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The laser micro-machining was carried out on a station equipped with a TruMicro 5325c laser emitting ultraviolet radiation (343 nm wavelength) in picosecond pulses. On the surface of the Ti6Al7Nb alloy, dimple texturing with a constant diameter of ~200 µm, different depths (from ~5 to ~78 µm) and density (from 10% to 50%) were produced. The value of surface free energy was determined with the Owens-Wendt method using two measuring liquids: distilled water and diodomethane. The Staphylococcus epidermidis strain was used to test the adhesion of bacteria. It was found that the surface free energy value is influenced by both of the texture parameters (density, depth). The density also affects the potential for biofilm formation. Based on the analysis, it was shown that with an increase in surface free energy, the number of adhering microorganisms increases exponentially. Moreover, the study shows that there is a correlation between the number of adhering microorganisms and surface free energy.
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One of the most commonly applied methods of joining dissimilar materials is gluing. This could be mainly attributed to the applicability of this technique in various industries. The article presents a method of material surface treatment, which increases the shear strength of adhesive joints for lightweight metals such as aluminum with plastics. For this purpose, laser surface microstructuring was performed on each of the selected construction materials. As a result of the performed treatment, the active surface of the glued area was increased, which increased the adhesive strength. The picosecond laser with UV radiation used in the research is TruMicro 5325c with which material can be removed as a result of the cold ablation phenomenon. The applied parameters of the laser device did not cause thermal damage to the surface of the microstructured materials, which was confirmed by microscopic examination. Laser micromachining did not deteriorate the degree of wetting of the tested materials, either, as was confirmed by the contact angle and surface energy measurements with the use of water as the measuring liquid. In investigated cases of microstructure types, the presented method significantly increased the shear strength of the joints formed, as demonstrated by the presented strength test results. Research has shown that created joints with microstructure made according to the described method, are characterized by a significant increase in strength, up to 376%, compared to materials without microstructure. The presented results are part of a series of tests aimed at selecting the operating laser parameters for the implementation of geometric shapes of microstructures which will increase the strength of adhesive joints in selected materials.
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This article presents the results of research on the technology and peripheral properties of laser-welded micro-couplings. The aim of this research was to determine the characteristics of properly made joints and to indicate the range of optimal parameters of the welding process. Thin-walled AISI 316L steel pipes with diameters of 1.5 and 2 mm used in medical equipment were tested. The micro-welding process was carried out on a SISMA LM-D210 Nd:YAG laser. The research methods used were macroscopic and microscopic analyses of the samples, and assessment of the distribution of elements in the weld, the distribution of microhardness and the tear strength of the joint. As a result of the tests, the following welding parameters are recommended: a pulse energy of 2.05 J, pulse duration of 4 ms and frequency of 2 Hz, beam focusing to a diameter of 0.4 mm and a rotation speed of 0.157 rad/s. In addition, the tests show good joint properties with a strength of more than 75% of the thinner pipe, uniform distribution of alloying elements and a complex dendritic structure characteristic of pulse welding.
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Elastomers are used as construction materials in numerous industries, and in particular the biomedical industry, mechatronics, electronics, the automotive industry, and chemical devices. The paper presents the results of tests involving the effects of microprocessing of elastomeric materials using a UV laser emitting picosecond pulses. In particular, it presents an analysis of the influence of the parameters of processing on its efficiency. The paper provides a recommendation of the most advantageous processing parameters for materials such as polyurethane and silicone (MVQ). The authors see prospects for the use of the developed technology in the techniques of sealing and microfluidisation. The final part of the paper presents examples of surface structures generated on elements made of artificial materials and the results of tests involving reduction of friction resistance of sealing rings in a pneumatic actuator.
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In this paper, an experimental investigation of the ablation plasma generated from the copper substrate by means of nanosecond laser pulses is presented. We studied the evolution of the ablation plasma in the first 1000 ns after plasma onset using the fast-gated imaging and optical emission spectroscopy methods. Plasma imaging showed that the expansion of the plume front can be described using a so-called drag model, with the expansion limit increasing with laser fluence from 254 µm for 30J/cm2 to 375 µm for 67J/cm2. By using the Boltzmann plot and Stark broadening methods, it was found that within the first microsecond after onset, the electron excitation temperature and electron number density decrease from 1.2 eV to 0.8 eV and from 4×1016cm-3 to 5×1015cm-3, respectively. Using the McWhirter criterion, we confirmed that in the considered time range the plasma remains in a state of local thermodynamic equilibrium.
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This paper presents the results of laser welding of dissimilar joints, where low-carbon and stainless steels were welded inthe lap joint configuration. Performed welding of austenitic and ferritic-pearlitic steels included a sealed joint, where only partial penetration of lower material was obtained.The authors presented acomparative study of the joints under different configurations. The welding parameters for the assumed penetration were estimated via anumericalsimulation. Moreover, a stress-strain analysis was performed based on theestablished model. Numerical analysis showed significant differences in joint properties, therefore, further study was conducted. Investigation of the fusion mechanism in the obtained joints wascarried out using electron dispersive spectroscopy (EDS) and metallurgical analysis. The study of the lap joint under different configurations showed considerable dissimilarities in stress-strain distribution and relevant differences in the fusion zone structure. The results showed advantages of using stainless steel as the upper material of a microstructure, and uniform chemical element distribution and stress analysis is considered.