Application of phased array ultrasonic technology for nondestructive testing of railway wheels
A scheme is proposed to realize nondestructive testing (NDT) of railway wheels based on phased array ultrasonic testing technology in order to ensure the safe operation and high-speed of railway transport, and achieve accurate determine the defects of railway wheels. A phased array ultrasonic NDT system for wheels was designed. The system includes four main parts: system management software, probe moving and scanning parts, ultrasonic signal acquisition and imaging. A testing scheme for wheels was designed aiming at the configuration of railroad wheels and the distribution of defects in them. The wheels safety testing experiments were carried out on model wheels with artificial defects. Results of experiments demonstrate that the testing methods are more accurate in examining the depth and the location of defects in the wheels, and this system can obtain the defects status of wheels with higher sensitivity, higher facilitation and less affection by environmental factors.
Applications of Phased Array Techniques to NDT of Industrial Structures
In many industrial areas, such as nuclear, aircraft and oil industry, there is an increasing need for versatile Non Destructive Testing methods, able to ensure the reliab ility of complex structures. Ultrasonic (UPA) phased arrays have been widely studied for several years, sinc e they provide a powerful tool for improved adaptability to a wide range of applications. These phased a rrays rely on transducer splitted into an array of elements individually driven, which allows one to master the ultrasonic beam thanks to delay and amplitude laws. One advantage is the capability of phased array to i ncrease productivity of industrial application. A simple example of a thickness measurement will be developed in order to show how fast phased array can be compared to conventional techniques. One other advantage of pha sed array is their capability to overcome difficult geometrical problems thanks to their adaptability : electronic commutation, beam-steering and focusing in complex geometries. A specific flexible phased ar ray probe will be presented and applied on a nozzle inspection. This phased array is able to conform to a complex component, without degrading the radiated UT beam.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.