Contents of Journal of Mechanical Engineering 60, 3 (2009)


ALDAJAH, S.: Thermal residual stress development in a laser glazed carbon steel 121

ÉCSI, L., ÉLESZTÖS, P.: One of the possible variational formulations 
of fully coupled thermal-structural analysis                                    135

KOTAIAH, K. R., SRINIVAS, J., BABU, K. J.: Prediction of optimal stability 
states in inward-turning operation using genetic algorithms                     145

FIALOVÁ, S., POCHYLÝ, F., FEDOR, P.: Gels as construction materials             161

KOTAIAH, K. R., SRINIVAS, J., BABU, K. J.: Force feed effects on stability 
in turning                                                                      169

Abstracts

Thermal residual stress development in a laser glazed carbon steel

SAUD ALDAJAH

Laser glazing is a relatively new surface modification technique in which a high-power laser beam is used to melt the top layer of the surface, followed by rapid cooling and resolidification. This results in a new surface layer microstructure with enhanced hardness properties. Due to the melting and rapid solidification of laser glazing process, thermal stresses are developed within the substrate. These stresses are high enough to cause microcracks to develop in the glazed region. This paper introduces an analytical model to determine thermal stresses developed in a laser glazed 1080 steel rectangular sample.

One of the possible variational formulations of fully coupled thermal-structural analysis

LADISLAV ÉCSI, PAVEL ÉLESZTÖS

In this paper, a possible variational formulation of fully coupled thermal structural analysis is presented. The aim of the formulation is to solve a specific thermal-structural problem with heat convection using the finite element method. In this particular case the applied heat equation may be extended with the conservation of mechanical energy, which results in the complete first principle of thermodynamics to be included in the variational formulation of the problem. Such a constrained formulation automatically ensures the two-way coupling in weak solution of the governing equations, which, if additionally supplemented with thermal dissipation, will result in a more complete formulation of solid body deformation thermodynamics outside the equilibrium. The constraint equation is of great importance as it ensures the two-way coupling normally realised via the Neumann type boundary condition of the Euler-Cauchy equation of motion. In this paper some results in the early stage of the mathematical model development are presented using a cross-shaped specimen in biaxial tension.

Prediction of optimal stability states in inward-turning operation using genetic algorithms

KALLURI RAMA KOTAIAH, JONNALAGADDA SRINIVAS, K. J. BABU

This paper proposes a neural network-based optimisation scheme for predicting localized stable cutting states in inward turning operation. A set of cutting experiments is performed in inward orthogonal turning operation. The cutting forces and critical chatter locations are predicted as a function of operating variables including tool-overhanging length. A neural network model is employed to develop the generalized relations. The optimum cutting parameters are predicted from the model with the help of binary-coded Genetic Algorithms. Results are illustrated with the data of four different work materials.

Gels as construction materials

SIMONA FIALOVÁ, FRANTIŠEK POCHYLÝ, PAVOL FEDOR

The convolute equation of the gel structure as a rheology material is presented in the paper.
The convolute equation is expressed in the memory dependence as a linear model in the first case. This model is compound of reversible and irreversible parts that characterize the stress tensor. The dependence is formulated by the convolution integral.
Next model considers the nonlinearity between certain characteristic stress and the strain rate.
Another part of the paper is the methodology concept of the gel memory determination and the volumetric compressibility modulus definition.
The gels usage is assumed as well in the biomedical engineering as in the engineering industry, for example for the noise and shocks elimination and the special sleeve bearings design.

Force feed effects on stability in turning

KALLURI RAMA KOTAIAH, JONNALAGADDA SRINIVAS, K. J. BABU

This paper presents an analytical stability analysis of turning using a non-linear force-feed model in two dimensions. Most of the existing analytical models ignored the effect of static feed term on the regeneration phenomenon. In practice there is a marked effect of feed on stability due to force variation. The modified analytical equations for cutting insert using three-dimensional tool geometry are obtained by considering relative motion of tool with respect to a two-dimensional elastic model of the work-piece. The critical stability limits obtained as a function of feed are confirmed by time domain analysis. Experiments are conducted on a flexible work-piece at varying feed conditions. The measured cutting forces show a marked effect of feed on stability. Neural network models were developed to obtain the critical depth of cut at various values of operating speed and feed.