• Tribology and Lubricants
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• v.37 no.2
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• pp.54-61
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• 2021

The effect of the sand blasting before TiAlN coating in the manufacture of WC hard metal alloy tips have been studied. For four different tips, according to the status of processing of the sand blasting and the coating, residual stress measurement by X-ray diffraction and several tests for mechanical properties have been conducted. The results suggest that there was no difference in static mechanical properties, such as hardness, surface roughness and elastic modulus, between two coatings. Furthermore, compressive residual stress was generated equally on their surfaces. Additionally, the compressive residual stress in substrate WC was found to increase greatly when subjected to sand blasting treatment. However, the compressive residual stress decrease after coating regardless of sand blasting treatment. Nevertheless, it is confirmed that the compressive residual stress generated in the coating after sand blasting is less than that in the non-sandblasting coating. This was attributed to the plastic deformation occurring in the WC substrate during coating after sand blasting. In contrast to the scratch test results, sand blasting was assumed to have a negative effect on the adhesion between the coating and substrate. This is because there is a high possibility of microcracks due to plastic deformation in the WC substrate under the coating after sand blasting.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.64-69
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• 2020

To determine the effective factors for microparticle blasting with precise sequence position control in the x-axis and y-axis directions, we conducted a statistical experimental analysis of blasted square shapes by considering five condition factors. The control input and output were operated simultaneously by rotation-linear motion conversion and fine particles were blasted onto the aluminum specimen by precise position control driving using multiple execution codes. The micro-driving device used for processing was capable of microparticle blasting and of controlling the system through contact with a limit sensor at high speed and a two-degree-of-freedom driving mechanism. Our experiments were conducted on 1,050 specimens of pure aluminum (containing <1% of other elements). The effects of several factors (e.g., particle and nozzle diameters, blasting pressure, and federate and blasting cycle numbers) on the surface roughness and blasted surface's depth were verified through a statistical experimental analysis by applying the dispersion analysis method. This statistical analysis revealed that the nozzle diameter, the blasting pressure, and the blasting cycle number were the dominant factors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.310-315
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• 2017

Although studies evaluating the effects of the blasting vibration on the adjacent structures from various angles have continued, cases of securing the safety of the adjacent buildings and researching the proper blasting method for the field condition by analyzing the vibration waveform of the measuring field while performing the open pit blasting are poor. Therefore, it is necessary to present a remedy for blasting pattern selection through test blasting that is appropriate for field conditions, and is economical and efficient. In this study, open pit blasting work was conducted based on the separation distance applied according to the standard blasting method by test blasting and the vibration regulation standard in the road expansion construction site to measure the blasting vibration value, and the vibration prediction equation by blasting methods was examined using a regression analysis computer program to calculate K, N, and R of the confidence level 95%. By setting the blasting allowed vibration standard of the test blasting target area to 0.3cm/sec, and the charring weight and blasting method by the separation distances according to the blasting vibration estimation equation of the open pit blasting guideline and the blasting vibration estimation equation of the test blasting were compared/analyzed, it was possible to identify the factors that increased the working expenses. In addition, the measurement and analysis of the adjacent structures during open pit blasting and the blasting vibration were performed after selecting the most adjacent structure to the open pit blasting spot to analyze the problems on the test blasting procedure and analysis method in the open pit blasting design/construction guidelines, which appeared in the process of completing open pit blasting construction, and a remedy is presented.

• Geotechnical Engineering
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• v.11 no.3
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• pp.55-68
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• 1995

This paper is the analysis of the relationship between RQD and decay constant, blasting vi bration constant of cube root scaling and square root scaling, through experimental blast ins test in subway construction for excavation of shaft hole by bottom blasting. The magnitude of particle velocity is largely effected by the distance from blasting source, the maximum charge per delay and the properties of ground. In order to verify the effects of ground properties on blast-induced vibration, the relation-ship between magnitude of blasting vibration and Rock Quality Disignation which stands for joint property was studied. The results of test are verified that blasting vibration constant "K" and the absolute value("n") of decay constant relatively increse as RQD increased. According to the result, it can be predict the particle velocity by the blast -induced vibration in bottom blasting pattern.om blasting pattern.

• Explosives and Blasting
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• v.41 no.1
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• pp.32-45
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• 2023

Environmental regulations in Korea for blasting at industrial sites have conservative standards, which often result in reduced efficiency and cost-effectiveness due to the consideration of environmental regulations and public complaints. Therefore, there is a need for blasting methods that can reduce environmental damage while improving construction efficiency and cost-effectiveness. In this study, we analyzed the effects of the PA-Deck (Paraffin Air-Deck) blasting method, which is a kind of Air Decoupled Charge method in principle utilizing a paraffin-infused paper tube as an air gap, on reducing blasting hazards and improving blasting efficiency. The analysis also evaluated the effectiveness of newly applied equipment for collecting blasting vibration data, and derived the relationship between the explosion velocity and vibration velocity of explosives, and performed frequency analysis of the vertical component. The results of the blasting vibration velocity analysis showed that the Paraffin Waxed Paper Tube-based blasting method exhibited significantly lower vibration velocities compared to conventional blasting methods, and it was judged that more uniformly small-sized fragmented rocks were generated.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.657-664
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• 2002

This study presents the influence of blasting-induced vibration on the adjacent structures in rocks of various RMR values. 3D finite element analysis was performed to simulate the behaviour of tunnel and adjacent structures during rock excavation. The blast loadings were evaluated from the blasting pressure which is depending on the type and amount of explosive charges. Influencing factors for the stability of adjacent structures and ground conditions were reviewed in terms of structural dimensions and RMR values. The stiffness and load of adjacent structures are modeled in the numerical analysis to Investigate blasting effects of the size of adjacent structures. The vibration velocity and maximum particle velocity was increase sharply when the RMR value changed from 30 to 50. The effect of particle velocity was minimized at the width of structure become 2 times of tunnel diameter.

• Explosives and Blasting
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• v.35 no.3
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• pp.9-14
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• 2017

Coupling effects of the stemming materials for single borehole were studied by AUTODYN analysis and compared to understand the role of different stemming materials on transmitting the pressure from blasthole to the surrounding rocks. Five different material properties, air, sand, water, 10% and 20% gelatin were selected. Authors assumed that high pressure detected in borehole means better fragmentation. Simulations show that these coupling materials lead to different level of pressure in the blasting hole and 20% gelatin turns out to be highest among them. Results show that gelatin can be used as better coupling material than sand or water.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.31-37
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• 1994

The effects of blasting and ground vibratons on curing concrete have not been well studied. As a results unrealistic and costly ground vibration constraints have been placed on blasting and piling when it occurs in the vicinity of curing concrete. To study the effects of ground vibrations, a shaking table was made to produce peak particle velocities in the nearly same frequency range as found in construction blasting. Concrete blocks of 33.3X27.7X16.2cm were molded and placed on the shaking table. Different sets of concrete blocks were subjected to peak vibrations of 0.25, 0.5, 1.0, 5.0 and 10cm/sec. The impulses were applied at two hour intervals for thirty seconds. Along with unvibrated concrete blocks, the vibrated concrete samples with 60.3mm in diameters were measured for elastic moduli, sonic velocity, tensile and uniaxial compressive strength. Test results showed that the vibrations in curing concrete generally have effects on the uniaxial compressive strength or physical properties of the concrete.

• Explosives and Blasting
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• v.13 no.1
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• pp.20-31
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• 1995

Many methods and techniques to reduce ground vibrations are well known. Some of them are to adopt electric milisecond detonators with a sequential blasting machine or an initiating system with an adequate number of delay intervals. The types of electric detonators munufactured in Korea include instantaneous, decisecond and milisecond delays byt numbers of delay intervals are only limite from No.1 to No.20 respectively. It is not sufficient to control accurately milisecond time with these detonators in tunnel excavation. Sequential fire time refers to adding an external time delay to a detonators norminal firing time to obtain sequential initiation and it is determined by sequential timer setting. To reduce the vibration level, sequential blasting machine with decisecond detonatore was adopted. A total of 134 blasting was recorded at various sites. Blast-to-structure distances ranged from 20.3 to 42.0 meter, where charge weight varied from 0.25 to 0.75 kg per delay. The results can be summarized as follow : 1. The effects of sequential blasting machine on the vibration level are discussed. The vibration level by S.B.M. are decreased approximately 14.38~18.05 to compare to level of conventional blasting and cycle time per round can be saved. 2. The empirical equations of particle velocity were obtained in S,B.M. and conventional blastin. $V=K(D/W^{1/3})-n$. where the values for n and k are estimated to be 1.665 to 1.710 and 93.59 to 137 respectively. 3. The growth of cracks due to vibrations are found but the level fall to within allowable value.

• Explosives and Blasting
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• v.22 no.1
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• pp.57-65
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• 2004

Explosive blasting in tunnel excavation produces ground vibration and air blast as its side effects, which may cause complaints from nearby residents. This study was intended to investigate the propagation characteristics of ground vibration induced by tunnel blasting and to evaluate its effects on the residential structures near the site. We have conducted field measurements for 6 blasts and acquired vibration data from 70 measuring points, some of which on positioned inside the tunnel for comparative reason. Various documentation was reviewed to determine an allowable level of peak particle velocity for the residential structures in the area and the allowable limit was set to 0.5 cm/sec. Propagation equations for peak particle velocities were derived from regression analyses using the data acquired at both the surface and the underground tunnel. Finally we proposed appropriate predictive equations for the two areas and a safe blasting criterion.