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Initiation of Ignition in Ammunition
Published in Ajoy K. Bose, Military Pyrotechnics, 2021
Heat is generated, on providing electric impulse to wire, which is more than the ignition temperature of the squib composition. The resistance wire generally used is nichrome, platinum -iridium, platinum- rhodium, tungsten, cupro-nickel etc. which have high and uniform specific resistance; without kinks/twist; with higher melting point than ignition temperature of squib composition and low specific heat for ignition of squib composition even at lower electrical energy. The energy (E) generated by resistance wire is given by E=i2Rt where i = current in amperes, R = resistance in ohms/metre, t = time in seconds.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Wire-wound resistors are power wire wounds or precision wire wounds. In either case the resistance wire is either a nickel-chromium alloy with a resistivity of 1.33⋅10-4ohm-cm for high resistance values, or a copper-nickel alloy with a resistivity of 5⋅10-5ohm-cm for lower resistances. Power wire wounds are intended to operate at higher power dissipation and are composed of single layers of bare wire with substrates and packages of high-temperature materials. Precision resistors are stable, highly accurate components. The wire is multilayered, and therefore must be insulated, and all materials can be low temperature The main disadvantages of wire-wound resistors are the high cost and low operating frequency.
Properties and Applications of Molybdenum
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
The second is based on the molybdenum-tungsten alloy system. A series of molybdenum-tungsten alloys has been developed primarily for use as hooks in high wattage lamps, supports and springs in discharge tubes, and heaters in radio tubes. These alloys are also used as resistance wire in high temperature electric furnaces. Besides this alloy series, mention may also be made of a particular alloy composition consisting of molybdenum with 30 wt% tungsten. This alloy composition was originally developed to take advantage of the high melting point of tungsten to result in an alloy with a melting point higher than that of molybdenum. It has been found that this alloy is not attacked by molten zinc. For this reason the alloy is seen to be in extensive use in zinc handling equipment for parts such as impellers, tundishes, and thermocouple protection tubes.
Investigation of heat transfer and damage characteristics of high pressure abrasive water jet impacting high temperature sandstone
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Jianguo Zhang, Yingwei Wang, Jianming Shangguan, Zehua Niu, Rui Min
For metal ores buried at greater depths (>3 km), the ore rock temperatures typically exceed 100°C. In order to approximate the real deep ground high-temperature environment, the experiments were set up with three sets of sandstone heating temperatures of 250°C, 300°C and 350°C. The heating device is SX2–10-12A box muffle furnace. The device adopts resistance wire heating element for heating, and the maximum temperature can reach 1200°C. It has the characteristics of subsection setting of heating path, real-time measurement and display of furnace temperature and continuous adjustable heating rate. The rock samples are first heated to a preset temperature at a heating rate of 60°C/h to prevent thermal shock to the rock during the heating process (Chen et al. 2012; Yin, Li, and Li 2019), and after heating to the target temperature, they are kept at a constant temperature in the furnace for 2 hours to ensure uniform heating of the rock.