Carbody Strength Research Articles

Fracture Properties of Double Skin Structure including Friction Stir Welds used in Aluminum Alloy Railway Carbody in Three-point Bending Tests.

Recently friction stir (FS) welds are applied to aluminum alloy railway carbody. FS welds may have lower mechanical strength than base metal. It is important to identify their characteristics when evaluating the strength of carbody. Therefore, quasi-static three-point bending tests were conducted to determine the fracture characteristics of double skin structure to which FS welds are applied under bending loads. Specimens are double skin structure with FS welds and were fabricated from the side structure of aluminum alloy railway vehicles. Furthermore, we carried out a FE simulation under the same condition as the experimental test, and the differences between the experimental results and the simulation results were verified. The simulation result was in good agreement with the experimental one in terms of load before crack initiation or buckling.

Vibration fatigue analysis of high-speed railway vehicle carbody under shaking condition

A method called modified modal superposition method (MMSM) for calculating the vibration fatigue dynamic stress of carbody under shaking condition is proposed. In MMSM, each external load is divided into low frequency component and high frequency component according to critical frequency (CF), which is used to separate whether the external load causes resonance effect of the structure, then traditional quasi-static method (QSM) and modal superposition method (MSM) are adopted to deal with the two load components respectively. During the simulation, QSM is used to ensure the integrity and accuracy of the structural stiffness under quasi-static condition, while MSM can consider the dynamic characteristics of the structure in resonance state. At last, the fatigue strength of the carbody was carried out based on the stress calculated according to cumulative damage method. The calculation results show that the fatigue life of carbody under shaking condition is significantly reduced to 81,450 km, far less than the design life. The damage of the stress obtained by MMSM is far greater than that from traditional QSM, even in the new wheel condition, the damage obtained by QSM is too dangerous. For the stress obtained by MSM, generally in the low-frequency region, the stress level is higher than that obtained by QSM due to mode truncation, especially for the average stress. So QSM and MSM are not recommended to evaluate the fatigue strength of railway vehicle carbody.

A modal frequency optimization approach for a fully-equipped car body of high-speed trains

The tubular structural car body of high-speed trains with lightweight design generally results in a low diamond deformation modal frequency, which deteriorates significantly both the lateral and vertical vibrations of the car body. To increase the diamond deformation modal frequency of the car body, the structural optimization and modal sensitivity optimization of the car body based on sensitivity analysis are proposed. The former starts with the analysis of the mode shape deformation characteristics; in the latter case, the modal strain energy verification is considered and the influence of the threshold values of sensitivity on the modal frequency optimization are studied. Results show that by increasing the spacing of the inner and outer panels of the side wall from 47 mm to 65 mm and optimizing the thicknesses of 16 components of the car body, the diamond deformation modal frequency of the fully-equipped car body can be enhanced from 8.7 Hz to 10.31 Hz, while ensuring the lightweight requirement without loss in car body strength.

The transient response of car body and side windows for high-speed trains passing by each other in a tunnel

The transient responses of car body and side windows for CRH2 high-speed trains passing by each other in a tunnel at different meeting conditions were investigated numerically using the Finite Element (FE) software LS-DYNA/explicit algorithm. Nine meeting cases including the case of meeting at the same speed and at the different speeds were respectively examined, where the moving pressure waves loaded on the surfaces of the observed train were obtained from the previous aerodynamics simulation. The typical transient responses (i.e., the stress and lateral displacement) of car body and side windows were analyzed, and the contribution of pressure wave to structural design strength of car body was also discussed. A comparison between the dynamic pressure wave loading simulation and the equivalent quasi-static loading simulation was also made. The simulation results indicate that both the von-Mises equivalent stress and lateral displacement of the car body are sensitive to the meeting speed. The side windows are subjected to the tensile stress in the most of response stage, and the maximum Y-directional stress of each monitor point presents a rapid increase with the increased meeting speed. The contribution rate of pressure wave to structural strength of the car body increases with the meeting speed. Besides, the dynamic pressure wave loading simulation method is demonstrated to be a better choice to investigate the transient response of the carriage. These research results are significant for ensuring the safety of the trains traveling in tunnels and elevating the safety of side windows.

The Application of Aerodynamics in the Design of Double-Decker Container Vehicles

In the double container car size overrun, the center of gravity high, angular shape characteristic, according to the aerodynamic load of vehicle dynamics, and the influence of intensity method and the mechanical model, studied the aerodynamic load of double container car mechanics index and application in vehicle design method, using the aerodynamics of wind environment and climate and the intersection under the condition of high speed passenger cars are double container car for the analysis of aerodynamic load, and the vehicle dynamics and simulation analysis of car body strength, to test the double container car running safety and stability, and in the original railway line running test organization, double container car aerodynamics performance has been further validation.

Evaluation of Carbody Strength against Side Load

In the 2005 railroad crash in Japan, a side impact severely damaged one carbody, suggesting the need to improve the crashworthiness of carbodies under such impacts. This paper reports on static and dynamic compression tests that were performed to evaluate carbody side strength using full-size partial carbodies, followed by finite element (FE) analyses performed under the same loading conditions as in the empirical tests. The numerical results obtained by FE analyses were consistent with the empirical results in terms of deformation of carbodies and load-time characteristics. The authors developed a method that uses FE analysis to evaluate the impact deformation behavior of a carbody subject to side loads. An example using this method is presented.

CP강의 디스크레이저 용접부의 경도특성에 미치는 B 함유량의 영향

CP steel was developed to reduce the weight and increase the strength of car body. When it was welded using state-of-the-art disk laser welding, the effected of boron on the microstructure and hardness were investigated. Welding power was fixed at 3.5kW and welding speeds were 4,8 and 12m/min. Full penetration occurred in welding speed of 12m/min and weld bead was almost unchanged with boron contents. But the welding speed increased, the upper and lower bead were narrowed. In a welding speed of more than 8m/min, underfill defects were formed on the bead bottom. The hardness of weld zone was somewhat fluctuation in fusion zone and HAZ showed the highest hardness values. The hardness of each region showed little change with the boron contents, and softening phenomenon occurred in the HAZ near the base metal regardless of the boron contents.

Carbody-side Strengthening Effects of an Inner Sub-frame Ring Structure

When a railway vehicle overturns in an accident, the carbody cross section is likely to take on a parallelogram shape as a result of side impact, and the survival space for passengers and crew is reduced as a result. To secure the survival space available, an innerring structure can be formed by uniting sub-frames attached to the inside of the carbody as non-structural members. The authors performed strength tests and finite element analysis to verify the possibility of improving carbody strength against loads from the side by creating such a ring structure.

566 内部骨組を活用した鉄道車両の車体強度向上効果の検証

When a railway vehicle overturns in accidents, the shape of cross section of the carbody is likely to be transformed to the parallelogram by the side impact. In the case, the survival space for passengers and crews may be decreased by the deformation. To secure the survival space, the "ring structure" is composed by uniting sub-frames attached inside the carbody as non-structural members together. Empirical tests and FE analyses were performed to verify the possibility of improving the rail carbody strength against the load from the body side.

Speed-up of Car Body Strength Calculation by the Use of Electronic Computer

Though many methods have been proposed for calculating the strength of a car body, the energy method regarding the side frame as Vierendeel truss is employed by J.N.R. as its standard method. Here will be described the principle of the calculation and the program for the electronic digital computer, where the initial data (specific quantities of cross section, dimensions of various parts, elastic coefficients, condition of loading, etc.) are given as input ; and sectional forces (bending moment, shearing force and axial force), stress of various parts and deflection of nodal points of lower chord can be obtained as output.