Contents of Journal of Mechanical Engineering 55, 4 (2004)

 
SIVARAO, S. P. - CHIN, Ch. W.: Comparison of statistical and mathe-
matical methods for determination of tool wear in drilling                187

KVASNICKA, P., PALCAK, F.: Optimization of the engine mounts on a car 
model using ride comfort criteria in a multiobjective function            199                                                                  136
             
KLIMAN, V., - JAROSI, M.: System of continuous assessment of structure
fatigue reliability. Part I: Methodology (in Slovak)                      218

ZOLNAJ, Z. - JELEMENSKY, K.: Influence of rectangular duct cross-section
shape factor on the velocity fields at helical flow (in Slovak)           235

Abstracts

Comparison of statistical and mathematical methods for determination of tool wear in drilling

SUBRAMONIAN P. SIVARAO, CHEE WEN CHIN

Metal removing process is becoming increasingly more complex, demanding, and it experiences an unprecedented growth. It has been reported that one-third of material removal process performed in industry is drilling operation. This complex cutting operation holds a substantial portion of all metal cutting operations, and the largest amount of money spent on any one class of cutting tool is drill. From the viewpoint of cost and productivity, modelling and optimization of drilling process is extremely important for the manufacturing industry. For a successful progress, it is necessary to develop, support and maintain a vigorous innovative manufacturing industry, based on advanced technologies which can operate successfully in the competitive world.

The aim of the present work is to identify suitable parameters, monitoring of which enables predictions of drill failures. The paper deals with a comparative performance analysis and modelling of the twist drills at different cutting conditions for a model designed according to factorial design method. Experiments were performed using two straight shank twist drills of different make (tool X and tool Y) possessing the same specifications. The variables selected for tool wear are cutting speed, feed, thrust force, and machining time. The relative comparison of tool wear for tool X and tool Y is done by actual measurement, statistical analysis and inverse coefficient matrix method.

Optimization of the engine mounts on a car model using ride comfort criteria in a multiobjective function

PAVEL KVASNICKA, FRANTISEK PALCAK

After theoretical background of the ride comfort evaluation, a study of the influence of the ride comfort criteria to a multiobjective optimization of engine mounts is presented in this paper. The objective function Obj_CMA is constructed as a weighted combination of the ride comfort perception quantity, standard deviation of movements of the engine mounts and acoustic motivated criteria. For the ride comfort perception optimization and the car model identification a MATLAB toolbox was developed.

System of continuous assessment of structure fatigue reliability. Part I: Methodology

VLADIMIR KLIMAN, MARIAN JAROSI

The paper is devoted to the problem of a continuous assessment of fatigue reliability of structures under operation with a random nature of loading. A model has been developed which enables real-time computation of the following characteristics needed for assessment of the structure service in view of fatigue:

- the fatigue damage value is probabilistic interpretation; - the probability of premature fatigue failure occurence regarding the requirement on service life of the structure and probability survival of this requirement; - the probability survival in regard to the current time of structure service; - remaining fatigue life; - the parameters enabling to assess the change of fatigue life of the structure in consequence of a non-standard load situation occurence.

The methodology proposed serves as the basis for elaboration of a computer program providing continuous monitoring of the mechanical structure operation with the aim:
- early indication of a forthcoming dangerous state of the structure in view of fatigue damage in order to prevent the breakdown of the equipment, and
- to optimize the cost needed to provide a reliable structure operation.

Influence of rectangular duct cross-section shape factor on the velocity fields at helical flow

ZELIMIR ZOLNAJ, KAROL JELEMENSKY

A renormalization-group-based k-eps model of turbulence for fully developed turbulent flow of an incompressible viscous fluid in helical ducts of rectangular cross-section is used for numerical modelling of velocity distribution. The results of measured velocity distributions in helical ducts by Laser-Doppler Anemometry are presented. Both numerical and experimental data are compared. The influence of the shape factor of cross section h/b on the velocity fields in a stabilized flow is reviewed.