【摘要】：由于缺少數(shù)控機床使用階段的載荷數(shù)據(jù),造成產(chǎn)品在設(shè)計階段時無法準確的評估出其真實的使用壽命;同時在可靠性試驗階段,由于缺少程序加載譜,造成無法確定與實際工況相符的加載系數(shù)。針對上述問題,本文以數(shù)控機床的關(guān)鍵功能部件數(shù)控刀架為研究對象,開展數(shù)控刀架載荷譜的編制方法及應(yīng)用研究。為了能夠獲取數(shù)控機床真實的載荷工況,需要深入機床用戶現(xiàn)場采集機床工藝數(shù)據(jù),并根據(jù)現(xiàn)場的工藝數(shù)據(jù),開展切削試驗獲取切削載荷。由于數(shù)控機床加工工況復雜,外界干擾源較多等因素,造成切削載荷數(shù)據(jù)統(tǒng)計分析處理困難。針對上述問題,本文主要開展典型工藝參數(shù)的確定、載荷信號的降噪處理、載荷的參數(shù)外推、載荷譜的編制及應(yīng)用等關(guān)鍵技術(shù)的研究,具體研究內(nèi)容如下:1)根據(jù)現(xiàn)場采集的機床工藝數(shù)據(jù),確定了36組典型工藝參數(shù)及對應(yīng)的使用比例;搭建了數(shù)控車床切削力采集裝置,確定了切削采樣頻率和切削試驗步驟;最后開展切削試驗,獲取了典型工藝參數(shù)下的數(shù)控刀架載荷信號。2)根據(jù)數(shù)控車床的加工特點和實測的數(shù)控刀架載荷信號,分析出實驗室采集的載荷信號中存在著大量的噪聲和奇異點,同時存在著噪聲識別困難的問題;針對上述問題,本文提出改進的小波相鄰系數(shù)法,實現(xiàn)了數(shù)控刀架載荷信號的降噪處理。3)根據(jù)數(shù)控刀架的載荷特性,提出基于混合分布的載荷參數(shù)外推模型。利用蒙特卡洛馬爾可夫鏈法將36組載荷信號擴展到指定長度,并通過雨流計數(shù)法合并了36組載荷均幅值頻次矩陣。根據(jù)合并后載荷均幅值的擬合特性,提出采用混合威布爾分布模型擬合載荷均值,威布爾分布模型擬合載荷幅值;針對混合威布爾分布模型中基函數(shù)個數(shù)選擇困難的問題,提出相鄰似然比法選擇最優(yōu)基函數(shù)的個數(shù);在分析載荷均幅值相關(guān)性的基礎(chǔ)上,應(yīng)用Copula函數(shù)建立了載荷均幅值的聯(lián)合分布模型。最后根據(jù)載荷外推累計頻次和聯(lián)合分布模型,編制了切削力矩恒定工況下的數(shù)控刀架載荷譜。4)在分析可靠性試驗基本流程的基礎(chǔ)上,制定了基于載荷譜的數(shù)控刀架可靠性試驗方案;主要包括:可靠性試驗時間的確定、試驗最小樣本數(shù)的求解以及試驗加載方案的確定。最后,結(jié)合研究內(nèi)容,本文還應(yīng)用MATLAB設(shè)計了載荷譜生成器軟件。
[Abstract]:Due to the lack of load data in the use phase of NC machine tools, it is impossible to accurately evaluate the true service life of the products in the design phase. At the same time, in the reliability test stage, due to the lack of program loading spectrum, it is impossible to determine the loading coefficient which is consistent with the actual working conditions. Aiming at the above problems, this paper takes the CNC tool holder as the research object, and develops the method and application of the load spectrum of the NC tool holder. In order to obtain the real load condition of the NC machine tool, it is necessary to collect the machine tool process data from the machine tool users and carry out cutting tests to obtain the cutting load according to the field process data. Because of complex working conditions and many external interference sources, it is difficult to analyze and process the cutting load data. In order to solve the above problems, this paper mainly studies the key technologies, such as the determination of typical process parameters, the noise reduction of load signals, the extrapolation of load parameters, the compilation and application of load spectrum, etc. The specific research contents are as follows: 1) according to the machine tool process data collected on the spot, 36 groups of typical process parameters and corresponding usage ratio are determined; The cutting force acquisition device of NC lathe is built, and the cutting sampling frequency and cutting test steps are determined. Finally, the cutting test is carried out, and the load signal of NC tool holder under typical technological parameters is obtained. 2) according to the machining characteristics of NC lathe and the measured load signal of NC tool holder, It is found that there are a lot of noises and singularities in the load signals collected in the laboratory, and at the same time, the problem of noise identification is also found. In order to solve the above problems, an improved wavelet adjacent coefficient method is proposed to reduce the noise of the NC tool holder load signal. 3) according to the load characteristics of the NC tool holder, a load parameter extrapolation model based on mixed distribution is proposed. By using Monte Carlo Markov chain method, 36 sets of load signals are extended to a specified length, and 36 sets of load average amplitude frequency matrices are combined by rain flow counting method. According to the fitting characteristic of the average amplitude of combined load, a hybrid Weibull distribution model is proposed to fit the load mean value and Weibull distribution model to fit the load amplitude value. In view of the difficulty of selecting the number of basis functions in the mixed Weibull distribution model, the adjacent likelihood ratio method is proposed to select the number of optimal basis functions. Based on the analysis of the correlation between the average amplitude of the load and the Copula function, the joint distribution model of the average amplitude of the load is established. Finally, according to the cumulative frequency and joint distribution model of load extrapolation, the load spectrum of NC tool holder under constant cutting moment is compiled. 4) based on the analysis of the basic flow of reliability test, The reliability test scheme of NC tool holder based on load spectrum is established. It mainly includes the determination of the reliability test time, the solution of the minimum sample number and the determination of the test loading scheme. Finally, combined with the research content, the software of load spectrum generator is designed by using MATLAB.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG659

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