Eva Ostertagová

Methodology of contact stress analysis of gearwheel by means of experimental photoelasticity.

The subject of this paper is the analysis of contact stresses that occur between the teeth of a gear. The analysis was carried out by means of reflection photoelasticity, which is an experimental method rarely used in this field. Contact stresses assessed in the experiment are compared with values assessed through an analytical calculation while using the Airy stress function or Hertzian relations.

Miniature Mobile Bristled In-Pipe Machine

The in-pipe machine locomotes in the pipe on the principle of differential friction between the bristles and the pipe wall during the movement of the bristle forwards and backwards. These bristles are very important construction parts of the in-pipe machine. In order to define the locomotion of movement it is important to know the force situation on the bristles caused by its high deformation in the pipe. The determination of force situation brought us to a non-linear differential equation of the second order and determination of conditions for its solution. By this equation it is possible to describe the outline of large deformations of the construction part and to determine the forces affecting this part.

Methodology and Application of the Kruskal-Wallis Test

This paper describes the methodology and application of the very popular nonparametric test which is a rank based test named as Kruskal-Wallis. This test is useful as a general nonparametric test for comparing more than two independent samples. It can be used to test whether such samples come from the same distribution. This test is powerful alternative to the one-way analysis of variance. Nonparametric ANOVA has no assumption of normality of random error but the independence of random error is required. If the Kruskal-Wallis statistic is significant, the nonparametric multiple comparison tests are useful methods for further analysis. The statistical analysis of the application data in this paper was performed with software MATLAB.

Application of the harmonic star method in photoelastic separation of principal stresses.

This paper deals with automation of an experiment process by means of photoelasticity on the condition that only information which was previously collected by identification of isochromatic fringes is used. The analysis of this issue pointed to Poissons and Laplaces equations. These equations were solved through the harmonic star method. The automation of an experiment was based on the development of a noncommercial program for processing of data which had been collected during photoelastic measurements. In addition, the program was used for verification of these measurements and comparison of measurement outcomes with results which were gained by the finite element method (FEM). Such a program enabled us to measure stresses in a certain point of the examined surface and, at the same time, separate these stresses, that is, determine the magnitude of individual stresses. A data transfer medium-a camera-was used to transfer the picture of isochromatic fringes directly into a computer. The chosen procedure of solving and evaluating the experiment provided us with reliable outcomes comparable to results gained by FEM.

Analytical and Numerical Solution of Large Actuator Deformation

This paper deals with the possibility of controlled deformation of the actuator of a flexible system. In the solution, large deformations of the actuator have been assumed. The model was made of a material capable of large deformations caused by internal pressure. The internal pressure was let into the cavities located in the actuator. The solution was realized analytically and numerically. The results show the relevance of the stated proposal.

Application of the Simple Linear Regression Model in the Experiment

The paper presents the results of experiments and measurements of the stress of a pipeline located on a pipe bridge. The experiment was carried out by means of resistance strain gages for two modes, which were the stress changes upon pressure changes in the pipes and at the driving in of sheet pilings in the immediate vicinity of the pipeline. On the basis of measurements, the impact of these changes on the operational safety of the pipeline in the renovation process of old above ground and the realization of new underground pipeline solutions. Polynomial regression models were applied for the prediction and a statistical analysis of residuals was applied for the quality assessment of selected models.

Shape Memory Alloy Actuator (SMA)

Our article deals with the possibility of using shape memory material (SMA − Shape Memory Alloy) to create an actuator of the mechanical element. The biggest advantage of the SMA actuators compared to those made of conventional materials is that they have the ability to generate relatively great force, are of low weight and small size.

Aberration Problem within the Process of Automation of the Photoelastic Measurement of the Stresses

The aim of the paper is the automation of experimental determination of isotropic and orthotropic background stresses by the tools of the photoelasticity and by the effects of the isolines’ field recorded through the recording medium.

Photoelast Method and Possible Applications of Mathematical Statistics in Prediction of Stress State of Structural Elements

The presented article is dedicated to stress state development while assessing the concentration of stresses in samples with continuously changing notches. These samples represent connecting elements of structural parts. The stress states of selected samples were determined experimentally by means of reflection photoelasticity. This method is suitable mainly for determination of stress state in the whole area in question, predominantly though for the analysis of stress concentration and its gradient in the notched area. Within the method of reflection photoelasticity, a layer was used to analyse the stress field. When loaded, this layer exhibits the ability of temporal birefringence. One of the statistical methods was selected in order to predict the stress state of other samples with bigger notches.

Application of Differential Equations to Calculations of Large Deformations of Structural Members

The article discusses the application of differential equations to solve large deformations of the designed slender structural elements. The structural element under design has a variable circular cross-section in longitudinal direction. It is made of a composite material based on carbon fiber and is capable of large deformations. In the solution it was necessary to consider the nonlinear deformation theory, which led to the solution of a nonlinear differential equation of second order. The creation of the differential equation describing the line of elastic deformation of a significantly curved structural element required the formulation of input equations and boundary conditions for its solution. The results obtained by means of a differential equation were compared with the numerical solution applying the finite element method. The solution presented and methodology can be used for practical application in the engineering design of fishing rods.