JLA Vol:7 Iss:4 (Overview of laser technology at Los Alamos National Laboratory)

Authors:
Gary K. Lewis
David A. Cremers

JLA Vol:6 Iss:1 (Measurement of temperature and absorptance for laser processing applications)

Authors:
S. Ramanathan
M. F. Modest
Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A.

The use of CO₂ lasers has been successfully demonstrated for several manufacturing processes such as cutting, drilling, scribing, etc., of a wide range of materials. The absorptance of a material at the laser wavelength and at the material removal temperature substantially affect the efficiency of the laser machining process. Some materials have absorption bands in the mid‐infrared and the absorptance changes drastically with temperature at the CO₂ laser wavelength of 10.6 μm. Additionally, the absor...

JLA Vol:6 Iss:1 (Effects of process parameters on the fatigue strength of laser beam welds)

Authors:
P. C. Wang
K. M. Ewing

An experimental study, augmented by three‐dimensional finite element analysis, was performed to assess the effects of various process parameters such as presence of galvanized coating, welding speed and weld geometry (weld start and stop, metal fit‐up, and weld orientation) on the fatigue resistance of laser beam welds. It was found that the fatigue resistance of laser beam welds depends upon the welding speed used and weld geometry. With a 2.75 kW CO₂ laser and at a welding speed of 38.1 mm s⁻¹, the resultant laser beam welds gave the highest fatigue resistance. For a continuous weld, maintaining ...

JLA Vol:6 Iss:1 (Laser safety notes)

Authors:
Robert Weiner
Weiner Associates, Manhattan Beach, California U.S.A.

JLA Vol:7 Iss:4 (Laser Applications in Science Education (LASE) Project at Santa Teresa High School)

Authors:
James D. Sagray
Science Department, Santa Teresa High School, San Jose, California 95123, U.S.A.

The goal of the Laser Applications in Science Education (LASE) Project, centered at San Jose State University, is to bring significant laser technology and optics to the secondary level with a special emphasis on student research and publication. Its implementation at Santa Teresa High School has focused on permitting all students in physics classes (32/period) to experience laser labs in small groups working throughout the classroom. In addition to receiving this exposure, all physics students are encouraged to do original research projects and to compete for cash or other prize...

JLA Vol:7 Iss:4 (Laser applications in science education (LASE) Project: an introduction to photonics at the secondary school level)

Authors:
Gareth T. Williams
Physics Department, San Jose State University, San Jose, California, U.S.A.

JLA Vol:7 Iss:4 (Laser machining of ablating materials — overlapped grooves and entrance/exit effects)

Authors:
Michael F. Modest
Sriram Ramanathan
Armin Raiber
Birgit Angstenberger

A three‐dimensional conduction model has been developed to predict the transient temperature distribution inside a thick solid that is irradiated by a moving laser source, and the changing shape of single or overlapping grooves carved into it by evaporation of material. The laser may operate in CW or in pulsed mode (with arbitrary temporal intensity distribution) and may have an arbitrary spatial intensity profile. The governing equations are solved, for both constant and variable thermophysical properties, using a finite‐difference method on a boundary&...

JLA Vol:7 Iss:3 (Laser beam surveying, refractive index measurements and the making of a 360° reflection hologram)

Authors:
David Foster
Notre Dame High School, 596 South Second St., San Jose, California 95112, U.S.A.

Triangulation measurements, using a laser to find the height of a room and of buildings, will be described first. This will be followed by triangulation and laser beam divergence measurements for range finding. The use of a hollow prism to hold liquids, whose refractive indicies are to be found, will then be described. The final topic will describe how a 360° reflection hologram was made at Notre Dame High School, utilizing three lasers and beam spreaders and four lasers and beam spreaders. The 360° hologram, made by a student, will be available for viewing.

JLA Vol:7 Iss:4 (Laser cutting of thick sectioned steels using gas flow impingement on the erosion front)

Authors:
P. M. Ilavarasan
P. A. Molian
Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, U.S.A.

An off‐axial gas jet has been developed that has the potential to extend the laser's effectiveness by improving the rate at which parts can be machined, producing high‐quality surfaces, enhancing the cutting thickness, and adding to the range of materials that can be machined. In laser cutting, an erosion front (liquid–gas region) forms at the momentary end of the cut. Laser heating, exothermic reactions and shear force between the gas flow and the molten layer dictate the material removal rates. The principle of the off‐axi...

JLA Vol:6 Iss:1 (Mass transport during laser welding of stainless steels and alloys used by US Navy)

Authors:
Anand J. Paul
Parwaiz A. A. Khan
Manufacturing and Materials Division, Concurrent Technologies Corporation, 1450 Scalp Avenue, Johnstown, PA 15904, U.S.A.

Lasers, though developed only about a quarter century ago, are now being routinely used in the automotive, aerospace and other industries to produce superior quality, high‐speed autogenous welds with narrow heat‐affected zones in a number of alloys. However, they cannot at present be used to successfully weld certain important structural alloys due to a change in weld composition resulting from selective mass transport of certain alloying elements from the laser‐melted region. The loss of a...