• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.8
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• pp.51-59
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• 2019

Flow forming is an eco-friendly and high-efficiency plastic deformation process with fewer chips during a process which is specifically used to manufacture seamless tubular products like tire wheels, rocket motor cases etc. On the development of mortar barrel using Inconel718 tube, some flow formed products had dimensional errors on their thickness. In this study, our purpose is to optimize the process conditions with the smallest dimensional error. In order to find an optimum process condition, 2D axisymmetric FEM simulation analyses with Taguchi method were conducted. Geometric variables (attack angle, flatting angle, roller nose radius) and operating parameters (depth of forming, feed rate) are considered as control factors. Forward flow forming with single roller was first analyzed to determine the effective factors using AFDEX software and attack angle of the roller was identified as the most influential factor. Also, the nose radius of the rollers was confirmed as a significant factor in multi-rollers flow forming system. The effect of rollers offset values are also studied and finally, we proposed optimal conditions to improve the accuracy of flow forming process with Inconel718 tube for mortar barrel manufacturing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.69-76
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• 2015

This study investigates the thermal efficiency and the efficiency of heat transfer through thermal analysis when the same heat is applied to a mortar frame by firing with various configurations of mortar. As the inside diameter of the mortar increases, the additional material must be reinforced. In comparison with the extent of getting cold due to models, a mortar with the strut under the gun barrel becomes cooler than one with no strut. The thermal deformation at firing becomes different. According to the configuration of mortar and its inside diameter, the extent of getting cold becomes different. This study result can be effectively applied for improving the efficiency of the heat transfer of mortar.

• Conservation Science in Museum
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• v.26
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• pp.161-182
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• 2021

A jungwangu, a type of medium-sized mortar, is a firearm with a barrel and a bowl-shaped projectileloading component. A bigyeokjincheonroe (bombshell) or a danseok (stone ball) could be used as a projectile. According to the Hwaposik eonhae (Korean Translation of the Method of Production and Use of Artillery, 1635) by Yi Seo, mortars were classified into four types according to its size: large, medium, small, or extra-small. A total of three mortars from the Joseon period have survived, including one large mortar (Treasure No. 857) and two medium versions (Treasure Nos. 858 and 859). In this study, the production method for medium mortars was investigated based on scientific analysis of the two extant medium mortars, respectively housed in the Jinju National Museum (Treasure No. 858) and the Korea Naval Academy Museum (Treasure No. 859). Since only two medium mortars remain in Korea, detailed specifications were compared between them based on precise 3D scanning information of the items, and the measurements were compared with the figures in relevant records from the period. According to the investigation, the two mortars showed only a minute difference in overall size but their weight differed by 5,507 grams. In particular, the location of the wick hole and the length of the handle were distinct. The extant medium mortars are highly similar to the specifications listed in the Hwaposik eonhae. The composition of the medium mortars was analyzed and compared with other bronze gunpowder weapons. The surface composition analysis showed that the medium mortars were made of a ternary alloy of Cu-Sn-Pb with average respective proportions of (wt%) 85.24, 10.16, and 2.98. The material composition of the medium mortars was very similar to the average composition of the small gun from the Joseon period analyzed in previous research. It also showed a similarity with that of bronze gun-metal from medieval Europe. The casting technique was investigated based on a casting defect on the surface and the CT image. Judging by the mold line on the side, it appears that they were made in a piece-mold wherein the mold was halved and using a vertical design with molten metal poured through the end of the chamber and the muzzle was at the bottom. Chaplets, an auxiliary device that fixed the mold and the core to the barrel wall, were identified, which may have been applied to maintain the uniformity of the barrel wall. While the two medium mortars (Treasure Nos. 858 and 859) are highly similar to each other in appearance, considering the difference in the arrangement of the chaplets between the two items it is likely that a different mold design was used for each item.