• Corrosion Science and Technology
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• v.16 no.4
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• pp.209-225
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• 2017

Development of high strength steel requires proper understanding of hydrogen behavior since the higher the steel strength the greater the susceptibility of hydrogen assisted cracking. This paper provides a brief but broad overview on hydrogen entry and transport behavior of high-strength ferritic steels. First of all, hydrogen absorption, diffusion and trapping mechanism of the steels are briefly introduced. Secondly, several experimental methods for analyzing the physical/chemical nature of hydrogen uptake and transport in the steels are reviewed. Among the methods, electrochemical permeation technique utilized widely for evaluating the hydrogen diffusion and trapping behavior in metals and alloys is mainly discussed. Moreover, a modified permeation technique accommodating the externally applied load and its application to a variety of steels are intensively explored. Indeed, successful utilization of the modified permeation technique equipped with a constant load testing device leads to significant academic progress on the hydrogen assisted cracking (HAC) phenomenon of the steels. In order to show how the external and/or residual stress affects mechanical instability of steel due to hydrogen ingress, the relationship among the microstructure, hydrogen permeation, and HAC susceptibility is briefly introduced.

• Transactions of Materials Processing
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• v.6 no.2
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• pp.110-117
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• 1997

Sticking behavior under the hot rolling conditions for ferritic stainless steels have been studied. Sticking, which is a phenomenon that the naked metal exposed to the surface by scale breakaway during hot rolling sticks to the roll surface, was affected by both high temperature tensile strength and oxidation resistance of the steels. A steel having higher tensile strength and lower oxidation resistance exhibits better resistance to the sticking. It is due to that higher tensile strength increases localized deformation resistance and lower oxidation resistance creates lower friction between steel and roll by forming thicker scale as a lubricant during hot rolling. So, the sticking tends to occur more severely in the order of 430J1L, 436L, 430 and 409L. The most sensitive temperature to the sticking was found to be 90$0^{\circ}C$ for all grade of steels. It was also found that the high speed steel(HSS) roll compared to the Hi-Cr roll was more beneficial to prevent sticking. Because higher surface hardness of HSS roll compared to that of Hi-Cr roll provides less nucleation sites for sticking such as scratch on the roll surface.

• Transactions of Materials Processing
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• v.30 no.4
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• pp.165-171
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• 2021

This study was conducted on the manufacturing method of high-strength aluminum bolts. We obtained the displacement-load information by tensile test of the Al 6056 raw material and the T6 heat-treated material and calculated the precise flow stress and fracture limit using repetitive finite element analysis for before and after heat treatment. We designed a multi-stage forging process for T6 heat-treated material, and calculated that the accumulated damage value does not exceed fracture limits by finite element method. We produced the prototype forgings without any harmful defects such as cracks and folding occurring. Bolts made of T6 heat treated material show 9.6%higher tensile strength than T6 heat treated material after wire drawing.

• International Journal of Concrete Structures and Materials
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• v.9 no.2
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• pp.219-239
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• 2015

This paper discusses the suitability of producing concrete with 100 % recycled aggregate to meet durability and strength requirements for different applications. Aggregate strength, gradation, absorption, specific gravity, shape and texture are some of the physical and mechanical characteristics that contribute to the strength and durability of concrete. In general, the quality of recycled aggregate depends on the loading and exposure conditions of the demolished structures. Therefore, the experimental program was focused on the evaluation of physical and mechanical properties of the recycled aggregate over a period of 6 months. In addition, concrete properties produced with fine and coarse recycled aggregate were evaluated. Several concrete mixes were prepared with 100 % recycled aggregates and the results were compared to that of a control mix. SEM was conducted to examine the microstructure of selected mixes. The results showed that concrete with acceptable strength and durability could be produced if high packing density is achieved.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.2
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• pp.47-56
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• 2015

At the present, the mechanized form roads pavement was constructed with plain concrete. Mostly, it was used by welded wire mesh for preventing crack. Cellulose fibers for the reinforcement of concrete offer relatively high levels of elastic modulus, fiber count (per unit weight), specific surface, and bond strength to cement-based materials. The construction of concrete pavement confirmed that cellulose fiber reinforced concrete was applicable to mechanized form roads pavement. In the study, cellulose fibers were used here at 0.08 % volume fraction, which is equivalent to a fiber content of $1.2kg/m^3$. Cellulose fiber reinforced concrete were compared with plain concrete. Field test results indicated that cellulose fiber reinforced concrete showed slightly to increase of 28 days compressive strength and improved the initial strength. it tended to increase of splitting tensile strength. Test results showed that the slump and air content tend to decreased. but, the variation of air contends is very little. Also, construction cost of cellulose fiber reinforced concrete is less than about 25.7 % the case of welded wire mesh previously used. Therefore, The cost reduction is expected to be possible in construction site by mechanized form roads pavement.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.257-269
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• 2016

Early-strength-concrete (ESC) made of Type I cement with a high Blaine value of $500m^2/kg$ reaches approximately 60 % of its compressive strength in 1 day at ambient temperature. Based on the 210 compressive test results, a generalized rateconstant material model was presented to predict the development of compressive strengths of ESC at different equivalent ages (9, 12, 18, 24, 36, 100 and 168 h) and maximum temperatures (20, 30, 40, 50 and $60^{\circ}C$) for design compressive strengths of 30, 40 and 50 MPa. The developed material model was used to find optimum curing regimes for precast prestressed members with ESC. The results indicated that depending on design compressive strength, conservatively 25-40 % savings could be realized for a total curing duration of 18 h with the maximum temperature of $60^{\circ}C$, compared with those observed in a typical curing regime for concrete with Type I cement.

• Journal of Power System Engineering
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• v.8 no.4
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• pp.31-37
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• 2004

The damping capacity and strength of Fe-2Al-26Mn alloys have been studied for the development of new materials with high strength and damping capacity. Particularly, the effect of ${\alpha}'\;and\;{\varepsilon}$ martensite phase, which constitutes the microstructure of cold rolled Fe-Al-Mn alloys, has been investigated in terms of the strength and damping capacity of the alloys. The damping capacity rises with increasing the degree of cold rolling and reveals the maximum value at 25% reduction. The damping capacity is strongly affected by the volume fraction of ${\varepsilon}$ martensite, while the other phases, such as ${\alpha}'$ martensite and austenite phase, actually exhibit little effect on damping capacity. Considering that tensile strength increases and elongation decreases with increasing the volume fraction of ${\alpha}'$ martensite, it is proved that tensile strength is mainly affected by the amount of ${\alpha}'$ martensite.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.3
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• pp.35-44
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• 1985

This research explored the effects of abrasion, laundering, and abrasion/laundering interaction upon wear of 15 durable nonwoven fabrics. Wear was measured in terms of changes in tensile strength and stiffness. The test materials consisted of nine different dry-laid commercial interfacing fabrics of various fiber contents and six spunbonded poyester and polypropylene fabrics. Three fixed levels of abrasion and four fixed levels of laundering made up the 3$\times$4 factorial analysis used for the experiment and the analysis of variance. Findings revealed that abrasion had a greater effect than laundering on strength and stiffness of the tested fabrics. Laundering seemed related to the particular fibers used and to the fixation quality of fiber bonds. Spunbonded webs performed better than dry-laid webs in retaining tensile strength Stiffness change occurred more readily than strength change. Lighter, flexible, stretchable fabrics seemed less easily abraded than heavier, stiff, less stretchable fabrics. The interfacing fabrics of 70/20/$10\%$ nylon/polyester/rayon blends with high crosswise stretchability effectively resisted wear caused by abrasion and laundering. Further research is recommended to study the effects of longer abrasion periods and additional laundering cycles o,1 wear qualities of nonwoven fabrics. Additional factors such as amount and fixation methods of bonding agents, the effect of shear distortion, seam construction, and drycleaning solvents could also be studied.

• Journal of Surface Science and Engineering
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• v.32 no.6
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• pp.709-716
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• 1999

Ceramic is select for an alternative substrate material for high-speed circuits due to its low-thermal expansion. As, in this study, ceramic was prepared by ISG (interlayer sol-gel) process using metal salts and a metal alkoxide as the starting materials. Generally ceramic substrate is used electroless copper plating for the metallization. But it has been indicate weakely the adhesion strength between the substrate and copper layer. Therefore, this research, using the ISG process on the preparation of homogeneous and possible preparation at law temperature fabricated sol solution. Using of the dip coating method was coated for the purpose of giving the anchoring effect on the coating layer and enhancing the adhesion strength between the $Al_2$O$_3$ substrate and copper layer. This study examined primary the characteristic of the sol making condition and differential thermal analysis (DTA) X-ray diffraction (XRD) were mearsured to identify the crystal phase of heat treatment specimens. The morphology of the coated films were studied by scanning electron microscopy(SEM). As a resurt, XRD analysis was obtained patterns of $\alpha$-cordierite after heat-treatment about 2 hours at $1000^{\circ}C$. SEM analysis could have seen a large number of voids on coated film. The more contants of$ Al_2$$O_3$ Wt% was increased the more voids was advanced. Peel adhesion strength has a maximum in the contants of the TEOS:ANE of 1:0.7 mole%. In this case, adhesion strength has been measured 1150gf, peel adhesion strength were about 10 times more than uncoated of the ceramics film.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.154-159
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• 2010

Recent concrete structures have been being constructed with higher strength concrete than normal strength concrete. Therefore, it is necessary to review the applicabilities of current design codes and models for the prediction of mechanical behaviors of concrete materials such as creep. To investigate the applicability of creep model with the consideration of the strength level of concrete, three current models (ACI 209R, CEB-FIP MC90 and EC2) were studied and compared with series of experimental results. It was shown that EC2 model which is the updated model of CEB-FIP MC90 better predicts creep coefficient for high strength level concretes and showed relatively good agreements with experimental data.