• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1072-1076
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• 2017

고속 회전하는 로켓보조추진탄의 로켓 추진 유동특성을 수치해석적으로 연구하였다. 회전지상연소시험을 통해 연소실 내부 압력을 계측하였고 지상 조건, 작동 고도 조건, 기저부 압력 조건의 노즐압력비를 적용하여 수치해석을 수행하였다. 그리고 수치해석 결과를 등엔트로피 1차원 해와 지상회전시험 결과와 비교 하였다. 또한 동일 노즐압력비에서 유동의 회전 유/무에 따른 추력특성의 차이를 확인하였다.

• 품질경영학회지
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• 제49권3호
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• pp.255-268
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• 2021

Purpose: We sought to understand why a high-speed rotating projectile featuring a fuze-and-body assembly sometimes exhibited airburst, and we intended to improve the flight stability by eliminating airburst. Methods: We performed characteristic factor analysis, structural mechanics modeling, and dynamic modeling and simulation; and we scheduled firing tests to discover the cause of airburst. We used a step-by-step procedure to analyze the reliability function for selecting the bonding force standard that prevents airburst. Results: The 00MM high-speed rotating projectile features a fuze bonded to a body assembly; the bonding sometimes can break on firing. The resulting contact force, vibration and roll damping during flight generated yaw. Flight became unstable; fuze operation triggered an airburst. Our reliability test improved the bonding force standard (the force was increased). When the bonding force was at least the minimum required, a firing test revealed that airburst/flight instability disappeared. Conclusion: Analysis and identification of the causes of flight instability and airburst render military training safer and enhance combat power. Ammunition must perform as designed. Our method can be used to set standards that improve the performances of similar types of ammunition.

• 대한건축학회논문집:구조계
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• 제35권2호
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• pp.13-20
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• 2019

This study was conducted in order to validate the nose shape factors of projectile in existing impact formulas for high-strength concrete in the event of collision with high-speed projectiles. In order to conduct the high-speed impact experiment, specified concrete strengths of 35, 100, and 120 MPa were prepared and tested in collision with both conical and hemispherical projectiles. The results showed that the measured penetration depth did not decrease linearly as concrete strength increased. Comparing the ratio penetration depth to the kinetic energy of the conical and hemispherical projectiles, the difference in the ratios for high strength concrete was observed to decline as concrete strength increased. However, in the modified NDRC and the Hughes formulas, the difference in the predicted penetration depth of the conical and hemispherical projectiles was constant despite increasing concrete strength. The modified NDRC and Hughes formulas should be improved upon so as to be applied to high strength concrete.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.450-465
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• 2021

In this study, an attempt has been made to investigate the water-entry characteristics of the high-speed parallel projectile numerically. The shear stress transport k-𝜔 turbulence model and the Zwart-Gerber-Belamri cavitation model based on the Reynolds-Averaged Navier-Stokes method were used. The grid independent inspection and grid convergence index is carried out and verified. The influences of the parallel water-entry on flow filed characteristics, trajectory stability and drag reduction performance for different values of initial water-entry speed (𝜈₀ = 280 m/s, 340 m/s, 400 m/s) and clearance between the parallel projectiles (L_p = 0.5D, 1.0D, 2.0D, 3.0D) are presented and analyzed in detail. Under the condition of the parallel water-entry, it can be found that due to the intense interference between the parallel projectiles, the distribution of cavity is non-uniform and part of the projectile is exposed to water, resulting in the destruction of the cavity structure and the decline of trajectory stability. In addition, the parallel projectile suffers more severe lateral force that separates the two projectiles. The drag reduction performance is impacted and the velocity attenuation is accelerated as the clearance between the parallel projectiles reduces.

• 한국염색가공학회지
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• 제12권1호
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• pp.1-11
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• 2000

This paper surveys the fabric weavability and machine efficiency in the various weaving looms such as Projectile, Rapiers, and Air-jet. Used projectile loom was Sulzer-PU, and FAST-R, THEMA-11E, and Picanol-GTX were used for Rapier looms, as the Air-Jet looms, Picanol PAT and OMNI types were used. Using these looms, 5 harness worsted satin fabrics were woven for surveying the fabric weavability and machine efficiency. Warp yam count of fabric is 1/40Nm, Sirofil, and filling is 1/30 Nm, worsted. End breaks of warp and filling directions for the various types of looms are measured and discussed with the mechanism of each loom. Warp and filling yam tensions are also measured and analysed with open width of shedding motion of each weaving machine. And various warp yam tensions with open width of shedding are measured and analysed according to the warp yam in various heald frame. These results fire also discussed with temples such as bar and ring. Warp yam tensions at the various positions on the fabric with various looms are measured and discussed with fabric mechanical properties such as tensile, bending, shear and surface.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3455-3459
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• 2014

본 논문은 전자기 발사체에서 피투사체의 높은 발사력을 위한 코일건 설계 및 실험을 다루고 있다. 현재 코일건은 전자기 발사체에 적용하기 위해 많은 연구가 진행되고 있다. 코일건은 솔레노이드 형태의 코일에 전류 인가 시, 플레밍의 오른손 법칙에 의하여 발생하는 전자기력에 의해 피투사체를 추진시키는 원리이다. 피투사체의 발사력은 코일에 흐르는 전류가 생성하는 자기력과 비례한다. 전류는 코일의 수명에 영향을 미치므로 전류의 한계점이 존재한다. 따라서, 전류의 한계점을 초과하지 않고 피투사체가 받는 자기력이 최대가 되는 코일건의 설계가 요구된다. 이를 위해 먼저 코일건의 자속밀도, 자기력을 계산하고, Onderdonk's 식을 이용하여 코일의 전류 한계점을 찾는다. 솔레노이드를 설계하기 위해서 전류 한계점을 초과하지 않는 조건을 만족하며 코일건의 자기력을 최대로 가지는 권수를 알아낸다. 설계 결과에 따라 시제품을 제작하여 피투사체의 속도를 측정하기 위한 실험을 하였다. 발사된 피투사체는 CCD 카메라를 이용하여 촬영 및 분석하였으며, 평균속도 21m/s임을 알 수 있었다. 또한, 상용 전자기 해석 소프트웨어 MAXWELL을 이용한 자속 밀도 해석값와 실험값을 비교한 결과, 오차는 약 9.5%이었다.

• 한국운동역학회지
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• 제14권3호
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• pp.301-311
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• 2004

The purpose of this study was to verify the usefulness of the Mathcad program as a tool for the studying and teaching the sport biomechanics. A projectile motion was analyzed because it is the one of the most popular motion in sports activities. A 3 dimensional CG data for the high jump bar clear phase was used to calculate the initial velocity vector of the CG. Linear regression function and other functions such as cubic spline and derivative of Mathcad were used to calculate this vector. Finally, the approach angle to the bar and peak jump height was calculated. Programming in Mathcad was relatively easy compare to traditional computer language such as Fortran and C, because of the unique documentation method of Mathcad. Additionally the 2 and 3 dimensional graph function was very easy and useful to describe the mechanical data. If the use of Mathcad program is more popular in the field of sport biomechanics, it could greatly contribute to overcome the limit of research caused by the lack of proper programming ability.

• 항공우주시스템공학회지
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• 제6권4호
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• pp.29-33
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• 2012

This paper is focusing on the difference from experiment result and method through dynamic loaded from impact analysis about inertia measure unit of high speed projectile. At Inertia measure unit dynamic load is applied when the high speed projectile is operated by impact to inside. it is necessary to design inertia measure unit enduring from external effect with operating environment. Investigation of material deformation with high strain speed is performed for military purpose, and still concerned to many scientist. From this study, this paper will prove of impact analysis result through comparing with experiment result and method when applied dynamic load.

• 소성∙가공
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• 제12권2호
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• pp.128-133
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• 2003

In this study, the momentum conservation type punching mechanism for micropunching system was developed to avoid the punch failure in the misaligned status between the punch and die. The punching energy can be precisely controlled by the falling height of the projectile mass and the intermediata mass, which contacts with the punch, transmit the energy to the punch with the same contact condition. The potential energy of the projectile mass is converted to kinetic energy at the light weight punch that the projection speed into the sheet metal workpiece can be accelerated. The butt formation characteristics for the alignment condition and for the projection speeds are investigated to verify the feasibility of the proposed punching mechanism.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.55-60
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• 2004

This study is concerned to the perforation phenomena of the oblique dual-plate by projectile. Experiment and simulation related to that was carried out. the variables considered in this phenomena include the electrolytic zinc coated steel sheet and carbon steel rod. In the former, the confirmation and projectile velocity possible phenomena of real phenomena is done, the latter, the effect of parameter such as time-step and grid space length is analized by using the three-dimensional Lagrangian explicit time-integration finite element code, HEMP. this code use the eight node hexahedral elements and in this study, Von-Mises Criteria is used as the strength model, Mie-Gruneisen is as the Equation of State. the simulation was performed by contrast with the experiment. through the calibration of the parameter of lagrangian code, reasonable result was approached.