外文翻译--矿井提升机绳索的失效分析

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 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 failure 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 suggests that the dives are responsible for the premature retirement of the hoist rope. Published by Elsevier Science Ltd. 1. INTRODUCTION Wire 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 of 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 wire 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 rope 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 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, and, 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 unbroken wires in the bad segment? 2. BACKGROUND Wire 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 wrapped 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 and the strand within the Fig. 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 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 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 strand 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 strands 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 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 stresses 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 as 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 trellis 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 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 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 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 strands 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 would 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 king 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. 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 segment. 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 chemistry 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 alloying 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 the outside wires, there is no reason to expect that they are from the Fig. 3. (a) Abrasive wear is commonly seen as the principal mode of damage in wires that are exp osed to external surfaces. (b) Fretting results from the relative motion between wires, such as is seen at nicks. Fracture craters due 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 nickel. 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 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 rope. 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 included 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 of Fig. 4. Schematic of hoisting operation. 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 ropes 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 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 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, crown wear, and nicks between adjacent strands. These samples Fig. 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 clockwise 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 strand 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. EXPERIMENTAL RESULTS AND DISCUSSION 4.1. Rope construction The 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 centimeters, 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 flattening 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. During 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 associated 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 elsewhere, 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 becomes 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 becomes m ore 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.) 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 anomaly 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. (Dimensions are in mm.) 4.2. Chemical analysis Wire 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 produced 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 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) 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 steel 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 differences 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) Layers 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 appears 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 differ 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, 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 significant 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 behavior 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 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 results For the rope segments examined, the number of torsions may reasonably be expected to be lower than those in the API specifications, due to fatigue and wear degradation during service. However,as can be seen from Table 2, the torsions generally met or exceeded the AP! specifications. It should be noted that the API specification evaluates the individual torsions, not the averages, whereas Table 2 lists the averages. When individual torsion results are evaluated, more than 90% of outside wires from layer 1 (both segments) and 50% of the outside wires from layer 4 (bad segment) meet this criteria. Since torsion results are highly dependent on surface imperfections such as crown wear and trellis patterns (wear produced as a result of contact between the outside wires in adjacent strands), lower torsion results for these two wire groups are not unusual. For the rope segments examined, the number of torsions may reasonably be expected to be lower than those in the API specifications, due to fatigue and wear degradation during service. However, as can be seen from Table 2, the torsions generally met or exceeded the AP! specifications. It should be noted that the API specification evaluates the individual torsions, not the averages, whereas Table 2 lists the averages. When individual torsion results are evaluated, more than 90% of outside wires from layer 1 (both segments) and 50% of the outside wires from layer 4 (bad segment) meet this criteria. Since torsion results are highly dependent on surface imperfections such as crown wear and trellis patterns (wear produced as a result of contact between the outside wires in adjacent strands), lower torsion results for these two wire groups are not unusual. (1) The outside wires of a strand experience crown wear and/or trellis contact, a cumulative process that affects the surface quality of the wire and lowers the overall torsions. (2) King wires do not experience crown wear or trellis contact, and no appreciable difference in the torsion values was seen. The torsion test is geared towards testing ductility. The API specifications provide for a minimum ductility to be present in a newly fabricated rope. On the other hand, the Ontario Ministry of Labour recommendations provide guidelines for removing a rope based on a decrease in ductility. The initial ductility is primarily a function of the steel chemistry and the wire drawing process. After a rope is put into service, the ductility will change as a function of fatigue and wear. As can be seen,the ductility is similar to that required for a newly fabricated rope, and far exceeds the Ontario Ministry of Labour guidelines for removal. Therefore, it appears that the ductility of the wires in both the good and the bad segments is sufficient. All the torsion results met or exceeded the API requirements for wires removed from newly fabricated wire rope, even though the wires were removed from a used rope. The number of torsions of wires removed from the good rope segment was significantly greater than for those removed from the bad rope segment, but was limited to the outside wires of a strand. These differences are most likely a result of crown wear and/or trellis patterns. There was virtually no difference in the number of torsions between broken and unbroken wires. Therefore, it is highly unlikely that the wires failed due to poor ductility. 4.4. Tensile results The breaking strengths listed in Table 3 generally do not meet the minimum requirements for wires produced from electric furnace steel. Breaking strength requirements should more accurately be called breaking load requirements because the requirements list the minimum load-carrying ability of a given diameter wire. Minimum breaking loads will depend on the cross-sectional area as well as the material property known as the ultimate tensile strength. When crown wear and trellis patterns are present, the cross-sectional area is reduced. The result is that the wire will generally break at these sites of reduced cross section. However, the API specifications are for wires removed from newly fabricated ropes, presumably with uniform cross sections. It would be reasonable to find lower strengths in wires from a rope removed from service, e.g. a rope with crown wear and trellis contact. This effect is probably responsible for the drop in strength seen in the broken outside wires from layer 1. Dives create high wires (analogous to high strands) which experience more material removal from crown wear and deeper nicks from trellis contact. The differences in breaking load between the king wires in the good and bad segments for the first three layers was found to be highly significant. An effect similar to this has been seen by the Bureau of Mines Pittsburgh Research Center when testing rope segments 6. They have noted that the rope breaking strength may initially increase, and then drop off significantly as the rope approaches the end of its useful life. For ropes, the initial increase in breaking strength is generally attributed to break-in and the flattening of contact sites between wires. Although there is a significant difference between the breaking loads for the wires in the good and bad segments, there is not a significant difference between the breaking loads for the broken and unbroken wires in the bad segment. Although interesting, the increase in strength of the wires does not appear to be related to wire failure. The tensile test is used to evaluate the minimum strength of the wires. Wires that are not of the minimum strength run the risk of being overloaded during normal use, and will also have shorter fatigue lives. Signs of overloading, such as ductile cup-cone failures, were not seen. The average strength of the wires is generally acceptable when compared with the strengths listed for other steelmaking processes. With the exception of results for the broken wires in the outside layer (which appears to be related to a loss of metallic area), there is no significant difference in the broken and unbroken wires in the bad segment. The average breaking strength of the wires removed from both the good and bad segments failed to meet the minimum API specifications for wires made out of electric furnace steel. With a few exceptions, the average breaking strengths exceeded those required for basic oxygen steel. The loss of strength of broken outside wires from layer 1 is attributed to the presence of crown wear and trellis patterns. King wires showed an unexplained increase in strength between the good segment and the bad segment, but there was no significant difference in strength between the broken and unbroken king wires. It seems unlikely that inadequate tensile strength is responsible for the wire breaks. 4.5. Metallography Decarburization was observed on wires from layers 1-3. The full depth of decarburization was approximately 15-20/tm, or a little over 1% of the diameter of the wire. Although decarburization detrimentally affects fatigue, the effect is much smaller in magnitude than that of a surface blemish such as crown wear or trellis contact. The amount measured should not have a noticeable effect on the fatigue life of the rope 7. Two types of cracks were observed in the metallographic samples. The first type of crack was radial, less than 50 pm, and generally emanated from a surface pit. The pits and cracks appear to ollow the incursion of decarburization into the wire. This is not unexpected since the ferrite resulting rom the decarburization will pit preferentially during the pickling process. Since the cracks appear n almost all of the samples from layers 1 3, regardless of location, it is highly unlikely that the adial cracks account for the differences in fracture behavior between the good and bad segments. The second type of crack propagated parallel to the surface of the wire, and was located at both rown wear and nick sites. The size and appearance of this type of crack took a variety of forms.At crown wear scars, various degrees of abrasion were found, many samples having wedge formation nd heavy plastic deformation. Some cracks were seen separating the wedge from the main body of he wire. Smaller cracks often appeared in the middle of the crown wear site, and separated the lip f material left after abrasion from the base metal itself. Unlike the abrasion found at the crown ear sites, the wear mechanism present at the nick sites tended to be sliding wear or fretting. The liding wear produced considerable deformation in the pearlitic structure, while fretting tended to emove material by spalling. In all cases, the cracks appeared roughly parallel to the surface, and ropagation of the cracks produced a metallic flake as opposed to a transverse fatigue crack. These echanisms, which are what would be expected given the nature of the interactions within the rope nd with its environment, are the same as found at crown wear and nick sites in other ropes 2. It is ighly unlikely that these mechanisms contributed to premature removal of the rope. Martensite, a suspected nucleation site for fatigue cracks, was not readily identified. Using a natal etchant, only small, thin areas were identified as martensite. It should be noted that there is some question as to whether the white-etching layer observed in wear of ferrous materials is actually martensite. A thin white layer, less than 15/tm, was observed at some nick and crown wear sites in both segments. At some locations, surface cracks that turned and followed the boundary of the white layer were visible. It is felt that the cracks associated with the white layer led to spalling, and are not responsible for the premature removal of the rope. A wide disparity of inclusions was noticed on initial examination. In relation to each other, these nclusions ranged from minimal in size and number to large in size. Since inclusions can reduce the load-carrying capability of a wire as well as decrease its fatigue performance, the number and size of inclusions was investigated. The Making, Shapin9 and Treatin 9 of Steel mentions a cleanliness rating of 0.1).3 vol % inclusions in the range of 10-50 m in diameter for continuous casting 8. Of 69 transverse samples, only 12 had inclusions that were in that range, and these were typically ! 0-25 #m. In the longitudinal direction, the cleanliness rating ranged from 0.1 vol % to approximately 0.75%. (It should be noted that all inclusions are included in this value, not just those greater than 10/m. In addition, only one field was used, leading to a large statistical error.) These observations suggest that, although large inclusions are present, they are within the range expected in this type of steel. Large inclusions and/or clusters of inclusions were found in both the good and the bad segments, as well as at general wear sites, crown wear, and trellis sites. Therefore, it does not appear that there is a correlation between inclusion content and/or size and rope segment, layer, wire, or wear type. Extensive metallographic analyses were performed on wires removed from the two rope segments.Decarburization was found on all outside wires from the first three layers, but was uniform between the segment in question and the comparison. Two types of cracks were observed in the samples.The first type was a radial crack that appeared in relation to the decarburization, and was observed the length of the wire. The second type of crack occurred at wear sites on both the good and bad segments, and on both the broken and unbroken wires, and was observed to propagate parallel to Failure analysis of a mine hoist rope 37 the wire surface. This type of crack most likely contributed to spalling and material removal at the wear site as opposed to initiating a fatigue crack in and of itself. An extensive search was undertaken to locate the appearance of martensite at wear surfaces. The search revealed small locations that could possibly be martensite, but the depth is much less than has been reported in the literature. All nomalies noticed during the metallographic analysis appeared in both segments without regard to broken or unbroken wires. Therefore, it is highly unlikely that microstructural anomalies were responsible for the wire breaks. 4.6. Fractogaphy A fractographic study of 12 fracture locations including five matching fractures was performed to identify characteristics of: (1) fracture location, and (2) crack initiation. Of the 12 fracture locations, nine were identified as occurring at crown wear sites, two as occurring at trellis sites, and one was too obliterated to determine its location. The relationship of the wire failures to dives was also sought. The movement of wires within a strand creates faint wear patterns between wires that are in contact, allowing the placement of adjacent wires to be identified. Adjacent wires within a strand follow a helical path around the king wire, and, although the wires twist, the patterns around the wires are evenly spaced, and continuous between crown wear patterns. The disruption of these wear patterns was considered as evidence of a dive (a location where two wires switch position in the strand). As such, nine of the fractures were positively identified as being in the location of a dive. Most of the wire fractures had two identifiable crack initiation sites. For the failures occurring at crown wear sites, initiation often occurred at the actual crown wear site, located either at the center or at a corner. There was usually another failure site located opposite the crown wear site at the location of the faint wear patterns. Often this wear pattern was of the wire associated with the dive. For the two failures that occurred at trellis sites, the wear associated with the dives was closely associated with one of the nicks. The amount of deformation present as well as the remaining material was evaluated. Some of the crown wear fractures had one-third to one-half of the wire cross section removed by abrasion Others experienced considerable flattening in addition to the loss of cross-sectional area. The trellis nicks associated with the wire fractures were also (qualitatively) larger than the nicks seen elsewhere on the ropes. Therefore, it is felt that the effect of the wire dives on the wire fractures was twofold. First, the dives disrupted the close-packed structure of the strand, and produced locations where certain wires were high. If the high wires were on the outside of the rope, the result was increased wear and/or compression of the wire. If the high wires were in the interior of the rope, the result was deeper than normal nicks on adjacent strands. Second, the wear characteristics and stress distribution were altered in the presence of a dive. In many cases, this contributed to either primary or secondary crack initiation. In summary, fractography was performed on wire breaks removed from the rope. Of the fractures that were not obliterated, most could be identified as being in the location of a dive by wear patterns. The process by which the wires failed varied. Clearly, some of the wires had excessive crown wear, and failed in relation to a loss of metallic area. Fractures at crown wear sites associated with dives had as much as one-third to one-half of the cross-sectional area removed. The interchange of wires at a dive produced unusual wear patterns with adjacent wires, and these wear patterns often appeared as an initiation site of the fatigue crack. Fractures at trellis sites experienced deeper nicks than were seen elsewhere in the rope. In one case, a large gouge caused by an adjacent wire (larger than that shown in Fig. 7) was identified as initiating the wire break. Although a variety of failure mechanisms were present, the common factor was the proximity of a dive. The dive either accentuated a normally occurring mechanism (crown wear) or was the cause of an unforeseen mechanism (gouging). 5. CONCLUSIONS A series of experiments was designed: (1) to compare the broken wires in the bad segment with the unbroken wires in the bad segment, and (2) to compare the wires in the bad segment with those in the comparison segment. Chemical analyses, tensile tests, torsion tests, metallography, and fracture analysis have all been performed. It was determined that, although six different steelmaking heats were identified, there was no correlation with broken and unbroken wires. A significant difference was found in the torsion between the good and the bad segments (attributed to in-service surface wear), but not between the broken and unbroken wires. The results all met or exceeded the API requirements for wires removed from a new rope, so it is highly unlikely that the wires failed due to poor ductility. The tensile results exceeded those for new wires made from basic oxygen steel. Again, a significant difference between the broken wires and the unbroken wires was not observed, so it seems unlikely that inadequate tensile strength is responsible for the wire breaks. Inclusions, decarburization, cracks and martensite ere all evaluated. All anomalies noticed during the metallographic analysis appeared in both segments without regard to broken or unbroken wires. It is highly doubtful that the metallurgical structure was responsible for the wire breaks. Differences in the chemical analyses, tensile tests, torsion tests, and metallography do not correlate with the presence or absence of broken wires. The construction anomaly called a dive was found to be related to the presence of broken wires. The three strands in the bad segment that had wire breaks were also the three strands that contained dives. One strand in the good segment contained a single dive, but no wire break. Dives produce a larger than normal strand diameter in the local vicinity, which results in unusual and unexpected wear and/or deformation. Fractography of the wire breaks showed the breaks to be associated with gouges, flattening, or severe crown wear, all of which can be attributed to the disruption of the strand structure produced by a dive. It appears that the wear and/or deformation caused by the presence of the dive accounts for the wire breaks. The number and distribution of wire breaks were, in turn, responsible for the rope being retired prematurely. REFERENCES 1. U.S. Code of Federal Regulations. Title 30 Mineral Resources； Chapter l-Mine Safety and Health Administration, epartment of Labor； Subchapter N-Metal and Nonmetallic Mine Safety； Part 56, Subpart R, and Part 57, Subpart R: ubchapter OCoal Mine Safety and Health； Part 75, Subpart O, and Part 77, Subpart O； 1 July 1989. 2. Sehrems, K. K., Do,an, C. P. and Hawk, J. A., Journal o Materials Engineerin 9 and PerJormance, 1995, 4, 136. 3. American Petroleum Institute, Spec!fication/br Wire Rope. APISpec(fication 9A (Spec 9A), 23rd edn. Washington, DC,1984. 4. Djivre, M., Mine ShaJ Ropes: Ontario Destructite Wire Testin,q Program. Ontario Ministry of Labour, Sudbury, Ontario,16 January 1991, p. 5. 5. Dove, A. B., Ferrous Wire. Vol. I: The Manu/tcture fFerrous Wire. The Wire Association International, Guilford, CT,1989. 6. Miscoe, A. J., Private communication, 1990. 7. Mayer, M., Private communication, 1995. 8. Lankford, W. T., Jr., Samways, N. L. Craven, R. F. and McGannon, H. E., eds, The Making, Shaping, and Treating o teel, 10th edn. Association of Iron and Steel Engineers, Pittsburgh, PA, 1985. 中文翻译： 矿井提升机绳索的失效分析 摘要 对提前报废的提升钢丝绳进行广泛的调查。这些绳索比预想的要早报废，但是因为它满足金属丝中断的号码和分配。它的化学性质，强度极限和延展性都较好的满足新绳索的标准。金属组织显示局 部的不规则，但是这些现象在好的和坏的段两者都有出现，在断了和未破损的电线都存在。仅仅有一项仿佛和电线的故障和出现不规则结构有关系。这些不规则结构，术语叫 潜水 ，使绳股的结构分裂，还可能导致过度的压力磨损和罕见的磨耗图纹。绳索中断的地方全部发现在 潜水 附近。这个调查提出这个 潜水 是卷扬绳过早的报废的原因。 1、简介 钢丝绳传递着巨大的轴向负荷和展示极度的揉曲性。另外 ,钢丝绳设计使它当一些电线中断而没有完全损失时经受得起。这些特征使得钢丝绳在许多体系中成为一个万能的元件。钢丝绳被用于许多工业，包 括采 矿，滨外海上石油生产和牵引或荒野的船。奥尔巴尼研究中心已经研究钢丝绳的降解机理，目的是为了更精确地推算绳索的使用年限。在和Henderson Mine 合作下，奥尔巴尼研究中心人员研究使用寿命出乎意料短暂的报废后的提升机绳索。在工作 9 个月以后，这绳索因为它超过容许的每敷管长度断丝的脉码调制数而报废。选中绳索的两部分俩来研究。一部分是在或靠近因为断丝而要求报废的一段（此后被认为是这错误程序段），另一部分是来自包着金属的（此后被认为是好的部分）。分析这两部分在结构，钢的成分加工方法，和机械性能上的差异。因为人 们感到绳索是过早地报废，分析的目的是识别，和如果可能的话定量的说明绳索中断的任何差异。 首先的研究集中在两个明白的问题：（ 1）绳索的好的和坏的部分有什么差异，（ 2）在中断和在坏段里未破损绳索是否存在任何实际的或机械的的差异？ 2、背景 钢丝绳由金属丝绕成一束组成叫做 绳股 ，然后绕成绳索（图 1）。在绳股的在最中心的金属丝为绳子的主要部分，为为缠绕它的金属丝提供支撑。一或多层可能是包在主要金属丝来构成绳股。最后层构成绳股的最外面，从而这金属丝叫做室外线。在一个绳股里数量，大小和钢丝排列方式以及绳股的数目 决定它的结构。绳股里的金属丝和绳索里的绳股是各自向左或者向右螺旋缠绕形成的。钢丝绳术语引用了右向逆捻或左向逆捻的术语。右旋和左旋要看绳索里绳股的螺旋方向，这个结论引用绳股里金属丝的螺旋方向和绳索里绳股的螺旋方向的关系。在逆捻钢 丝绳的上，绳股里的金属丝缠绕方向和绳索里的绳股是相反的，然而同向捻钢丝绳缠绕方向是一样的。钢丝绳绳心可能是绳股，较小绳索 叫做绳式股芯（独立钢丝绳芯） 或者纤维。不旋转钢丝绳（亦称抵制旋转绳索）是一个特殊的绳索，由倍数的钢绞线层组成，钢绞线层减少了正常绳索的旋转。 图 1。金属丝绳索的三个基本组成成分是金属丝，绳股和核心。金属丝是单个、连续的金属棒。绳股是对称排列、成螺旋形缠绕组合的金属丝。核心是金属丝绳索的中心构件。绳索又一个纤维，金属丝绳股或绳式股芯组成。这三部分组合成金属丝绳索。 绳索通常被用于 矿井提升机的工作里因为它有三种联系。（ 1）接触绳索的绳股外面的有一个套件，例如一个滑车轮，金属桶，或金属桶上的绳索层，简而言之经常叫做顶部磨损；（ 2）在单个绳股或绳股之间里面金属丝之间有线接触；（ 3）在单个绳股或绳股之间里面金属丝之间有点接触。金属丝的实际磨损是由应力在绳索拉紧和因为绳索弯曲、装卸的局部运动中接触面积发展而来的组合引起的。顶部磨损表现为绳索在外面的金属丝横截面减少如图 2（）。绳股之间的磨损表现为刻痕，因为是长方形磨损伤痕而显得很明显如图 2（）。一个特殊的图案，由一或多类似的方向和 深度的刻痕组成，各个金属丝绳股之间的接触部位紧接着排着。这些刻痕的特征图由绳股之间点和线接触构成的，被称为 格子结构 或异常刻痕 如图 2（）。由磨擦引起的顶部损耗显示钢丝绳的磨损 如图 3（ a） , 由磨损引起的刻痕 如图 3（ b） , 由于严重的磨损机构存在外表上的差异。 3、实验步骤 两部分绳索大约 10 英尺长度。坏的部分包含许多的断裂和要求报废段的附近。好的部分不包含断裂，并且来自报废的金属绳索 (见图 4)。在工作期间 ,绳索的坏的一段受到来自滑轮和金属桶的环状的弯曲应力，以及来自绳索的和平衡物的重量的变化 张应力。好的一段绳索受到来自绳索的和平衡物的重量的变化张应力。 金属丝分为绳索部分，层（外面绳股 = 1 层核心 = 5 层），绳股和金属丝，如图 5 所示。断丝仅仅发现在坏的绳索部分。在这部分里，全部的断裂包含在外 面两层绳股里面和绳股的第三层。这三绳股也包含被认为是 潜水 的不规则结构。这些被称为 “ 潜水 ” 是因为当一个绳股的可见的生效的 室外线，人们注意到绳索便会隔些时候 潜水变成绳股的内部，就再也不生效了。一不同的金属丝便会从绳股的内部出来，取代消失的室外线的位置。进一步断定，潜水超过轴的位置，绳索的主钢丝阻拦 潜水起室外线作用，室外线阻拦潜水起绳索的主钢丝作用。一个这样的潜水如图 6所示。另外，绳股阻拦好的绳索部分容纳潜水，但是和金属丝断裂没有关联。虽然绳股包含潜水包含金属丝断裂，但金属丝断裂和俯冲也不一致，也不是全部金属丝断裂都发现在潜水的地方。 在潜水期间，主钢丝和室外线在多股电缆芯线里面位置完全地转换。这个带来在线的标签故统计比较的困难。为了标明用途，主钢丝通过绳股到绳索另一端 位置基准认出。然而许多平面图根据同一的金属丝名称上的组计值。为了分析，主钢丝和室外线单独地由直径决定。就是这些分析的结论属于未容纳潜 水的绳股。 图 2。（）在顶部磨损位置的疲劳裂缝。顶部磨损是在和滑车轮，金属桶或其他的外部的元件接 触的绳索的室外线出现。（）在凹痕处的疲劳裂缝。金属丝之间的接触引起凹痕，突出的凹痕是在邻近的多股金属丝成为一绳股的地方发现的。（）邻近的绳股通常有许多金属丝接触，产生一个可识别的凹痕叫做格状图案。凹痕由箭头记号指出。三条凹痕构成一个格状图案。 图 3。（ a）磨损量一般看作是损害暴露于外部的表面金属丝的主要形式。（ b）摩擦腐蚀是由金属丝之间相对运动引起的，例如在凹痕处。分层的出 现导致断面凹坑。一些材料已经从接触面积被挤出。 图 4。提升机运行图解。绳索来自双绞筒提升机的平衡物。这段要求在装配标记 坏的 段取出。比较样品（ 好的 段）来自金属桶的绕线。 图 5。提升钢丝绳结构。绳索的金属丝是一层层的（外面 =1 层，核心 = 5 层）以及绳股位置（ 1 5 =室外线，金属丝 7 =主钢丝）。绳股在各个层按顺时针方向关系标签，选择参考绳股。插图目的是显示两个绳股的金属丝断裂（绳股 2和 13）。 图 6.潜水的外形 .潜水出现在绳股结构的室外线和主钢丝联接位置。白色箭头记号指出位置在室外线移动进绳股的内部去承担主钢丝的功能。 表格 1。坏的绳索段的钢成分：在给定层的从所有的绳股里随机选择金属丝的结果平均数。分别地测定室外线和主钢丝，用重量百分率表示。 表格 2。报废绳索中金属丝的转矩结果： APT 对新制造绳索的金属丝要求。安大略劳工部推荐的用过绳索的 金属丝的要求。 表格 3。报废绳索的金属丝的平均断裂强度：列举了由电炉钢制造成钢丝绳的金属丝的 API 要求的最小值断裂强度的平均数。 研究所有绳索部分的金属丝的化学性质。合金成分的金属丝在力学性能上有巨大的影响，（ 1）合金成分的断裂和未破损的金属丝在坏的部分有重大差别。（ 2）评价全部的合金成分的各个单层。假定好的部分和坏的部分的合金成分一致的：所以，金属丝好的部分的化学分析没有进行。然而，因为主钢丝没有室外线一样的直径，就没有理由认为他们来自于一样的钢熔炼。所以，主金属丝的化 学性质分别地金属丝外面来评价。下列成分可以确定：碳，硫，硅，磷，锰，铬和镍。碳和硫可以由气体分析来确定，硅，锰 ，磷和铬由湿法化学方法来确定。为了获得合金成分的统计学结果，从各个层多重抽样分析。结果见表 1。 扭转试验是按照美国石油组织（ API）对金属丝绳索的规格进行的。表格 2 列举从电炉钢中制造来制造成钢丝绳的金属丝的扭转的最小值（即扭转到破坏得值）。除 API 扭转最小值之外，表格 2 还列举用实验方法确定的好的部分和坏的部分的绳索的扭转的平均值，以及坏的部分的断丝（ ,G O O D B A D B R O K E NX X X）。包括 0.3 GOODX 作为和安大略劳工部实验的比较。安大略劳工部在 他们交付使用以前测试绳索测定最初的参考值作为后来试验周期的捷径。他们建议当扭转数目跌至最初的参考值的30%的时候要警示，以及建议绳索当扭转数目降低到 15%的程度就报废。 拉力的测试是按照钢丝绳的 API 规范进行的。表 3 列出了从中电炉钢制造变成钢丝绳的金属丝的断裂强度平均最小的值。除 API 要求拉力的强度的最小值之外，表格 3 还列举了用实验方法测定的平均断裂强度。包括了好的部分，坏的部分和坏的部分的断丝（ ,G O O D B A D B R O K E NX X X）。 进行金相的和断口金相研究为了确定单一金属丝破坏原因 。因为这金相的研究，各个绳股层的外线和主钢丝包括好的和坏的部分在一般的 磨损，顶部磨损和在邻近的绳股之间的刻痕位置的横向的方向有了测定。这个样品进行了脱碳，裂缝，马氏体，和伤痕磨损测定。另外还测定了金属丝与潜水的联系。 4、试验结果和讨论 4.1、绳索结构 这个不规则结构称为潜水，在绳股结构室外线和主钢丝转换位置。平行绳股轴，两个金属丝便会发生一段几个厘米的互换，于是导致比正常的绳股大的直径（如图 7）。有时罕见的和意外的磨损及畸变便会发生在多股电缆芯线金属丝之间，也见图 7，深的刻痕很容易观察。在其它情况下 ，当顶部磨损的数值增加道接近潜水时，这个结果将成为金属丝表面和顶部过度的磨损广泛的变平（图 8）。除磨损和畸变之外，金属丝的互换尤其是不同的直径便会改变绳股的负荷分配。 在分解期间， 12 潜水是在坏的部分的三不同的绳股中确定。全部的金属丝的断裂是在这三股不同的绳股里发现的（数字 9 10），或经常位于或在潜水之间。比较起来，仅仅一个潜水是在好的部分发现的，这个跟金属丝断裂没有关联。在金属丝绳索设计时，主钢丝的直径一般地比室外线大。总的说来，主金属丝（金属丝 7）的直径大约有 2.95 毫米， 相比来说室外线有 2.82 毫米。在金属丝的研究，据发现连续的主钢丝不能确定 2和 13层如同数字 9 和 10 的图解。这个，除困难展开绳股容纳潜水之外，认为在工作期间不规则没有产生。 图 7。 1 层绳，股 2 的跳水。潜水位置的绳股直径比其它地方大，像两个白色箭头记号显示的一样。圆凿是直径展开的产生的结果如黑色箭头记号显示。 图 8。 1层绳股 13的跳水。总共四条金属丝的断面是明显的，两个是对比断面。主金属丝的联接位置变成室外线，定位标记 潜水 。这些金属丝显示出大量的平化和顶部磨损，仅仅在金属丝断面位置前。两个灰色箭头指出主金属丝磨损的严重差异。在接近潜水的位置，主金属丝的变成更严重。 图 9。坏的绳索部分 1 层绳股 2 的金属丝直径和金属丝断裂位置。金属丝的阴暗部分的直径明显大些。底部插图显示多股聚集的潜水和金属丝断裂的关系。（尺寸为毫米） 4.2 、化学分析 用于美国的钢丝绳没有要求满足合金标准。然而， API 要求金属丝由以下几种方法产生：（ 1）酸的或基本的平炉，（ 2）基本的氧，或（ 3）电炉炼钢；金属丝生产必需满足机械性能的规格，例如断裂强度和扭转的要求，都要取决于炼钢法的使用。断裂强度和扭转的要求很大成分是取决于合金成分， API 合格的结果已经发展成三种不同的炼钢方法。所以，这种炼钢法需要比 API 技术规范更新。 在表格 1 中是代表电炉钢金属丝的化学性质。其余合金元素（锰，铬和镍）和混合物（硫和磷）在电炉钢比敞炉或碱性氧吹钢的较高。一般而言，较多的合金元素会导致延展性降下和强度极限升高。这个反映在 API 技术规范上，电炉钢 图 10。坏的绳索部分 1 层绳股 13 的金属丝直径和金属丝断裂位置。金属丝的阴暗部分的直径明显大些。底部插图显示多股聚集的潜水和金属丝断裂的关系。（尺寸为毫米） 对拉力强度极限有很高的要求和扭转最小的要求。绳索用的钢是在电炉生产的，这是后来被绳索厂商核实了。多变量的化学分析来测定在在不同的层金属丝之间是否存在化学成分的差异。分析显示在第一个三层和包含绳式股芯两个层之间存在化学性质放入显 著差异。结果总结如下： （ 1） 1、 3 层的金属丝有很类似的成分，很可能是从一样的钢的炉次获得。而且 1、 3层室外线是由同一种热处理炉次获得的，而主金属丝是另一种热处理得的。人们注意到 2 层仿佛同 1 、 3 层经过是一样的热处理的，然而不管是主金属丝还是室外线都不包含段的金属丝。 （ 2） 4和 5 层在成分上和起初三层有较大地不同，很可能是从不同的热处理获得的。 （ 3） 4层和 5层彼此存在很大的差别，而且可能不是来自一样的热处理。此外主金属丝出现和室外线不同的热处理。 总计，在绳索中一共有六不同的热处理炉方法。 图 11。 3层绳股 3的坏的绳索段的潜水和断裂 的位置 图 12。比较段 1 层绳股 7 的跳水的位置。这些是发现在比较段的潜水。这些和金属丝断裂没有关联。 与这种炼钢过程 无关，一个主要的问题是钢丝材料它本身是否跟金属丝过早失效有关系。可以看表格 1，在坏的绳索部分的断裂处和未破损处金属丝的化学分析结果很类似的。多元方差分析显示在化学性质之间没有显著差异，可