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On the physics of laser cladding and its context to production
2006 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The thesis treats both fundamental physical mechanisms of a materials processing technique, namely laser cladding, and its introduction to a certain product, namely piston rings, in production. In particular it is demonstrated that even very fundamental physical mechanisms discovered can have important impact on several production stages. After discussing three physical mechanisms of the laser cladding process, and after discussing possible scenarios for introducing laser cladding to production, this context will be illustrated and discussed. The three physical mechanisms investigated are based on earlier research work that was developed further, by applying new methods and approaches. Absorption as the essential conversion mechanism from highly expensive high power laser beam power to heat is studied for preplaced powder laser cladding, where a fundamental experiment enables facilitated theoretical estimation of the absorptance, that turns out to decrease with increasing pulse energy and to range typically between 25% and 10%. The temperature field resulting from the combined heat flow through the clad layer and the substrate of a second different material is studied by deriving an analytical equation for this complex case, again in a simplified manner. The induced changes in the temperature gradient are discussed for four substrate materials and two clad layer materials as well as for three different clad layer thicknesses. Steeper gradients are induced in the clad than in the substrate. Moreover, the lowered thermal conductivity of a preplaced powder layer is studied through a parametric study by accomplishing a simplified model, showing its insulating behaviour. The third mechanism studied is the stress and strain formation in laser cladding. For former Finite Element Analysis a method for additional investigation and illustration was developed, facilitating the understanding of the complex mechanisms behind. A series of evident and hypothetical theories can be stated and discussed in a more rational manner than before. For example the strong transversal tensile stresses can either cause clad layer detachment or longitudinal edge cracking. Beside these three physical mechanisms of laser cladding, the implementation of laser cladding to production is discussed, comparing the alternative possibilities of direct investment into a laser cladding system for the manufacturing line or by outsourcing this step to a laser cladding job shop. A series of other production steps as well as the product development are affected by introducing such new technology. Eventually the context between the above three physical studies and the production is discussed by demonstrating how a better understanding of the process physics can have an impact on different production steps from a holistic view. Showing the context through such holistic and interdisciplinary treatment is a new approach with the aim to enhance the understanding that treating engineering steps in a partially holistic manner rather than separately can be of importance for the whole product development and production, as demonstrated for laser cladding of piston rings. Confidential until 2008-12-31

Place, publisher, year, edition, pages
Keyword [en]
Technology, laser cladding, manufactiuring, production
Keyword [sv]
URN: urn:nbn:se:ltu:diva-47862ISRN: LTU-EX--06/024--SELocal ID: 55c55fed-469f-4ab8-b1f0-17ad35407716OAI: diva2:1021192
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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