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Sheet Metal Parts—I
Published in Godfrey C. Onwubolu, Introduction to SOLIDWORKS, 2017
Bending is a common metalworking technique to process sheet metal, as shown in Figure 18.1. It is usually done by hand on a box and a pan brake, or industrially on a brake press or a machine brake. The typical products that are made like this are boxes such as electrical enclosures and rectangular ductwork. Usually, bending has to overcome both tensile stresses and compressive stresses. When bending is done, the residual stresses make it spring back toward its original position, so we have to overbend the sheet metal keeping in mind the residual stresses. When a sheet metal is bent, it stretches in length. The bend deduction is the amount that the sheet metal will stretch when bent as measured from the outside. A bend has a radius. The term bend radius refers to the inside radius. The bend radius depends upon the dies that are used, the metal properties, and the metal thickness.
Sheet and plate metalwork
Published in Roger Timings, Fabrication and Welding Engineering, 2008
Generally, the position of the neutral line is 0.4 times the thickness of the metal in from the inside of the bend. Therefore, the radius used for calculating the bend allowance is equal to the sum of the inside bend radius plus 0.4 times the thickness of the metal. Furthermore, the bend radius is rarely less than twice the metal thickness and rarely more than four times the metal thickness. Therefore, for all practical purposes, when calculating the required length of a thin sheet-metal blank when forming cylindrical or part cylindrical work, the mean circumference is used. That is, the neutral line is assumed to be the central axis of the metal thickness. It is only when working with thin plate and thick plate that the neutral line needs to be calculated more accurately. The terminology used when bending metal is as follows: Bend radius – the inside radius of the bend.Outside bend radius –the inside radius of the bend plus the metal thickness.Bend allowance – the length of the metal required to produce only the radius portion of the bend.
Forming and Shaping Processes
Published in Richard L. Shell, Ernest L. Hall, Handbook of Industrial Automation, 2000
Bending is a common sheet-metal process achieved using a press brake. The ability of a material to undergo bending is characterized by its bend radius. The bend radius depends on the ductility of a material and the sheet thickness. The outer fibers in bending are typically subjected to tension and the inner fibers are put in compression. This makes the determination of the neutral axis very important. Compensation must also be provided for springback or the elastic recovery after bending. Bent products abound in applications, automobile and aircraft bodies serving as principal examples. Casings and bodies for home airconditioners and refrigerators, and boxing for packaging and storage containers all illustrate bending at various angles and varying sheet thicknesses. Bending also serves in certain applications where the principal purpose is to increase the moment of inertia and stiffness of parts. Material is typically clamped and bent at the desired places with a die.
Void Fraction of Air-Water Two-Phase Flows in a Vertically Placed Horizontal U-Bend
Published in Heat Transfer Engineering, 2023
Kosuke Hayashi, Shosuke Yasui, Ryo Kurimoto, Akio Tomiyama
de Oliveira and Barbosa [10] measured void fractions of air-water two-phase flows at the inlet and outlet of U-bends by using an electrical capacitance method. The pipe diameter, D, was 26 mm and the dimensionless bend radius of curvature, DB* (= 2 RB/D), ranged from 6.1 to 12.2, where RB is the bend radius of curvature. The bend was placed in the vertical plane and the void fractions in the upward and downward flows were obtained. The void fraction in the bend was evaluated as the mean of the inlet and outlet values. They reported that the Chexal et al. [13] correlation for straight pipes gave better agreement with their data than the Smith [14] and Premoli et al. [15] correlations, though the agreement with the data was not sufficient. The deviation from the data could be caused by neglecting the effects of bending. Usui et al. [9] pointed out that for upward flows the bend void fraction is similar to that in a straight pipe. On the other hand, in downward flows, the bend void fraction is larger in the bend than in the straight pipe, especially when the centrifugal force in the bend is weak compared with the gravitational force. Their experiments were carried out for D = 16 mm with RB = 90, 132.5 and 180 mm and D = 24 mm with RB = 135 mm. Hence, 5.6 ≤ DB* ≤ 11.25. Although Usui et al. [9] developed a correlation for the bend void fraction in downward flows, which is expressed in terms of the void fraction in the straight pipe and the bend Froude number, the correlation has not been sufficiently assessed yet mainly due to the lack of experimental data, especially for small D used in practical application, e.g., air-conditioning systems.
Flow analysis in right-angled pipes with different geometric shapes and parameters for sludge discharge in slime shield machines measured using a CFD-DEM method
Published in International Journal for Computational Methods in Engineering Science and Mechanics, 2020
Lumin Chen, Kaixuan Liu, Yufeng Yao, Jun Yao, Zixue Su, Guofu Luo
Figure 8 shows the proportion of the number of collisions and the number of contacts between the particles and the pipe wall. For both curves 1 and 2, the results showed a tendency of decrease and then increase. For curve 1, when the transitional pipe bend radius was changed to 0.6 − 1.5, the proportion reaches a minimum value. For curve 2, when the pipe bend radius was 2 times of the pipe diameter, the proportion was the lowest. Subsequently, it increases monotonically with the increase of pipe bend radius.
In-bend pressure drop and post-bend heat transfer for a bend with a partial blockage at its inlet
Published in Numerical Heat Transfer, Part A: Applications, 2018
J. M. Gorman, E. M. Sparrow, C. J. Smith, A. Ghosh, J. P. Abraham, R. Daneshfaraz, A. Rezazadeh Joudi
The geometry was based on the experimental results reported in references [14,15]. The pipe diameter was 48 mm and the straight section of pipe extended 480 mm beyond the exit of the bend. The bend radius of curvature is 2.8 times the diameter. The inlet boundary for the numerical simulation was located 0.58 diameters upstream of the bend because the available data (velocity profiles and turbulence intensities) are reported at that location.