• Structural Engineering and Mechanics
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• 제59권3호
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• pp.527-537
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• 2016

We describe a stress analysis of a single leaf flexure under torsion in which the warping effect is considered. The theoretical equations for the warping normal stress (${\sigma}_{xx}$) and shear stresses (${\tau}_{xz}$ and ${\tau}_{xy}$) are derived by applying the warping function of a rectangular cross-sectional beam and the twist angle equation that includes the warping torsion. The results are compared with those of the non-warping case and are verified using finite element analysis (FEA). A sensitivity analysis over the length, width, and thickness is performed and verified via FEA. The results show that the errors between the theory of warping stress results and the FEA results are lower than 4%. This indicates that the proposed theoretical stress analysis with warping is accurate in the torsion analysis of a single leaf flexure.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.146-153
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• 2005

Structural design of the torsion beam rear suspension is investigated by calculating warping of the torsion beam. Since the longitudinal displacement in the cross section of the torsion beam due to torsional moment causes normal stress across the beam restrained from outside at both ends, the profile of torsion beam needs to be designed considering the warping. Warping function of the beam is derived with the parameters of cross section fur the arbitrary shapes of torsion beam profiles assuming thin-walled open section. From comparing the warping calculated for two different beam profiles, the design method for the torsion beam in the view point of low stress is discussed. It is shown that the gusset used to reinforce the torsion beam can be optimized in accordance with warping shape. The method to fix the end point of the gusset is proposed to minimize the stress concentrated on the end point of the gusset produced during torsional moment. The result from finite element analysis shows the stress is minimized when the height of gusset end point is coincident with the point where warping of the beam is minimized.

• 한국해양공학회지
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• 제25권6호
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• pp.80-85
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• 2011

The Ultrasonic Nanocrystal Surface Modification (UNSM) technology improves the fatigue life of a torsion bar by inducing compressive residual stress on the surface layer. The UNSM is applied to replace the presetting method and shot peening technology. The torsion bar must be changed periodically because of a lack of durability and a phenomenon related to the stress relaxation. The torsion fatigue test specimens were made of DIN17221 material, and the results showed that the fatigue life was 5 times more than under durability test conditions. A comparison test between the commercial vehicles' presetting method and shot peened torsion bar and the UNSM torsion bar showed that the UNSM could replace the presetting method and shot peening.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.123-128
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• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evaluation of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. Stress analysis was conducted of the inside of a hollow cylinder in the axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• 한국생산제조학회지
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• 제7권5호
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• pp.46-52
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• 1998

In fracture problems, stress intensity factors obtained theoretically and experimentally have been effectively utilized in the analytical evolution of the cracks effect. The effect of surface crack of a cylindrical and a hollow cylindrical bar is investigated, as well as the effect of the thickness of a hollow cylindrical bar and inclined crack of a hollow cylinder subjected to torsion moment. In this study, stress intensity factor Km of mode III which expresses the stress state in the neighborhood of a crack tip is used. stress analysis was conducted on the inside of hollow cylinder inthe axial direction of three dimensional crack tip subjected to torsion moment by combining the caustics method and the stress freezing method.

• Structural Engineering and Mechanics
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• 제10권2호
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• pp.165-180
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• 2000

An analytical model with tension softening for the prediction of the capacity of prestressed concrete beams under pure torsion and under torsion combined with shear and flexure is introduced. The proposed approach employs bilinear stress-strain relationship with post cracking tension softening branch for the concrete in tension and special failure criteria for biaxial stress states. Further, for the solution of the governing equations a special numerical scheme is adopted which can be applied to elements with practically any cross-section since it utilizes a numerical mapping. The proposed method is mainly applied to plain prestressed concrete elements, but is also applicable to prestressed concrete beams with light transverse reinforcement. The aim of the present work is twofold; first, the validation of the approach by comparison between experimental results and analytical predictions and second, a parametrical study of the influence of concentric and eccentric prestressing on the torsional capacity of concrete elements and the interaction between torsion and shear for various levels of prestressing. The results of this investigation presented in the form of interaction curves, are compared to experimental results and code provisions.

• 한국지반공학회지:지반
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• 제4권1호
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• pp.17-28
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• 1988

흙의 역학적거동을 파악하기 위한 요소시험중 공시체의 주응력방향을 회전시킬 수 있는 비틀림 전단시험기의 기능에 대하여 검토하였다. 본 연구에서는 이 비틀림전단시험기가 점토시료에 사용 될 수 있게 개량제작되었다. 이 시험기를 사용하여 반죽성형된 Ko-견밀점토시료에 대한 약간의 비배수 비틀림전단시험을 실시하여 혼의 거동에 미치는 주수력축의 회전영향이 조사되었다. 우선, torque없이 비틀림전단시험기를 사용하여 얻은 흙의 역학적 거동이 통상의 축대칭삼축압 축시험에 의한 결과와 비교검토됐다. 흙의 응력일변형거동, 문극수압및 주응력비는연직하중과 torque에 의한 응력경로에 크게 영향을 받았으며 전단변형률의 증가에 따라 주응력회전각과 주응력의 상대적 크기, b(=o2-o3)/(o1-o3)) 값토 점진적으로 커져 파괴시의 값에 수렴하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.352-361
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• 2003

A fatigue damage accumulation model based on the continuum damage mechanics theory was develope(1 where modules decay ratios in tension and shear on used as indicators for damage variables D . In the model, the damage variables are considered to be second-order tensors. Then the maximum principal damage variable, $D^*$ is introduced According to the similarity to the Principal stress, $D^*$ is obtained as the maximum eigen value of damage tensor [D']. Under proportional tension and torsion loadings, fatigue lives were satisfactorily predicted at any combined stress ratios using the present model in which the fatigue characteristics only under uniaxial tension and pure torsion loadings on needed. Fatigue life prediction under uniaxial tension and pure torsion loadings, was performed based on the damage mechanics using boundary element method.

• 한국공작기계학회논문집
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• 제13권6호
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• pp.64-73
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• 2004

A fatigue damage accumulation model based on the continuum damage mechanics theory was developed where modulus decay ratios in tension and shear were used as indicators for damage variables D. In the model, the damage variables are considered to be second-order tensors. Then, the maximum principal damage variable, $D^*$ is introduced. According to the similarity to the principal stress, $D^*$ is obtained as the maximum eigen value of damage tensor [D]. Under proportional tension and torsion loadings, fatigue lives were satisfactorily predicted at any combined stress ratios using the present model in which the Fatigue characteristics only under uniaxial tension and pure torsion loadings were needed. Fatigue life prediction under uniaxial tension and pure torsion loadings, was performed based on the damage mechanics using boundary element method.

• Structural Engineering and Mechanics
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• 제73권1호
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• pp.75-82
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• 2020

In this study, the problem of torsion of bars with open cross section surrounded by corrugated boundaries is analyzed. An approximate analytical solution is given using perturbation technique. First, the stress analysis for circular open cross-section for arbitrary opening angle is formulated and the problem is analytically solved. Second, the open cross-section with corrugated cross section is analyzed using perturbation method. First order contributions to the stresses and the torques have been added. The results have been exemplified and compared by considering special examples.