Product design and Finite Element Analysis, GEARS

Gear teeth failure due to fatigue is a common
phenomenon observed. Even a slight reduction in the root
tensile stress results in great increase in the fatigue life of a
gear. If gear fails in tensile fatigue, the results are
catastrophic and occur with little or no warnings. Therefore
for all the r easons mentioned above, this work is of more
practical importance.  For many years, gear design has been
improved by using improved material, hardening surfaces
with heat treatment and carburization, and shot penning to
improve surface finish etc. Few more efforts have been
made to improve the durability and strength by altering the
pressure angle, using the asymmetric teeth, altering the
geometry of root fillet curve and so on. Most of the above
methods do not guarantees the interchangeability of the
existing gear systems. This work presents the possibilities of
using the stress redistribution techniques by introducing the
stress relieving features in the stressed zone to the
advantage of reduction of root fillet stress in spur gear. This
also ensures interchangeability of existing gear systems. In
this work, combination of circular and elliptical stress
relieving features are used and better results are obtained
than using circular stress relieving features alone which are
used by earlier researchers.  A finite element model with a
segment of three teeth is considered for analysis and stress
relieving features of various sizes are introduced on gear
teeth at various locations. Analysis revealed that,
combination of elliptical and circular stress relieving
features  at specific, locations are beneficial than single
circular, single elliptical, two circular or two elliptical stress
reliving features.

Nowadays, the main method of machining the gears with a module in the range 1-25 mm, which are integral parts of modern machines, remains hobbing. Operations of the toothed crown processing determine the efficiency of the entire technological process of manufacturing gears. Thus, the time expenses and performance, the cost of the gears, and their final quality depend to a large extent on these indicators in operations of hobbing. Considering the importance of this process for mechanical engineering, considerable attention of scientists is devoted to its modeling. Chip parameters are the key source of information required for comprehensive and complete analysis of the hobbing process. Despite the large number of publications devoted to this problem, there is still no methodology for adequate reproduction of these parameters. Known methods and models are characterized by significant simplifications and do not reproduce completely the kinematics of this complex process. This article presents a new approach to graphical modeling of the chip parameters in the hobbing process, which is based on the analysis and synthesis of elementary kinematic motions, related to unit motions and displacements of the hob cutting elements in the process of removing the metal in the gap between the teeth of the processed gear. The algorithm for forming the instantaneous transitional surface between the gear teeth and the three-dimensional (3D) space geometry of the chips on all active teeth of the tool is implemented in the graphic system AutoCAD. The article presents the results of computer modeling of chips in the climb and up-cut hobbing with Archimedean and convoluted hobs. Complete information on the geometric structure of the cut layers provides the basis for complex and system modeling of this process at the level of separate racks, teeth and edge of a hob. In combination with the data on the intensity of plastic deformation, stresses and temperature obtained for the corresponding conditions of hobbing in the Deform system, data on the parameters of the cut layers create opportunities for predicting the heating and wear of cutting elements of a hob, their loading, strength of protective coatings, transient processes of the cutting force and temperature, designing of optimal technological processes of hobbing and management of these processes. Introduction The gears are integral parts of modern machines, which in the near future do not have an alternative in most applications. These are parts of increased complexity and considerable laborability, which are produced in significant annual volumes in all branches of mechanical engineering.

Los trenes de engranajes son utilizados masivamente en sistemas de transmision de potencia
mecanica. Aun cuando las carcasas y los ejes utilizados son generalmente muy rıgidos, cuando se
aplican torques y fuerzas externas sobre el tren de engranajes todos sus componentes sufren pequeñas
deformaciones. Para mejorar los resultados de los analisis numericos, deben considerarse estas deformaciones
y sus efectos en el contacto entre engranajes. Este trabajo presenta un elemento de engranaje
modificado para modelar el efecto de desalineaciones y desplazamientos de ejes sobre la cinematica
del mecanismo y los esfuerzos transmitidos. Teniendo en cuenta el efecto de asentamiento que se logra
luego de las etapas iniciales de marcha, se comparan modelos teoricos y empıricos para describir los
perfiles de presiones de contacto que resultan de la desalineacion entre ruedas dentadas. El efecto de
las modificaciones introducidas se describe en algunos casos de ejemplo. Finalmente se detallan algunas
conclusiones y oportunidades de mejora para la formulacion implementada

The progress of additive manufacturing technology brings about many new questions and challenges. Additive manufacturing technology allows for designing machine elements with smaller mass, but at the same time with the same stiffness and stress loading capacity. By using additive manufacturing it is possible to produce gears in the form of shell shape with infill inside. This study is carried out as an attempt to answer the question which type of infill, and with how much density, is optimal for a spur gear tooth to ensure the best stiffness and stress loading capacity. An analysis is performed using numerical finite element method. Two new infill structures are proposed: triangular infill with five different densities and topology infill designed according to the already known results for 2D cantilever topology optimization, known as Michell structures. The von Mises stress, displacements and bending stiffness are analyzed for full body gear tooth and for shell body gear tooth with above mentioned types of infill structure.