In this study, the uncertainty in the ballistic test was calculated. Characteristic factor plots were used to identify the sources of uncertainty. The results are as follows. First, the uncertainty about the projectile was calculated to be 0.008m/s. Second, the uncertainty for depth measurement was calculated to be 0.03mm. The biggest factor influencing the uncertainty was the human error by the measurer. Therefore, in order to reduce the uncertainty, it is necessary to minimize human intervention by introducing automatic measuring equipment.

In this study, quality keywords of frequent mention of failures were extracted by analyzing the field operational data of main battle tanks recorded for about 5 years. As a result of the data analysis, the leaf spring assembly of the crew hatches corrosion and failure was frequently occurred. FEA(Finite Element Analysis) and tests were performed to analyze the cause of the failure, and it was confirmed that durability of the leaf spring was insufficient. Therefore a design modification study was conducted to improve durability of the leaf spring, and FEA and durability tests demonstrated the improvement. As a result, the durability of leaf spring was improved at least 3.3 times compared to before improvement. This study will contribute to suggesting the use of data analysis in the defense area and improving the operability of the main battle tanks.

During the field operation of the Korean MBT(Main Battle Tank), the multi-smoke projectile launching system failed to function. As a result of conducting analysis, it was confirm that the gear shaft of reducer was failed. Therefore, a study on improvement in impact resistance of the reducer was conducted. The reducer was improved impact resistance by changing the design and material of gear shaft. The reliability of modified reducer was investigated by finite element analysis, performance and environmental tests. As a result of analysis, a strength of the modified gear shaft was improved by about 20 times than before improvement. The results of performance and environmental test show that the modified reducer is applicable for Korean MBT under the severe conditions. The quality improvement of multi-smoke projectile launching system contributes to survivability of Korean MBT.

The suspension system of special tracked vehicle is using hydraulic piston pump to adjust track tension and control vehicle position change. During operation of vehicle on rough field, failure of suspension control was occurred due to the piston pump failure. In this study, investigation was performed to analyze the cause of hydraulic piston pump failure. Main reason of piston pump failure is strong peak pressure and insufficient structural safety of shoe. The static stress analysis considering peak pressure was performed to find the weak point of the shoe. From the result, it is confirmed that pass hole of lubrication is the weakest point. Improved piston shoe shows 27% decrease in maximum stress and satisfies the design target which is less than 40% of stress margin.

Corrosion of the steel reinforcement in a cold and saline environment leads to the overall deterioration of reinforced concrete structures. To avoid such deterioration, Glass Fiber Reinforcement Polymer(GFRP) rebars are used in place of steel reinforcement. In the present paper, in order to examine the effect of reinforcement ratio of concrete beam reinforced with lap-spliced GFRP bar, nonlinear finite element analyses are performed.