• Title/Summary/Keyword: Tensile strength of welded joint

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Variation of Welded-Joint Tensile Strength of GMA Welded Accelerated-Cooled Steel (가속냉각강 GMAW 용접이음부의 강도 변화)

  • 방국숙;정성욱
    • Journal of Welding and Joining
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    • v.18 no.6
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    • pp.83-88
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    • 2000
  • Variation of welded-joint hardness and tensile strength of a accelerated-cooled fine-grained ferritic-pearlitic steel with heat input was investigated. In a weld heat-affected zone, a softened zone was formed and it had lower hardness than that of a base metal. While the width of a softened zone increased continuously with an increase of heat input up to 100kJ/cm. the minimum hardness in a softned zone was almost constant after a continuos decrease up to 60KJ/cm. Because of a softened zone, the welded-joint was fractured in the HAZ and its maximum reduction of tensile strength was about 20%. Measured welded-joint tensile strength and calculated minimum tensile strength in a welded-joint was almost same, which means that the plastic restraint of a softened zone did not occur in this experiment. It is believed that as a softened zone width-to-specimen thickness ratio is as high as 2~6 in this experiment, the plastic restraint effect does not occur. Theoretical analysis shows that the plastic restraint effect occurs only when the ratio is below 0.5.

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A Study of Tensile Strength in 18% Ni Maraging Steel Sheet Welded with Electron Beam (E.B 용접된 18% Ni 마르에이징강 박판의 인장이음강도에 관한 연구)

  • 정병호;김무길;김원녕
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.2
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    • pp.157-165
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    • 1997
  • The strength level of welded joint in room temperature and elevated temperature up to $600^{\circ}C$ was investigated in 250 and 300 grade 18% Ni maraging steel sheet welded with electron beam. The results obtained in this study are as follows; 1. Optimum welding heat input was 600J/cm in 1.0mm thickness and the room temperature tensile strength, joint efficiency of welded joint treated with optimum aging condition were found to be about 166kg/$mm^2$, 95% in 250 grade, 189kg/$mm^2$, 92% in 300 grade maraging steel sheet, respectively. 2. Tensile strength of welded joint in room temperature increased slightly by aging after repeated solution heat treatment, but the fracture mode showed a shear. 3. Joint efficiency at a temperature between $540^{\circ}C$and $600^{\circ}C$ found to be about 72% to 55%, but the joint efficiency exceeded about 90% below $300^{\circ}C$. 4. The fracture occurred in most weld metal, and the fracture surface showed a shallow dimple.

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Failure analyses of friction welded Al/Cu joints (Al/Cu 마찰용접부의 파단분석)

  • 박재현;권영각;장래웅
    • Journal of Welding and Joining
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    • v.12 no.1
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    • pp.80-93
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    • 1994
  • The microstructure and fractography of the friction welded joint of Al to Cu have been investigated in order to understand the formation of intermetallic compounds and their effects on the failure in tensile test of the joint. The variation of welding pressure did not affect significantly the tensile strength of joint. However, the tensile strength of joint decreaed as welding time increased. The thickness of reaction layers of welded joints was several micro-meters and mainly composed of intermetallic compounds of $CuAl_2$, $Cu_9Al_4$ and Al+$CuAl_2$. The thickness of $CuAl_2$, $Cu_9Al_4$ was increased with welding time. However, $CuAl_2$ was gradually changed to $Cu_9Al_4$ which caused the decrease of tensile strength . Even though the morphology of fractured surfaces depended upon the welding time, the failure occurred along $CuAl_2$ intermetallic compound itself or between $CuAl_2$ and $Cu_9Al_4$ in most cases.

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Effect of Annealing on the Improvement of Strength of Butt Welded Joint (맞대기 이음용접의 강도향상을 위한 어니일링 효과에 관한 연구)

  • ;;Shin, Keun-Ha
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.3 no.2
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    • pp.43-47
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    • 1979
  • This paper presents the effect of stress relief annealing on mechanical properties in single Vee-groove welding joint. In this experiment, the investigation of annealing effect on mechanical properties of test material carried out by changing the annealing temperature from $600^{\circ}C$ to $900^{\circ}C$ under the given conditions. The results pbtained by this study are as follows: (1) Under the constant welding conditions, the tensile strength of test welded joint decrease in accordance with the increase of annealing temperature. The experimental results show that the reduction rate of tensile strength is about 35.09% of base metal strength. (2) Microhafdness distribution of welded joint bring about the maximum hardness near the bended line of welding joint. (3) Izod impact energy of welded joint in increase in according to the rise of annealing temperature and the peak energy of impact test occurs at $800^{\circ}C$

A study on the strength characteristics of welded joints in aluminum carbody of rolling stock (알루미늄 철도차량 차체 용접부의 강도 특성에 관한 연구)

  • 서승일
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.290-292
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    • 2004
  • In this paper, static and fatigue load tests for the specimens, components and carbody were carried out to investigate the strength of welded joints in aluminum rolling stock. Tensile load test results showed that the static strength of welded joint for heat-treated alloys is reduced significantly and fatigue strengths are scattered by the welding imperfections. Component and whole carbody fatigue test results showed agreements with the design fatigue strength standards for specimens of same joint detail. Test results revealed that full penetration welding and strict management of welding procedure are crucial for securing strength of welded joint in aluminum carbody.

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Characteristics of Adhesive bonded Joints of Steels for Automobile(I) (자동차용 강판의 접착특성 - 접착부위 접합 강도와 영향인자 -)

  • 윤병현;권영각
    • Journal of Welding and Joining
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    • v.13 no.2
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    • pp.106-114
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    • 1995
  • The characteristics of adhesive bonded joint of steels for automobile were investigated. Shear and tear strength were tested and analyzed for the joints of cold rolled steel sheets bonded with three kinds of epoxy and urethane based adhesive. The results showed that the tensile shear strength and the tear strength of adhesive joint were affected by the shape of adhesive joint such as the length and width of adhesive joint. The thickness of adhesive layer was very important factor affecting the bonding strength. The shear strength increased with decrease of the thickness of adhesive layer, while the tear strength decreased as the thickness of adhesive layer decreased. In comparison with the strength of spot welded joint, the shear strength of adhesive Joint was higher than that of spot welded joint, but the tear strength of adhesive Joint was lower than that of spot welded joint.

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A Study on the Feasibility of Partial Penetration Laser Welding for the Lap Joint of 390MPa High Strength Steel Sheets (390MPa급 고장력강판의 경치기 레이저 용접에서 부분용입 용접의 적용 가능성에 대한 연구)

  • 이경돈;박기영;김주관
    • Journal of Welding and Joining
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    • v.20 no.2
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    • pp.95-101
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    • 2002
  • After high power lasers are avaliable in the commercial market, the number of applications of the laser welding has been increased in manufacturing industries. Although the tailored blank laser welding of butt jointed steel sheets is well known recently in the automotive industries, the lap joint laser welding is a new technology to the automotive manufacturing people as well as the design people. But the deep penetration laser welding seems to be preferred to the partial penetration welding for the lap joint welding in the automotive manufacturers because the partial penetration is a serious deflect for the butt joint. In this study, the feasibility of partial penetration welding fur the lap joint $CO_2$ laser welding was studied fur the 1mm thick 390MPa high strength steel sheets for automotive bodies. The process window of the lap joint partial penetration welding was obtained from experiments with the gap size and the welding speed as process parameters. The partial penetration welding was found excellent on the basis of the tensile shear strength and sectional geometry. The bead width, input energy Per volume, tensile-shear strength, deformation energy and the sectional geometries after tensile-shear tests of partial penetration welded specimens are compared with those of full penetration welded specimens with a series of gaps and welding speeds.

Evaluation on the Properties of Strain Distribution of the sopt welding specimen under tensile-shear load (인장-전단하중을 받는 점 용접재의 변형률 분포 특성 평가)

  • 김덕중
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.8 no.6
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    • pp.113-118
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    • 1999
  • In order to evaluate strength of spot welded joint, at first it is importent that we should know strain distribution near nugget zone. During loading, in HAZ, compressive strain increase with Increase of load, but in nugget zone tensile strain increase. During unloading, on the other hand, even through the decreases, the strain variation is not almost appeared in nugget zone and HAZ. In nugget boundary zone, the strain range increases continuously along with load increase on outer surface, but the strain increases continunously and decreases rapidly beyond yield strength on inner surface. In this paper, strain distribution are measured in inner and outer surface with variation of thickness and load under tensile-shear load. Tensile-shear strength increased as with increase of specimen thickness. As for thickness increase rates are 25%, 50%, 100%, and 150%, tensile-shear strength in crease rates are 40%, 81%, 130% and 228%.

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A Study on Fatigue Design of CT-Type Spot Welded Lap Joint (CT형 점용접 이음재의 피로설계에 관한 연구)

  • Baek, Seung-Yeb
    • Journal of Welding and Joining
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    • v.28 no.2
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    • pp.91-95
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    • 2010
  • Stress distribution and deformation on the CT-type(Cross Tension type) spot welded lap joint subjected to out of plane tensile load were investigated by finite element method. Using the maximum principal stresses at the nugget edge obtained by FEM analysis, evaluated the fatigue strength of the CT-type spot welded lap joints having various dimensions and materials. and also, the influence of the geometrical parameters of CT-type spot welded lap joints on stress distribution and fatigue strength must be evaluated. thus, in this paper, ${\Delta}P-N_f$ curve were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curve were systematically rearranged in the $\Delta\sigma-N_f$ relation with the hot spot stresses at the CT-type spot welded lab joints. It was found that the proposed $\Delta\sigma-N_f$ relation could provide a more reasonable fatigue design criterion for the CT-type spot welded lap joints.

A Study on the Strength Characteristics of Welded Joints in Aluminum Carbody of Rolling Stock (알루미늄 철도차량 차체 용접부의 강도 특성에 관한 연구)

  • Seo Sung-Il
    • Journal of Welding and Joining
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    • v.23 no.1
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    • pp.35-40
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    • 2005
  • In this paper, static and fatigue load tests for the specimens, components and carbody were carried out to investigate the strength of welded joints in aluminum rolling stock. Tensile test results showed that the static strength of welded joint for the heat-treated alloy is reduced significantly and fatigue strength data are scattered by the welding imperfections. Component and whole carbody fatigue test results showed agreements with the design fatigue strength standards for specimens of the same joint detail. Test results revealed that full penetration welding and strict management of welding procedure are crucial for securing the strength of welded joint in aluminum carbody.