• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.3
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• pp.259-265
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• 2009

In the traditional percussion locks of small arms, a firing pin is struck by a hammer rotating on a single center of rotation, which makes the percussion mechanism simple and reliable. In order to strike the firing pin by the hammer, however, the firing pin should be located within the radius of rotation of the hammer. As the distance between the striking point of the firing pin and the center of rotation of the hammer becomes longer, the radius of rotation of the hammer should also be increased, which results in the increase of the volume and weight of the small arms because the hammer needs the more space for its operation inside of the small arms. In this paper, a link type percussion lock was newly proposed in order to overcome the limitation of designing small arms when using traditional percussion locks, as mentioned above. The link type percussion lock was modeled by using multi-body dynamics software and designed to satisfy the requirements such as striking force level of the hammer exerting on the firing pin enough to detonate the percussion cap of ammunitions and the safety on the accidental drop. It was applied to the newly developed dual-barrel weapon system, in which the weight and overall length are important design factors, and verified by durability test and drop test on the ground.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.648-655
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• 2020

The firing pin of modern automatic rifles detonates the primer of loaded ammunition via a hammer. During this process, the firing pin receives an impact load and repetitive force throughout the life of the rifle. An endurance test of a rifle showed that the firing pin breaks prematurely at 96.26% of life. Accordingly, a case study was conducted through cause analysis and a reconstruction test. Optical microscopy and scanning electron microscopy of the broken surface of the firing pin showed that a crack began in the circumferential direction of the surface, resulting in a fatigue crack to the core after repeated impact. Crack growth and fatigue destruction occurred at the end due to the repetitive impact and was estimated using a notch. For verification, a sample that produced a 0.03mm circumferential notch was broken at 64.25% of life in the reconstruction test. A test of breakage according to the notch types showed that a 0.3mm and a 0.5mm one-side notch were broken at 66.53% and 50.76%, respectively, and a 0.03mm six-point notch was broken at 85.65%. The endurance life of a sample firing pin with a rough surface and tool mark was examined, but an approximately 381 ㎛ internal crack formed. Through this study, failure for each notch type was considered. These results show that quality control of the notch and surface roughness is essential for ensuring the reliability of a component subjected to repeated impact.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.102-111
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• 2014

An analytical model was developed to understand the physics and predict the functional performance of a pin puller. The formulated model is based on one-dimensional gas dynamics for an ideal gas. Resistive forces against pin shaft movement were measured in quasi-static mechanical tests, the results of which were incorporated into the model. The expansion chamber pressure and the pin shaft displacement were measured from an actual firing test and compared to the model prediction. The gas generation rate was adjusted by a correction factor, and the heat transfer rate was obtained through parametric analysis. The validity of the model is assessed for additional firing tests with different amounts of pyrotechnic charge. This model can provide knowledge on how the pin puller functions, and on which design parameters contribute the most to the actuation of the pin puller. Using this model, we estimate the functional safety factor by comparing the energy generated by the pyrotechnic charge to the energy required to accomplish the function.

• Tribology and Lubricants
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• v.36 no.3
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• pp.168-192
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• 2020

In recently designed diesel engines, the running conditions for piston-pin bearings have become severe because of the higher combustion pressure and increased temperature. Moreover, the metal removal from the bushing material has strongly reduced the ability of the antifriction material to accept asperity contacts. Therefore, it is necessary to find ways of reducing wear scar on the connecting-rod small-end bushing and piston-pin boss bearing related to the higher combustion pressure on the power cell of an engine. In this work, the position and level of material removal from the surfaces of the bushing and bearing under such severe operating conditions - for example, maximum power and torque conditions of a passenger car diesel engine - are estimated for several combinations of surface roughness. First, piston-pin rotating motion is investigated by calculating the friction coefficient at piston-pin bearings, the oil film thickness, and the frictional torques induced by hydrodynamic shear stress. Subsequently, the wear scarring on the surfaces of a connecting-rod small-end bushing and two piston-pin boss bearings related to piston-pin rotational motion is numerically calculated under the maximum power and torque operating conditions. This work is helpful to determine the reasonable surface roughness of the bushing and bearing for reducing wear volume occurring at the interface between a bearing and a shaft.

• Journal of Korean Society for Quality Management
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• v.47 no.3
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• pp.417-424
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• 2019

Purpose: In this study, the goal is to analyze this case to prevent the same accidents when using one-shot rifle. Methods: Detailed analysis of damaged parts must first be made in order to determine the cause of the abnormal explosion. The cause of abnormal operation can be determined by analyzing the information of damaged components and the firing mechanism of the weapon step by step. Also we can refer to a statement of shooter, witness and accident scene situation. Based on this theory, cause of abnormal firing can be narrow down. Results: Fracture of pin for fixing firing and latch is cause of abnormal operation of firing. Conclusion: It is deemed that periodic inspection and fundamental improvement of the structure are required to prevent the same accident as this.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.319-328
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• 2006

This paper presents a method for analysis of the mechanical behavior of a crankshaft in a four-cylinder internal combustion engine. The purpose of the analysis was to study the characteristics of the shaft in which the pin and arm parts were assumed to have a uniform section in order to simplify the modal analysis. The results of natural frequency transfer function and mode shape were compared with those obtained by experimental work. The results obtained from the comparison showed a good agreement with each other and consequently verified the analysis model. Furthermore, a prediction of crankshaft characteristics under the firing condition, by using the model, was performed. This study describes a new method for analyzing the dynamic behavior of crankshaft vibrations in the frequency domain based on the initial firing stages. The new method used RMS values to calculate the energy at each bearing journal and counter weight shape modification under the operating conditions.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.273-280
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• 2008

Monolith aperture-type oxygen sensors with simple structure of YSZ(pin-hole)/Pt/ YSZ(solid electrolyte)/Pt were fabricated by co-firing technique. To enhance the yield of productivity, a couple of YSZ green sheets for diffused barrier and solid electrolyte were prepared by tape-casting and co-firing method. The limit current characteristics of the oxygen sensors were measured between 500 and $650^{\circ}C$ The heating temperature of $600^{\circ}C$ was optimum as a portable oxygen sensor in the range of oxygen concentration from 0 to 75 vol%. Linear proficiency of limit current behavior as a function of oxygen concentration was controlled by the variation of aperture dimension. The fabricated oxygen sensors showed the stable sensing output for 30 days. Gas leakage in bonding area due to warping, cracking and thermal cycling was not found in the period.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1121-1126
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• 2003

Strength evaluation was carried out for the fillet and oil hole of crankshaft of medium speed diesel HiMSEN engine to verify initial concept design. Alternating torque obtained from torsional vibration analysis and radial force due to firing pressure were applied. It was assumed that the maximum alternating torque and radial force occur simultaneously. Weak points in view of fatigue are proceeding fillet and crank pin fillet area and the minimum normalized fatigue safety factor is 1.17 at crank pin fillet. The fatigue strength of the oil hole was evaluated to verify the effect of the surface roughness of the oil hole. As results, the specific level of the inner surface roughness and the polishing depth of the oil hole for sufficient fatigue strength was suggested. The maximum stress value and stress distribution at the inner surface of the oil hole can be easily estimated at initial design stage by the newly developed method.

• Tribology and Lubricants
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• v.34 no.3
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• pp.93-107
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• 2018

The purpose of Part I of this study is to find the potential region of wear scarring on engine journal bearings operating at a constant angular crank shaft velocity under firing conditions. To do this, we calculate the applied loads and eccentricities of a big-end journal bearing installed on a four-stroke and four-cylinder engine at every crank angle. Then, we find potential wear regions, such as a minimum oil film thickness, at every crank angle below most oil film thickness scarring wear (MOFTSW) obtained based on the concept of the centerline average surface roughness. Thus, the wear region is defined as a set of each film thickness below the MOFTSW at every crank angle. In this region, the wear volume changes according to the wear depth and wear angle, depending on the minimum oil film thickness at every crank angle. The total wear volume is the summation during one cycle. Graphical views of the region in the two-dimensional coordinates show the crank angle and bearing angle along the journal center path, indicating the position of the minimum oil film thickness. The results of wear analysis show that the possible wear region is located at a few tens of angles behind the upper center of a big-end bearing at maximum power rpm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4828-4834
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• 2015

From the moment that a firing pin triggers the detonator to the moment that a grenade leaves a barrel is called Action Time. Since a loading and percussion of 40mm grenade happens simultaneously, action time should be within a certain time in order to prevent a Jamming malfunction. Previously, unreliable action time device of 40mm grenade made it difficult to improve quality assurance of K4 Grenade Machine Gun. Here, various sensors were compared and a special device was designed to seek an accurate measurement on action time. In this device, the gap between a signal from an optical sensor in Firing Pin and that from Eddy current probe in the barrel was recorded and data were sent to a computer in real time. Confirming if action time is within the criteria, it is expected that action time plays an important role in quality assurance on 40mm grenade.