In order to study the phenomenon of spallation in titanium alloy under nanosecond laser shock, and on the basis of analyzing the advantages of laser shock forming technology and the relevant domestic and foreign research status, this paper conducts numerical simulation and experimental research on laser shock forming of titanium alloy sheet, systematically studies the effect of different laser energy and impact times on laser shock forming effect, and the deformation law of TC4 titanium alloy material in the process of laser shock forming are analyzed. The simulation model analyzes the deformation of the target material based on the target displacement cloud map at different times. In addition, the laser shock experiment verifies the correctness of the simulation results with experimental data. The results show that under the single-variable method, as the energy gradually grows, the target shape variable also increases. As the number of impacts increases, the target deformation gradually increases until cracks appear. These results provide a basis for setting laser parameters and selecting targets when nanosecond laser strikes the TC4 target.
A novel optoelectronic measurement system using a beam-shading technique is developed to detect the dynamic characteristics of a metal sheet under laser shock in laser shock forming (LSF), including deformation, strain, and strain rate. Experiments conducted yield the dynamic deformations at two points on an aluminum sheet with a thickness of 0.25 mm in LSF. The average strain rates calculated in the experiments are 5.46×10 2 , 4.71×10 2 , and 3.59×10 2 s −1 when the targets were hit by laser pulses with energies of 5, 6, and 8 J, respectively. The results show that the strain rate induced by laser shocking is not at the ultrahigh level of 10 6 –10 7 s −1 as generally estimated in past studies, which offers an experimental reference for the deformation study of strain-rate-dependent metal materials in LSF.
When a short pulse of a Q-switched high-power laser hit surface of materials, laser energy would be absorbed rapidly,
thus producing explosive vaporization, and almost at the same time a high-pressure shock wave was induced, called laser
shock wave. This ultra-high pressure induced by high power laser had been applied in the fields of basic research and
engineering application such as inertial confined fusion, laser shock processing, etc. Influence of variable laser power
density on laser shock wave was studied in this paper. Influences of variation of laser wavelength and pulse duration on
laser shock waves were also discussed in laser shock processing. Piezoelectric Polyvinylidene Fluoride (PVDF)
transducer and TDS3052B Digital Oscilloscope were applied in our experiments to measure the piezoelectric wave of
PVDF and the corresponding stress wave induced by laser in real time. Differences and relations between laser-induced
shockwave and laser pulse in laser shock processing were researched according to the obtained waves, and the detailed
analyses of their causes were given based on the formation of laser-induced shock wave. The research results could have
important implications for a better understanding of characteristics of laser shock wave and further studies into the
interaction between high-power laser and materials.
Life sciences is an important field of scientific research nowadays .On this important subject to the human blood measure,
this paper puts forward applying infrared spectrum analysis technology to this research subject less likely to be set foot
of diagnosis on disease. This paper gives infrared spectrums of cholesterol serums of normal and abnormal bloods
sample within the range of certain frequency spectrum. By comparing the characteristic of the spectrums, we can
measure and judge whether the serum sample is normal or not. Results indicate the differences on the absorption rate,
position of absorption peak between normal and abnormal blood sample. A new method of medical diagnosis and
analyses is presented. Compared with the other existed blood measures methods, it is convenient and easy to popularize
for the serum infrared spectrum characteristic analysis method presented in this paper, meanwhile it has the merit of
analyses simple fast.
The focusing system is very important for laser processing, especially for laser micro-processing, whose characteristics influence directly the quality of laser processing. A new optical system from the potive axicon and spherical lens combination is proposed in this paper to generate the diffraction-free beam. Only one axicon is needed in this system to produce the variable diffraction-free beam spot of micro order by changing the ordinary cheap spherical lenses. If such an optical system is used as the focusing system for laser micro-processing, the sensitivity to the workpieces' position would be zero and the adaptability to the flatness of the workpieces' surface could be enhanced. Moreover, such a system could adapt well to the different processing criterion by changing the ordinary spherical lenses and would also have potential application in the measurement field.
Using the technique of Lie operator algebra, we present a recursive formulation for calculating the third and fifth order aberrations of a general optical system and express the third and fifth order aberration coefficients in the 7×7 and 12×12 matrix forms, respectively. One advantage of our formulae is their explicit algebraic expressions suitable for practical application and numerical calculations, another is that the formulae provide a formulation of the matrix method for general nonlinear transformation and the generalized matrix method employing Lie algebraic tools proposes a new view for aberration optics computation. With the method it should be possible to evaluate all the aberration terms for any optical system. Applications of the matrix method are illustrated with thick lens and some well known imaging systems.
An orthogonal projection sampling method is proposed in this paper and is applied in the reconstruction of incomplete data field by using the prior knowledge algorithm based on the modified ART, by which the satisfying reconstruction results can be obtained even with less sampling directions and limited sampling angular range. The Mean Square Error (MSE) and peak value between the origin field, the reconstructed field using orthogonal projection sampling method and traditional projection sampling method are analyzed with the numerical simulation of computer. The results indicate that the orthogonal projection sampling can reduce the MSE greatly in the reconstruction of incomplete data. Thus our researches provide a new means for the reconstruction of incomplete data field.
KEYWORDS: Free space, Global system for mobile communications, Beam propagation method, Gaussian beams, Matrices, Systems modeling, Diffraction, Laser beam propagation, Laser applications, Coherence (optics)
We investigate the twist properties of the ten-parameter family of partially coherent general anisotropic Gaussian Schell model (AGSM) beams passing through first-order optical systems. By utilizing the generalized Huygens-Fresnel diffraction integral for asymmetric first-order optical systems, the explicit twist expressions for the principal axes of intensity distribution, transverse coherence distribution and the principal curvatures of phase front in the cross-spectral density function of AGSM beams are obtained. In some special cases when the beams are the twist Gaussian Schell-Model, Gaussian Schell-Model, Li-Wolf and Gori-Guattari beams, our results reduce to well known expressions. It is shown that, under some conditions, although the ten parameters are all not zero and any one of the intensity distributions, transverse coherence distribution and the phase front has its independent principal axis, the beam spot does not twist when the beam passing through free-space. As a result, special partially coherent beams called the twisted-free ten-parameter family of partially coherent general anisotropic Gaussian Schell model (TF-AGSM) beams are introduced and their properties are discussed.
The Optical Computerized Tomography (OCT) is an important means for the research of flow field. In this paper, the Algebra Reconstruction Technology (ART) of OCT is discussed. An improvement for the reconstruction equations has been presented. A property matrix including the prior knowledge is introduced in the reconstruction, and an unfixed ultra relaxation coefficient is adopted, that is to say, giving the coefficient a dynamic range. By this way, the reconstruction precision will be greatly increased, thus the reconstructed field will approach the actual field.
In our paper, OCT is used to measure the distribution of temperature field generated by disc, hemisphere etc. systematically for the first time. The method of this technology is discussed firstly. Secondly the gathered interferograms through Fabry-Pérot (F-P) rotary interferometer are provided and the 3-D temperature distributions of all the fields are given. Then the results are compared with the actual measured value, and the difference is given, which shows the precision can reach 5%. Furthermore, the temperature distributions of several complex objects combined by simple objects are also measured, and the results indicate that the temperature field of complex objects can be combined by that of simple objects through certain way. Because all the complex objects can be regarded as the combination of the simple objects, our researches establish the theoretical and experimental foundations for the research on the temperature field of complex objects.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.