• JLA Vol:9 Iss:1 (Characteristics of CO<sub>2</sub> laser welded high carbon steel gauge plate)

    Eng S. Ng
    Ian A. Watson
    Laser and Optical System Engineering Center, Department of Mechanical Engineering, James Watt Building, University of Glasgow, Glasgow G12 8QQ, U.K.

    The welding performance of CO2 lasers is strongly affected by the clamping geometry and welding speed. Moreover, the rapid cooling rate associated with laser welding results in an untempered martensitic structure and a transverse variation in the hardness profile. An untempered martensitic structure can lead to brittle welds, and particularly for samples that are subject to cyclic loading, component fatigue and failure. To avoid this problem it is useful to optimize the laser operat...


  • JLA Vol:9 Iss:1 (Continuous wave Nd:YAG laser cladding modeling: A physical study of track creation during low power processing)

    J&hyphen;.M. Jouvard
    D. F. Grevey
    F. Lemoine
    A. B. Vannes

    This paper concerns the modeling of cladding using an Nd:YAG laser operating at low powers typically less than 800 W. Experimental observation of the evolution of the mass of the clads shows two power thresholds. The theoretical study relies on a calculation of the fluence provided to the substrate and on a model of heat transfer into the substrate. We suggest that the first threshold is the power required for substrate melting. The second power is the threshold when the powder is directly melted by the beam and is therefore a liquid when contacting the substrate.


  • JLA Vol:9 Iss:1 (Laser cladding of Al&hyphen;Sn alloy on a mild steel)

    Z. Liu
    J. L. Sun
    W. M. Steen
    K. G. Watkins
    C. Lee
    W. P. Brown

    Direct laser cladding of Al alloy on mild steel produces continuous brittle intermetallic FexAly layers at the interface resulting in weak bonding of the clad and the substrate. To overcome this problem, both Ni and Al were investigated as intermediate coatings. Although a Ni coating with a thickness of 70 μm was successful in eliminating the formation of continuous Al&hyphen;Fe intermetallics, the bonding at the Al alloy/Ni interface was not strong enough to survive a bending test. A pure Al coating was found to be a better ...


  • JLA Vol:9 Iss:1 (Laser generated air contaminants released during laser cutting of fabrics and polymers)

    Max Kiefer
    C. Eugene Moss
    National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, OH 45226, U.S.A.

    Environmental monitoring was conducted at an industrial facility to qualitatively identify the major contaminants generated while cutting fabrics and polymers with a 25 W CO2 continuous beam laser. Carbon monoxide, hydrogen cyanide, and particulates were also assessed, and a bulk sample of residue from the laser exhaust duct was analyzed for inorganic acids, pH, and volatile organic compounds. Samples were collected while cutting vinyl, acrylics, woven fabrics, felt, Formica®, and Plexiglass®....


  • JLA Vol:9 Iss:1 (On the formation of the keyhole and its temperatures)

    E. A. Metzbower
    US Naval Research Laboratory, Code 6320, Washington, DC 20375&hyphen;5000, U.S.A.

    A thermodynamically based model has been developed to calculate the size and temperature of the ‘keyhole’ through the thickness of the weldment. The model is based on calculating the power loss resulting from evaporation of an element in the chemistry of the plate and a minimum power density required to produce a keyhole. The evaporative power loss is set equal to the Gaussian power density, which is used to represent the laser beam. The result is a temperature distribution across the keyhole. Absorption of the laser power in the keyhole is calculated based on inverse...


  • JLA Vol:9 Iss:1 (The development of a laser machining curriculum: An interdisciplinary approach (the MAST program))

    Gary J. Masciadrelli
    Nicholas M. Massa

    The development of an industry&hyphen;driven interdisciplinary curriculum in laser machining is presented. The Machine tool Advance Skills Technology (MAST) program is a US Department of Education grant to develop and demonstrate a national training model for new technologies and manufacturing processes in precision manufacturing. Springfield Technical Community College (STCC) in partnership with six other community colleges nationwide, developed, tested, and disseminated industry&hyphen;specific skills standards and model curricula in laser machining and related technologies for the United States machine tool industry. STC...


  • JLA Vol:9 Iss:2 (Integration of real time quality control systems in a welding process)

    E. Nava&hyphen;Ru¨diger
    M. Houlot
    Ecole Nationale Supe´rieure d'Arts et Me´tiers, Laboratoire Proce´de´s et Techniques de Production Me´canique, Paris, France

    The automation of laser welding processes requires the control of the various process components as well as the control of the laser—material interaction. These systems are essential for ensuring the quality of the weld seam as they are able to react to dynamic fluctuations during the process. During the process various phenomena occur which are potential sources of diagnostic signals: these include thermal, electrical, optical, mechanical and acoustic events. This pa...


  • JLA Vol:9 Iss:2 (Kinematic compensation of repetitive errors for non&hyphen;circular laser shaping)

    P. Sheng
    K. Liu
    Department of Mechanical Engineering, University of California, Berkeley, CA, U.S.A.

    This paper presents an approach for kinematic compensation of the laser shaping process which is capable of achieving improved dimensional accuracy for non&hyphen;circular profiles. In this approach, a plug&hyphen;in repetitive controller is added into the existing position servo loop to improve tracking of the desired sinusoidal trajectory and subsequently reduce tracking errors. The effect of tracking errors on different dimensional error modes in the non&hyphen;circular shaping process is identified. Simulation models are developed for testing the performance o...


  • JLA Vol:9 Iss:2 (Laser cladding with a pulsed Nd:YAG laser and optical fibers)

    M. Brandt
    D. A. Scott
    S. B. Emms
    J. M. Yellup

    A new laser cladding technique for producing wear and corrosion resistant surfaces on engineering components is reported. The technique involves the combination of the pre&hyphen;placed and injected powder delivery methods for producing clad layers. The clad layers were formed with a pulsed Nd:YAG laser and optical fibers. The results using a nickel&hyphen;based alloy (Hastelloy C) indicate that uniform clad layers in excess of 1 mm in thickness can be achieved in a single pass with 240 W average power incident on the workpiece. The laser beam was delivered through a step&hyphen;index glass ...


  • JLA Vol:9 Iss:2 (Relationship between airborne acoustic and optical emissions during laser welding)

    D. Farson
    Y. Sang
    A. Ali
    Department of Industrial, Welding and Systems Engineering, Ohio State University, Columbus, OH, 43210 U.S.A.

    This paper describes experimental work directed at understanding the relationship between acoustic and optical emissions from the laser welding process. Laser welds were performed and the emissions were measured with a microphone and photodiode and recorded with a data acquisition system. A time&hyphen;domain correlation analysis of the acoustic and optical signals revealed them to be highly related at a phase shift corresponding to the delay time for sound to propagate from the weld area to the microphone. A moving av...



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