TEMPLUM: A Process Adapted Numerical Simulation Code for The 3D Predictive Assessment of Laser Surface Heat Treatments in Planar Geometry

A process adapted numerical simulation code for the 3D predictive assessment of laser heat treatment of materials has been developed. Primarily intended for the analysis of the laser transformation hardening of steels, the code has been successfully applied for the predictive characterization of other metallic and non metallic materials posing specific difficulties from the numerical point of view according to their extreme thermal and absorption properties. Initially based on a conventional FEM calculational structure, the developed code (TEMPLUM) reveals itself as an extremely useful prediction tool with specific process adapted features (not usually available in FEM heat transfer codes) in the field of laser heat treatment applications

Finite element method modeling applied to laser crystallization of amorphous silicon

The crystallization by laser of amorphous or microcrystalline silicon films allows to obtain thin, high-quality, polycrystalline Si films, being a very promising method for diminishing costs in the microelectronic and solar cells sectors. During a laser crystallization process, light is partially absorbed in the amorphous silicon film, heating the sample and, if the temperature rises high enough, causing the reorganization of the film structure into a crys- talline one. In this work we show both experimental results on the crystallization of non-hydrogenated silicon thin-films performed by a continuous wave infrared laser are included, as well as a study of the process with a simple finite elements (FEM) numerical model based in the dimensional non-linear heat transfer equation with a steady heat source

Laser crystallization of silicon and study by finite element modelling

Laser crystallization of amorphous or microcrystalline silicon films to obtain high-quality polycrystalline films is one of the most promising methods for diminishing costs in the microelectronic and solar cells sectors. During a laser crystallization process light is partially absorbed by the amorphous silicon, heating the sample and, if the temperature rises high enough, causing the reorganization of the film structure into a crystalline one. In this work we show results on the crystallization of non-hydrogenated silicon thin-films by a continuous wave infrared laser, as well as a study of the process with a simple finite elements method (FEM) numerical model based in the dimensional non-linear heat transfer equation with a steady heat source

Predictive assessment of plasma dynamics effects on the shock transformation of metallic alloys by laser shock processing

Laser shock processing (LSP) has been presented as an effective technology for improving surface mechanical and corrosion properties of metals, and is being developed as a practical process amenable to production engineering. The main acknowledged advantages of the laser shock processing technique consist on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly, the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. In the present paper, practical results at laboratory scale on the application of Laser Shock Processing are presented showing the obtained tensile residual stresses relaxation along with corresponding preliminary results about the resulting mechanical properties improvement induced by the treatment

PERBANDINGAN MODEL PEMBELAJARAN CORE (CONNECTING, ORGANIZING, REFLECTING AND EXTENDING) DAN DISCOVERY LEARNING DALAM PEMBELAJARAN MATEMATIKA TERHADAP KEMAMPUAN PEMECAHAN MASALAH MATEMATIS DAN SELF-REGULATED LEARNING SISWA SMA

Pada pelaksanaan proses pembelajaran dengan menggunakan model pembelajaran Discovery Learning terlihat bahwa interaksi antar siswa masih sangat kurang. Selama proses diskusi, sebagian besar kelompok belum melibatkan setiap anggotanya karena anggotanya mengerjakan LKS secara individu, sehingga diskusi didominasi oleh beberapa siswa saja. Akibatnya, ketika dihadapkan dengan persoalan matematika siswa kurang mampu untuk menyelesaikannya. Salah satu upaya untuk mengatasi masalah tersebut adalah dengan menggunakan model pembelajaran inovatif lainnya. Salah satunya dengan penggunaan model pembelajaran CORE (Connecting, Organizing, Reflecting, dan Extending). Model pembelajaran CORE merupakan model pembelajaran dengan metode diskusi dengan menghubungkan informasi lama dengan informasi baru, mengorganisasikan sejumlah materi yang bervariasi, merefleksikan segala sesuatu yang peserta didik pelajari, dan mengembangkan lingkungan belajar. Tujuan dari penelitian ini adalah mengkaji perbedaan kemampuan pemecahan masalah matematis dan Self-Regulated Learning siswa yang menggunakan model pembelajaran CORE dengan siswa yang menggunakan model pembelajaran Discovery Learning dalam pembelajaran. Adapun metode penelitian yang digunakan adalah kuantitatif eksperimen, dengan desain kuasi eksperimen. Populasi dalam penelitian ini adalah seluruh siswa SMAN 13 Bandung. Dua dari tiga belas kelas XI yang ada dipilih sebagai sampel penelitian. Instrumen yang digunakan adalah tes dan angket. Analisis data yang digunakan adalah uji kesamaan dua rerata dengan uji-t dua pihak menggunakan Independent Sample T-Test. Berdasarkan analisis pada keseluruhan tahapan penelitian dapat disimmpulkan bahwa: 1) Kemampuan pemecahan masalah matematis siswa SMA yang memperoleh model pembelajaran CORE tidak lebih baik dari kemampuan pemecahan masalah matematis siswa SMA yang memperoleh model pembelajaran Discovery Learning, 2) Self-Regulated Learning siswa yang dalam pembelajaran matematikanya menggunakan model pembelajaran CORE lebih baik daripada siswa yang menggunakan model pembelajaran Discovery Learning. Kata Kunci: CORE (Connecting, Organizing, Reflecting, and Extending), Discovery Learning, Model Pembelajaran, Pemecahan Masalah Matematis, Self-Regulated Learning

Optimization of interferometric photonic cells for biochemical sensing based on advanced high sensitivity optical techniques

The integration between micro-nano fluidics and optics is a new emerging research field, with promising high impact applications in the area of optical biosensing devices. This is the case of tunable Mach-Zehnder interferometers, photonic crystals and ring resonators, which have been demonstrated recently. Recent investigations1 have demonstrated that by combination of the simultaneous used of Ellipsometry, Reflectometry and Spectrometry based technologies broadly used in semiconductor industry at sub-micron spot-size level and advanced photonic structures, a relevant improvement can be achieved at the level of performance of the current state of the art for label-free biosensing and nano-fluidics metrology. The variation in the effective index of refraction can be easily detected in micron/sub-micron domains due to the fact of using several reflectivity profiles and optical responses simultaneously, making possible to remove ambiguities in the sensing interrogation process. To achieve this novel bio-chemical sensing system, it is proposed to combine the miniaturization of sub-micro-holes based Interferometric photonic structures in combination with sub-micron spot size advance optical techniques holistically. Thus, optical sensing system is based on the observation of external reflectivity profile of the high sensitive photonic structures. The reflectivity profile provides four magnitudes which can be used to assess the photonic structures response. These are the reflected amplitude and phase of the electric field components polarized parallel (p) and perpendicular (s) to the plane incidence. The reflected light of the photonic structures produce spectra interference patterns as a function of the angle of incidence for p and s polarization directions and as a function of the spectral range. These patterns are the fundamental source of information to detect the biomolecules binding in the sensing surfaces, ultra small fraction of volumes and flow control in sub-micron domains. Theoretical calculations at CLUPM demonstrate that a detection limit of 10-7 R.I.U. and surface concentration detection limit of 0.1 pg/mm2 are feasible

Numerical Thermo-Mechanical Modelling Of Stress Fields and Residual Constraints in Metallic Targets Subject To Laser Shock Processing

In the analysis of the thermomechanical behaviour of the target material subject to Laser Shock Processing (LSP), most of the simplified models used for the analysis of its residual shocked state rely on rather simple estimations or material response equations that rarely take into account a detailed description of the material subject to a simultaneous dynamic compression and either deformation-induced or plasma-driven thermal heating. The calculational system developed by the authors (SHOCKLAS) includes a coupled analysis of the pressure wave applied to the target material as a result of the plasma buildup following laser interaction and the shock wave propagation into the solid material with specific consideration of the material response to thermal and mechanical alterations induced by the propagating wave itself (i.e. effects as elastic-plastic deformation, changes in elastic constants, etc.). The model is applicable to the typical behaviour shown by the different materials through their dynamic strain-stress relations. In the present paper, the key features and several typical results of the developed SHOCKLAS calculational system are presented. In particular, the application of the model to the realistic simulation (full 3D dependence, non linear material behaviour, thermal and mechanical effects, treatment over extended surfaces) of LSP treatments in the experimental conditions of the irradiation facility used by the authors is presente

Analysis of plasma thermal surface effects on the residual stress field induced by LSP in Al2024-t351

In Laser Shock Processing (LSP) a high intensity pulsed laser beam is focused at the interface between a metallic target and a transparent confining material (normally water) that induces a residual stress distribution in the target material. Without a protective coating thermal effects are present near the target surface. A calculational model has been developed, able to systematically study LSP processes, starting from laser-plasma interaction and coupled thermo-mechanical target behavior. We present results obtained in LSP treatments without coating. In particular the relative influence of thermal/mechanical effects shows that: each effect has a different temporal scale and thermal effects are limited to a small region near the surface; repeated pulses increase maximum compressive residual stress and the depth of the compressive residual stress region; compressive residual stresses very close to the surface level can be induced even without any protective coating through the application of adjacent pulses

Scientific and Technological Issues on the Application of High Intensity Lasers to Material Properties Modification: The case of Laser Shock Processing of Metallic Alloys

Laser Shock Processing (LSP) has been practically demonstrated as a technique allowing the effective induction of residual stresses fields in metallic materials allowing a high degree of surface material protection. Experimental results obtained with commercial Q-switched lasers prove complete feasibility at laboratory scale. Depending on initial material mechanicla properties, the remaining residual stresses fields can can reach depths and maximun values providing an effectively enhanced behaviour of materials against fatigue crack propagation, abrasive wear, chemical corrosion and other failure conditions. This makes the technique specially suitable and competitive with presently use techniques for the treatment of heavy duty components in the aeronautical, nuclear an automotive industries. However, according to the inherent difficulty for prediction of the shock waves generation (plasma) and evolution in treatedmaterials, the practical implementation of LSP processes needs an effective predictive assessment capability. A physically comprehensive calculational tool (SHOCKLAS) has been developed able to sistematically study LSP processe

Laser induced forward transfer of silver pastes for printing of fingers in c-si cells.

The main objective of this work is to adapt the Laser Induced Forward Techniques (LIFT), a well- known laser direct writing technique for material transfer, to define metallic contacts (fingers and busbars) onto c-Si cells. The silver paste (with viscosity around 30-50 kcPs) is applied over a glass substrate using a coater. The thickness of the paste can be control changing the deposit parameters. The glass with the silver paste is set at a controlled gap over the c-Si cell. A solid state pulsed laser (532 nm) is focused at the glass/silver interface producing a droplet of silver that it is transferred to the c-Si cell. A scanner is used to print lines. The process parameters (silver paste thickness, gap and laser parameters -spot size, pulse energy and overlapping of pulses) are modified and the morphology of the lines is studied using confocal microscopy. Long lines are printed and the uniformity (in thickness and height) is studied. Some examples of metallization of larger areas (up to 10 cm x 10 cm) are presented