Study of contact force between drill string and borehole wall in constant-curvature wellbores;

Calculation and analysis of fatigue strength of drill string in deep well;

Study of vortex mechanism and rule of bottom drill string;

Nonlinear finite element analysis on drillstring colloiding with wellbore;

Research on How to Predict the Drillstring Fatigue Life of Whole Well with Precession and Backward Precession;

Some problems in the recent research of drillstring bifurcation;

Dynamic simulation of the contact between drill stem and well wall;

The calculation of critical compressive force of drill stem in horizontal well;

The effect of initial deflection on nonlinear lateral vibration of drill stem;

ANSYS-based finite element analysis method of longitudinal vibration of drilling string and its application;

Rules and their application of drilling string lateral vibration;

Optimization design methods of drilling strings in extended reach wells;

Particular attention has been focused on studying the mechanical behaviors of drillstrings, because drilling engineering takes high risk and invests heavily capital.

Based on the theory of large spatial deflection for elastic slender bars, the fundamental non-linear partial differential equations of drillstrings are derived.

Flexible drillstrings have been frequently used in extended reach wells,and their stability is one of the key factors to be success in drilling engineering.