• 한국추진공학회지
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• 제1권2호
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• pp.91-102
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• 1997

점화기의 성능에 미치는 노화의 영향을 알아보기 위하여 12년, 15년, 16년 경과된 활성 모타로부터 점화기를 분해하여 점화제의 특성 값을 측정하고 점화기의 연소 시험을 하였다. 점화제인 B/$KNO_3$ 펠렛의 수분 함량, 외형 치수, 분쇄 강도, 열 분해 특성, 발열량 등을 측정한 결과, 노화 기간에 비례하여 분쇄 강도는 다소 증가하였고 발열량은 감소하였으나 그 외의 특성 값들은 변화가 없었다. 밀폐 용기 시험과 비활성 모타 연소 시험 결과, 노화된 점화제의 연소 속도는 약 10% 증가하였고, P-t 곡선의 압력을 적분한 값 $P_t$는 약 15% 감소하였다. 연소 속도는 점화제에 균열이 발생할 경우 증가하고 $P_t$는 폭발 열량에 비례하여 감소함을 추론할 수 있었다.

• 펄프종이기술
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• 제30권1호
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• pp.29-43
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• 1998

This study was to investigate the effect of .compressive load and cyclic humidity(2$0^{\circ}C$, 65% and 90% RH) on the physical and mechanical properties of corrugated board. Corrugated boards in the study were under compressive load and under cyclic humidity, and their properties were compared to those without load. Results were summarized as follows ; 1 Statistically significant correlation was shown between the ring crush of the boards and the compressive strength of cylinder specimen made from the boards. So we could study the compressive behavior of board with cylinder specimen. 2. The boards under the compressive load increased their moisture content and thickness much more than those without load both in constant and in cyclic RH. 3. The compressive and tensile strength of board samples were inversely and closely proportional to the sheet moisture content regardless of their load and humidity history. 4. The moisture content did not show any significant proportionality to the change of burst strength of boards within this experiment. 5. Board reconditioning in standard condition led to the recovery of the strength loss that had occurred under various load and humidity condition. 6. The handsheets prepared from the boards that had experienced compressive load and cyclic humidity, and those with no-load and 65% RH did not show any significant difference in strength properties. No physical damage or load-carrying properties of the wood fiber were observed by the compressive load and cyclic humidity history.

• Geomechanics and Engineering
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• 제35권2호
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• pp.209-219
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• 2023

This paper presents numerical investigations into the particle crushing effect on the shear properties of gravel under direct shear condition. A novel particle crushing model was developed based on the octahedral shear stress criterion and fragment replacement method. A series of direct shear tests were carried out on unbreakable particles and breakable particles with different strengths. The evolutions of the particle crushing, shear strength, volumetric strain behavior, and contact force fabric during shearing were analyzed. It was observed that the number of crushed particles increased with the increase of the shear displacement and axial pressure and decreased with the particle strength increasing. Moreover, the shear strength and volume dilatancy were obviously decreased with particle crushing. The shear displacement of particles starting to crush was close to that corresponding to the peak shear stress got. Besides, the shear-hardening behavior was obviously affected by the number of crushed particles. A microanalysis showed that due to particle crushing, the contact forces and anisotropy decreased. The mechanism of the particle crushing effect on the shear strength was further clarified in terms of the particle friction and interlock.

• 한국포장학회지
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• 제7권1호
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• pp.9-15
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• 2001

Top-to-bottom compression strength of corrugated fiberboard boxes is partly dependent on the load-carrying ability of the central panel areas. The ability of these central areas to resist bending under load will increase the stacking strength of the box. The difference of box compression strengths, among boxes which are made with identical dimensions and fabricated with same components but different flute sizes, is primarily due to difference of the flexural stiffness of the box panels. Top-to-bottom compression strength of a box is accurately predicted by flexural stiffness measurements and the edge crush test of the combined boards. This study was carried out to analyze the flexural stiffness, maximum bending force and maximum deflection for various corrugated fiberboards by experimental investigation. There were significant differences between the machine direction (MD) and the cross-machine direction (CD) of corrugated fiberboards tested. It was about 50% in SW and DW, and $62%{\sim}74%$ in dual-medium corrugated fiberboards(e.g. DM, DMA and DMB), respectively. There were no significant differences of maximum deflection in machine direction among the tested fiberboards but, in cross direction, DM showed the highest value and followed by SW, DMA, DMB and DW in order. For the corrugated fiberboards tested, flexural stiffness in machine direction is about $29%{\sim}48%$ larger than cross direction, and difference of flexural stiffness between the two direction is the lowest in DMA and DMB.

• 펄프종이기술
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• 제34권1호
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• pp.46-53
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• 2002

This study was carried out to analyze the effects of preservation temperature and relative humidity to the physical properties of corrugated fiberboard boxes for fruit and vegetable packaging. The preservation temperature did not affect severely to physical properties of corrugated fiber-board. Relative humidity was a major cause of corrugated fiberboard box quality deterioration. The burst and compressive strengths of experimental boxes measured with Mullen high pressure tester and tong crush tester were decreased gradually as relative humidity increased from 55% to 75%. But, the strength properties slightly decreased relative humidity at 75% or higher. This tendency was the greater for single wall (SW) corrugated fiberboard box than that for double wall (DW). It is suggested that development of the water-resistant corrugated fiberboard and box be needed that can be used under the condition of low temperature and high moisture content, which are being employed in the cold chain system.

• 한국지반신소재학회논문집
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• 제9권4호
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• pp.67-73
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• 2010

보강토 옹벽에서 가장 중요한 것 중 하나는 양질의 뒷채움 재료를 구하는 것이다. 그러나 양질의 재료가 부족하여 부득히 부족한 토사대신 현장 유용토인 쇄석을 혼합하여 보강토 옹벽을 축조한 사례가 있었다. 따라서, 본 연구에서는 보강토옹벽의 뒷채움 재료로서 쇄석혼합토를 사용할 경우 혼합비에 따른 입도분포, 진단특성 및 인발특성에 대해서 각각 실험을 통하여 혼합비에 따른 특성변화들 검토하고자 하였다. 또한, 다양한 쇄석의 함유량에 대해 입도 선정기준에 적합한지 여부를 검토하였는데, 시험결과 입도19mm이하의 쇄석을 20%까지 혼합한 경우 뒷채움재료의 입도기준을 만족하였다. 전단강도정수 및 인발정수를 구하는 시험을 실시하였는데, 정수들은 쇄석함유량이 증가함에 따라서 증가하였다. 쇄석혼합토가 뒷채움재료로 사용될 경우 본 연구결과는 설계참고자료가 될 것으로 판단된다.

• 한국건축시공학회지
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• 제12권3호
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• pp.284-290
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• 2012

시멘트 입도계수(CFM)란 시멘트의 입자크기 분포를 정수로 표현하는 방법으로서 시멘트의 화학성분이나 광물조성은 변화시키지 않고, 시멘트 분쇄과정의 조정으로 CFM을 변화시킨다면 조강, 중용열 및 저열 등의 다양한 시멘트로의 접근이 가능할 것으로 추측된다. 따라서 본 연구에서는 CFM 변화를 활용한 특수 시멘트의 제조 가능성을 분석하기 위한 기초적 연구로서 CFM이 콘크리트의 기초적 특성에 미치는 영향에 대하여 검토하고자 하였다. 그 결과를 요약하면 굳지 않은 콘크리트의 배합특성으로 CFM이 커질수록 목표 유동성을 확보하기 위해 잔골재율 및 단위수량은 증가시켜 주어야 하고, AE제 및 SP제 사용량은 감소시켜 주어야 했다. 응결시간은 CFM이 커질수록 지연되었고, 압축강도는 초기재령에서는 상대적으로 낮았으나, 후기재령으로 갈수록 압축강도의 차이는 작아져 3년 정도가 되면 동등한 수준의 압축강도가 발현되었다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2003년도 하계 학술대회 논문집
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• pp.347-352
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• 2003

농산물 포장화물의 경우 농산물의 손상은 겉포장 상자의 파손에 의한 압상이 주요 원인이다. 따라서 농산물 상자의 경우 압축강도를 특히 중요시 여기고 있으며, 한국산업규격을 비롯해 각종 농산물 관련 규정에서는 압축강도에 의한 상자의 품질관리를 규정화 하고 있다. 골판지 상자의 압축강도는 원단인 골판지의 구성 원지들(라이너, 골심지)의 품질과 이들의 구성 형태 및 상자의 외형 치수 비율에 따라 결정되므로, 원지의 링크라쉬(ring crush), 원단의 수직압축강도(edgewise compression strength)를 통해 상자의 압출강도를 관리하는 것이 보통이다. 또한 골판지 상자는 제작 후 유통 과정을 거치면서, 여러 요인에 의해 압축강도가 현격하게 저하되는데, 이중 수분 흡습에 의한 강도저하와 장기 누적하중, 진동 및 충격 등의 피로로 인한 강도 저하가 가장 크다. 여러 산업 분야에서 골판지 상자의 견고성 문제는 물품의 내수 및 수출시 제품에 대한 신뢰성 확보와 기업의 이미지 제고와 직결되는 중요한 사항이다. 특히, 세계 각 국의 농산물 시장이 개방됨에 따라 우리나라 농산물의 수출도 확대될 전망이고 또한 마땅한 대체재가 개발되지 않는 한 골판지 상자의 이용은 날로 증가될 것으로 전망된다. 따라서 골판지 상자의 압축강도와 내구성 향상에 대한 다각적인 연구가 절실하다. (중략)

• 대한정형외과스포츠의학회지
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• 제7권1호
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• pp.8-14
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• 2008

Elbow joint injuries during exercise mostly occur by repeated stress to the joint than direct trauma. A pitcher who uses his arm above his head is most likely to be injured. So learning the right way to exercise and gaining the strength by maturating the body are essential for diminishing the chance of injury. On lateral ulnar tendon injury, which is most commonly injured area on elbow joint, pitchers generally complain of pain in arm movement above head and reduction of velocity, accuracy, and number of pitching. When there is pain on upper arm in harsh using, the stress fracture must be thought and epicondylar physis fracture of medial arm can occur by repeated abduction stress and contraction of flexors on forearm on children with immature skeleton. Osteochondritis dissecans of capitullum occur in young athletes who use there upper limb continuously lifting weights and gym work. And stress of abduction-extension includes damage of soft tissue and bone components, post medial crush syndrome, lateral ulnar ligament injury, extensor-abductor injury, stress of radius- capitullum are in this category.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.195-205
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• 2001

The mechanical properties of aluminum honeycomb on the direction of axial crushing under quasistatic loading test was investigated. The crushing process was simulated numerically by full-scale finite element models. Simulations reproduce the experimental results both qualitatively as well as quantitatively. From the investigation, we suggested the constitutive model of energy absorbing honeycomb structure for large scale impact analysis. Real impact test of the WB(Moving Deformable Barrier) was carried and compared with finite element simulation. Constitutive model used in the numerical simulation had a good correlation with experiment. By suggesting the optimizing method fur honeycomb cell configuration design, relationship between cell configuration and crush strength is studied.