【正文】 r years. Such cranes are used in the forest industry at log yards for transferring fulllength and sawn logs to road trains, having a loadfitting capacity of 32 tons. More than 1000 cranes of this type work at the enterprises of the Russian forest industry. The problem was stated to find the weakest elements limiting the cranes39。when processing exceeds the log removal from the forest, the crane expects work above an operational pile close to the saw mill with the grab lowered on the pile。 一 3 m3, with the nominal volume of one pack being 25 m3. Then, knowing the total volume of a processed load for a month or year, it is possible to determine distribution parameters of the number of operation cycles for these periods to take advantage of the methods of renewal theory [1]. According to these methods, a random renewal process as shown in Fig. 2 is considered, where the random volume of loads forms a flow of renewals: In renewal theory, realizations of random:， having a distribution function F(t), are understood as moments of recovery of failed units or request receipts. The value of a processed load:， after }th operation is adopted here as the renewal moment. Let F(t)=P﹛ n? ＜ t﹜ . The function F(t) is defined recurrently, Let v(t) be the number of operation cycles for a transferred volume t. In practice, the total volume of a transferred load t is essentially greater than a unit load, and it is useful therefore totake advantage of asymptotic properties of the renewal process. As follows from an appropriate limit renewal theorem, the random number of cycles v required to transfer the large volume t has the normal distribution asymptotically with mean and variance. without dependence on the form of the distribution function 月 t) of a unit load (the restriction is imposed only on nonlattice of the distribution). Equation (4) using Table 2 for each averaged operation month,function of number of load cycles with parameters m,. and 6,., which normal distribution in Table 3. Figure 3 shows the average numbers of cycles with 95 % confidence intervals. The values of these parameters for a year are accordingly 12,719 and 420 cycles. 3. Strain measurements In order to reveal the most loaded elements of the metalwork and to determine a range of stresses, static strain measurements were carried out beforehand. Vertical loading was applied by hoisting measured loads, and skew loading was formed with a tractor winch equipped with a dynamometer. The allocation schemes of the bonded strain gauges are shown in Figs 4 and 5. As was expected, the largest tension stresses in the bridge take place in the bottom chord of the truss (gauge 1145 MPa). The top chord of the truss is subjected to the largest pression local bending stresses caused by the pressure of wheels of the crane trolleys are added to the stresses of the bridge and the load weights. These stresses result in the bottom chord of the I 一 beam being less pressed than the top one (gauge 1775 and 1020 MPa). The other elements of the bridge are less loaded with stresses not exceeding the absolute value 45 MPa. The elements connecting the support with the bridge of the crane are loaded also irregularly. The largest pression stresses take place in the carrying angles of the interior pa nel。9:119. [3] Piskunov V(i. Finite elements analysis of cranes metalwork. Moscow: Mashinostroyenie, 1991 (in Russian). [4] MU RD 5069490. Reliability engineering. Probabilistic methods of calculations for fatigue of welded metalworks. Moscow: (iosstandard, 1990 (in Russian). [5] Kopnov VA. Fatigue and Fracture of Engineering Materials and Structures 1993。對載重的循環(huán)周期進行計算，下雨循 環(huán)計數(shù)技術(shù)得到了使用。保留所有權(quán)利。引起疲勞裂紋的故障沿著起重機的橋梁焊接接頭進行傳播，并且能夠支撐三到四年。 為了分析，在葉卡特琳堡地區(qū)的林場碼頭選中了一臺被安裝在葉卡特琳堡地區(qū)的林場碼頭的龍門式起重機 LT62B， 這臺起重機能夠供應(yīng)兩個伐木廠建立存儲倉庫，并且能轉(zhuǎn)運木頭到鐵路的火車上，這條鐵路通過存儲倉庫。 1999年 Elsevier公司科學(xué)有限公司保留所有權(quán)利。原木不同的倉庫 。 這是解釋復(fù)雜的各種系統(tǒng)和隨機效應(yīng)，對搬運施加的影響：天氣條件，道路條件和貨車車隊等，所有木材被運送到存 儲倉庫的木材，在一年內(nèi)應(yīng)該被處理。將有可能為每個起重機，每一個月所負(fù)荷的載重量，建立這些數(shù)據(jù)，無需特別困難的統(tǒng)計調(diào)查。參照這個調(diào)查結(jié)果，以操作時間為一個周期，作為范本，由正常變量與平均值 等，標(biāo)準(zhǔn)差為 。二是考慮到， （隨機變量）負(fù)荷，形成了一個流動的數(shù)據(jù)鏈： 在重建的理論中，隨機變量： n? ，有一個分布函數(shù) f（ t）的，可以被理解為在失敗的連接或者要求收據(jù)時的恢復(fù)時刻。實踐中，總 轉(zhuǎn)移貨物的總噸數(shù)，基本上是大于機組負(fù)荷，由于利用漸近性質(zhì)的重建過程所以式有益的。在正態(tài)分布表 3中 。靜態(tài)應(yīng)力值分布在圖 4和 5中 。這些壓力的結(jié)果，在底部的共振的的 I 梁那么壓縮應(yīng)力比最高的 1 處要大得多 （ 值 1775和 1020兆帕斯卡），其他要素的梁加載的值 |機械故障分析 6（ 1999） 131141 月份 圖 3 95%的置信區(qū)間運作周期的平均數(shù) |機械故障分析 6（ 1999） 131141 圖 4梁的分配計劃 不超過絕對值 45 兆帕斯卡。在隔板和角度 1 的支板上，最大的拉應(yīng)力達到 45 兆帕斯卡（壓力表 1 ）。首先它必須遵循起重機的裝載規(guī)則，由于逐步脫離基地。載重量應(yīng)始終保持平衡。在事實上，并沒有發(fā)現(xiàn)金屬有顯著的振蕩，并且壓力慢慢達到了最大值。梁的最大壓力增長倒最大值 12 S并且平均振蕩為 ％ 。制動一個負(fù)荷，當(dāng)它逐漸降低時，在金屬制品上產(chǎn)生顯著的振動應(yīng)力，可以達到靜態(tài)載荷的 7%左右。 4 疲勞載荷分析 通過起重機的工作和壓力示波圖的獲得，在測試點進行應(yīng)變測量，在圖 6 和第 5 中排列顯示，自一臺起重機的常見工作周期的時間由足夠的散射和平均值約為 15 分鐘，常見的運行周期的時間起重機有足夠的散 射與平均價值 ） |機械故障分析 6（ 1999） 131141 時間（ ）裝貨過程變化值 民，以減少這些示意圖均勻過濾所產(chǎn)生的這些信號，和所有反復(fù)的形成的值，也就是說，當(dāng)結(jié)構(gòu)是不受到動態(tài)加載，只有靜態(tài)加載發(fā)生時，將會被拒絕。減少貨物的裝載量導(dǎo)致裝載量減少，并且建成一項基本負(fù)載周期的一半。 [ 2 ]是采取優(yōu)勢，以前面提到的疲勞的強度回線分析，為三個最弱的要素：（ 1）底部角度的協(xié)調(diào)（表 11），（ 2）橫梁頂端的協(xié)調(diào)（表 17），（ 3）角度的支持（表 8）。而處理這一類示波 圖，一個整體樣本數(shù)量的加載周期 得到了構(gòu)成的整數(shù)與最低及最高觀察值 ： 24和 26。在另一方面， 泊松分布可以很好地近似正態(tài)分布平均 k? 。 5 應(yīng)力集中的因素和元件的耐力 要素起重機的各個部件初步是由半自動氣體焊接，沒有邊緣制造設(shè)備及相應(yīng)的加工。變異系數(shù)為 ，和相應(yīng)的標(biāo)準(zhǔn)偏差為 1s?? = .觀察的基本組成部分 2是一個 I形穿孔，由孔附加導(dǎo)軌，以頂端法蘭?？赡艿闹档脑啬土O限上述重疊的范圍，載荷振幅與非零的概率，這意味著這些元素受到疲勞累積損傷。該法所得的平均數(shù)和標(biāo)準(zhǔn)偏差分別見表 5 。然而，這些要素失效的概率不小于 34年和是在范圍 。 （ 2）雨流循環(huán)計數(shù)技術(shù)的計算負(fù)荷周期為一期標(biāo)準(zhǔn) 運作。 以實現(xiàn)延長疲勞強度。26:169.