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Those Magnificent Flying Machines and Their Internal Environment
Published in Harry W. Orlady, Linda M. Orlady, John K. Lauber, Human Factors in Multi-Crew Flight Operations, 2017
Harry W. Orlady, Linda M. Orlady, John K. Lauber
The jet age began with Britain’s ill-fated Comets, which had their first scheduled flight in 1952. Unfortunately, the Comets, which doubled the speed and altitude of existing transports, had a fatal design flaw. While the Comets met or surpassed all existing and predicted structural standards, its square windows developed small fatigue cracks at its corners. Round or oval shapes (like an egg) provide a stronger structure subject to less fatigue and stress cracking. The square windows on the Comet eventually gave way under the rapid changes in altitude to catastrophic fatigue failures that resulted from the Comet’s unusually fast climbs and descents. The result was a series of disastrous decompressions and the airplane was doomed. The US waited for the Boeing 707, which was first flown in 1958 and had its first scheduled trip in 1959. About a year later, the Douglas DC-8 flew its first trip. Both Boeing and Douglas had learned from the pioneering Comet’s problem, details of which, in the best tradition of air transport, had been provided to them by de Havilland. In this era, human factors was still very much secondary to engineering considerations. Pilots were simply expected to adapt to this new technological wonder. Those who could not adapt were restricted to propeller airplanes or eliminated.
Manufacturing Techniques
Published in Sumit Sharma, Composite Materials, 2021
This process is an automated one. This process is used in the fabrication of components or structures made with flexible fibers. This process is primarily used for hollow, generally circular- or oval-sectioned components. Fiber tows are passed through a resin bath before being wound onto a mandrel in a variety of orientations, controlled by the fiber feeding mechanism and rate of rotation of the mandrel. The wound component is then cured in an oven or autoclave. One can use resins like epoxy, polyester, vinyl ester, and phenolic along with any fiber. The fiber can be directly drawn from creel, nonwoven, or stitched into a fabric form. The filament winding process is shown in Figure 3.3.
Fatigue assessment of weld root failure of hollow section joints by structural and notch stress approaches
Published in J.A. Packer, S. Willibald, Tubular Structures XI, 2017
The approach is not only restricted to weld toes, but can also be applied to weld roots. The fictitious radius may be arranged as shown in Fig. 6, leading to a keyhole shape. This can result in a stress over-estimation in case of stresses parallel to the slit. Therefore, oval shapes are sometimes preferred. Alternative approaches using a smaller notch radius have been developed particularly for thin-walled structures used in the automotive industry, e.g. 0.05 mm (Eibl et al., 2003).
Geometrical Analysis of Oval Domes through Architectural and Mathematical Methods. The Case of the Dome of the Camarín of the Virgin of El Puig (Valencia, Spain)
Published in International Journal of Architectural Heritage, 2022
Esther Capilla Tamborero, Vicenta Calvo Roselló, M. Carmen Gómez-Collado
With regards to the dome, Table 1 shows the maximum distances of the data in each horizontal plane to the ellipse with semi-axes a and b obtained from these data and to the four-centered oval described in the methodology. It can be seen that the ellipse better approximates the data. These distances are calculated from each point to the corresponding curve, oval or ellipse. Obviously, for these calculations it was necessary to execute a great number of subroutines in Mathematica. To do this, we have used the Rigel cluster and the computers, working in parallel, of the Calculation Centre of the Universitat Politècnica de València. Without this technical support, it would have been impossible to perform the enormous quantity of calculations required in a reasonable computing time.
Stresses in flex gear of a novel harmonic drive with and without pay load
Published in Australian Journal of Mechanical Engineering, 2022
Vineet Sahoo, Bhabani Sankar Mahanto, Rathindranath Maiti
The conventional HD uses truncated involute teeth to avoid tip interference and loses conjugacy in gearing action as the pitch curve takes the shape of an oval due to the oval-shaped wave generator. To maintain conjugacy in gearing action new (split cam) wave generator has been proposed by Maiti (2004) and Maiti and Roy (1996). The main advantage of the split cam wave generator is that the deformed pitch circle of the FG cup becomes circular around the tooth contact regions separated by two elliptical arcs. This helps to maintain the gearing law around the tooth contact region. Consequently, conjugate gearing action should be achieved with involute gear teeth. Maiti et al. (2012) have also proved that it has higher contact ratio and there may have higher stresses where circular arc has changed to oval-shaped cam. Moreover, the synthesis of suitable tooth profiles (Kondo and Takada 1990; Kayabasi 2007) to work with the conventional oval-shaped cam is one of them. Furthermore, to examine the workability of HD with split-cam SWG, experiments were conducted (Mahanto and Maiti 2011; Biswas, 2005). In the rigorous experiments, the stress-strain analysis is done by placing strain gauges at various places on the FG cup wall surfaces (Mahanto, Sahoo, and Maiti 2018), but the results are limited to strain analysis due to split-cam SWG insertion only.
Effect of thickness on the buckling strength of egg-shaped pressure hulls
Published in Ships and Offshore Structures, 2018
Jian Zhang, Minglu Wang, Weicheng Cui, Fang Wang, Zhengdao Hua, Wenxian Tang
To resolve these disadvantages, researchers have advocated non-spherical pressure hulls, shells of revolution with positive Gaussian curvature, to replace the spherical one (Wong 2012; Blachut 2014). For instance, Jasion and Magnucki presented a numerical and analytical study into the elastic buckling of barrelled shells resembling Cassini oval (Jasion and Magnucki 2015a), clothoidal-spherical (Jasion and Magnucki 2015b) and circular arc (Jasion and Magnucki 2007; Magnucki and Jasion 2013) shapes. Moreover, Blachut proposed a family of shells of revolution in the shape of circular arc (Blachut 2002) and generalised ellipse (Blachut 2003). The elastic–plastic buckling of these shells was numerically and experimentally explored. However, these studies fall into a tentative stage, in which these non-spherical shells are not in match with the application maturity as spherical ones, and their applications into deep pressure hulls are not evaluated. Also, little attention has been paid on the effect of wall thickness on the buckling.