外文翻译--矿井提升机绳索的失效分析

《外文翻译--矿井提升机绳索的失效分析》由会员分享，可在线阅读，更多相关《外文翻译--矿井提升机绳索的失效分析（48页珍藏版）》请在装配图网上搜索。

1、外文资料与中文翻译外文资料：FAILURE ANALYSIS OF A MINE HOIST ROPE Astarte-An extensive investigation was carried out to determine the cause of the early retirement of an inservicehoist rope. The rope was retired earlier than expected because it met the criteria for removal based on the number and distribution of

2、wire breaks. Its chemistry, strength and ductility compared favorably to standards for new ropes. Metallography revealed minor anomalies, but these appeared indiscriminately in both the good and the bad segments, and in both broken and unbroken wires. Only one item appeared to be related to the fail

3、ure of wires, and this was the appearance of a construction anomaly. This anomaly, termed a dive, disrupts the construction of the strand, and may cause excessive crown wear or unusual wear patterns.The wire breaks removed from the rope were all found in the vicinity of dives. The investigation sugg

4、ests that the dives are responsible for the premature retirement of the hoist rope. Published by Elsevier Science Ltd.1. INTRODUCTIONWire ropes transmit large axial loads, and exhibit extreme flexibility. In addition, a wire rope is designed so that it can withstand some wire breaks without a loss o

5、f integrity. These characteristics make wire rope a versatile component in many systems. Wire ropes are used in many industries,with applications that include mining, offshore oil production, and towing or mooring of ships. The Albany Research Center has been studying the degradation mechanisms of w

6、ire ropes with the goal of more accurately predicting when the end of the useful life of a rope has been reached. In partnership with Henderson Mine, Albany Research Center personnel investigated a hoist rope that was retired after an unexpectedly short service life.After 9 months of service, the ro

7、pe was retired because it exceeded the allowable number of broken wires per lay length 1. Two rope segments were selected for investigation. One segment was at or near the location that required retirement because of broken wires (hereafter referred to as the bad segment), and the other segment came

8、 from the dead wrap on the drum (hereafter referred to as the good segment). The two segments were analyzed for differences in construction, steel composition and processing, and mechanical properties. Since it was felt that this rope was retired prematurely, the analysis was designed to identify, a

9、nd, if possible, quantify, any differences that might account for the wire breaks. Initial examination focussed on two broad questions: (1) what are the differences between the wires in the good and the bad rope segments, and (2) are there any physical or mechanical differences between broken and un

10、broken wires in the bad segment?2. BACKGROUNDWire ropes are composed of wires wound into bundles called strands, which are then wound into the final rope (Fig. 1). The centermost wire of a strand, known as the king wire, provides support for the wires wrapped around it. One or more layers may be wra

11、pped around the king wire to form the strand. The last layer of wires forms the outside of the strand, and, hence, the wires are called outside wires. The number, size and arrangement of wires in a strand, and the number of strands in a rope, determine its construction. The wires within the strand a

12、nd the strand within theFig. 1. The three basic components of a wire rope are the wire, the strand, and the core. The wire is a single, continuous length of metal that is drawn from a rod. The strand is a symmetrically arranged and helically wound assembly of wires. The core is the central member of

13、 a wire rope, about which the strands are laid. It can be made of a fiber, a wire strand, or an independent wire rope. rope can be wound in either a right or a left helix. Wire rope terminology refers to a right regular lay or left lang lay. The terms right and left refer to the helix of the strand

14、within the rope, while the lay refers to the relationship between the helix of the wires in the strand and the helix of the strand in the rope. A regular lay rope has the wires in the strand wound in the opposite direction to the strands in the rope, whereas a lang lay rope has the wires in the stra

15、nd and the strands in the rope wound in the same direction. The rope core can be either another strand, a smaller rope called the independent wire rope core (IWRC), or a fiber. A non-rotating rope (also known as a rotationresistant rope) is a specialty rope that consists of multiple layers of strand

16、s where different types of lays are alternated to reduce the natural rotation of the rope.The wear that occurs within ropes used in mine hoisting operations usually occurs as the result of one of three types of contact: (1) contact of the outer strands of the rope with an external member, such as a

17、sheave, drum, or layer of rope on the drum, a contact that is often called crown wear; (2) line contact between wires within a single strand or between strands; and (3) point contact between wires within a single strand or between strands. Actual wear of the wires results from the combination of str

18、esses that develop at these contact areas during tensioning of the rope, and during localized movement as the rope is bent, loaded and unloaded. Crown wear appears as a reduced cross section on the outside wires of the rope Fig. 2(a). Wear between strands appears as nicks, which are easily visible a

19、s oblong wear scars Fig. 2(b). A characteristic pattern, consisting of one or more nicks with a similar orientation and depth, forms on each wire at the multiple-wire contact site between strands. This characteristic pattern of nicks created by point and line contacts between strands is known as tre

20、llis or interstrand nicking Fig. 2(c). One evaluation of wear in a wire rope has revealed that crown wear results from abrasion Fig. 3(a), and interstrand nicking results from fretting Fig. 3(b), with differences in appearance due to the severity of the wear mechanism 2.3. EXPERIMENTAL PROCEDURE The

21、 two rope segments were approximately 10 ft in leng.The bad segment contained numerous breaks, and was in the vicinity of the location requiring retirement. The good segment contained no breaks, and came from the dead wrap on the drum (Fig. 4). During service, the bad segment of the rope experienced

22、 cyclic bending stresses from both the head sheave and the drum, as well as varying tensile stress from the weight of the rope and the counterweight. The good segment of the rope experienced some tensile stress from the weight of the rope and the counterweight.All wires were disassembled and labeled

23、 by rope segment, layer (outside strands = layer 1 to core = layer 5), strand, and wire position, as shown in Fig. 5. Broken wires were only found in the bad rope segment. In this segment, all breaks were contained within two outside layer strands, and one strand from the third layer. These three st

24、rands also contained the construction anomaly referred to as a dive. These were named dives because, while visually following outside wires around a strand, it was noticed that a wire would occasionally dive into the interior of the strand,and could no longer be followed visually. A different wire w

25、ould come out of the interior of the strand, and take the position of the outside wire that disappeared. It was later determined that, beyond the axial location of the dive, the king wire from before the dive functioned as an outside wire, and the outside wire from before the dive functioned as a ki

26、ng wire. One such dive is shown in Fig. 6. Additionally, one strand from the good rope segment contained a dive, but no associated wire break. Although only the strands that contained dives contained wire breaks, not all dives had a corresponding wire break, nor were all wire breaks found at a dive.

27、 During a dive, a king wire and an outside wire physically change position within the strand. This presented a difficulty in labeling the wires and performing statistical comparisons. For labeling purposes, king wires were initially identified by strand position referenced to one end of the rope seg

28、ment. However, many of the planned evaluations were based on groupings of nominally identical wires. Therefore, for analyses, both king and outside wires were determined solely by diameter. Implicit in these analyses is that the conclusions pertain to a strand that does not contain dives. The chemis

29、try of all groups of wires in the rope segments were examined. Since the alloying composition of a wire can have a large affect on the mechanical response, (1) the alloying composition of broken and unbroken wires in the bad segment were evaluated for significant differences, and (2)the overall allo

30、ying composition of each individual layer was evaluated. The alloying composition of the good segment was assumed to be identical to that of the bad segment: therefore, chemical analyses of the wires from the good segment were not performed. However, since king wires do not have the same diameter as

31、 the outside wires, there is no reason to expect that they are from theFig. 3. (a) Abrasive wear is commonly seen as the principal mode of damage in wires that are exposed to external surfaces. (b) Fretting results from the relative motion between wires, such as is seen at nicks. Fracture craters du

32、e to delamination are present. Some material has been extruded from the area of contact.same steel heat. Therefore, t,he chemistry of the king wires was evaluated separately from the outside wires. The following elements were determined: carbon, sulfur, silicon, phosphorus, manganese, chromium and n

33、ickel. Carbon and sulfur were determined by gas analysis, and silicon, manganese, phosphorus and chromium by wet chemistry methods. In order to obtain a statistical representation of the alloying composition, multiple samples from each layer were analyzed. The results are reported in Table 1.Torsion

34、 tests were performed according to the American Petroleum Institute (API) Specification for Wire Rope 3. Table 2 lists the requirements for the minimum number of torsions (i.e. the number of twists to failure) to be attained by wires made out of electric furnace steel after fabrication into wire rop

35、e. In addition to the API requirements for minimum torsions, Table 2 also lists the average number of experimentally determined torsions for wires in the good segment and the bad segment, and for broken wires in the bad segment (XGOOD, XBAD, XBROKEN, respectively). A column labeled 0.3J(GOOD is incl

36、uded as a comparison to a practice by the Ontario Ministry of Labour. The Ontario Ministry of Labour tests ropes before they are put into service to determine initial reference values, and subsequently tests periodic cutoffs. They recommend caution when the number ofFig. 4. Schematic of hoisting ope

37、ration. The rope in question came from the counterweight of a double drumhoist. The segment requiring removal was at the location marked bad section. The comparison sample(good segment) came from the dead wraps on the drum.torsions drops to 30% of the initial reference value, and recommend that rope

38、s be retired when the number of torsions drops below 15% 4.Tensile tests were performed according to the API Specification for Wire Rope 3. Table 3 lists the requirements for the average minimum breaking strength to be attained by wires made out of electric furnace steel after fabrication into wire

39、rope. In addition to the API requirements for minimum tensile strength, Table 3 also lists the experimentally determined average breaking strength for wires in the good segment, the bad segment, and broken wires in the bad segment ()?GOOD, XBAD, BROKEN, respectively).Metallographic and fractographic

40、 investigations were carried out in order to identify the cause(s) of failure of individual wires. For the metallographic investigation, one outside and one king wire from each strand layer of both the good and the bad segments were evaluated in the transverse direction at sites of general wear, cro

41、wn wear, and nicks between adjacent strands. These samplesFig. 5. Construction ofretired hoist rope. Wires in the rope were examined as a function oflayer (outside=layer 1, core = layer 5) and strand position (wires 15 = outside wires, wire 7 = king wire). Strands in each layer were labeled in a clo

42、ckwise relationship to strand 1, an arbitrarily chosen reference strand. For illustration purposes, the two strands from layer 1 that contained wire breaks (strands 2 and 13) are shown.Fig. 6. Appearance of a dive. A dive is a location where an outside wire and a king wire switch positions in the st

43、rand structure. White arrows indicate positions where an outside wire moves into the interior of the strand to assume the function of a king wire.were evaluated for decarburization, cracks, martensite, and the appearance of the wear scar. In addition, wires involved with dives were also evaluated.4.

44、 EXPERIMENTAL RESULTS AND DISCUSSION4.1. Rope constructionThe construction anomalies were named dives, and are locations where an outside wire and a king wire switch position in the strand structure. Along the strand axis, the interchange of the two wires will take place over a length of several cen

45、timeters, and results in a larger than normal strand diameter (Fig. 7). Unusual and unexpected wear and/or deformation will take place between the wires within the strand. In some cases, as also shown in Fig. 7, this is observed as deep nicks (gouges). In other cases, the result will be extensive fl

46、attening of the wire surface and/or excessive crown wear (Fig. 8), with the amount of crown wear increasing as the proximity to the dive increases. In addition to the wear and deformation, the interchange of wires, especially of different diameters, will alter the load distribution in the strand. Du

47、ring disassembly, 12 dives were identified in three different strands in the bad segment. All wire breaks were found in these three different strands (Figs 9-11), and were often located at or between dives. In contrast, only one dive was found in the good segment (Fig. 12), and there was no associat

48、ed wire break. In wire rope design, king wires typically have a larger diameter than outside wires. Overall, the king wires (wire 7) had a diameter of approximately 2.95 mm, in comparison with Fig. 7. Dive from layer 1, strand 2. The strand diameter at the location of the dive is larger than elsewhe

49、re, as is shown by the two white arrows. The gouge produced as a result of this expanded diameter is shown by the black arrow.Fig. 8. Dive from layer 1, strand 13. A total of four wire fractures are visible, and two are matching fractures. The location where the king wire switches position and becom

50、es an outside wire is at the location marked dive. This wire shows extensive flattening and crown wear just prior to its fracture location. The two gray arrows point out differences in the severity of the crown wear. As the location of the dive is approached, the crown wear of the surrounding wires

51、becomes more severe. Fig.9. Wire diameters and location of wire breaks for layer 1, strand 2, bad rope segment. The shaded portion of the wire has a significantly larger diameter. The bottom illustration shows the relationship of dives and wire breaks in the assembled strand. (Dimensions are in mm.)

52、2.82 mm for the outside wires. In attempting to group like wires/sizes, it was found that a continuous king wire could not be identified in strands 2 and 13 from layer 1 as illustrated in Figs 9 and 10 . This, in addition to the difficulty unwinding strands containing dives, suggests that the anomal

53、y was not created during service.Fig. 10. Wirc diameters and location of wire breaks for layer 1, strand 13, bad rope segment. The shaded portion of the wire has a significantly larger diameter. The bottom illustration shows the relationship of dives and wire breaks in the assembled strand. (Dimensi

54、ons are in mm.)4.2. Chemical analysisWire ropes used in the United States are not required to meet alloying standards. However, the API does require that the wire be produced from: (1) acid or basic open-hearth, (2) basic oxygen, or (3) electric furnace steelmaking processes; and that the wire so pr

55、oduced meets certain mechanical property specifications, e.g. breaking strength and torsional requirements, dependent upon the steelmaking process used. Breaking strength and torsional requirements are highly dependent on alloying composition, and API-acceptable results have been developed for each

56、of the three different steelmaking processes. Therefore, the type of steelmaking process needs to be determined for later comparisons with API specifications.The chemistries of the wires in Table 1 are typical of an electric furnace steel 5. Residual alloying elements (manganese, chromium and nickel

57、) and impurities (sulfur and phosphorus) are generally higher in electric furnace steel than in open-hearth or basic oxygen steel. In general, higher levels of alloying elements result in lower ductility and higher strength. This is reflected in the API specifications, where the electric furnace ste

58、el has the highest requirement for tensile strength and the lowest for torsion. The steel used in this rope was considered to be produced in an electric furnace. This was later verified by the rope manufacturer.A multivariate analysis of the chemical analysis data was performed to determine if diffe

59、rences in chemical composition exist between the different layers of wires. The analysis revealed that there is a significant difference in the chemistries between the first three layers and the two layers that comprise the independent wire rope core. The results can be summarized as follows:(1) Lay

60、ers 1 3 contain wires with very similar composition, and are probably obtained from the same heat of steel. Furthermore, the outside wires from layers I-3 were obtained from one heat of steel, and the king wires from the same layers were obtained from another heat. It should be noted that layer 2 ap

61、pears to be produced from the same steel heats as layers 1 and 3, yet contains no wire breaks of either king or outside wires.(2) Layers 4 and 5 have significantly different composition from the first three layers, and are probably not obtained from the same heat as layers 1 3.(3) Layers 4 and 5 dif

62、fer significantly from each other, and probably do not come from the same heat. Again, the king wires appear to be from a different heat than the outside wires.In all, it appears that there are six distinct heats of steel represented in this rope.Independent of the type of steelmaking process used,

63、one of the primary questions to be addressed is whether the wire material itself is responsible for premature failure of the wires. As can be seen in Table 1, the chemical analyses of broken and unbroken wires in the bad rope segment are very similar. A multivariate analysis of variance shows no sig

64、nificant difference between the chemistries,with the possible exception of the nickel content of the layer 1 king wires. Although the statistical analysis identifies the nickel content as being significantly different, from a practical standpoint the difference is not great enough to affect the beha

65、vior of the material.It appears that the steel used for this wire rope came from six distinct heats from an electric furnace. All of the broken wires were found in layers 1 and 3, which would comprise only two of six distinct steelmaking heats identified. No significant difference was found between

66、the broken and unbroken wires. It can, therefore, be concluded that it is highly unlikely that the overall chemistry of the wires was responsible for the wire breaks.4.3. Torsion resultsFor the rope segments examined, the number of torsions may reasonably be expected to be lower than those in the API specifications, due to fatigu