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The paper presents a finite element simulation for research in the so-called chessboard effect of plastic strain localization. In the simulation, we consider a polycrystal metal strip under uniform tension on the assumption of a normal yield stress distribution over its grains. Using the simplest isotropic model, it is taken that all grains have the same linear hardening coefficient. The simulation results demonstrate that whether the problem statement is two- or three-dimensional the material reveals plastic strain localization in the form of numerous intersecting bands arranged into a chessboard system on the initially flat specimen surface. [ABSTRACT FROM AUTHOR]

The paper proposes a new graphene resonator circuit which operates on the principle of a self-oscillator and has no drawbacks typical of nanoresonators as mass detectors and associated with their law quality factor, eigenfrequency errors (measurements from resonance curves), and dependence of quench frequency on oscillation frequency (curves with quenching for nonlinear systems). The proposed circuit represents a self-oscillator comprising an amplifier, a graphene resonator, and a positive feedback loop with a graphene oscillation transducer, and its major advantage is in self-tuning to resonance frequency at slowly varying resonator parameters, compared to oscillation periods. The graphene layer with a conducting substrate beneath it forms a capacitor which is recharged by a dc voltage source as its capacitance varies due to graphene deformation, and the recharge current is an oscillation- dependent signal transmitted from the transducer to the amplifier input. The graphene layer is placed in a magnetic field and is deformed when a current from the amplifier output is passed through. By properly choosing the magnetic field direction and the amplifier gain, it is possible to provide swinging oscillation whose amplitude is limited by the amplifier nonlinearity. For the proposed system we present an electromechanical model, dimensionless equations of motion, and numerical data demonstrating the generation of steady-state oscillations with eigenfrequency. Also presented is an analysis showing that the system can have only one limit cycle and that this cycle is always stable. The proposed resonator circuit can be used as a mass detector which determines the added mass from a change in self-oscillation frequency. [ABSTRACT FROM AUTHOR]