Contents of Journal of Mechanical Engineering 61, 4 (2010)



KLIMAN, V., GIBA, V., JELEMENSKÁ, J., ŠIŠKO, R.: Probabilistic 
approach to fatigue reliability assessment. Part I. Fatigue-life
estimation model 191

KLIMAN, V., GIBA, V., JELEMENSKÁ, J., ŠIŠKO, R.: Probabilistic
approach to fatigue reliability assessment. Part II. Example
of application 203

RAJESWARI, K., LAKSHMI, P.: A PSO-tuning of Fuzzy Logic Controller
for vehicle suspension system 215

LIN ZHU, TIEN-CHIEN JEN, YI-HSIN YEN, CHENG-LONG YIN, MEI ZHU:
Numerical investigation of heat pipe cooling in drilling applications 233







Probabilistic approach to fatigue reliability assessment Part I. Fatigue-life estimation model

V. KLIMAN, V. GIBA, J. JELEMENSKÁ, R. ŠIŠKO

In this paper we propose a simple computing procedure to determine in probabilistic form the material constants that enter fatigue-life calculation, namely fatigue strength (ductility) coefficient s'f (e'f) and fatigue strength (ductility) exponent b (c). The procedure, which assumes log-normal distribution of fatigue-life, is based on the shift of the regression line (representing the fatigue-life curve) to the desired value of the probability of occurrence. The calculation yields a set of material constants s'f , b, e'f, c ranging in probability of occurrence from 1% to 99%. Suitable application of this procedure to the life estimation model under random loading conditions yields the fatigue-life distribution function in respect of the scatter of cyclic material properties. The life estimation model thus modified enables the assessment of fatigue reliability at critical spots of a construction taking into consideration the scatter of cyclic properties of the material.


Probabilistic approach to fatigue reliability assessment Part II. Example of application

V. KLIMAN, V. GIBA, J. JELEMENSKÁ, R. ŠIŠKO

In Part I of this paper, a simple computing method for determining the Manson-Coffin fatigue-life curve parameters in probabilistic form was proposed. Part II presents the application of this method to evaluate fatigue reliability of a vehicle's construction. The magnitude of scatter of a material's cyclic properties at a critical spot in its construction (welded joint) is shown to greatly affect fatigue reliability, e.g. for a requirement of 5 years' failure-free operation, the probability of premature fatigue failure varies from 2.5% to 30% depending upon this magnitude. Based on the proposed methodology, the maximum permissible value of the scatter of a welded joint's cyclic properties was determined to ensure that the probability of premature fatigue failure occurrence would not exceed the allowable value.



A PSO-tuning of Fuzzy Logic Controller for vehicle suspension system

K. RAJESWARI, P. LAKSHMI

In this paper, Particle Swarm Optimization (PSO) is developed for tuning Fuzzy Logic Controller (FLC) applied to active suspension system. First the controller is designed according to Fuzzy Logic rules for disturbance rejection to reduce unwanted vehicle's motion. Then the FLC is optimized with PSO and Genetic Algorithm (GA) so as to obtain optimal adjustment of the scaling factors, membership functions and the number of fuzzy control rules. Root-Mean Square (RMS) value of the body acceleration is considered as the performance index. The relative performances of the two algorithms are compared. Digital simulation results demonstrate that the PSO tuned FLC based active suspension system exhibits an improved ride comfort and better road holding ability than its counterparts.



Numerical investigation of heat pipe cooling in drilling applications

LIN ZHU, TIEN-CHIEN JEN, YI-HSIN YEN, CHENG-LONG YIN, MEI ZHU

In this paper, the feasibility and effectiveness of heat pipe cooling in drilling operations are investigated. A new embedded heat pipe technology was used to remove the heat generated at the tool-chip interface in the drilling process. Numerical studies were involved in four cases, including solid drill without coolant, solid drill with coolant, heat pipe drill, and heat pipe drill with coolant. The thermal, static and dynamic characteristics of the drill were investigated using a numerical calculation with Fast Finite Element (FFE) Method plus solvers based on explicit finite element analysis software. The results indicate that the heat pipe drill is most feasible and effective in the actual drilling processes.