【摘要】：纖維板生產(chǎn)中,木片在熱磨機(jī)磨片的動載作用下分離成纖維。木片斷裂的形貌特征、定量描述方法和木片斷裂過程中強(qiáng)度薄弱的方向以及能量消耗的影響因素,對熱磨機(jī)纖維分離機(jī)理及其磨片優(yōu)化設(shè)計(jì)研究有著重要的影響作用,是此領(lǐng)域研究的前沿課題之一。本文利用分形理論和斷裂力學(xué)理論,主要研究了木片受剪切、沖擊載荷斷裂解離的形貌特征、力學(xué)性能和分形特征,通過建立動載作用下木片斷裂的分形力學(xué)模型,研究了木片斷裂時(shí)能量消耗的影響因素和規(guī)律。本文以5種有代表性的針闊葉木材為試驗(yàn)材料,通過剪切斷裂試驗(yàn),獲取各樹種試件斷口的圖像和斷裂所需的力；運(yùn)用分形理論對試件的斷裂方向、斷裂表面形態(tài)、力學(xué)特性和分形特征進(jìn)行分析,獲得斷口的分形維數(shù)及其與分形曲線的關(guān)系;計(jì)算分析各樹種試件的抗剪強(qiáng)度,得到其抗剪強(qiáng)度薄弱的方向和條件,探討各樹種試件的抗剪強(qiáng)度與其斷口分形維數(shù)之間的相關(guān)性。通過對試件進(jìn)行沖擊斷裂試驗(yàn),獲取各樹種試件斷口的圖像和斷裂所需的能；運(yùn)用分形理論對試件的斷裂方向、斷裂表面形態(tài)、力學(xué)特性和分形特征進(jìn)行分析,獲得斷口的分形維數(shù)及其與分形曲線的關(guān)系；計(jì)算分析各樹種試件的沖擊韌性,得到其沖擊韌性薄弱的方向,探討各樹種試件的沖擊韌性與其斷口分形維數(shù)之間的相關(guān)性。從熱磨機(jī)磨片各分區(qū)采集試驗(yàn)的纖維樣本,運(yùn)用分形理論建立了木片研磨過程中,各分區(qū)纖維的長度、直徑與纖維距磨盤外邊沿距離的雙對數(shù)線性回歸模型,模型表明,木片研磨分離過程中,纖維長度或直徑的變化具有分形性；通過對各分區(qū)纖維長度和直徑分形維數(shù)的分析,揭示了研磨解離纖維時(shí),磨片各分區(qū)纖維分離活動的特征和磨損趨向。利用分形和斷裂力學(xué)理論建立木片斷裂的分形斷裂模型和動載作用下分形力學(xué)模型;通過對木片斷裂分形斷裂模型和動載作用下分形力學(xué)模型的曲線分析,獲得木片斷裂時(shí)裂紋的初始條件和動載作用下木片斷裂時(shí)對能量消耗的影響及變化規(guī)律,為熱磨機(jī)及磨片的結(jié)構(gòu)和參數(shù)設(shè)計(jì)提供了理論依據(jù)。本文通過對材料斷口分形維數(shù)計(jì)算方法的研究分析,提出了一種利用三維掃描計(jì)算材料斷口分形維數(shù)的新方法,并獲得了授權(quán)發(fā)明專利(ZL201310185200.4)；此方法具有精度高、不受碼尺限制、可重復(fù)測量計(jì)算的特點(diǎn),為分形維數(shù)的計(jì)算尋找到新的途徑。動載作用下木片斷裂形貌特征與分形力學(xué)模型的研究,也為熱磨法纖維分離機(jī)理的深入研究,實(shí)現(xiàn)節(jié)能降耗,提高熱磨纖維質(zhì)量提供理論依據(jù)和應(yīng)用實(shí)踐,具有重要理論意義和實(shí)際應(yīng)用價(jià)值。
[Abstract]:In the production of fiberboard, wood chips are separated into fibers under the action of the dynamic load of the grinder. The morphology characteristics, quantitative description method, the direction of weak strength and the influencing factors of energy consumption in the process of wood chip fracture have important effects on the separation mechanism of fiber and the optimum design of the mill. It is one of the frontier research topics in this field. In this paper, fractal theory and fracture mechanics theory are used to study the morphology, mechanical properties and fractal characteristics of fracture dissociation of wood subjected to shear and impact loading. The influencing factors and rules of energy consumption during the breaking of wood chips were studied. In this paper, five kinds of representative coniferous broadleaved wood were used as experimental materials. Through shear fracture test, the fracture images and the force needed for fracture of each tree species specimen were obtained, and the fracture direction and fracture surface morphology of the specimen were analyzed by fractal theory. The fractal dimension of fracture surface and its relation with fractal curve are obtained by analyzing the mechanical and fractal characteristics, the shear strength of each tree species specimen is calculated and analyzed, and the direction and conditions of weak shear strength are obtained. The correlation between the shear strength and the fractal dimension of the fracture surface of each tree species specimen was studied. Through the impact fracture test on the specimen, the fracture image of the specimen and the energy needed for the fracture are obtained, and the fracture direction, fracture surface morphology, mechanical properties and fractal characteristics of the specimen are analyzed by fractal theory. The fractal dimension of fracture surface and its relation with fractal curve are obtained, the impact toughness of each tree species specimen is calculated and analyzed, the direction of weak impact toughness is obtained, and the correlation between impact toughness and fractal dimension of fracture surface is discussed. Based on the fiber samples collected from each zone of the mill, a double-logarithmic linear regression model of fiber length, diameter and distance from the fiber to the outer edge of the disc is established by using fractal theory. The model shows that the fiber length, diameter and the distance between the fiber and the outer edge of the disc are linear regression models. The change of fiber length or diameter is fractal in the process of lapping and separation of wood pieces, and the fractal dimension of fiber length and diameter in each zone is analyzed to reveal that when lapping and dissociating the fiber, The characteristics and wear tendency of fiber separation activity in different subzones of grinding sheet. The fractal fracture model and the fractal mechanics model under dynamic load are established by using fractal and fracture mechanics theory, and the curve analysis of fractal fracture model and fractal mechanics model under dynamic load is carried out. The influence of the initial condition of the crack and the influence of the dynamic load on the energy consumption are obtained, which provides a theoretical basis for the structure and parameter design of the hot mill and the mill. Based on the research and analysis of the method of calculating the fractal dimension of material fracture, a new method for calculating fractal dimension of fracture surface of material by 3D scanning is proposed in this paper, and the patent of authorized invention (ZL2013101855200.4) is obtained, this method has high precision and is not limited by code size. The characteristics of repeatable measurement and calculation provide a new way for the calculation of fractal dimension. The study on fracture morphology and fractal mechanics model of wood chips under dynamic loading also provides theoretical basis and application practice for further study on separation mechanism of hot milling fibers, energy saving and consumption reduction, and improvement of quality of hot milling fibers. It has important theoretical significance and practical application value.
【學(xué)位授予單位】：東北林業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O346.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前2條

1 任寧;于海鵬;劉一星;董君偉;;木材紋理的分形特征與計(jì)算[J];東北林業(yè)大學(xué)學(xué)報(bào);2007年02期

2 費(fèi)本華;分形理論在木材科學(xué)與工藝學(xué)中的應(yīng)用[J];木材工業(yè);1999年04期

相關(guān)博士學(xué)位論文 前1條

1 關(guān)鑫;基于漆酶介體體系活化木纖維制備木質(zhì)纖維板的研究[D];東北林業(yè)大學(xué);2012年

，

本文編號：2132538