This study develops a computational model of the dynamic characteristics of the actively controlled, magnetically levitated (maglev) system moving on a flexible guideway. The 5-dof ...(degree-of-freedom) vehicle model, the modeling of the EMS (electromagnetic suspension
), guideway, and guideway irregularity are described, respectively. In this sense, the dynamic response of a coupled vehicle and guideway system is investigated with different vehicle speeds and masses. Furthermore, the formulation of SMC (sliding mode control) based on the Kalman filter is addressed for the control of the dynamic response of the maglev system for various prescribed running speeds. For numerical simulation, the Runge–Kutta method is used to solve the state-space equation, which includes information about the vehicle, guideway and controller. The results reveal that both the air gap fluctuation and the cabin CG (center of gravity) vertical acceleration are strongly affected by the vehicle speed and guideway irregularity, but only slightly affected by the vehicle mass. Moreover, SMC based on the Kalman filter considerably reduces the air gap fluctuation and cabin CG vertical acceleration responses, and the efficiency of the adopted control methodology is demonstrated even at higher critical speed conditions.
► The dynamic response of a coupled vehicle and guideway system is investigated for different vehicle speeds and masses. ► The results reveal that both the air gap fluctuation and cabin CG vertical acceleration are strongly affected by the vehicle. ► SMC based on the Kalman filter considerably reduces the air gap fluctuation and cabin CG vertical acceleration responses.
The influences of train length on vehicle dynamics and train stability were investigated using different vehicle models of various lengths. First, a reliable vehicle model was constructed to ...determine the cause of unstable lateral vibration. This model reflects the tendencies observed in the high-speed test line investigations. Analysis results show that the secondary lateral stiffness of the air spring is the most significant cause of lateral vibration in car bodies. Vibrations were stable in the analysis of short train formations, which had either 7 or 10 cars, even though lateral stiffness was high. However, long train formations that contained either 16 or 20 cars vibrated unstably. Mode analysis results suggested that an increase in wheel conicity can reduce the unstable, low-frequency vibration of long trains.
The running stability of railway vehicle has been one of the important pending issues of railway operators and organizations. Especially the dynamic stability has become more important in terms of ...securing safety since vehicles are running faster than before. Currently the dynamic stability assessment is being conducted by usingtest equipment such as roller rig. However, full scale roller rig is not cost effective and inconvenient to achieve diverse design parameters. To marginalize the drawbacks, a small scale simulator has been used butthe technique for the design of the small scale simulator for the fundamental study about the dynamic characteristics of the wheel-rail system and the bogie system has not been well developed. Several researchers had produced 1/5 small scaled bogie model and analyzed critical speed by applying a creep theorybut the related studies did not carefully describe all of factors including suspension characteristicsthat have a large effecton small scaled bogie’s dynamic characteristics. Therefore the research about the development of the small scale simulator and the assessment method of the bogie dynamics has been required. This study presents the assessment method of 1/5 small scaled bogieusing small-scaled derailment simulator to predict dynamic stability of the railway vehicle. The results show that the characteristics of the small scaled bogie’s major modes obtained at the running speed of 40km/h on the small-scaled derailment simulatorweresimilar to the mode analysis results and this means thatthe obtained results from the small scaled simulator could be used to assess the dynamic characteristics of the vehicle with a support from the analytic model. It was also found that the theoretic hunting motion frequency of the 1/5 small scaled bogie was similar to thefrequency obtained on the simulator. These results mean that the small-scaled derailment simulator could reproducethe wheel/rail interface characteristicsand could be used for running stability assessment through the analytic model considering relevant similitude rule.
The super-speed tube train was introduced to increase the speed of ground transportation.
It levitates magnetically and runs in a partial vacuum tube, which significantly reduces air resistance.
...However, strong magnetic force sufficient to propel the massive train can affect the infrastructure. The induced eddy current produces joule heat, and raises the inside temperature of the girder, which might lead to electrochemical corrosion on the girder, thereby weakening its durability. In this paper, the authors analyzed the magnetic flux and induced eddy current in the reinforced concrete girder by using three-dimensional FEM, particularly by varying the number of reinforcing steels of the upper flange of the girder to the condition of almost the same flexural strength and reinforcing steel amount. KCI Citation Count: 1
An ultrasonic horn originally designed for welding has generally been used for thermosonic testing. However, it is difficult to obtain reproducible and controllable excitation with the existing horn ...system because of nonlinearity in the coupling; surface damage can also be produced by chattering caused by loss of contact between the tip of the horn and the structure. Therefore, this research was conducted to develop a simple excitation system that should excite sufficient strain for the detection of the defects of interest at all relevant positions in the structure, and should also be easy to attach to and remove from the structure. It must also avoid surface damage. Test results suggest that a simple, small wax coupled PZT exciter may provide a convenient, reliable thermosonic test system in applications such as composite structures and electronic materials where relatively low strain levels are required for damage detection.
Wheels of the railway vehicle play the important role for driving train through wheel-rail interaction. Especially wheel profile is one of the most important design factors to rule the running ...stability and safety of train. Accordingly maintenance of wheel like wheel profile control is also very important for securing safety and stability of train operation. This study presents the wheel wear measurement results of Saemaeul running on the conventional line. The train set included three different cars which have different shape of wheel profile including KNR profile currently used in Saemaeul. Train set was operated on Seoul-Pusan line with fixed train set formation for commercial service. Wheel wear measurements were performed periodically. We can find the influence of wheel profile on the wheel wear of the train running on the conventional line through the measurement results.
The super-speed tube train was introduced to increase the speed of ground transportation. It levitates magnetically and runs in a partial vacuum tube, which significantly reduces air resistance. ...However, strong magnetic force sufficient to propel the massive train can affect the infrastructure. The induced eddy current produces joule heat, and raises the inside temperature of the girder, which might lead to electrochemical corrosion on the girder, thereby weakening its durability. In this paper, the authors analyzed the magnetic flux and induced eddy current in the reinforced concrete girder by using three-dimensional FEM, particularly by varying the number of reinforcing steels of the upper flange of the girder to the condition of almost the same flexural strength and reinforcing steel amount.
Thermosonics is a non-destructive testing method in which cracks in an object are made visible through the local generation of heat caused by friction and/or stress concentration. The heat is ...generated through the dissipation of mechanical energy at the crack interfaces by vibration. The temperature rise around the area close to the crack is measured by a high-sensitivity infrared imaging camera whose field of view covers a large area. The method therefore covers a large area from a single excitation position so it can provide a rapid and convenient inspection technique for structures with complex geometry and small and closed cracks. An ultrasonic horn, originally designed for welding, has generally been used for thermosonic testing. However, it is diffcult to obtain reproducible and controllable excitation with the existing horn system because of non-linearity in the coupling; surface damage can also be produced by chattering caused by loss of contact between the tip of the horn and the structure. Therefore, the general aim of the study was to develop a reliable and convenient excitation method that should excite sufficient vibration for the detection of the defects of interest at all relevant positions in the structure and must also avoid surface damage. In this thesis, a numerical and experimental study for the development of the ex- citation method for reliable thermosonic testing is presented. Successful excitation methods for the detection of delaminations in composites and cracks in metal struc- tures are described. A simple, small wax-coupled PZT exciter is introduced as a con- venient, reliable thermosonic test system in applications where relatively low strain levels are required for damage detection such as composite plates. A reproducible vibration exciter may be su cient for thermosonic testing in some metal structures such as a thin plates. However, higher strain levels are often required in metal structures, though the required strain level is dependent on the crack size. This level of strain is not easily achieved within the reproducible vibration range because of non-linearity in the contact between the exciter and the structure. Therefore, studies are conducted with an acoustic horn with high power capability to investi- gate the characteristics of the vibration produced in a real structure with complex geometry and to develop a excitation method for achieving reliable excitation in the non-linear vibration range for thermosonic testing. An excitation method for a complicated metallic structure such as a turbine blade is also investigated and the in uence of the clamping method and the excitation signal that is input to the horn on the vibration characteristics generated in the testpiece is presented. As a result, a fast narrow band sweep test with a general purpose amplifier and stud coupling is proposed as an excitation method for thermosonic testing. This method can be ap- plied to different types of turbine blades and also to other components. One typical characteristic of a thermosonic test using non-linear vibration is the lack of repeata- bility in the amplitude and the frequency characteristic of the vibration. Therefore, vibration monitoring is necessary for reliable thermosonic testing and a Heating In- dex(HI) has been proposed as a criterion indicating whether su cient vibration is achieved in a tested structure or not. The HI is calculated from different vibration records measured by different sensors and these results are compared in this thesis. A microphone can provide a cheaper and more convenient non-contacting vibration monitoring device than a laser or strain gauge and the heating index calculated by a microphone signal shows similar characteristics to that calculated from the other sensors.
PDF
