Ján Kostka

Determination of the Fatigue Life of the Vehicle Construction Based on Strength Calculations

The article is divided into three parts. Except the foundations of theoretical knowledges about the fatigue life, the design of the breakdown truck body construction for a particular vehicle is also described in initials. In the second part the stress analysis of this construction is analyzed by finite element method (FEM). Based on this, at the end of the thesis, the fatigue life time is evaluated and compared with the experimental.

Proposal of Methodology for Determination of Stresses around Groove by Photo Stress Method

The aim of the paper is to propose a new methodology for verifying residual and operational stresses, determined by the drilling method. The newly proposed methodology will be based on the use of optical methods for total surface deformations and stress analysis through optically sensitive material applied to the surface of the object being investigated.

Stress Analysis Performed by Photoelasticity and Digital Image Correlation

This paper deals with the use of classical experimental technique of photoelasticity as well as modern one – digital image correlation by stress analysis. Both mentioned methods were used to compare the corresponding stress fields obtained on a sample with stress concentrators loaded by bending. The paper contains the basic principle of photoelasticity, methodology of static analysis with polariscope and briefly describes the measurement with low-speed digital image correlation system. Taking into account that the used correlation system does not allow to evaluated stress fields, calculation and visualization of stress fields were realized in program Q-STRESS v.1.0 developed at the authors department.

Utilisation Possibilities of PhotoStress Method in Determination of Residual Stresses

The presented paper demonstrates the determination of residual stresses by means of PhotoStress® method. The identification was performed on a drilled and subsequently loaded sample of a split ring. Through drilling and subsequent loading of the sample we were able to simulate residual stresses throughout the surface of the split ring. Using the values of residual stresses, a gradient of residual stresses was specified. The 3 mm thick split ring was laser-cut from a non-alloyed fine-grained structural steel sheet suitable for welding, i.e. steel 11 523. It was coated with 3.125 mm thick photoelastic coating PS-1A with fringe constant.

Proposal of Methodology for Verification of Stress Distribution in Bolted Joints by Optical Method

Nowadays, the most spread method for the solution of contact problems is based on numerical modelling. The bolted joints belong to the complex contact problems. In the paper is given methodology for the stress analysis of bolted joints with modification in the area of the first threads on the nut by the optical method. The stress analysis has been accomplished for the bolted joint without as well as with modification. The results of experimental measurements were verified by numerical modelling by the finite element method.