• 한국생산제조학회지
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• 제7권5호
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• pp.120-126
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• 1998

Second step shot peening was applied on both smooth specimen and U-notch specimen in order to investigate the stress distribution and the improvement in fatigue strength. Various experiments and measurements such as rotary bending fatigue test and the measurement of compressive residual stress were performed. The results showed that the fatigue strength of second step shot peened specimens increased by 34 percent compared to that of unpeened ones. Compressive residual stress also considerably increased, which resulted in the increase of fatigue strength. finite element analysis showed that shot peening is effective in decreasing the bending stress by external force. The effectiveness of shot peening in reducing the compressive residual stress was anticipated by the superposition of the concentrated stress and the compressive residual stress.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.367-372
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• 2003

Fiber Reinforced Cementitious Composite, DFRCC has strain hardening property with multiple crack in failed of compressive, tensile, bending force, concrete is not so that. But DFRCC could not use to the building element for which has not structural stiffness only has ductile property. DFRCC is used for repair only in recently. In that reason, we considered the concrete of light weight concrete, porous concrete, mortar complex with DFRCC. and DFRCC reinforced by fiber net, steel bar. In this study, results of experiment on complex method of concrete and DFRC were shown as follows; The complex methods of concrete lay on DFRCC, sandwich layer composition were effective for bending force depending on section size each layer, and reinforce DFRCC by fiber net, steel bar was effective method also.

• 대한치과기공학회지
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• 제33권4호
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• pp.331-337
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• 2011

Purpose: The purpose of this study was to impact of force system change in finger spring that add helical coil one round on orthodontic force. Methods: The following conclusions were drawn from the experiment conducted after bending 90 samples with a CNC wire forming machine while changing the height and lumen size to 1mm - 3mm - 5mm and 2mm - 3mm - 4mm respectively in the coil of the force system in finger spring added with one wheel of helical coil of 18-8 stainless steel round wire (${\Phi}0.5mm$, spring hard) from Jinsung Co. in domestic market under the following conditions: Laboratory name = Instron 5942; Temperature($deg^{\circ}C$) = 18.00; Humidity(%) = 50.00; Rate 1 = 10.00000 mm/min; Compressive extension = 5.0mm. Results: When Coil height is 1, 3, 5mm and lumen size is 2, 3, 4mm reduce finger spring as mean value of compressive extension occasion maximum load(mN) increases as coil height rises, and lumen size grows to 5.0mm. And was expose that compressive load(mN) increases as coil position of finger spring rises and increase as lumen size is decrescent. Conclusion: As the adherence height of coil was raised from 1mm through 3mm to 5mm, compressive load increased. As the lumen size increased from 2mm through 3mm to 4mm, compressive load decreased. Therefore, these results suggest that it is desirable to lower the coil height and enlarge the lumen size to enhance the biomechanical efficiency of finger spring when manufacturing the finger spring for removable orthodontic devices.

• 콘크리트학회논문집
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• 제12권5호
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• pp.121-130
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• 2000

Currently, in evaluating a flexural strength of a concrete member, the effect of specimen depth has not been systematically studied, even though its effect on ultimate strength of a section is very important. For all types of loading conditions, the trend is that the strength of a member tends to decrease when the member depth increases. In this study, the influence of specimen depth on flexural compressive strength of concrete member was examined experimentally. A series of C-shaped specimens subjected to axial compressive force and bending moment were tested using three geometrically similar specimens with different length-to depth ratios (h/c = 1, 2 and 4) which have compressive strength of 55 MPa. The results indicate that the flexural compressive strength decreased as the specimen depth increased. A model equation was derived based on regression analyses of the experimental data. Also, the results show that ultimate strain decreases as the specimen depth increases. Finally, a general model equation for the depth effect is proposed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1083-1088
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• 2004

This paper deals with the vibration and stability of a circular cylindrical shaft, modeled as a tapered thin-walled composite beam and spinning with constant angular speed about its longitudinal axis, and subjected to an axial compressive force. Hamilton's principle and the assumed mode method are employed to derive the governing equations of motion. The resulting eigenvalue problem is analyzed, and the stability boundaries are presented for selected taper ratios and axial compressive force combinations. Taking into account the directionality property of fiber reinforced composite materials, it is shown that for a shaft featuring flapwise-chordwise-bending coupling, a dramatic enhancement of both the vibration and stability behavior can be reached. It is found that by the structural tailoring and tapering, bending natural frequencies, stiffness and stability region can be significantly increased over those of uniform shafts made of the same material. In addition, the particular case of a classical beam with internal damping effect is also included.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.115-120
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• 2000

Currently, in evaluating a flexural strength of a concrete member, the effect of specimen depth has not been systematically studied, even though its effect on ultimate strength of a section is very important. For all types of loading conditions, the trend is that the strength of a member tends to decrease when the member depth increases. In this study, the influence of specimen depth on flexural compressive strength of concrete member was examined experimentally. A series of C-shaped specimens subjected to axial compressive force and bending moment were tested using three geometrically similar specimens with different length-to-depth ratios(h/c=1, 2 and 4) which have compressive strength of 55MPa. The results indicate that the flexural compressive strength decreased as the specimen depth increased. A model equation was derived based on regression analyses of the experimental data. Also the results show that ultimate strain decreases as the specimen depth increases. Finally, a general model equation for the depth effect is proposed.

• 농업과학연구
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• 제14권1호
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• pp.98-133
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• 1987

The mechanical and rheological properties of agricultural materials are important for engineering design and analysis of their mechanical harvesting, handling, transporting and processing systems. Agricultural materials, which composed of structural members and fluids do not react in a purely elastic manner, and their response when subjected to stress and strain is a combination of elastic and viscous behavior so called viscoelastic behavior. Many researchers have conducted studies on the mechanical and rheological properties of the various agricultural products, but a few researcher has studied those properties of rice plant, and also those data are available only for foreign varieties of rice plant. This study are conducted to experimentally determine the mechanical and the rheological properties such as axial compressive strength, tensile strength, bending and shear strength, stress relaxation and creep behavior of rice stems, and grain detachment strength. The rheological models for the rice stem were developed from the test data. The shearing characteristics were examined at some different levels of portion, cross-sectional area, moisture content of rice stem and shearing angle. The results obtained from this study were summarized as follows 1. The mechanical properties of the stems of the J aponica types were greater than those of the Indica ${\times}$ Japonica hybrid in compression, tension, bendingand shearing. 2. The mean value of the compressive force was 80.5 N in the Japonica types and 55.5 N in the Indica ${\times}$ Japonica hybrid which was about 70 percent to that of the Japonica types, and then the value increased progressively at the lower portion of the stems generally. 3. The average tensile force was about 226.6 N in the Japonica types and 123.6 N in the Indica ${\times}$ Japonica hybrid which was about 55 percent to that of the Japonica types. 4. The bending moment was $0.19N{\cdot}m$ in the Japonica types and $0.13N{\cdot}m$ in the Indica ${\times}$ Japonica hybrid which was 68 percent to that of the Japonica types and the bending strength was 7.7 MPa in the Japonica types and 6.5 MPa in the Indica ${\times}$ Japonica hybrid respectively. 5. The shearing force was 141.1 N in Jinju, the Japonica type and 101.4 N in Taebaeg, the Indica ${\times}$ Japonica hybrid which was 72 percent to that of Jinju, and the shearing strength of Taebaeg was 63 percent to that of Jinju. 6. The shearing force and the shearing energy along the stem portion in Jinju increased progressively together at the lower portions, meanwhile in Taebaeg the shearing force showed the maximum value at the intermediate portion and the shearing energy was the greatest at the portion of 21 cm from the ground level, and also the shearing strength and the shearing energy per unit cross-sectional area of the stem were the greater values at the intermediate portion than at any other portions. 7. The shearing force and the shearing energy increased with increase of the cross-sectional area of the rice stem and with decrease of the shearing angie from $90^{\circ}$ to $50^{\circ}$. 8. The shearing forces showed the minimum values of 110 N at Jinju and of 60 N at Taebaeg, the shearing energy at the moisture content decreased about 15 percent point from initial moisture content showed value of 50 mJ in Jinju and of 30 mJ in Taebaeg, respectively. 9. The stress relaxation behavior could be described by the generalized Maxwell model and also the compression creep behavior by Burger's model, respectively in the rice stem. 10. With increase of loading rate, the stress relaxation intensity increased, meanwhile the relaxation time and residual stress decreased. 11. In the compression creep test, the logarithmic creep occured at the stress less than 2.0 MPa and the steady-state creep at the stress larger than 2.0 MPa. 12. The stress level had not a significant effect on the relaxation time, while the relaxation intensity and residual stress increased with increase of the stress level. 13. In the compression creep test of the rice stem, the instantaneous elastic modulus of Burger's model showed the range of 60 to 80 MPa and the viscosities of the free dashpot were very large numerical value which was well explained that the rice stem was viscoelastic material. 14. The tensile detachment forces were about 1.7 to 2.3 N in the Japonica types while about 1.0 to 1.3 N in Indica ${\times}$ Japonica hybrid corresponding to 58 percent of Japonica types, and the bending detachment forces were about 0.6 to 1.1 N corresponding to 30 to 50 percent of the tensile detachment forces, and the bending detachment of the Indica ${\times}$ Japonica hybrid was 0.1 to 0.3 N which was 7 to 21 percent of Japonica types. 15. The detachment force of the lower portion was little bigger than that of the upper portion in a penicle and was not significantly affected by the harvesting period from September 28 to October 20. 16. The tensile and bending detachment forces decreased with decrease of the moisture content from 23 to 13 percent (w.b.) by the natural drying, and the decreasing rate of detachment forces along the moisture content was the greater in the bending detachment force than the tensile detachment force.

• 소성∙가공
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• 제8권4호
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• pp.347-355
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• 1999

The paper is concerned with an improved scheme for application of the blank holding force in order to take account of the thickness distribution in the sheet material of the flange region. The scheme incorporates with a modified membrane finite element method for planar anisotropic materials. The new scheme proposed two coefficients α and βto calculate the compressive stress in the sheet metal due to the blank holding force, which should be determined properly for accurate analysis. The effect of αand βon the blank holding force distribution and the deformed shape is investigated with simulation of rectangular cup deep drawing processes by changing parameter values.

• 농업과학연구
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• 제9권2호
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• pp.569-575
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• 1982

수확기간(收穫期間)에 있어서 벼줄기의 물리적(物理的) 및 기계적(機械的) 특성(特性)을 구명(究明)하고져 일반계(一般系) 품종(品種)인 이리(裡里)348 및 진주(晋州)벼와 통일계(統一系) 품종(品種)인 서광벼 및 태백(太白)벼 4개(個) 품종(品種)을 표준시비구(標準施肥區)에서 선정(選定)하여 압축(壓縮), 인장(引張), 굽힘 시험(試驗)을 실시(實施)하고, 이어서 진주(晋州)벼 및 태백(太白)벼에 대(對)하여 부위별(部位別), 전단각도(剪斷角度) 및 함수율(含水率) 변화(變化)에 따른 전단하중(剪斷荷重)-변형특성(變形特性), 전단력(剪斷力) 및 전단(剪斷) energy등(等) 전단특성(剪斷特性)을 측정(測定) 분석(分析)한 결과(結果)는 다음과 같다. 1. 압축(壓縮), 굽힘, 인장(引張) 및 전단력(剪斷力)은 통일계품종(統一系品種)에 비(比)하여 일반계(一般系) 품종(品種)이 컸다. 2. 전(全) 부위별(部位別)의 전단력(剪斷力) 추세는 진주(晋州)벼에 있어서 하부위(下部位)의 큰 값이 상부위(上部位)로 갈수록 감소(減少)하였고, 태백(太白)벼에 있어서는 하부위(下部位)부터 지상(地上) 21cm까지 비교적 일정(一定)한 큰 값으로 나타냈다. 3. 전단면적(剪斷面積)의 증가(增加)에 따라 전단력(剪斷力) 및 전단(剪斷) energy는 증가(增加)하였고, 그 증가율(增加率)은 전단면적(剪斷面積) $10mm^2$까지는 컸으나 그 이상(以上)에서는 매우 둔화(鈍化)되었다. 4. 예취(刈取) 직후(直後)에 있어서 함수율(含水率)의 감소(減少)에 따른 전단력(剪斷力) 및 전단(剪斷)energy의 감소(減少)는 컸으나 함수율(含水率) 60%(w.b)부터는 큰 변화(變化)가 없었다.

• Steel and Composite Structures
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• 제35권4호
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• pp.495-508
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• 2020

Double skin composite walls are alternatives to concrete walls to resist gravity load in structures. The composite action between steel faceplates and concrete core largely depends on the internal mechanical connectors. This paper investigates the structural behavior of novel composite wall system with T section and under combined compressive force and bending moment. The truss connectors are used to bond the steel faceplates to concrete core. Four short specimens were designed and tested under eccentric compression. The influences of the thickness of steel faceplates, the truss spacing, and the thickness of web wall were discussed based on the test results. The N-M interaction curves by AISC 360, Eurocode 4, and CECS 159 were compared with the test data. It was found that AISC 360 provided the most reasonable predictions.