Circle grid analysis (CGA), also known as circle grid strain analysis, is a method of measuring the
strain levels of
sheet metal
Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes.
Thicknesses can vary significantly; ex ...
after a part is formed by
stamping or
drawing
Drawing is a visual art that uses an instrument to mark paper or another two-dimensional surface. The instruments used to make a drawing are pencils, crayons, pens with inks, brushes with paints, or combinations of these, and in more mod ...
. The name itself is a fairly accurate description of the process. Literally, a grid of circles of known diameter is
etched to the surface of the sheet metal to be formed. After the part is formed, the circles have been stretched into ellipses. By measuring the longest part of the ellipse (called the “major strain”) and the shortest part of the ellipse (called the “minor strain”), it is possible to determine how close any stamped part is to splitting or fracturing.
The goal of using circle grid strain analysis is to predict potential problems before they become problems. Once you have a forming problem, chances are circle grid analysis won’t be able to help you, unless it’s intermittent enough to form a “good” part from time to time.
See also
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Forming limit diagram A forming limit diagram, also known as a forming limit curve, is used in sheet metal forming for predicting forming behavior of sheet metal. The diagram attempts to provide a graphical description of material failure tests, such as a punched dome t ...
References
''Engineering Quality Solutions''
Mechanical engineering
Metal forming
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