龍門式起重機(jī)外文翻譯@中英文翻譯@外文文獻(xiàn)翻譯

英文原文： Fatigue life prediction of the metalwork of a travelling gantry crane V.A. Kopnov Abstract Intrinsic fa tigue 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 a t the enterprises of the Russian forest industry. The problem was stated to find the weakest elements lim iting 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 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. 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 remova l of logs from the forest exceeds the processing rate, i.e. there is a creation of a log store, the cra ne expects work, being above the centre of a formed pile with the grab lowe red 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 know n 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 w ood removal should be performed in winter. While in winter the remova l 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 turnove r. 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 sta tistical 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 w ith 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 t o 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, w ith the nominal volume of one pack being 25 m3. Then, know ing 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)=Pn 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. F igure 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 de termine a range of stresses, static st rain measurements were carried out beforehand. Vertical loading was applied by hoisting measured loads, and skew loading was formed with a tractor w inch 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 w ith 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 ske w 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 w ith 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 perm itted； 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 w ith the same hoisting speed. Usua lly, 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 w ith 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 characte rized 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 w hen lowering coincide w ith braking of the trolley w ith 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. S ince 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 cha racteristic 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 maxim um values when a load is hoisted. A fter that a load is transferred to the necessa ry location and stresses oscillate due to the irregular crane movement on ra ils 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 w ith 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 num ber 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 m inim um 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 lim it theorem is taken advantage of. F irstly, it is known from probability theory that the addition of k independent Poisson variables gives also a random variable with the Poisson distribution w ith parameter k,. On the other hand, the Poisson d istribution can be well approximated by the normal distribution w ith average, and variation ,. Secondly, the central lim it theorem, roughly speaking, states that the distribution of a large number of terms, independent of the initial distribution asymptotically tends to normal. If the initia l 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 prelim inary 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 calcula tion methods 3, kf=2.r2.9, coinciding w ith 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 ra ther large local stresses caused by local bending also prom ote 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 1s=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 w ith 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 5and 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 F ig. 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. Howeve r, 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 tha t some elements of the metalw ork a re subjectedto large dynamic loads, which causes fatigue damage accumulation followed by fatigue failures.The procedure of fatigue hfe predic tion 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. 中文翻譯 龍門式起重機(jī)金屬材料的疲勞強(qiáng)度預(yù)測 v.a.科普諾夫 摘要 內(nèi)在的疲勞曲線應(yīng)用到 龍門式起重機(jī)金屬材料的 疲勞壽命預(yù)測問題。起重機(jī)，用于在森林工業(yè)中，在伐木林場對各種不同的工作條件進(jìn)行研究，并且做出相應(yīng)的應(yīng)變測量。對載重的循環(huán)周期進(jìn)行計(jì)算，下雨循環(huán)計(jì)數(shù)技術(shù)得到了使用。在一年內(nèi)這些起重機(jī)運(yùn)作的樣本被觀察為了得到運(yùn)作周期的 平均數(shù)。疲勞失效分析表明，一些元件的故障是自然的系統(tǒng)因素，并且不能被一些隨意的原因所解釋。1999 年 Elsevier 公司科學(xué)有限公司。保留所有權(quán)利。 關(guān)鍵詞：起重機(jī) ；疲勞評估 ；應(yīng)變測量 1.緒論 頻繁觀測 龍門式起重機(jī) LT62B 在運(yùn)作時金屬元件 疲勞失效。引起疲勞裂紋的故障沿著起重機(jī)的橋梁焊接接頭進(jìn)行傳播，并且能夠支撐三到四年。這種起重機(jī)在森林工業(yè)的伐木林場被廣泛使用，用來轉(zhuǎn)移完整長度的原木和鋸木到鐵路的火車上，有一次裝載 30 噸貨物的能力。 這種類型的起重機(jī)大約 1000 臺以上工作在俄羅斯森林工業(yè)的企業(yè)中。限 制起重機(jī)壽命的問題即最弱的要素被正式找到之后，預(yù)測其疲勞強(qiáng)度，并給制造商建議，以提高起重機(jī)的壽命。 2.起重機(jī)運(yùn)行分析 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(jī) LT62B， 這臺起重機(jī)能夠供應(yīng)兩個伐木廠建立存儲倉庫，并且能轉(zhuǎn)運(yùn)木頭到鐵路的火車上，這條鐵路通過存儲倉庫。這些設(shè)備的安裝就是為了這個轉(zhuǎn)貨地點(diǎn)在起重機(jī)的跨度范圍之內(nèi)。一個起重機(jī)示意圖顯示在圖 1 中 。 1350-6307/99 /元，看到前面的問題。 1999 年 Elsevier 公司科學(xué)有限公司保 留所有權(quán)利。 PH:S1350-6307(98)00041-7 V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 圖 1 起重機(jī)簡圖 檢查起重機(jī)的工作之后，一系列的假設(shè)可能會作出： 如果每月從森林移動的原木超過加工率，即是有一個原木存儲的倉庫，這個起重機(jī)期待的工作，也只是在原木加工的實(shí)際堆數(shù)在所供給原木數(shù)量的中心線以下； 當(dāng)處理超過原木從森林運(yùn)出的速度時，起重機(jī)的工作需要在的大量的木材之上進(jìn)行操作，相當(dāng)于在大量的木材上這個鋸木廠賺取的很少； 原木不同的倉庫 ；大量的木材的高度被認(rèn) 為是最高的 ； 倉庫的變化，取替了一側(cè)對面的鋸軋機(jī) ； 裝載進(jìn)程中總量是平均為 K=1.4 倍大于移動總量由于額外的轉(zhuǎn)移。 2.1 搬運(yùn)強(qiáng)度 據(jù)了解，每年的搬運(yùn)強(qiáng)度是不規(guī)律的，不能被視為一個平穩(wěn)過程。非平穩(wěn)流動的道路列車的性質(zhì)在 23 家企業(yè)中已經(jīng)研究 5 年的時間，結(jié)果已經(jīng)表明在年復(fù)一年中，對于每個企業(yè)來說，每個月的搬運(yùn)強(qiáng)度都是不同的。這是解釋復(fù)雜的各種系統(tǒng)和隨機(jī)效應(yīng)，對搬運(yùn)施加的影響：天氣條件，道路條件和貨車車隊(duì)等，所有木材被運(yùn)送到存儲倉庫的木材，在一年內(nèi)應(yīng)該被處理。 因此，在春季和秋季搬運(yùn)木頭的可能性越來 越小，冬天搬運(yùn)的可能性越來越大，然而在冬天搬運(yùn)強(qiáng)度強(qiáng)于預(yù)想的，在夏天的情況下，更多足夠長的木材就地被處理的比運(yùn)出去的要多的多。 V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 表 1 搬運(yùn)強(qiáng)度（ %） 表 2 轉(zhuǎn)移儲存量 通過一年的觀察，從 118 各搬運(yùn)值的觀察所了解到的數(shù)據(jù)進(jìn)行分析，并且有可能評價(jià)相關(guān)的搬運(yùn)強(qiáng)度（噸）參考年度的裝載量的百分比。該搬運(yùn)的數(shù)據(jù)被記錄在起重機(jī)預(yù)期值表 1 中，它可以被應(yīng)用到估計(jì)疲勞壽命，尤其是為檢查起重機(jī)應(yīng)變測量（見稍后） 。將有可能為每個起重機(jī)，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(jì)調(diào)查。此外，為了解決這個問題的壽命預(yù)測的知識是未來的荷載要求， 在類似的操作條件下，我們采取起重機(jī)預(yù)期值。 每月搬運(yùn)價(jià)值的分布 Q（ t） ，被相對強(qiáng)度 q（ t）表示為 其中 Q是每年的裝載量的記錄存儲，是設(shè)計(jì)的最大存儲原木值 Q 以百分比計(jì)算，其中為考察起重機(jī)等于40.0 萬立方米每年， 和容積載重搬運(yùn)為 10 的起重機(jī)，得到的數(shù)據(jù)列在表 2 中，總量 56000立方米每年，用 K 表示。 2.2 .裝載木塊的數(shù)量 這個運(yùn)行裝置，如夾緊，吊裝，轉(zhuǎn)移，降低，和釋放負(fù)載可被視為起重 機(jī)的一個運(yùn)行周期（加載塊）。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 11.5 分相等等，標(biāo)準(zhǔn)差為 1.5 分鐘。不幸的是，這個特點(diǎn)不能簡單地用于定義運(yùn)作周期的數(shù)目，任何工作期間的載重加工是非常不規(guī)則。使用運(yùn)行時間的起重機(jī)和評價(jià)周期時間，與實(shí)際增加一個數(shù)量的周期比，很容易得出比較大的誤差，因此，最好是作為如下。 測量一個單位的載荷，可以作為范本，由一個隨機(jī)變量代入分布函數(shù)得出 ，并且比實(shí)際一包貨物少 然 后，明知總量的加工負(fù)荷為 1 個月或一年 可能確定分布參數(shù)的數(shù)目，運(yùn)作周期為這些時期 要利用這個方法的更 新理論 V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 圖 2隨機(jī) 重建過程中的負(fù)荷 根據(jù)這些方法，隨機(jī)重建過程中所顯示的圖。二是考慮到， （隨機(jī)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(jī)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。過程的載荷值，作為下一次的動作的通過值，被看作是重建的時刻。 設(shè) ()nnF t P t。函數(shù) f （ t ）反復(fù)被定義， 假設(shè) V （ t ）是在運(yùn)作周期內(nèi)轉(zhuǎn)移貨物的數(shù)量。實(shí)踐中，總 轉(zhuǎn)移貨物的總噸數(shù)，基本上是大于機(jī)組負(fù)荷，由于利用漸近性質(zhì)的重建過程所以式有益的。根據(jù)下面適當(dāng)?shù)南拗浦亟ǘɡ?，需要轉(zhuǎn)移大量噸數(shù)。已正態(tài)分布漸近與均值和方差，確定抽樣數(shù)量的周期 v 而不依賴于整個的形式分布函數(shù)的 ()Ft， （只對不同的格式分配進(jìn)行限制）。 利用表 2 的每個月平均運(yùn)作用方程（ 4 ）表示，賦予正態(tài)分布功能的數(shù)量，負(fù) 載周期與參數(shù) m和 6。在正態(tài)分布表 3 中 。圖 3 顯示的平均人數(shù)周期與 95 的置信區(qū)間某一年的相應(yīng)的值為 12719和 420 個周期。 表 3 運(yùn)作周期的正太分布 3 .應(yīng)變測量 為了顯示大多數(shù)金屬的負(fù)載元素，并且確定一系列的壓力，事前做了靜態(tài)應(yīng)變測量。垂直載荷用來測量懸掛負(fù)載，并且斜交加載由一個牽引力所形成，配備了一臺測力計(jì)。靜態(tài)應(yīng)力值分布在圖 4和 5 中 。同樣地預(yù)計(jì)，梁上的最大的拉應(yīng)力，發(fā)生在底部的桁架上（值為 11-45 MPA ）。頂端的桁架受到最大的壓縮應(yīng)力。 此處的彎曲應(yīng)力所造成的壓力，車輪起重機(jī)，手 推車等被添加到所說的橋梁和負(fù)荷的重量。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 17-75 和 10-20兆帕斯卡），其他要素的梁加載的值 V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 月份 圖 3 95%的置信區(qū)間運(yùn)作周期的平均數(shù) V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 圖 4 梁的分配計(jì)劃 不超過絕對值 45 兆帕斯卡。連接與支持的橋梁起重機(jī)加載的時間，也不定期。最大的壓縮應(yīng)力發(fā)生在變形的最大角度，在內(nèi)部看來 ；最高壓力值將達(dá)到到 h0MPa 和痛苦（計(jì) 8 日和 9 ） 。在隔板和角度 1 的支板上，最大的拉應(yīng)力達(dá)到 45 兆帕斯卡（壓力表 1 ）。 起重機(jī)梁的器件在受到最大壓力和軸向載荷較弱的時候，另一方面，所遭受的主要是斜負(fù)荷。起重機(jī)的豎向載荷主要是由牽引力引起的。 這種轉(zhuǎn)移完整長度的木材的起重機(jī)的金屬的載重量，不同于一般用途的起重機(jī)。首先它必須遵循起重機(jī)的裝載規(guī)則，由于逐步脫離基地。因此，負(fù)荷增加，并不是慢慢的順利進(jìn)行。 第二個特點(diǎn)是物質(zhì)吊裝的加快導(dǎo)致低低效率。這是抓斗所存在的所限制，這意味著不允許繩索從吊具座下降 ；載重量應(yīng)始終保持平衡。負(fù)載減弱加快 電機(jī)運(yùn)轉(zhuǎn)的可能性是沒有根據(jù)的，因此微乎其微。因此，以同時懸掛的速度，森林龍門式起重機(jī)受到較小的動應(yīng)力與類似的一般用途的起重機(jī)相比而言。通常，當(dāng)速度增加順利，在接通電器之后，從基地進(jìn)行轉(zhuǎn)載 3.5-4.5 秒鐘進(jìn)行一個循環(huán)。在事實(shí)上，并沒有發(fā)現(xiàn)金屬有顯著的振蕩，并且壓力慢慢達(dá)到了最大值。 V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 圖 5 支持分配 當(dāng)可能性最明朗的時候，在伸展和抓取的結(jié)合處，在按下開關(guān)后一秒鐘繩索開始繃緊，在結(jié)合處清楚的發(fā)生。這個電動機(jī)以 0.6-0.7 每秒的速度進(jìn)行 旋轉(zhuǎn)。從按下開關(guān)到繩索完全拉緊這一刻，需要 3-3.5 s 的時間，緊張的繩索慢慢的增加倒最長。梁的最大壓力增長倒最大值 1-2 S 并且平均振蕩為 3.5 。 當(dāng)一個固定的負(fù)荷解除時，加快速度，裝載在鋼絲繩上的吊具和金屬幾乎是相同的情況下快速吊起一堆捆扎的木材。該金屬金工振蕩的特點(diǎn)是有兩個諧波在 0.6 和 2 秒的過程當(dāng)中，這些已經(jīng)在前面的分析中獲得。從總結(jié)裝貨的振幅可以看出在最壞的情況下裝載貨物，使最高動態(tài)加載超過上述靜態(tài)載荷可以達(dá)到 13-14 。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(dá)到靜態(tài)載荷的 7%左右。 移動超過鋼軌接頭的 3-4 毫米的高度 時 ， 得到的 只有微不足道的 壓力 。 在 運(yùn)行 中，有可能的情況下，當(dāng)源自不同類型的負(fù)荷加載結(jié)合起來。 當(dāng)最高負(fù)荷從制動負(fù)荷時降低 ， 是最大負(fù)荷情況配合制動手推車與 同 的調(diào)整制動器 。 4 疲勞載荷分析 通過起重機(jī)的工作和壓力示波圖的獲得，在測試點(diǎn)進(jìn)行應(yīng)變測量，在圖 6 和第 5 中排列顯示，自一臺起重機(jī)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(yùn)行周期的時間起重機(jī)有足夠的散射與平均價(jià)值 11.5 ） V.A.Kopnov|機(jī)械故障分析 6（ 1999） 131-141 時間（ 0.1 分鐘）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。 三個特點(diǎn)強(qiáng)調(diào)示意圖 （表 11 ）顯示在 表6 中，而裝貨運(yùn)行周期的內(nèi)部結(jié)構(gòu)是可見的。首先，當(dāng)負(fù)載被提升時，壓力增加到最高值。當(dāng)載荷被轉(zhuǎn)移到合適的位置并且強(qiáng)烈振蕩之后之后，由于不規(guī)則起重機(jī)運(yùn)動對鋼軌及以上的鋼軌接頭導(dǎo)致大量的軸向載荷作為大多數(shù)降低載荷的原 因。減少貨物的裝載量導(dǎo)致裝載量減少，并且建成一項(xiàng)基本負(fù)載周期的一半。 4.1 裝載過程中的振幅分析 這兩個名詞，現(xiàn)在應(yīng)該分開：裝載周期和裝載量。第一是作為一獨(dú)特的振蕩講（閉環(huán)） ，二是為一套加載周期期間一個運(yùn)行周期。 該雨流循環(huán)計(jì)數(shù)方法給出了最終裁決。 2