In mechanical engineering

Mechanical engineering

Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...

, a fillet (icon) is a concave

Concave function

In mathematics, a concave function is the negative of a convex function. A concave function is also synonymously called concave downwards, concave down, convex upwards, convex cap or upper convex.-Definition:...

 easing of an interior corner of a part design. A rounding of an exterior corner is called a "round" or a "chamfer

Chamfer

A chamfer is a beveled edge connecting two surfaces. If the surfaces are at right angles, the chamfer will typically be symmetrical at 45 degrees. A fillet is the rounding off of an interior corner. A rounding of an exterior corner is called a "round" or a "radius"."Chamfer" is a term commonly...

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Applications

• Stress concentration
  Stress concentration
  A stress concentration is a location in an object where stress is concentrated. An object is strongest when force is evenly distributed over its area, so a reduction in area, e.g. caused by a crack, results in a localized increase in stress...
  
   is a problem of load-bearing mechanical parts which is reduced by employing fillets on points and lines of expected high stress. These features effectively make the parts more durable and capable of bearing larger loads.
• For considerations in aerodynamics
  Aerodynamics
  Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...
  
  , fillets are employed to reduce interference drag where aircraft components such as wings, struts, and other surfaces meet one another.
• For manufacturing, concave corners are sometimes filleted to allow the use of round-tipped end mills to cut out an area of a material. This has a cycle time benefit if the round mill is simultaneously being used to mill complex curved surfaces.
• Rounds are used to eliminate sharp edges that can be easily damaged or that can cause injury when the part is handled.

Design process

Fillets can be quickly designed onto parts using 3d solid modeling

Solid modeling

Solid modeling is a consistent set of principles for mathematical and computer modeling of three dimensional solids. Solid modeling is distinguished from related areas of Geometric modeling and Computer graphics by its emphasis on physical fidelity...

 engineering CAD software by invoking the function and picking edges of interest. Once these features are included in the CAD design of a part, they are often manufactured automatically using computer-numerical control.

Different packages use different names for the same operations. CATIA

CATIA

CATIA is a multi-platform CAD/CAM/CAE commercial software suite developed by the French company Dassault Systemes...

, Vectorworks

VectorWorks

Vectorworks is a computer-aided design and Building Information Modeling software program developed by Nemetschek Vectorworks that is used for drafting, technical drawing and 3D modeling. Vectorworks offers 2D, 3D, production management, and presentation capabilities for all phases of the design...

, Autodesk Inventor

Autodesk Inventor

Autodesk Inventor, developed by U.S.-based software company Autodesk, is 3D mechanical solid modeling design software for creating 3D digital prototypes used in the design, visualization and simulation of products...

 and Solidworks

SolidWorks

SolidWorks is a 3D mechanical CAD program that runs on Microsoft Windows and is being developed by Dassault Systèmes SolidWorks Corp., a subsidiary of Dassault Systèmes, S. A. . SolidWorks is currently used by over 1.3 million engineers and designers at more than 130,000 companies worldwide...

 refer to both concave and convex rounded edges as fillets, while referring to angled cuts of edges and concave corners as chamfers. Unigraphics and CADKEY

CADKEY

CADKEY is a 2D/3D Mechanical CAD software application released for various DOS, UNIX, and Microsoft Windows operating systems. Originally released for DOS in 1984, CADKEY was among the first CAD programs with 3D capabilities for personal computers.-History:Peter Smith and Livingston Davies founded...

 refer to concave and convex rounded edges as blends. Pro/Engineer

Pro/ENGINEER

Creo Elements/Pro, a product formerly known as Pro/ENGINEER is a parametric, integrated 3D CAD/CAM/CAE solution created by Parametric Technology Corporation . It was the first to market with parametric, feature-based, associative solid modeling software...

 refers to rounded edges simply as rounds. Other 3D solid modeling software programs outside of engineering, such as gameSpace, have similar functions.

Smooth edges connecting two simple flat features are generally simple for a computer to create and fast for a human user to specify.