Theoretical And Experimental Study On The Wave Propagation Through A Micro Gap

There are many contact interfaces in structures. The contact interface will inevitably affect the mechanical behavior of materials when materials or structures are impacted by the earthquake or the dynamic load, Therefore, the interface has a great significance on the structural dynamic response.In the present paper, the studies about the interaction of elastic waves and interfaces focus on the well-bonded interface.However, so far few studies have involved in micro-gaps between two solids. Micro-gaps can be seen as a special interface. The surface can reflect waves when incident wave is weak, which will completely block the transmission of waves; when the wave is strong enough, two surfaces will contact or partly contact, which will make the wave transmit from one side to the other side.Thus, studies on the wave propagation through a micro-gap have important theoretical and practical significance,.they can also provide the basis for vibration isolation and non-destructive evaluation.We carry out a preliminary exploration which includes the theoretical analysis and experimental study on the wave propagation through a micro-gap. Harmonic and pulse waves, the same and the different medias are.taken into account. At last we get the refracted waves in time domain and frequency domain and the amplitude of refracted waves wth the second-order frequency varying with the gap width.1)First, we conduct a theoretical analysis on harmonic waves interaction with the micro-gaps.Considering the normal incidence and the smooth interface, and we get the relationship between contact area and the gap width. At the same time, we find that, refracted waves contain all higher frequencies due to the presence of micro-gaps.The amplitude of refracted waves is strongly dependent on the gap width, the amplitude of the incident waves and the material properties. Besides, the magnitude increases as d/A0 increases until a critical value is reached and then decrease. The amplitude of the same medium(St-St) is far bigger than that of different mediums(St-Al and Al-St).2)We conduct an experimental analysis on harmonic wave interaction with the micro-gaps.The same and the different mediums are.taken into account. Due to the presence of micro-gaps, refracted waves contain all higher frequencies. The waveforms are distorted obviously. The amplitude of St-Al Experiment is far greater than that of St-St. Experiment. and these results are in good agreement with theoretical results. Three different experimental results show that:material properties not only have significant influences on the refracted waves, the order of waves through the materials will also change waveforms and nature of the wave.3) We also conduct an experimental analysis on pulse waves interaction with the micro-gaps.The same and the different mediums are taken into account. Based on the above results,we can see that, the forms of the refracted waves are distorted with higher harmonics generated. which is different from the seamless cases obviously. With the gap width increasing,The amplitude of refracted waves first increases and then decreases.The amplitude of the same medium is far bigger than that of the different mediums.