Analysis of local stability of telescopic boom based on cubic NURBS curve

HUANG Xin-lei， JI Ai-min， YIN Xu， SUN Peng-fei
（College of Mechanical and Electronic Engineering， Hohai University， Changzhou 213022， China）

Abstract： Aiming at the problem of which cross-section shape needs to be used in order to increase the local stability of boom of truck crane，the non-uniform rational B-splines（NURBS）curve was exploited to model the cross-section shape of boom and ANSYS software was applied to the analysis of local stability of boom. Firstly，the knot vector of cubic NURBS curve was obtained by accumulated chord length method，then the weights and control points were worked out by reverse technology，thus the cubic NURBS curve function of the lower cover cross-section of truck crane's telescopic boom was established. Secondly，with APDL command flow，various curve shaped cross-section of boom were gotten by adjusting the cubic NURBS curve's coordinates of the control points and the size of the weights，then the buckling eigenvalue was calculated，so the critical stresses of boom and its variation were gained. Finally，the increased value of the critical stresses from a hexagonal cross-section to a dodecagon cross-section，then to a curve cross-section was obtained. The results indicate that the method can solve the problem of the local stability of curve shaped cross-section boom of crane.
Key words： non-uniform rational B-splines（NURBS）； truck cranes； telescopic boom； local stability； APDL