This paper deals with the fatigue damage of the welded cantilever under a high-speed train subjec... more This paper deals with the fatigue damage of the welded cantilever under a high-speed train subjected to wind-induced loading using a field test campaign and a CFD (Computational Fluid Dynamic) simulation. The results show that significant airflow pressure on the cantilever frames and the structural resonance are the main cause of the fatigue damage of welded joints. During long-term operation, the free end of the cantilever tends to vibrate undesirably, which affects the service life of the structure. Firstly, a finite element model with constant amplitude of wind pressure is created based on the current design specifications to assess the static and fatigue strength of the cantilever. The simulation results show that the structural strength meets the standard design requirements. However, the results of the field test show that the acceleration at the free end of the cantilever is 32.0 m/s2, which far exceeds the relevant requirements. Meanwhile, there is a significant difference in aerodynamic pressure on the frame surfaces between the leading and trailing cars. An aerodynamic model is created for two full-size cars with the CFD method. The results show that FIV (flow-induced vibration) is the main cause of the continuous vibration of the elastic cantilever frame as long as the wake shedding occurs at a frequency close to the natural frequency of the frame. This study provides a reference for the aerodynamic fatigue design of the equipment mounted high-speed trains, especially for structures with low stiffness affected by open airflow.
Manganese-copper(Mn-Cu) alloy has high damping and strength, but there are few engineering applic... more Manganese-copper(Mn-Cu) alloy has high damping and strength, but there are few engineering applications in the railway vehicles at present. For the suspended bracket made of Mn-Cu damping alloy (M2052) under the railway carbody, the strength, the damping and the vibration reduction capability of the M2052 was testified in this paper. Constant amplitude fatigue tests under different loads were implemented for verifying its fatigue strength, and corresponding S-N curves are fitted to prove that its strength and the fatigue properties are sufficient. Based on the single bracket and reducing vibrational system with the 500 kg counterweight, the Frequency Response Analysis (FRA) rig tests subjected to the sinusoidal and white noise signals were carried out and the comparison with similar shape made of Q355 proves that the single damping bracket has a better damping performance. In the vibration reduction test with a 500 kg counterweight, the Acceleration Spectral Density (ASD) response results in the range of 10-50 Hz subjected to the sine sweep show that the damping alloy bracket is lower by about 32.2% than the Q355 steel bracket, and the deduction amplitude is evident at other frequencies. However, under the excitation of the white noise signals, the acceleration and dynamic stress response of the M2052 and the Q355 brackets are not significantly distinguish. It is assumed that the size of the bracket is too small to fully exert the damping property of the structures. Finally, two suggestions are proposed for the development and application of the innovative damping alloy in the railway vehicles.
Aiming to solve the failure problem of welded frame suspended under high-speed EMU, a longterm tr... more Aiming to solve the failure problem of welded frame suspended under high-speed EMU, a longterm tracking test was carried out. The modal resonance of 8-20 Hz is the main cause of structural failure. The characteristics of the in-service vibration environment and the difference with the standard load spectrum are analyzed. The measured load spectrum exceeds the IEC61373 standard load spectrum in the frequency range of 10-20 Hz and 30-120 Hz. Meanwhile, the kurtosis of measured acceleration signal does not always follow the Gaussian distribution for the carbody bolsters, and the acceleration and dynamic stress amplitude of the bolster and suspension equipment frame increase more with higher train speed. After a finite element model with welded joints was developed to evaluate the fatigue life, an optimized prototype BBF was designed. The reliability of the optimized structure is verified by rig test. The optimized structure avoids 8-20 Hz resonance and meets the test requirements.
This paper deals with the fatigue damage of the welded cantilever under a high-speed train subjec... more This paper deals with the fatigue damage of the welded cantilever under a high-speed train subjected to wind-induced loading using a field test campaign and a CFD (Computational Fluid Dynamic) simulation. The results show that significant airflow pressure on the cantilever frames and the structural resonance are the main cause of the fatigue damage of welded joints. During long-term operation, the free end of the cantilever tends to vibrate undesirably, which affects the service life of the structure. Firstly, a finite element model with constant amplitude of wind pressure is created based on the current design specifications to assess the static and fatigue strength of the cantilever. The simulation results show that the structural strength meets the standard design requirements. However, the results of the field test show that the acceleration at the free end of the cantilever is 32.0 m/s2, which far exceeds the relevant requirements. Meanwhile, there is a significant difference in aerodynamic pressure on the frame surfaces between the leading and trailing cars. An aerodynamic model is created for two full-size cars with the CFD method. The results show that FIV (flow-induced vibration) is the main cause of the continuous vibration of the elastic cantilever frame as long as the wake shedding occurs at a frequency close to the natural frequency of the frame. This study provides a reference for the aerodynamic fatigue design of the equipment mounted high-speed trains, especially for structures with low stiffness affected by open airflow.
Manganese-copper(Mn-Cu) alloy has high damping and strength, but there are few engineering applic... more Manganese-copper(Mn-Cu) alloy has high damping and strength, but there are few engineering applications in the railway vehicles at present. For the suspended bracket made of Mn-Cu damping alloy (M2052) under the railway carbody, the strength, the damping and the vibration reduction capability of the M2052 was testified in this paper. Constant amplitude fatigue tests under different loads were implemented for verifying its fatigue strength, and corresponding S-N curves are fitted to prove that its strength and the fatigue properties are sufficient. Based on the single bracket and reducing vibrational system with the 500 kg counterweight, the Frequency Response Analysis (FRA) rig tests subjected to the sinusoidal and white noise signals were carried out and the comparison with similar shape made of Q355 proves that the single damping bracket has a better damping performance. In the vibration reduction test with a 500 kg counterweight, the Acceleration Spectral Density (ASD) response results in the range of 10-50 Hz subjected to the sine sweep show that the damping alloy bracket is lower by about 32.2% than the Q355 steel bracket, and the deduction amplitude is evident at other frequencies. However, under the excitation of the white noise signals, the acceleration and dynamic stress response of the M2052 and the Q355 brackets are not significantly distinguish. It is assumed that the size of the bracket is too small to fully exert the damping property of the structures. Finally, two suggestions are proposed for the development and application of the innovative damping alloy in the railway vehicles.
Aiming to solve the failure problem of welded frame suspended under high-speed EMU, a longterm tr... more Aiming to solve the failure problem of welded frame suspended under high-speed EMU, a longterm tracking test was carried out. The modal resonance of 8-20 Hz is the main cause of structural failure. The characteristics of the in-service vibration environment and the difference with the standard load spectrum are analyzed. The measured load spectrum exceeds the IEC61373 standard load spectrum in the frequency range of 10-20 Hz and 30-120 Hz. Meanwhile, the kurtosis of measured acceleration signal does not always follow the Gaussian distribution for the carbody bolsters, and the acceleration and dynamic stress amplitude of the bolster and suspension equipment frame increase more with higher train speed. After a finite element model with welded joints was developed to evaluate the fatigue life, an optimized prototype BBF was designed. The reliability of the optimized structure is verified by rig test. The optimized structure avoids 8-20 Hz resonance and meets the test requirements.
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Papers by Jianhui Jing