Increase In Efficiency Factor Research Articles

Research of working capacity of pulsed variable-speed drives

The paper presents the results of experimental researches of the basic working capacity characteristics of pulsed variable-speed drives - gear ratio, efficiency factor, and reliability of the eccentric free-wheel mechanisms When conducting research, the main working capacity parameters of the pulsed variable-speed drive (independent factors) changed according to the design of experiment in the range: the load applied to the output shaft was from 250 to 2.750 N·m; adjustable gear ratio - from 20 to 180. It was established that the reliability of the eccentric free-wheel mechanisms is guaranteed when making mechanisms of 100Cr6 steel with hardness not lower than HRCЭ 58…62 with a module of at least 0.75 mm. It was shown that the yield surface, which characterizes the change in the gear ratio of the pulsed variable-speed drive, can be described by a model using first-order polynomials. It was established that with increasing load, a slight increase (at 1.0...9.9%) occurs in the adjusted gear ratio, which has a character close to linear. It was concluded that with an increase in load, the increase in efficiency factor is non-linear and equals 1.8...2.6 times, an increase in the gear ratio causes its linear decrease by 1.13...1.64 times in the dependence close to a linear one. Empirical dependences are obtained to determine the magnitude of the gear ratio and efficiency factor.

Whither Transverse Reinforcement in Bottle-shaped Struts?

Recommendations in many of the current design codes like the Eurocode and the AASHTO LRFD Bridge Design Code discount the effect of transverse reinforcement on strength of bottle shaped struts whereas the mechanics of the force system within a bottle-shaped strut suggests otherwise. In this investigation, the effect of amount of transverse reinforcement on strength of steeply inclined normal-strength and high-strength concrete bottle-shaped struts measured in terms of efficiency factors has been experimentally investigated for three transverse reinforcement ratios - 0.0031, 0.0046 and 0.0069, with the control bottle-shaped strut being transversely unreinforced. Efficiency factor increases of 31% and 25% in the normal-strength and the high-strength concrete bottle-shaped struts respectively were obtained when the transverse reinforcement ratio was increased from nil to 0.0031 whereas for the higher reinforcement ratios the increase in efficiency factor was relatively smaller. Service load crack widths in all the transversely reinforced struts were less than an upper bound value of 0.3 mm. The results of this investigation emphasise the role of transverse reinforcement in the strength of bottle-shaped struts and indicate that the 0.003 transverse reinforcement ratio recommended in the ACI 318-14 Building Code is the optimum amount of such reinforcement in normal-strength and high-strength concrete bottle-shaped struts.