In this study that spur gears are chosen, contact stress of spur gear is presented under the effect of rotational speed. Three-dimensional simulation of dynamic analysis of gears designed and modeled using ANSYS software. The dynamic analysis included in the determination of dynamic stresses analysis. Contact stress is theoretically calculated and analyzed and numerically estimated using both Hertzian mathematical model and finite element method respectively. Different values of rotational speed used to study its effect on contact stress. Both methods compared by evaluating the percentage error of contact stress, and the modeling of the spur gear and stress analysis of spur gear carried out using SOLID WORK and ANSYS V14, respectively. The most significant note in this study concludes that increasing speed causes vibration and pitting failure due to repetitions.

This paper presents a study of vibration characteristics in headstock of a lathe machine, at different cutting parameters. These parameters are the cutting speed; the depth of cut lnq the feed rate .The transducer were used on the heidstock in two directions, the vertical and horizontal (feed) direction, Also for a time domain of (l0sec) in both directions. The results show that the effect of the vertical vibrations is more significanf than the horizontal (feed) direction, for all of the cases investigated in this paper. Unlike the veriical vibration, the horizontal vibration is lower and steadier, when the cutting speed, ine Oepttr of cut and the feed rate are increased, Whereas the vertical vibration shows a great fluctuation when these parameters are increased.

In metal cutting studies, the flank wear width (VB) is commonly used as a criterion or as a limit measure for the cutting tool life. From the point view of this work, there is a critique concerning the traditional limit measure (vB). The researchers in this domain do not take the diameter of the work-piece into consideration. In this situation, the contact angle, between the tool and the work-piece, should be determined from the limit measure of flank wear width. This work deals with the effect of the work-piece diameter on the limit measures and proposes a related limit measure for each diameter' For the experimental approach, certain confirmation tests were achieved. It seems that the work-piece diameter could modify the limit measure and it could be increased for large diameters, or decreased for small ones.