• International Journal of Highway Engineering
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• v.16 no.2
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• pp.61-71
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• 2014

PURPOSES : The first generation of wide base tires introduced in the early 1980s was found to cause a significant increase in pavement damage compared to dual-tire assemblies. However, wide base tires have evolved considerably, and a new generation of wide base tire is thought to be comparable to conventional dual tires for pavement damage. A challenge associated with using wide base tires is the accurate quantification of pavement damage induced by these tires. The objective of this study was to investigate the responses of flexible pavement to continuously moving vehicular loading under various tire configurations. METHODS : The comparison of the strain/stress responses of full-depth pavement caused by conventional dual tire assembly and new generation of wide-base tires was performed. The FE model incorporates linear viscoelasticity of asphalt material and continuous moving load using implicit dynamic analysis. RESULTS AND CONCLUSIONS : The result demonstrates that the new wide-base tires caused slightly more fatigue damage and less primary rutting damage in HMA layer than a dual-tire assembly, but caused more secondary rutting damage in subgrade than a dual tire assembly.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.204-209
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• 2003

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important for dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations. Therefore, by modifying the constitutive equation fur a nonlinear viscoelastic incompressible material developed by Lianis, the data fur the elastomeric bushing material was obtained and this data was used to derive the new load-displacement relation for radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed, Solutions were allowed fur comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.

• The Korean Journal of Rheology
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• v.9 no.3
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• pp.89-96
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• 1997

PS/PPO 블렌등의 동적 탄성율 E*($\omega$)와 동적 스트레인-광학계수 O*($\omega$)을 유리전이 영역에서 동시에 측정하여, PS/PPO 3종류조성블렌드의 E*($\omega$)와 O*($\omega$)완화거동을 조성 단 일 중합체와 비교고찰하였다. PS/PPO 블렌드의 $\alpha$-분산 점탄성 거동은 조성에 관계없이 거 의 유사하여 조성 고분자가 상호 협동적으로 완화하는 것을 알수 있었다. 그러나 광학적 완 화 스펙트럼 O*($\omega$)는 정성적으로 명확히 다른 거동을 보였다. 단일 PS와 PPO의 O*($\omega$)는 전 영역에 걸쳐 상반된 부로를 나타냈으며 두 고분자의 블렌드는 조성고분자의 반대부호를 상호보상으로 인하여 복굴절이 감소하였다. 3종류블렌드는 PPO의 조성이 증가함에 따라 상 호보상에 의해 O*($\omega$)의부호가 순차적으로 변하여 반전하였으며, 저 복굴절 PS/PPO 블렌드 의 PS조성이 65-80wt% 범위내에 있음을 추정할수 있었다. 상이한 부호를 갖는 복굴절 특 성으로 인하여 블렌드 내에서 각 성분 고분자의 완화 기여를 다순 가성법칙에 의해 정량적 으로 계산하는 것이 가능하였다. 또한 PS/PPO 블렌드의 상용성을 광학적 부분 기여 파라메 터를 사용하여 고찰하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.746-755
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• 1997

This paper addresses the systematic procedure using sequential approach for the analysis of the coupled thermo-mechanical behavior of a steady rolling tire. Not only the knowledge of mechanical stresses but also of the temperature loading in a rolling tire are very important because material damage and material properties are significantly affected by the temperature. In general, the thermo-mechanical behavior of a pneumatic tire is highly complex transient phenomenon that requires the solution of a dynamic nonlinear coupled themoviscoelasticity problem with heat source resulting from internal dissipation and friction. In this paper, a sequential approach, with effective calculation schemes, to modeling this system is presented in order to predict the temperature distribution with reasonable sccuracies in a steady state rolling tire. This approach has the three major analysis modules-deformation, dissipation, and thermal modules. In the dissipation module, an analytic method for the calculation of the heat source in a rolling tire is established using viscoelastic theory. For the verification of the calculated temperature profiles and rolling resistance at different velocities, they were compared with the measured ones.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.415-419
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• 2003

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important for dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations. Therefore, by modifying the constitutive equation for a nonlinear viscoelastic incompressible material developed by Lianis, the data for the elastomeric bushing material was obtained and this data was used to derive the new load-displacement for radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed. Solutions were allowed for comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.140-141
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• 2005

To measure elastic properties of semiconducting materials in power cable, we have investigated modulus of EVA/acetylene black composite showed by changing the content of acetylene black. The specimen was primarily kneaded in material samples of pellet form for 5 minutes on rollers ranging between 70[$^{\circ}C$] and 100[$^{\circ}C$]. Then this was produced as sheets after pressing for 20 minutes at 180[$^{\circ}C$] with a pressure of 200[kg/cm]. The contents of conductive acetylene black were 20, 30 and 40[wt%], respectively. The modulus experiment was measured by DMA 2980. The ranges of measurement temperature were from -50[$^{\circ}C$] to 100[$^{\circ}C$] and measurement frequency is 1[Hz]. The modulus of specimens was increased according to an increment of acetylene black content. And modulus was rapidly decreased at the glass transition temperature. The tan$\delta$ of specimens was decreased according to an increment of acetylene black content.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.703-708
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• 2002

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is an elastomeric hollow cylinder which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the load applied to the shaft or sleeve and the relative deformation of Elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation fur elastomeric bushing is important fur dynamic numerical simulations. A boundary value problem for the bushing response leads to the load-displacement relation which requires complex calculations and is hence unsuitable. Therefore, by modifying the constitutive equation for a nonlinear viscoelastic incompressible material developed by Lianis, the data fur the elastomeric bushing material was obtained and this data was used to derive the new load-displacement relation fur radial response of the bushing. After the load relaxation function for the bushing is obtained from the step displacement control test, Pipkin-Rogers model was developed. Solutions were allowed for comparison between the results of Modified Lianis model and those of the proposed model. It is shown that the proposed Pipkin-Rogers model is in very good agreement with Modified Lianis model.

• The Korean Journal of Rheology
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• v.9 no.4
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• pp.163-173
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• 1997

Polystyrene/polycarbonate 조성이 약 50/50인 3종류의 Poly(carbonate-g-styrene) 공중합체의 동적 탄성율, E*($\omega$)와 동적 스트레인-광학계수 O*($\omega$)을 유리전이 영역부근의 여러온도에서 동시에 측정하여 연구하였다. 두 개의 공중합체는 각각의 스티렌 그라프트쇄 에 5, 10 wt%의 MAH를 함유하고 있다. 이들 공중합체의 E*($\omega$)와 O*($\omega$)완화거동과 그라 프트 공중합체의 상용성과 연관하여 비교 고찰하였다. 공중합체들의 E*($\omega$)는 전형적인 무 정형 고분자의 유리전이 완하거동을 보였으며 정성적인 차이를 발견할수 없었다. 그러나 고 강도의 단일 tan$\delta$분산의 저주파수 영역에 미세분산을 나타내, 공중합체는 2상으로 분리되 어 있음이 추정되엇다. 폴리스티렌 그라프트체에 무수 말레인산 함유량이 증가함에 따라, 저 주파수 영역의 미세피크가 $\alpha$주분산에 병합되어 성분 고분자간의 상호 형동성이 증가함을 알수 있었다. 3공중합체의 유사한 기계적 특성과는 달리, 광학적 완화 스펙트럼 O*($\omega$)는 정 성적으로 명확한 차이를 보여 공중합체들의 광학완화 거동이 명확히 다름을 나타냈다. 기계 적 특성보다는 광학적 특성이 공중합체내의 성분 고분자의 미세한 완하 거동에 훨씬 민감한 응답을나타냈다. 이러한 특성적인 공중합체의 O*($\omega$)차이를 공중합체의 조성단일 고분자 PS, PC의 O*($\omega$)의 가성성을 가정하여 모사하였다 모사에서 구한 광학적 부분 기여 파라메 터를 사용하여 공중합체의 상용성을 고찰하였다.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.2
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• pp.16-21
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• 2004

An elastomeric bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. The relation between the load applied to the shaft or sleeve and the relative displacement of elastomeric bushing is nonlinear and exhibits features of viscoelasticity. A load-displacement relation for elastomeric bushing is important fur dynamic numerical simulations. A boundary value problem fur the bushing response leads to the load-displacement relation, which requires complex calculations. Therefore, by modifying the constitutive equation for a nonlinear viscoelastic incompressible material developed by Lianis, the data for the elastomeric bushing material was obtained and this data was used to derive the new load-displacement relation for radial response of the bushing. After the load relaxation function for the bushing was obtained from the step displacement control test, Pipkin-Rogers model was developed. Solutions were allowed for comparison between the results of the modified Lianis model and those of the proposed model. It was shown that the proposed Pipkin-Rogers model was in very good agreement with the modified Lianis model.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.125-131
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• 2022

The microstructure of highly aggregated colloidal dispersions was investigated by probing the rheological behavior of magnetic suspensions. The dynamic moduli as functions of frequency and strain amplitude are shown to closely resemble that of colloidal gels indicating the formation of network structure. The two types of characteristic critical strain amplitudes, γ_c and γ_y, were characterized in terms of the changing microstructure. The amplitude of γ_c indicates the transition from linear to nonlinear viscoelasticity and depends only on particle volume fraction not magnetic interactions. The study of scaling behavior suggests that it is related to the breakage of interfloc, i.e., floc-floc structure. However, yielding strain, γ_y, was found to be independent of particle volume fraction as well as magnetic interaction. It relates to extensive deformation resulting in yielding behavior. The scaling of elastic constant, G_e, implies that this yielding behavior and hence γ_y is due to the breakage of long-range interfloc interactions. Also, the deformation of flocs due to increase strain was indicated from the investigation of the fractal nature.