The Investigation of Structure Heterogeneous Joint Welds in Pipelines

Welding joints of dissimilar steels don’t withstand design life. One of the important causes of premature destructions can be the acceleration of steel structural degradation due to cyclic mechanical and thermal gradients. Two zones of tube from steel 12H18N9T, exhibiting the structural instability at early stages of the decomposition of a supersaturated solid austenite solution, were subjected to investigation. Methods of x-ray spectral and structure analysis, micro hardnessmetry were applied for the research. Made the following conclusions, inside and outside tube wall surfaces of hazardous zones in welding joint have different technological and resource characteristics. The microhardness very sensitive to changes of metal structure and can be regarded as integral characteristic of strength and ductility. The welding processes are responsible for the further fibering of tube wall structure, they impact to the characteristics of hot-resistance and long-term strength due to development of ring cracks in the welding joint of pipeline. The monitoring of microhardness and structural phase conversions can be used for control by changes of mechanical properties in result of post welding and reductive heat treatment of welding joints

Pulsed optical timing distribution system with sub-ps accuracy for applications in geodesy.

Here we report on the recent progress of the highly stable optical pulsed Timing Distribution System (TDS) commissioned at the geodetic observatory in Wettzell (Germany). The system connects a master clock (H-maser) to a mode-locked femtosecond-laser, which in turn uses delay compensated fiber lines for the coherent transmission of time and frequency. In order to use time itself for sensitive delay compensation, we developed a new generation of electronic interfaces for the generation and distribution of Pulse-Per-Second (PPS) signals with sub-ps stability, a low temperature coefficient (1ps/°C) and a constant delay with respect to the master reference. For the interfacing to the respective measurement systems, a set of required standard RF-Signals (5, 10, 100 MHz) with low phase noise (-160 dBc/Hz at 10kHz) and high fractional frequency stability (Allan Deviation 8x10-14 in 1s) are provided. This indicates that the system indeed distributes the stability of the master clock without penalties, which is equivalent to having a true copy of the master clock in perfect synchronization at each end point