Closed-Form Transient Response of One-Dimensional Continua

Author(s):  
Xuqiang Wu ◽  
Bingen Yang

Abstract Exact and closed-form transient response of general one-dimensional distributed dynamic systems subject to arbitrary external, initial and boundary disturbances is determined. Non-self-adjoint operators characterizing damping, gyroscopic and circulatory effects, and eigenvalue-dependent boundary conditions are considered. Through introduction of augmented operators, a closed-form modal expansion of the displacement and internal forces of the distributed system is derived. The eigenfunction expansion is realized in a spatial state-space formulation, which systematically yields exact eigensolutions, eigenfunction normalization coefficients, and modal coordinates. The proposed method is illustrated on a cantilever beam with end mass, damper and spring.

1987 ◽  
Vol 54 (3) ◽  
pp. 513-518 ◽  
Author(s):  
T. Belytschko ◽  
Xiao-Jun Wang ◽  
Z. P. Bazant ◽  
Y. Hyun

Closed-form solutions are presented for the transient response of rods in which strain softening occurs and the stress-strain laws exhibit nonvanishing stresses after the strain-softening regime. It is found that the appearance of any strain softening results in an infinite strain rate if the material is inviscid. For a stress-strain law with a monotonically decreasing stress the strains are infinite also. If the stress increases after the strain-softening portion, the strains remain finite and the strain-softening point moves through the rod.


1996 ◽  
Vol 63 (4) ◽  
pp. 997-1003 ◽  
Author(s):  
Bingen Yang

An analytical method is developed for closed-form estimation of the transient response of complex distributed parameter systems that are nonproportionally damped, and subject to arbitrary external, initial, and boundary excitations. A new modal analysis leads to the Green’s function formula for the distributed system and an eigenfunction expansion of the system Green’s function. The legitimacy of the modal expansion is also shown.


Author(s):  
Xuqiang Wu ◽  
Bingen Yang

Abstract A closed-form transient analysis of one-dimensional distributed dynamic systems is presented. The proposed approach, called the Z-Prime Method, starts with inverse Laplace transform of a distributed transfer function formulation. Through establishment of a relation between transfer function residues and system eigensolutions, the closed-form transient response of the distributed system under general external, boundary and initial disturbances is obtained. Unlike conventional modal expansion, the proposed method does not depends on any orthogonal eigenfunctions.


2009 ◽  
Vol 18 (07) ◽  
pp. 1263-1285 ◽  
Author(s):  
GUOQING CHEN ◽  
EBY G. FRIEDMAN

With higher operating frequencies, transmission lines are required to model global on-chip interconnects. In this paper, an accurate and efficient solution for the transient response at the far end of a transmission line based on a direct pole extraction of the system is proposed. Closed form expressions of the poles are developed for two special interconnect systems: an RC interconnect and an RLC interconnect with zero driver resistance. By performing a system conversion, the poles of an interconnect system with general circuit parameters are solved. The Newton–Raphson method is used to further improve the accuracy of the poles. Based on these poles, closed form expressions for the step and ramp response are determined. Higher accuracy can be obtained with additional pairs of poles. The computational complexity of the model is proportional to the number of pole pairs. With two pairs of poles, the average error of the 50% delay is 1% as compared with Spectre simulations. With ten pairs of poles, the average error of the 10%-to-90% rise time and the overshoots is 2% and 1.9%, respectively. Frequency dependent effects are also successfully included in the proposed method and excellent match is observed between the proposed model and Spectre simulations.


Author(s):  
Scott Bair ◽  
M. M. Khonsari

Exact, closed form one-dimensional Reynolds equations are presented for the Ostwald-DeWaele model, Ellis model, Spriggs model and the double-Newtonian Rabinowitsch and Ferry models. From numerical solutions for flow rate, an approximate Reynolds-Carreau equation is obtained.


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