Papers by Keyword: Pre-Tension

Abstract: Welding distortion remains a significant challenge in vehicle structures incorporating aluminum components. This study investigates the application of pre-tension to mitigate welding distortion in an aluminum T-joint structure. Through finite element (FE) simulation, the mechanism by which pre-tension alters the residual stress state and reduces distortion is analyzed and comprehensively explained. Based on the findings, an optimized pre-tension condition is proposed to minimize welding distortion in the T-joint configuration.

Abstract: Bolting and anchoring products are mostly pre-tensioned after their putting into the construction. Pre-tensioning force is a force with clearly defined size and direction and helps the construction to transfer loads. After pre-tensioning a cable bolt some pre-tension losses occur immediately after releasing the jack and other losses progress during their working time. These losses may occur due to the mechanical properties of the cable bolt and its structure itself, but also due to the properties of the surrounding rock mass.The article deals with the enumeration and description of individual losses in accordance with applicable legislation and their measurements both in the laboratory and in actual mining conditions. The comparison of calculated and measured losses and a brief overview of pre-tensionable bolting technology within OKD coal deep mines is a part of the content as well. The result of the tests is quantification of these types of pre-tension losses including proposals for their reduction.

Abstract: The paper reviews the theory of technical evaluation of the containment and the experience of using the mobile geodetic diagnostic system at the nuclear power plant unit No. 4 of Rostov NPS. The paper considers the results of a regular built-in system designed to determine and evaluate the strain-stress state of containments during the acceptance in service, commissioning stage and operating period. A comparison with the results of the geodetic system obtained at the same stages of containment existence.

Abstract: An experimental investigation into projectile penetration of pre-tensioned woven fabric samples – Tawron^® CT 717 (plain weave) – is undertaken. Specimens are clamped at their top and bottom edges, and pre-stretched by forces of 200N, 1000N, 2000N, 3000N and 4000N respectively. They are then oriented at various angles (0, 7.5°, 15° and 30°) from the vertical (perpendicular to the horizontal axis of a gas gun), and subjected to impact by a 12mm diameter steel sphere. A high-speed camera is utilized to observe the deformation and failure of the fabric, and to determine the residual projectile velocity. For normal incidence, the ballistic limit initially increases, then decreases with pre-tension, displaying a maximum resistance for a pre-tension of about 2000N. With respect to the angle of incidence (obliquity of impact), for target inclinations of 7.5° and 15°, pre-tension has minimal influence on the ballistic limit, while for an inclination of 30°, the effect of pre-tension on the ballistic limit is similar to that for normal impact.

Abstract: This paper presents and discusses the possibility of improving the bending strength of timber beams through the use of prestress. The emphasis is put on various methods of imposing the prestress force and transferring it into the wood part: i) through post-tension, with the force being mechanically anchored on the ends of the wood elements; ii) through pre-tension, with the anchorages being either mechanical, as in the previous system, or glued, with the force being gradually transferred through shear stresses along a certain length of the wire/wood interface. Although the risk of failure due to tension perpendicular to the grain in the anchorage regions exists, it is not specifically studied in here, due to the limited scope of the study. The main conclusion is that any of the procedures may be advantageously used with either small (mass-production) or large-span glued-laminated timber beams and, though they are mostly suited to the production of new elements, they may also be adapted to the strengthening of existing beams.

Abstract: Since the pre-stressed anchor technology became to be used from the beginning of twentieth century, it is widely used with the advantages of its good applicability, high cost performance, good looking appearance and easy green. Pre-stressed anchor achieves the purpose of actively controlling foundation pit deformation by exerting pre-stress on steel strand of its free section. This thesis chooses deep foundation pit engineering, adopt Mohr-Coulomb ideal soil body by finite difference software FLAC3D, and select different anchor pre-tension values to simulate. It combines Lizheng software to do numerical simulation and analytic study on pile-anchor supporting structure. This thesis compares results coming from the two kinds of software, and analyze the impact on row piles' body bending moment, pile top deformation, anchor cable axial force and foundation pit deformation when pre-tension changes.

Abstract: The structure design of the tension cable in monolayer cable net curtain wall is very important. Generally the diameter and initial pre-tension of the tension cable is identified via iterative computing in the past works. This paper proposes a simple computing method for this case, which not only quickly computes the maximal internal force of the tension cable by the known deflection limit and identify the diameter of the tension cable, but also deduces the initial pre-tension of the tension cable and assist engineers to analyze and calibrate the tension cable and guide field tension construction.

Abstract: In this paper, the influence of pre-tension on elongation percentage at specified load for knits was studied .First of all, initial elongation and elongation percentage at specified load for different retractility knits were tested and analyzed at different pre-tension. And then significance of influence of pre-tension on initial elongation and elongation percentage at specified load for knits were analyzed by means of variance analysis. Results show that the pre-tension has significant influence on initial elongation for different retractility knits, and it has no significant influence on elongation percentage at specified load for little retractility knits, and it has significant influence on elongation percentage at specified load for well retractility knits. The greater the pre-tension is, the more significant the influence is, Therefore it is suggested that pre-tension is generally less than 0.1N in the test.The research results can provide a certain reference to stretch and recovery test for knits and test standard recension .

Abstract: By applying the elastic pre-tension method, 5A05 aluminium alloy sheets with 4mm thickness were welded. It is shown that the peak value of residual stresses and their distribution vicinity, the longitudinal buckling distortions and plane deformations of specimens after welding under pre-tension were obviously reduced. It is considered that pre-tension counteracts the compression stress in regions close to the weld generated by thermal expansion, consequently reduces the compression plastic deformations and the tensile stresses in these regions when cooling down, and accordingly diminishes the compressive stresses far from the weld.