Computational design of the compacted wire strand model and its behavior under axial elongation

C. Erdönmez 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.11

Compacted wire strand is produced by applying compression to the readymade classical wire strand. Therefore, parametric mathematical curves that can create geometric cross-sectional shape of the center and outer wires are not available. The center and outer wires of compacted wire strand are formed with the help of the real cross-sectional compacted wire rope by using the developed computer code. Due to the compaction process cross-sections of the core wire and the outer single helical wires of the circular wire strand becomes to hexagonal and isosceles trapezoidal shapes respectively. The amount of gap in the cross-sectional area is decreased and the contact surfaces of the wires are increased by compaction process. As a result, the diameter of the compacted wire strand is decreased at the end of this process. After the modeling process, a finite element analysis is conducted by applying strain boundary condition to the compacted wire strand. The obtained results are compared with the analytical, test and the finite element analysis results obtained for the classical wire strand model and the good agreement between them is recognized. Meanwhile the analysis results showed that the contact forces are decreased due to the increased contact area between the outer wires of the compacted wire strand. This also proves that the compaction process increases the strength and life span of wire strands.

VCTFK의 반복피로에 의한 소손 패턴의 특성 해석

최충석,송길목,김동우 한국안전학회 2004 한국안전학회지 Vol.19 No.4

In this paper, we analyzed on the characteristics of the stranded wire disconnected by repeated stress. The stranded wires that were used in the experiment are PVC insulated flexible cords(VCTFK: Vinyl Insulated Vinyl Cabtyrc Cord Flat-type) of 0.75mm², 1.25mm², and 2.Omm². They are used to connect the load in low voltage. The stranded wires disconnected by repeated stress were magnified with optical microscope. Using X-ray, the disconnected wire were photo-graphed. we compared mechanical characteristics of the stranded wire between disconnected tendency and allowable current. On the mechanical strength of vinyl cap tire ellipse type cords under bending stress, VCTFK of 1.25mm²was the strongest of them. When it was bent 826.3±7 times, it appeared the disconnected tendency that element wires of VCTFK of 1.25mm²are more about 1.67 times than element wires of VCTFK of 0.75mm². In mechanical strength, VCTFK of 1.25mm² is higher about 1.7 times than VCTFK of 0.75mm². Therefore, we found out that mechanical strength was higher, when the wire had a lot of element wires. In comparison with bending stress, VCTFK of 1.25mm²is the strongest among samples, and it is the most useful in wires of movable type.

Accurate segmented equivalent circuit‑based calculation approach for non‑ideal stranded Litz wire leakage energy

Bin Chen,Pengfei Jiang,Nina Wan,Bo Tang 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.2

Existing calculations of leakage energy in the Litz wire winding region of high-frequency transformers usually ignore the influence of Litz wire stranded structures. Therefore, a new approach is established in this paper to accurately calculate Litz wire leakage energy through the segmented equivalent circuit approach and the two-dimensional finite element method. That is, a single Litz wire in a complete stranded pitch is segmented and equated to the linear structure of multiple inductance cells. First, the two-dimensional finite element method calculates the impedance of each strand of Litz wire. Then the strand current vector is solved according to the system equation. Finally, the current vector is substituted back into the 2D Litz wire transverse-sectional model to calculate the leakage magnetic field energy under the skin effect and internal proximity effect, which is combined with the analytical expression of the external leakage magnetic field to calculate the total magnetic leakage energy of the Litz wire winding. Calculation results indicate that the new approach has an average relative deviation of less than 2.154% and a maximum relative deviation of no more than 4.953%.

과전류에 의해 용단된 소선의 특성해석에 관한 연구

최충석,김향곤,김동욱 한국안전학회 2004 한국안전학회지 Vol.19 No.1

The PVC insulated flexible cords are used mainly as power supply cords of electric appliance. This electric wire is a stranded wire consisted of dozens of strands. In case stranded wires are disconnected by mechanical stress, it weakens electrically. Finally, the over current flows through stranded wires, and electrical fire occurs. In this study, we analyzed the melting properties of strands by over current, such as melting process, melting current and melting time. And we analyzed that quantity of heat for melting, a cross sectional structure, and surface structure by optical microscope and SEM. As analysis results, melting time decreased as melting current increased. And quantity of heat for melting was low, too. From the cross sectional structure of melted wire, when a melting current low and melting time long, it was found that the dendrite structure grew. However, the dendrite structure is hard to grow because growing time is not enough when a melting current high and melting time short.

Analysis of elliptical Hertz contact of steel wires of stranded-wire helical spring

Xiaoyong Li,Shilong Wang,Jie Zhou 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

A stranded-wire helical spring is formed of a multilayer and coaxial strand of several wires twisted together with the same direction ofspiral. Because of the multilayer structure, the wear on the local area of the steel wires’ surface is related to the elliptical contact betweenadjacent wires during working process. Based on Boussinesq potential functions and elastic half-space model, the contact area and surfacepressure of elliptical Hertz contact were investigated. Moreover, these surface contact quantities are used to expand the calculationof subsurface stress relevant to elliptical contact. It is found that the greater contact angle of two contact wires, the smaller contact areaand greater maximum contact pressure. Meanwhile, the magnitude of subsurface von Mises stress is much higher when the contact angleincreases.

인장 실험을 통한 현수교 주케이블용 고강도 평행선스트랜드의 적용성 검토

유훈(Yoo Hoon),서주원(Seo Ju-Won),이성형(Lee Sung-Hyung) 대한토목학회 2011 대한토목학회논문집 A Vol.31 No.6A

본 논문에서는 인장강도 1960 ㎫급 고강도 강선을 이용한 현수교 주케이블용 평행선스트랜드의 적용성을 검토하였다. 현수교 주케이블의 가설공법에 따른 장단점을 분석하고 공장 제작형 평행선스트랜드의 구조 및 가설 방법을 정리하였다. 고강도 강선에 대한 역학적 특성 및 품질 기준을 정리하였고 현재 규격화 되어 있지 않은 현수교용 평행선스트랜드의 품질 기준을 제안하였다. 별도로 제작된 7기의 평행선스트랜드 실험체의 인장 파단 실험을 실시하여 평행선스트랜드의 실용 특성을 검증하였다. 실험 결과 고강도 강선을 적용한 평행선스트랜드 실험체는 본 논문에서 제안한 품질기준에 적합한 안정적인 거동 특성을 보였으며 현수교 주케이블용으로 적합한 구조적 특성을 보유하고 있는 것으로 나타났다. This paper discusses the problems in application of a parallel wire strand with high performance steel wires which have the tensile strength of 1960 ㎫ grade as a major component of the main cables in suspension bridges. Construction methods of main cables in suspension bridges are briefly reviewed by comparing the pros and cons of available methods. Required items for performance and quality of parallel wire strands are described based on the established references. Ultimate tensile strength tests are carried out for seven specimens in order to analyze the behavior of high-performance parallel wire strands. The test results demonstrate that the properties of test specimens are satisfied with performance indexes specified in this paper. The high-performance parallel wire strands are acceptable for application in main cables of suspension bridges.

A strain-based wire breakage identification algorithm for unbonded PT tendons

A.B.M. Abdullah,Jennifer A. Rice,H.R. Hamilton 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.3

Tendon failures in bonded post-tensioned bridges over the last two decades have motivated ongoing investigations on various aspects of unbonded tendons and their monitoring methods. Recent research shows that change of strain distribution in anchor heads can be useful in detecting wire breakage in unbonded construction. Based on this strain variation, this paper develops a damage detection model that enables an automated tendon monitoring system to identify and locate wire breaks. The first part of this paper presents an experimental program conducted to study the strain variation in anchor heads by generating wire breaks using a mechanical device. The program comprised three sets of tests with fully populated 19-strand anchor head and evaluated the levels of strain variation with number of wire breaks in different strands. The sensitivity of strain variation with wire breaks in circumferential and radial directions of anchor head in addition to the axial direction (parallel to the strand) were investigated and the measured axial strains were found to be the most sensitive. The second part of the paper focuses on formulating the wire breakage detection framework. A finite element model of the anchorage assembly was created to demonstrate the algorithm as well as to investigate the asymmetric strain distribution observed in experimental results. In addition, as almost inevitably encountered during tendon stressing, the effects of differential wedge seating on the proposed model have been analyzed. A sensitivity analysis has been performed at the end to assess the robustness of the model with random measurement errors.

사장교 케이블용 7연선 손상 패턴과 구조성능 수준과의 관계 분석

서동우(Dong-Woo Seo),나원기(Wongi Na),김병철(Byung-Chul Kim),박기태(Ki-Tae Park) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.11

본 연구는 사장교 케이블의 주요 부재로 쓰이는 MS(Multi-strand) 타입 7연선의 손상 패턴과 성능수준과의 관계를 파악하기 위해 시도되었다. 사장교 케이블은 준공후 지속적으로 손상이 발생하며 부식 등이 주요 손상원인이다. 이에 따른 손상에 따라 성능저하가 발생하지만 구조적인 특성상 케이블 내부의 손상 패턴을 점검하기 어려우며, 이에 따른 성능저하수준을 정량적으로 평가하기 어려운 실정이다. 본 연구에서는 강연선의 손상 패턴과 성능수준과의 관계를 도출하기 위해 실내실험 및 FEA(Finite element analysis) 해석을 통하여 결과를 비교 분석하였다. 그리고 7연선의 손상을 모사하기 위해 기계적 정밀가공으로 인위적인 손상을 인가하여 성능평가를 수행하였다. 분석 결과 강연선의 손상 크기와 관계없이 손상이 발생한 직후 급격한 구조성능 저하가 발생하며, 강연선 성능수준 평가를 위한 변수로 손상량 이외에 손상 형태가 고려돼야 함을 실험적 및 해석적으로 도출하였다. 향후 본 연구에서 구축하고자 하는 손상 패턴 및 손상량에 따른 DB를 구축하여 사장교 케이블의 안전 관리에 활용될 수 있을 것으로 사료된다. This study investigates the relationship between the damage patterns and structural performance levels of a multi-strand 7-wire strand that is used as an important member of stay cables. Stay cables are continuously damaged after completion, and corrosion is the main cause. However, it is difficult to check the damage pattern inside the cable due to its structural characteristics, and it is difficult to evaluate the degradation level of the damage quantitatively. This study derives the relationship between the damage pattern and the performance level of the stranded wire by comparing results and analyzing them through an indoor experiment and finite element analysis. In order to simulate the damage of a 7-wire strand, artificial damage was applied by mechanical precision machining to perform a performance evaluation. The results of the analysis show that regardless of the damage size of the strand, the structural performance deteriorated immediately after the damage. It was experimentally and analytically deduced that the type and amount of damage should be considered as a parameter for evaluating the performance level of the strand. This information can be used for the safety management of a cable stayed bridge by constructing a database according to the pattern and amount of damage.

강연선의 국부적 손상에 따른 응력 회복길이 분석 연구

서동우(Dong-Woo Seo),김병철(Byung-Chul Kim),정규산(Kyu-San Jung),나원기(Wongi Na),박기태(Ki-Tae Park) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.12

본 연구는 PSC(Post Tensioned Concrete) 교량 및 사장교(Cable Stayed Bridge) 등에 많이 적용되는 강연선의 국부적 손상에 따른 응력 회복길이를 분석하였다. 강연선은 PC 강선(Prestressing Strand)을 여러 줄을 꼬은 강재이며, 재료의 특성상 준공후 지속적으로 손상이 발생하며 부식 등이 주요 손상원인이다. 이에 따른 손상에 따른 성능저하가 발생하지만, 구조적인 특성상 케이블 내부의 손상 정도 및 응력 변화 패턴을 파악하기 어렵다. 교량에 적용된 케이블의 경우 설치 형상에 따라 채수 등에 따라 부식이 취약한 부분이 발행하며, 이로 인해 국부적인 손상이 발행할 수 있다. 본 연구는 교량 Post-Tensioning 또는 케이블 사장재에 주로 적용되는 강연선(7-Wire Strand)의 국부적 손상에 따른 성능저하 경향 및 응력 회복길이를 FEA 해석을 통하여 분석하였다. 향후 본 연구에서 구축하고자 하는 해석모델을 활용하여 PSC 교량 및 사장교 케이블 등의 안전성 평가 및 잔존수명 예측에 활용될 수 있을 것으로 사료된다. This study examined the stress recovery length due to the local damage of a 7-wire strand, which is applied widely to PSC(Post Tensioned Concrete) bridges and cable-stayed bridges. The 7-wire strand is a multiple stranded steel of PC prestressing strand. Owing to the nature of the material, it is damaged continuously after completion with corrosion being the main cause of damage. On the other hand, due to its structural characteristics, it is difficult to grasp the degree of damage inside the cable and the pattern of stress variation. In the case of cables applied to bridges, the parts that are susceptible to corrosion are generated depending on the water supply and installation shape, which may cause local damage. This study analyzed the tendency of performance degradation and stress recovery length according to local damage of a 7-wire strand, which is applied mainly to bridge post-tensioning or stay cables. This study developed a computer-based simulation model that was validated with experimental results. The model developed in this study can be used to evaluate the safety level and estimate the remaining life span of PSC bridges or cable-stayed bridges.

Wire Rope의 등가모델을 위해 이방성 탄성계수 적용에 대한 연구

탁승민(Seung-Min Tak),강민규(Min-kyu Kang),박동진(Dong-Jin Park),이계광,이석순(Seok-Soon Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

Wire rope made of twisted wire is a mechanical elements. And Composed of single or multi-layer strands. It has high Axle strength to weight but small resistance for bending. Wire ropes are widely used in offshore, suspension bridge and elevator, etc. It is difficult to find out the characteristics of a strand or wire rope because of complicated geometry and contact condition. therefore, analytical method than the simple way is needed. In this study, Equivalent model has the same radius of the wire rope. and it has a modulus of orthogonal anisotropy. Tensile & 3 point bending analysis done to compare the results. Strong point that is widely used with wire rope in offshore. and applies equivalent model to strong point and verify the verified.