The aim of the conducted research was to compare the functional properties and the cutting accuracy of items produced using Fiber lasers in comparison with CO2 lasers. The object of 6 mm thick sheet plates made of S235JR steel cut with the two different laser types were analyzed. The tests covered dimensional accuracy (in accordance with the PN EN 22768-fH standard) and the surface after cutting (in accordance with the PN-EN ISO 9013: 2017-04). The results of the analysis have demonstrated that for the same welding linear energy, more accurate cutting surface is obtained using Fiber laser cutting.

In this paper, the possibilities of detection and measurement of fatigue crack length in welded joints made of steel of duplex type, have been presented. In the investigations there has been used an original research system FatigueVIEW employing advanced optoelectronic techniques and numerical methods of image analysis. The proposed approach enables analysis of the fatigue crack growth during fatigue tests and after their finishing in off-line mode.

The butt welding of 1.4462 (2205) duplex stainless steel plates with thickness of 4 mm under various welding parameters was achieved by Nd:YAG laser type without the use of the filler material. Welding parameters such as welding power (kW) and the focus distance from the joint surface (mm) were changed. The Ar 5.0 protective gas flow and welding speed were the same for all the tests and were 20 L/min and 0.5 m/min, respectively. The weld shape, weld macrostructure, microstructure, strength and hardness, and the content of the ferrite in the weld zone, heat-affected zone, and base metal were emphatically investigated. The test results showed that increase in laser power increases the weld zone area. For the weld samples, a better ferrite/austenite ratio was obtained by focusing the laser beam on the sheet surface. Furthermore, the largest elongation from strength test has been observed for the weld samples made with laser power of 2.0 kW.

This paper presents issues of fatigue life calculations in operational load conditions. The assumed runs were so processed as to get a set of sinusoidal cycles by using the following methods: full cycles counting method and rainflow counting method. On the basis of such sets of cycles of the varying parameters S_{m i} and S_{a i} were prepared block load spectra of equivalent amplitudes S_az , obtained with the use of an original method of these authors, in which two-parameter fatigue characteristics were applied. The work resulted in comparison of fatigue life results for load spectra determined by using the assumed cycles counting methods and the assumed two-parameter fatigue characteristics: the model IM, model II, model III and model IV, respectively.

When determining the characteristics of the fatigue crack growth rate, it is necessary, inter alia, to measure the crack length growth which must be combined with the number of accumulated load cycles. The length of the crack is determined using different testing methods. Recently, there is an increased interest in optical systems based on digital image correlation methods. These methods have however some limitations as regards, inter alia, the sharpness of pictures taken during tests e.g. at cryogenic temperatures. This paper presents a comparative analysis of the crack length “a” as a function of a crack-opening-displacement “δ” obtained by experimental and numerical method. The tests were performed under ambient temperature for CT type specimens made of Ti6Al4V titanium alloy. Numerical research was carried out by finite element method using ABAQUS software. Satisfactory results were obtained which gave the reasons for establishing a hybrid methods for the crack length determination.

This paper presents the results of the fatigue tests carried out on laser welded joints of DUPLEX 2205 steel (X2CrNiMoN22-5-3 according to PN-EN 10027-1:2007). The butt-welded joints were made using an Nd-YAG disk laser with no filler for two different welding parameters. The parameters were selected based on previous tests (according to PN-EN ISO 15614-11: 2005) conducted for joints made with more than ten welding parameters.The tests carried out provided a basis for the determination of optimum parameters for laser welding of DUPLEX 2205 steel in terms of fatigue life. Additionally, the fatigue test results were related to the fatigue life of samples taken from the parent material.