發(fā)布時間：2018-08-15 12:22

【摘要】：超細(xì)粉體以其特有的優(yōu)良特性迅速受到世界各國的重視。超細(xì)粉體技術(shù)綜合性高，涉及范圍廣，研究起來比較困難。為了獲得粒度更細(xì)的粉體，世界各國對超細(xì)粉體的研究重點主要集中在超細(xì)粉碎設(shè)備的更新上，使得超細(xì)粉碎理論的發(fā)展滯后于粉碎設(shè)備的發(fā)展，超細(xì)粉碎理論的研究有還待于進(jìn)一步改進(jìn)和完善。 超細(xì)粉體是由大量微小顆粒組成的顆粒群，研究超細(xì)粉碎理論就避免不了研究顆粒的力學(xué)性能。為了研究簡便，本文以單顆粒破碎為理論研究對象，建立粉碎數(shù)學(xué)模型。根據(jù)斷裂力學(xué)以及損傷力學(xué)的基本理論，研究單顆粒在粉碎過程中的應(yīng)力變化、裂紋擴(kuò)展條件以及相應(yīng)的能耗關(guān)系。從微觀方面研究材料內(nèi)部導(dǎo)致晶體破碎的依據(jù)，以及使材料達(dá)到破碎所需要的剪切應(yīng)力臨界值。通過上述研究，為材料的裂紋擴(kuò)展以及粉碎提供了重要的理論依據(jù)。 超聲粉碎主要是依靠超聲波產(chǎn)生的沖擊力作用于粉碎物料，導(dǎo)致材料內(nèi)部產(chǎn)生損傷和裂紋并進(jìn)一步擴(kuò)展，最后達(dá)到粉碎的效果。超聲粉碎系統(tǒng)的優(yōu)劣主要取決于其振動位移的大小，因此變幅桿的設(shè)計就顯得極其重要。本文在進(jìn)行大量理論研究的基礎(chǔ)上，設(shè)計并制造了一個圓柱圓錐復(fù)合型變幅桿，并計算變幅桿的性能參數(shù)。通過ANSYS軟件對該圓柱圓錐復(fù)合型變幅桿進(jìn)行有限元分析，分析其縱向振動位移曲線，得到變幅桿的數(shù)值模擬參數(shù)。通過分析對比，發(fā)現(xiàn)理論推導(dǎo)與有限元分析所得到的數(shù)據(jù)誤差不大，驗證了理論推導(dǎo)與有限元分析的一致性。 在理論研究的基礎(chǔ)上，通過仿真軟件ANSYS/LS-DYNA模擬超聲波沖擊固體顆粒的應(yīng)力-應(yīng)變過程。觀察固體顆粒的應(yīng)力變化，通過仿真模擬驗證利用超聲波進(jìn)行超細(xì)粉碎的可行性。 在理論研究以及仿真模擬的基礎(chǔ)上，進(jìn)行超聲粉碎試驗。通過改變超聲粉碎的工藝條件，驗證超聲粉碎試驗的粉碎效果。得到粉碎粒度與粉碎時間的關(guān)系變化曲線。通過改變粉碎時間、超聲功率、粉碎物料的粒度，，來驗證影響超聲粉碎的工藝條件。對數(shù)據(jù)結(jié)果進(jìn)行分析，確定超聲粉碎最佳的粉碎時間、顆粒大小以及超聲功率。根據(jù)試驗結(jié)果分析，發(fā)現(xiàn)超聲粉碎方式與表面積粉碎模型比較類似，微小顆粒逐漸從大顆粒表面脫落，最終均勻形成超細(xì)粉體。
[Abstract]:Ultrafine powder has been paid more and more attention all over the world because of its unique excellent properties. Ultra-fine powder technology is highly comprehensive, involving a wide range, difficult to study. In order to obtain finer powder, the research focus of the world on ultrafine powder is mainly on the renewal of ultrafine pulverizing equipment, which makes the development of ultra-fine grinding theory lag behind the development of crushing equipment. The research on the theory of ultrafine grinding still needs to be further improved and perfected. Ultrafine powder is a group of particles composed of a large number of tiny particles. The study of ultrafine pulverization theory can not avoid the study of mechanical properties of particles. In order to be simple and convenient, a mathematical model of single particle breakage was established in this paper. According to the basic theory of fracture mechanics and damage mechanics, the stress change, crack propagation condition and energy consumption relation of single particle during comminution are studied. The basis of crystal breakage in the material and the critical value of shear stress for the material to be broken are studied from the microcosmic point of view. The above research provides an important theoretical basis for crack propagation and comminution of materials. Ultrasonic comminution mainly depends on the impact force produced by ultrasonic wave acting on the comminuted material, which leads to the damage and crack inside the material and further expands, and finally achieves the effect of crushing. The merits and demerits of ultrasonic comminution system mainly depend on the magnitude of vibration displacement, so the design of amplitude-varying rod is very important. Based on a large number of theoretical studies, a cylindrical tapered composite horn is designed and fabricated, and its performance parameters are calculated. The finite element analysis of the cylindrical conical composite horn is carried out by ANSYS software, and the longitudinal vibration displacement curve is analyzed, and the numerical simulation parameters of the horn are obtained. Through the analysis and comparison, it is found that the error between the theoretical derivation and the finite element analysis is small, which verifies the consistency between the theoretical derivation and the finite element analysis. On the basis of theoretical research, the stress-strain process of ultrasonic impact on solid particles was simulated by simulation software ANSYS/LS-DYNA. The stress changes of solid particles were observed and the feasibility of ultra-fine grinding with ultrasonic was verified by simulation. On the basis of theoretical research and simulation, ultrasonic crushing test was carried out. By changing the technological conditions of ultrasonic comminution, the grinding effect of ultrasonic comminution test was verified. The curve of the relation between grinding granularity and crushing time was obtained. By changing the grinding time, ultrasonic power and the particle size of the pulverized material, the technological conditions affecting the ultrasonic comminution were verified. The data were analyzed to determine the best crushing time, particle size and ultrasonic power. According to the analysis of the experimental results, it is found that the ultrasonic comminution mode is similar to the surface area comminution model, and the fine particles gradually fall off from the surface of the large particles and form ultrafine powders uniformly.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.3

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