A mortar formulation for frictionless line-to-line beam contact

This paper describes the quasi-static formulation of frictionless line contact between flexible beams by employing the mortar finite element approach. Contact constraints are enforced in a weak sense along the contact region using Lagrange multipliers. A simple projection appropriate for thin beams with circular cross-sections is proposed for the computation of contact regions. It is combined with the geometrically exact beam formalism on the Lie group $SE(3)$ S E ( 3 ) . Interestingly, this framework leads to a constraint gradient and a tangent stiffness invariant under rigid body transformations. The formulation is tested in some numerical examples.

A study on the removal of paint and oxide layer on the steel surface by laser beam scanning method

In this study, a laser cleaning method was developed in order to replace the existing manual work-based technologies. The experimental investigation analyzed the cleaning properties of the paint and the oxide layer on the steel surface according to the laser beam scanning method. Experiments showed that in the cleaning process, the line beam patterns with a moving stage showed differences in heat input depending on the area, and the square area beam patterns obtained with control of a Galvano scanner showed uniform cleaning performance. The results of this study demonstrated that through the prosed laser cleaning technique, oxide layers as well as paint on steel surfaces can be removed with excellent precision, which is expected to be useful in the development of eco-friendly surface cleaning techniques.

An improved high-precision Jacob's staff with laser sighting and topographic capabilities for the high-resolution stratigrapher

ABSTRACT Accurate and quick high-resolution measurements of stratigraphic thicknesses and geologic profiles exposed in surface outcrops are critically important for interpreting depositional environments, basin development, and tectonic evolution. Therefore, a high-precision instrument is required for high-resolution stratigraphic measurements. Herein, a new version of the Jacob's staff incorporating an Abney level or a geological compass, a laser pointer, and a handheld GPS is presented. Both the Abney level and the laser pointer are oppositely positioned side by side at the 1.5 m position on the 1.6-m-long fiberglass rod, and they can synchronously slide vertically and rotate horizontally. Because accurate sighting of bedding surfaces is facilitated with both the sighting tube of the Abney level and straight-line beam of the laser pointer, this novel design greatly improves the precision and speed of stratigraphic thickness measurements. More importantly, when the section requires a lateral shift, the straight-line beam can easily and precisely identify the new start point without rotating the rod, which greatly reduces potential changes in the angle of the rod. The GPS unit installed at the top of the rod synchronously records the track of the measured section and coordinates of each measurement, which enables acquisition of a topographic profile along the stratigraphic section. Uncertainties in stratigraphic thickness measurements are minimized when observations are made through the sight tube of the Abney level when the rod is oriented perpendicular to the bedding surface.