Analytical and nonlinear FEM simulation of contact damage

of hardened gears

Veli Kujanpää, Heikki Martikka

Lappeenranta University of Technology

POB 20, FIN-53851 Lappeenranta, Finland

veli.kujanpää@lut.fiљљљљљ љљљљљheikki.martikka@lut.fi

In this paper results of studying contact endurance of laser transformation hardened teeth of quenched and hardened steel gears are reported. Analytical simulation is used to find safety margins against surface damage depending on distribution of surface hardening. Models for designing tooth root treatment to maximize fatigue life and for controlling surface and delamination damages are considered. Simulations using LS-DYNA FEM (Finite Element Method) virtual models of the microstructural mechanisms give detailed and visual scenarios of the contact damage phenomena and large deformation process involved. The results show that simulations can be advantageously used to predict and optimize contact endurance by surface hardening on micro and macro levels.

Introduction

Background for this study is need to control the contact mechanics behaviour of industrial machinery.The method is to simulate the behaviour of contacting surfaces. One tool is the LS-DYNA [1] program for simulating deformation and fracturing processes ofљ three-dimensional inelastic structures. The present study is based on data of FZG gear tests. The aim of the present study is to explore possibilities of optimizing gear tooth contact damage resistance using LS-DYNA [1] simulations and analytical models based on Stachowiak et al [2], Johnson [3], Dale [4] and Matsui [5].Some the results of the present study were extracted from the reference [6].

Conclusions

The following conclusions can be drawn.

1.    Methods of theoretical and experimental contact mechanics are effective tools in optimal design of highly stressed machine elements of mechanical power transmission and material contact loadings.

2.    Laser surface transformation method is a powerful energy and information intensive method for increasing the hardness values in controlled surface areas in or out ofљ complex geometrical components by two or three fold. Gears with low contact pressures and high speeds can be advantageously laser treated giving a hard and defect free surface. The weaknesses are observed at the transition zone of large hardness gradients where load compressive stresses are superposed on residual stresses. The factors of safety are acceptable according to analytical and FEM simulations.

3.    Analytical simulation models can give physical design tools for controlling the main parameters. FEM models can give visual scenarios of damages. Better models and material data are needed to obtain quantitative results.

References

1.      LS-DYNA Version 950, university licence version, Theoretical manual, Livermore Software Technology Corporation, Livermore.

2. G.W.Stachowiak, A.W.Batchelor. Engineering Tribology, Butterworth Heinemann, Boston, 2000.

3.      K.L.Johnson. Contact mechanics, Cambridge University Press, 1987.

4.      C.Dale, McIntyre, Kerry, P., Lamppa, Macie M. Sturm, Neau, E L, and Stinnet R W, Microsecond heat treatment of gears.

5.      K.Matsui, H.Eto, K.Yukitake, Y. Miak, K.Ando. Increase in Fatigue Limit of Gears by compound Surface refining Using Vacuum Carburizing, Contour Induction Hardening and Double Shot Peening, JSME International Journal, Series A, Vol.45, No.2, 2002, 290-297.

6.      H.Martikka, H.Eskelinen. Study of wear damage resistance of gears using laser surface treatment and microstructural simulation. Sixth international conference on computational methods in contact mechanics, WIT Press, UK, 2003, 125-136.

7.      S.T.Mileiko. The tensile strength and ductility of continuous fibre composites, J. Mater.Sci., 4, 1969, 974-977.

8.      S.W.McGregor. Handbuch der analytischen Verschleissberechnung. New York, Plenum Press, 1964.