Dynamic torsional response of pre-strained end bearing pile embedded in pre-strained isotropic saturated soil medium

The influence of initial strain state on the dynamic response of an end bearing pile embedded in isotropic saturated soil is investigated through the linearized theory of small elastic perturbation superposed on largely stressed bodies. The governing equations for soil, based on Blot＇s poroelasticity theory, are derived in the cylindrical coordinates, and the pile is modeled by using the one-dimensional elastic theory. The analytical solutions of pile impedance, frequency response of both twist angle and time history of velocity response are obtained by using of separation of variables technique. Finally, a parametric study of the influence of initial strains on the torsional impedance, twist angle, and velocity response at the top of the pile is carried out.

A computational study of a capsule lateral migration in microchannel flow

A numerical method is used to model a capsule migration in a microchannel with small Reynolds number Re = 0.01. The capsule is modeled as a liquid drop sur- rounded by a neo-Hookean elastic membrane. The numer- ical model combines immersed boundary with lattice Boltz- mann method （IB-LBM）. The LBM is used to simulate fixed Cartesian grid while the IBM is utilized to implement the fluid-structure interaction by a set of Lagrangian moving grids for the membrane. The effect of shear elasticity and bending stiffness are both considered. The results show the significance of elastic modulus and initial lateral position on deformation and morphological properties of a circular cap- sule. The wall effect becomes stronger as the capsule ini- tial position gets closer to the channel wall. As the elastic modulus of membrane increases, the capsule undergoes less pronounced deformation and velocity in direction x is de- creased, thus, the capsule motion is slower than the back- ground flow. The best agreement between the present model and experiments for migration velocity takes place for the capsule with normal to moderate membrane elastic modulus. The results are in good agreement with experiment study of Coupier et al. and previous numerical studies. Therefore, the IB-LBM can be employed to make prediction in vitro and in vivo studies of capsule deformation.

Specific features of SH-waves propagation in structures with prestressed inhomogeneous coating made of piezoceramics based on LiNbO_(3)

Within the framework of the linearized theory of electroelastic wave propagation,a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered.The ferroelectric LiNbO_(3) is used as the main material of the structure.The initial deformed state of the coating material is homogeneous,induced by the action of initial mechanical stresses and an external electrostatic field,the properties of the coating continuously change in thickness.By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface,the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied.The separate and combined effects of initial actions on changes in the physical properties of the structure,the transformation of the surface wave field,and the change in the SAW velocities in a wide frequency range is studied.The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures,in the optimization and design of new structures and devices on SAW with high performance characteristics.