Failure analysis of polycrystalline diamond compact cutters for breaking rock by bending waves theory

The breakage mechanism of the polycrystalline diamond compact(PDC) cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by using the cutter at three kinds of negative fore angles of 30°, 45° and 60°. The results show that, when the edge of the PDC layer is broken, the layer of tungsten cobalt is broken a little under the angle of 30°, while the layer of tungsten cobalt is broken continuously under the angle of 60°, their maximum depths are about 2 and 7 mm respectively in the two cases. The eccentric distance mainly depends on the negative fore angle of the cutter. When the cutter thrusts into the rock under an attack angle of 60°, the energy of bending waves reaches the maximum since the eccentric distance is the maximum. So the damage of cutter is the most serious. This test result is consistent with the conclusion of theoretical analysis well. The eccentric distance from the axial line of cutter to the point of action between the rock and cutter has great effect on the breakage of the cutter. Thus during the process of cutting, the eccentric distance should be reduced to improve the service life of PDC cutters.

EXPERIMENTAL STUDY ON CRACK CURVING PROPAGATION IN BENDING BEAMS UNDER IMPULSIVE LOAD

Dynamic fracture behaviour of crack curving in bent beams has been investigated. In order to understand the propagation mechanism of such cracks under impact, an experimental method is used that combines dynamic photoelasticity with dynamic caustics to study the interaction of the flexural waves and the crack. From the state change of the transient stresses in polymer specimen, the curving fracture in the impulsively loaded beams is analyzed. The dynamic responses of crack tips are evaluated by the stress intensity factors for the cracks running in varying curvature paths under bending stress wave.

Strength Analysis of Turret Mooring Productive/Storage Tanker

The longitudinal strength of turret mooring productive/storage tanker is studied. A numerical example has been implemented according to the method presented in this paper to give practical illustration. From the results of the numerical example, it is concluded that the turret hole located near the forward of the amidships has small effect on the longitudinal strength of the ship hull. As for design extreme value of wave bending moment of storage tanker, statistic method is a more reasonable methodology, especially with the consideration of the servere environmental conditions. The primary estimation of design section modulus of turret storage tanker can be determined by this design bending moment.

Bending waves of a rectangular piezoelectric laminated beam

A simple nonlinear model is proposed in this paper to study the bending wave in a rectangular piezoelectric laminated beam of infinite length.Based on the constitutive relations for transversely isotropic piezoelectric materials and isotropic elastic materials,combined with some electric conditions,we derive the bending wave equation in a long rectangular piezoelectric laminated beam by using energy method.The nonlinearity considered is geometrically associated with the nonlinear normal strain in the longitudinal beam direction.The shock-wave solution,solitary-wave solution and other exact solutions of the bending wave equation are obtained by the extended F-expansion method.And by using the reductive perturbation method we derive the nonlinear Schrodinger(NLS)equation,further more,the bright and dark solitons are obtained.For those soliton solutions,and some parameters derived by the process of solving soliton solutions,some conclusions are drawn by numerical analysis with some fixed conditions.

Giant Magnetostrictive Material Loudspeaker System Acoustic Radiation Simulation

An infinite panel model of giant magnetostrictive material loudspeaker system （GMMLS） is proposed by making use of finite element method（FEM）. Bending wave eigenfunction is introduced to describe the acoustic radiation condition of the panel. Far-field response in different conditions is calculated by changing the mass surface density. Conclusion is obtained by analyzing the curves simulated, that panel which has larger mass surface density can hardly generate far-field acoustic radiation for lower frequency, while the panel has smaller mass surface density generates far-field acoustic radiation for lower frequency evenly and stronger.

Bending wave intensity in a thick beam

In this paper the expressions are derived for estimating bending wave intensity and its components at arbitrary frequency in one-dimensional structures such as beams. There is a critical frequency fo above which there are two bending waves with different wave numbers propagating along a structure and the estimates of bending wave intensity and its components become quite complicated, and it may not be possible to measure bending wave intensity using the existing intensity techniques. The expressions are also derived for calculating approximate estimate error resulting from using the existing intensity theory. To verify the theoretical results, a series of measurements was carried out on a masonry column under laboratoryconditions.

The measurement of bending wave intensity in a two-dimensional structure

In a two-dimensional bending wavefield, the intensity vector is the sum of the effec-tive intensity vector and the intensity variation vector. The effective intensity vector gives the magnitude and direction of bending wave power flow per unit width in structures. The illtensity variation vector characterizes the circulation of local bending wave energy and varies harmon ically with space and wavenumber. This paper studies the relationship between the analysis frequency bandwidth and the measurement acctiracy of effective bending wave intensity, and ex-amines the accuracy of source localization using measured intensity vectors in two-dimensional structures. It is shown that if the analysis frequency bandwidth is wider than the sum of several one-third octave frequency bandwidths, the intensity variation can be suppressed to a negligible value in comparison with the effective intensity Moreover, a structure-borne source can be localized by measuring effective bending wave intensity vectors at a few positions, but the accuracy is dependent on the analysis frequency bandwidth, the property of the wavefield and the distance between source and measurement position. The more active the wavefield, the higher the accuracy of 8ource localization.

Resuspension of spherical particles due to surface vibration

In this study,particle resuspension due to surface vibration was investigated.A spherical particle was assumed to rest on top of a thin plate,and an external vibrating force was applied normal on the plate at t=0 and at distance R from the particle.The external driving force created a displacement field in both time and space domains,where deformations in the body of the plate were considered small elastic oscillations that are perpendicular to the propagation of the displacement.Free oscillations were introduced via the theory of elasticity and the creation of waves on thin plates,i.e.,bending waves.Particle motion in the vertical direction was initiated through plate displacement,provided that inertia due to particle mass is overcome.In particular,the particle was assumed to oscillate with a force(of oscillation)estimated via Newton’s second law of motion,comprising of two components:the acceleration due to the plate displacement and the particle mass.Subsequently,a simple force balance method was used to determine the conditions for resuspension.Accordingly,resuspension occurs when the oscillation force exceeds the couple of the adhesive and gravitational forces.The results suggest that the plate displacement depends on the characteristics of the applied force,material properties,and plate thickness.In addition,it was found that the oscillation force is substantially lower than the applied force and that it depends on plate displacement and particle mass.Additionally,the particle size significantly influencedthe outcome of resuspension.Thus,resuspension is favorable for large particles,strong applied forces,and high forcing frequencies.