Sound Wave Detection Of Glass Rubber Mixed Particulate Matter

The granular matter is a multi-body system in which a large number of macroscopic particles are aggregated.It is one of the most widely-existence aggregation states of substance on the earth.Granular matter is a typical strong dissipative non-equilibrium system leading to significant difference with Newtonian fluid or elastic solids and other continuous media.Under external disturbances,granular matter will display dynamic behaviors of several different characteristic time scales in the micro-meso-macro structure.The recognition of the principles and mechanisms of these behaviors not only helps to reveal the basic physical and mechanical properties of granular materials,but also have important practical significance of the energy conservation during production and transportation of raw materials and the prevention of natural disasters such as landslides.Acoustic detection method is an excellent non-destructive methods in detecting particle material's properties and internal structure.The propagation of acoustic signals in particle systems is influenced by multiple mechanisms of transmission,reflection,scattering,and dissipation.The signals contain various information about the macroscopic properties and microstructure of the particle system.In this dissertation,firstly,the acoustic wave measurement was performed on the single component granular material by using the time-of-flight method,and the influence of the pressure on the transmitted wave was investigated.It is found that the acoustic wave velocity meets a simple positive exponential relationship with the pressure,while the attenuation coefficient and the nonlinear coefficient has a negative exponential relationship with the pressure.At the same time,the effect of sample thickness on sound waves was studied.It is found that,as the thickness of the sample increases,the sound velocity of the sample increases first and then saturates.The wave spectrum obtained by wavelet transform shows that,as the thickness of the sample increases,the main frequency of the wave contained in the E wave gradually transitions from high frequency to low frequency.Secondly,we studied the elastic properties of the glass-rubber binary mixed particle system using acoustic wave detection.In the experiment,the mixing ratio of glass-rubber was controlled to investigate the change of modulus of glass-rubber mixed sample under axial loading.Using the time-of-flight method to measure the equivalent d ynamic elastic modulus of the mixed material.It is found that,as the ratio of rubber particle increases,sample gradually changes from the glass-like rigid behavior to the rubber-like flexible behavior.A similar result is obtained in DEM simulation which is based on the Hertz-Mindlin nonlinear contact model.The simulation calculates the particles' velocity and interaction force.Also,the intuitive force chain distribution,the probability density and coordination number distribution of the interparticle force distribution are obtained.The simulation shows that the glass particles constitute the main chain structure and the rubber particles do not participate in formation of the strong chain in low-ratio rubber particles.When the rubber particles get a large proportion,the glass particles and rubber particles constitute the main chain network structure together.The distribution of the normal contact force is relatively uniform in particles and can be considered as the glass particles suspended in the rubber particles.For such change of the elastic behavior,we used the modified effective medium theory(EMT)to make a reasonable interpretation with the spring stiffness model:the deformation of the internal particles is relatively uniform when the rubber particles in a low-ratio,the material satisfies the equal strain hypothesis and is regarded as a parallel spring model.When the rubber particles account for a large proportion,the mixed material approximately satisfies the assumption of equal stress a nd is regarded as a series spring model.The results obtained by the two models are consistent with the simulation results.