Flexure
Aflexureis a flexible element (or combination of elements) engineered to be compliant in specificdegrees of freedom.[1]Flexures are a design feature used bydesign engineers(usuallymechanical engineers) for providing adjustment or compliance in a design.
Flexure types
[edit]Most compound flexure designs are composed of three fundamental types of flexure:[2]
- Pin flexure - a thin bar or cylinder of material, constrains three degrees of freedom when geometry matches a notch cutout
- Blade flexure - thin sheet of material, constrains three degrees of freedom
- Notch flexure - thin cutout on both sides of a thick piece of material, constrains five degrees of freedom
| Pin flexure | Blade flexure | Notch flexure |
|---|---|---|
 |
 |
 |
Since single flexure features are limited both in travel capability and degrees of freedom available, compound flexure systems are designed using combinations of these component features. Using compound flexures, complex motion profiles with specific degrees of freedom and relatively long travel distances are possible.
Design aspects
[edit]In the field ofprecision engineering(especially high-precisionmotion control), flexures have several key advantages. High precision alignment tasks might not be possible whenfrictionorstictionare present.[4]Additionally, conventionalbearingsorlinear slidesoften exhibit positioninghysteresisdue tobacklashand friction.[5]Flexures are able to achieve much lower resolution limits (in some cases measured in thenanometerscale), because they depend onbendingand/ortorsionof flexible elements, rather than surface interaction of many parts (as with aball bearing). This makes flexures a critical design feature used inoptical instrumentationsuch asinterferometers.
Due to their mode of action, flexures are used for limited range motions and cannot replace long-travel or continuous-rotation adjustments.[6]Additionally, special care must be taken to design the flexure to avoidmaterial yieldingorfatigue,both of which are potentialfailure modesin a flexure design.
Design examples
[edit]
- Living hinge:Flexure which acts as a hinge. Preferred for their simplicity, as they can be included as a feature in a single piece of material (as in aTic Tacbox's lid).
- Leaf spring:Leaf Springs are commonly used invehicle suspensions.Leaf springs are an example of a flexure system with one compliantdegree of freedom.
- Flex Pivot: Frictionless pivoting component, for use in precision alignment applications.[7]
- NASA'sMars Exploration Roversand the Mars Science Laboratory roverCuriosityhave engineered flexures in their wheels which act as vibration isolation and suspension for the rovers.[8]
See also
[edit]References
[edit]- ^Thomas, Marcel."Flexures".MIT Web.Retrieved13 Feb2017.
- ^"Flexural Encyclopedia".Bal-Tec.Retrieved13 Feb2017.
- ^Panas, Robert (7 Jul 2014). "Eliminating Underconstraint in Double Parallelogram Flexure Mechanisms".Journal of Mechanical Design.137(9). Lawrence Livermore National Laboratory.doi:10.1115/1.4030773.OSTI1228007.
- ^Speich, John (5 Oct 1998)."Three-degree-of-freedom flexure-based manipulator for high-resolution spatial micromanipulation".SPIE Digital Library.3519.Proc. SPIE Vol. 3519: 82–92.doi:10.1117/12.325750.S2CID110388341.Retrieved14 February2017.
- ^Zago, Lorenzo (Mar 1997)."Application of Flexure Structures to Active and Adaptive Opto-Mechanical Mechanisms"(PDF).University of Arizona Opto-Mechanical Papers Reference.Proc. SPIE Vol. 2871.Retrieved13 February2017.
- ^Salek, Mir (2008)."Flexure Mounts for High Resolution Optical Elements"(PPT).University of Arizona Opto-Mechanical Papers Reference.Retrieved13 February2017.
- ^"Free Flex Pivot Product line".Riverhawk Flex Pivots.Retrieved13 February2017.
- ^"Wheels in the Sky".NASA Jet Propulsion Laboratory.Retrieved14 February2017.