Effect of Dimension Parameters on the Torsion Property of A C/SiC Pipe

Through finite element numerical simulation and based on laminated plate theory, the effect of dimension on the torsion properties of uniform C/SiC composites pipe was studied to provide a theoretical guidance for preparing the C/SiC pipe with different dimensions. The results show that, with increasing length of pipe, the anti-torsion section coefficient of pipe increases whereas the torsion angle per unit length decreases. Increasing the length can improve the torsion property. Anti-torsion section coefficient rises with increasing internal radius, while the torsion angle per unit length decreases to a constant. With increasing thickness, the anti-torsion section coefficient increases whereas the amplitude decreases gradually, and the torsion angle per unit length is a constant. Increment of internal radius and thickness improves the torsion property finitely.

Torsion properties of poly (glycolide-co-L-lactide) biodegradable braided regeneration conduits for peripheral nerve repair

BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, greatly influence nerve regeneration and functional recovery. OBJECTIVE： To observe the influence of conduit parameters and coating methods on torsion properties in an in vitro-degradation environment and at normal temperature. DESIGN, TIME AND SE＇I-FING： An in vitro, comparative study using repeated measures was performed at the College of Textiles, Donghua University, China from January 2005 to December 2007. MATERIALS： PGLA fiber and yarn （Shanghai Bio-TianQing, China）, as well as torsion property testing instrument （LaiZhou Electronic Instrument, China）, were used in the present study. METHODS： A total of 16 types of conduits were constructed according to braiding structures （regular/triaxial）, angles （50°/55°/60°/65°）nd coating methods （coated/uncoated）. At normal temperature, torsion properties of all conduits were tested at a predefined constant angle of 90°. Coated and uncoated conduits, which were triaxial and 65°, were incubated in a 5% CO2 incubator at 37 ℃ to simulate an in vitro degradation environment, and then torsion properties were tested at 4, 7, 11, 14, 17, 21,24, and 28 days in culture. MAIN OUTCOME MEASURES： Maximal torsion strength and torsion strength-torsion angle curve of conduits at normal temperature, as well as torsion strength-torsion angle curve, loss of torsion strength, and change in maximal torsion strength in an in vitro degradation environment. RESULTS： At normal temperature, the torsion properties of the triaxial structure were superior to the regular structure. Coated conduits performed better than uncoated ones, and the larger braiding angles exhibited superior torsion properties （P 〈 0.05）. In the in vitro degradation environment, with degradation time, torsion strength of uncoated conduits was deceased gradually and the loss of torsion strength was increased fast. Torsion strength of coated conduits was increased first and decreased afterwards; the loss of torsion strength was decreased slowly till 14 days; both became identical after 14 days （P 〉 0.05）. CONCLUSION： Torsion properties of coated conduits with a triaxial structure and large braiding angle were superior to uncoated conduits with regular structures and small braiding angles.

TORSIONAL PROPERTIES OF METALLIC NANOSPRINGS

Based on molecular mechanics and the embedded-atom potential, the torsional mechanical behaviors of metallic copper nanosprings are investigated in this paper. The torsion coefficient of the nanospring is obtained by fitting the curve of potential energy versus torsion angle according to a parabolic law. It is found that the geometry of nanospring has a strong influence on the torsion coefficient. With the increase of the wire radius and the helix radius, the torsion coefficient of the nanospring increases. However, it decreases with the increase of the helix pitch and turns. It is also found that the classic spring theory is invalid to torsional nanosprings. The calculated torsion coefficient is higher than the predication from the classic spring theory and is lower than that of the corresponding solid rod. In addition, the continuum mechanics is shown to be inapplicable to describe the torsional behavior of nanosprings. These findings might provide a better understanding of the usability and functionality of nanosprings in nanodevices.

Test analysis on prestressed concrete composite beams with steel boxes subjected to torsion and combined flexure and torsion

While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or international literature on the an- ti-torque and composite torque properties of this type of beam. With the aim of understanding the torque properties of these beams, this paper presents results of ten comprehensive tests; three of these were based on stirrup spacings and prestressing levels as the main parameters, while the other seven were based on torsional rates. The torsion tests were conducted on the re- sults which established several key parameters, including curves of constant torsion, strain curves of steel torsion, strain distri- bution of steel beams and concrete, curves of bending-moment and mid-span deflection, as well as cross strain distribution.The prestressing impact-factor method was adopted to deduce semiempirical equations for cracking torque in such composite beams. Furthermore, this involves the use of the equation of ultimate torque based on tress-model-theory of the distortion an- gle, the calculated results show good agreement with the measured values. In summary, this paper offers theoretical analysis for future applications of HSC composite beams with PS boxes, and provides both validation of the methods employed and a reference point for on-going research on composite beams and related anti-torque studies.

Ultra-low-carbon steel spheroidization and torsion

Spheroidizing annealing and torsion testing of 0.027 wt% carbon steel rod were conducted to evaluate spheroidization kinetic behavior at 943 K （670 ℃） under deformed and non-deformed states. Kinetic curves were also predicted using the Johnson-Mehl-Avrami-Kolmogorov equation, and the results agree well with the experimental ones. After spheroidization was performed twice, the spherical cementite and precipitated carbides became smaller and the distribution was more uniform. Comparison of materials subjected to single and double spheroidizing annealing indicated a difference in grain size. Torsion performance was considerably improved under double spheroidization, especially the maximum torque with slight variations.

Effects of microstructure on the torsional properties of biodegradable WE43 Mg alloy

Torsional properties are important performance parameters for bone screw applications,but they are seldom studied,especially for newly developed biodegradable Mg alloys.In this study,WE43 Mg alloy with different microstructures was achieved by equal channel angular pressing(ECAP)and heat treatment,and their torsional properties were studied.In addition,tensile properties were also tested as a comparison.The results indicated that grain refinement led to higher torsional strength and ductility,while the second phases improved the torsional strength but reduced the ductility.The texture was strengthened after ECAP,as a result the tensile strength increased,but the torsional strength did not increase and even decreased,especially for 2-pass ECAP sample with a typical basal fiber texture.The basal plane orientation deviation from the extrusion direction after 4-pass ECAP resulted in higher torsional strength and lower torsional ductility,but lower tensile strength and higher tensile ductility were obtained.This implied that a strong fiber texture would reduce the torsional strength but improve the torsional ductility,which was different from its effect on tensile properties.