60. plugins.section2d — Some functions operating on 2D structures.

This is a plugin for pyFormex. (C) 2002 Benedict Verhegghe

See the Section2D example for an example of its use.

class plugins.section2d.PlaneSection(F)[source]

A class describing a general 2D section.

The 2D section is the area inside a closed curve in the (x,y) plane. The curve is decribed by a finite number of points and by straight segments connecting them.

60.1. Functions defined in module plugins.section2d

plugins.section2d.sectionChar(F)[source]

Compute characteristics of plane sections.

The plane sections are described by their circumference, consisting of a sequence of straight segments. The segment end point data are gathered in a plex-2 Formex. The segments should form a closed curve. The z-value of the coordinates does not have to be specified, and will be ignored if it is. The resulting path through the points should rotate positively around the z axis to yield a positive surface.

The return value is a dict with the following characteristics:

  • L : circumference,
  • A : enclosed surface,
  • Sx : first area moment around global x-axis
  • Sy : first area moment around global y-axis
  • Ixx : second area moment around global x-axis
  • Iyy : second area moment around global y-axis
  • Ixy : product moment of area around global x,y-axes
plugins.section2d.extendedSectionChar(S)[source]

Computes extended section characteristics for the given section.

S is a dict with section basic section characteristics as returned by sectionChar(). This function computes and returns a dict with the following:

  • xG, yG : coordinates of the center of gravity G of the plane section
  • IGxx, IGyy, IGxy : second area moments and product around axes through G and parallel with the global x,y-axes
  • alpha : angle(in radians) between the global x,y axes and the principal axes (X,Y) of the section (X and Y always pass through G)
  • IXX, IYY : principal second area moments around X,Y respectively. (The second area product is always zero.)
plugins.section2d.princTensor2D(Ixx, Iyy, Ixy)[source]

Compute the principal values and directions of a 2D tensor.

Returns a tuple with three values:

  • alpha : angle (in radians) from x-axis to principal X-axis
  • IXX,IYY : principal values of the tensor