共查询到20条相似文献,搜索用时 109 毫秒
1.
Gu Wei Chu Jianxin 《IEEE transactions on instrumentation and measurement》2002,51(1):120-124
Based on analyzing the magnetic leakage feature of wire rope defects, the longitudinal resolved vector Bot of the defect leakage field is taken for the object to be tested. In order to detect the weak magnetic leakage field, a fluxgate sensor of single core and single winding is developed. Using the fluxgate, a new kind of transducer for testing defects of wire rope has been designed. The structure and interface circuit of the transducer are studied. The experimental results of detecting the LF and LMA defects of the wire rope are presented 相似文献
2.
Madhavarao Krishnadev Maude Larouche V. I. Lakshmanan R. Sridhar 《Journal of Failure Analysis and Prevention》2010,10(4):341-348
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. 相似文献
3.
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. 相似文献
4.
金刚石绳锯在切割圆弧板材时,受到进给方向的阻力,形成"线弓角",使板材中部产生"过切",严重时导致材料报废.为解决这一问题,提出了线弓角的概念,从理论上提出了一种基于悬臂式力传感器的绳锯线弓角的静态测量方法,通过轴力传感器输出的电压值计算出线弓角度.试验在自行设计和搭建的绳锯线弓角测量平台上进行,用钢丝绳模拟串珠绳产生线弓角,并进行导轮受力与线弓角关系的静态测量试验分析,以验证该方法测量线弓角的可行性.试验结果表明:在一定范围内,串珠绳初始张紧力越大,线弓角的计算值越接近理论值.因此,采用所提出的测量方法,当装有轴力传感器的导轮处在刚好与钢丝绳接触的状态下,选择合适的初始张紧力,可以测得较准确的角度值. 相似文献
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为查明某玻璃厂一台通用桥式起重机钢丝绳断裂导致货物坠落的事故原因,对断裂的钢丝绳进行了理化检验,并对钢丝绳滑轮组和防跳绳安全保护装置的结构进行了分析。结果表明:钢丝绳断裂为挤压磨损致使钢丝绳不能承受较大载荷而产生的一次性大应力断裂,导致事故的直接原因是防跳绳安全保护装置的结构设计存在严重缺陷,使钢丝绳脱出滑轮槽在轴衬套上运行,产生较大的滑动摩擦力,使钢丝绳磨损变形。 相似文献
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在组合法计算彩色显像管偏转系统的基础上,对25英寸700线彩色显像管所用偏转线圈进行了优化设计。选取荧光屏光栅结点上的像差作为优化目标函数,选取线圈调制极上绕线密度的傅里叶展开系数作为优化参数,采用分步阻尼法优化设计出了25英寸700线彩色显像管用偏转线圈。根据实际的实验条件,绕制了25英寸700线彩色显像管用垂直偏转线圈,并与已有的25英寸同类彩色显像管所用偏转线圈进行了比较和分析。 相似文献
9.
Donglai Zhang Min Zhao Zhihui Zhou Shimin Pan 《Journal of Nondestructive Evaluation》2013,32(1):37-43
Magnetic flux leakage (MFL) techniques are used extensively for non-intrusively detecting and characterizing wire rope defects. Traditionally, MFL signals are captured with induction coil sensors. However, the output of coil sensors is related to the wire rope speed, and they can only provide the axial distribution along the wire rope. Hall sensors array are designed due to the limitation of coil sensors. In this paper, a Hall sensors array was designed to capture the MFL signals both axially and circumferentially. 30-channel data from Hall sensors are processed to compose a MFL image. A digital image process technique is introduced to preprocess the MFL image, the MFL images from different types of defects show different texture characteristics. Gray level co-occurrence matrix is utilized for feature extraction of the texture in the MFL image. Five typical eigenvalues (contrast, correlation, energy, homogeneity and entropy) are used as the inputs of back propagation (BP) networks. After training with typical samples, the BP networks show good performance in the quantitative recognition of different defects. The result of this work shows that texture analysis method for MFL image is suitable for feature extraction and quantitative detection of wire rope defects. 相似文献
10.
Magneto-impedance element 总被引:2,自引:0,他引:2
Mohri K. Bushida K. Noda M. Yoshida H. Panina L.V. Uchiyama T. 《IEEE transactions on magnetics》1995,31(4):2455-2460
The magneto-impedance (MI) effect is a phenomenon in which the voltage induced by a high frequency current source in a ferromagnetic wire changes with the application of an external field. A giant MI effect was found in amorphous magnetic wires having a composition of (Fe 0.06Co0.94)72.5Si12.5B 15 and a magnetostriction of (-10-7). The amplitude of the wire voltage decreased by 40% at 1 MHz, 60% (600 kHz) and 50% (150 kHz), for wires having diameters 30 μm, 50 μm and 124 μm, respectively, under the influence of an external longitudinal field of about 10 Oe (800 A/m). A highly sensitive and quick-response field sensor was constructed using a 200 MHz resonant multivibrator bridge-circuit combining two MI-effect elements of 1 mm length with two field effect transistors (FET). Highly sensitive flux detection was carried out by using the small MI sensor head on a rotary encoder magnet having 512 poles and a diameter of 30 mm. Discussion of a mechanism for the MI effect considers the skin effect in an amorphous wire with high circumferential anisotropy 相似文献
11.
Qianru Wu Jiping Lu Xuezhi Shi Qian Ma Shuiyuan Tang 《Materials and Manufacturing Processes》2017,32(16):1881-1886
Wire-feed additive manufacturing is cost competitive and efficient in producing large and complex components in aerospace applications. However, for the additive manufacturing technologies with lateral wire feeding, including laser wire additive manufacturing, electron beam freeform fabrication, plasma arc welding, and gas tungsten arc welding, it is difficult to obtain uniform deposit due to the variable wire feeding direction. In this work, high-angle wire feeding method is proposed to obtain uniform deposit in gas tungsten arc welding-based additive manufacturing. The results illustrate that low wire feeding angle (30°–50°) causes the deposition to break at the back feeding, meanwhile too high wire feeding angle (70°) leads to many littered droplets on one side of the deposition at the condition of side feeding. A uniform deposition can be obtained at the optimal wire feeding angle of 60° in any wire feeding direction, and the reasons have been discussed based on the temperature distribution characteristics of the arc and molten pool. Furthermore, the deposition layers exhibit similar columnar prior β grains, basketweave microstructure, and tensile properties from different wire feeding directions. 相似文献
12.
《IEEE transactions on magnetics》2007,43(5):2001-2008
13.
目的针对传统钢材硬度低、不耐磨损的问题,选用WC颗粒来增强传统钢材性能,研究不同工艺对WC颗粒增强钢基材料的影响。方法采用埋弧焊方法,将含有WC颗粒的药芯焊丝在钢板表面进行堆焊,采用SVS3020显微镜、光学显微镜和显微硬度计对焊缝的显微组织进行观察与分析。结果随着焊接电流、电压的增大,焊缝成形逐渐完好,无焊缝缺陷,焊接速度增大,焊缝有夹渣缺陷产生;焊缝硬度随着电流、速度的提升而增大,但随电压的提升而下降。结论埋弧焊焊接选用350 A电流、32 V电压和20 m/s速度成形的焊缝质量最佳,基体的稀释作用对堆焊合金层的显微硬度也有明显影响。 相似文献
14.
K. P. Balan 《Journal of Failure Analysis and Prevention》2002,2(3):71-74
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. 相似文献
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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 %. 相似文献
17.
Amitava Ray S. K. Dhua K. B. Mishra S. Jha 《Journal of Failure Analysis and Prevention》2003,3(4):51-55
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. 相似文献
18.
直缝埋弧焊管焊接完成后,射线检验发现明显连续白色亮带,分析发现其化学成分、力学性能和焊接工艺等方面都满足规范要求,但在金相分析时发现明显的未熔合缺陷。产生未熔合缺陷的原因为四丝焊接时第二丝焊接断弧,送丝轮出现故障,从而停止送丝,最终形成该缺陷。该缺陷处理方法为补焊。 相似文献
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The instrumented indentation test is a promising nondestructive technique for evaluating mechanical properties of metallic materials. In this study, the localised mechanical properties of welded joint of 304 austenitic stainless steel were characterised with the instrumented indentation test. The single V-groove welded joint was produced using the electric arc welding. A series of instrumented indentation tests were carried out at different regions, including base material, weld zone and heat-affected zone (HAZ). A soft zone regarding strength properties was found in the coarse-grain HAZ. The results show that the HAZ has the lowest yield strength and tensile strength (263.6 MPa, 652.5 MPa) compared with the base material (307.4 MPa, 807.9 MPa) and the weld zone (285.6 MPa, 702.1 MPa). In addition, characterisations of microstructure, microhardness and conventional tensile tests have been performed for comparison. The results reveal that the localised mechanical properties of welded joint of austenitic stainless steel can be represented effectively with the instrumented indentation technique. 相似文献