【正文】 ES 一 l=h7 Map. Using the same variation coiffing dent th e stand arid d emit ion is 1s?? = MPa. An average SN curve, remended in [4], has the form: with the inflexion point No=5一 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 panel。 the store of logs varies。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。if the monthly removal of logs from the forest exceeds the processing rate, . there is a creation of a log store, the cra ne expects work, being above the centre of a formed pile with the grab lowered on the pile stack。 Strain gauging 1. Introduction Fatigue failures of elements of the metalwork of traveling gantry cranes LT62B are observed frequently in operation. Failures as fatigue cracks initiate and propagate in welded joints of the crane bridge and supports in threefour 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。 英文原文： Fatigue life prediction of the metalwork of a travelling gantry crane . Kopnov Abstract Intrinsic fatigue curves are applied to a fatigue life prediction problem of the metalwork of a traveling gantry crane. A crane, used in the forest industry, was studied in working conditions at a log yard, an strain measurements were made. For the calculations of the number of loading cycles, the rain flow cycle counting technique is used. The operations of a sample of such cranes were observed for a year for the average number of operation cycles to be obtained. The fatigue failure analysis has shown that failures some elements are systematic in nature and cannot be explained by random Elsevier Science Ltd. All rights reserved. Key words: Cranes。 Fatigue assessment。 lives, predict their fatigue behavior, and give remendations to the manufacturers for enhancing the fives of the cranes. 2. Analysis of the crane operation For the analysis, a traveling gantry crane LT62B installed at log yard in the Yekaterinburg region was chosen. The crane serves two saw mills, creates a log store, and transfers logs to or out of road trains. A road passes along the log sto re. The saw mills are installed so that the reception sites are under the crane span. A schematic view of the crane is shown in Fig. 1. 13506307/99/$一 see front