Papers by Keyword: Fibre Laser

Abstract: In this paper, the influence of laser surface alloying on the structure and mechanical properties of aluminium alloy was analysed. As a parent material aluminium EN AC-51300 alloy was applied. The laser surface alloying was executed by direct introduction of metallic powder Fe/Cu into the remelted area (molten pool). As a heat flux, the Hight Power Fiber Laser (HPFL) has been used. Metallic powder before the treatment was mixed in a ball mill and dried on the hot plate (90°C temperature). The mechanical and tribological properties of alloyed surface were analysed including hardness (HRF), microhardness (HV_0.1) and ball-on-plate wear test. The structure of the laser alloyed surface was evaluated by light and scanning electron microscopy.

Abstract: In paper laser thermal oxidation of austenitic stainless steels AISI 201, 304L of different surface mill finishes, the hot and cold rolled was investigated by the Ytterbium-doped fibre laser (λ=1070 nm) with an output power of 400W by varying scanning speed in the range 5÷20m/s in the air atmosphere. The influence of laser oxidation parameters on the surface colour was evaluated by colorimetric identification.

Abstract: The energy level structure of Yb3+ is analyzed, and a theoretical model is established. Theinfluence of pumping power, fiber length, reflectance of cavity mirror and other related parameters onthe performance of the laser is analyzed. The maximum output power can be achieved at a certainreflectance. The higher the input pump power, the smaller the reflectance of the rear mirror whichobtains the maximum output power. For different pumping wavelengths, the optimal length of thegain fiber is not the same, and it is also different from the optimal length determined by the minimumpumping threshold. Therefore, in the design of fiber lasers, we should consider comprehensively todetermine the appropriate fiber length. Reducing inner raduis is beneficial to improving slopeefficiency when the characteristics of the fiber itself remain unchanged.

Abstract: Ti6Al2Sn4Zr2Mo exhibits improved oxidation and creep properties compared to Ti6Al4V. Laser beam welding (LBW) is an approved process to receive narrow weld seams at high welding speeds with low heat input. Almost distortion free complex shaped structures can be joined with optimal parameters. For the optimisation of the LBW process the most relevant parameters are the welding speed, the laser input power and the gas shielding strategy. Using a fibre laser, the laser radiation is attenuated by a welding plume the so-called metal-vapour cloud (MVC). The MVC has a large influence on the laser input power. Therefore, an approach for reducing the MVC by optimising the shielding strategy using an additional gas flow in opposite welding direction is examined. Utilizing high-speed camera records, the effectiveness of the approach is assessed. Welded samples are evaluated by visual and radiographic inspection, metallographic assessment as well as microhardness measurements with regard to weld seam geometry, defects, microstructure and local mechanical properties. The obtained results are correlated to the used laser welding parameters.

Abstract: Laser technologies are considered to be unconventional technologies. Laser cutting is one of the most popular industrial operations that use a laser beam. Fibre lasers are most commonly used for cutting metallic materials. The aim of this paper is to experimentally demonstrate a procedure for determining the focal length of a laser beam from the output of the cutting head of a JK400FL fibre laser. Along with other factors, the correct position of the focal point of a laser beam cutting materials, plays a vital role in the quality of the cut and also in determining the cutting speed. It is possible to use a higher cutting speed of the laser machine, without compromising the quality of the cut.

Abstract: This article presents some results of laser processing of materials, used for the construction of microsystems and micro-sensors, e.g. Si, Al₂O₃ and zirconia ceramics. The necessity of faithful reproducing the geometry and dimensions in the micro-scale puts specific requirements for laser machining process. Laser micro-technologies must be conducted under conditions which ensure the perfect guidance of a well-focused laser beam, scanning at a suitable speed, and the laser pulse duration with proper repetition frequency. The amount of absorbed energy depends on wavelength of laser radiation and kind of material, which also influence on this process. All these conditions should take into account the need to maintain a small heat affected zone (HAZ). This guarantees keeping the true reproduction of micro-shapes and cutting edges with a different angle of lines even in micro-scale details. The present work confirms the possibility of using laser technology for such applications.

Abstract: Titanium and its alloys are nowadays widely used in many sectors: in the medical field (orthopedic and dental ones), in the architectural field, in the chemical plants field and in aeronautic [1]. In this last field it is more and more used both for its contribution to make lightweight and time durable structures and for its compatibility with new materials, first of all Carbon Fiber Reinforced Plastics (CFRP). Cutting of titanium sheets is one of the primary requirements in the fabrication of most of the components. Laser cutting offers several advantages over conventional cutting methods. It includes narrow kerf width (minimum material lost), straight cut edges, low roughness of cut surfaces, minimum metallurgical and surface distortions, easy integration with computer numerically controlled (CNC) machines for cutting complex profiles and importantly non-contact nature of the process (suitable for cutting in hostile environments and in areas with limited access) [2]. However, due to very limited literature available on laser cutting of titanium, it is very difficult to predict the cut surface quality and optimum process parameters for laser cutting, especially when dross-free cuts are required. Laser cutting of titanium and titanium alloys needs to be carried out with an inert gas, this due to the high reactivity of the titanium with the oxygen at high temperatures [3]. However when the available power is limited, as in the present case, the use of a reactive gas (air) can help to achieve cutting speed value reasonable for industrial applications. The aim of this work is to study the cutting of Ti-6Al-4V rolled sheets 1 mm in thickness, by means of a 100 W fibre laser, (SPI-Red Power) working at wavelength  = 1090 nm. The maximum cutting speed were measured in both CW and pulsed regime at different mean power and different duration. Furthermore, the kerf geometry and the heat affected zone (HAZ) were studied decreasing the cutting speed from the maximum to the 80 % of this values. The results obtained showed that both the power and the cutting speed influence the cutting kerf geometry and HAZ. In particular the synergy of power and speed, resulting roughly into the heat input, seems to rule the whole cutting process.

Abstract: A study concerning the application of fiber laser to perforate thermoplastic pre-pregs is presented. An IPG fiber laser was used to drill arrays of holes in PEKK carbon-fiber composite pre-preg material. Perforated holes were of the order of 100μm. The effects of laser perforation process parameters including the number of pulses on the geometry of the resultant holes and the thermal damage to the matrix and fibres have been investigated. Dimensional analysis and experimental results have been used to construct the laser perforation process model. Keywords: Laser perforation; Fibre laser; Process modelling; Polymer matrix composites.

Abstract: The use of high power laser technology in the cleaning and dressing of grinding wheels has been the subject of several research projects worldwide and over the last 30 years. Several projects have reported beneficial outcomes however the process has not been implemented in production. The arrival of fibre lasers may provide a viable laser source for cleaning, and ultimately dressing, of wheels. This paper reports on some preliminary data confirming this potential and that supports the need for further research effort.

Abstract: The interest in laser material processing of Carbon Fibre Reinforced Plastic (CFRP) over the past few years has increased, especially in the aerospace industry. A number of different laser groups around the world are investigating different laser sources for the express reason of developing a laser material processing centre for machining CFRP for the aerospace and automotive industry. This paper reports on the work of two such groups, in the UK and Germany, who are using fibre laser technology and a diode pumped solid state laser system. The initial results from the two studies are reported and show that these two very different laser systems offer processing capability with respect to machining CFRP.