Formation Mechanism of Metro Rail Corrugation Based on Wheel–Rail Stick–Slip Behaviors

Field investigation shows that most corrugations occur on the inner rail surface of curved tracks with a radius of less than 700 m. In order to explore the formation mechanism of metro corrugation, the relationship between wheel–rail stick–slip characteristics and rail corrugation is studied by combining single wheelset curving and a rigid–flexible coupling model. The numerical results illustrate that the lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the small radius curve eventually leads to the generation of inner rail corrugation, and the lateral torsional stick–slip vibration of outer rail–outer wheel of the driven wheelset may also occur, but the intensity is weak and the probability is low. The lateral torsional stick–slip vibration of inner rail–inner wheel of the guiding wheelset on the large radius curve is also easy to cause inner rail corrugation, but the degree of inner rail corrugation is lower than that on the small radius curve; the outer rail on the large radius curve is still not easy to produce corrugation. The formation mechanism of rail corrugation on the straight track is different from that on the curve track, which is mainly related to the wheel–rail longitudinal torsional stick–slip vibration.

On the Planning and Construction of Railway Curved Track

Increasing demand for railway vehicle speed has pushed the railway track designers to develop high-quality track. An important measure of track quality is the character of the transition curve track connecting different intersecting straight tracks. A good transition curve track must be able to negotiate the intermittent stresses and dynamic effects caused by changes in lateral acceleration at high speed. This paper presents the constructional methods for planning transition curves considering the dynamics of movement. These methods consider the non-compensated lateral acceleration, deviation in lateral acceleration and its higher time derivatives. This paper discusses the laying methods of circular, vertical and transition curves. Key aspects in laying a curved track e.g. widening of gauge on curves are discussed in this paper. This paper also suggests a transition curve which is effective not only from a dynamic point of view considering lateral acceleration and its higher time derivative but also consider the geometric conditions along with the required deflection angle.

FE Model Of A Cord-Rubber Railway Brake Tube Subjected To Extreme Operational Loads On A Reverse Curve Test Track

In certain cases, rolling stocks and railway vehicle components, i.e. brake tubes need to operate under extreme conditions such as at sub-zero temperature (e.g. -40°C) and on a reverse curve track, when displacements of the suspension points of the tubes cause large deformations in tubes. In this paper, displacements of the suspension points of the tubes are determined by a kinematic model validated by a draw and buffing gear test [1]. Afterwards, FE simulation has been carried out at minimum and maximum suspension point distance based on these displacements for the investigation of stress, strain states and possible failure considering the case of internal pressure and no internal pressure. Equivalent strain, stress and Tsai-Hill failure indices are much below the criterial values, so failure is not probable. The straight section between the curves of opposite curvatures reduces deformation in tubes in the critical positions leading to lower strain, stress and failure index values.

Development of Cervical Massage Instrument imitating Manipulation

In order to meet the action effect of pushing, kneading, squeezing, pressing and rolling of nerve root type cervical spondylosis, a new type of cervical massage chair imitating manipulation treatment is developed, which adopts the structural scheme of the combination of massage handwheel and eccentric wheel. Based on NX software, the structure of each part of the cervical massage chair is designed, the virtual prototype is designed, and the finite element analysis of the transmission spindle is carried out. The results show that the structure design is reasonable, the simulation action meets the contra direction synchronous 8-shaped curve track designed by massage handwheel, and the assembly structure is reasonable without interference. Using 3D printing technology, a prototype model was made, which laid a foundation for the follow-up biomechanical analysis and clinical application.

Can Physics Help Athletes Run Faster on a Curve Track

Sprinting on a curve is slower than sprinting on a straight lane. To explain this phenomenon, various models based on a combination of biological and physical assumptions have been developed. These models depend on detailed parameters that significantly differ for each individual athlete. Here, we propose a general model solely based on kinetic theory of physics that can be universally applied to all athletes. By solving the force and torque equations for the running speed of the athletes on a curved track, we analyzed sprinting speeds between the inner and outer curves. Applying the data from the classic works into our models, we find that our results and conclusions are mostly aligned with the previous works while our approach is built on the accurate physics principles and contains no uncontrollable parameters. Further we show how runners can alleviate the centrifugal effect of curved track by tilting their bodies and we quantitatively determine the optimal tilting angle for a given curvature.

WSN-Based Vibration Characteristic Research for Various Railway Track Structures for Pattern Classification

To effectively study vibration characteristics of tracks under different track structures, wavelet transforms of the vibration data are used for pattern classification of vibration feature. First, acceleration data of the track are collected with running speed of 150[Formula: see text]km/h at 26 positions respectively on a slab tangent track, ballast tangent track and ballast curve track by a wireless sensor network (WSN). Then they are analyzed using the power spectral densities (PSDs) and wavelet-based energy spectrum analysis. The paper elaborates on the reasons for the differences of vibration energy and excitation frequencies due to the mechanism of different frequency bands and the corresponding track structures. Based on these, the instantaneous frequencies, vibration energies and durations in the low, medium, and high frequency bands are selected as the features for three track structures. A function curve representing the features is proposed to detect the abnormal track structure by a correlation analysis. Finally, the proposed method of pattern classification has been validated by experimental testings.