Forming grinding of spur gears is to trim the grinding wheel into an outer profile exactly the same as the groove shape required for machining the gears and to grind the gears by means of the shaped surface of the grinding wheel.Forming grinding of teeth can produce accurate tooth profiles with high grinding efficiency and is usually the last step in gear machining.
Gears are widely used in practical engineering, but their fatigue failure is the most important factor for gear failure. Therefore, it is very important to study the surface integrity of the grinded gear.Residual stress is a major indicator of surface integrity and an ideal surface residual compressive stress can greatly improve the fatigue resistance of the tooth surface.
Mahdi M et al. considered the influence of grinding heat and grinding force on residual stress and established a calculation model for residual stress in plane grinding.
Yu et al. studied the influence of grinding heat on residual stress by assuming a moving rectangular heat source. He established a finite element model and the calculated results are in good agreement with the measured values.
Shah et al. established a two-dimensional finite element model for planar grinding, which considered that the phase transition generated at high temperature during grinding would have a great influence on the residual stress, and that the tensile stress could be formed on the grinding surface by selecting reasonable grinding parameters.
Maroju et al. studied the surface residual stress of Ti6Al4V alloy during vibration grinding and normal grinding through experiments, and established corresponding finite element model. The research observed that adding vibration assistance to normal grinding method can create indentation effect and increase residual compressive stress.
Fergani et al. calculated the thermal stress through Timoshenko thermal stress theory analysis, then applied the elastic-plastic relaxation condition to the stress, thus constructed the quantitative calculation function of the temperature influence on the residual stress, and finally carried out AI-SI.Grinding experiments on 52100 hardened steel verify the correctness of its function. Based on the model established, the initial temperature at which the grinding tensile stress occurs under certain grinding conditions and material properties can be calculated.
Kuschel et al. predicted the change of residual stress caused by grinding thermal shock through two-dimensional finite element simulation, then carried out grinding experiments and measured the temperature below the contact area. The research shows that during the process below the austenitizing temperature, the thermal load of material and the residual stress generated by dry grinding can be accurately predicted by the established model, and the temperature below the austenitizing temperature is given.Functional relationship between maximum surface temperature and surface residual stress in the direction of grinding at degrees.
At present, many researches on grinding residual stress are based on surface grinding, but the form grinding of gears is surface grinding, which is quite different from surface grinding. The grinding parameters at different positions on the involute are not constant.In this paper, firstly, the theory of form grinding is analyzed, and then a calculation model of residual stress on the surface of form grinding ofis put forward. Finally, the influence of grinding parameters on the residual stress on the tooth surface is analyzed by comparing experimental research with simulation calculation, which provides a reliable reference for the calculation of residual stress in form grinding.
(1) Based on forming grinding kinematics and thermo-mechanical coupling finite element simulation technology, a calculation method of residual stress in forming grinding is put forward, and the residual stress field distribution of tooth surface after forming grinding is obtained by calculation.
(2) Forming grinding experiment of spur gear is carried out, and the maximum relative error between the experimental value and calculated value of residual stress on tooth surface is found to be 14.9%, which verifies the proposed method to some extent.
(3) The research results show that the greater the feed depth, the smaller the residual compressive stress on the tooth surface formed by grinding, which provides theoretical reference for the selection of processing parameters of spur gear shape grinding.