• 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%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.487-490
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• 2004

In this paper, we investigated the characteristics of initiation and propagation behavior for fatigue crack observed by changing various shapes of initial crack and magnitudes of loading in modified compact tension shear(CTS) specimen subjected to shear loading. In the low-loading condition, the secondary fatigue crack was created in the notch root due to friction on the pre-crack face grew to a main crack. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Influenced by the shear loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. The propagation path of fatigue crack under the Mode II loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.302-307
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• 2004

This paper reviewed characteristics of fatigue crack behavior observed by changing various shapes of initial crack and magnitudes of loading in compact tension shear(CTS) specimen subjected to shear loading. In the high-loading condition, fatigue crack under shear loading propagated branching from the pre-crack tip. Meanwhile, the secondary fatigue crack in the low-loading condition which was created in the notch root due to friction on the pre-crack face grew to a main crack. Influenced by the mode II loading condition, fatigue crack propagation retardation appeared in the initial propagation region due to the reduction of crack driving force and friction on crack face. In both cases, however, fatigue cracks grew in tensile mode type. Propagation path of fatigue crack under the shear loading was 70 degree angle from the initial crack regardless of its shape and load magnitude.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.485-488
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• 2000

In this study, the fatigue characteristic of spot weld specimen was studied by using the various specimen. The specimen types were tensile shear specimen welded one spot and two spot, and cross tension. The tensile tests and fatigue tests were executed to know the mechanical properties under static and fatigue load condition. In addition, the relationship was illustrated by finite element method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.98-104
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• 2006

In this paper, for the purpose of investigation the acoustic emission(AE) behaviors during resistance spot welding process and tension test of spec steels. As the results present the resistance spot welding method that can get suitable welding qualities or structural integrity estimating method. The resistance spot welding process consists of several stages: set-down of the electrodes; squeeze; current flow; forging; hold time; and lift-off. Various types of AE signals are produced during each of these stages. For tensile-shear test and cross tensile test in resistance spot welded specimens, fracture pa 야 ems are produced: tear fracture; shear fracture; and plug fracture. Tensile-shear specimens strength appeared higher than cross tensile specimens one. In case of tensile-shear specimen happened tear fracture that crack happens in most lower plate. Also, in case of cross tensile specimens, upper plate and lower plate are detached perfect fracture was exposed increases a little as acting force is lower than ordinary welding condition. Therefore, the structure which is combined by resistance spot welding confirmed that welding design must attain so that shear stress may can interact mainly.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.55-60
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• 2001

The automobile is made up of thousands of parts. Some parts are formed by pressing and combined by spot welding. To find weldability conditions of spot welding, clearance between two welding plates was made and after spot welding, weldability is evaluated by means of tensile shear load, nugget size and shape. Specimen used in this study was a steel plate of 1.2mm thickness and electrode was Cu-Cr alloy of 6mm diameter. When spot welding started, the clearance of two specimens was changed 0mm, 3mm and 5mm and distance from vise to measure influence of bending moment 25mm, 45mm, 65mm step by step. The fractured surface of specimen after this test was observed by Optical Microscope to measure microstructure and nugget shape. When clearance of two specimen was 3mm and 5mm, strength and nugget size was decreased and nugget shape was not clear. The much bending moment and crosshead speed are the much tensile shear load is.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.4
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• pp.394-400
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• 2007

The properties and weldability of lap joints by PFSW with 1050 Al sheet was investigated according to tool shape. dimension and welding condition. Tensile shear test was carried out for lap jointed specimen, and the hardness in the joint regions was examined. Moreover interfacial joining length, metallograph and failure location of the lap-jointed cross section were discussed. Two tool types were a simple cylindrical type and a notched cylindrical type. Under joining conditions such as plunging depth of 2.2mm. rotating speed of 1600rpm and dwelling time of 3s, the tensile shear strength of lap-jointed specimen by the notched type tool was superior to that by simple cylindrical type tool. The maximum tensile shear load of lap jointed specimen was 5807N. Optimal dimensions of the notched type tool were as follows : diameters of the shoulder and pin were $18{\phi}mm$ and $10{\phi}mm$, and pin length was 2.2mm.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.167-174
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• 2003

It is absolutely natural to be interested in durability and safety of the structure under shear behavior. To fulfill this desire, a comparison on the shear behavior between steel fiber reinforced concrete both simple and continuous beams is done to use in the field working. Several operations are conducted : First of all, plan for optimal combination is standardized. Second, resistance for shear has been generalized in that it is decided by combination of individual elements. Third, as the fracture of tensile bar leads to destruction of specimen, shear behavior of whole specimen is decided by stress working on tensile bar. It should be generalized for other specimens also. Forth, evidence of the softness of steel fiber reinforced concrete beam by experiment lead to application in the fields. Finally, numeral values of the steel fiber reinforced concrete are analyzed and the result is compared to those of experiments. With these consequences, this study was done for the application to dynamic structures such as bridges and the repair and rehabilitation.

• Journal of Welding and Joining
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• v.20 no.1
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• pp.55-61
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• 2002

The automobile is made up of about twenty thousand parts. Some parts are formed by pressing and combined by spot welding. Among them, steel palate of fuel tank is formed in the metal mold and bending parts are jointed by spot and seam welding. To find weldability conditions of spot welding, clearance between two welding steel plates was made and after spot welding, weldability is evaluated by means of tensile shear load, nugget size and shape. Specimen used in this study was a mild steel of 1.2mm thickness and electrode was Cu-Cr alloy of 6mm diameter. When spot welding started, the clearance of two steel plates was changed 0mm, 3mm and 5mm step by step. The fractured surface of specimen after this test was observed by Optical Microscope to measure microstructure and nugget shape. When clearance of two specimen was 3mm and 5mm, strength and nugget size was decreased and nugget shape was not clear.

• Journal of Welding and Joining
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• v.16 no.1
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• pp.106-113
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• 1998

In this study, the plug weldability of STS 304 was investigated. The parameters which influence plug weldability were pushing pressure of the plates, position of welding wire and composition of shielding gases. Among these factors, the composition of shielding gases and hole diameter of the upper plate were found to be the major factors influencing weld quality. To evaluate weldability, tensile shear strength of the plug welded specimen was measured and compared with tensile strength of butt welded specimen. Hardness was measured for both plug weld and butt weld. The microstructure of the weld metal and HAZ were also characterized.