• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.207-207
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• 2000

Fuel consumption of a modern combustion engine is significantly influenced by the mechanical friction losses. The reduction of the engine friction losses offers a remarkable potential in emission and fuel consumption reduction. The analysis of the engine friction distribution of modern engines shows that the piston and the cylinder have a high share at total engine friction. The present study uses PISDYN(by Ricardo) software to analyze the friction losses. The design parameters such as skirt profile, center of mass of the piston are shown to have key influences on the friction losses.

• Journal of the KSME
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• v.28 no.5
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• pp.469-475
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• 1988

연료소비율의 향상은 점차 감소되어 가는 경향에 있다. 그 원인은 3원촉매변환기 채용에 의한 이론공기연료비의 사용, 기관의 연소개선이 발전하여 고압축비화에 의한 연료소비율 향상이 더 이상 어렵게 되었다는 점을 들 수 있다. 한편, 고압축비화의 역효과로는 연소실내 최고압력이 증가하여 각부의 강도나 기관 소음의 문제가 대두된다. 이들 역효과를 타파하여 충분한 연료 소비 향상을 얻을 수 있는 수단이 단기적인 과제가 될 것이다. 전자제어, 희박연소, 마찰저감 등 통상의 엔진의 개량에 대한 노력이 계속될 것이다.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.6
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• pp.638-643
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• 2013

Nowadays, the hydraulic power unit (HPU) has been increased its working pressure and enlarged its capacity in order to improve the performance of the hydraulic system, but it produces noise leveled around 110dB(A) during operation. Recently, due to the reinforcement of industrial safety regulations and the requirement of improving work environment, a separated HPU room is installed at outside or underground of the building as to reduce the noise from HPU, but there are also problems of power loss owing its fluid friction of pipe system and of deficient accessibility during its failure accident. In this study, experiment is performed to improve the noise characteristics with installing a soundproof chamber to minimize the power loss and exclude effectively the high leveled noise, which is generated during the power conversion of HPU.

• International Journal of Highway Engineering
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• v.12 no.1
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• pp.29-37
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• 2010

Porous pavements can provide road users with beneficial characteristics such as skid resistance and surface water drainage under rainy condition, and they cause less tire-road noise than conventional hot mix asphalt(HMA) pavements. However, voids of porous pavements are easily clogged by road debris at early stages, which leads to frequent maintenance works. Therefore, this study focused on the way of minimizing void clogging in porous pavements. During mixture design, the quantity of coarse aggregate has been increased to form many straight void conduits (SVCs) in porous HMAs. These SVCs were found to be effective resisting the void clogging problems. Four different porous HMAs(19mm, 13mm, 10mm, and 8mm) were developed and placed on highway roads. Their performances were validated with field tests during the past four years.

• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.31-39
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• 2004

The bored pile is widely used as a low noise and vibration piling method in Korea. However, there is design tendency to minimize the friction capacity of the bored pile because of uncertainty and the quality control specification is not set up. This research analysed the strength characteristics of cement paste after the uniaxial compression test with various condition. Test results show that the compressive strength of cement paste with w/c=0.83 was up to $156.0kgf/cm^2$, and the lower w/c ratio and the longer age, the strength of cement paste increased. Also the higher soil mixing ratio, the strength of soil cement decreased, and too high soil mixing ratio caused the malfuction of soil cement. Also this research analysed the 188 dynamic pile test results which were performed before and after hardening of cement paste. Analysis result showed that the average ultimate unit friction capacity was $9.1tf/m^2$ and this result surpassed the common design criteria of the bored pile.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.19-31
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• 2024

In Korea, driven piles are generally penetrated up to weathered rock or harder strata. Friction piles have been used to some extent in the southwest coastal area with deep soils; however, friction piles are not extensively due to uncertainties about construction quality. The embedded pile construction method is primarily used due to noise and vibration complaints. However, in Southeast Asian countries (e.g., Cambodia, Myanmar, and Vietnam), where soft sediments are deep, the driven pile method is commonly used due to its economic advantages. Construction companies are increasingly entering overseas construction markets, e.g., Southeast Asia; thus, it is necessary to understand the behavior of driven friction piles in the soil and improve on-site engineering management to gain market competitiveness in these countries. In this study, the bearing capacity of friction piles driven into clayey coastal soils in Vietnam with time-dependent characteristics was evaluated based on the dynamic and static pile load tests. Based on the results, a modified Danish formula is proposed for on-site quality management.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.67-75
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• 2011

Domestic economic development, industrialization, and urbanization have brought along not only increased highway traffic but also elevated traffic noise levels. Thus, it is necessary to accurately predict the traffic noise levels in order to address the public demand of alleviating the noise levels in urban areas. In this study, the method of evaluating the sound power level of road traffic was investigated in terms of considering the types of road surface and vehicle, based on previous researches. Regarding CPX (Close Proximity Test) and Pass-by test, the measured noise data of Test Road of Korea Highway Corporation were utilized in order to construct the database of sound power levels of various vehicles. Specifically, the 38 noise measurement and analysis in 1/1-octave band frequencies at 12 pre-selected sites were carried out, considering topography and road surface. Finally, the comparison study was conducted between predicted and measured data in terms of traffic noise. The traffic noise prediction was based on the KRON (Korea Road Noise) program, which was developed being equipped wit 3-dimensional GUI. In addition, the traffic noise characteristics were evaluated in terms of vehicle types and pavement surface conditions.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.233-241
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• 2018

In this paper, we develop a durability test method that can verify the noise caused by the repeated load on the door trim grip handle. The test method was developed in consideration of the load mode and durability test cycle applied to the grip handle. In order to verify the validity of the method, we demonstrated the door trim grip handle noise that occurred in the field claim with the product in the early stage of mass production through the developed test method. Finally, It is used to detect and improve the noise of subsequent development products through the currently developed test method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.546-552
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• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.5
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• pp.520-526
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• 2016

Squeal noise is a typical brake noise that is annoying to both passengers and pedestrians. Its frequency range is fairly wide from 1 kHz to 18 kHz, which can be distressful to people. The brake squeal noise occurs due to various mechanisms, such as the mode coupling of the brake system, self-excited vibration, unstable wear, and others. In this study, several parameters involved in the generation of a squeal noise are investigated experimentally by using a brake noise dynamometer. The speed, caliper pressure, torque, and friction coefficient are measured as functions of time on the dynamometer. The contact pressure and temperature distributions of the disc and the pad are also measured by using a thermal imaging camera and a pressure mapping system. As a result of the simultaneous measurement of the friction coefficient and squeal amplitude as functions of the velocity, it is found that the onset of the squeal may be predicted from the ${\mu}-v$ curve. It is also found that a non-uniform contact pressure causes instability and, in turn, a squeal. Based on the analysis results, design modifications of the pad are suggested for improved noise characteristics.