Numerical analysis of detaching and wrinkling of mechanically lined pipe during its spooling-on stage to the reel

The structural behavior of mechanically lined pipes （MLPs） during the spooling-on phase is investigated in this paper, motivated by their promising offshore applications relying on reel installation. By applying quasi 2D models, we first investigated the gripping stresses preserved in the MLP after the hydraulic expansion manufacturing process and the detachment of the liner under spooling-on curvatures. Furthermore, a comparative 3D finite element （FE） analysis for the liner wrinkling behaviors of MLP with different wall thicknesses of outer layers was performed and indicated that when the wall thickness of outer layer increases from 14.3 mm to 17.9 mm, MLP＇s critical spooling-on curvature increased more than 47%, reachin0.1432 rdd/m.

A comparison of electromigration failure of metal lines with fracture mechanics

Atoms constructing an interconnecting metal line in a semiconductor device are transported by electron flow in high density. This phenomenon is called electromigration, which may cause the line failure. In order to characterize the electromigration failure, a comparison study is carded out with some typical phenomena treated by fracture mechanics for thin and large structures. An example of thin structures, which have been treated by fracture mechanics, is silica opti- cal fibers for communication systems. The damage growth in a metal line by electromigration is characterized in compar- ison with the crack growth in a silica optical fiber subjected to static fatigue. Also a brief comparison is made between the electromigration failure and some fracture phenomena in large structures.

Type Synthesis of Spatial Straight Line Mechanisms with only Revolute Joints

Spatial straight line mechanisms are a class of spatial mechanisms whose end-effectors generate the trajectory with the form of exact straight lines, which have potential applications in many industrial sectors. This study aims to synthesis the spatial straight line mechanisms with only revolute joints, meaning that no prismatic joints are included. According to the generalized function sets and the law of one dimensional rotation, the type of compositions of characteristic and the corresponding conditions are derived. Furthermore, some novel symmetrical and asymmetrical spatial straight line mechanisms are synthesized through assembling specific kinematic chains under the corresponding conditions. Finally, several synthesized spatial straight line mechanisms are illustrated to show the effectiveness of the synthesis methodology.

Description of a Propulsion Unit Used in Guiding a Walking Machine by Recognizing a Three-point Bordered Path

A reconfigurable propulsion unit based on the Peaucellier-Lipkin mechanism has the ability to describe exact straight or curved paths depending on the selected ratio between the lengths of two of its links. The Peaucellier-Lipkin mechanism with one degree of freedom is transformed into a more sophisticated parallel kinematic chain by including four more degrees of freedom. The resulting propulsion unit is able to adapt its kinematic structure and reach instant centers of rotation, in accordance with the presence of three points that border a geometric path. A laser sensor mounted on the body of the machine detects each point. Once the machine has detected the exact location of the border of the road, it walks along a curve parallel to that border. Although the proposed research describes only one propulsion unit or leg, the methodology can be applied to all the legs of the walking machine. The novel 5-DOF leg is able to reach different centers of rotation, providing either the concave or convex arcs that satisfy the basic principle of displacement of walking machines.

A Possible Pumping Mechanism for Interstellar Class Ⅱ107 GHz Methanol Masers

It is recognized that the interstellar methanol-107GHz masers and OH-4.765 GHz masers towards Class II sources are associated with each other and coexist towards ultracompact HII regions. Therefore we suggest a new pumping mechanism - methanol masers without population inversion. It can explain the formation of 107GHz methanol masers, with the 4.765 GHz OH masers acting as a driving coherent microwave field. It is argued that this mechanism is compatible with the astronomical conditions.