Experimental study and numerical simulation on compressive buckling behavior of thin steel skins in unilateral contact with rigid constraints

In this paper,a practical test and finite element analysis has been undertaken to further investigate the effects of contact buckling.A test rig was designed and constructed to record vertical and transverse deflections of compressively loaded steel skin plates.The boundary conditions were modeled as fully fixed.A finite element analysis was also undertaken using the software package Strand7.Results from both analyses have been examined and compared to data established from previous studies on contact buckling.Both the finite element analysis and practical results correlate well with this data.The result of the investigation has confirmed contact buckling theories and has foreshadowed the onset of the newly observed phenomenon of secondary contact buckling.

Dynamic modeling and analysis of the 3-PRS power head based on the screw theory and rigid multipoint constraints

This study presents a dynamic modeling and analysis methodology for the 3-PRS parallel mechanism.First,an improved reduced dynamic model of component substructures is proposed using the dynamic condensation technique and the rigid multipoint constraints at the joint/interface level,leading to a minimum set of generalized coordinates for external nodes.Next,the mapping between interface constraint stiffness and global stiffness is illustrated,resulting in an analytical stiffness model of joint substructures.Subsequently,the derived component and joint substructures are synthesized into the entire mechanism based on the Lagrange equation.Finally,a case study illustrates that the lower-order dynamic performances predicted within the proposed approach have the same trend as those obtained from a complete-order finite element model.The root mean square discrepancy of the lower-order natural frequencies between the two models is less than 5.92%,indicating the accuracy and effectiveness of the proposed model.The developed approach can highly and efficiently predict the dynamic performance distributions across the entire workspace and guide the optimal functional design under the virtual machine framework.

Rigidity Constraints for Large Mesh Deformation

It is a challenging problem of surface-based deformation to avoid apparent volumetric distortions around largely deformed areas. In this paper, we propose a new rigidity constraint for gradient domain mesh deformation to address this problem. Intuitively the proposed constraint can be regarded as several small cubes defined by the mesh vertices through mean value coordinates. The user interactively specifies the cubes in the regions which are prone to volumetric distortions, and the rigidity constraints could make the mesh behave like a solid object during deformation. The experimental results demonstrate that our constraint is intuitive, easy to use and very effective.