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August 2013

Volume 25, Issue 4 (partial)

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Experiment investigation on microstructure and mechanical properties of TC17 titanium alloy treated by laser shock peening with different laser fluence

Xiangfan Nie, Weifeng He, QiPeng Li, Nidong Long, and Yan Chai

J. Laser Appl. 25, 042001 (2013); http://dx.doi.org/10.2351/1.4800444 (6 pages)

Online Publication Date: 01 May 2013

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In this paper, microstructure, microhardness, and residual stress of TC17 titanium alloy treated by laser shock peening (LSP) with different laser fluence were examined and compared by x-ray diffraction, scanning electron microscope, transmission electron microscope, microhardness test, and residual stress test. The results of microstructure point out that microstrains and grain-refinement are generated in the material surface layer which is a severe plastic deformation layer. In relation to the microhardness and residual stress, the results indicate that LSP can obviously improve the hardness and introduce a great compressive residual stress which also has a good thermal stability.
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42.62.-b Laser applications
62.20.Qp Friction, tribology, and hardness
81.40.Lm Deformation, plasticity, and creep
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.65.-b Surface treatments
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
62.20.fq Plasticity and superplasticity

Three-dimensional microstructure characteristics and evolution on dentin surface induced by ultraviolet laser irradiation

Qiurui Li, Lingfei Ji, Xiaochuan Chen, and Yijian Jiang

J. Laser Appl. 25, 042002 (2013); http://dx.doi.org/10.2351/1.4801321 (8 pages)

Online Publication Date: 01 May 2013

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In texturing dentin surface by KrF laser with the fluences of 200–800 mJ/cm2, it is observed the irradiated surface topography has different characteristics with that irradiated under high fluence above 1000 mJ/cm2 reported in previous studies. The formation threshold fluence of the microstructure consisted of erected microcylinders was determined at 400 mJ/cm2. By scanning electron microscopy including fine examination of a single microstructure unit under high magnification, the microstructure formation and evolution tending to the fashion of high fluence were given. Analysis of the ablation details captured by high-speed photography confirmed the development mechanism of the texturing microstructure. Raman analysis showed the composition of the laser textured dentin underwent changes. Although the texturing is related to the characteristics of the dentin tissue, laser parameters play a decisive role in the controlling of the shape and the height of the three-dimensional microstructure. The combination of our work and the previous work by Sivakumar et al. [J. Laser Appl. 18(4), 330–333 (2006) and Lasers Med. Sci. 21, 160–164 (2006)] demonstrates laser fabrication of the three-dimensional microstructure with different topography features on dentin surface is controllable.
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87.50.wp Therapeutic applications
42.62.Be Biological and medical applications

Passive and active protective clothing against laser radiation

Michael Hustedt, Christian Hennigs, Stefan Kaierle, Wojciech Gołębiowski, Dirk Wenzel, and Andreas Hutter

J. Laser Appl. 25, 042003 (2013); http://dx.doi.org/10.2351/1.4802762 (8 pages)

Online Publication Date: 01 May 2013

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In order to provide machine operators using, e.g., industrial laser processing machines or hand-held laser devices with adequate protection against accidental laser irradiation of the skin, passive and active solutions based on high-tech technical textiles have been investigated. These solutions can be used for personal protective clothing (PPC) or curtains. The passive solutions are constructed as multilayer systems with high passive protection levels with respect to near-infrared laser radiation. The incorporation of sensors into the multilayer structure is able to increase the protection level significantly by providing the ability to deactivate the laser source upon irradiation above a threshold and subsequent signaling. In order to classify the new laser PPC, a test procedure and a corresponding testing set-up have been developed, which could be the basis for an intended standardization process.
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42.60.-v Laser optical systems: design and operation

On the exposure limits for extended source multiple pulse laser exposures

Brian J. Lund and Karl Schulmeister

J. Laser Appl. 25, 042004 (2013); http://dx.doi.org/10.2351/1.4802761 (11 pages)

Online Publication Date: 13 May 2013

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The proposed revisions to the ANSI Z136, ICNIRP, and IEC 60825-1 laser exposure limits for multiple pulse ocular exposure for wavelengths from 400 to 1400 nm are examined for pulse durations tp ≥ tmin (Ti). The three rules that are defined to be applied for multiple pulse exposures (or for classification for IEC 60825-1) are compared to identify criteria for which one of the rules is the critical one, i.e., the rule that limits the energy per pulse for a given exposure or product emission. Such a comparison can help to simplify a safety analysis, but also guide the design of systems for which the output is to be maximized yet still be classified as a Class 1 or Class 2 laser system.
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87.50.W- Optical/infrared radiation effects

Calculation of peak intensity for Yb3+:YAG short pulse from a ring cavity including spectral information

Zhiyun Huang

J. Laser Appl. 25, 042005 (2013); http://dx.doi.org/10.2351/1.4805094 (7 pages)

Online Publication Date: 16 May 2013

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On the basis of the spectral information, a theoretical model is developed to calculate the peak intensity of the short pulse from an active continuous wave injected ring cavity with Yb3+:YAG amplifier. Starting from rate equation, the formula describing the short pulse is obtained. As a computable model, it takes into account the pump absorption saturation and the laser reabsorption. By this model, the peak intensities of the short pulse under different cases are analyzed.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Thermal stress distributions and microstructure in laser cutting of thin Al–Si alloy sheet

Syed Sohail Akhtar, Bekir Sami Yilbas, and Emin Bayraktar

J. Laser Appl. 25, 042006 (2013); http://dx.doi.org/10.2351/1.4807081 (12 pages)

Online Publication Date: 22 May 2013

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In the present study, laser cutting of thin aluminium–silicon alloy sheet is carried out and the temperature and stress fields are predicted using the finite element code. Surface temperature predictions are validated with the thermocouple data. The changes and geometric features of the cut sections are examined through scanning electron microscope, energy dispersive spectroscopy, and x-ray diffraction. It is found that the high conductivity of aluminum–silicon alloy increases the cooling rates and influences the thermal stress field in the cutting section. The striation patterns are formed at the kerf surface and some small dross attachments are observed at the cut edges.
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42.62.Cf Industrial applications
02.70.Dh Finite-element and Galerkin methods
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
62.20.-x Mechanical properties of solids

Ablation and cutting of carbon-fiber reinforced plastics using picosecond pulsed laser radiation with high average power

J. Finger, M. Weinand, and D. Wortmann

J. Laser Appl. 25, 042007 (2013); http://dx.doi.org/10.2351/1.4807082 (5 pages)

Online Publication Date: 22 May 2013

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In this paper, processing of carbon-fiber reinforced plastics (CFRPs) using ps pulsed laser radiation with an average power of up to 80 W is investigated. The influence of average power, scanning speed, and repetition rate on the ablation rate and the width of heat affected zone is evaluated and discussed. Processing with a heat affected zone smaller than 5 μm and ablation rates of almost 100 mm3/min are achieved. Finally, precise cutting of 2 mm thick CFRP samples by repetitive ablation of a 350 μm groove with negligible heat affected zone is demonstrated.
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81.05.Qk Reinforced polymers and polymer-based composites
79.20.Eb Laser ablation

Analysis of Yb:YAG thin disk laser resonator considering thermal lens effects: Experimentally and by Laser Cavity Analysis and Design

M. Asl Dehghan, M. H. Daemi, S. S. Seyed Zamani, and M. Shayganmanesh

J. Laser Appl. 25, 042008 (2013); http://dx.doi.org/10.2351/1.4807175 (5 pages)

Online Publication Date: 22 May 2013

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In this paper, a precise calculation of thermal lensing effects of a face-pumped Yb:YAG thin disk is presented. First, in a V-shaped resonator, the spatial profiles of pump power on disk active medium at different pump powers were recorded. Then the results were used to examine the three dimensional changes of refractive index and their effects on output power and beam quality through Laser Cavity Analysis and Design software. Finally, the experimental results of M2 and output power measurements were compared with theoretical simulations.
Show PACS
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
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