• Journal of Animal Environmental Science
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• v.5 no.2
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• pp.79-86
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• 1999

Recently more dairy farmers are interested in the utilization of stretch film for wrapping silage material. Most of stretch film are imported from abroad and one domestic product was developed, but its quality has not yet been tested. Therefore this study was executed to offer basic data on this material to the farmers. Measured items were tensile load, extension ratio, and tear propagation strength of stretch films. Comparisons were made among the white color of domestic product(Kw), and white(Fw), black (Fb) and green color(Fg) of foreign products. The result were summarized as follows: 1. Tensile loads of lengthwise direction in stretch films were 557.4, 377.4, 282.6 and 398.4kgf/$\textrm{cm}^2$ in Kw, Fw, Fb and Fg, respectively, and tensile loads of width direction were 415.9, 418.1, 360.2 and 433.0kgf/$\textrm{cm}^2$ in Kw, Fw, Fb and Fg, respectively. 2. Extension ratios of lengthwise direction were 650, 462.5, 512.5% and 537.5% in Kw, Fw, Fb and Fg, respectively, Extension ratios of width direction were 930, 962.5, 950 and 1,000% in Kw, Fw, Fb and Fg, respectively. 3 Tear propagation strength of lengthwise direction 187.9, 148.9, 157.3 and 142.8kgf/cm, and tear propagation strength of width direction were 141.4, 129.8, 140.4 and 106.6kgf/cm in Kw, Fw, Fb and Fg, respectively. 4. In the light transmittance, there was no difference between white and green color stretch film, but it was very low in black one. Therefore, it is thought that research on quality of roll bale silage treated with each stretch film would be needed.

• Journal of Welding and Joining
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• v.6 no.4
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• pp.44-53
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• 1988

The mechanical strengths of buried lamellar tears located near the weld toe in the welded tee joints were evaluated in terms of the loss of load carrying capacity as a function of tear area. In static loading, the load carrying capacity was significantly reduced when tear intercepted over 10% of the cross-sectional area of the welded joints. However, the welded joints containing buried tears still failed at stresses over the yield strength of the base metal in the through-thickness direction in spite of the presence of tears up to 20-25% of the area. Fatigue strength of welded joints containing tears markedly reduced with increasing tear areas. Lehigh lamellar tearing test used in this study to produce speicmens was described in detail. The load carrying cpapacity in static loading was influenced by the reduction of supporting area whereas that in fatigue loading was influenced by the stress-concentration effects of lamellar tears and the reduction of supporting area. In bend tests, the pre-existing lamellar tears always grew up toward the weld toe. However, in fatigue loading, cracks grew up and down simultaneously form both the weld toe and the top of lamellar tears because of stress concentration. In fatigue loading, delaminations and decohesion of inclusion/matrix interface generated in multipass welds provided crack propagation paths and enhanced crack propagation because the tips of delaminations and deconhesios acted as stress raisers.

• Journal of Bio-Environment Control
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• v.5 no.1
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• pp.23-33
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• 1996

This study was performed to induce a quality improvement and standardization of materials used for greenhouse. For this purpose, physical and mechanical properties of agricultural films for greenhouse were measured by kinds and thickness of the films. The properties are composed of impact, tensile, tear propagation strength and light transmittance. The results were summarized as follows. 1. At the impact test result of the falling dart, the thicker the film, the greater the impact strength of soft film. The impact weight at 50 percents is from 158g to 213g and the strength of low density polyethylene(LDPE) film is higher than the rest of any other films. 2. Seeing the leveling of the impact rupture, maximum impact weight which was ruptured very little ranges from 62g to 192g. The impact strength of 0.1mm films was higher than that of 0.05mm as from 1.8 to 3.2 times. 3. Tensile weight covers from 0.95kg to 2.22kg in the test materials, and the weight of lengthwise film is larger than that of width. LDPE film has high value of tensile weight. Elongation range is from 345 to 102 percent and lengthwise elongation is greater than width as much as from 1.4 to 2.7 times. 4. Tea. propagation strength ranges from 80.5kg/cm to 121.7kg/cm, and unlike which of LDPE film has high value, EVA film has low value in the films tested. The width strength is higher than the lengthwise. 5. The light transmittance of the soft film is about 78-92 percent in the range of ultraviolet ray, but has high value in the visible ray range.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.85-90
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• 2000

The fracture toughness and crack propagation behaviors of short nylon66 fiber reinforced Chloroprene rubber nave been Investigated as functions of fiber aspect ratio, fiber content and interphase conditions. The J for crack initiation and rupture were determined for short-fiber reinforced rubber. The values of $J_c$ for most reinforced rubbers were low compared that of matrix. But, $J_r$ at rupture showed a higher value than that of matrix. The crack propagation behaviors were analyzed into 3 patterns with increasing fiber aspect ratio and fiber content. The tearing mechanisms of matrix and fiber reinforced rubber were observed by CCD camera focused on the tip of crack and load-displacement graph. Both cases showed a completely different behaviors