【摘要】：載荷譜是對零部件進行疲勞試驗的基礎(chǔ)，它的真實性直接影響零部件疲勞壽命預(yù)測的準(zhǔn)確度。目前已有一些領(lǐng)域（如汽車、風(fēng)力發(fā)電、航空航天等）的載荷譜編制方法已經(jīng)發(fā)展的比較成熟，并形成了相應(yīng)的行業(yè)標(biāo)準(zhǔn)和專門的通用處理軟件。工程機械領(lǐng)域的載荷譜編制工作起步晚，其理論計算結(jié)果與試驗測試結(jié)果之間仍存在較大偏差。為研究以裝載機為代表的工程車輛耐久服役性能的室內(nèi)快速評價、理論預(yù)測方法，本文結(jié)合國家自然基金資助項目（基金號：50805065），在借鑒參考國內(nèi)外相關(guān)研究成果的基礎(chǔ)上，對載荷譜編制的關(guān)鍵技術(shù)—分布函數(shù)的選擇與極值載荷的確定方法進行了探討，主要的研究內(nèi)容和結(jié)論分述如下： （1）探索了建立混合分布模型的通用方法。根據(jù)裝載機的循環(huán)作業(yè)特點與每一作業(yè)段的實際載荷分布特性，提出了基于混合分布理論建立最佳分布函數(shù)的方法。建立了多備選方案多目標(biāo)屬性的評估矩陣，通過MTOPSIS優(yōu)化方法求解出不同準(zhǔn)則的權(quán)重系數(shù)，然后利用多準(zhǔn)則決策技術(shù)對多目標(biāo)屬性進行量化處理，并利用優(yōu)化方法確定出混合分布模型中基本函數(shù)的個數(shù)。 （2）建立了極值載荷最佳分布模型，，給出了外推的極值載荷近似表達式�？紤]載荷樣本的隨機性，并結(jié)合統(tǒng)計學(xué)理論，建立了極值載荷的統(tǒng)計學(xué)模型，對比分析了不同類型分布函數(shù)的外推風(fēng)險值（Value at Risk），篩選出最佳的擬合函數(shù)，基于POT理論，在閥值已知的基礎(chǔ)上，利用反推法確定出極值載荷的經(jīng)驗計算公式。 （3）提出了閥值與分布參數(shù)的改進算法。綜述了目前不同領(lǐng)域常用的閥值確定方法理論基礎(chǔ)和應(yīng)用范圍，分析了閥值高低對偏差、方差之間的影響規(guī)律，推導(dǎo)出基于自助采樣法（Bootstrap）求解閥值的過程，針對工程車輛載荷隨機性、不可重復(fù)性與難預(yù)測性等特點，提出利用貝葉斯理論將統(tǒng)計分布函數(shù)的參數(shù)視為隨機變量，以實測數(shù)據(jù)為基礎(chǔ)及時對原參數(shù)進行更新修正，通過對比修正前后的擬合效果，驗證了考慮貝葉斯理論后計算結(jié)果的合理性。 （4）以輪式裝載機變速箱輸出法蘭為例進行極值載荷分布特性分析，并驗證本文提出理論方法的有效性與準(zhǔn)確性。對比分析了三種不同工況下極值分布的離散程度、閥值的差異和極值載荷的大小，并對這種現(xiàn)象產(chǎn)生的原因進行了細致的分析。 本文系統(tǒng)的闡述了工程車輛極值載荷確定方法的基本原理及具體實現(xiàn)過程，為形成系統(tǒng)的工程車輛載荷譜編制理論、制定關(guān)鍵零部件室內(nèi)快速檢測方法和標(biāo)準(zhǔn)提供基礎(chǔ)理論具有重要的學(xué)術(shù)意義與實際應(yīng)用價值。
[Abstract]:Load spectrum is the basis of fatigue test of parts, and its authenticity directly affects the accuracy of fatigue life prediction. At present, there are some fields (such as automobile, wind power, aerospace, etc.) load spectrum compilation method has been developed more mature, and formed the corresponding industry standards and specialized general processing software. The compilation of load spectrum in the field of construction machinery started late, and there is still a big deviation between the theoretical calculation results and the test results. In order to study the indoor rapid evaluation of durable service performance of engineering vehicles represented by loaders, the theoretical prediction method is used in this paper, combined with the project funded by the National Fund for Nature (fund number: 50805065), on the basis of referring to the relevant research results at home and abroad. The selection of distribution function and the method of determining extreme load are discussed in this paper. The main research contents and conclusions are as follows: (1) the general method of establishing mixed distribution model is explored. According to the characteristics of the Loader's cyclic operation and the actual load distribution of each working section, a method of establishing the optimal distribution function based on the mixed distribution theory is proposed. The evaluation matrix of multi-objective attribute is established, and the weight coefficients of different criteria are calculated by MTOPSIS optimization method. Then, the multi-objective attribute is quantified by multi-criteria decision technology. The number of basic functions in the mixed distribution model is determined by the optimization method. (2) the optimal distribution model of extreme load is established, and the approximate expression of extrapolated extreme load is given. Considering the randomness of load sample and combining with statistical theory, the statistical model of extreme load is established, and the extrapolation risk value (Value at Risk), of different distribution function is compared and analyzed. The best fitting function is obtained based on POT theory. On the basis of the known threshold value, the empirical formula of extreme load is determined by using the backstepping method. (3) an improved algorithm of threshold and distribution parameters is proposed. This paper summarizes the theoretical basis and application range of threshold determination methods in different fields, analyzes the influence of threshold values on deviations and variances, and deduces the process of solving threshold values based on self-help sampling method (Bootstrap). In view of the randomness, unrepeatability and unpredictability of the loads of engineering vehicles, the Bayesian theory is used to treat the parameters of the statistical distribution function as random variables, and the original parameters are updated and revised timely on the basis of the measured data. By comparing the fitting results before and after the correction, the rationality of the calculation results after considering Bayesian theory is verified. (4) taking the gearbox output flange of wheel loader as an example, the extreme load distribution characteristics are analyzed, and the validity and accuracy of the theoretical method proposed in this paper are verified. The discreteness degree of extreme value distribution, the difference of threshold value and the magnitude of extreme load under three different working conditions are compared and analyzed, and the causes of this phenomenon are analyzed in detail. In this paper, the basic principle and realization process of the method for determining the extreme load of engineering vehicles are systematically expounded, so as to form the theory of compiling the load spectrum of engineering vehicles. It is of great academic significance and practical application value to establish the basic theory of indoor rapid inspection method and standard for key parts.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TH123

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本文編號：2379421