Volume 70 (2020): Edizione 1 (April 2020)

The helical gears are widely used in different engineering applications especially in case of vehicles on the gear boxes. The aim of this research is the analysis of the effect of number of teeth on the pinion beside of the constancy number of teeth on the driven gear. Five types of helical gears have to be designed for the comparative analysis. Own-designed designing software are necessary for the facilitation of the designing and modelling process. During this research the normal stresses and normal deformations will be analysed into different directions by TCA method. After the analysis the functions of the mechanical properties and the number of teeth will be determined.

In order to study the strength of the proposed rope threaded joint for machine parts made of reinforced composite materials, a modeling of a stress-strain state was conducted using the software of finite-element analysis LS-DYNA. Stress-strain state modeling was conducted for a rope threaded joint, affecting on the main performance parameters considered to be p – thread pitch (p = 4 mm), and t – thread depth (t = 1 mm). The main thread parameters taken for the model were up to the metric thread М6 (ISO 724:1993) parameters.

This paper confers to compare the behavior of AZ91E, AZ91E with 2 wt. % plain and surface modified alumina reinforced composites under different loading conditions. The composites were prepared and specimens were cut in accordance with standard procedures to conduct impact and fatigue tests. Surface modified alumina reinforced AZ91E magnesium based composites resulted in improved impact and fatigue strength because of good interactions between the matrix and reinforcement. The results are discussed.

The paper deals with Finite difference Method of solving a boundary value problem involving a coupled pair of system of Ordinary Differential Equations. A novel iterative scheme is given for solving the Finite Difference Equations. Quasi-linearization used to convert a nonlinear problem into a series of linear problems. A problem from a flow of a nanofluid is presented as an example.

The heat exchangers are used to heat or cool the material streams. To calculate the heat exchanger, it is important to know the type of heat exchanger and its operating characteristic. This characteristic determines one of the key variables (e.g., F, NTU_min, or θ). In some special cases, it is not necessary to know its operating characteristic to calculate the heat exchanger. This article deals with these special cases. The article also contains a general dependency that allows checking the key variables related to a given heat exchanger.

A method for calculating the ultimate true stresses arising in the walls of shells of revolution in the area of uniform plastic deformation is developed in the research. In order to derive the stability loss for the plastic deformation process the criterion of maximum load is taken as the basis, simple differential equations were solved. It has been shown analytically that the level of the boundary true stresses is much lower when the values of the principal stress ratios approach to 2 or 1/2 compared to the adjacent stress states.

Nickel Titanium (NiTi) alloys are the class of smart materials classified under shape memory alloys. The traditional machining of these alloys is hard because of various inherent mechanical characteristics of these alloys. Therefore, non-traditional machining process such as wire electro discharge machining (WEDM) has been employed for machining of such alloys. The present study is focused on multi-performance characteristic simultaneous optimization of WEDM process parameters, in which three system control factors, namely, pulse on time (T_ON), pulse off time (T_OFF) and wire feed (WF) are considered for simultaneously maximizing material removal rate (MRR), while minimizing surface roughness (SR) and tool wear rate (TWR). The simultaneous optimization is performed using Taguchi’s Quality Loss Function. Analysis of means and analysis of variance have been carried out to identify the significance level of each system control factor. The different levels of settings and the optimized setting have been analysed using scanning electron microscope images for surface morphological studies. The multi-response optimization investigations revealed that T_ON is the major contributing factor and optimal performance values were obtained at T_ON of 125μs, T_OFF of 25μs and at WF of 4 m/min.

The impact of machine feed rates of Wire Electric Discharge Machining on the kerf-width (K-width), material-removal-rate (MR-R), and surface-roughness (S-R) in the machining of Al/SiC composite is practically analysed. The relation among the feed rates of machine and K-width, MR-R, S-R is graphically acquired. It is demonstrated that lesser rate of feed is responsible for generation of larger K-width, lesser MR-R, and good finish as compared to more feed rate.

Most of the people living in developing or less developed countries have limited earning to provide somehow their basic needs & usual staff. Carrying goods is a regular task in life & several products have been invented to minimize efforts in this purpose. But the product’s price & features are not optimum for the people of fewer earnings. Stair climbing cart is very useful for those houses where a lift is not available and goods have to be carried frequently upstairs. In this research, the mechanical design has been modified so that the manufacturing cost can be minimized. Finite element analysis has been performed upon the design to find out how the manufacturing cost can be reduced by making the design optimal for manufacturing cost and process. The result shows that the structural members should not be processed further because any tooling operation will require an extra machine as well as an extra cost. Only the wheels are possible to subject under optimization by reducing material as well as weight. This article will be a valuable asset for the mass manufacturers of this type of product.

The paper deals with stress and reliability calculation of a gas pipeline straight section buried in a ground (elastic foundation) loaded by heating and internal overpressure. Mathematical derivation of relations necessary for reliability calculation of the pipeline section by stochastic approach is also included in the paper. Resulting values are obtained by software Anthill using the Monte Carlo method. Input random parameters of the examined pipeline section are shown by bounded histograms.

Corrosion and corrosion-fatigue tests of the material of the pipeline, which was in operation for 41 years. It has been shown that prolonged operation reduces the parameters of resistance to fatigue and prolonged static loading in corrosive environments. It was established that the degradation of physical and mechanical properties is insignificant, Ukraine’s main gas pipelines are ready to operate at full capacity provided that timely monitoring measures are carried out.

The objective of these analyzes is to evaluate the behaviour of bearing cage in operation and to determinate the safety factor towards to yield and ultimate strength of structure, when cage is under load. Safety factor can be defined as force needed to achieve yield or ultimate strength divided by operation force given from dynamic simulation. Second analyze was based on pressing of whole cage in radial direction to determinate radial pressing force needed to achieve yield and ultimate strength.

The technique of obtaining a hyperboloidal gear engagement with linear contact between a cylindrical involute wheel and a hyperboloid producing worm is considered. The resulting cutting tool greatly simplifies the manufacturing technology of hyperboloid worms and hyperboloid gears along with improved accuracy and roughness of the machined teeth and lower manufacturing costs.

The purpose of this technical note is to present a method of analysis of a joint made using a single row of bolts, typical of a bolts around the edge of a closure plat or a simple bracket. Classical analysis methods are applied to the joint subjected to combinations of both in-plane and out-of-plane loads and moments. An analysis of loads and stresses in a single bolt is developed. The note brings together a number of concepts and links them into a practical design analysis process that is applicable for many cases of joints made with a single bolt or a single line of bolts and are adequate to demonstrate the structural integrity of the joint. In some cases finite element methods may be more appropriate, and the methods discussed can be used in the validation process.