• Journal of the Korean Wood Science and Technology
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• v.50 no.4
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• pp.237-245
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• 2022

This study examined the structural performance of experimental parallel strand lumber (PSL) from a Larch veneer strand. The prototype of PSL from a Larch veneer strand was manufactured in the experimental laboratory and tested. The bending and dowel bearing strength were determined from the modulus of elasticity (MOE), modulus of rupture (MOR), and dowel bearing strength based on a 5% offset yield load. The test results indicated that the average MOR of PSL was higher than that of 2 × 4 dimension lumber, and the average MOE of PSL was lower than that of 2 × 4 dimension lumber. A linear relationship was observed between the MOR and MOE. The allowable bending stress of PSL was derived as specified in ASTM D2915 and compared with other research. The dowel bearing strength of PSL in parallel to the grain was approximately double that perpendicular to the grain of PSL. A comparison of several theoretical calculations based on each national code for the dowel bearing strength was conducted, and some theoretical equations produced results closer to the experimental results when it was parallel to the grain, but the difference was higher in the case perpendicular to the grain. The test results showed that PSL made with Japanese larch veneer strands appeared to be suitable for a raw material of structural composite lumber (SCL) appeared to be used as a raw material for SCL.

• Journal of the Korean Ceramic Society
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• v.13 no.1
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• pp.35-44
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• 1976

The effect of quartz which exists in clays, especially in kaolin used for the production of chamotte sagger, on the strength of refractory was examined. In this study, a mixture of chamotte 50%, kaolin 25%, plastic clay 25% in ternary component system was selected as a batch composition. To this mixture 1%, 3% and 5% of feldspar and sericite were added respectively. The plastic clay used here was separated under 170 mesh by dry process. Feldspar and sericite were separated under 325 mesh by dry process. Feldspar and sericite were separated under 325 mesh by dry process. In order to change the particle size and the content of quartz, the kaolin was separated under 60, 115, 170 and 325 mesh by wet process, substituted quartz for coarse parts of it. Chamotte was classified into three grades, coarse (5-10mesh): medium (10-20mesh): fine(20-115mesh) and the ratio was 1:1:1. Samples were formed in 0.8xIx10cm size with 12.5% water at 160kg/$\textrm{cm}^2$ pressure, and fired at 130$0^{\circ}C$ for 1 hr. The fired samples were ivnestigated by means of x-ray diffraction analysis and microscopic observation, and the physical properties of them were also examined, such as firing shrinkage, apparent specific gravity and bulk specific gravity, apparent porosity, water absorption and modulus of rupture. The obtained results are as follows: 1. When screened kaolin with low content of quartz was added to fixed chamotte-plastic clay system, the sample lowered modulus of rupture and increased apparent porosity as the size of kaolin became finer. 2. When kaolin under 325 mesh with 7.2-15.81% quartz between 60-325 mesh was added to fixed chamotte-plastic clay system, the sample had higher apparent porosity and lower modulus of ruputure as the size and the amount of quartz became larger. 3. The addition of feldspar and sericite to chamotte-plastic clay system improved apparent porosity and modulus of rupture. The effect of feldspar was better when quartz content was low, although that of sericite was better than quartz content was high.

• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.20-27
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• 1994

Water repellent preservative (WRP) treated and untreated, small-sized specimens prepared from semiwater resistant, water resistant, and tegofilm-overlaid plywood were exposed to outdoor weathering for one year. Exterior durability of specimens was evaluated on the basis of changes in dynamic modulus of elasticity, degree of delamination, modulus of elasticity, modulus of rupture, and glueline shear strength. Among untreated specimens, tegofilm-overlaid plywood showed the best outdoor durability, and durability between semiwater resistant and water resistant plywood was similar. Although WRP treatment increased the durability of all types of plywoods, the effect of treatment on the increase in durability for semi water resistant plywood was not distinct. Accordingly, it can be concluded that semi water resistant plywood, which is used for temporary construction such as concrete formwork in our country, can not be inadequate for exterior use, regardless of WRP treatment. The bending strength and glueline shear strength of untreated water resistant plywood measured after weathering for one year did not exceed the minimum value specified by Korean Standard (KS), thereby the outdoor use of water resistant plywood was not desirable without WRP treatment. Exterior durability between treated water resistant plywood and untreated tegofilm-overlaid plywood was very similar. This result suggests that if an exposed plywood surface is treated with WRP regularly water resistant plywood can be used for temporary construction. This suggestion, however, needs to be investigated. In summary, semiwater resistant plywood cannot be used for temporay construction regardless of WRP treatment. Water resistant plywood can be used only with WRP treatment. Comparing the cost of tegofilm-overlaid plywood to costs of water resistant plywood and WRP treatment, however, it can be concluded that use of tegofilm-overlaid plywood for temporay constrution is strongly suggested from the point of view of both outdoor durability and costs.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.105-113
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• 2016

Most studies on mechanical properties of concrete with recycled aggregate was focused on the concrete with compressive strength of less than 40 MPa. Therefore, this paper concerns the compressive strength and mechanical properties of concrete with compressive strength of greater than 40 MPa containing recycled coarse aggregate (RCA). The experimental parameters were compressive strength level and replacement ratio of RCA. Compressive strength level was 45 and 60 MPa, and replacement ratio of RCA was 30, 50, 70 and 100%. The results of the test were discussed: compressive strength, elastic modulus, split tensile strength and modulus of rupture. Test results of elastic modulus were compared to the design code predictions. The design code predictions for elastic modulus overestimated the experimental results. However, the design code predictions for modulus of rupture were generally in agreement with the measured values.

• Journal of Biosystems Engineering
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• v.28 no.3
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• pp.239-244
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• 2003

The potential use of ultrasonic technique for firmness measurement of apples was evaluated. Mechanical properties(bioyield deformation, bioyield strength, rupture deformation, ultimate strength, and elastic modulus) and ultrasonic parameters (ultrasonic velocity, attenuation coefficient and the first peak frequency) of the apple flesh during the storage time were measured and analyzed. Ultrasonic parameters were determined from the measurement of ultrasonic wave transmission through the apple flesh specimen. Mechanical properties were obtained by universal testing machine. The bioyield strength, rupture strength, elastic modulus, ultrasonic velocity, and the first peak frequency of the apple flesh decreased with the storage time. The bioyield deformation, rupture deformation, and ultrasonic attenuation coefficient increased with the storage time. The correlation analysis between ultrasonic parameters and mechanical properties and the storage time was performed. The high correlations were found between the storage time and the ultrasonic parameters, and these relationships seem to be useful for determining the firmness of the apple flesh.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.49-59
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• 2016

According to KS and Standard Specifications for Concrete, the compressive strength of concrete containing recycled aggregate is limited to 27 MPa and thereafter there are little research on concrete containing recycled aggregate of its compressive strength of greater than 27 MPa. Therefore, to expand the applicability of concrete recycled coarse aggregate(RCA), this paper concerns the mechanical properties of concrete containing RCA with compressive strength ranging from 30 to 60 MPa. The experimental parameters were water-cement ratio and replacement ratio of RCA. Water-cement ratio(w/c) was 0.36, 0.46 and 0.53, and replacement ratio of RCA was 30, 50, 70 and 100%. The experimental results were discussed about compressive strength, elastic modulus, split tensile strength and modulus of rupture. Test results of elastic modulus were compared to the design code predictions. Experimental elastic modulus for concrete with w/c=0.53 decreased by greater than 10% compared with that for concrete with w/c=0.36. The design code predictions for elastic modulus overestimated the experimental results. Whereas, the design code predictions for modulus of rupture underestimated the measured values.

• Journal of the Korean institute of surface engineering
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• v.27 no.1
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• pp.29-35
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• 1994

The effects of coating of 3$\mu\textrm{m}$ thickness on the mechanical property of alumina after heat treatment at 100$0^{\circ}C$ for 30minutes under $10^{-6}$torr vacuum was quantified in terms of modulus of rupture(MOR) using Weibull plot. While the copper coating did not change MOR of alumina due to the nonwetting behavior of Cu on $Al_2O_3$, the reactive titanium metal coating caused a noticeable 29% reduction in averaged MOr strength. This was related with the combined effects of microcracks in coating formed during heat treatment and good bonding character between Ti and $Al_2O_3$. The effect of cosputtering of Ti and Cu, bilayer coatings of Cu/Ti and Ti/Cu were also investigated. It was found that Ti, cosputtered, Cu/ti and Ti/Cu coatings reduced MOR strength of alumina in the order listed. This was correlated with the amount of Ti at coating/alumina inter-face associated with a coated layer or segregation of Ti during heat treatment.

• Journal of the Korean Wood Science and Technology
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• v.41 no.5
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• pp.392-398
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• 2013

This study investigated the effect of test zone selection for evaluating bending strength of visually graded lumber. This will contribute to the understanding of two different methods under different standards. In method I, the major defect was randomly placed in the test specimen. In method II, the major defect was randomly placed in the maximum moment zone (MMZ). The results showed that the method II is more accurate for reflecting the effect of defects governing the grade of lumber. Unless the maximum strength-reducing defect (MSRD) is placed in MMZ, the evaluated value would be higher than that of MSRD. For evaluating the modulus of rupture (MOR) of visually graded lumber in test set-up of Method I, the Eq. (5) needs to be considered.

• Journal of the Korean Ceramic Society
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• v.21 no.1
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• pp.51-59
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• 1984

In this paper mechanical properties of reaction-bonded silicon nitride are studied with the variation of initial nitrogen partial pressure. At 1, 25$0^{\circ}C$ the amount of nitridation and the nucleation of nitride increase linearly with the nitrogen partial pressure increase. After the nitridation is completed the density of nitride and modulus of rupture at room temperature are increased with the amount of nitridation. When the partial pressure of nitrogen is 0.5 atm the specimen show the optimum properties that is the highest density of nitride and modulus of rupture. Also the microstructure of $\alpha$-matte is deveoped very well at that pressure of nitrogen which contributes to the strength development of specimen. It is shown that with proper control of initial partial pressure of nitrogen high strength silicon nitride body can be manufactured for dynamic applications.

• Computers and Concrete
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• v.19 no.6
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• pp.667-675
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• 2017

One of the main disadvantages of Ultra High Performance Concrete exists in the large suggested value of UHPC ingredients. The purpose of this study was to find the models mechanical properties which included a 7, 14 and 28-day compressive strength test, a 28-day splitting tensile and modulus of rupture test for Ultra High Performance Concrete, as well as, a study on the interaction and correlation of five variables that includes silica fume amount (SF), cement 42.5 amount, steel fiber amount, superplasticizer amount (SP), and w/c mechanical properties of UHPC. The response surface methodology was analyzed between the variables and responses. The relationships and mathematical models in terms of coded variables were established by ANOVA. The validity of models were checked by experimental values. The offered models are valid for mixes with the fraction proportion of fine aggregate as; 0.70-1.30 cement amount, 0.15-0.30 silica fume, 0.04-0.08 superplasticizer, 0.10-0.20 steel fiber, and 0.18-0.32 water binder ratio.