A flexure is a flexible element (or combination of elements) engineered to be compliant in specific degrees of freedom. [1] Flexures are a design feature used by design engineers (usually mechanical engineers) for providing adjustment or compliance in a design.
Most compound flexure designs are composed of three fundamental types of flexure: [2]
| 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.
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. [4] Additionally, conventional bearings or linear slides often exhibit positioning hysteresis due to backlash and friction. [5] 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 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 instrumentation such as interferometers.
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 avoid material yielding or fatigue, both of which are potential failure modes in a flexure design.
A machine is a physical system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules, such as molecular machines. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power, and include a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement. They can also include computers and sensors that monitor performance and plan movement, often called mechanical systems.
A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation, with all other translations or rotations prevented; thus a hinge has one degree of freedom. Hinges may be made of flexible material or moving components. In biology, many joints function as hinges, such as the elbow joint.
A flexure bearing is a category of flexure which is engineered to be compliant in one or more angular degrees of freedom. Flexure bearings are often part of compliant mechanisms. Flexure bearings serve much of the same function as conventional bearings or hinges in applications which require angular compliance. However, flexures require no lubrication and exhibit very low or no friction.
A conventional fixed-wing aircraft flight control system (AFCS) consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered flight controls as they change speed.
Lead selenide (PbSe), or lead(II) selenide, a selenide of lead, is a semiconductor material. It forms cubic crystals of the NaCl structure; it has a direct bandgap of 0.27 eV at room temperature. A grey solid, it is used for manufacture of infrared detectors for thermal imaging. The mineral clausthalite is a naturally occurring lead selenide.
A mirror mount is a device that holds a mirror. In optics research, these can be quite sophisticated devices, due to the need to be able to tip and tilt the mirror by controlled amounts, while still holding it in a precise position when it is not being adjusted.
Vibration isolation is the prevention of transmission of vibration from one component of a system to others parts of the same system, as in buildings or mechanical systems. Vibration is undesirable in many domains, primarily engineered systems and habitable spaces, and methods have been developed to prevent the transfer of vibration to such systems. Vibrations propagate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others. Passive vibration isolation makes use of materials and mechanical linkages that absorb and damp these mechanical waves. Active vibration isolation involves sensors and actuators that produce disruptive interference that cancels-out incoming vibration.
The rocker-bogie system is the suspension arrangement developed in 1988 for use in NASA's Mars rover Sojourner, and which has since become NASA's favored design for rovers. It has been used in the 2003 Mars Exploration Rover mission robots Spirit and Opportunity, on the 2012 Mars Science Laboratory (MSL) mission's rover Curiosity, the Mars 2020 rover Perseverance and ISRO's Chandrayaan-3 rover Pragyan in 2023.
Multibody system is the study of the dynamic behavior of interconnected rigid or flexible bodies, each of which may undergo large translational and rotational displacements.
In mechanical engineering, a kinematic chain is an assembly of rigid bodies connected by joints to provide constrained motion that is the mathematical model for a mechanical system. As the word chain suggests, the rigid bodies, or links, are constrained by their connections to other links. An example is the simple open chain formed by links connected in series, like the usual chain, which is the kinematic model for a typical robot manipulator.
A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm; the arm may be the sum total of the mechanism or may be part of a more complex robot. The links of such a manipulator are connected by joints allowing either rotational motion or translational (linear) displacement. The links of the manipulator can be considered to form a kinematic chain. The terminus of the kinematic chain of the manipulator is called the end effector and it is analogous to the human hand. However, the term "robotic hand" as a synonym of the robotic arm is often proscribed.
In mechanical engineering, a compliant mechanism is a flexible mechanism that achieves force and motion transmission through elastic body deformation. It gains some or all of its motion from the relative flexibility of its members rather than from rigid-body joints alone. These may be monolithic (single-piece) or jointless structures. Some common devices that use compliant mechanisms are backpack latches and paper clips. One of the oldest examples of using compliant structures is the bow and arrow.
In engineering, a mechanism is a device that transforms input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components which may include:
Harold Holcroft was an English railway and mechanical engineer who worked for the Great Western Railway (GWR), the South Eastern and Chatham Railway (SECR) and the Southern Railway (SR).
TracePro is a commercial optical engineering software program for designing and analyzing optical and illumination systems. The program's graphical user interface (GUI) is 3D CAD-based creating a virtual prototyping environment to perform software simulation before manufacture.
The Holcroft valve gear was a type of conjugated valve gear designed and patented by Harold Holcroft and used on three-cylinder steam locomotives of the South Eastern & Chatham Railway (SECR). It bore many similarities to the Gresley conjugated valve gear, which it predated, as eventually used on all Gresley's three cylinder designs. It varied from the Gresley method of operation by using the combination lever assembly instead of the valve spindles to drive the middle cylinder of a three-cylinder design. This had operational advantages over Gresley's design, namely eliminating the problems of flexure, bush wear and the influence of heat in the valve spindles.
Strain wave gearing is a type of mechanical gear system that uses a flexible spline with external teeth, which is deformed by a rotating elliptical plug to engage with the internal gear teeth of an outer spline.
A deployable structure is a structure that can change shape so as to significantly change its size.
Larry L. Howell is a professor and Associate Academic Vice President (AAVP) at Brigham Young University (BYU). His research focuses on compliant mechanisms, including origami-inspired mechanisms, microelectromechanical systems, medical devices, space mechanisms, and developable mechanisms. Howell has also conducted research in lamina emergent mechanisms and nanoinjection. He received a bachelor's degree in mechanical engineering from BYU and master's and Ph.D. degrees from Purdue University. His Ph.D. advisor was Ashok Midha, who is regarded as the "Father of Compliant Mechanisms."
Flexure may refer to: