Torsion—Resistant Structures: A Nature Addressed Solution

The complexity of torsional load, its three-dimensional nature, its combination with other stresses, and its disruptive impact make torsional failure prevention an ambitious goal. However, even if the problem has been addressed for decades, a deep and organized treatment is still lacking in the actual research landscape. For this reason, this review aims at presenting a methodical approach to address torsional issues starting from a punctual problem definition. Accidents and breaks due to torsion, which often occur in different engineering fields such as mechanical, biomedical, and civil industry are considered and critically compared. More in depth, the limitations of common-designed torsion-resistant structures (i.e., high complexity and increased weight) are highlighted, and emerge as a crucial point for a deeper nature-driven analysis of novel solutions. In this context, an accurate screening of torsion-resistant bio-inspired unit cells is presented, taking inspiration specifically from plants, that are often subjected to the torsional effect of winds. As future insights, the actual state of technology suggests an innovative transposition to the industry: these unit cells could be prominently implied to develop novel metamaterials that could be able to address the torsional issue with a multi-scale and tailored arrangement.

Dynamic Response of an Inhomogeneous Elastic Pile in a Multilayered Saturated Soil to Transient Torsional Load

In this paper, we solve the dynamic response of an inhomogeneous elastic pile embedded in a multilayered saturated soil and subjected to a transient torsional load via a semianalytical method. To portray the inhomogeneity of the pile and the stratification of surrounding soil, the pile-soil system is subdivided into Nth layers along the depth direction in view of the variation of shear modulus or cross-sectional dimension of the pile or differences in soil properties. Then, the vibration displacement solution with undermined constants for any saturated soil layer subjected to the time-harmonic torsional load is obtained by virtue of the separation of variables scheme. To establish the connection of adjacent longitudinal soil layers, the circumferential contact traction at the interface of the adjacent layers is treated as the distributed Winkler subgrade model independent of the radial distance. Then, by utilizing the continuity conditions of the pile-soil system and the method of recursion typically used in the transfer function technique, the torsional impedance of the pile top can be derived in the frequency domain. By virtue of inverse Fourier transform and convolution theorem, the velocity response of an inhomogeneous pile subjected to a transient half-sine exciting torque and embedded in a layered saturated soil is gained in the time domain. Finally, selected numerical results are gained to investigate the influence of typical defects in pile and soil layering on the velocity response of the pile top in the time domain.

DYNAMIC STRUCTURAL ANALYSIS OF ENGINE CRANKSHAFT AT DIFFERENT ANGLE OF CRANK TURNS FOR THREE DIFFERENT MATERIALS

For many years, engines have been one of the main power machinery of different kinds of applications, and the main part of power machinery is a crankshaft that converts the piston’s reciprocating displacement with four-link mechanisms into rotary motion. . The major limitation of the engine crankshaft is fatigue failure due to repeated load caused by bending and torsional load. In this paper, the comparative dynamics structural analysis was carried out for three different materials such as forged steel, cast iron, and chromium-molybdenum steel with different angles of turns of cranks from 0° to 720° and to predict the stresses, deformation, and fatigue life of crankshaft without compromising its weight, strength and reliability. The 3D CAD model was simulated with FEA software. The simulated results show that by applying bending load and torsional load for three materials, the maximum stresses produced in the fillet area of the main bearing journal and in the fillet area of the crankpin journal at a crank angle of 360° respectively. The deformation results revealed that maximum deformation occurs at the mid-surface of the crankpin. From fatigue life prediction it was observed that forged steel and chromium-molybdenum steel shows better fatigue life as compared to cast iron. Moreover, in the comparative study, it was concluded that chromium-molybdenum steel shows fewer stresses and better fatigue life. Therefore it is suggested that chromium-molybdenum steel would be the better option for manufacturing crankshaft.

In vitro comparison of the torsional load transfer of various commercially available stainless-steel wires used for fixed retainers in orthodontics

Objective: To assess the torsional load transfer of various commercially available stainless-steel wires used for fixed retainers. Design: An in vitro study using a robotic device. Setting: Department of Pediatric Oral Health and Orthodontics, University of Basel. Methods: A 10° proclination of a maxillary lateral incisor of a 2-2 retainer was simulated with a robotic device. Eight stainless-steel wires with different shapes (round or rectangular), types (plain, braided, coaxial or chain) and dimensions were selected to measure the torsional load transfer at the adjacent central incisor. The influence of annealing was also tested. Results: The 0.016 × 0.016 and Bond-A-Braid™ wires (0.02645 × 0.01055-inch, 8-stranded, braided) showed the largest relative torsional load transfer (3.7% and 3.3%, respectively). The two multistranded wires - Triple Flex™ and Respond® - showed the smallest values of 1.0% and 0.7%, respectively. The spiral direction of these two multistranded wires affected the load transfer, the twisting showing larger torsional load transfer than the untwisting one. Conclusion: The effective torsional load transfer depends on the dimension, shape and type of a wire. Plain and braided retainers were more predictable in torsional load transfer than multistranded retainers, which may have stored more energy in the area between the composite bonding sites. This may explain the unexpected complications reported in multistranded retainers.