Using millisecond pulse laser irradiating CCD detector, the interacting process between millisecond pulse laser and CCD detector was studied, the forming reason of different damage effects was analyzed, the damage process and damage laws of CCD detector under millisecond pulse laser were revealed. The results show that: with the same laser energy density, the maximum temperature and the damaged area increased with the increase of pulse number; with the same pulse number, the range of the noise widened with the increase of laser energy density, and the vertical shift register impedance values decreased with the increase of laser energy density; the microlens layer on the damaged edge of CCD detector occurred stress damage.
Established a physical model to simulate the melt ejection induced by long pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. This simulation is based on the interaction between single pulsed laser with different pulse width and different peak energy and aluminum alloy material. By comparing the theoretical simulation data and the actual test data, we discover that: the theoretical simulation curve is well consistent with the actual experimental curve, this two-dimensional model is with high reliability; when the temperature at the center of aluminum alloy surface increases and evaporation happens after the surface temperature at the center of aluminum alloy surface reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium vaporization; the keyhole appears on the surface of the target, an increment of the keyhole, the maximum temperature at the center of aluminum alloy surface gradually moves inwardly. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.
Established a physical model to simulate the melt ejection induced by long pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. This simulation is based on the interaction between single pulsed laser with different pulse width and different peak energy and aluminum alloy material. By comparing the theoretical simulation data and the actual test data, we discover that: the theoretical simulation curve is well consistent with the actual experimental curve, this two-dimensional model is with high reliability; when the temperature at the center of aluminum alloy surface increases and evaporation happens after the surface temperature at the center of aluminum alloy surface reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium vaporization; the keyhole appears on the surface of the target, an increment of the keyhole, the maximum temperature at the center of aluminum alloy surface gradually moves inwardly. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.
According to the heat conduction equation, thermoelastic equation and boundary conditions of finite, using the finite
element method(FEM), established the three-dimensional finite element calculation model of thermal elastic ,numerical
simulation the transient temperature field and stress field distribution of the single crystal silicon materials by the
pulsing laser irradiation, and analytic solution the temperature distribution and stress distribution of laser irradiation on
the silicon material , and analyzes the different parameters such as laser energy, pulse width, pulse number influence on
temperature and stress, and the intrinsic damage mechanism of pulsed laser irradiation on silicon were studied. The
results show that the silicon material is mainly in hot melt under the action of ablation damage.According to the
irradiation of different energy and different pulse laser ,we can obtain the center temperature distribution, then get the
law of the change of temperature with the variation of laser energy and pulse width in silicon material; according to the
principal stress and shear stress distribution in 110 direction with different energy and different pulse, we can get the
law of the change of stress distribution with the variation of laser energy and pulse width ;according to the principal
stress distribution of single pulse and pulse train in 110 direction, we can get the law of the change of stress with pulse
numbers in silicon.When power density of laser on optical material surface (or energy density) is the damage threshold,
the optical material surface will form a spontaneous, periodic, and permanent surface ripple, it is called periodic surface
structure laser induced (LIPSS).It is the condensed optical field of work to generate low dimensional quantum
structures by laser irradiation on Si samples. The pioneering work of research and development and application of low
dimensional quantum system has important academic value.The result of this paper provides theoretical foundation not
only for research of theories of Si and substrate thermal stress damage and its numerical simulation under laser
radiation but also for pulse laser technology and widening its application scope.
In this paper, we establish a physical model to simulate the melt ejection induced by millisecond pulsed laser on
aluminum alloy and use the finite element method to simulate the melting and vaporization process of aluminum alloy.
Compared with the conventional model, this model explicitly adds the source terms of gas dynamics in the
thermal-hydrodynamic equations, completes the trace of the gas-liquid interface and improves the traditional level-set
method. All possible effects which can impact the dynamic behavior of the keyhole are taken into account in this
two-dimensional model, containing gravity, recoil pressure of the metallic vapor, surface tension and Marangoni effect.
This simulation is based on the same experiment condition where single pulsed laser with 3ms pulse width, 57J energy
and 1mm spot radius is used. By comparing the theoretical simulation data and the actual test data, we discover that: the
relative error between the theoretical values and the actual values is about 9.8%, the melt ejection model is well
consistent with the actual experiment; from the theoretical model we can see the surrounding air of the aluminum alloy
surface exist the metallic vapor; an increment of the interaction time between millisecond pulsed laser and aluminum
alloy material, the temperature at the center of aluminum alloy surface increases and evaporation happens after the
surface temperature reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium
vaporization; the keyhole depth is linearly increased with the increase of laser energy, respectively; the growth of the
keyhole radius is in the trend to be gentle. This research may provide the theoretical references to the understanding of
the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application
of the laser materials processing and military field.
A spatial axisymmetric finite element model is established to investigate the distribution characteristics of temperature field that monopulse millisecond laser act on aluminum alloy. The thermal process of laser acting on aluminum alloy (melting, gasification and temperature drop) is simulated. Using the specific quivalent heat capacity method to simulate the solid-liquid, liquid-gas phase transition of aluminum alloy, and considering the differences of thermal physical parameters between different states (solid-liquid, liquid-gas) of aluminum alloy in the process of numerical simulation. The distribution of temperature field of aluminum alloy caused by the change of energy density, pulse width and spot radius of monopulse millisecond laser are investigated systematically by using numerical simulation model. The numerical results show that the temperature of target no longer rises after reaching the target gasification. Given the pulse width and spot radius, the temperature of target rise as the energy density increases, the laser intensity distribution is gaussian, so the temperature distribution of the target surface also shows Gaussian. The energy absorption mechanism of aluminum alloy is surface absorption mechanism, the temperature gradient in axial of the target is much lager than the temperature gradient in radial of the target surface, so the temperature rise in axial only exists a thin layer of target surface. Given the energy density and spot radius, as the pulse width increases, the power density of laser decreases, therefore the temperature of target center point decreases as the pulse width increases, and the temperature difference becomes small. As the pulse width decreases, the heat transfer in axial reduce, the deposition of energy enhances on the surface. Given the energy density and pulse width, the distribution of the temperature is enlarged as the spot radius increases, but the distribution of the temperature in axial is independent of the spot radius.
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