本文選題：聲子晶體　切入點(diǎn)：磁流變液　出處：《寧波大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：聲子晶體是一種周期性排列結(jié)構(gòu)的復(fù)合材料。當(dāng)彈性波在聲子晶體中傳播時(shí),由于其結(jié)構(gòu)上周期性的排列,存在一定頻率范圍的彈性波將會(huì)被阻礙而不能在其中傳播,這個(gè)不能傳播的彈性波的頻率范圍就叫做聲子晶體的帶隙。一般來說,當(dāng)構(gòu)成聲子晶體的材料和聲子晶體的拓?fù)浣Y(jié)構(gòu)確定了之后,聲子晶體的帶隙也就隨之確定了。面對(duì)目前復(fù)雜的工程應(yīng)用環(huán)境,聲子晶體帶隙的確定性已不能滿足工程實(shí)際需求,所以探究帶隙可調(diào)控的聲子晶體便成了我們需要完成的任務(wù)。磁流變液是一類性質(zhì)可控的智能材料,被認(rèn)為是最具發(fā)展?jié)摿Φ闹悄懿牧现�。�?dāng)沒有外加磁場(chǎng)時(shí),磁流變液以液態(tài)存在,而施加磁場(chǎng)以后,磁流變液迅速變成類固態(tài),且這個(gè)轉(zhuǎn)變是可逆的。這種現(xiàn)象反映在材料參數(shù)上則是磁流變液模量和粘度的改變�；谝陨险撌�,本文提出了一類將磁流變液作為組成材料的聲子晶體。由于磁流變液的模量可以由磁場(chǎng)來調(diào)控,這樣利用磁流變液作為媒介就可以通過磁場(chǎng)來調(diào)節(jié)聲子晶體的帶隙。為了獲得聲子晶體在不同磁場(chǎng)下的帶隙,我們首先用實(shí)驗(yàn)的方法測(cè)得了磁流變液隨磁場(chǎng)變化的剪切儲(chǔ)能模量和耗能模量圖。其次,使用磁流變液構(gòu)造了完美周期聲子晶體模型和帶有缺陷的聲子晶體模型,實(shí)驗(yàn)中使用LMS儀器測(cè)得了其在不同磁通密度下的振動(dòng)傳輸圖譜,同時(shí)運(yùn)用COMSOL仿真軟件對(duì)實(shí)驗(yàn)的聲子晶體加以建模并計(jì)算了帶隙。最后,將實(shí)驗(yàn)得到的帶隙范圍和理論結(jié)果進(jìn)行了對(duì)比,分析了產(chǎn)生誤差的原因,并總結(jié)了磁場(chǎng)改變對(duì)帶隙范圍的影響規(guī)律。主要結(jié)論有:磁流變液的剪切儲(chǔ)能模量和耗能模量隨著磁通密度的增加而逐漸變大,直至磁流變液達(dá)到磁飽和狀態(tài);隨著磁通密度的增大,磁流變液調(diào)控的一維聲子晶體,二維聲子晶體板的帶隙出現(xiàn)了帶隙所在頻率變大,帶隙寬度變寬的現(xiàn)象;以完美周期結(jié)構(gòu)的鋁/水聲子晶體為比較對(duì)象,隨著含有周期缺陷的數(shù)目的增加,以磁流變液作為缺陷的一維聲子晶體梁出現(xiàn)了阻礙聲子晶體中波的傳播的現(xiàn)象;對(duì)于含有三個(gè)周期缺陷的聲子晶體梁,隨著磁通密度的增大,帶隙所在頻率變大,帶隙寬度變寬,這和磁流變液調(diào)控完美周期聲子晶體的帶隙的規(guī)律有較好的一致性。
[Abstract]:The phonon crystal is a kind of composite material with periodic arrangement structure. When elastic wave propagates in phonon crystal, because of its periodic arrangement on the structure, there is an elastic wave in a certain frequency range which will be blocked and can not propagate in it. The frequency range of this nonpropagating elastic wave is called the band gap of the phonon crystal. In general, when the material that constitutes the phonon crystal and the topological structure of the phonon crystal are determined, The band gap of phonon crystal has been determined. Facing the complicated engineering application environment, the certainty of band gap of phonon crystal can no longer meet the practical requirement of engineering. So exploring band-gap, controllable phononic crystals is the task that we need to do. MRF is a kind of smart material with controllable properties, which is considered to be one of the most promising smart materials. When there is no external magnetic field, The magnetorheological fluid exists as a liquid, and after the application of the magnetic field, the magnetorheological fluid becomes a kind of solid state rapidly, and this transition is reversible. This phenomenon is reflected in the change of the modulus and viscosity of the magnetorheological fluid in the material parameters. In this paper, we propose a kind of phononic crystals which use magnetorheological fluid as the composition material. Because the modulus of MRF can be controlled by magnetic field, In this way, the band gap of phonon crystal can be adjusted by magnetic field by using the magnetorheological fluid as the medium. In order to obtain the band gap of phonon crystal under different magnetic fields, The shear energy storage modulus and energy dissipation modulus of the magnetorheological fluid varying with the magnetic field are measured by the experimental method. Secondly, the perfectly periodic phonon crystal model and the phononic crystal model with defects are constructed by using the magnetorheological fluid. In the experiment, LMS instrument was used to measure the vibration transmission atlas at different flux density, and the experimental phonon crystal was modeled and the band gap was calculated by COMSOL simulation software. The band gap range obtained from the experiment is compared with the theoretical results, and the causes of the errors are analyzed. The main conclusions are as follows: the shear energy storage modulus and the energy dissipation modulus of the magnetorheological fluid increase with the increase of magnetic flux density until the magnetorheological fluid reaches the state of magnetic saturation. With the increase of magnetic flux density, the band gap of two-dimensional phonon crystal plate increases with the increase of magnetic flux density. With the increase of the number of periodic defects, the one-dimensional phononic crystal beams with magnetorheological fluid as defects appear to hinder the propagation of waves in phononic crystals, and for the beams with three periodic defects, with the increase of magnetic flux density, The frequency of band gap becomes larger and the width of band gap becomes wider, which is in good agreement with the regulation of band gap of perfect periodic phonon crystal by magnetorheological fluid.
【學(xué)位授予單位】：寧波大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB33;O735

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