Based on a model with three-degree-of-freedom, the nonlinear coupled axial-torsional vibration of drill string is numerically studied considering modified contact bit-rock interaction. The effects driving angular velocities, nominal drilling pressures, and formation stiffness response are discussed. simulation results show that can be periodic, quasi-periodic or chaotic motion variation system ...

The aim of this work is to develop an experimental method to measure in-plane surface properties on the nanometer scale by torsional resonance mode atomic force microscopy and to understand the underlying system dynamics. The invention of the atomic force microscope (AFM) and the advances in development of new AFM based techniques have significantly enhanced the capability to probe surface prop...

malian animals, i.e. that of a cat. It was also influenced by the spring-mass model representation [2]. Compliant prismatic legs show an intrinsic robustness for their angle of attack [2], they have a stability region. If the leg design is changed into a two segmented leg with a specific linear torsional spring, the leg stiffness kleg becomes nonlinear (Fig. 2(b) blue line), similar to that of ...

Acoustic metamaterials possessing subwavelength characteristics can be used for low-frequency noise and vibration control. with adjustable dynamic properties further enhance their possible applications. This paper designs a kind of tunable acoustic consisting the frame structure, airbag, balancing weight. And manipulated by tuning gauge pressure gas temperature in airbag. The calculation result...