FPSO and CALM (Catenary Anchor Leg Mooring) buoy offloading systems are being extensively employed in water field of West Africa. In this paper we did some research on the response of FPSO and CALM offloading systems under special environment conditions in West Africa. It is found that Swell dominate sea state has much larger effects on wave frequency motions of FPSO than responding results introduced by Wind Sea dominate sea state, and squall and current will introduce large horizontal motions of FPSO, such as surge and sway. As for CALM, swell and wind sea mainly affect its heave and roll motions, respectively. Due to its little wind area, CALM does not show great response to Squall which is the extreme environment condition for FPSO though.
By comparing the results from OOL (Oil Offloading Line) dynamic analysis and quasi-static analysis, it could be that OOL dynamic effect has little influence on motions of FPSO. But it can bring large changes of responses of CALM because of its small water displacement which indicates coupled analysis of the whole system is necessary.
Besides, investigations on OOL fatigue have also been done, and the results show that CALM motion plays an important role on fatigue damage and life of OOL under different sea states.
Free vibration of rectangular plates with three kinds of porosity distributions and different boundary constraints has been performed by means of a semianalytical method. The distribution of porous varies along the thickness of the plate, in which the mechanical properties are defined by open-cell metal foam. Regardless of boundary conditions, displacement admissible functions are represented by combination of standard cosine Fourier series and auxiliary sine series. The kinetic energy and potential energy of plates are also expressed on the basis of first-order shear deformation theory (FSDT) and displacement admissible functions. Finally, the coefficients in the Fourier series which determine natural frequencies and modal shape are derived by means of the Rayleigh–Ritz method. Convergence and dependability of the current method are verified by comparing with the results of FEM and related literatures. In addition, some new results considering geometry parameters under classical and elastic boundary constraints are listed. The effects of geometry parameters, material parameters, and boundary constraints have been discussed in detail.
A kind of intelligent materials named magnetorheological elastomers (MREs) is applied on the surface of a rotating plate to avoid resonance vibration and to attenuate the vibration amplitude. Under a variable magnetic field, the stiffness of structure with MREs can be changed in wide range. First, the field-induced shear modulus is numerically studied and compared with the experimental results. Then, other equivalent parameters in nonlinear material equation of MREs are determined. Finally, the vibration suppression effect is verified through numerical simulation of the dynamic impact response of rotating plate in a fluid-driven deployable mechanism subjected to impact loads. On the condition that the weight of the plate is fixed, its vibration response is suppressed in shorter time than original design.
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