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Suspension System of Railway Vehicle

By on May 15, 2013

Movement of Railway vehicle on Rail is a guided movement, different as compared to road. This system is complex with having many degrees of freedoms making the study of vehicle dynamics a challenging subject from the beginning of industrial revolution

Mechanical system provides
  • Transfer and balancing of vertical Load
  • Guidance and automatic steering of vehicle along the track with varying profile
  • Support and damp the vibration due to track irregularities, curves, switches and impact between vehicle
  • Application and transfer of tractive and braking effort
  • And in totality safe and comfort travel measured through riding index
Mechanical system consists of
  • Wheel Sets
  • Axle Box
  • Elastic Suspension with dampers
  • Connection between bogie and vehicle
  • Brakes
  • Support Traction Drive
  • Transmit Tractive and Braking Effort
Modes of Vibration

Vibration and oscillation are two terms generally talked about while discussion unusual behavior of running vehicle. The difference between the two lies

Vibration: It is the repetitive motion of a body which may or may not be periodic. A vibrating body may not have a definite time period. Also the amplitude of vibration is generally small and changes with time. Example: The vibrating string of a guitar.

Oscillation: It is the periodic motion of a body about a mean position. It has a definite time period of oscillation and the amplitude remains constant. Example: A freely oscillating pendulum.

A rolling stock is subjected to the vibration in all the axis and named as follows

X Axis In Line with X axis Translational Motion- Accelerating or braking
Around X axis Rolling
Y Axis In Line with Y axis Lateral oscillation
Around Y axis Pitching
Z Axis In Line with Z axis Bouncing
Around Z axis Nosing

vibration Diagram

Mechanical Resonance

A system consists of mass and spring. It get disturbed with application of external force and vibrates. During vibration cycle, there is continuous interchange of energy between mass and spring at a fixed frequency called natural frequency. If the external force is repetitive and its natural frequency is same as that of natural frequency and in phase, amplitude of vibration goes very high to dangerous level. This results in developing alternate stresses on the components of the system resulting local hardening and brittle, which ultimately results in fatigue failure. For this reason, in Railway Engineering, natural frequency of the system is usually very high or low as compared to natural frequency of the exciting force. For this reason, dampers are used to control the amplitude of vibration when the system is passing through range of natural frequencies.

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