observed, reflecting a decrease in fracture toughness of the material with ageing. At 300°C, the FCGRs are higher than at room temperature for all ageing conditions. Variable amplitude loading tests carried out on differently-aged materials showed the same retardation effect.

Abstract: In this investigation, variable amplitude loading effect was studied on aged hardening Al-alloys in series 2000 and 7000. Generalised Willenborg model was used in order to show loading interaction effects (overload effects). Variable amplitude loading under different form of spectrum has affected highly the fatigue life and fatigue crack growth rates. Fatigue lives were increased and fatigue crack growth rates (FCGRs) were decreased in increasing of overload ratio in single overload case. In application of overload band, the fatigue lives and FCGRs were affected by band overload and R-ratio of them when level in FCGRs was increased.