Method of Achieving Accuracy of Thermo-Mechanical Treatment of Low-Rigidity Shafts

Abstract

The paper presents a method combining the processes of straightening and thermal treatment. Technological processes with axial strain were considered, for the case of heated material and without its heating. The essence of the process in the case of heated material consisted in the fact that if under tension all longitudinal forces in the first approximation are uniform -the same strains are generated. The presented technological approach, aimed at reducing the curvature of axial-symmetrical parts, is acceptable as the process of rough, preliminary machining, in the case of shafts with the ratio L/D≤100 (L -shaft length, d -shaft diameter) and without a tendency of strengthening. To improve the accuracy and stability of geometric form of low-rigidity parts, a method was developed that combines the processes of straightening and heat treatment. The method consists in that axial strain -tension, is applied to the shaft during heating, and during cooling the product is fixed in a fixture, the cooling rate of the shaft being several-fold greater than that of the fixture. A device is presented for the realisation of the method of controlling the process of plastic deformation of lowrigidity shafts. In the case of the presented device and the adopted calculation scheme, a method was developed that permits the determination of the length of shaft section and of the time of its cooling.

Technology of Heat Treating-Straightening of Long Shafts With Low Rigidity

“…Analysis of the technology of manufacturing of long shafts with low rigidity, and in particular of the operation of heat treating-straightening [6,7,13], revealed that the drawback of the known technological approaches is the impossibility of keeping the product -shaft -at the state of tension when the temperature is decreased to 20°С, as the fixture is compressed faster than the shaft. Because the walls of the fixture (layered tube or sleeve) are thin (fixture cools down several-fold faster), a gap is formed between the face of the dissected clamping sleeve, which causes the release of the product during cooling, and the appearance of an uneven distribution of inner compressive forces.…”

“…Shaft-type parts with low rigidity are used in many contemporary machines, fixtures and other devices [1,6,7,8,10,11,12,13,14]. The continuous growth of production of low-rigidity shafts is determined by the growing production of precision machines.…”

Molybdenum Sheet Local Resistance Heating Test Device

“…The heat is generated on the microscale when the conduction by the drawing electrons transfer energy to the conductor's atoms by way of collisions [3,6]. The heat can be generated e. g. in resistance wires and it is transferred to the heated object by the conduction, convection and radiation [4,21].…”

Analysis of Typical Structures of Dynamic Systems of Machining of Elastic-Deformable Shafts With Low Rigidity

“…The problem of machining low-rigidity shafts was widely discussed in the literature. There are many publications concerning the problem of stability lobes [2÷23], definition of cutting conditions [4,18], machining forces and error prediction [16,17], surface quality modelling [1,7,11,19] or chatter suppression [15]. Moreover, the problem of simulation of low-rigidity part machining was in the special interests of researchers [5,9,15].…”