• Title/Summary/Keyword: Welded defects

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Testing of Mechanical Properties on Dissimilar Metal Friction Welds (異性材料 마찰용접부의 기계적 성질검사)

  • 나석주
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.8 no.1
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    • pp.41-47
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    • 1984
  • Increase of the requirements on quality of welded structures necessitates the improvement of known inspection methods and the introduction of progressive new techniques. Non-destructive methods are the most advanced, but there are considerable difficulties in using the methods of radiography with electromagnetic rays and ultrasonic testing in the inspection of dissimilar metal friction welds, because their physical and mechanical properties are changed very rapidly at the interface. The values of simple mechanical test for dissimilar metal friction welds have always been dubious, as the strength of the bond is often greater than that of the softer materials being jointed. Thus, in this paper some conventional mechanical testing methods are examined in an attempt to determine a technique for dissimilar metal friction welds, which will give a reliable quantitative indication of the weld quality. From the considered static and dynamic testing methods the impact bending test on unnotched and notched specimens are the most sensitive to find out the small joining defects in the interface.

ULTRASONIC DETECTION OF INTERFACE CRACK IN ADHESIVELY BONDED DCB JOINTS

  • Chung, N.-Y.;Park, S.-I.;Lee, M.-D.;Park, C.-H.
    • International Journal of Automotive Technology
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    • v.3 no.4
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    • pp.157-163
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    • 2002
  • It is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing (NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam (DCB). An optimal condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated and discussed. The experimental values are in good agreement with the computed results by boundary element method (BEM) and Ripling's equation.

Influence of Nickel Alloy Weld on the Mold Surface Cracks (니켈 합금 용접이 금형 표면의 균열 발생에 미치는 영향)

  • Jeong, Hyae-Dong;Lee, Ji-Hoon;Hong, Min-Sung
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.4
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    • pp.478-483
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    • 2011
  • Cast mold has low wear-resistance comparing with other alloyed molds which result in lower production rate and high cost of products. Recently, various weld methods are being applied to increase the wear-resistance of molds and to extend mold life. Among them, nickel alloy weld process increases the hardness irrelevant to its machinability and creates very uniform structures. In addition, it causes better wear-resistance and reduces shrinkage defects. In this paper, we analyze the mold surface cracks welded by nickel alloy and propose the methods to improve the mold surface and its wear-resistance. It has been found that nickel alloy weld does not affect the inside crack of mold but has an influence on the surface crack seriously. Results show that the start and growth of fatigue cracks have been delayed about 3 times and reduced approximately 75%, respectively, and the mold surface cracks are decreased about 5.7 times.

A Feasibility Study on the Use of Autogeneous GTAW for Correction of Distortions in Welded Aluminum Alloy Structures (알루미늄 熔接構造物의 變形橋正을 위한 Autogeneous GTAW의 適用 可能性 硏究)

  • 하용훈;강춘식;유순영
    • Journal of Welding and Joining
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    • v.10 no.1
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    • pp.20-34
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    • 1992
  • Characteristics of two correcting methods, a new Autogeneous GTAW heating (TIG) method and the conventional GMAW bead-on plate welding(MIG) method, for distorted aluminum fabrication structures were studied. As a result of microscopic study of Autogeneous GTAW heating and GMAW bead-on plate welding areas, porosities in weld metal and surface cracks in local heating zone were found. Through the mechanical tests, it was verified that porosities decrease tensile strength and surface of distortion, angular displacement and transeverse shrinkage were measures and compared. In order to investigate changes of material properties in heating area and cause of defects such thermal stresses were calculated by ADINA. Through the computations of transient thermal stresses and microscopic observation of fracture surface, thermal stress was found to be the cause of crack during Autogeneous GTAW heating.

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Stress Concentration of Longitudinal Rib to Deckplate Welded Joint in Orthotropic Steel Bridge Decks (강상판 종리브.바닥강판 응접연결부의 응력집중)

  • 장동일;최동호;최준혁;김도환
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1999.04a
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    • pp.343-350
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    • 1999
  • Orthotropic steel bridge decks are potentially liable to cause fatigue cracks due to weld defects, residual stresses, and in-plane or out-of-plane stresses. In particular, the cracks propagated through deckplate in longitudinal rib to deckplate joints occur at weld toe and weld root due to stress concentrations. Numerical parametric studies are performed to show the Influence of the parameters on the stress concentration at the connection between the longitudinal rib and the deckplate. The parameters include root gap, toe angle $\theta$, toe radius $\rho$, and weld penetration. This study provides a fundamental point for the improvement of fatigue resistance and the estimation of the fatigue crack propagation in wekded joint details.

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Detection of Interface Crack Using Ultrasonic Method in Adhesively Bonded Joints (초음파 탐상법을 이용한 접착이음에 대한 계면 균열의 검출)

  • Jeong, Nam-Yong;Park, Seong-Il;Lee, Myeong-Dae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.3
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    • pp.415-423
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    • 2001
  • In is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing(NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interface crack length in the adhesively bonded joints of double-cantilever beam(DCB). The optimum condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated. The experimental values are in good agreement with the computed results by boundary element method(BEM) and Riplings equation.

A Study on the Characteristics of Thermit Welded Rail (테르밋 레일용접의 특성에 관한 연구)

  • 나성훈;양신추
    • Proceedings of the KSR Conference
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    • 2001.10a
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    • pp.488-493
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    • 2001
  • CWR technology is generally believed to contribute to the increase of train speed and bring a variety of significant advantages, such as the decrease in track works, noise and vibration as well as the improvement of passenger comfort. In CWR technology, welding is considered to be one of the most important element technologies. Among the various welding methods, thermit welding is the most frequently used one for site welding since the operation is simple and the instruments are light as well as easy to deal with. However, it could cause interference with safety operation of trains since thermit welding points, are essentially made of castings and there are potentialities of defects according to the operation conditions, the environment of the site as well as the dexterity of the worker. This study tries to describe the characteristics of thermit welding, defect-causing factors and defect-detection methods at welding points.

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A Study on Fatigue Strength Characteristics of Weld Joint using Metal Type Flux Cored Wire (금속계 플럭스들이 용접이음부의 피로강도 특성에 관한 연구)

  • 강성원;신동진;김환식
    • Journal of Welding and Joining
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    • v.12 no.4
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    • pp.151-161
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    • 1994
  • FCAW has wide application in ship fabrication, maintenance and field erection. It has many advantages over SMAW.SAW and GMAW process. In many applications, the FCAW provides highquality weld metal. This method can reduce weld defects especially porosity and spatter. But the fatigue characteristics of those deposited metal have been rarely investigated. The purpose of this study is to investigate the cyclic stress-strain behavior and fatigue tests by the constant strain control were carried out on the rounded smooth specimen with deposited metal using the metal type flux cored wire. As the results of this study for the deposited metal welded by the metal type flux cored wire, the hardening or softening characteristics under cyclic load were investigated and cyclic stress-strain curve, strain-fatigue life curve, stress-strain function and fatigue life relation which are useful to estimate the fatigue life under the stress concentration condition were obtained.

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Detection of Interface Crack Using Ultrasonic Method in Adhesively Bonded Joints (초음파 탐상법을 이용한 접착이음에 대한 계면균열의 검출)

  • Chung, Nam-Yong;Lee, Myung-Dae;Park, Sung-Il
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.97-102
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    • 2000
  • It is well recognized that the ultrasonic methods is one of the most common and reliable nondestructive testing(NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam(DCB). The optimum condition of transmission coefficients in the adhesively bonded joints and it's experimental accuracy by the ultrasonic method have been investigated. The experimental values are in good agreement with the computed results by boundary element method(BEM) and Ripling's equation.

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The Development of Simplified Ultrasonic CT System and Its Application to the Evaluation of Weld Metal

  • Kim, Kyung-Cho;Hiroaki Fukuhara;Hisashi Yamawaki;Tetsuya Saito
    • Journal of Mechanical Science and Technology
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    • v.15 no.1
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    • pp.52-60
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    • 2001
  • In this paper, as a new measurement method to estimate the change of material condition, the simplified ultrasonic CT system, which uses the information of three directions, that is, $90^{\circ}$, $+45^{\circ}C$and $-45^{\circ}C$ about inspection plane is proposed. Use of simplified CT system has two merits: Firstly, the measurement time is very short compared with general CT. Secondly, it can detect sensitively small defect in vertical or slant direction about inspection plane because the obtained image is CT image calculated from three directions. From these merits, this method can be considered as an effective method to evaluate material conditions. The basic performance of the proposed method was confirmed through several specimens with several simple defects. In order to confirm the applicability of actual NDT, several kinds of welded specimens are investigated. The result showed that the CT image obtained had good agreement with actual defect of specimens.

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