China
Africa
Explore chapters and articles related to this topic
Cutting Cylindrical Surfaces
Published in Hassan El-Hofy, Fundamentals of Machining Processes, 2018
5.7 In a turning operation of 90 mm diameter to 85 mm using feed rate 0.4 mm/rev, the ratio of main cutting force (Fv) to feed force (Fa) to radial force (Fr) is 5:2:1, respectively. The specific cutting resistance is 3,000 N/mm2, and the rotational speed is 150 rpm. Calculate The resultant cutting forceThe main cutting powerThe feed powerThe motor power in kW if the mechanical efficiency is 0.90
Machine Tools
Published in David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, 2018
David A. Stephenson, John S. Agapiou
Linear motors or direct drives (Figure 3.48) eliminate the mechanical transmission system required with rotary motors [6,158–160] since they combine the functions of the ball screw and motor. They are made with permanent or induction type magnets; induction magnets generally provide better performance and reliability. The force is transmitted through a magnetic field instead of a mechanical linkage. Because they are noncontact devices (except in the way system), they exhibit little wear and require less maintenance. Also, they can run at high speeds (up to 120 m/min) with high acceleration/deceleration characteristics (1-1.5 g) and eliminate deflections, backlash, and windup since bearings and ball nuts are not used. They can provide higher tool feed rates (almost twice that of ball screws) with equivalent or increased accuracy when compared with traditional ball screw systems since they can be controlled using many times the gain of their rotary counterparts [161]. The length of travel does not affect the performance of a linear motor as it does a ball screw. However, they have a comparatively low dynamic stiffness and limited load capabilities. Linear drives have traditionally been limited to applications with relatively small cutting forces (<5000 N) [161]. Higher forces can be achieved by placing separate drives in parallel. They require special machine designs and heat dissipation approaches due to their low mechanical efficiency. Linear drives used on horizontal beds should be carefully sealed to prevent swarf contamination in the track, which can degrade performance. Linear motors are not superior to ball screws in all cases [162] but are used for high-speed machining applications not possible with other systems or for large machines made for very large dies, molds, and aerospace parts.
Introduction
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, MECHANICAL DESIGN of Machine Components, 2018
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
The mechanical efficiency, designated by e, of a machine may be defined as follows: () e=PoweroutputPowerinput
Experimental investigation on the performance and emission characteristics of a diesel engine powered with waste mango seed biodiesel blends
Published in International Journal of Ambient Energy, 2022
B. Prasanth Kumar, K. Appa Rao, V. Dhana Raju, S. Rami Reddy, D. Mallikarjuna Rao, J. Subba Reddy
Figure 7 shows the variation of mechanical efficiency with brake power for all the tested fuel samples used in this investigation. Mechanical efficiency is generally defined as the ratio of brake power to the indicated power of the engine. The value of mechanical efficiency is always higher for the efficient operating engines. It is shown in the graph when the brake power is increased, mechanical efficiency is also increased. It is found that the mechanical efficiency of mango seed oil blend MSME20 (72.23%) at full load condition is nearer to that of diesel (75.72%). From the graph, it is also noticed that MSME20 shows higher mechanical efficiency than the other blends of MSME. The mechanical efficiency for the tested fuels of MSME10, MSME20, MSME30, MSME40, MSME50 and MSME100 at full load conditions is 69.89%, 72.23%, 67.49%, 66.84%, 65.48,% and 63.75%, respectively. It is noticed that MSME20 has shown higher mechanical efficiency at full load than other biodiesel blends.
Assessment of waste plastic oil blends on performance, combustion and emission parameters in direct injection compression ignition engine
Published in International Journal of Ambient Energy, 2019
Hariram Venkatesan, Seralathan Sivamani, Kunal Bhutoria, Harsh H. Vora
Mechanical efficiency is the measure of useful work performed by the system with the input of fuel and energy. Figure 12 shows the variation in mechanical efficiency for all fuel blends at all loads. From the plot, it can be noticed that there was a constant increase in mechanical efficiency with increasing load for straight diesel and PO blends. PO30% blend showed marginally better efficiency at low and part load due to higher ignition delay resulting in enhanced premixed combustion period and poor atomisation of fuel at high loads. The mechanical efficiency of straight diesel and PO15% blend was found to be 67.72% and 69.84% at full load condition.