The ways in which to determine twist angle for twisted profiles:
- Section Axis Definition - Each profile has a section axis
composed of Web Face normal (H), Flange Face Normal
(V) and, the Third direction (T) which is along the
tangent direction of the Profile trace.
- Nomenclature:
H: Normal to
WebInner- face of profile and pointing to
WebInner+ face.
V: Normal to
Molded Flange2 face of profile and pointing to
MoldedFlange1 face.
T: Line Tangent to Profile trace.
- Twist Angle Measurement - Looking into the direction of the
Profile trace (from End of profile to Start of Profile), we see the cross section of End
Face of Profile at an angle to the Start Face of Profile.
Twist angle = Angle measure from H
Axis of End Section to H Axis of Start Section. Angle measures
counterclockwise while looking from the End section toward the Start section.
The
display of angle value in Workshop documents is as per the Units defined in preferences.
- Straight Profile trace - For this data, the Tangent
direction of Section axis at start and end of profile are collinear. Hence the Twist
angle is equal to the angle measured between the H direction
of the Section axis at start and end.
- Curved Profile trace - The
MoldedFlange2 face and WebInner-
face of profile are nonplanar.
Computation of the Twist angle with the following steps:
- Translate the Section axis at start to origin of Section axis at End of
profile.
- Rotate the translated Start section axis such that the Tangent
(T) the line of the Start Section axis is collinear with the
Tangent (T) line of the End Section axis.
At the end of these translation and rotation maneuvers, the
result.
By
Viewing in the direction opposite to the Profile Tangent Trace at the Profile end,
we see the following twist in the Profile section.
Twist angle = The angle measured in counterclockwise between the
H direction of the Section axis. Example between
HE and H`S in this case.