Rail Vehicle Dynamics Flashcards
Why is the subject of vehicle track interaction important?
Poor running behavior leads to: Poor comfort High track forces - large track irregularities High waer
How can the track be vehicle friendly?
Low irregularities
High curve radii
Long transition curves
Low stiffness?
What factors affect track stiffness?
Track components
Temperature?
Humidity?
Soil?
What track features make the vehicle track interaction dynamic as the vehicle runs along the track?
Track irregularities
Track flexibility
Vehicle suspension
Self steering with conical wheels?
What is track twist?
Twist is the difference in can’t between to cross-sections of track decided by distance
Why do track irregularities increase over time for most track designs?
Soil settlement
Dynamic forces
Wear
How can wheelset structural flexibility affect the vehicle track interaction?
Chapter 6.2
How is the vertical air spring stiffness affected by increasing air pressure, air volume,
Cross sectional area
Vertical spring stiffness almost proportional to load
Softer for higher volume
Cross section? 3.4.3
What is meant by structural flexibility in a multi body dynamics context?
It means Bodys have finite stiffness. They are not perfectly rigid as usually assumed for simplicity reasons.
Lateral track plane acceleration equation
ay = v^2/R -g*ht/2b0
Simplified equation for jerk (in transition curve)
å = v/L * ay,0
ay,0 = track plane acceleration on circular curve
Cant excess in equations
he= ht-heq
he= -2b0/g * ay
Permissible track plane acceleration
Category A: 0.65m/s2
B: 0.98
S: 1.6
How should conicity, longitudinal primary stiffness and wheel base be chosen to achieve high critical speed?
Conicity: low (0.1?)
kyp: high?
Wheel base: long
How should conicity, longitudinal primary stiffness and wheel base be chosen to achieve good curving performance?
Conicity: high(0.4?)
kyp: low?
Wheel base: short
Klingel equation for one wheelset
Lw = 2π sqrt(b0r0/λ)
Klingel equation for a stiff bogie
L0, stiff = 2π sqrt(b0r0/λ) sqrt(1+(a/b0)^2)
What is meant by the half space assumption?
The contact patch is small compared to typical dimensions of the contact partners. Semi infinite bodies limited by a straight plane is assumed.
Typical cant for non-dedicated lines
150 mm
in which frequency range of vertical motions is the risk for motion sickness most pronounced?
0.1-0.3 Hz
