关键词: buckling, impact, finite time, Hamiltonian system, Saint Venant problem, Symplectic, eigenvalue problem, elastic column, stability, Hoff problem, stability criterion, dynamic buckling

Abstract:

The existing theories of finite-time stability depend on a prescribed bound on initial disturbances and a prescribed threshold for allowable responses. It remains a challenge to identify the critical value of loading parameter for finite time instability observed in experiments without the need of specifying any prescribed threshold for allowable responses. Based on an energy balance analysis of a simple dynamic system, this paper proposes a general criterion for finite time stability which indicates that finite time stability of a linear dynamic system with constant coefficients during a given time interval[0, t_f] is guaranteed provided the product of its maximum growth rate (determined by the maximum eigen-root p₁ >0) and the duration t_f does not exceed 2, i.e., p₁t_f <2. The proposed criterion (p₁t_f=2) is applied to several problems of impacted buckling of elastic columns:(i) an elastic column impacted by a striking mass, (ii) longitudinal impact of an elastic column on a rigid wall, and (iii) an elastic column compressed at a constant speed ("Hoff problem"), in which the time-varying axial force is replaced approximately by its average value over the time duration. Comparison of critical parameters predicted by the proposed criterion with available experimental and simulation data shows that the proposed criterion is in robust reasonable agreement with the known data, which suggests that the proposed simple criterion (p₁t_f=2) can be used to estimate critical parameters for finite time stability of dynamic systems governed by linear equations with constant coefficients.

Key words: finite time, elastic column, stability, Hamiltonian system, Saint Venant problem, Symplectic, eigenvalue problem, impact, Hoff problem, buckling, dynamic buckling, stability criterion