• Journal of Drive and Control
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• v.19 no.4
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• pp.10-18
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• 2022

Air-drop hammer press and counterblow hammer press are widely used power-drop forging hammersemploying different forging blow mechanisms. It is important and necessary to analyze mechanical vibrations of these two different hammers in their forging processes in order to develop high performance forging hammers. In this study, these two forging hammers were mathematically modelled as mass-spring-damper systems. For these two different types of forging hammers, the forging efficiency and mechanical vibrations due to hammer forging blow were theoretically analyzed and compared. The force transmitted to the ground was also determined and compared. Especially, effects of mass ratio and restitution coefficient on forging efficiency were investigated.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.405-412
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• 2002

The performance of a hammer/driving systems is a major factor which affects bearing capacity and integrity of installed piles. Hammer performance can be evaluated from the results of dynamic pile testing using Pile Driving Analyzer(PDA). By comparing the rated energy with measured maximum transferred energy(EMX), the energy transfer ratio(ETR) can be calculated. This paper based on the dynamic measurements of 442 cases in 130 piling projects and evaluated ETR according to the hammer types(hydraulic and drop hammers) and pile types(steel and concrete piles).

• Explosives and Blasting
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• v.10 no.1
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• pp.3-7
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• 1992

In the pilling works in the city, it is tend to transfered to the non-vibration pilling works. This drop-hammer pilling executed with in 2 meters distance to neighbour building structure. in the rainy season. According to imperical formula which tested in similar site, Vibration damaged area is within 14 meters radius from drop-hammer pilling site. The loratories Data of Dae Woo of Korea hausing Authority are refered to above poject.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.303-309
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• 2000

Seismic reflection method is applied to detect shallow location of limestone in Chechon area. The data using hammer source is compared with that of weight drop. Small size hammer and weight-drop are used as energy source and 100Hz geophones are used for data aquisition. Data processing is conducted utilizing the available processing technique of "Geobit", which is seismic data processing software developed by KIGAM. The result of above data processing, the velocity of topsoil layer is 1,250m/sec. The velocity of this area is higher than other area because loading trucks pass this area and make this layer compact. And in limestone area, hammer is proposed to energy source instead of weight drop because the energy propagates the layer very well.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.469-476
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• 2001

The Ν-value in the standard penetration test(SPT) is affected by the magnitude of the rod penetration energy transmitted from the falling hammer as well as the geotechnical characteristics of the ground. Understanding of the striking energy efficiency in the SPT equipment is getting important for that reason. The energy efficiencies of the doughnut hammer with the hydraulic lift system and the automatic trip hammer system were investigated through field tests using the instrumented rod and wave-signal acquisition systems including the pile driving analyzer(PDA) . The rod energy ratio, ΕR$\_$r/ was defined as the ratio of the energy delivered to the drilling rod to the potential free-fall energy of the hammer. It appears that the type of the hammer and lift/drop system had a strong influence on the energy transfer mechanism and ΕR$\_$r/ also varies according to the energy instrumentation system and the analysis methods.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.2
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• pp.41-50
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• 2019

Stiffness characteristic of subgrade is one of the most important aspects for the design and evaluation of pavement and railway. However, adequate field testing methods for evaluating the stiffness characteristics of the subgrade have not been developed yet. In this study, an in-situ dynamic stiffness analyzer (IDSA) is developed to evaluate the characteristics of subgrade stiffness along the depth, and its performance is evaluated in elastic materials and a compacted soil. The IDSA consists of a falling hammer system, a connecting rod, and a tip module. Four strain gauges and an accelerometer are installed at the tip of the rod to analyze the dynamic response of the tip generated by the drop of hammer. Based on the Boussinesq's method, the stiffness and Young's modulus of the specimens can be calculated. The performance of IDSA was tested on three elastic materials with different hardness and a compacted soil. For the repeatability of test performance, the dynamic signals for force and displacement of the tip are averaged from the hammer impact tests performed five times at the same drop height. The experimental results show that the peak force, peak displacement, and the duration depend on the hardness of the elastic materials. After calculating the stiffness and elastic modulus, it is revealed that as the drop height of hammer increases, the stiffness and elastic moduli of MC nylon and the compacted soil rapidly increase, while those of urethanes less increase.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.71-78
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• 2002

The N-value from the standard penetration test(SPT) is affected by the magnitude of the rod penetration energy transmitted from the falling hammer as well as the geotechnical characteristics of the ground. Understanding of the striking energy efficiency in the SPT equipment is getting important for that reason. The energy efficiencies of the various type of equipment were investigated through field tests using the instrumented rod and wave-signal acquisition systems including the pile driving analyzer(PDA). The rod energy ratio, ERr was defined as the ratio of the energy delivered to the drilling rod to the potential free-fall energy of the hammer. It appears that the type of the hammer and lift/drop system had a strong influence on the energy transfer mechanism and ERr also varies according to the energy instrumentation system and the analysis methods.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.04a
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• pp.127-135
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• 2002

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.1-6
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• 2014

When the fluid energy convert into kinetic energy due to water hammer, the propagation velocity of pressure wave appear. The propagation velocity of pressure wave(1050 m/s) of very fast could be damage to the pipeline system. If the occurrence of water hammer is due to down-pressure, the faster the air exhaust or supply device is needed. it is high Speed Air Valve. In this paper, Each 3.12, 3.13, 3.72, $3.74kg/cm^2$ pipeline pressure were setting, and then executed pressure rapid drop for obtaining a high Speed Air Valve Operating time and pressure change data. the result was that pipe line pressure stabilization time were each 0.98, 1, 1.22, 1.25 sec. In other words, that pressure drop experimental results pipe line pressure was equal to atmospheric pressure without negative pressure After about one second. The study result would be useful to pipe line system stability design because this data could be foresee pressure stabilization time.