Papers by Keyword: Torsional Rigidity

Abstract: The objective of this study is to give an analytical solution for the Saint-Venant torsion of bars having cross section bounded by two hyperbola arcs. The solution of the problem is based on the theory of uniform torsion which was developed by Saint-Venant and Prandtl. The material of the bar is homogeneous, isotropic and linearly elastic.

Abstract: Box girders are now prominently used in freeway and bridge systems because of its structural efficiency, better stability, serviceability, economy of construction and pleasing aesthetics. Due to its high torsional rigidity box girders are most suited for curved bridges. In the present investigation, a comparative study of straight and curved box girder bridges with trapezoidal cross section has been carried out. The analysis is carried under the dead load, super imposed dead load, live load of IRC Class A tracked vehicle and prestressed load .This paper focus on the parametric study of box girders with different radius of curvature by keeping the span, cross sectional shape and material properties constant. The parametric investigations performed on curved box girders helps to evaluate the effects of change in radius of curvature on the behaviour of the box girders. This study would help the bridge engineers to better understand the behaviour of straight and curved box girder bridges. The results obtained from this study will be a valuable guidance to the bridge designers.

Abstract: To study structural characteristics of flying-wing vehicle, static and dynamic model of half wing span, static and dynamic model of all wing span, optimization model were established. Based on associated static test and ground resonance test data, these models were modified to implement static, dynamic and optimization analysis. Results demonstrated that structural bending and torsional deformations are mainly at outer wing surface. Torsion at inner wing is positive, while torsion at outer wing is negative. Total spar axial force along the wing span increases gradually from inner wing to outer wing and then decreases gradually after reaching the inner-outer wing interface. After axial force is transmitted to the inner wing, it is going to concentrate at the rear spar obviously. Structural bending rigidity and torsional rigidity satisfy requirements of both static force and flutter, without flutter problem of main structural mode. Viewed from the optimization size, ±45° and 0° skin at inner-outer wing turn thickens significantly. This can increase structural bending and torsional rigidity, which is good for satisfying multiple constraints comprehensively.

Abstract: The design of reinforced concrete beams has usually focused on the ultimate flexural capacity and disregarded the lateral stability of the beams. However, the development of high-strength concrete and the implementation of new construction techniques increase the use of longer and deeper concrete beams, which makes the lateral instability a primary concern of failure in concrete bridges. In particular, the lateral stability should be more taken into consideration in the construction and erection phases due to inadequate lateral supports. Thus, an experimental study was carried out to evaluate the lateral torsional buckling of reinforced concrete beams with initial geometric imperfections. The lateral flexural and torsional rigidity expressions, which could account for the flexural, torsional, and shrinkage cracking of concrete, the contribution of longitudinal and shear reinforcement, and the nonlinearity of materials, were proposed for rectangular reinforced concrete beams. Finally, this study proposed an analytical formula to estimate the buckling loads of initially imperfect reinforced concrete beams. The estimates of the study showed close agreement with the experimental values.

Abstract: In this paper, the torsional rigidity of micro-lattice plates is investigated using a FE analysis. In particular, the effect of the overall length of the plate and the unit-cell geometry on the torsional rigidity are discussed. Also, a theoretical approach, based on classical beam theory, for predicting the rigidity is proposed, and its effectiveness is verified by comparing with FE results.

Abstract: In frame structure, the Supports of secondary beam are frame beams or main beams, Support Beam rotation of the secondary beam to form certain constraints. General calculation method, for edge Supports, sometimes as fixed or hinged, the so-called “method of taking no account of torsion rigid”. In such cases, intermediate supports are usually as hinged, obviously not reasonable. We consider the torsional characteristics of all supports, according to torsional stiffness of the beam support. Therefore, we can become the continuous beam mode into the frame mode, so as to simplify the calculation, analyzed the influence of the torque, and should pay attention to the problem.

Abstract: We consider the Saint-Venant torsion problem of composite shafts. Two different kinds of imperfect interfaces are considered. One models a thin interphase of low shear modulus and the other models a thin interphase of high shear modulus. The imperfect interfaces are characterized by parameters given in terms of the thickness and shear modulus of the interphases. Using variational principles, we derive rigorous bounds for the torsional rigidity of composite shafts with cross-sections of arbitrary shapes. The analysis is based on the construction of admissible fields in the inclusions and in the matrix. We obtain the general expression for the bounds and demonstrate the results with some particular examples. Specifically, circular, elliptical and trianglar shafts are considered to exemplify the derived bounds. We incorporate the cross-section shape factor into the bounds and show how the position and size of the inclusion influence the bounds. Under specific conditions, the lower and upper bounds will coincide and agree with the exact torsional rigidity.

Abstract: System torsional rigidity is an important design index, having important influence on operating performance of the advanced actuator; therefore, this paper emphasizes the study on calculation of system torsional rigidity. This paper firstly introduces working principle and structural features of the novel ball screw transmission. Then uses commercial CAD and FEM softwares, SolidWorks and Cosmos/Works, fulfils deformation analytical computation for such three key parts as driveshaft, fixed guiding sleeve and straight-rotary sleeve. Next, sum up each term of torsional rigidity. Finally, makes a conclusion that the system torsional rigidity of the advanced actuator satisfies the designing demand.

Abstract: As high-speed steel tap is incapable of small-hole tapping (M3) in hardened steel, vibration tapping is introduced in this paper to solve this problem. Theoretic analysis with fracture mechanics indicates that the impact effect of the tap on the workpiece results in extended micro cracks and a much lower tapping torque. And the torsional rigidity of the tap is enforced in vibration tapping as proved by dynamic analysis. The experimental results show that with well chosen amplitudes, tapping torque decreases as vibration frequency increases and increases with the increase of net cutting time ratio, with the latter being the more significant influencing factor. In vibration tapping of hardened steel, 24 threads can be machined with a single tap. Vibration tapping is then proved to be a practical solution to the problem of small-hole tapping in hardened steel.

Abstract: The design of shaft coupling ensuring serviceability of an actuator under varying conditions is presented in this paper. The driving half coupling is an eccentric balanced over the axis of rotation. The torque of the coupling is determined by the parameters of the flexible ring and eccentricity. When the parameters of coupling are properly selected, the transfer coefficient of vibration can be reduced markedly.