Failure Analysis of Failed Wire Rope

Failure of an old rope from a stringing lattice transmission towers occurred in winter while the rope was being removed to make way for a new rope. Fracture took place around mid-span. At that time, ambient temperature was −22 °C. Wire rope was in service for nearly 50 years. We were given the mandate to determine the reasons for the fracture of the wire rope and also to suggest measures to prevent such failures from occurring. The study involved laboratory testing (mechanical and metallographic) of representative wire rope samples. The effect of low temperature (from room temperature to −40 °C) on the tensile behavior of wires and wire rope samples was evaluated. In addition, we designed an instrumented impact test to assess the effect of notches, low temperatures and dynamic loading on the fracture behavior; however, no standards were available for direct comparison. Optical metallography was used to judge the extent of corrosion and the nature of microstructure and the cleanliness of the steel. The fracture morphology of broken tensile and impact specimens was carried out using scanning electron microscopy to establish relations between test parameters and fracture modes. Results indicate that considerations have to be given to the occurrence of corrosion, notches, low temperatures, and dynamic loading conditions when replacing wire ropes and this may necessitate the replacement of wire rope earlier than the time dictated by the criterion of 10% loss in breaking strength. Results also indicate that impact testing is a better evaluator of the susceptibility of wire ropes to brittle fracture than tensile tests.     

Theoretical and experimental investigation of effects of failures on the tensile endurance of elevator ropes

Elevators have an important place in human life just after uprising demands in high rise buildings, skyscraper and luxury residence concepts have surged. Steel wire ropes provide permanent working safety and reliability in the elevator installations. Due to this reason steel wire ropes are one of the vital components of elevators. In this study, effects of discard criteria such as wire breaks, abrasive wear and corrosion where extents of those failures are defined by ISO 4344 standard on the tensile endurance of 6×19 Seale and 8×19 Warrington elevator ropes have been investigated theoretically and experimentally. Tensile endurances of rope samples that have different extents of failure have been determined by using tensile testing machine and comparison is made by undamaged samples for each rope separately. In addition, stress and strain values occurred on the elevator ropes investigated have also been presented. The most critical failure type has been found to be 24 wire breaks for 6×19 Seale rope with fiber core where lifting capacity reduced by 25.99 %. The most critical failure type has been found to be abrasive wear which is 0.1 mm in depth along 100 mm length for 8×19 Warrington rope with independent wire rope core where lifting capacity reduced by 7.93 %.     

Metallurgical Investigation of Failed Locked Coil Track Ropes Used in a Mining Conveyor

A locked coil track rope (LCTR) is essentially composed of wires (round and rail-shaped) laid helically in different layers. These wire ropes are sometimes used in conveyors carrying empty and loaded buckets in mining areas. During service, such wire ropes may fail prematurely due to disintegration/failure of individual groups of wires. To understand the genesis of LCTR wire failures, a detailed metallurgical investigation of failed rope wires was made and included visual examination, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Two types of failed wires were investigated; one is from a 40 mm diameter locked coil track rope and the other from a 53 mm locked coil track rope. Optical microscopy of failed round wires in the 53 mm diameter rope clearly revealed fully decarburized layers at the surface and a few grain-boundary cracks. From the location of the failure, it was clear that apart from static tensile loads, the wire ropes had been subjected to bending and unbending loads near the saddle, as fully loaded or empty buckets traveled access the conveyor. The SEM studies confirmed that the fracture had been caused by initiation of fatigue cracks in the decarburized zone under conditions of repeated bending and unbending stresses superimposed on the static tensile load.     

Effect of abrasive wear on the tensile strength of steel wire rope

Known amounts of external abrasive wear were introduced into a new 6-strand steel wire rope and the effects of this wear on the tensile strength of the rope examined against the rope discard criteria for wear stated in ISO 4309: 1990 and other selected international standards. The variations of strength with degree of wear in the test rope were compared with continuous observations on two haulage ropes which were in service under abrasive wear conditions up to the stage of failure. The results point to a need for greater caution in applying available discard criteria for wear. The results also indicate the existence of two different rapid strength deterioration regimes in strand wire rope under increasing amounts of external abrasive wear and they direct towards test parameter levels which signal the onset of these regimes.     

Effect of degradation and impaired quality on wire rope bending over sheave fatigue endurance

This paper reports the outcome of a series of tests undertaken on six strand and multi-strand ropes to investigate the effects of degradation and impaired quality on the rope’s Bending-over-Sheave (BoS) fatigue endurance. The simulated degradation and quality impairment investigated were: wire breaks (internal and external); plastic wear, abrasive wear, corrosion, slack strands, slack wires and torsional imbalance. Theoretical predictions of rope fatigue endurance have been made to compare with the experimental values, using Feyrer’s equation. The investigation indicates that the bending over sheave fatigue endurance of rope is little influenced by degradation and impaired quality, which is primarily dependent on the rope construction and the diameter ratio of sheave to rope. The study establishes methodologies for assessment of the residual BoS fatigue endurance of degraded or impaired rope, which can inform the practical operation, inspection and discard of wire rope thereby enhancing safety.     

Microstructural manifestations of fractured Z-profile steel wires on the outer layer of a failed locked coil wire rope

Locked coil wire ropes, by virtue of their unique design and construction, have specialized applications in aerial ropeways, mine hoist installations, suspension bridge cables, and so forth. In such specialty ropes, the outer layer is constructed of Z-profile wires that provide not only effective interlocking but also a continuous working surface for withstanding in-service wear. The compact construction and fill-factor of locked coil wire ropes make them relatively impervious to the ingress of moisture and render them less vulnerable to corrosion. However, such ropes are comparatively more rigid than conventional wire ropes with fiber cores and therefore are more susceptible to the adverse effects of bending stresses. The reasons for premature in-service wire rope failures are rather complex but frequently may be attributed to inappropriate wire quality and/or abusive operating environment. In either case, a systematic investigation to diagnose precisely the genesis of failure is desirable. This article provides a microstructural insight into the causes of wire breakages on the outer layer of a 40 mm diameter locked coil wire rope during service. The study reveals that the breakages of Z-profile wires on the outer rope layer were abrasion induced and accentuated by arrays of fine transverse cracks that developed on a surface martensite layer.     

Failure analysis of a wire rope

Wire ropes, pulleys, counterweights, and connecting systems are used for auto tensioning of contact wires of electric railways. A wire rope in one such auto tensioning system suffered premature failure. Failure investigation revealed fatigue cracks initiating at nonmetallic inclusions near the surface of individual wire strands in the rope. The inclusions were identified as Al-Ca-Ti silicates in a large number of stringers, and some oxide and nitride inclusions were also found. The wire used in the rope did not conform to the composition specified for AISI 316 grade steel, nor did it satisfy the minimum tensile strength requirements. Failure of the wire rope was found to be due to fatigue; however, the ultimate fracture of the rope was the result of overload that occurred after fatigue failure had reduced the number of wire strands supporting the load.     

锈蚀高强钢丝力学性能退化的试验研究

该文通过试验研究了锈蚀高强钢丝的锈蚀形貌、产物、力学性能，为其检测评估提供依据。用高分辨率X射线衍射仪和场发射环境扫描电镜分析高强钢丝锈蚀产物，用华朗-3DX+非接触式三维扫描仪确定其截面特性沿钢丝轴向的变化情况，还采用MTS试验机对其进行静力拉伸和疲劳加载试验。通过分析三维扫描数据确定锈蚀高强钢丝表面形貌，基于实测锈蚀高强钢丝力学性能建立本构关系模型参数与锈蚀率的退化关系。试验结果表明:高强钢丝锈蚀截面面积的变异性随锈蚀程度增加越来越显著；极限强度在锈蚀率大于1.25%时小于标准极限强度1770 MPa；断后伸长率在锈蚀率大于5.05%时小于规范限值4%；疲劳寿命在锈蚀率大于4.16%时小于200万次；锈蚀率对高强钢丝弹性模量无明显影响。根据试验结果综合完善了现有规范对锈蚀高强钢丝等级划分的指标值。     

Failure Analysis of Wire Rope Used for Hoisting in Mining: A Case Study

Wire ropes are used in vast range of applications and many of the applications are safety critical. In the mining industry wire ropes are extensively used for hoisting/haulage. Due to the hostile operating load conditions, many wire ropes degrade in service. Fatigue of wires in rope in combination with other detrimental factors is frequently responsible for rope deterioration and premature failure during operation. In this paper the causes of failure of a wire rope used for hoisting in an Indian mine are determined with only a minimum level of information provided by the customer. Samples of the failed rope were obtained and analyzed and potential remedial measures to prevent such degradation are discussed. Reprinted with permission from Proceedings of AIME 2006, held on January 20–21, 2006 organized by Jamia Milia Islamia (a central university) New Delhi-110025, pp. 122–132.     

Failure Analysis of a Drilling Wire Rope

The failure of a multistrand wire rope used in drilling rig hook is investigated in this case study. The wire rope failed during the raising of the rig and caused some serious damage to the rig structure. Throughout its short time of service, the wire had been used a few times for rig up and rig down. The failure investigation is performed by metallurgical examinations and computational analyses utilizing the finite element method. The wire rope was made of AISI 1095 steel. Its chemical composition, ferrite?Cpearlite structure, and high hardness indicate that the wire is a type of extra extra improved plow steel (EEIPS) grade. The morphologies of fractured surfaces indicate tensile overloading of wires. Finite element analysis confirms the overload in core and strands, and compressive contact stresses between wires, and between wires and sheave surface. The results show that high tensile stresses due to the overload and small ratio of sheave-to-rope diameter were responsible for the failure.     

Studies on failure behaviour of wire rope used in underground coal mines

Wire ropes operate at high stress levels and are almost invariably subject to fluctuating loads. The continuous degradation of wire rope affected with operative services will ultimately lead to failure. Study of the causes of failure of two wire ropes from two different Indian coal mines have been carried out and discussed here. The investigating parameters comprises of physical examination, wear & corrosion, lubrication, macro & micro-examination and chemical composition. The investigation revealed that the major cause of failure was due to excessive wear and corrosion resulted in high reduction in diameter ranging from 50%–90% and poor lubrication condition of wire rope. Micro-examination also revealed intergranular corrosion with cracks and pittings, uniform corrosion with pitting along the grain. Further elongated grain which was indicative of stress due to excessive corrosion with sudden impact resulted in its failure.     

Theoretical approach to the solutions of axially loaded complex ropes

Abstract

A rational analysis procedure consisting of a complete cycle of systematic calculations has been developed for the theoretical solutions of problems in describing the behavior of axially loaded complex ropes consisting of wires and strands, which were simulated as particle‐motion models. In essence, axial and rotational strains of a rope were specified. Constitutive relations of the loaded wires and strands were obtained through compatibility of motion requirements. Material law was then imposed to determine the internal force of each wire. Nonlinear equilibrium relations of wires were applied to describe the relationship among sectional stresses and external forces. The theory is used in the analysis of a 6 × 7 wire rope with an independent wire rope core (IWRC). Some solutions and comparisons to other research results have been provided. Results show that the recursive nature of the wire in the model enhanced the calculation of constitutive relations and made it easier to apply to the analysis of complex ropes having multiple orders.     

A finite element model for independent wire rope core with double helical geometry subjected to axial loads

Due to the complex geometry of wires within a wire rope, it is difficult to model and analyse independent wire rope core accurately (IWRC). In this paper, a more realistic three-dimensional modelling approach and finite element analysis of wire ropes are explained. Single helical geometry is enough to model simple straight strand while IWRC has a more complex geometry by inclusion of double helical wires in outer strands. Taking the advantage of the double helical wires, three-dimensional IWRCs modelling is applied for both right regular lay and lang lay IWRCs. Wire-by-wire based results are gathered by using the proposed modelling and analysis method under various loading conditions. Illustrative examples are given for those show the accuracy and the robustness of the present FE analysis scheme with considering frictional properties and contact interactions between wires. FE analysis results are compared with the analytical and available test results and show reasonable agreement with a simpler and more practical approach.     

酸性大气环境下多龄期平面钢框架结构抗震性能试验研究

为研究酸性大气环境下锈蚀对钢材力学性能和平面钢框架结构抗震性能的影响,利用人工气候加速腐蚀试验技术对21组钢材材性试件和4榀平面钢框架结构进行加速腐蚀,并分别对其进行拉伸试验和拟静力试验。拟合拉伸试验数据,得到钢材力学性能（屈服强度、极限强度、伸长率和弹性模量）与失重率之间的线性回归关系;通过拟静力试验,分析了不同锈蚀程度对平面钢框架结构抗震性能（荷载-位移曲线、骨架曲线、强度和刚度退化、耗能能力等）的影响,得到不同锈蚀程度下平面钢框架结构抗震性能的衰退规律。结果表明,锈蚀对平面钢框架结构的抗震性能有着显著的影响,随着锈蚀程度的加剧,平面钢框架结构的极限承载力和耗能能力明显降低,强度和刚度退化严重,而且脆性破坏显著。     

Study of the martensitic transformation in NiTi–epoxy smart composite and its effect on the overall behavior

In this work, the effect of wire phase transformation on the overall thermo-mechanical behavior of NiTi–epoxy composites has been investigated. The shape memory wire received in as drawn condition was subjected to three heat treatments which results to different transformation characteristics. Composite specimens were manufactured by casting followed by curing and post curing process. The mechanical behavior of samples has been determined using standard tensile test. The effect of wire volume fraction and test temperature was investigated as well.It is found that the martensitic transformation occurring in the wire affects the mechanical behavior of the composite specimens. In this way, using the wire with higher transformation stress improves the composite tensile strength. This is achieved either by increasing the test temperature or by using the wires heat treated at lower temperatures. From the experimental results, the martensitic transformation can change the debonding mode. It seems that on the constraint of matrix, the transformation occurs simultaneously at several points in wires that result in regular debonded/undebonded pattern.     

Bending fatigue behaviour of bearing ropes working around pulleys of different materials

Nondestructive quantitative detection and artificial detection were carried out to study bending fatigue behaviour and failure mechanisms of wire ropes. When working around nylon pulleys, wire ropes exhibit a slowly increasing of fracture rate and total damage in one lay length. The bending fatigue life of wire ropes is twice longer than that of ropes working around steel pulleys. The primary failure mode of wire ropes working around nylon pulleys is fatigue fracture and the fracture surfaces of wires exhibit a wide crack propagation zone and narrow tear zone.     

起重钢丝绳通也滑轮的偏角和包角对钢丝绳寿命的影响

在缆索起重机等高效的起重设备设计中,很重要的问题是必须采取多方面的措施来增加所用钢丝绳的使用寿命。这些措施包括应在导绕系统中钢丝绳通过滑轮时采用尽可能小的偏角和适当的包角,以求达到使钢丝绳具有较长的疲劳寿命的目的。本文将对这两方面加以阐述,特别是对偏角和包角影响钢丝绳疲劳寿命的机理作出解释。     

近海大气环境下锈蚀平面钢框架抗震性能试验研究及有限元分析

为研究近海大气环境下锈蚀钢框架结构的抗震性能,采用人工气候加速腐蚀技术对42件钢材材性试件和4榀平面钢框架进行加速腐蚀试验,然后对不同锈蚀程度的钢材材性试件进行拉伸破坏试验,获得锈蚀Q235B钢材力学性能指标（屈服强度、极限强度、伸长率和弹性模量）与其失重率的函数关系。并对4榀平面钢框架进行低周往复加载试验,研究了锈蚀对平面钢框架的破坏机制、滞回曲线、骨架曲线、刚度退化、延性及耗能能力等的影响。结果表明:4榀平面钢框架试件均发生了延性较好的破坏,呈现出混合屈服机制;但随着锈蚀程度的增加,试件承载力、耗能能力显著降低,强度和刚度退化明显,延性变差。在试验研究的基础上,利用通用软件ABAQUS对试验平面钢框架进行了非线性有限元分析,研究了轴压比对其力学性能的影响,结果表明:随着轴压比的增大,试件承载力、延性不断降低。     

矿用钢丝的表面腐蚀形貌及分形研究

钢丝绳中钢丝锈蚀是造成矿用提升钢丝绳失效的主要形式之一,以矿用钢丝为研究对象,在模拟矿井淋水的碱性腐蚀介质下开展长时间的腐蚀试验,观察腐蚀形貌并探讨钢丝的腐蚀规律,基于分形理论计算腐蚀形貌的分形维数。结果表明,分形维数值可以描述钢丝腐蚀过程中表面形貌的复杂程度;腐蚀表面与分形维数密切相关,腐蚀越严重,表面形貌越复杂,分形维数越大;浸泡初期以点蚀为主,失重速率变化较快,分形维数先升高达到一个峰值随后减小;浸泡后期以均匀腐蚀为主,失重速率变化趋于平缓,分形维数逐渐增大。     

Pass schedule of wire drawing process to prevent delamination for high strength steel cord wire

The high-speed drawing of high carbon content steel wires is usually conducted at room temperature employing a number of passes or reductions through several dies. In the multipass drawing process, the temperature rise at each pass affects the mechanical properties of the final product (such as its bending and torsion properties, and its tensile strength). This temperature rise during deformation encourages delamination in the wire, which has a deleterious influence on the torsional properties and durability of the wire. In this study, we investigated the delamination of wires using torsion tests and evaluated the wire temperature during drawing. Our data shows that one of the main reasons for delamination was an excessive rise in wire temperature. Based on our experimental results, in order to prevent delamination due to an excessive rise in wire temperature, a new isothermal pass schedule that could control the wire temperature was designed. The pass redesign for the conventional high carbon (0.75 wt%C) steel cord wire drawing process with delamination was carried out by using the isothermal pass schedule to control the wire temperature. In order to verify the effectiveness of the proposed method, wire drawing and torsion test were conducted. From the results of experiments, it was possible to produce high carbon steel cord wire without delamination.