• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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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.

• International Journal of Precision Engineering and Manufacturing
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• 제5권2호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.273-276
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• 2008

Thermoplastic resin takes place stress relaxation and creep according to temperature and time. In room temperature, time dependent deformation (TDD) of polymer was carried out at previous study. In this study, it evaluates time dependent deformation to relate temperature. Nanoscale indents can be used as cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. Therefore, it is important to control pattern depth for change of indent depth by creep when using Nanoindenter. For evaluating TDD at high temperature, it is occurred thermal-nanoindentation test by changing hold time at maximum load. Temperature is putted at $90^{\circ}C$, hold time at maximum loads are putted at 1, 10, 50, 100, 200, 300 and 500s.

• 한국구조물진단유지관리공학회 논문집
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• 제15권2호
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• pp.136-143
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• 2011

고력볼트의 현장 조립시 볼트 구멍 간의 불일치로 인하여 볼트 구멍을 확장하는 경우가 빈번하게 발생하고 있으며, 이를 위해서 외국 기준에서는 볼트 구멍 크기, 형태, 하중 방향에 따라 미끄럼하중에 대한 규정을 따로 두고 있다. 그러나 우리나라의 경우 과대구멍에 대한 시방규정이나 이에 대한 접합부 특성에 관한 연구는 미흡한 실정이다. 따라서, 접합부재 표면처리와 볼트구멍 크기의 변화가 접합부 내력에 어떠한 영향을 미치는 지를 실험을 통해 정량적으로 평가할 필요가 있다. 본 연구에서는 볼트 구멍 크기 및 형태에 따른 접합부의 미끄럼하중의 변화와 체결 후, 장기축력이완의 경향을 분석하기 위하여 160시간 및 800시간 동안 고력볼트의 축력의 변화를 측정하였다. 본 실험대상 고력볼트로 KS B 2819에 규정된 TS(Torque Shear)형 고력볼트를 사용하였다. 표준 볼트구멍 대비 그 외 볼트구멍의 미끄럼하중의 변화는 10% 미만으로 나타났으며, 장기축력이완은 직경 2.5배의 슬롯구멍에서, 2.66%로 가장 높게 나타났다.

• 한국지반공학회지:지반
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• 제14권5호
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• pp.39-52
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• 1998

본 논문은 정규압밀된 점성토 지반에서 강관 매입 말뚝의 수평 거동에 영향을 미치는 여러인자들 중에서 말뚝의 근입길이, 지반조건(건조단위 중량 $\gamma_4$), 말뚝 두부의 구속조건의 영향에 관하여 모형실험을 수행하였으며, 이러한 영향을 정량화 할 수 있는 경첩식을 그 결과들로부터 얻었다. 모형실험에 사용한 지반은 3종류의 정규압밀 점토이다. 2종류의 말뚝 근입길이와 말뚝 두부의 고정 자유조건의 모형실험결과들에 의하여 수평하중-변위 관계는 $\gamma_d/\gamma_{dmax}$=0.84 이하에서 완전 탄소성체의 거동형상을 보일 것으로 나타났으며, 각 실험에서 최대 수평하중(Q--) 이후의 수평하중 감소는 상당한 시간 의존성을 보였다. 본 연구에서는 수평 하중-변위관계(logo-logy/D)와 최대 휨 모멘트-변위관계($loaM_{max}$.-.-logy/D)에서 각각 구한 항복 수평하중(Qy)과 항복 최대 휭 모멘트(My)가 직선적인 관계로 밝혀졌다. Relaxation에 의한 수평하 중은 모형실험 결과들로부터 시간을 변수로 한 지수 함수식으로 회귀분석 하였다. 수평 극한하중과 항복하중에 대한 지반조건의 영향은 $\gamma_4$$/\gamma_{dmax}$의 변수로 한 지수함수식으로 모델화 하였으며, Broms와 Budhu et at.에 의한 결과와의 비교에서 예측결과가 26-78%정도 과대평가 되었다. 수평하중-변위 관계에 대한 말뚝 두부의 고정조건 영향에서 $Q_{mxed}/Q_{free}$-y/D의 관계는 상당히 비선형적으로 나타났으며, yiD를 변수로 한 지수함수식으로 모델화하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제25권5호
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• pp.8-14
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• 2021

포스트텐션 프리스트레스트 콘크리트 부재는 즉시 손실 이외에도 크리프, 건조수축 및 릴렉세이션과 같은 시간적 손실이 발생한다. 아울러 상부 슬래브 또는 포장 등의 교체 등에 의한 고정하중 변동으로 인하여 부재 상하부의 응력이 변화하게 된다. 이러한 응력의 변화는 부재의 안전성에 영향을 줄 경우가 있으며, 이 경우 프리스트레스 힘의 조절이 필요하다. 따라서 이 연구에서는 나사를 적용한 새로운 유형의 재긴장 포스트텐션 정착구를 제안하고, EAD160004 및 KCI-PS101에 규정된 하중전달시험을 통하여 하중에 대한 안전성과 변형률에 대한 안정성을 만족함을 구명하였다.

• 대한기계학회논문집A
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• 제25권4호
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• pp.619-628
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• 2001

A viscoelastic constitutive equation of rubber is proposed under small oscillatory load superimposed on large static deformation. The proposed model is derived through linearization of Simos nonlinear viscoelastic constitutive model and reference configuration transformation. Statically pre-deformed state is used as reference configuration. The model is extended to a generalized viscoelastic constitutive equation including widely-used Mormans model. Static deformation correction factor is introduced to consider the influence of pre-strain on the relaxation function. The model is tested for dynamic behavior of rubbers with different carbon black fractions. It is shown that the constitutive equation with static deformation correction factor agrees well with test results.

• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.151-160
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• 1996

The fatigue test under the constant amplitude repeated loading is performed to investigate the fatigue behavior of the Torque Shear type high tension bolted joint which is able to manage the axial force uniformly. From the test results, it's known that the reduction of the axial force of T/S bolt followed by the elasped time is similar to that of the high tension bolts. The difference of relaxation is not occurred according to the position of bolts, the size of the introduced axial force but the effect of the variation of temperature is large. In the reduction of the axial force followed by the cumulation of the fatigue load, the outer bolt is larger than the inner bolt. This result depends on the difference in the distribution of the non-slip zone. The variation of the surface roughness affects the slip and the reduction of the anal force.

• 한국정밀공학회지
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• 제22권11호
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• pp.118-124
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• 2005

An automotive 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 a 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 force applied to the shaft and the relative deformation of a bushing is nonlinear and exhibits features of viscoelasticity. In this paper, an automotive bushing is regarded as nonlinear viscoelastic incompressible material. Instron 8801 equipment was used for experimental res earch and ramp-to-constant displacement control test was used for data acquisition. Displacement dependent force relaxation function was obtained from the force extrapolation method and expressed as the explicit combination of time and displacement. Pipkin-Rogers model, which is the direct relation of force and displacement, was obtained and comparison studies between the experimental results and the Pipkin-Rogers results were carried out.

• 대한통합의학회지
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• 제10권1호
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• pp.129-136
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• 2022

Purpose : The purpose of this study was to investigate the effect of applying intensity on the muscle activity and muscle hardness of the upper trapezius muscle in adult males when TENS (transcutaneous electrical nerve stimulation) was applied. In addition, this study intends to prepare the scientific basic data of TENS for the purpose of relaxation based on the experimental results. Methods : Eighty-seven healthy adult males participated in the experiment, and they were randomly divided into an experimental group and a control group. All subjects in this study were healthy subjects without musculoskeletal or nervous system damage. All subjects were subjects who voluntarily consented to the purpose and method of the experiment. All subjects were provided with a load by typing for 20 minutes, and muscle activity and muscle hardness of the upper trapezius muscle were measured immediately. Afterwards, TENS was given to each groups for 15 minutes, and the experimental group received stimulation at the motor threshold level, and the control group received a placebo stimulation. After stimulation, muscle activity and muscle hardness of the upper trapezius muscle were measured in the same method. The measured data were compared between groups through an independent t-test and dependent t-test. The statistical significance level was set at .05. Results : The application of TENS statistically significantly decreased the muscle activity and muscle hardness of the trapezius muscle in the experimental group, and the results showed a significant difference from the control group. Conclusion : Application of TENS significantly decreased the muscle activity and muscle stiffness of the upper trapezius muscle. The application of TENS of applying intensity that induces muscle contraction may induce relaxation by reducing the muscle activity and muscle hardness of the trapezius muscle.