During laser shock peening, the pulsed laser with high energy is irradiated on the surface of the absorbing coating, after which the laser induces a plasma explosion. The plasma explosion could induce a shock wave with high peak pressure much higher than the yield strength of metal samples so that the plastic deformation can be formed after laser shock peening. After laser shock peening on metal materials, the shock wave could form compressive residual stress near the surface of the sample, which is beneficial for the mechanical properties. The hardness tester is used to measure the hardness of the sample with and without laser shock peening. The results of hardness could be used to analyze the effect of absorbing coating on shock wave. The study of laser shock peening with different absorbing coatings, such as black tape, aluminum tape, and paint coating, could help the application of laser shock peening for metal parts with complex shapes.
As the third generation of photovoltaic cell technology, the Perovskite Solar Cells (PSCs) have strong theoretical advantages compared with discrystalline silicon and thin film cells because of their material characteristics. In the formation of the series structure of perovskite cells, different film layers need to be marked at different positions. The scribing of functional layers can be done by mask plate, chemical etching, mechanical or laser scribing. Laser scribing can produce finer scribing areas. At present, laser scribing has gradually replaced other scribing methods and become the main scribing methods. In this paper, laser scribing for the realization of all the P1, P2, and P3 scribes are reported by optical fiber femtosecond laser with output wavelengths of 532 nm, and pulse width is adjustable at 300 fs. The better processing parameters are found for the scribing speed of 2000 mm/s, and the laser power of 1.8 W for the P1 scribe. High precision scribing with slit width less than 10 μm is obtained by optimizing scribing speed and laser power. All the results indicate that laser scribing would play an important role in achieving high performance PSCs modules in which the interconnects.
Laser shock peening is an effective surface technology for improving the surface mechanical properties of metals. Many studies have been performed to process different kinds of metallic material that can induce compressive residual stress in the top layer of samples, which would extend the fatigue life of metal parts in the industry. The titanium alloy samples are treated by laser shock peening with water layer as constraint layer and without protective coating in this research, after which the titanium alloy samples are observed and analyzed with a scanning electron microscope, hardness tester, laser confocal microscope, and wear tester. The surface roughness, surface microstructure, and other properties of untreated and treated titanium alloy are compared to study the effect on titanium alloy of laser shock peening process without protective coating.
Electronic ceramic substrates have been widely used in various markets, which include the automotive industry, electronics, aviation, and sensor due to their good thermal conductivity and thermal stability. The holes in ceramic substrates are very important for their application, many techniques are studied to drill holes of different sizes. This research presents the results of UV ultrashort pulse laser drilling of ceramic substrates with different laser parameters. Normally, the ultrashort pulse laser can be used to process materials due to its less heat-affected zone, so the heat-affected zone of the hole is also observed around the laser-drilled holes.
Laser shock peening as one kind of surface technique is used to enhance the mechanical property of metals, like aluminum alloy, stainless steel, and titanium alloy. The Ti6Al4V alloy specimens are processed with laser shock peening technology by nanosecond laser with a square laser spot. The hardness near-surface region and residual stress distribution in the top layer of Ti6Al4V alloy specimen are measured by Vickers hardness tester and hole drilling tester. The results show that the shock wave formed by laser shock peening can induce compressive residual stress in the top layer of Ti6Al4V alloy, which is beneficial for the improvement of fatigue life of Ti6Al4V alloy when it is used in aviation. The hardness of the near-surface region increases slightly in this research.
Laser shock peening is a new and important surface treatment technique that can enhance the mechanical properties of metal materials. Normally, the nanosecond laser with pulse-width between 5 ns and 20 ns is used to induce a high-pressure shock wave that can generate plastic deformation in the top layer of metals. The femtosecond laser shock peening in the air has been studied recently, which can induce higher pressure shock wave than that of traditional nanosecond laser shock peening in a very short time. The NiTi alloy is processed by femtosecond laser shock peening, then a nanoindentation device is used to measure its surface hardness and residual stress. The hardness results of NiTi alloy before and after treatment show that the femtosecond laser shock peening can increase the hardness of NiTi alloy, which also shows that the femtosecond laser can be used to perform laser shock peening on NiTi alloy without coating.
High strength steel has been used in the aviation industry and automotive body structural applications to reduce its mass through a reduction in thickness. Therefore, it is very important to enhance its mechanical property, such as microhardness. In the present research, the high strength steel samples were treated by laser shock peening (LSP) with different laser pulse energy and laser pulse width. The microhardness and residual stress were measured to compare the difference between laser energy of 3 J with 10 ns and 5 J with 20 ns. The results in the study show that the surface LSP treatment can increase the microhardness and the compressive residual stress can be found when the samples were tested by hole drilling testing.
The experiment study presents the influence of femtosecond laser shock peening (FsLSP) without a protective layer in the air on the surface hardness and surface mechanical property of NiTi shape memory alloy. Femtosecond laser shock peening is a new possibility of direct laser ablation without any protective layer under atmospheric conditions, which can produce intense shock waves with low pulse energy in the air. The average surface roughness values of the NiTi alloy samples were measured, because the surface roughness may affect its friction resistance. The results showed that the surface roughness of NiTi increased after femtosecond laser shock peening treatment. In comparison with the initial state, the coefficient of friction decreased and surface microhardness increased after femtosecond laser shock peening treatment with different FsLSP parameters. This improvement of wear properties may be attributed to the enhancement of surface microhardness and surface titanium oxide layer induced by the shock wave and laser ablation during FsLSP treatment.
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