# Upgrade of the Universal Testing Machine for the Possibilities of Fatigue Tests in a Limited Mode
## 3 Examples of Ways and Reasons for Upgrading in Technical Practice  
From the wide range of information available on the methods and reasons for upgrading test machines or entire measurement chains and test methods in technical engineering practice, several examples can be given from different fields of application. [PERSON] et al. in [4] presents a description and a certain solution to the practice situation, when before deployment of components in industrial applications it is advisable to perform mechanical fatigue tests of the materials used and of the whole prototype structures. However, such fatigue tests often require continuous long-term application of a suitable handling and clamping fixture. However, this can present a problem in terms of outsourcing the testing and can also be limiting in terms of the ability to adapt quickly and easily to a particular type of test. This paper presents the design and feasibility of a simple low-cost, adaptable jig designed for bending fatigue testing of structural elements. The jig was designed and evaluated using FEM and later on real long-term experiments to verify the longevity of the jig. Compared to outsourcing, this design is cost-effective, according to the authors, if longer-term tests are planned at the level of more than 373 h of testing. An assembly using the test machine and the proposed jig will allow for continuous long-term fatigue testing while allowing for multiple customization options. The options, among others, consist in the ability to choose the method of fatigue loading of the beam in the mode of three-point or four-point bending, with the choice of the level of minimum (as compressive) and maximum (as tensile) loading force and loading speed. A remarkable example according to [5] was even not only the development but also the actual production of a simple experimental device based on commercially available components such as an electric drive motor or digital speed sensor. A custom clamping frame with integrated spring load system was also developed and manufactured. The testing machine was developed for the purpose of rotational bending tests based on the [PERSON]. [PERSON] principle for educational or less demanding commercial applications. It was designed and implemented at a fraction of the cost required to purchase or procure a commercially manufactured product. [PERSON] in [6] presents a description of the redesign and automation of a machine for fatigue testing in rotational bending by applying knowledge and principles from mechatronics. The publication presents examples of the final design and how to apply the LabView graphical programming tool in the development of the control interface and in the simulation of the tests. The contribution [7] brings a study of low-cycle fatigue analysis using miniature specimens under high temperature conditions and considering the effects of surface roughness and residual stress. These miniature specimens with a non-standard test cross-section diameter of 1 mm were taken from the failed portions of standard size specimens. Based on the verification tests, the results were found to be in relative agreement with those obtained on the large 6.5 mm diameter specimens. By shrinking the test specimens, these efforts bring about a streamlining of testing and methodology, material savings and thus modernization of test equipment and entire measurement chains by miniaturizing them. A presentation of similar efforts and activities can be found, e.g., in the works [8; 9]. [PERSON] et al. in [10] discusses the problem of design and implementation of a relatively simple test device for fatigue testing of fiber-reinforced polymer (FRP) composites. The proposed device allowed to take into account several important parameters such as fiber/matrix ratio, fiber orientation, and order of fiber deposition. At the same time, it allowed the tests to be carried out at low frequencies in order to avoid temperature rise in the polymer matrix, which could degrade the mechanical properties of the composite.