The Transmission Characteristics Of Elastic Waves In Elliptic Phononic Crystal Plate

Mechanical vibration is not only harmful to the accuracy and reliability ofmachinery and equipment,but also will reduce the service life of machinery andequipment,which is urgent problem to solve in the field of mechanical engineeringall the time.Artificial periodic structure material phononic crystal’s elastic waveband gaps provides new ideas for solving this problem.Phononic crystal also hassome special properties,such as defect mode,negative refraction,soundfocusing,acoustic diode,these characteristics have great potential application valuein noise reduction materials and the special acoustic devices,etc.Propagation of lambwaves in phononic crystal has acoused wide interest in many relevant scientificresearch workers in recent years.Unlike body waves phononic crystal,the elasticwave energy of lamb waves phononic crystal completely localized on board up anddown between the free surface,which greatly reduced in the process of elastic wavepropagation in energy consumption.The scattering body focused on circle and squareshape in the traditional research on phononic crystals,in order to explore theinfluence of other shape on the band structure,we study ellipse scattering bady.Bychanging the relevant paramaters we can get more wider and lower frequency bandgap.We use the plane wave expansion method and the finite element method to studythe Bragg scattering phononic crystals and local resonance phononic crystals.Tryingto provide theoretical guidance in designing the preparation of large band gap andlow frequency performance phononic crystal.(1) We use the classic plane wave expansion method studing the band structureof lamb waves in the Bragg elliptic phononic crystals.Compared with circularscatterer under the same conditions,elliptic phononic crystal can produce wider bandgap.Ellipse filling rate,the ratio of short axis and long axis,rotation angle,thethickness of vacuum,PC board and the substrate plate are studied at the sametime.We find that through reasonable design reasonable parameters can obtain morewider band gap,which provides a reference on designing large band gap phononiccrystals.(2) We use the finite element method studing the band structure of lamb wavesin the local resonance elliptic cylinder phononic crystals.By changing the height ofthe elliptic cylinder,filling rate,the ratio of short axis and long axis,rotation angle,we find that the height of the elliptic cylinder influence on the band gap is thelargest.Filling rate is proportional to the width of the band gap,the ratio of short axisand long axis have small influence on the lower boundary of band gapfrequency,which is also determined by the characteristics of the local resonance.