The aim of my thesis is the analysis of properties of laser cladding. The theoretical part is focus on conventional methods of laser cladding, types and properties of lasers and its applications in industry. Then there is the description of preparing metallographic samples and its assessment, also there are types of wear enclosed. In the experimental part the nickel laser cladding were made by using semiconductor laser, in which the structure, the dilution, the EDS analysis and the hardness with respect to input parameters are assessed.

No description available.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed December 6, 2007) Includes bibliographical references.

In laser cladding, a material, usually in the form of powder, is deposited on a substrate. Powder particles are intermingled with inert gas and fed by a powder feeder system on the substrate. Laser is employed to melt the additive material and a small layer of surface of the substrate simultaneously. While the powder is being deposited, the laser melts the powder particles and the melted powder particles join the melt pool on the substrate beneath the laser beam. Generating relative motion between the laser focal point and the substrate will result in moving melt pool on the substrate. This will lead to addition of a desired material to the substrate with desired thickness and good bonding as well as minimum dilution. In addition, by producing clads beside and on the top of each other a functional component can be built in a layer by layer fashion. Despite many advantages of laser cladding, it is highly sensitive to internal and external disturbances. This makes a closed-loop control system for laser cladding inevitable. Utilizing a closed-loop control system in laser cladding makes the system insensitive to external and internal disturbances. Having a closed-loop control system for laser cladding would contribute to substantial improvement in clad quality and cost reduction. Feedback sensor is an essential part in a closed-loop control system. Among different parameters that can be used as feedback signals in a closed-loop control of laser cladding, melt pool geometry and in particular clad height is of great importance specifically for the purpose of rapid prototyping. This thesis presents novel algorithms for real-time detection of clad height in laser cladding. This is accomplished by the following: Tackling the issues pertinent to image acquisition in the presence of harsh and intensive light is scrutinized. Important parameters of digital cameras related to selection of proper type of CCD cameras in order to overcome the existent harsh condition are presented. Also, the existent light in laser cladding arisen from different sources is analyzed and based upon that proper bandpass filters and neutral filters are selected. All these lead to capture relatively sharp and clear images of the melt pool. Capturing good quality pictures potentially would provide valuable information about the process. This information could include, but is not limited to, melt pool geometry (i.e., melt pool height, width, melt pool profile, and wet angle), angle of solidification, melt pool temperature, and melt pool temperature distribution. Furthermore, the issues regarding path dependency of the melt pool image are addressed by using a trinocular cameras configuration. By utilizing this, always two cameras monitor the front end of the melt pool regardless of the direction of the clad. Image analysis of the grabbed images is also discussed. Image thresholding is one of the most formidable tasks in image processing and this difficulty is intensified due to characteristics of the grabbed images of the melt pool (e.g., surrounding hazy area around the melt pool). Applying hard partitioning thresholding method did not lead to detec- tion of the melt pool accurately. As a result, fuzzy thresholding by minimizing of the measure of fuzziness is developed and its performance is investigated. The effect of three important membership functions, triangular, Gaussian, and generalized Bell on the performance of the thresholding method is investigated. Also, Image thresholding by utilizing fuzzy c-means clustering is developed. Applying the developed thresholding methods show promising results. Among the developed thresholding methods, fuzzy thresholding with minimizing the measure of fuzziness with Gaussian membership function is selected for the implementation in the algorithm. Finally, Image feature tracking module is presented. The detected borders of the melt pool images are transformed from image plane to the world plane by using a perspective transformation. Four features of the elliptical features of the projected melt pool borders are selected. These four features along with the angle of tangential path vector with respect to the corresponding right hand side camera's axis are fed into an Elman recurrent neural network. The proposed algorithms and the trained neural network are utilized in the process resulting in acceptable detection of the clad height in deposition of straight clads for a specific direction. It is concluded that the system can detect the clad height with about ±0.15 mm maximum error.

In laser cladding, a material, usually in the form of powder, is deposited on a substrate. Powder particles are intermingled with inert gas and fed by a powder feeder system on the substrate. Laser is employed to melt the additive material and a small layer of surface of the substrate simultaneously. While the powder is being deposited, the laser melts the powder particles and the melted powder particles join the melt pool on the substrate beneath the laser beam. Generating relative motion between the laser focal point and the substrate will result in moving melt pool on the substrate. This will lead to addition of a desired material to the substrate with desired thickness and good bonding as well as minimum dilution. In addition, by producing clads beside and on the top of each other a functional component can be built in a layer by layer fashion. Despite many advantages of laser cladding, it is highly sensitive to internal and external disturbances. This makes a closed-loop control system for laser cladding inevitable. Utilizing a closed-loop control system in laser cladding makes the system insensitive to external and internal disturbances. Having a closed-loop control system for laser cladding would contribute to substantial improvement in clad quality and cost reduction. Feedback sensor is an essential part in a closed-loop control system. Among different parameters that can be used as feedback signals in a closed-loop control of laser cladding, melt pool geometry and in particular clad height is of great importance specifically for the purpose of rapid prototyping. This thesis presents novel algorithms for real-time detection of clad height in laser cladding. This is accomplished by the following: Tackling the issues pertinent to image acquisition in the presence of harsh and intensive light is scrutinized. Important parameters of digital cameras related to selection of proper type of CCD cameras in order to overcome the existent harsh condition are presented. Also, the existent light in laser cladding arisen from different sources is analyzed and based upon that proper bandpass filters and neutral filters are selected. All these lead to capture relatively sharp and clear images of the melt pool. Capturing good quality pictures potentially would provide valuable information about the process. This information could include, but is not limited to, melt pool geometry (i.e., melt pool height, width, melt pool profile, and wet angle), angle of solidification, melt pool temperature, and melt pool temperature distribution. Furthermore, the issues regarding path dependency of the melt pool image are addressed by using a trinocular cameras configuration. By utilizing this, always two cameras monitor the front end of the melt pool regardless of the direction of the clad. Image analysis of the grabbed images is also discussed. Image thresholding is one of the most formidable tasks in image processing and this difficulty is intensified due to characteristics of the grabbed images of the melt pool (e.g., surrounding hazy area around the melt pool). Applying hard partitioning thresholding method did not lead to detec- tion of the melt pool accurately. As a result, fuzzy thresholding by minimizing of the measure of fuzziness is developed and its performance is investigated. The effect of three important membership functions, triangular, Gaussian, and generalized Bell on the performance of the thresholding method is investigated. Also, Image thresholding by utilizing fuzzy c-means clustering is developed. Applying the developed thresholding methods show promising results. Among the developed thresholding methods, fuzzy thresholding with minimizing the measure of fuzziness with Gaussian membership function is selected for the implementation in the algorithm. Finally, Image feature tracking module is presented. The detected borders of the melt pool images are transformed from image plane to the world plane by using a perspective transformation. Four features of the elliptical features of the projected melt pool borders are selected. These four features along with the angle of tangential path vector with respect to the corresponding right hand side camera's axis are fed into an Elman recurrent neural network. The proposed algorithms and the trained neural network are utilized in the process resulting in acceptable detection of the clad height in deposition of straight clads for a specific direction. It is concluded that the system can detect the clad height with about ±0.15 mm maximum error.

The experiments performed for this thesis were designed to define the primary process variables of time, temperature, and atmosphere for an engineering system that will produce metal powder from recycled nuclear fuel cladding. The proposed system will hydride and mill Zircaloy cladding tubes to produce fine hydride powder and then dehydride the powder to produce metal; this thesis is focused on the hydride formation reaction. These experiments were performed by hydriding nuclear grade Zircaloy-4 tubes under flowing argon-5% hydrogen for various times and temperatures. The result of these experiments is a correlation which relates the rate of zirconium hydride formation to the process temperature. This correlation may now be used to design a method to efficiently produce zirconium hydride powder. It was observed that it is much more effective to hydride the Zircaloy-4 tubes at temperatures below the a-B-d eutectoid temperature of 540°C. These samples tended to readily disassemble during the hydride formation reaction and were easily ground to powder. Hydrogen pickup was faster above this temperature but the samples were generally tougher and it was difficult to pulverize them into powder.

Thesis (M.S.C.E.)--University of Massachusetts Amherst, 2009. / Open access. Includes bibliographical references (p. 87-89).

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003. / Word processed copy. Summary in English. Includes bibliographical references (leaves 99-105). Also available online.

This research investigates the interaction between heavy precast cladding units attached to steel framed buildings. Cladding systems are designed as non-structural components and are not expected to contribute to the energy absorption of the primary structure. However, research has indicated that the cladding system may be designed to reduce the response of the primary structure under seismic excitations. The use of flexible connections between the cladding and primary structural frames may be able to provide beneficial effects to the entire structural response. In this study, a series of earthquake engineering simulations were conducted in OPENSEES to analyze the effects of the flexible connections of the cladding on both a 3 story and 9 story prototype structures. The research focus is on the 3 story structure. The results from 3 story and 9 story structures indicate that the flexible cladding connections have the ability to transfer hysteretic energy from the primary structure to the flexible cladding connections.

Thesis (MscEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Low-rise buildings with crest fastenedmetal cladding are susceptible to failures in the vicinity of the fasteners during strongwind uplift conditions. These localised failures often lead to the progressive removal of cladding, which can cause disastrous building damage. In South Africa, the current metal cladding design approach is inadequate, since it solely relies upon manufacturer design specifications. These specifications are typically designated as broad design guidelines for the maximum allowable cladding support spacings which are independent from any specified design loads. This research focuses on the investigation of 0.50 mm ISQ550 IBR cladding systems to understand basic cladding behaviour during static wind uplift conditions and to quantify the uplift performance of IBR systems. The research investigation also included the improvement and performance evaluation of a full-scale cladding test method which applies an air-bag loading method to simulate static wind uplift conditions according to the revised SANS 10237:201X code of practice. This thesis may serve as a basis for further cladding research, and the development of suitable standardised metal cladding test methods in South Africa. Several experimental investigation methods and limited finite element analyses (FEA) were used to investigate IBR and the performance of the test methods. Tensile testing was used to determine the material properties of the cladding metal. The full-scale cladding assembly testing was used to investigate the behaviour of IBR and to evaluate the performance of the air-bag test rig. The localised behaviour of the cladding around the fasteners was also investigated with a small cladding subassembly test method. The FEA served as a supplementary investigation for IBR performance evaluation. The experimental investigation confirmed that the static wind uplift resistances of IBR systems are mainly governed by localised deformations of their fastened crests and fastener pull-through failures. The behaviour and performance of IBR systems are heavily dependent on the crest fastening arrangement. IBR systems with every crest fastening demonstrated a considerably higher wind uplift resistance than IBR systems with the standard alternate crest fastening arrangement. The measured fastener loads were independent from span length, whereas the overall uplift resistance of IBR reduced with increased span lengths. Load-span resistance data for 0.50 mm ISQ550 IBR was derived from testing to provide a rational framework for design. The FEA provided a reasonable simulation of IBR subjected to static wind uplift and confirmed the presence of high stress and strain concentrations around the fastener holes which cause fastener pull-through failures. Therefore, FEA can be used as an effective tool to investigate the behaviour of IBR. In conclusion, the air-bag test method used in this research investigation provided an effective method for evaluating the uplift performance of crest fastened metal cladding. However, the air-bag load method is not capable of accurately simulating a true uniformly distributed uplift load. It is recommended that direct air pressure testing be adopted for any further research or commercial testing ofmetal cladding because direct air pressure testing is an effective and proven test method for accurate simulation of static and cyclic wind uplift conditions. / AFRIKAANSE OPSOMMING: Metaalbekleding met kruinvashegting op lae geboue is geneig om te faal by die vashegters tydens toestande van sterkwind-opheffing. As vashegters faal kan bekleding progressief verwyderwordomrampspoedige skade aan die gebou te veroorsaak. Die huidige ontwerpmetode vir metaalbekleding in Suid-Afrika is onvoldoende, aangesien dit slegs gegrond is op vervaardigers se ontwerpspesifikasies. Spesifikasies word gewoonlik verklaar as breë ontwerpriglyne vir die maksimum toelaatbare spasiërings van ondersteunings sonder enige oorwegings vir ontwerpbelastings. Hierdie navorsing fokus dus op 0.50mm ISQ550 IBR metaalbekleding omdie basiese gedrag van bekleding tydens wind-opheffing beter te verstaan en die ophefweerstand van IBR te kwantifiseer vir ontwerpdoeleindes. Verder ondersoek hierdie navorsing ook die verbetering en evaluasie van ’n volskaalse bekledingstoetsmetode wat statiese wind-opheffing naboots met verspreide lugsakbelasting volgens die hersiende SANS 10237:201X gebruikskode. Hierdie proefskrif kan dien as ’n grondslag vir verdere navorsing en die ontwikkeling van geskikte standaard-toetsmetodes vir metaalbekleding in Suid-Afrika. Verskeie eksperimentele toetsmetodes en beperkte eindige-element-analises (EEA) is gebruik om die gedrag van IBR en die toets-opstellings te ondersoek. Trektoetse is gebruik om die meganiese eienskappe van die bekledingsmetaal te bepaal. Volskaalse toets-opstellings is gebruik om die weerstand van IBR te ondersoek en die lugsaktoetsmetode te evalueer. Die gelokaliseerde gedrag van die bekleding rondom die vashegters was ook ondersoek met klein toets-opstellings. EEA het gedien as ’n aanvullende ondersoek om die gedrag van IBR te evalueer. Die eksperimentele ondersoek het bevestig dat die wind-ophefweerstande van IBR-stelsels hoofsaaklik bepaal word deur gelokaliseerde deformasies van die vasgehegde kruine en die vashegters se deurtrekweerstand. Die gedrag en weerstand van IBR-stelsels is ook grootliks afhanklik van die toegepaste vashegtingsmetode. IBR stelsels met vashegting deur elke kruin het ’n hoër ophefweerstand verskaf as IBR-stelsels met die standaard vashegtingsmetode deur elke tweede kruin. Die gemete vashegterbelastings was onafhanklik van die spanlengtes, terwyl die algehele ophefweerstand van IBR verminder het vir langer spanlengtes. Toetsdata is gebruik om ophefweerstande vir 0.50mm ISQ550 IBR oor verskeie spanlengtes af te lei sodat ’n rasionele raamwerk vir ontwerp bewerkstellig kan word. Die EEA het die gedrag van IBR tydens toestande van statiese wind-opheffing redelik goed nageboots en het ook die teenwoordigheid van hoë spannings- en vervormingskonsentrasies rondom die vashegtergate, wat vashegters laat deurtrek, bevestig. Daarom kan EEA as ’n effektiewe instrument gebruik word om die gedrag van IBR te ondersoek. Ten slotte word dit afgelei dat die lugsaktoetsmetode van hierdie navorsingsondersoek ’n effektiewe metode verskaf het vir die gedrag-evaluering van kruinvasgehegte bekleding tydens wind-opheffing. Die lugsaktoetsmetode kan egter nie ’n ware gelykverspreide ophefbelasting naboots nie. Daarom word dit voorgestel dat toetsmetodes wat direkte lugdruk aanwend gebruik moet word vir enige verdere navorsing of kommersiële toetse van metaalbekleding, aangesien dit ’n effektiewe en bevestigde toetsmetode is wat statiese en sikliese opheftoestande akkuraat kan naboots.