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Iron Bridges
Published in Robert Routledge, Discoveries and Inventions of the Ninteenth Century, 2018
To test the stability of the bridge, fifteen heavy pieces of artillery, accompanied by fifty horses and 300 people, were made to traverse it at various speeds, and the results were entirely satisfactory. Indeed, a few years afterwards the people of Fribourg had another wire bridge thrown over the gorge of Gotteron, at about a mile from the former. This, though not so long (640 ft.), spans the chasm at a great height, and in this respect is probably not surpassed by any bridge in the world—certainly not by any the length of which can compare with its own. The height of the roadway above the valley is 317 ft., or about the same as that of the golden gallery of St. Paul’s Cathedral above the street. The structure is very light, and the sensation experienced when, looking vertically downwards through the spaces between the flooring boards, you see the people below diminished to the apparent size of flies, and actually feel yourself suspended in mid-air, is very peculiar, as the writer can testify.
EEMS2015 organizing committee
Published in Yeping Wang, Jianhua Zhao, Advances in Energy, Environment and Materials Science, 2018
The primary failure mode of unreinforced wall was the separating between block and mortar joint which cause the loss of structural integrity under blast loads. But in the reinforced test wall, the pri- mary failure mode was the vertical and diagonal cracks which occurred at the mortar joints and completely traverse the thickness of the blocks. The primary crack propagated completely from the top to the bottom of the wall, and developed furca- tion at the center of the wall due to the one-way flexure mode of text wall and the shear strain on the bottom half. In the explosive test of clay brick wall, the presence of polyurea layer improved the flexure resistance of test wall due to the increase of the effective tangent modulus of reinforced wall (Urgessa and Maji, 2009, Blazynski, 1987). Further- more, the polyurea increased the blast resistance of test wall due to the highly pressure sensitive and the stiffness increasing remarkably with increasing pressure (Amini et al., 2010a, Amini et al., 2010b). Consequently, a part of impact energy was trans- ferred to the polyurea and dissipated in the defor- mation of the polyurea layer. The fully reinforced wall appeared to be much stronger and more rigid than partially reinforced.
Recoil Arresting and Recoilless Guns
Published in Donald E. Carlucci, Sidney S. Jacobson, Ballistics, 2018
Donald E. Carlucci, Sidney S. Jacobson
The first approach to getting around the recoil mass is commonly employed by trench mortars. These are described in the introduction as man-portable cannon than cannot fire a flat trajectory at all. The reason is simple. Most mortars are fired off baseplates that couple the recoil forces directly to the soil beneath them. A ball socket interface between the breech of the cannon and plate allows traverse and elevation of the cannon. They are limited to fire at elevations no less than 45°. The base plates are typically circular and employ vertical projections or grousers that bite into the soil to better hold the baseplate in place. If the firing elevation were made a little bit too shallow, the baseplate would shift during firing and introduce accuracy errors. If fired far too low, rapid disemplacement of the cannon and baseplate would ensue presenting a hazard.
A sustainable ecofriendly additive manufacturing approach of repairing and coating on the substrate: cold spray
Published in Australian Journal of Mechanical Engineering, 2022
Abdul Faheem, Ankit Tyagi, S. M. Pandey, Faisal Hasan, Qasim Murtaza
In this study, copper particles were sprayed onto structural steel substrate, meanwhile, investigated the deposition and coating aspects. Spherical Cu particles were utilised on cleaned Mild steel (MS) plates with a mirror surface in the experimental approach. Procedure parameters, for example, carrier gas, pressure and temperature are well controlled to yield higher micro-metallic particle deposition. The convergent-divergent de Laval type conical-shaped nozzle was used in this investigation. The extension proportion of the nozzle was 9, and the downstream length from the throat to the exit was 100 mm. The standoff separate from the exit of the nozzle to the substrate surface was 20 mm. The shower or spray conditions for the Cu powders were 2.7 MPa injection pressure, nitrogen as a carrier gas and temperature of 27°C. The shower gun was controlled by a robot and moved at a traverse speed of 500 mm/s over the substrate surface to acquire the disfigured or deformed particles on the cleaned surface. The surface and the cross-sectional morphologies of the deformed particles of particle and substrate were observed by using a scanning electron microscope (SEM), Jeol Ltd in University sophisticated instruments facility, Aligarh Muslim University, Aligarh, India. For inert gas-atomised copper powder with particle sizes ranging from 10 to 20 m, a critical velocity of around 500 m/s was achieved. The different results clearly explained that particles with a velocity above the critical one created a successful coating on the mild steel substrate.
A review on characteristics of cold sprayed coatings
Published in Australian Journal of Mechanical Engineering, 2022
Akella Srikanth, Venkateshwarlu Bolleddu
Gas temperature and pressure: These are two important parameters for a successful deposition of the coating. If the temperature of powder particles increases the influence of critical velocity is in a negative manner. Always the powder particles pressure should be high to attain the spraying velocity. Insignificant changes in parameters affect the coating deposition efficiency (Srikanth, Mohammed Thalib Basha, and Venkateshwarlu 2020).Gun traverse speed: The volume of deposited powder particles will be decided through the traverse gun speed. Lower deposition rate will occur with higher amount of traverse gun speed whereas a higher deposition rate will be noted with a lesser amount of traverse gun speed (Santos da Silva et al. 2017).Spraying distance: It is the gap between spray gun nozzle and surface of the substrate. In cold spray process, the maximum spraying distance should be 50 mm whereas in remaining thermal spraying methods it’s ranging from 120 to 300 mm (Suegama et al. 2007).Spraying angle: The coating microstructure, thickness and deposition efficiency will be affected by the spraying angle. This can be separated into three ranges: First is deposition with a spraying angle of 90°. Second is deposition with an angle varying in between 40º and90º and 100% coating deposition efficiency. The last one is with a spraying angle of less than 40° (Li, Li, and Wang 2003).Substrate temperature: It can also influence the coating performance. If the substrate temperature is very high at the time of spraying, thermal softening between the particles and substrate will come about and decreases the particle velocity during contact with the substrate (Ernst et al. 2012).
Electrostatic powder coating process optimisation by implementing design of experiments
Published in Transactions of the IMF, 2021
When the literature is reviewed, there are a number of noteworthy studies. Mountain and Mazumder2 studied powder coating variables. They used RSM to optimise first pass transfer efficiency which is affected from air flow and voltage. Luangpaiboon3 used paint flow rate and ring air pressure to optimise paint thickness by RSM. Luangpaiboon et al.4 applied the full factorial design, RSM and Taguchi methods. They tried to investigate the optimum factor level in order to improve the quality of performance of an automotive manufacturing industrial paint shop. Farzaneh et al.5 studied the influence of anionic surfactant sodium dodecyl sulphate (SDS), pH, substrate finishing, and annealing temperature, on the hardness of electroless nickel phosphorus (ENi-P) coatings and the surface morphology. They used the Taguchi method. Singhtaun and Prasartthong6 applied factorial design in a powder coating study and determined the optimum levels for the cleaning time, chemical concentration and shape of hanger (which is a jig for hanging the component to be powder coated). Banubakode et al.7 used the Taguchi method to determine the optimum factor levels of voltage, powder flow rate, booster air flow rate to reduce the DFT and orange peel texture of the coating. They also tried to determine the appropriate powder type. Karidkar and Mali8 studied powder spray process optimisation. They also used the Taguchi method to optimise, in their study, the coating thickness and coating microstructure. For this purpose, they determined the optimum factor levels of gun stand-off distance and gun traverse speed. Chidhambara et al.9 applied the Taguchi method to optimise paint flow, shaping air, viscosity to achieve optimum DFT. Goud et al.10 utilised RSM to determine the optimum levels for the voltage, distance between the tip of the gun and the reinforcement or towpreg (which are pre-impregnated reinforcement fibres), and the velocity of the carbon towpreg. Liu et al.11 applied RSM to determine the optimum levels of argon gas, power, spraying distance, and powder feeding amount.