300 likes | 932 Views
Summary. What is a flexure?Compare to other mountsBasic types of FlexureSome examples. What is a Flexure. By definition, flexure is an elastic element which provides controlled motion. Plunging to the Idea. . . . . . Lens. . Mount. . Plunging to the Idea (idea from Yoder's book). . . . . . 120
E N D
1. Flexure Mounts For High Resolution Optical Elements Mir Salek
Optomechanics
Fall 2008
3. What is a Flexure By definition, flexure is
an elastic element which
provides controlled motion
4. Plunging to the Idea
5. Plunging to the Idea (idea from Yoders book)
6. Points Equal Compliances -> Keeps the lens centered when temperature changes
The spring forces allow the lens to decenter during shocks and return afterwards
Minimize stress in optics during shocks
Typically stiff tangentionally and axially and compliant radially
Uses Kinematic principles to find the location of flexures
7. High Performance Lens Assembly Tight tolerance alignment
Maintain alignment under operational level shock, vibration, pressure, temperature change
Retain its alignment upon exposure to survival level of environmental effects
Low stress on optics (particularly mirrors)
8. Advantages of Flexure Mounts Free of slick-slip and friction effects of semi-kinematic design
Less hysteresis than rolling or sliding contacts
More robust to adverse environment effects such as extreme temperatures, vacuum, and abrasive dust
Needs very little maintenance if any
* Ideal for space applications
9. Flexure Material Should provide required compliance within length limitation
Should have high dimensional stability for repeated use in time
10. Flexure Material Should have high fracture toughness
Thermal properties to maintain operation with temperature change
11. Compliance For a given length:
Higher RTS ->maximum compliance
Reduced tensile strength is the ratio of yield strength to modulus of elasticity.
12. Dimensional Stability Material instability or room temperature creep can happen at stresses less than micro-yield strength
Andreas Beta Law predicts instability with time:
13. Flexure Design
14. Basic Flexures: Single Strip Flexure It can be used to guide both translation and rotation
The strain is a function of axial preload
16. In the table L is the flexure length;
E is the elastic modulus;
I is the moment of inertia;
P is the applied axial load;
? is the end slope of the flexure;
M is the applied torque;
d is the end displacement of the flexure;
F is the applied force;
.
17. Strain versus Axial Stressconstant force
18. Basic Flexures: Cross-Strip Rotational Hinge Two single stripped flexures at right angles provide a rotational hinge
center of rotation shifts as a function of angle of rotation
19. Cross-Strip Rotational Hinge: rotation-torque relations
20. Basic Flexures: Parallel Spring Guide Flexure A pair of parallel single strip guides provides linear translation
The range of motion is limited to 1-2mm
also the motion is not purely linear and there is a height shift as well
21. Parallel Spring Guide Flexure: Force-Displacement Relations If the force is not applied at the midpoint, the flexure would tilt as it translates
22. Basic Flexures: Cruciform Flexure Provides limited rotation in very confined spaces
23. Basic Flexures: and Tapered Uniform-Stress Cantilever Flexure It is used to provide a small range of translation motion in very confined space
24. Flexure Mount Example 1
25. Flexure Mount Example 2
26. Flexure Mount Example 3
27. Bipod Flexure Mount
28. Happy Finals