5 In 1983, E.E. Fitchard and S.A. Fitchard introduced a formula to calculate borehole torsion applied to a cylindrical helix trajectory (OGJ, Jan. 17, 1983, pp. 121-124). In the following 10 years ...

The hypothesis used in developing the stress and strain in the shaft is that all points on a cross-section of the shaft experience the same angle of twist. The angle of twist for a section of length L ...