Temperature is one of the essential parameters in fusion welding. Typically, an uncooled infrared detector acquires 14-bit data, while a human observer can only distinguish about 128 levels of grey. ...For IR HDR (high dynamic range) images, one of the main goals of dynamic range compression is to enhance the visibility of low-contrast details. It is an important issue because the temperature span in the cross-section of a welded joint and its length are large. In the paper, global approaches for range compression are investigated, such as algorithms that include pixel transformations, histogram equalization ('he') and some of its variants. Additionally, multiscale decomposition methods were investigated. All results are obtained for the sequences of thermograms acquired during the TIG welding of plates made of Inconel 625 superalloy. The process was observed with an uncooled IR camera. The application of compression methods led to the generation of low-dynamic-range (LDR) IR images. The algorithms allowed the preservation of global contrast and enhancement of the visibility of hot details in dark and low-contrast areas. All IR representations of the welded samples were evaluated, and relationships between apparent temperature counted in the pixel-level value and weld-face geometry were revealed. Methods based on wavelet transforms were found to be the most suitable for this type of image; nevertheless, a relatively large local noise was generated.
The aim of this study was to analyze the effect of the HFMI (high-frequency mechanical impact) treatment of each weld bead on the properties of a butt joint with a ceramic backing welded by robotic ...method 135 (MAG—metal active gas welding method) and to determine the effect of HMFI on the stress level. This analysis was based on a comparison of three butt joints made of a S690QL plate, in the as-welded condition, with the HFMI of each bead and with the heat treatment carried out with PWHT stress relief annealing. The high-frequency (90 Hz) peening of each weld bead was linked with a stress reduction in the weld via the implementation of compressive stresses into the joint. The HFMI pneumatic hammer was used for this. The correctness of treatment was achieved when 100% of the surface of each bead including the face was treated. As part of the post-welding tests, basic tests were carried out based on the standards for the qualification of welding technology, and as a supplementary test, a stress state analysis using the Barkhausen effect was carried out. The tests carried out showed that the use of high-frequency peening after each pass did not affect the negative results of all the required tests when qualifying the welding technology of S690QL sheet metal compared to the test plates in the as-welded condition and after heat treatment—stress relief annealing. Inter-pass peening of the welded face and HAZ (heat-affected zone) resulted in a reduction in post-weld residual stresses at a distance of 12 mm from the joint axis compared to the stress measurement result for the sample in the as-welded condition. This allowed for a positive assessment of peening in the context of reducing the notch, which is the concentration of tensile stresses in the area of the fusion line and HAZ. The tests carried out showed that the peening process does not reduce the strength properties of welded joints, and the results obtained allow the technology to be qualified based on applicable standards.
The study is concerned with the assessment of the weldability of steel S700MC subjected to the thermomechanical control process (TMCP) and precipitation hardening and characterised by a high yield ...point. Appropriate mechanical and plastic properties of steel S700MC were obtained using the thermomechanical control process through precipitation, solution, and strain hardening as well as by using grain-refinement-related processes. Constituents responsible for the hardening of steel S700MC include Ti, Nb, N, and C. The hardening is primarily affected by (Ti,Nb)(C,N)-type dispersive precipitates sized from several nanometres to between ten and twenty nanometres. The welding process considerably differs from TMCP conditions, leading to the reduction of plastic properties both in the heat-affected zone (HAZ) and in the weld area. This study demonstrates that in cases of TMCP steels, where the effect of precipitation hardening is obtained through titanium and niobium hardening phases, the carbon equivalent and phase transformation γ-α cannot constitute the basis of weldability assessment. The properties of welded joints made from the above-named group of steels are primarily affected by the stability of hardening phases, changes in their dispersion, and ageing processes. The most inferior properties were identified in the high-temperature and coarse-grained HAZ area, where the nucleation of hardening phases in the matrix and their uncontrolled reprecipitation in the fine-dispersive form lead to a sharp decrease in toughness.
Welding is an important process in terms of manufacturing components for various types of machines and structures. One of the vital and still unsolved issues is determining the quality and properties ...welded joint in an online manner. In this paper, a technique for prediction of joint hardness based on the sequence of thermogram acquired during welding process is proposed. First, the correspondence between temperature, welding linear energy and hardness was revealed and confirmed using correlation analysis. Using a linear regression model, relations between temperature and hardness were described. According to obtained results in the joint area, prediction error was as low as 1.25%, while for HAZ it exceeded 15%. Future work on optimizing model and input data for HAZ hardness prediction are planned.
The microstructure of the in situ TiC-reinforced composite surface layers developed during laser surface alloying of a ductile cast iron substrate with titanium was related to the solidification ...conditions in the molten pool. The solidification conditions were estimated using infrared thermography. It was found that the cooling rates of the melt up to about 700 °C/s enable the complete reaction between carbon and the entire amount of titanium introduced into the molten pool. In turn, the cooling rate of about 280 °C/s for the melt containing 8.0 wt% Ti allows the TiC particles to grow in the dendritic form with well-developed secondary arms and a total size of up to 30 µm. For a constant Ti content, the cooling rate of the melt had no effect on the TiC fraction. The increase in the cooling rate elevated the retained austenite fraction in the matrix material, lowering its hardness.
Undoubtedly, culture is a unique way in which every human being identifies himself with a group of people and, in parallel, differentiates from others. It is also obvious that culture is not stable ...in its form, mostly because it is considered as an average of many factors determined by time, place, etc. Hence, culture searches for uniqueness, and that makes it the overriding objective for a group of people. On the other hand, it provides an ancillary support through common values that makes us human. On top of that, culture expresses itself through unique form of communication and as such might become a irreplaceable tool in the whole process of sending and receiving information. In our study, we made an effort to analyze the above-presented ambiguous concept of culture and to compare it with two exemplary leaders of Tanzania, namely Nyerere and Magufuli. Such analyses meant to help us to understand how they understood, lived, and used culture in their struggle for the development of Tanzania.
The paper presents the evaluation of the brazing capabilities of the multi-beam Trifocal laser joint system made of galvanized steel DX51D with a thickness of 3 mm, covered with a protective coating ...of Magnelis type. The brazed joints obtained have been subjected to metallographic, strength and corrosion resistance tests in the Ascott CCIP450 salt cell. The tests have shown that there is a certain range of brazing process parameters that allow to make the correct overlap joints of high quality with small welding distortions and a narrow heat affected zone. The obtained joints are characterized by a slightly worse corrosion resistance than the basic material, and zinc evaporation by means of additional low-power laser beams improves the solder's flow.
The aim of this study was to evaluate the structural changes of the airways using the endobronchial ultrasound (EBUS) in ACO patients compared to severe asthma and COPD patients.
The study included ...17 patients with ACO, 17 patients with COPD and 33 patients with severe asthma. Detailed clinical data were obtained from all participants. Basic laboratory tests were performed, including measurement of eosinophil counts in blood and serum immunoglobulin E (IgE) concentrations. All patients underwent spirometry and bronchoscopy with EBUS (a 20‑MHz ultrasound probe) to measure the total thicknesses of the bronchial walls and their particular layers in segmental bronchi of the right lower lobe. EBUS allows to distinguish five layers of the bronchial wall. Layer 1 (L
) and layer 2 (L
) were analyzed separately, while the outer layers (layers 3-5 L
) that correspond to cartilage were assessed together.
In patients with ACO the thicknesses of the L
and L
layers, which are mainly responsible for remodeling, were significantly greater than in patients with COPD and significantly smaller than in patients with severe asthma (median L
= 0.17 mm vs 0.16 mm vs 0.18 mm,
<0.001; median L
= 0.18 mm vs 0.17 mm vs 0.20 mm,
<0.001, respectively). The thicknesses of the total bronchial walls (L
+L
+L
) and L
were significantly smaller in ACO and COPD patients compared to asthma patients (median L
+L
+L
= 1.2 mm vs 1.14 mm vs 1.31 mm,
<0.001; median L
= 0.85 mm vs, 0.81 mm vs 0.92 mm,
=0.001, respectively).
The process of structural changes in the airways assessed by EBUS is more advanced in individuals with ACO compared to patients with COPD, and less pronounced compared to patients with severe asthma. It seems that EBUS may provide useful information about differences in airway remodeling between ACO, COPD and severe asthma.
The paper presents robotic spot resistance welding technologies for DOCOL 1200M steel with a thickness of 1.8 mm. DOCOL 1200M steel with a martensitic structure is intended mainly for the production ...of car bumpers, side beams and other elements ensuring the safety of the user of motor vehicles. The test joints were made on a robotic station equipped with a KUKA KR180 robot and a welding from ARO. The obtained welded joints were subjected to macro and microscopic metallographic tests, hardness measurement and strength tests. It has been shown that for properly selected resistance spot welding, DOCOL 1200M steel joints with a satisfactory strength level can be obtained.
This study discusses the effect of laser beam welding parameters on the structure, mechanical properties and corrosion resistance of 1.2 mm thick galvanized sheets made of low-carbon steel DC04 ...provided with a ZE36/36 GardoprotectOC2BU organic coating. The test laser beam butt welded joints were made without the filler metal, using a variable welding rate, where linear welding energy was restricted within the range of 30 J/mm to 90 J/mm. The joints were subjected to non-destructive tests, destructive tests and corrosion resistance tests. The tests revealed the possibility of making joints meeting the criteria specified in the ISO 15614-11 standard. Regardless of the value of linear welding energy applied in the process, all the joints were characterised by high mechanical and plastic properties. It was noticed that an increase in linear welding energy from 30 J/mm to 90 J/mm was accompanied by the widening of the weld and that of the heat-affected zone (HAZ). In addition, an increase in linear welding energy was accompanied by a decrease in the maximum weld hardness to approximately 250 HV0.2. In the HAZ, hardness was restricted within the range of 190 HV0.2 to 230 HV0.2 and decreased along with increasing linear welding energy. In the static tensile test, regardless of the value of linear welding energy, the test specimen ruptured in the base material. In the bend test, regardless of the value of linear welding energy, a bend angle of 180° was obtained without partial tear or scratches; unit elongation was restricted within the range of 29% to 42%. The electrochemical tests and experiments performed in the salt spray chamber revealed the very high effectiveness of the corrosion protections against aggressive chloride ions.
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