A single-degree-of-freedom equation of motion was used for modeling a compliant offshore structure exposed to viscous hydrodynamic loads. The equation of motion contains nonlinearities in the forms of both Duffing sti...A single-degree-of-freedom equation of motion was used for modeling a compliant offshore structure exposed to viscous hydrodynamic loads. The equation of motion contains nonlinearities in the forms of both Duffing stiffness and Morison drag force with current. The water particle velocity and acceleration for calculating the Morison inertia and drag forces are modeled as Gaussian processes based on a Pierson-Moskowitz (P-M) elevation spectrum. The single-degree-of-freedom equation of motion containing different ocean current values are then numerically integrated via a fourth-order Runge-Kutta scheme. Time trajectories of the surge response displacements of the offshore structure and the response probability density curves are obtained. Furthermore, the ocean current influences on the response central moments up to the fourth order are studied. A literature review reveals that this is the first treatment of such a pair of nonlinearities in time domain. The simulation results are analyzed, and some conclusions valuable for engineering design are pointed out.展开更多
Using Moore-Penrose inverse theory, a set of formulations for calculating the static responses of a changed finite element structure are given in this paper. Using these formulations by structural analysis may elimina...Using Moore-Penrose inverse theory, a set of formulations for calculating the static responses of a changed finite element structure are given in this paper. Using these formulations by structural analysis may eliminate the need of assembling the stiffness matrix and solving a set of simultaneous equations.展开更多
采用Gleeble-3500对铁素体/马氏体(F/M)钢的热成形规律进行了研究。基于F/M钢热压缩应力-应变曲线,建立了F/M钢动态材料模型(dynamic material model,DMM)热加工图,并通过金相分析对热加工图进行了验证。结合热加工图和金相分析,研究了...采用Gleeble-3500对铁素体/马氏体(F/M)钢的热成形规律进行了研究。基于F/M钢热压缩应力-应变曲线,建立了F/M钢动态材料模型(dynamic material model,DMM)热加工图,并通过金相分析对热加工图进行了验证。结合热加工图和金相分析,研究了F/M钢热成形过程中的组织变化,给出了不同情况下的热加工参数:如后续需要继续大变形加工,可采用850℃、应变速率0.01 s^-1作为加工参数,该参数可生成细小、均匀且易加工的铁素体组织;如后续对F/M钢有较高的强度要求,可选取1150℃、应变速率10 s^-1作为加工参数,该参数可生成细小、均匀且高强度的马氏体。展开更多
文摘A single-degree-of-freedom equation of motion was used for modeling a compliant offshore structure exposed to viscous hydrodynamic loads. The equation of motion contains nonlinearities in the forms of both Duffing stiffness and Morison drag force with current. The water particle velocity and acceleration for calculating the Morison inertia and drag forces are modeled as Gaussian processes based on a Pierson-Moskowitz (P-M) elevation spectrum. The single-degree-of-freedom equation of motion containing different ocean current values are then numerically integrated via a fourth-order Runge-Kutta scheme. Time trajectories of the surge response displacements of the offshore structure and the response probability density curves are obtained. Furthermore, the ocean current influences on the response central moments up to the fourth order are studied. A literature review reveals that this is the first treatment of such a pair of nonlinearities in time domain. The simulation results are analyzed, and some conclusions valuable for engineering design are pointed out.
文摘Using Moore-Penrose inverse theory, a set of formulations for calculating the static responses of a changed finite element structure are given in this paper. Using these formulations by structural analysis may eliminate the need of assembling the stiffness matrix and solving a set of simultaneous equations.
文摘采用Gleeble-3500对铁素体/马氏体(F/M)钢的热成形规律进行了研究。基于F/M钢热压缩应力-应变曲线,建立了F/M钢动态材料模型(dynamic material model,DMM)热加工图,并通过金相分析对热加工图进行了验证。结合热加工图和金相分析,研究了F/M钢热成形过程中的组织变化,给出了不同情况下的热加工参数:如后续需要继续大变形加工,可采用850℃、应变速率0.01 s^-1作为加工参数,该参数可生成细小、均匀且易加工的铁素体组织;如后续对F/M钢有较高的强度要求,可选取1150℃、应变速率10 s^-1作为加工参数,该参数可生成细小、均匀且高强度的马氏体。
