英文原文： Fatigue life prediction of the metalwork of a travelling gantry crane V.A. Kopnov P.O. Box 64, Eknteriuburg 620107, Russian Received 3 April 1998; accepted 29 September 1998 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 causes.卯1999 Elsevier Science Ltd. All rights reserved. Key words: Cranes; Fatigue assessment; 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 three-four years. Such cranes are used in the forest industry at log yards for transferring full-length and sawn logs to road trains, having a load-fitting 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 cranes' fives, predict their fatigue behavior, and give recommendations 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 store. 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. 1350-6307/99/$一see front matter 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 3 5 0一6307(98) 00041一7 A series of assumptions may be made after examining the work of cranes: ·if the monthly removal of logs from the forest exceeds the processing rate, i.e. there is a creation of a log store, the crane expects work, being above the centre of a formed pile with the grab lowered on the pile stack; ·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; ·the store of logs varies; the height of the piles is considered to be a maximum; ·the store variation takes place from the side opposite to the saw mill; ·the total volume of a processed load is on the average k=1.4 times more than the total volume of removal because of additional transfers. 2.1. Removal intensity It is known that the removal intensity for one year is irregular and cannot be considered as a stationary process. The study of the character of non-stationary flow of road trains at 23 enterprises Sverdlesprom for five years has shown that the monthly removal intensity even for one enterprise essentially varies from year to year. This is explained by the complex of various systematic and random effects which exert an influence on removal: weather conditions, conditions of roads and lorry fleet, etc. All wood brought to the log store should, however, be processed within one year. Therefore, the less possibility of removing wood in the season between spring and autumn, the more intensively the wood removal should be performed in winter. While in winter the removal intensity exceeds the processing considerably, in summer, in most cases, the more full-length logs are processed than are taken out. From the analysis of 118 realizations of removal values observed for one year, it is possible to evaluate the relative removal intensity g(t) as percentages of the annual load turnover. The removal data fisted in Table 1 is considered as expected values for any crane, which can be applied to the estimation of fatigue life, and, particularly, for an inspected crane with which strain measurement was carried out (see later). It would be possible for each crane to take advantage of its load turnover per one month, but to establish these data without special statistical investigation is difficult. Besides, to solve the problem of life prediction a knowledge of future loads is required, which we take as expected values on cranes with similar operation conditions. The distribution of removal value Q(t) per month performed by the relative intensity q(t) is written as where Q is the annual load turnover of a log store, A is the maximal designed store of logs in percent of Q. Substituting the value Q, which for the inspected crane equals 400,000 m3 per year, and A=10%, the volumes of loads transferred by the crane are obtained, which are listed in Table 2, with the total volume being 560,000 m3 for one year using K,. 2.2. Number of loading blocks The set of operations such as clamping, hoisting, transferring, lowering, and getting rid of a load can be considered as one operation cycle (loading block) of the crane. As a result to investigations, the operation time of a cycle can be modeled by the normal variable with mean equal to 11.5 min and standard deviation to 1.5 min. unfortunately, this characteristic cannot be simply used for the definition of the number of operation cycles for any work period as the local processing is extremely irregular. Using a total operation time of the crane and evaluations of cycle durations, it is easy to make large errors and increase the number of cycles compared with the real one. Therefore, it is preferred to act as follows. The volume of a unit load can be modeled by a random variable with a distribution function(t) having mean22 m3 and standard deviation 6;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 11-45 MPa). The top chord of the truss is subjected to the largest compression stresses.The 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 compressed than the top one (gauge 17-75 and 10-20 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 compression stresses take place in the carrying angles of the interior panel; the maximum stresses reach h0 MPa (gauges 8 and 9). The largest tension stresses in the diaphragms and angles of the exterior panel reach 45 MPa (causes 1 and hl. The elements of the crane bridge are subjected, in genera maximum stresses and respond weakly to skew loads. The suhand, are subjected mainly to skew loads.1, to vertical loads pports of the crane gmmg rise to on the other The loading of the metalwork of such a crane, transferring full-length logs, differs from that of a crane used for general purposes. At first, it involves the load compliance of log packs because of progressive detachment from the base. Therefore, the loading increases rather slowly and smoothly.The second characteristic property is the low probability of hoisting with picking up. This is conditioned by the presence of the grab, which means that the fall of the rope from the spreader block is not permitted; the load should always be balanced. The possibility of slack being sufficient to accelerate an electric drive to nominal revolutions is therefore minimal. Thus, the forest traveling gantry cranes are subjected to smaller dynamic stresses than in analogous cranes for general purposes with the same hoisting speed. Usually, when acceleration is smooth, the detachment of a load from the base occurs in 3.5-4.5 s after switching on an electric drive. Significant oscillations of the metalwork are not observed in this case, and stresses smoothly reach maximum values. When a high acceleration with the greatest possible clearance in the joint between spreader andgrab takes place, the tension of the ropes happens 1 s after switching the electric drive on, the clearance in the joint taking up. The revolutions of the electric motors reach the nominal value in O.}r0.7 s. The detachment of a load from the base, from the moment of switching electric motors on to the moment of full pull in the ropes takes 3-3.5 s, the tensions in ropes increasing smoothly to maximum. The stresses in the metalwork of the bridge and supports grow up to maximum values in 1-2 s and oscillate about an average within 3.5%. When a rigid load is lifted, the accelerated velocity of loading in the rope hanger and metalwork is practically the same as in case of fast hoisting of a log pack. The metalwork oscillations are characterized by two harmonic processes with periods 0.6 and 2 s, which have been obtained from spectral analysis. The worst case of loading ensues from summation of loading amplitudes so that the maximum excess of dynamic loading above static can be 13-14%.Braking a load, when it is lowered, induces significant oscillation of stress in the metalwork, which can be }r7% of static loading. Moving over rail joints of 3} mm height misalignment induces only insignificant stresses. In operation, there are possible cases when loads originating from various types of loading combine. The greatest load is the case when the maximum loads from braking of a load when lowering coincide with braking of the trolley with poorly adjusted brakes. 4. Fatigue loading analysis Strain measurement at test points, disposed as shown in Figs 4 and 5, was carried out during the work of the crane and a representative number of stress oscillograms was obtained. Since a common operation cycle duration of the crane has a sufficient scatter with average value } 11.5min, to reduce these oscillograms uniformly a filtration was implemented to these signals, and all repeated values, i.e. while the construction was not subjected to dynamic loading and only static loading occurred, were rejected. Three characteristic stress oscillograms (gauge 11) are shown in Fig. 6 where the interior sequence of loading for an operation cycle is visible. At first, stresses increase to maximum values when a load is hoisted. After that a load is transferred to the necessary location and stresses oscillate due to the irregular crane movement on rails and over rail joints resulting mostly in skew loads. The lowering of the load causes the decrease of loading and forms half of a basic loading cycle. 4.1. Analysis of loading process amplitudes Two terms now should be separated: loading cycle and loading block. The first denotes one distinct oscillation of stresses (closed loop), and the second is for the set of loading cycles during an operation cycle. The rain flow cycle counting method given in Ref. [2] was taken advantage of to carry out the fatigue hysteretic loop analysis for the three weakest elements: (1) angle of the bottom chord(gauge 11), (2) I-beam of the top chord (gauge 17), (3) angle of the support (gauge 8). Statistical evaluation of sample cycle amplitudes by means of the Waybill distribution for these elements has given estimated parameters fisted in Table 4. It should be noted that the histograms of cycle amplitude with nonzero averages were reduced afterwards to equivalent histograms with zero averages. 4.2. Numbers of loading cycles During the rain flow cycle counting procedure, the calculation of number of loading cycles for the loading block was also carried out. While processing the oscillograms of one type, a sample number of loading cycles for one block is obtained consisting of integers with minimum and maximum observed values: 24 and 46. The random number of loading cycles vibe can be described by the Poisson distribution with parameter =34. Average numbers of loading blocks via months were obtained earlier, so it is possible to find the appropriate characteristics not only for loading blocks per month, but also for the total number of loading cycles per month or year if the central limit theorem is taken advantage of. Firstly, it is known from probability theory that the addition of k independent Poisson variables gives also a random variable with the Poisson distribution with parameter k},. On the other hand, the Poisson distribution can be well approximated by the normal distribution with average}, and variation },. Secondly, the central limit theorem, roughly speaking, states that the distribution of a large number of terms, independent of the initial distribution asymptotically tends to normal. If the initial distribution of each independent term has a normal distribution, then the average and standard deviation of the total number of loading cycles for one year are equal to 423,096 and 650 accordingly. The values of k are taken as constant averages from Table 3. 5. Stress concentration factors and element endurance The elements of the crane are jointed by semi-automatic gas welding without preliminary edge preparation and consequent machining. For the inspected elements 1 and 3 having circumferential and edge welds of angles with gusset plates, the effective stress concentration factor for fatigue is given by calculation methods [3], kf=2.}r2.9, coinciding with estimates given in the current Russian norm for fatigue of welded elements [4], kf=2.9. The elements of the crane metalwork are made of alloyed steel 09G2S having an endurance limit of 120 MPa and a yield strength of 350 MPa. Then the average values of the endurance limits of the inspected elements 1 and 3 are ES一l=41 MPa. The variation coefficient is taken as 0.1, and the corresponding standard deviation is 6S-、一4.1 MPa. The inspected element 2 is an I-beam pierced by holes for attaching rails to the top flange. The rather large local stresses caused by local bending also promote fatigue damage accumulation. According to tables from [4], the effective stress concentration factor is accepted as kf=1.8, which gives an average value of the endurance limit as ES一l=h7 Map. Using the same variation coiffing dent th e stand arid d emit ion is s1=6.7 MPa. An average S-N curve, recommended in [4], has the form: with the inflexion point No=5·106 and the slope m=4.5 for elements 1 and 3 and m=5.5 for element 2. The possible values of the element endurance limits presented above overlap the ranges of load amplitude with nonzero probability, which means that these elements are subjected to fatigue damage accumulation. Then it is possible to conclude that fatigue calculations for the elements are necessary as well as fatigue fife prediction. 6. Life prediction The study has that some elements of the metalwork are subject to fatigue damage accumulation.To predict fives we shall take advantage of intrinsic fatigue curves, which are detailed in [5]and [6]. Following the theory of intrinsic fatigue curves, we get lognormal life distribution densities for the inspected elements. The fife averages and standard deviations are fisted in Table 5. The lognormal fife distribution densities are shown in Fig. 7. It is seen from this table that the least fife is for element 3. Recollecting that an average number of load blocks for a year is equal to 12,719, it is clear that the average service fife of the crane before fatigue cracks appear in the welded elements is sufficient: the fife is 8.5 years for element 1, 11.5 years for element 2, and h years for element 3. However, the probability of failure of these elements within three-four years is not small and is in the range 0.09-0.22. These probabilities cannot be neglected, and services of design and maintenance should make efforts to extend the fife of the metalwork without permitting crack initiation and propagation. 7. Conclusions The analysis of the crane loading has shown that some elements of the metalwork are subjectedto large dynamic loads, which causes fatigue damage accumulation followed by fatigue failures.The procedure of fatigue hfe prediction proposed in this paper involves tour parts: (1) Analysis of the operation in practice and determination of the loading blocks for some period. (2) Rainflow cycle counting techniques for the calculation of loading cycles for a period of standard operation. (3) Selection of appropriate fatigue data for material. (4) Fatigue fife calculations using the intrinsic fatigue curves approach. The results of this investigation have been confirmed by the cases observed in practice, and the manufacturers have taken a decision about strengthening the fixed elements to extend their fatigue lives. References [1] Feller W. An introduction to probabilistic theory and its applications, vol. 2. 3rd ed. Wiley, 1970. [2] Rychlik I. International Journal of Fatigue 1987;9:119. [3] Piskunov V(i. Finite elements analysis of cranes metalwork. Moscow: Mashinostroyenie, 1991 (in Russian). [4] MU RD 50-694-90. 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;16:1041. [6] Kopnov VA. Theoretical and Applied Fracture Mechanics 1997;26:169. 附录B 中文翻译 龙门式起重机金属材料的疲劳强度预测 v.a.科普诺夫 邮箱64 ，邮编 620107 ，俄 收到1998年4月3日;接受1998年9月29日 摘要 内在的疲劳曲线应用到龙门式起重机金属材料的疲劳寿命预测问题。起重机，用于在森林工业中，在伐木林场对各种不同的工作条件进行研究，并且做出相应的应变测量。对载重的循环周期进行计算，下雨循环计数技术得到了使用。在一年内这些起重机运作的样本被观察为了得到运作周期的平均数。疲劳失效分析表明，一些元件的故障是自然的系统因素，并且不能被一些随意的原因所解释。1999年Elsevier公司科学有限公司。保留所有权利。 关键词：起重机;疲劳评估;应变测量 1.绪论 频繁观测龙门式起重机LT62B在运作时金属元件疲劳失效。引起疲劳裂纹的故障沿着起重机的桥梁焊接接头进行传播，并且能够支撑三到四年。这种起重机在森林工业的伐木林场被广泛使用，用来转移完整长度的原木和锯木到铁路的火车上，有一次装载30吨货物的能力。 这种类型的起重机大约1000台以上工作在俄罗斯森林工业的企业中。限制起重机寿命的问题即最弱的要素被正式找到之后，预测其疲劳强度，并给制造商建议，以提高起重机的寿命。 2.起重机运行分析 为了分析，在叶卡特琳堡地区的林场码头选中了一台被安装在叶卡特琳堡地区的林场码头的龙门式起重机LT62B， 这台起重机能够供应两个伐木厂建立存储仓库，并且能转运木头到铁路的火车上，这条铁路通过存储仓库。这些设备的安装就是为了这个转货地点在起重机的跨度范围之内。一个起重机示意图显示在图1中 。 1350-6307/99 /元，看到前面的问题。 1999年Elsevier公司科学有限公司保留所有权利。 PH:S1350-6307(98)00041-7 V.A.Kopnov|机械故障分析6（1999）131-141 图1起重机简图 检查起重机的工作之后，一系列的假设可能会作出： ·如果每月从森林移动的原木超过加工率，即是有一个原木存储的仓库，这个起重机期待的工作，也只是在原木加工的实际堆数在所供给原木数量的中心线以下； ·当处理超过原木从森林运出的速度时，起重机的工作需要在的大量的木材之上进行操作，相当于在大量的木材上这个锯木厂赚取的很少； ·原木不同的仓库;大量的木材的高度被认为是最高的; ·仓库的变化，取替了一侧对面的锯轧机; ·装载进程中总量是平均为K=1.4倍大于移动总量由于额外的转移。 2.1 搬运强度 据了解，每年的搬运强度是不规律的，不能被视为一个平稳过程。非平稳流动的道路列车的性质在23家企业中已经研究5年的时间，结果已经表明在年复一年中，对于每个企业来说，每个月的搬运强度都是不同的。这是解释复杂的各种系统和随机效应，对搬运施加的影响：天气条件，道路条件和货车车队等，所有木材被运送到存储仓库的木材，在一年内应该被处理。 因此，在春季和秋季搬运木头的可能性越来越小，冬天搬运的可能性越来越大，然而在冬天搬运强度强于预想的，在夏天的情况下，更多足够长的木材就地被处理的比运出去的要多的多。 V.A.Kopnov|机械故障分析6（1999）131-141 表1 搬运强度（%） 表2 转移储存量 通过一年的观察，从118各搬运值的观察所了解到的数据进行分析，并且有可能评价相关的搬运强度（吨）参考年度的装载量的百分比。该搬运的数据被记录在起重机预期值表1中，它可以被应用到估计疲劳寿命，尤其是为检查起重机应变测量（见稍后） 。将有可能为每个起重机，每一个月所负荷的载重量，建立这些数据，无需特别困难的统计调查。此外，为了解决这个问题的寿命预测的知识是未来的荷载要求， 在类似的操作条件下，我们采取起重机预期值。 每月搬运价值的分布Q（t） ，被相对强度q（t）表示为 其中Q是每年的装载量的记录存储，是设计的最大存储原木值Q以百分比计算，其中为考察起重机等于40.0万立方米每年， 和容积载重搬运为10 ％ 的起重机，得到的数据列在表2 中，总量56000立方米每年，用K表示。 2.2 .装载木块的数量 这个运行装置，如夹紧，吊装，转移，降低，和释放负载可被视为起重机的一个运行周期（加载块）。参照这个调查结果，以操作时间为一个周期，作为范本，由正常变量与平均值11.5分相等等，标准差为1.5分钟。不幸的是，这个特点不能简单地用于定义运作周期的数目，任何工作期间的载重加工是非常不规则。使用运行时间的起重机和评价周期时间，，与实际增加一个数量的周期比，很容易得出比较大的误差，因此，最好是作为如下。 测量一个单位的载荷，可以作为范本，由一个随机变量代入分布函数得出且比实际一包货物少，并然后，明知总量的加工负荷为1个月或一年可能确定分布参数的数目，运作周期为这些时期要利用这个方法的更新理论 V.A.Kopnov|机械故障分析6（1999）131-141 图2随机重建过程中的负荷 根据这些方法，随机重建过程中所显示的图。二是考虑到， （随机变量）负荷，形成了一个流动的数据链： 在重建的理论中，随机变量：n，有一个分布函数f（t）的，可以被理解为在失败的连接或者要求收据时的恢复时刻。过程的载荷值，作为下一次的动作的通过值，被看作是重建的时刻。 设Fn(t)Pnt。函数f （ t ）反复被定义， 假设V （ t ）是在运作周期内转移货物的数量。实践中，总 转移货物的总吨数，基本上是大于机组负荷，，由于利用渐近性质的重建过程所以式有益的。根据下面适当的限制重建定理，需要转移大量吨数。已正态分布渐近与均值和方差，确定抽样数量的周期v 而不依赖于整个的形式分布函数的F(t)， （只对不同的格式分配进行限制）。 利用表2的每个月平均运作用方程（ 4 ）表示，赋予正态分布功能的数量，负载周期与参数m和6。在正态分布表3中 。图3显示的平均人数周期与95 ％的置信区间某一年的相应的值为12719和420个周期。 表3 运作周期的正太分布 3 .应变测量 为了显示大多数金属的负载元素，并且确定一系列的压力，事前做了静态应变测量。垂直载荷用来测量悬挂负载，并且斜交加载由一个牵引力所形成，配备了一台测力计。静态应力值分布在图4和5中 。同样地预计，梁上的最大的拉应力，发生在底部的桁架上（值为11-45 MPA ）。顶端的桁架受到最大的压缩应力。 此处的弯曲应力所造成的压力，车轮起重机，手推车等被添加到所说的桥梁和负荷的重量。这些压力的结果，在底部的共振的的I梁那么压缩应力比最高的1 处要大得多（值17-75和10-20兆帕斯卡），其他要素的梁加载的值 V.A.Kopnov|机械故障分析6（1999）131-141 月份 图3 95%的置信区间运作周期的平均数 V.A.Kopnov|机械故障分析6（1999）131-141 图4梁的分配计划 不超过绝对值45兆帕斯卡。连接与支持的桥梁起重机加载的时间，也不定期。最大的压缩应力发生在变形的最大角度，在内部看来;最高压力值将达到到h0MPa和痛苦（计8日和9 ） 。在隔板和角度1的支板上，最大的拉应力达到45兆帕斯卡（压力表1 ）。 起重机梁的器件在受到最大压力和轴向载荷较弱的时候，另一方面，所遭受的主要是斜负荷。起重机的竖向载荷主要是由牵引力引起的。 这种转移完整长度的木材的起重机的金属的载重量，不同于一般用途的起重机。首先它必须遵循起重机的装载规则，由于逐步脱离基地。因此，负荷增加，并不是慢慢的顺利进行。 第二个特点是物质吊装的加快导致低低效率。这是抓斗所存在的所限制，这意味着不允许绳索从吊具座下降;载重量应始终保持平衡。负载减弱加快电机运转的可能性是没有根据的，因此微乎其微。因此，以同时悬挂的速度，森林龙门式起重机受到较小的动应力与类似的一般用途的起重机相比而言。通常，当速度增加顺利，在接通电器之后，从基地进行转载3.5-4.5秒钟进行一个循环。在事实上，并没有发现金属有显著的振荡，并且压力慢慢达到了最大值。 V.A.Kopnov|机械故障分析6（1999）131-141 图5 支持分配 当可能性最明朗的时候，在伸展和抓取的结合处，在按下开关后一秒钟绳索开始绷紧，在结合处清楚的发生。这个电动机以0.6-0.7每秒的速度进行旋转。从按下开关到绳索完全拉紧这一刻，需要3-3.5 s的时间，紧张的绳索慢慢的增加倒最长。梁的最大压力增长倒最大值1-2 S并且平均振荡为3.5 ％ 。 当一个固定的负荷解除时，加快速度，装载在钢丝绳上的吊具和金属几乎是相同的情况下快速吊起一堆捆扎的木材。该金属金工振荡的特点是有两个谐波在0.6和2秒的过程当中，这些已经在前面的分析中获得。从总结装货的振幅可以看出在最坏的情况下装载货物，使最高动态加载超过上述静态载荷可以达到13-14 ％ 。制动一个负荷，当它逐渐降低时，在金属制品上产生显著的振动应力，可以达到静态载荷的7%左右。 移动超过钢轨接头的3-4毫米的高度时，得到的只有微不足道的压力。 在运行中，有可能的情况下，当源自不同类型的负荷加载结合起来。 当最高负荷从制动负荷时降低，是最大负荷情况配合制动手推车与同的调整制动器。 4 疲劳载荷分析 通过起重机的工作和压力示波图的获得，在测试点进行应变测量，在图6 和第5中排列显示，自一台起重机的常见工作周期的时间由足够的散射和平均值约为15分钟，常见的运行周期的时间起重机有足够的散射与平均价值11.5 ） V.A.Kopnov|机械故障分析6（1999）131-141 时间（0.1分钟） 装货过程变化值 民，以减少这些示意图均匀过滤所产生的这些信号，和所有反复的形成的值，也就是说，当结构是不受到动态加载，只有静态加载发生时，将会被拒绝。 三个特点强调示意图 （表11 ）显示在表6中，而装货运行周期的内部结构是可见的。首先，当负载被提升时，压力增加到最高值。当载荷被转移到合适的位置并且强烈振荡之后之后，由于不规则起重机运动对钢轨及以上的钢轨接头导致大量的轴向载荷作为大多数降低载荷的原因。减少货物的装载量导致装载量减少，并且建成一项基本负载周期的一半。 4.1 装载过程中的振幅分析 这两个名词，现在应该分开：装载周期和装载量。第一是作为一独特的振荡讲（闭环） ，二是为一套加载周期期间一个运行周期。 该雨流循环计数方法给出了最终裁决。 [ 2 ]是采取优势，以前面提到的疲劳的强度回线分析，为三个最弱的要素：（1）底部角度的协调（表11），（2）横梁顶端的协调（表17），（3）角度的支持（表8）。用微分的手段统计样本周期振幅的值的分布情况，由此得出估计参数列于于表4 中。应该指出的是，直线图的周期振幅与减少事后的非零平均数相等于直线图为零时的平均数。 V.A.Kopnov|机械故障分析6（1999）131-141 表4 装载振幅的威布尔分布参数 名字 值MPa 底部角度的协调 横梁顶端的协调 角度的支持 4.2 装载周期的数目 23.4 40.4 29.5 布尔分布参数 格式b 5 4 4 在雨流循环计数过程期间，计算有多少负荷周期进行了装载量由多少载重周 期的计算装载座也进行了。而处理这一类示波图，一个整体样本数量的加载周期得到了构成的整数与最低及最高观察值：24和26。随机装货周期数VB可以由泊松分布参数来形容 = 34 。 每个月装货块平均数值很快就获得了，因此它是有可能找到适当的特点，如果采取中央极限周期，不仅为每月装载量，而且也为每月或每年的装载周期。 首先，将它从已知的概率论考虑，除了给出了独立的泊松系数，还给出了一个随机变量与泊松分布的参数K）。在另一方面， 泊松分布可以很好地近似正态分布平均k。其次，中心极限定理，大致来说，有着大量标准的计算，独立的初次分配渐近趋于正常。如果初次分配每个独立的任期有一个正态分布，那么载重周期为一年的平均数和标准偏差总数的都是平等的，大致为423096和650 。通过这些值从表3中取值。 5 应力集中的因素和元件的耐力 要素起重机的各个部件初步是由半自动气体焊接，没有边缘制造设备及相应的加工。为考察要件1和3周和边缘焊缝的角度与节点板，有效应力集中疲劳系数是所给予的计算方法[ 3 ] ，的KF = 2.6-2.9 ，正好等于估计值，鉴于目前在俄罗斯规范疲劳焊接要素[ 4 ] ，的KF = 2.9 。起重机金属制成的材料为合金钢09g2s，此材料有一个持久极限120 MPa和屈服强度350兆帕斯卡。然后在平均值可承受的范围内视察要件1和3ES1= 41兆帕斯卡。变异系数为0.1 ，和相应的标准偏差为s1=4.1兆帕斯卡.观察的基本组成部分2是一个I形穿孔，由孔附加导轨，以顶端法兰。那个相当大的局部应力所造成弯曲的地方也能促进疲劳损伤累积。 根据表[ 4 ] ，有效应力集中系数是接受的KF = 1.8 ， 给出了一个平均的价值，可承受的极限，作为ES1=67的强度创伤。使用相同的变化系数的标准差是s1=6.7强度创伤.平均曲线，建议在表[ 4 ] ，已形式： V.A.Kopnov|机械故障分析6（1999）131-141 表5 对数参数的正太分布 名字 平均（块） 底部角度的协调 横梁顶端的协调 角度的支持 与拐点没有5.106和斜度为4.5为要件1及3斜度为5.5 组成部分2。可能的值的元素耐力极限上述重叠的范围，载荷振幅与非零的概率，这意味着这些元素受到疲劳累积损伤。然后根据上面可能作出结论，认为疲劳计算的要素是必要的，也就是疲劳强度预测. 106.800 143.200 74.620 寿命分布参数 标准(块) 58.200 79.200 32.300 6 寿命预测 该项研究的一些金属材料受到疲劳损伤的累积。内在的疲劳曲线是我们预测生命应采取的优势，其中详见于表[ 5 ]和表[ 6 ].通过以下内在疲劳曲线的理论，我们根据观察到寿命分布密度得到数正态分布的数据。该法所得的平均数和标准偏差分别见表5 。那个数正态分布所得出的分布密度，显示在图7中。这是从这个表中至少强度要件为3 。得出一个平均的数量，载重量1年为12719 ， 很明显，平均方法所得的吊臂前，疲劳裂纹出现在焊接要素是足够的：元件的生命周期8.5年为组成部分1 ，11.5年为要件2 ，和6年为组成部分3 。然而，这些要素失效的概率不小于3-4年和是在范围0.09-0.22 。这些概率不能被忽视，为服务的设计和维修提供帮助，应作出努力，扩大允许裂纹发生并且提高强度。 7 结论 通过分析起重机载重表明，一些金属材料受到较大动态载荷，从而导致疲劳损伤的积累，其次是疲劳失效。 疲劳强度的预测过程，本文提出了涉及四个部分 V.A.Kopnov|机械故障分析6（1999）131-141 运行周期 图7各要素寿命分布的密度曲线 （1）分析的运作，在实践中和决心装载块一段时期。 （2）雨流循环计数技术的计算负荷周期为一期标准 运作。 （3）选择适当材料根据疲劳数据。 （4）使用内在疲劳曲线的方法计算疲劳强度。 调查结果已证实的个案观察 制造商已采取的决定，关于加强固定强度。 以实现延长疲劳强度。 参考 [1] Feller W. An introduction to probabilistic theory and its applications, vol. 2. 3rd ed. Wiley, 1970. [2] Rychlik I. International Journal of Fatigue 1987;9:119. [3] Piskunov V(i. Finite elements analysis of cranes metalwork. Moscow: Mashinostroyenie, 1991 (in Russian). [4] MU RD 50-694-90. 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;16:1041. [6] Kopnov VA. Theoretical and Applied Fracture Mechanics 1997;26:169. 英 文 翻 译 班 级：机设1205 姓 名：金长顺 学 号：311204001909 学 院：机械学院 指导老师：王现辉