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Optical Methods in Metrology: Point Methods
Published in Daniel Malacara-Hernández, Brian J. Thompson, Advanced Optical Instruments and Techniques, 2017
Zacarías Malacara-Hernández, Ramón Rodriguez-Vera
Optical manufacturing has several ways to measure a radius of curvature, including templates, spherometers, and test plates. Templates are rigid metal sheets with both concave and convex curvature cuts at opposite faces (Figure 5.5). Templates are brought into direct contact with the sample. A minimal light space must be observed at the contact point. If the space between surfaces is small, the light between surfaces turns blue, due to diffraction. A template has the simplicity that it can be made in a mechanical shop with appropriate measuring tools, but it is also commercially available. For a more precise curvature measurement, a spherometer is used. Essentially, a spherometer measures the sagitta in a curved surface. Assume a bar spherometer, as shown in Figure 5.6 [18]. For a leg separation y and a ball radius r, the radius of curvature R can be obtained from the sagitta z: R=z2+y22z±r, where the plus sign is used for concave surfaces and minus for convex surfaces. The uncertainty in the measurement is found by differentiating the previous equation: ΔR=Δz2(1−y2z2).
The effect of degree of curvature and fabric orientation on the impact properties of single and multilayer textile composites
Published in The Journal of The Textile Institute, 2022
Mohammad Irfan, Bilal Zahid, Sheraz Hussain Sidique, Hafsa Jamshaid, Abdul Waqar Rajput, Aiqin Hou
To have the composites in a specific and calculated curvature, the molds were designed according to the required size and shape. It was done by using the plaster of paris and by employing an interesting method. The thick solution of plaster of paris was prepared and filled in balloons by the help of a pressure pump. The filling was done up to a specific volume so that different curvatures can be achieved. The diameter of blown balloons was measured and then the balloons were tied up. Later on, the balloons were hanged freely for about a day to allow the solution of plaster of paris become fully solidify. The next day balloon was burst and the mold in specified curvature was obtained. Spherometer was used here to measure and ensure the required degree of curvature. The systematic way of mold preparation is represented in Figure 1. Later the mold was smoothly finished and a wooden sheet of round shape was cut and placed at the bottom of each curvature to support the handling of mold. By using the same methodology, three molds were fabricated with the curvatures of 5, 10, and 20 m−1. For the flat composites, flat glass sheets were used instead of molds.