Hotspots, or local fluctuations in irradiance, in a laser beam can often skew its Gaussian distribution. Read on if you’re interested in an easy way to calculate power density – even in your head. 3.2. Laser engineers and technicians are often required to calculate a laser’s power density to determine whether a beam would damage an optic or sensor or for other various applications. The configuration of the model is shown in Fig. Both the American National Standard and the Federal Aviation Administration use this definition for laser safety calculations. As evaluated in previous chapters, the pressure induced by LSP is a function of the laser power density (Fabbro et al., 1998; Montross et al., 2002). Residual stress profile in the depth of section after single LSP. Laser power density and interaction time show major effects on the extent of thermal damages in laser processing. From these you can calculate the divergence (actually convergence) angle by common trigonometry. The plasma pressure pulse induced by LSP is a function of laser power density (Berthe et al., 1997). Gabrielle is the marketing manager at Gentec-EO. This is due to the equivalent average power being condensed into an incredibly short pulse duration. can quickly and easily be interchanged to optimize printing for all application types. Figure 4.16(a) shows that the surface residual stress profiles are slightly changed with only an increase of 10% in the peak compressive stress as a result of increasing the pressure, but the tensile residual stress is induced near the centre of the impact zone. Clauer (1996) reported this phenomenon for LSP on a 1.5 mm thick 4340 steel sheet and it was found that the tensile residual stress at the mid-plane of the section was higher after five shots. For quasi-CW lasers, ultrafast pulsed lasers with a repetition rate above 50 KHz, the peak irradiance can be significantly higher than that of a normal pulsed laser with equivalent average power. What happens when laser power is substantially increased, yet the area to which that power is delivered remains constant? The results in Fig.

The predicted increase in the plastically affected depth correlates well with the experimental observation on aluminium alloys that the compressive residual stress could be driven deeper below the surface by increasing the pulse pressure (Clauer, 1996; Peyre et al., 1996). 3.1. To simplify your calculations, we provide curves for minimum and maximum power density for each of our beam profilers. Your email address will not be published. Both power and energy densities are volumetric amounts, so the resulting cut made by the laser may not be as accurate and could be off-center., Effect of Laser Spot Size on Tissue Distribution of Light Energy. 4.16. 17.3.5. With increasing laser powers introduced into its systems, Optomec faced the challenge of how to keep a consistent power density and thus a stable conductive process over a wide range of laser powers. The rest of the energy is transmitted by the material. The magnitude of surface residual stress is significantly increased when the peak pressure level increases. The residual stress field with respect to changes in impact pressure was also evaluated by 3D FE analyses. Operation. In welding of various metals and alloys with high power CW laser, porosity such as a large pore of more than 1 mm size, root porosity, porosity near the fusion boundaries of the butt or lap joint, small porosity of about 0.1–0.4 mm or less than 0.1 mm size, and healed porosity filled with melt during solidification may be present in the weld fusion zones, as illustrated by the examples of CO2 laser welds of aluminum alloys in Fig. 2.3. The focused laser spot size is determined by three factors: the laser fiber cable diameter, the collimator lens focal length, and the focus lens focal length. Distribution of plastically affected depth (Lp) along the radius with respect to different peak pressures for single LSP.
In the experiment of Ballard and his colleagues (Ballard et al., 1991), the surface of a metal specimen (35CD4 50HRC steel) was irradiated by a square laser spot of 5 × 5 mm with laser power density of 8 GW/cm2 and duration of 30 ns.
The critical laser energy density for SLM of near fully dense Ti2448 is about 33 J/mm 3 [28], which is about one-third that of cp-Ti and Ti-6Al-4V (both of which are around 120 J/mm 3 [29]). How to cite the article; suggest additional literature. However, the plastically affected depth (L1 for P = 3.5 GPa, L2 for P = 4.0 GPa, L3 for P = 5.0 GPa) associated with the compressive residual stress slightly changes in a range of 0.085–0.1 mm in the depth (at r = 1.5 mm), depicted in Fig. Author: Dr. Rüdiger Paschotta The term power density is sometimes used as a short form of power spectral density in the context of noise specifications. In micromachining applications, users will not be able to discern the problem by simply measuring irradiance or fluence.


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