Effect Of Scanning Velocity Research Articles

Effect of Scanning Velocity on Bending Deformation per Pulse in Sheet Metal Bending by Laser Peen Forming

Effect of Scanning Velocity on Bending Deformation per Pulse in Sheet Metal Bending by Laser Peen Forming

Regular Periodic Surface Structures on Indium Tin Oxide Film Efficiently Fabricated by Femtosecond Laser Direct Writing with a Cylindrical Lens.

Regular laser-induced periodic surface structures (LIPSS) were efficiently fabricated on indium tin oxide (ITO) films by femtosecond laser direct writing with a cylindrical lens. It was found that randomly distributed nanoparticles and high spatial frequency LIPSSs (HSFL) formed on the surface after a small number of cumulative incident laser pulses per spot, and regular low spatial frequency LIPSSs (LSFL) appeared when more laser pulses accumulated. The mechanism of the transition was studied by real-time absorptance measurement and theoretical simulation. Results show that the interference between incident laser and surface plasmon polaritons (SPPs) excited by random surface scatterers facilitates the formation of prototype LSFLs, which in turn enhances light absorption and SPP excitation following laser pulses. The effects of scanning velocity and laser fluence on LSFL quality were discussed in detail. Moreover, large-area extremely regular LSFL with a diameter of 30 mm were efficiently fabricated on an ITO film by femtosecond laser direct writing with the cylindrical lens. The fabricated LSFLs on the ITO film demonstrate vivid structural color. During LSFL processing, the decrease of ITO film thickness leads to the increase of near-infrared optical transmittance.

Study of Femtosecond Laser Ablation Effect on Micro-Processing for 4H-SiC Substrate

4H-SiC substrate was ablated by linearly polarized femtosecond (fs) laser in three direct write methods at different parameters, such as repetition rate, scanning velocity and fluence, etc. Two processing modes, transverse scanning mode (TSM) and cross irradiation mode (CIM), were introduced. The surface morphologies were observed by scanning electron microscopy (SEM) for detailed investigation. It was found that the surface morphologies differed remarkably at different processing parameters. Firstly, the shapes of micro craters fabricated at different repetition rates and ablation time duration were respectively investigated. The shape of fs laser spot was demonstrated to play an important role for the generation of micro craters. Secondly, the effect of scanning velocity on the formation of nanoripples and micro grooves were investigated. It was found that the spatial ripples could be refabricated during repeated fs laser ablation; periodic ripples and micro grooves depended on fs laser scanning velocity. Agglomerative substance was fabricated especially at slow scanning velocity. Furthermore, rippled surfaces induced at different fluence were achieved and exhibited. Regular and uniform surfaces with periodic ripples were fabricated at the fluence of 0.31∼0.38 J/cm2. Finally, CMP was carried out to study the effect of fs laser ablation on polishing.

Effect of scanning velocity on femtosecond laser-induced periodic surface structures on HgCdTe crystal

In this paper, a femtosecond laser line-scanning irradiation was used to induce the periodic surface microstructure on HgCdTe crystal. Low spatial frequency laser induced periodic surface structures of 650–770nm and high spatial frequency laser induced periodic surface structures of 152–246nm were respectively found with different scanning speeds. The evolution process from low spatial frequency laser induced periodic surface structures to high spatial frequency laser induced periodic surface structures is characterized by scanning electron microscope. Their spatial periods deduced by using a two-dimensional Fourier transformation partly agree with the predictions of the Sipe-Drude theory. Confocal micro-Raman spectral show that the atomic arrangement of induced low spatial frequency laser-induced structures are basically consistent with the crystal in the central area of laser-scanning line, however a new peak at 164cm−1 for the CdTe-like mode becomes evident due to the Hg vaporization when strong laser ablation happens. The obtained surface periodic ripples may have applications in fabricating advanced infrared detector.

Velocity and forced excitation effects on atomic friction force with deformable substrate

We have investigated the effect of scan velocity on atomic friction force in a Prandtl–Tomlinson model at finite temperature. We use a nonsinusoidal substrate potential with variable shape to capture surface features. The velocity dependence of atomic friction force is classified into two regimes: thermal and athermal regimes. We numerically find turning velocity between these two regimes, and its shape parameter dependence is determined. Furthermore, we have studied the torsional oscillation effect on a cantilever. We show that friction force can be reduced by controlling the frequency and the amplitude of the superimposed torsional oscillation at low scan velocity. The numerical calculations have shown that the substrate shape strongly affects the occurrence of resonances, so the torsional resonance frequency dependence of the shape parameter is established.

Research on Effect of Scanning Velocity on Laser Cladding AISI 304 Stainless Steel/Al<sub>2</sub>O<sub>3</sub> Composite Coating

AISI 304 stainless steel powder and Al2O3 powder was used to produce laser cladding composite coatings in order to improve the surface wear resistance of 45 steel. Microstructure of the composite coating was examined and analyzed by metallographic microscope. Microhardness and wear resistance of the composite under different scanning velocities were evaluated. The results show that the composite coating is composed of planar crystal, cellular crystal, dendritic crystal and fine equiaxed; the composite coatings under different technological parameters are made of the same phases, ferrite (α) and austenite (γ) phases. Microhardness of the composite is enhanced along with the increase of scanning velocity; effect of scanning velocity on wear loss of the composite coatings is not significant.

Femtosecond Laser Micromachining of SiC Ceramic Structures

Femtosecond laser micromachining technology shows abroad application background in the field of micro manufacturing due to its unique advantages, especially for micromachining of ultrahard materials such as Silicon carbide (SiC) ceramic. The femtosecond laser micromachining system was set up, by using the system, effects of scanning velocity and laser pulse energy on quality of micromachined features were evaluated. The optimized technological parameter was obtained as 8mW, 1mm/s with 1kHz repetition frequency respectively on the basis of the morphological characteristics and microstructure accuracy. Besides, V-shaped cavity of 300μm depth and 120°angle was generated with layer-by-layer scan machining. Thus femtosecond laser micromachining technology is an effective method for hard and brittle materials precision processing.

The Effect of Scanning Velocity on AISI 304 Stainless Steel Laser Cladding Coatings

Single and multi pass AISI 304 stainless layers tightly combined with substrate was obtained by laser cladding on the surface of 45 steel using the way of presetting powder. Effect of different scanning velocities on cladding layers was analyzed and interpreted in this paper; influence of scanning velocities on dilution rate was also acquired, the dilution rate come up to a maximum value which is 11.1% when the scanning velocity reached 800 mm/min, what is more, immersion test shows that scanning velocity has little effect on the weightlessness rate. Besides, XRD patterns shows that the cladding layers composed of ferrite and austenite phases.

Numerical Simulation of the Effects of Scanning Velocity on the Process of Laser Transformation Hardening on the Inner Wall of Pump Barrel

This study establishes a 3-D finite element model for the numerical simulation of laser transformation hardening on inner wall of pump barrel through a finite element code-SYSWELD. The change of thermal mechanical parameters with temperature is considered. The temperature field, metallurgy transformation and distribution of residual stress are predicted. The effect of scanning velocity on the temperature, martensite fraction and distribution of residual stress are studied. The results show that peak temperature in the hardened zone reaches to 1067.0°C and the maximum heating and cooling rate of hardened zone are 1.24×104°C/s and 3.68×103°C/s. After treatment, martensite can be obtained as a main phase in the hardened zone whose fraction increases with the decrease of scanning velocity. Compressive stress could be acquired in the hardened zone while the peak of tensile stress exists in the HAZ.

扫描速度对硼化物金属陶瓷激光熔覆层组织和性能的影响

扫描速度对硼化物金属陶瓷激光熔覆层组织和性能的影响

扫描速度对硼化物金属陶瓷激光熔覆层组织和性能的影响

扫描速度对硼化物金属陶瓷激光熔覆层组织和性能的影响

Effect of Scan Velocity on Resulting Curvatures during Laser Beam Bending of AISI 1008 Steel Plates

Forming is a flexible process, by which a variety of different shapes can be produced through mechanical, thermo-mechanical, or thermal [Laser Beam Forming] process. Laser beam forming [LBF] process has been successfully applied to a variety of sheet metal components thereby plastically deforming it. This paper investigates the producing effect of scan velocity on the resulting curvatures and resulting properties of the bent components. The results show that three different curvatures (120, 180 and 240 mm) of 4 mm AISI 1008 low carbon steel plate was successfully produced under an optimized set of process parameters and a direct relationship was observed between the scan velocity and the resulting curvatures. Furthermore, microstructural characterization revealed that the grain structures of the irradiated surfaces are refined with cooling than the bottom due to the nucleation rate of new grains formed at the irradiated surface.

Effect of Scanning Velocity on Surface Hardening for Ti Substrate by CO<sub>2</sub> Laser

In this document, titanium matrix composite layer was produced by continuous wave CO2 laser system. Microstructure was analyzed by using VHX-600K metallographic microscopy. Results show that the decreasing of laser beam scanning velocity lead to the increasing of the heat energy absorbed by molten pool, the reduction of curvature radius of the laser clad layer, the increasing of width and depth at cross section of laser clad layer, and fine dendrites in the surface of laser clad layer. Microstructure changes both in the laser clad layer and the interface under the common action of melt flow and life time of molten pool.

The effect of scan velocity on the measurement of semiconductor parameters by optical-beam excitation

We analyze the effect of the speed of scanning a monochromatic light source across a p-n junction which is perpendicular to the sample surface. It is found that the collected junction current is sensitive to both the magnitude of scan speed and also its direction. This provides a simple method of determining both the minority-carrier-diffusion coefficient and lifetime independently. Scan speeds as small as 10% of the diffusion velocity can significantly modify the form of the junction current versus scan-position curve. The conclusions apply qualitatively to analogous techniques in the scanning electron microscope.