• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.89-99
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• 2007

The stiffness of the asphalt concrete is represented by the complex modulus $E^*$, which is very important properties in the mechanistic design of flexible pavement system. The moduli of asphalt concrete were generally determined by dynamic modulus test. However, the dynamic modulus testing method is too complex, expensive, and time consuming to be applicable on a production basis. The IR(Impact Resonance) method has been shown to be a truly simple nondestructive testing method which produces very repetitive, consistent results. The major object of this study was to estimate of the effects on IR tests for determining modulus of asphalt concrete including impact position, specimen support condition, impact steel ball size and sampling rate. The variations of IR test results with various testing conditions are within ${\pm}2.7%$.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.625-632
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• 2010

The moduli of concrete has been determined by various testing methods. The impact resonance (IR) method has been shown to be truly a simple nondestructive testing method which produces consistent results. It is possible to determine not only the modulus but also damping ratio from the IR test. However, the values of elastic modulus and damping ratio of concrete from the test is known to be affected by various test conditions including, specimen support condition, impact steel ball size and sampling rate. In this study, the optimum IR test conditions are suggested and validated experimentally. The test results showed that the recommended test conditions yielded a variation of resonant frequency within ${\pm}0.3%$ and damping ratio ${\pm}10.0%$. In addition, the modulus from the IR test was comparable to that from a static test when the effect of strain amplitude was properly taken into account.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.686-691
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• 2009

Damage due to frost action in pavement structure system is creating either frost heave or stiffness-weakening of subgrade soil follow melting. The formation of ice lenses requires a frost-susceptible soil, freezing temperatures, and continuous water supply. Eliminating one of these conditions suffices to significantly reduce the intensity of frost action. It is important to know characteristics of subgrade soil in frost susceptibility or decide degree of freezing permission. Also, study on the stiffness variation of subgrade soil during freezing and thawing cycle is very important. In this study, Impact resonance test for subgrade soil at freezing and thawing confirms that is applied for.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.95-102
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• 2019

Non-destructive methods such as rebound hardness method and ultrasonic method are widely studied for evaluating the physical properties, condition and damage of concrete, but are not suitable for detecting delamination and cracks near the surface due to various constraints of the site as well as the accuracy. Therefore, in this study, the impact resonance method was applied to detect the separation cracks occurring near the surface of the concrete slab and bridge deck. As a next step, the principal component analysis were performed by extracting various features using the FFT data. As a result of principal component analysis, it was analyzed that the reliability was high in distinguishing defects in concrete. This feature extraction and application of principal component analysis can be used as basic data for future use of machine learning technique for the better accuracy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.498-503
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• 2009

This paper presents the vibration problem of the Engine Casing (E/C) "B" deck in the handymax vessel and describes a method to avoid resonance. The first ship of the series did not have any vibration issue on the "B" deck. However, resonance condition occurred when additional machine was installed to the following vessels. To understand the dynamic characteristics of the deck, the normal mode analysis and impact test have been performed. Within the normal operating range of the vessel, the $1^{st}$ natural frequency of the E/C "B" deck is close to the main engine's $6^{th}$ order. Based on these analysis, a reinforcement on the deck was suggested and it proved to be effective. Since actual impact test after the reinforcement also confirmed the resonance avoidance.

• International Journal of Highway Engineering
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• v.16 no.3
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• pp.43-50
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• 2014

PURPOSES : The dynamic modulus can be determined by applying the various theories from the Impact Resonance Testing(IRT) Method. The objective of this paper is to determine the best theory to produce the dynamic modulus that has the lowest error as the dynamic modulus data obtained from these theories(Complex Wave equation Resonance Method related to either the transmissibility loss or not, Dynamic Stiffness Resonance Method) compared to the results for dynamic modulus determined by using the Universal Testing Machine. The ultimate object is to develop the predictive model for the dynamic modulus of a Linear Visco-Elastic specimen by using the Complex Wave equation Resonance Method(CWRM) came up for an existing study(S. O. Oyadiji; 1985) and the Optimization. METHODS : At the destructive test which uses the Universal Testing Machine, the dynamic modulus results along with the frequency can be used for determining the sigmoidal master curve function related to the reduced frequency by applying Time-Temperature Superposition Principle. RESULTS : The constant to be solved from Eq. (11) is a value of 14.13. The reduced dynamic modulus obtained from the IRT considering the loss factor related to the impact transmissibility has RMSE of 367.7MPa, MPE of 3.7%. When the predictive dynamic modulus model was applied to determine the master curve, the predictive model has RMSE of 583.5MPa, MPE of 3.5% compared to the destructive test results for the dynamic modulus. CONCLUSIONS : Because we considered that the results obtained from the destructive test had the most highest source credibility in this study, the dynamic modulus data obtained respectively from DSRM, CWRM were compared to the results obtained from the destructive test by using th IRT. At the result, the reduced dynamic modulus derived from DSRM has the most lowest error.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.71-77
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• 2010

Anti-freezing layer does not used in case of non frost heaving in subgrade soils. In this case, the modulus of subgrade soils were varied with freezing and thaw cycles under non frost heaving. That effect should be properly considered in pavement design. Impact resonance test that is nondestructive testing method was used for continuously determining the modulus of subgrade soils during freezing and thaw cycle. The modulus of subgrade soils was identical with freezing and thaw cycles under closed freezing and thaw system which is no water supplement into specimen during testing. There was also no difference in the modulus of subgrade soil between before and after freezing-thaw cycles for all specimens with different water content and density. That is thaw-weakening of subgrade soils do not occur under closed freezing and thaw system. The moduli at freezing conditions are varied with water content and density, but it can be ignored in practical design sense.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.4
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• pp.389-393
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• 2014

This paper presents one of the methods for design to reduce the noise and vibration of 200kW motor for electric propulsion ship. One of the important factors affecting vibration of the motor is the resonance. The natural frequency and natural mode of the 200kW motor is analyzed by using FEM tool and impact test equipment to avoid the resonance. Also, compare FEM result with impact test result to make a reliable FE model of 200kW motor. In order to find out the effect of the noise and vibration of the motor by electromagnetic excitation force, conduct electromagnetic-structure coupled analysis. These characteristics are much useful to design 200kW motor for electric propulsion ship.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.7
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• pp.3296-3301
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• 2011

The Porous pavement gains popularity because of several benefits. It is to minimize hydro-planning condition, spraying condition, and splash to increase friction resistance, and decrease noise. Also, other studies showed that it is important to have appropriate porosity to reduce noise and water flush. The purpose of this study is an evaluation on the mechanical properties of asphalt pavements for surface course. In this study the specimen was manufactured using the Gyratory compactor in order to compact the strengthened surface course that involved the two-layer pavement. This study is conducted by using Marshall stability test(KS F 2377), Impact resonance test, Schmidt hammer test(KS F 2730), and the Uniaxial compression test(KS F 2314). Using the Uniaxial compression test and Schmidt hammer test, the values of compressive strength and bearing capacity were measured, and the modulus of elasticity for each specimen was respectively measured using the Uniaxial compression test, Impact Resonance test.