3.3.2 Flexible element analysis
The flexible element layout and calculating scheme is shown in Fig 12.
Fig 12 . A “squirrel-weel” type flexible element.
a) design scheme and main dimensions; b) loaded bar displacements; c) cylinder involute view
An FE stiffness can be calculated by
n - number of bars;
a, b, l - width, thickness and length of a bar accordingly;
E - Young module of the bar material at operating temperature.
- correction coefficient, depending on the flexible
Maximal alterating stress in the bar,
where; n = 0 or 1
d - radial clearance
Static displacement under the support weight G loading
d0 = G/K .
Static stress in a bar under the weight loading
To balance the weight displacement as to center the bearing its initial location is to be preliminary moved d0 upwards.
Fatigue margin is determined by dynamic sa and static sm stresses
- fatigue limit of a flat coupon;
s-1 - - fatigue limit of a standard circle coupon;
ys - material sensitivity to the fatigue cycle non-symmetry;
- fatigue resistance coefficient;
ks - effecttive stress concentration;
- surface state coefficient;
- scaling factor.
Sometimes fatigue and stiffness requirements contradict each other. If so a "two-stores" design can be recommended which is a support furnished with two co-axial “squirrel-cages”.