Workswell (Czechia)

Resistance spot welding (RSW) is one of the main joining technologies of thin sheets in the automotive industry. Key factors affecting the strength of the RSW joint are the nugget diameter, asymmetry, expulsions, intended surfaces, and the presence of cracks. Despite its broad use, the RSW joint quality verification is limited only to destructive testing and a limited number of non-destructive testing (NDT) methods. Most of the testing is done destructively by sampling, which assesses only systematic defects. Ultrasonic Testing (UT) is the most used NDT method to detect non-systematic defects in the RSW joints, however the probability of the defect detection of conventional testing techniques is not fully satisfactory. Other approaches were invented to deal with this situation. The article uses the currently most used NDT approach of the UT testing as a benchmark to evaluate the ability of thermographic testing to detect defective welds of the resistance spot welding in an on-line mode. The article demonstrates that the infrared thermography may find systematic process errors that are not detectable by other NDT methods by an analysis of different temperature drops measured after a constant delay time caused by different cooling dynamics of satisfactory and non-satisfactory weld joints.

This paper describes an alternative method of correction of the influence of wind speed within thermographic measurements of power system components. Instead of measurements of wind speed measured temperature of a resistor fed by known electrical power is used. The paper gives theoretical background of the method and measurement's results.

The first objective of this study is to develop a Data Envelopment Analysis (DEA) model to determine the relative technical efficiency of firms to create shareholders’ value. The second objective is to compare the technical efficiency with the profit ratios in the Du Pont analysis to determine whether there are some consistencies between these two measures of performance. Data of 33 JSE Limited listed manufacturing companies were used over a five-year period. The study found that there is a significant monotone dependence between the annual technical efficiency and the return on equity of companies. The practical implication of the study is that it provides a functional model that indicates an aggregated judgement of a firm’s efficiency of using resources to create shareholders’ value, and, the readily available return on equity can be used as a substitute to technical efficiency, which is more complicated to calculate. The value of this study is that it is the first to apply a unique DEA model for profit-motive companies.