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A mechanical displacement control model tunnel for simulating eccentric ground loss in the centrifuge
Published in Andrew McNamara, Sam Divall, Richard Goodey, Neil Taylor, Sarah Stallebrass, Jignasha Panchal, Physical Modelling in Geotechnics, 2018
G. Song, A.M. Marshall, C.M. Heron
A single bi-directional screw shaft is placed at the tunnel centerline, fixed by two ball screw supports located on either side (front and back) of the strongbox. Two flange nuts are secured on the screw shaft in opposite directions. Each flange nut is connected with a hexagonal wedge shaped shaft (see Figure 2). The hexagonal wedge shaped shaft consists of six faces with different taper angles, which are varied from 4° at the tunnel crown to 0° at the tunnel invert. Six arch shaped tunnel segments are connected to the two opposing hexagonal wedge shaped shafts via two linear guide rails to generate the tunnel circumference. Each segment is equipped with two linear carriages, secured to the opposing wedge shaped shafts. The linear guide rail with linear carriage enables the relative movement between the six segments and the two shafts along the taper angle. A stepper motor linked with a 10:1 ratio gearbox drives the screw shaft via a flexible coupler, which permits some degree of misalignment between the screw and gearbox shafts. Tunnel volume loss is achieved by rotating the bi-directional screw shaft, causing the two hexagonal wedge shaped shafts to move apart from each other, and the six segments to move towards the tunnel centerline. Due to the differences in taper angle, the non-uniform tunnel boundary displacement profile is formed.
Methods of joining
Published in Andrew Livesey, Alan Robinson, The Repair of Vehicle Bodies, 2018
The locking collar is an integral part of the Cleveloc nut, but in the flange nut the locking element is integral within the nut and has no collar. They are precision formed to a geometric ellipse and provide two locking elements of uniform shape and thread contour. These locking elements utilize most of the threads that come within the depth of the collar (on the Cleveloc nut) or the element (on the flange nut) and distribute locking pressure over wide areas. This ensures high fatigue life, with the flexibility necessary to give consistent performance and dependability in service.
Control Valves
Published in Douglas O. J. deSá, Instrumentation Fundamentals for Process Control, 2019
To minimize the possibilities of a premature failure, it is suggested that preventative measures be implemented when the installation is being designed. The following tabulates, in direct relationship to the foregoing listing, methods for avoiding the stated problems: Select a valve with a low-pressure recovery trim, or install a secondary flow restrictor, or relocate the valve to a more favorable position.Wet steam, but most often hot steam condensate, is the cause of eating away of the carbon steel of the valve body beneath the stainless steel ring of the seat when there is no gasket or weld seal. In these applications, use or specify stainless steel or chromium-molybdenum alloy valve bodies.Use hardened trims or angle valves. Angle valves are suggested for flashing condensate at the inlet of a condenser, and for erosive fluids. In erosive fluid service, use a reduced trim and a long straight oversized pipe run on the downstream side of the valve. Furthermore, in this case the fluid flow should be in the direction that does not cause the valve plug to lift.Reversing the flow direction sometimes eliminates this problem; alternatively, a larger stem diameter and reduced weight of the plug can be a solution.Make a better selection of valve construction materials with the aid of corrosion tables.There are numerous causes for excessive stem packing leakage, some of which are: Valve has a loose packing flange nut when shipped from the manufacturer.Hot fluid service. A possible solution is to retighten packing after valve has been warmed up.Rotating the actuator before or without loosening the stem packing, or unstable control over extended periods causing wear resulting in leakage.Higher coefficient of expansion of the packing compared with the other materials used.Total effective packing length less than the full length of stem travel; it must be greater.Stem misalignment.
Anti-loosening mechanism of pitch difference bolt nut connections based on Junker loosening test
Published in Mechanics Based Design of Structures and Machines, 2022
Nao-Aki Noda, Biao Wang, Yoshikazu Sano, Ryo Kawano, Yuto Inui, Xi Liu, Yasushi Takase
There are mainly two methods widely used for preventing nut loosening. One is to use special washers, and the other is to change the shape of the nuts (Bhattacharya, Sen, and Das 2010; Gong, Liu, and Feng 2022; Panja and Das 2016, 2017; Samanta et al. 2012). Sawa et al. conducted a series of Junker loosening experiments by varying washers with M12 nut shapes (Sawa, Ishimura, and Yamanaka 2006; Shoji, Sawa, and Yamanaka 2007). It was found that loosening prevention performance was improved by using plate washers, spring washers, toothed washers, and Nord lock washers compared to normal bolt-nut connections without them. Like a washer, a flange nut has a wide flange surface at the bearing nut side, usually with a serrated shape, which contributes to anti-loosening. It was reported that 110 percent of the tightening torque is required to loosen the flange nut (Barrett 1990). Flange nuts are mainly used for wood and plastic. Slotted nut, also known as Castle Nut, has some slots on the free nut end side, and they are usually used together with a pin. This type of nuts is suitable for situations when the initial tightening torque needed is small (Barrett 1990). Super lock nut (SLN) is a kind of wire inserted nut and is widely used in industries such as transportation and bridges provided by Fuji Seimitsu Co. Different from the common nut, this type of nut can be reused several times. Since a spring is inserted in the thread, the loosening energy can be absorbed and transferred to a locking torque when vibrating the bolted joints.