Editing Flexure

{{other uses|Flexure (disambiguation)}}{{distinguish|Bending}}
[[File:Flexure pivot.png|thumb|A flexure pivot, utilized in place of bearings for its frictionless adjustment properties.]]
[[Image:Mint box polypropylene lid.JPG|thumb|upright|A [[living hinge]] (a type of flexure), on the lid of a [[Tic Tac]] box. This hinge has one compliant [[Degrees of freedom (mechanics)|degree of freedom]].]]
A '''flexure''' is a flexible element (or combination of elements) engineered to be compliant in specific [[degrees of freedom (mechanics)|degrees of freedom]].<ref>{{cite web|url=http://web.mit.edu/mact/www/Blog/Flexures/FlexureIndex.html|title=Flexures |last=Thomas |first=Marcel |website=MIT Web |access-date=13 Feb 2017}}</ref> Flexures are a design feature used by [[design engineer]]s (usually [[mechanical engineer]]s) for providing adjustment or compliance in a design.

== Flexure types ==

Most compound flexure designs are composed of three fundamental types of flexure:<ref>{{cite web|url=http://www.precisionballs.com/Flexural_Encyclopedia.php|title=Flexural Encyclopedia |website=Bal-Tec |access-date=13 Feb 2017}}</ref>

[[File:Compound Flexure System, Linear Translation.jpg|right|thumb|Example compound flexure design with nested linkage<ref>{{cite journal |title=Eliminating Underconstraint in Double Parallelogram Flexure Mechanisms |last=Panas |first=Robert |journal=Journal of Mechanical Design |publisher=Lawrence Livermore National Laboratory |date=7 Jul 2014 |volume=137 |issue=9 |doi=10.1115/1.4030773 |osti = 1228007}}</ref>]]

* 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

{| class="wikitable"
|-
! Pin flexure !! Blade flexure !! Notch flexure
|-
| [[File:Pin Flexure.jpg|thumb|upright=0.5]] || [[File:Blade Flexure.jpg|thumb|upright=0.5]] || [[File:Notch Flexure.jpg|thumb|upright=0.5]]
|}

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 ==

In the field of [[precision engineering]] (especially high-precision [[motion control]]), flexures have several key advantages. High precision alignment tasks might not be possible when [[friction]] or [[stiction]] are present.<ref>{{cite journal |url=http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=966610&resultClick=1 |title=Three-degree-of-freedom flexure-based manipulator for high-resolution spatial micromanipulation |last=Speich|first=John |publisher=Proc. SPIE Vol. 3519 |date=5 Oct 1998 |website=SPIE Digital Library |volume=3519 |pages=82–92 |doi=10.1117/12.325750 |s2cid=110388341 |access-date=14 February 2017|url-access=subscription }}</ref> Additionally, conventional [[bearing (mechanical)|bearing]]s or [[linear slide]]s often exhibit positioning [[hysteresis]] due to [[backlash (engineering)|backlash]] and friction.<ref>{{cite web |url=https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/Zago-1997.pdf |title=Application of Flexure Structures to Active and Adaptive Opto-Mechanical Mechanisms |last=Zago |first=Lorenzo |publisher=Proc. SPIE Vol. 2871 |date=Mar 1997 |website=University of Arizona Opto-Mechanical Papers Reference |access-date=13 February 2017}}</ref> Flexures are able to achieve much lower resolution limits (in some cases measured in the [[nanometer]] scale), because they depend on [[bending]] and/or [[torsion (mechanics)|torsion]] of flexible elements, rather than surface interaction of many parts (as with a [[ball bearing]]). This makes flexures a critical design feature used in [[optical instrument]]ation such as [[interferometer]]s.

Due to their mode of action, flexures are used for limited range motions and cannot replace long-travel or continuous-rotation adjustments.<ref>{{cite web |url=https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/Mir-Presentation.ppt |title=Flexure Mounts for High Resolution Optical Elements |last=Salek |first=Mir |date=2008 |website=University of Arizona Opto-Mechanical Papers Reference |format=PPT |access-date=13 February 2017}}</ref>  Additionally, special care must be taken to design the flexure to avoid [[Yield (engineering)|material yielding]] or [[Fatigue (material)|fatigue]], both of which are potential [[failure cause|failure modes]] in a flexure design.

[[Image:leafs1.jpg|thumb|A leaf spring suspension is an example of a flexure design in [[automotive engineering]].]]

== Design examples ==
[[File:NASA MER FLEXURE WHEEL.jpg|left|thumb|Drive wheel from the [[Mars Exploration Rovers]], with integral suspension flexures.]]
[[File:NASA MSL FLEXURE WHEEL.jpg|thumb|Drive wheel from the Mars Science Laboratory rover [[Curiosity (rover)|Curiosity]], with integral suspension flexures.]]
* [[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 a [[Tic Tac]] box's lid).
* [[Leaf spring]]: Leaf Springs are commonly used in [[vehicle suspension]]s.  Leaf springs are an example of a flexure system with one compliant [[Degrees of freedom (mechanics)|degree of freedom]].
* Flex Pivot: Frictionless pivoting component, for use in precision alignment applications.<ref>{{cite web |url=http://www.flexpivots.com/ |title=Free Flex Pivot Product line |website=Riverhawk Flex Pivots |access-date=13 February 2017}}</ref>
* [[NASA]]'s [[Mars Exploration Rover]]s and the Mars Science Laboratory rover [[Curiosity (rover)|Curiosity]] have engineered flexures in their wheels which act as vibration isolation and suspension for the rovers.<ref>{{cite web |url=http://mars.nasa.gov/mer/spotlight/wheels01.html |title= Wheels in the Sky |website=NASA Jet Propulsion Laboratory |access-date=14 February 2017}}</ref>

==See also==
* [[Flexure bearing]]
*[[Compliant mechanism]]

==References==
{{reflist}}

[[Category:Mechanical engineering]]