R&D (Research and Development Activities) / Theses

Research areas of Laser Technology Research and Application Center

THESES

Laser beam processing of carbon fiber reinforced composite materials surfaces to increase adhesive joining strength

MSc / 2018

Autor: YALÇIN ERDOĞAN
Supervisor: Assoc. Prof. ERHAN AKMAN
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 522365

Carbon fiber reinforced composites (CFRC-Carbon Fiber Reinforced Composites) are highly preferred composite materials in the aerospace or automotive industry due to their advantages such as extraordinary durability and low density. Carbon fiber reinforced composites usage increase day by day according to the needs of different sectors such as aerospace, military applications, turbines, automotive, medical and sports equipment. Composite parts are usually produced by combining multiple parts if the application is large and complex. Joints are the weakest part of the structure as naturally. Therefore, the manufacture of joints is very important. The process of bonding carbon fiber composites to one another has many difficulties. The mechanical joints damage the fibers which serve as load carriers and cause high stress buildup at the joints, which causes the joint to be damaged at a lower expected load. At this point, adhesive bonding, which is considered as an alternative technique, offers advantages such as lightness, tightness, corrosion and cost compared to mechanical connection methods. The most important factor that determines bonding quality in the adhesive bonding process is perhaps the material surface. In order to provide a strong and durable adhesion bonding, good adhesion between the adhesive and the material should be provided. This is accomplished by processing composite surfaces prior to bonding. Pretreatment will remove the weak boundary layers on the surface, change the surface energy and improve the micro photographic structure of the surface. As an alternative to conventional methods, surface treatment with laser is a technique that has the potential to be used in the processing of carbon fiber reinforced composites. The amount of heat transferred by the laser beam to the surface can be controlled by a number of different parameters including pulse duration, pulse energy and repetition rate with the help of the today's technology. In addition to these, the material response differs to the laser wavelength. This allows the surface to be processed with precision that is not possible with any other technique. In this study, the surface cleaning process of adhesive bonding of Carbon Fiber reinforced Composites was performed with different laser types. Radiation was given in infrared and ultraviyolet region. The strength is increased by the changes made in the laser parameters. The mechanical and spectroscopic analysis were carried out for the surface treatment.Its suitability for adhesion were determined in comparison with the single lap tensile tests after bonding.

Keywords: Carbon Fiber Reinforced Composite Materials Surface Treatment with Laser Adhesion Bonding

Determination of cutting and drilling parameters of fiberglass reinforced polymeric composite materials using laser

MSc / 2018

Autor: MEHTAP TÜRKMEN
Supervisor: Prof. Dr. ERSİN KAYAHAN
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering ; Polimer Bilim ve Teknolojisi = Polymer Science and Technology
Subject: Kompozit malzemeler = Composite materials ; Kompozit polimerler = Composite polymers ; Kompozitler = Composites ; Lazerle delme = Laser drilling ; Lazerler = Lasers
Thesis No: 521829

Fiberglass is produced from the materials such as silica, colemanite, aluminum oxide and soda. These materials are blended at high temperatures in glass furnaces and then flowed through small holes (micron level) under high pressure to produce fiberglass. Fiberglass is most used in fiber reinforced polymer composite production. Strength of the materials is very high, the thermal resistances are very low and high resists against to chemicals. It is also no absorbs humidity and have high electrical resistivity. Fiberglass reinforced polymeric composite materials are obtained by molding together the reinforcing material and the resin (matrix) used as the carrier. The molding process is carried out in many different ways. The important thing in the process is that the matrix can be wetted properly with fiberglass. In the molding process, the matrix is used for transmission and distribution of force to the fibers, protection of the fibers from the environmental effect sand damages, increase of the toughness of the composite material and blocking cracks and broken. Fiberglass reinforced polymeric composites have high abrasion resistance and are very lightweight, therefore, it is used in many sectors such as aerospace, space technology, automotive, food, construction, entertainment, technology and so on. In the used production process of glass fiber reinforced polymeric composites, cutting of burrs forms after the molding process and smoothing which is part of production processes are performed mechanically. This processes high cost, time loss and increases error rates. In this work, therefore, laser cutting and drilling operations were performed on this material. Optimum laser parameters and cutting speeds are determined. The glass fiber reinforced polymeric composite plates with 5 mm thickness were successfully cut and drilled by Nd: YAG lasers which have different pulse width. The optimum laser parameters were also determined.

Keywords: Fiberglass Fiberglass Reinforced Polymeric Composite Laser Drilling Laser Cutting Nd:Yag Lasers Polymeric Composite

Optical design of a thermal infrared imager for a high altitude platforms

MSc / 2017

Autor: ELİF KARA
Supervisor: Assoc. Prof. ERSİN KAYAHAN
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 474062

The aim of this study is to create an optical design of a thermal imager working on the platforms which are lighter (zeppelin, balloon, etc.) or heavier (unmanned aerial vehicles, etc) than air in the high altitude. People are informed about conceptional principles and infrared sources, atmospheric tranmissivity, dedector which will limit the optical system and optical materials which can be used in the infrared region are analyzed before this optical design. The design of optical camera which is a kind of Cassegrian is performed by being used Zemax optical design software. The optical performance analysis of the design is also discussed.

HO:YAG laser design and it's application for kidney stone fragmentation

MSc / 2016

Autor: MUHAMMAD IRFAN
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 436225

Holmium laser has a number of applications in medical field such as fragmentation of Kidney and Gladder stones. Wavelength of Holmium laser is 2.1µm which has significant absorption coefficient and low penetration depth in water that is why the use of this laser is inevitable for a lot medical applications. All those similar applications demand high energy laser pulses at low repetition rates. In this study, 20W Ho:YAG laser system was designed and implemented. The Ho:YAG laser system mainly comprised of Power supply, Laser design and cooling system. User friendly power driver was designed and implemented which was capable to driver laser system between 1-20Hz and variable pulse duration between 0.2-3ms. Parallel triggering technique integrated with simmer circuit was applied for best operation of flash lamp. Flash lamp driver was customized for 625 and 880V DC voltage levels. Ho:YAG laser resonator was designed and implemented. This laser was operated at different repetition rates up to 20Hz. Optimum operation was achieved at 5 and 10Hz with laser energy of 2J per pulse which is sufficient to break the Kidney stones. Laser power of 20W was measured at 10Hz repetition rate. Laser pulse duration is completely dependent upon flash lamp current pulse, so variable laser pulse duration was observed at variable flash lamp current pulse durations. Nevertheless cooling of gain media also plays a major rule in the efficiency of the laser. Although this laser may work at room temperature that demand can be fulfilled by water-air cooling unit. However, to run the laser system at desired conditions water-water cooling unit was designed which has capacity to remove 2kW heat per second from laser cavity. The major purpose of the developed of this laser was to use for lithotripsy (Kidney stones fragmentation). Experimental setup along with laser beam delivery system was designed to break kidney stones in water. Stone fragmentation is mainly photo thermal and involves a thermal drilling process rather than shock wave. Free running laser resonator in the presence of Pockel cell inside laser cavity was also implemented successfully. Finally, all the phases of the Holmium laser was designed and implemented successfully. Laser power of 20W at 10Hz repetition rate achieved. Offline, Kidney stone fragmentation experiment was designed and fragmentation was observed.

Analysis of optical and mechanical properties of colored surfaces produced by laser on titanium materials

MSc / 2016

Autor: ECEM ÇERKEZOĞLU
Supervisor: Dr. Öğr. Üyesi ERHAN AKMAN
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 436226

Laser marking of metals is a common application which is used for identification of products in industry. Unlike printing, emulsion coating and electrochemical processes, laser marking yields advantages such as increased repeatability, non-contact operation and fast processing. Studies on metals such as titanium, vanadium and copper leads to coloured surfaces formation with the effect of oxide layer generation on the surface while marking by laser. Different coloured surfaces can be optained via controlling parameters such as oxide layer thickness, refractive index and etc. Controlling heat energy that is transferred to the material which is impossible by any other method, renders the laser very useful in color marking applications. In this thesis study short-pulse (nanosecond) fiber laser is utilized to obtain different coloured surfaces on Titanium Grade 2 by changing the scanning speed. Optical properties of subject colours are determined via reflection spectra. Compositional content of oxide layers which are generated on surfaces are analysed by XPS and XRD. Additionally micro scratch tests are performed in order to determine the effect of micro scratches to the marked surfaces.

The development of Raman spectroscopy and its environmental applications

MSc / 2015

Autor: ARZU ALTINPINAR
Supervisor: Prof. Dr. ELİF KAÇAR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 423768

Raman spectroscopy is a molecular spectroscopic technique based on scattering of light and used to the analysis of solid, liquid or gases samples. Surface Enhanced Raman Spectroscopy (SERS) is kind of Raman spectroscopy developed using metal nanoparticles to enhance the Raman spectrum intensity. In this study, the analyses of the sea water and a chemical compound Sudan III samples were performed using the SERS technique. The gold (Au) nanoparticles used in the experiments were produced by laser ablation technique and availability of nanoparticles produced by this technique was examined in SERS experiments. The changes of intensities in the Raman spectra of the sea water were examined with developed SERS technique. The analyses on same samples with infrared spectroscopy (IR) which supports the Raman spectroscopy were performed and comparative results were evaluated. Chemical organic compound Sudan III sample is used as colorant in different industries and result of mixing to the nature, lead to serious environmental problems. The applications of the SERS in the both powdered and the solution forms of the environmentally important Sudan III molecule were carried out and analysis of the results obtained were performed. Also, sediment samples taken from the sea floor of the Gulf were evaluated by Raman spectroscopy and laser induced breakdown spectroscopy (LIBS) as environmental.

Implant surface modification by laser

MSc / 2014

Autor: TUBA İKİER
Supervisor: Assoc. Prof. ELİF KAÇAR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 354570

Change the surface topography of implant materials, plays an important role in cell-implant interactions. In this thesis, the surface of the titanium plates and the Al2O3-coated glass slides which have potential to can used as the implant materials were structured by laser. Firstly, the surface of the Al2O3 coated glass slides was structured as spots in matrix form using Ti-Sapphire laser and Nd-YAG laser. By evaluating of the analysis results of the obtained surfaces, the laser structured surface which has the desired nano-and micro-structures as well as undamaged coating was chosen. This surfaces were structured using two different methods. HUVEC (Human Umbilical Vein Endothelial Cell) cells were seeded on these surfaces and their behaviours were examined. Secondly, periodic surface structure were produced by two-beam interference method developed using Michelson interference system and wavelength of the 532 nm laser. Period of these fringes produced on Al/Al2O3 bi-phasic materials can be easily controlled. HUVEC cells were seeded onto the structures having different grating periods, and behaviour of these cells were examined. HUVEC cells adheres more well on the surfaces containing periodic structures according to the untreated surfaces. With the same method, on titanium surfaces were also formed periodical structures.

Keywords: Cells - Implant Material Interaction Two-Beam Interference Technique Laser Surface Treatment Periodic Surface Structures

Analysis of archaeological samples by LIBS

MSc / 2014

Autor: MESADET ASUMAN SINMAZ
Supervisor: Dr. Öğr. Üyesi BELGİN GENÇ ÖZTOPRAK
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Subject: Arkeometri = Archaeometry ; Lazer spektroskopisi = Laser spectroscopy
Thesis No: 372704

Laser induced breakdown spectroscopy (LIBS) is preferred technique in the analysis of archaeological samples. In this study, analyses of thin film and archaeological samples were carried out by using BAKİ-LIBS system as a domestic producted at Kocaeli University Teknopark company BEAM R&D. Multilayer CZTS thin films which produced on glass substrate by magnetic sputtering technique is selected as samples and their analyzes were performed by LIBS. Elements change were evaluated according to depth using the single shot LIBS measurements taken from the thin film surface. Analyses of glaze, paint and clay of archaeological ceramics which are considered as cultural heritage have been carried out using LIBS and the results presented. In the analysis of glaze, the creamics belong to the Islamic and Byzantine cultures and similarities and differences structure of their glaze were presented. In the analysis of paint, results of spectrochemical analysis according to the paint were presented by the results of LIBS measurement taken from green and brown paint layers in surface of ceramics. In the analyses of clay, form differences of ceramics were presented and then classification of the ceramics was performed by chemometric methods (PCA and PLS-DA) as an empirically defined in the structure of different clay; frit, calcerous frit and red soil.

Numerical and experimental investigation of nanosecond laser beam interaction with metal materials

PhD / 2014

Autor: PINAR DEMİR
Supervisor: Assoc. Prof. ELİF KAÇAR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 360871

Lasers are used in many applications based on laser ablation in several areas such as industry, medical area through the technological advances. Detailed investigations of laser heating, melting and vaporization processes occurred during laser-material interaction are necessary to control and develop these applications. In the scope of this thesis, thermal processes occurred during laser ablation were studied numerically and experimentally for several applications based on interaction of laser with material. In the thesis study, a mathematical model was considered to numerically investigate laser heating, melting and vaporization processes occurred in the interaction of laser beam with solid material during irradiating a metal surface by nanosecond laser beam with Gaussian intensity distribution. Using the considered mathematical model, calculations were performed for different applications to get an insight to the thermal mechanisms taking place in the laser ablation process. It was concluded that experimental and numerical results provide an insight for investigation of heat conduction for laser ablation process, and give an estimation for material removal caused by surface vaporization.

Keywords: Heat Conduction Laser Ablation Laser Interaction with Material Mathematical Modeling

Development of mobile optical frequency comb synthesizer system locked to Cs atomic clock

MSc / 2013

Autor: OĞUZHAN KARA
Supervisor: Assoc. Prof. ÖZCAN GÜNDOĞDU
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Bilim ve Teknoloji = Science and Technology ; Elektrik ve Elektronik Mühendisliği = Electrical and Electronics Engineering ; Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 342551

In this thesis work, a 33 fs Yb-doped optical frequency comb with central wavelength of 1050 nm and that covers the spectral range of 600-1600 nm has been generated and stabilized to 10 MHz output of a Cs atomic clock. All-normal-dispersion (ANDi), dispersion-managed, similariton and spectrally-breathing lasers have been built to be used as the optical oscillator of the Yb-doped frequency comb and their pulse durations, spectra, relative intensity noise and phase noise have been characterized. Amplified laser pulses are compressed using diffraction gratings and coupled into photonic crystal fiber (PCF), which produces supercontinuum (SC) that covers the range of 600-1750 nm. The factors that affects the spectral bandwidth of SC (central wavelength,duration and polarization of pulses, type and length of PCF, etc.) have been investigated experimentally and compared to simulation results. The coherence properties of the generated supercontinuum have been investigated using the obtained carrier-envelope-offset beat signal and the beat signal between SC and a stabilized Nd:YAG laser.

Keywords: Femtosecond comb frequency stabilization absolute optical frequency measurement optical frequency generation Yb fiber laser

Laser stimulated raman spectrometer design and medical applications

MSc / 2013

Autor: MURAT GÜNEŞ
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Electro-optical System Engineering
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 342550

In this study, performing of Raman spectroscopy with two different 532 nm and 785 nm wavelength laser sources and medical applications are aimed. After the optical design of Raman spectrometer has completed, the wavelength separated light, that scattered from the sample, has been caught with CCD detector and processed with the software. The software has a completely Turkish interface and written with C# programming language. Raman spectrometer, as opposed to other spectrometers, because the scattered light is so weak to capture with the CCD detector and hard to seperate from the noise the CCD detector should be cooled in a controlled manner, and it must be kept cold during measurement. For this purpose a temperature controller designed and implemented with TEC (Thermo Electric Cooling) and a microcontroller. SolidWorks software is used for modelling the mechanical parts of the system and after that mechanical parts have been produced.

Design of the laser-induced breakdown spectroscopy system, industrial and biological applications

PhD / 2012

Autor: BELGİN GENÇ ÖZTOPRAK
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Subject: Analitik analiz = Analytical analysis ; Bakır alaşımları = Copper alloys ; Böbrek taşları = Kidney calculi ; Sınıflandırma = Classification
Thesis No: 323161

Laser Induced Breakdown Spectroscopy (LIBS) provides a spectral measure of elemental composition in industrial and biological materials. BAKİ-LIBS system with a high resolution multichannel spectrometer and spectral analysis software was developed at Laser Technologies Research and Application Center (LATARUM), Kocaeli University. This thesis reports an interesting industrial application of LIBS in order to determine the elemental composition and diffusion of Stellite 6 powder evaluating quality of the laser welding of copper plates. The elements in laser weld joints of copper plates were analysed with BAKİ-LIBS, utilizing a high resolution multi-channel CCD spectrometer and a nanosecond pulse Nd:YAG laser, providing a depth profile of elemental composition of the penetrated region. As a biological application, various types of kidney stones were analysed with BAKİ-LIBS and classified by using element ratio, Principal Component Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA) methods. Heterogeneous kidney stones were analyzed by LIBS emission lines; charateristic of elements present in different types of kidney stones, taken at different locations on the stones, producing elemental mapping. The classification of the stones were conducted using the spectral line intensity ratios of C, H, Ca, Mg and P elements. It was found that the ratio of hydrogen (H) to carbon (C) was an important indicator of organic compounds such as uric acid. Also, PCA and PLS-DA of broadband LIBS spectra were employed for classifying different types of kidney stones. The hardness of the kidney stones was measured with traditional Vickers hardness test and was computed in good correlation from LIBS spectral line intensity ratio of MgII lines to MgI line.

Keywords: Depth Analyis LIBS Material Analysis Hardness Test Classification

Femtosaniye lazerle metalik nanoyapıların oluşturulması ve biyolojik uygulamaları

PhD / 2012

Autor: ERHAN AKMAN
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering ; Makine Mühendisliği = Mechanical Engineering
Subject: Biyomalzemeler = Biomaterials ; Biyoteknoloji = Biotechnology ; Lazerler = Lasers ; Nano yapı = Nano structure ; Nanopartiküller = Nanoparticles
Thesis No: 323163

It is known that the interaction between laser and material causes permanent changes which cannot be obtained through other instruments in material characteristics. There has been much concern recently in micro/nano processing with laser as a result of development of Ti:Sapphire lasers with ultra short pulse length (femtosecond). Lately, obtainment of functional surfaces through micro and nano structures which are formed on material surfaces using lasers and biological applications of these surfaces are among top research subjects. Production of biomaterials which are effected on cellular behaviour of cells is the primary aim to achieve this goal. Another important research area of the laser ablation process is the production of nanoparticles from metal targets because of potential applications of it in new materials, biomedical sciences, electronics, optics, magnetism, energy storage and electrochemistry fields. New properties of materials are tried to be obtained through nano-sized studies. The main objective of this study is the investigation and use in applications of physical and chemical properties which change when the materials are reduced to the nano scales.

In this study, micro and nano sized material processing was carried out using femtosecond pulse length laser. Hydrophobic property of 316L stainless steel surfaces was increased with the laser treatment. The adhesion and the enlargement of the bone stem cell was developed creating micro and nano structure on the stainless steel surface which can be used as an implantation material. Production and characterization processes of gold and silver nanoparticles using ultrashort laser in liquid environment which are applicable in bio-sensing and imagining due to their sharp and clear optic properties in visible region were performed. The sizes of nanoparticles were decreased applying the laser beam for the second time in different wavelengths to the gold and silver nanoparticles which are relatively produced bigger form the metal target.

Keywords: Bio-materials Laser surface processing Laser produced nanoparticle Metallic nanoparticles Surface plasmon resonance

Coating of the metalic powders to metalic surface using milisecond pulsed laser

MSc / 2010

Autor: SERDAR BABUR
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Fen Bilimleri Enstitüsü / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 275782

Cobalt-based Stellite powders have shown a high resistance against wear and corrosion and due to this the automotive, turbine and aerospace industries prefer this alloy is a kind of common. Industrial metal machine parts are exposed to high temperature and water droplets are regularly. Laser cladding techniques, compared to other hard facing techniques, have superior properties in terms of pureness, homogeneity, hardness, bonding and microstructure. The mixing between the clad layer and substrate materials must be as small as possible to utilise the properties of the coating material effectively and to achieve good quality clad layers. Modern Nd:YAG lasers have the ability to shape the temporal profile of each pulse at repetition rates of up to several kHz. This property gives control of thermal input in the material. Pulse energy, pulse frequency, overlap, powder mass flow rate and dilution are the main parameters that have influences on the cladding quality.

In this thesis, laser cladding experiments were carried out using Lumonics JK760 Nd:YAG pulsed laser. Cladding was accomplished by delivering the Stellite 6 powder homogeneously through a powder feeder (model: Sulzer Metco). Cladding parameters were determined by obtained experiments with using Stellite 6 powder alloy and the pulsed laser. It was found that dilution was the most important parameter that affectived the quality of clad layer. The lowest dilution was obtained the value (9.1 %) at an incident energy of 12 J/pulse, pulse frequency of 25 Hz and spot overlap of 80 %.

Design of a laser scanning confocal microscope to investigate the cells which are interacted with diode lasers

MSc / 2009

Autor: ÇAĞRI KAAN AKKAN
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Fen Bilimleri Enstitüsü / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Subject: Biyoloji = Biology ; Hücreler = Cells ; Lazerler = Lasers ; Mikroskop = Microscope
Thesis No: 259472

Lasers are light sources with large usage area. They are serving to many application like from industry to medical. Another usage area of lasers is microscopes which are using in many applications in biology and medical. And Laser Scanning Confocal Microscopes are the devices which are using lasers as a light source. Scientist prefers lasers as a Light source in microscopy because of their monochromatic and same frequency light.

In this master thesis, a laser scanning confocal microscope design introduced which is designed for investigate the affects of diode lasers on cells and showing the topography of rigid surfaces at Laser Technologies Research and Application Center.

Carbon-fibre reinforced compozites and determination of laser parameters for holes on polycarbonate materials

MSc / 2008

Autor: LEVENT CANDAN
Supervisor: Dr. Öğr. Üyesi TİMUR CANEL
Institution: Kocaeli University / Fen Bilimleri Enstitüsü / Fizik Bölümü / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 232756

Everyday new polymers are being added to thousands of polymer produced by new polymerization technique. Polymers are necessary part of daily life practically at all area. High quality holes are important in electronic and medical industry. Lasers are preferred in drilling, cutting, welding because its high process speed, low thermal deformation, high aspect ratio. Application area of lasers are growing with laser system developed with progressive technology. Flexibility of laser parameters (pulse duration, wavelength, pulse energy) made enable to develop quality of machining. Drilling process of ceramics, silicon and polymer layers with laser are used in electronic industry. Laser can drill smaller and more precise hole than that of conventional technique.

In this thesis study, laser parameters of drilling of carbon fibre reinforced polymer composites laser and microdrilling of polycarbonate material by Nd:YAG are investigated.

Keywords: Micromachining of materials with laser Nd:YAG laser application in industry drilling by laser machining of polymeric materials

Design and produced of spectrometers and imaging systems to record x-rays and visible spectral emission

MSc / 2006

Autor: BELGİN GENÇ
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Fen Bilimleri Enstitüsü
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 197205

Specrtometers are used for analyse of solid, liquid, gas and plasma materials. X-rays can be produced using laser produced plasmas. Crystal spectrometers are used to resolve x-rays emitted from plasmas. Visible spectrometers are used to examine visible rays emitted from different media.

In this thesis, spectrometers and imaging systems were designed and produced to record x-rays and visible spectral emission. These are visible spectrometer, x-ray spectrometer, pinhole camera, cross slit camera. Detailed design parameters of these systems and producing stages of these systems were introduced. Calibration of the enhanced spectrometers and imaging systems were made. Recorded spectrum during the laser maching experiments were introduced. Calculated spectrum helping design of spectrum were introduced.

Keywords: Spectrometer electromagnetic spectrum laser produced plasma

Hydrodynamic modelling of laser produced plasma media

MSc / 2006

Autor: PINAR DEMİR
Supervisor: Dr. Öğr. Üyesi ELİF KAÇAR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering
Thesis No: 197929

Laser produced plasmas are used as active medium for producing X-ray laser. Plasma parameters such as electron density, electron temperature, and radiations emitting from this plasmas are investigated experimentally and theoretically.

In this thesis, Ne-like Fe plasma medium produced by irradiating iron target with driving laser composed of two pulses is investigated theoretically. EHYBRID code is used for modelling. Variations of general plasma parameters such as electron density, electron temperature by driving laser configuration are investigated. In the simulation, variations of plasma parameters by pre-pulse duration, pre-pulse intensity and delay time are calculated. The driving laser parameters affect and determine the plasma properties and x-ray laser active medium.

Ni-like Sn and Ni-like Mo x-ray laser gain media produced using recently developed grazing incidence pumping method are simulated using EHYBRID code and a post- processor code. In the simulations, it is assumed that a pre-plasma is produced by irradiating Tin and Molibdenum targets with a pre-pulse in the direction of target normal and then laser gain medium is produced by irradiating the targets with a main-pulse with a grazing incidence angle. Ni-like Sn and Ni-like Mo x-ray laser gain madia are modelled for driving laser configuration parameters. Optimum driving laser configuration and plasma conditions for producing x-ray laser are determined.

Keywords: Hydrodynamic Modelling Laser Produced Plasmas X-Ray Lasers

Welding of Ti6Al4V titanium alloys with pulsed Nd:YAG laser and determining of welding parameters

MSc / 2006

Autor: ERHAN AKMAN
Supervisor: Prof. Dr. ARİF DEMİR
Institution: Kocaeli University / Institute of Natural and Applied Sciences / Physics
Discipline: Fizik ve Fizik Mühendisliği = Physics and Physics Engineering ; Makine Mühendisliği = Mechanical Engineering
Thesis No: 197940

Because of the light weight and excellent corrosion resistance of the titanium alloys are the most advantageous materials for the automotive and aerospace industry. In order to achieve reliable welds with minimal distortion for fabrication components for industry several techniques were investigated. Laser welding is the most important joining technique because of its desired features. Modern Nd:YAG lasers have the ability to shape the temporal profile of each pulse at repetition rates of up to several kHz. This flexibility gives control of thermal input with a precision not previously available. For pulsed laser welding, pulse shape, pulse energy, pulse duration, pulse repetition rate and peak power are the main parameters that have influences the weld quality. The combinations of this parameters are very important for pulsed laser seam-welding.

In this study, the Lumonics JK760 Nd:YAG pulsed laser was used, an experimental work have been done to determinate pulsed laser seam-welding parameters for titanium alloy. The rate between the pulse energy and the pulse duration is main factor which is effective while determining the penetration dept. Therefore we determined initially pulse duration and the pulse energy, to obtain desired weld quality the pulse shape was constituted. And also we considered the repetition rate to determine the welding speed.

Keywords: , Laser material processing Pulsed Nd:YAG laser applications in industry. Laser Welding Titanium alloys

Electro-Optics

  • Measurement of laser parameters
  • Spectroscopic investigations.
  • Determination of optical properties.

Laser Material Processing

  • Laser welding of industrial and advanced materials.
  • Laser surface modifications of the materials.
  • Laser assisted material alloying.
  • Laser machining and micromachining of the materials.

Modelling and Simulation

  • Modelling of the laser produced plasmas.
  • Designs of the spectrometers.
  • Modelling of optical properties of thin films.

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