How is the R angle of square tube specified in the national standard?

The R angle in the square tube is the transitional arc at the junction of two planes, which is generally the half diameter of the center line of the curved arc R angle. The value of the curved arc R is generally 1.5~2.0 times the pipe diameter. The size of the R angle is determined according to the wall thickness of the square tube. The R angle is divided into internal R angle and external R angle. The internal R is generally 1.5~2 times the wall thickness. Square steel tubes with different R angles can also be produced according to the user's requirements.
For example, for a rectangular steel pipe with circular arc R, A=1.0MM, diagonal=1.15MM, how do you know the R angle? If it is a square steel pipe with arc, is the calculation method the same? A rectangle has a length of A and a width of B, a diagonal of C, and the radius of four corner arcs R is equal. Calculate the size of R by the following formula: (C/2-R) ^ 2=(A/2-R) ^ 2+(B/2-R) ^ 2 C ^ 2/4-CR+R ^ 2=A ^ 2/4-AR+R ^ 2+B ^ 2/4-BR+R ^ 2 4R ^ 2-4 (A+B-C) R+(A ^ 2+B ^ 2-C ^ 2)=0.
It should be emphasized here that the R angle of the lower rectangular tube does not refer to the arc, but the center angle. The arc refers to a segment on the circumference, and the included angle of the line between the two ends of the arc and the center is the center angle. Since the circumference of a circle is 2 π R and its corresponding center angle is 2 π, the arc length corresponding to the unit center angle is 2 π R/2 π=R. Therefore, the arc length corresponding to any central angle a (radian unit)=aR is obtained. The measuring methods and tools for square tube R angle include R gauge and projector. The R gauge can be used for thick points, the projector for fine points, and the CMM for high requirements.