發(fā)布時間：2018-07-26 13:20

【摘要】：現(xiàn)代高效高精度加工對機床性能要求越來越高,且有競爭力的機床生命周期不斷縮短,傳統(tǒng)的物理原型機制造、測試、修改、優(yōu)化的設計方法逐漸不能滿足現(xiàn)代機床設計需求。運用虛擬機床技術建立機床結構的數(shù)學模型,在設計階段預測機床靜動態(tài)性能,并根據(jù)預測結果修正設計方案,最終達到設計要求是實現(xiàn)高效高水平機床設計的一種新途徑。建立能準確模擬機床結構靜動態(tài)特性的數(shù)學模型是虛擬機床技術的基礎,而機床結合部的建模則是機床結構建模中的難點和關鍵。 本文以數(shù)控機床結合部為研究對象,運用有限單元法、實驗模態(tài)分析法和現(xiàn)代優(yōu)化設計方法,對機床結構動力學建模中的結合部建模、模型參數(shù)獲取、影響因素分析和應用技術四個關鍵技術展開深入研究。主要工作有如下幾點： 第一,提出主軸-刀柄錐面配合固定結合部的帶錐度的有限單元模型及參數(shù)識別方法。該模型用帶錐度的有限單元剛度矩陣和阻尼比系數(shù)來模擬主軸-刀柄錐面配合固定結合部的動態(tài)固有特性。基于結構頻響函數(shù)矩陣與動剛度矩陣互逆關系,利用模態(tài)實驗法測試得到的頻響函數(shù)識別帶錐度的有限單元參數(shù)。通過不同數(shù)學模型計算結果與實驗值的比較,驗證了該有限單元模型能夠準確模擬錐面配合固定結合部的動力學特性。 第二,分析結構材料對機床螺栓固定結合部動力學特性的影響。分別基于Hertz接觸理論和實驗模態(tài)分析法,推導了不同材料配對螺栓固定結合部單元剛度矩陣與螺栓連接部件材料的等效彈性模量之間的統(tǒng)計模型。通過機床常見的螺栓連接部件建模應用,驗證該統(tǒng)計模型的正確性。該正比關系定量的揭示了材料參數(shù)對螺栓固定結合部動力學特性的影響,為螺栓固定結合部單元模型的廣泛應用提供了便利。 第三,基于結合部精確模型的機床結構動力學建模。將螺栓固定結合部和錐面配合固定結合部的有限單元模型集成到有限元軟件中,與結構組件的有限元模型、可動結合部的彈簧單元模型,合成機床整機結構動力學模型。將該方法應用于CKX5680機床、YK31320滾齒機結構和XCM1600機床整機結構動力學建模,模型計算的機床結構靜、動態(tài)特性參數(shù)與實驗值基本一致,說明該建模方法能夠準確建立機床結構動力學模型。 第四,以提高結構的動力學特性為目標,采用優(yōu)化方法確定機床多單元螺栓固定結合部動力學特性影響因素�；诼菟ü潭ńY合部動力學特性影響因素分析,確定優(yōu)化設計變量為螺栓數(shù)目和公稱直徑。通過約束條件分析,確定螺栓數(shù)目和公稱直徑的可行解范圍。根據(jù)許可的頻率損耗因子,在可行解范圍內(nèi),選取最優(yōu)的螺栓數(shù)目和公稱直徑使結構獲得更好的動力學特性。為機床多單元螺栓固定結合部結合面參數(shù)確定提供了一種有效的方法。 最后,以XCM1600機床為例,分析結合部對機床結構柔度分布影響機制。建立該機床結構的內(nèi)力傳遞路徑等效彈簧模型和柔度分布表征。利用所建立的XCM1600機床整機結構有限元模型計算結果,結合機床結構在內(nèi)力傳遞路徑等效彈簧模型,分析機床結合部對整機靜態(tài)柔度影響系數(shù)的影響,結果顯示機床結合部對整機X、Z方向靜態(tài)柔度的貢獻度分別為18.1532%和27.3615%。 本文圍繞機床固定結合部動力學建模及應用展開研究。建立機床錐面配合固定結合部的帶錐度的有限單元模型,確定螺栓固定結合部動力學特性與材料屬性參數(shù)之間的統(tǒng)計模型。在基于剛度影響因子法的螺栓固定結合部動力學模型及與單元尺寸、預緊力及材料屬性參數(shù)之間的定量關系的基礎上,對機床多單元螺栓固定結合部參數(shù)進行優(yōu)化設計�；谒岢龅墓潭ńY合部動力學模型,并綜合可動結合部經(jīng)典彈簧單元模型,提出機床整機結構動力學建模思路,通過機床結構動力學建模示例驗證該建模思路的有效性和正確性。并在此基礎上,分析結合部對機床整機結構靜態(tài)柔度分布的影響機制。
[Abstract]:Modern high efficiency and high precision machining is becoming more and more demanding for machine tool performance, and the life cycle of competitive machine tools is shortened. The traditional design method of physical prototyping, testing, modification and optimization can not meet the needs of modern machine tool design. The mathematical model of machine tool structure is established by using virtual machine tool technology, and the design stage is predicted. The static and dynamic performance of the machine tool is a new way to realize the design of high efficiency and high level machine tool. It is the foundation of the virtual machine tool technology to simulate the static and dynamic characteristics of the machine tool structure accurately, and the modeling of the machine tool junction is the difficult point in the modeling of the machine tool. And the key.
This paper, taking the joint of CNC machine tools as the research object, uses the finite element method, the experimental modal analysis method and the modern optimization design method, studies the combined part modeling, the model parameter acquisition, the influence factor analysis and the application technology of the four key technologies in the machine tool structure dynamics modeling. The main work has the following points:
First, the finite element model and parameter identification method of the spindle taper with the fixed joint are proposed. The model uses the finite element stiffness matrix and the damping ratio coefficient to simulate the dynamic inherent characteristics of the spindle - knife handle conical surface with the fixed joint, and the interaction between the structure frequency response matrix and the dynamic stiffness matrix. The frequency response function tested by the modal experiment method is used to identify the finite element parameters with taper. By comparing the calculated results with the experimental values of different mathematical models, it is proved that the finite element model can accurately simulate the dynamic characteristics of the conical surface with the fixed joint.
Second, the influence of structural material on the dynamic characteristics of the bolt fixed joint is analyzed. Based on the Hertz contact theory and the experimental modal analysis method, the statistical model of the equivalent elastic modulus of the stiffness matrix of the fixed combined part of the bolt and the material of the bolt connecting parts is derived respectively. The correctness of the model is verified by the modeling application of the connected components. The positive ratio relationship reveals the effect of the material parameters on the dynamic characteristics of the fixed joint of the bolt, which provides convenience for the wide application of the model of the bolt fixed joint unit.
Third, based on the dynamic modeling of the machine tool structure with the precise model of the combined part, the finite element model of the bolt fixed joint and the conical surface is integrated into the finite element software, the finite element model of the structural component, the spring element model of the movable part and the dynamic model of the machine tool whole machine. The application of this method is applied. The structure of the CKX5680 machine tool, the YK31320 hobbing machine structure and the whole structure dynamics of the XCM1600 machine tool are modeled. The structure of the machine tool is static, and the dynamic characteristic parameters are basically the same as the experimental values. It shows that the modeling method can establish the dynamic model of the machine tool structure accurately.
Fourth, in order to improve the dynamic characteristics of the structure, the optimization method is used to determine the influence factors of the dynamic characteristics of the fixed joint of the multi unit bolt of the machine tool. The number of bolts and the nominal diameter of the bolt are determined based on the analysis of the influence factors of the dynamic characteristics of the bolt fixed joint. The number of bolts is determined by the constraint condition analysis. According to the permitted frequency loss factor, the optimal number of bolts and nominal diameter can be selected to make the structure better dynamic characteristics in the range of the feasible solution. It provides an effective method for determining the joint surface parameters of the multi unit bolt fixed joint of the machine tool.
Finally, taking the XCM1600 machine tool as an example, the influence mechanism of the joint part on the flexibility distribution of the machine tool structure is analyzed. The equivalent spring model and the flexibility distribution of the internal force transmission path of the machine tool structure are established. The calculation results of the finite element model of the whole machine structure of the XCM1600 machine tool are used, and the equivalent spring model of the internal force transmission path is combined with the structure of the machine bed. The influence of the machine tool combination section on the static flexibility influence coefficient of the machine is analyzed. The results show that the contribution of the machine tool combination to the static flexibility of the whole machine X and Z direction is 18.1532% and 27.3615%., respectively.
In this paper, the dynamic modeling and application of the fixed joint part of the machine tool are studied. The finite element model of the taper with the conical surface of the machine tool is established, and the statistical model between the dynamic characteristics of the bolt fixed joint and the material property parameters is determined. The dynamic model of the bolt fixed joint based on the stiffness influence factor method is established. On the basis of the quantitative relation between the element size, the pretightening force and the material property parameters, the parameters of the fixed joint part of the machine tool multi unit bolt are optimized. Based on the dynamic model of the fixed joint part and the classical spring element model of the movable joint, the dynamic modeling idea of the machine tool machine is put forward. The dynamic modeling of machine tool structure validates the validity and correctness of the modeling idea, and on this basis, the influence mechanism of the joint part on the static flexibility distribution of machine tool structure is analyzed.
【學位授予單位】：華中科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG659

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本文編號：2146136