Development of Creep Damage in Similar Weld Joints of P92 Steel Pipe

The microstructure and creep behaviour of the welded joints of P92 steel pipe were investigated in order to determine the influence of orbital heat welding technology on the creep resistance. Creep specimens were machined from the welded joints. Tensile creep tests of welded joints were performed at 873 K using different stresses. The microstructure of tested specimens was investigated by scanning electron microscope Tescan equipped with an electron-back scatter diffraction. The creep results showed that the creep fracture strain of the welded joints decreases with decreasing value of applied stress. Microstructure investigation showed that fracture behaviour of welded joints is influenced by an enhanced cavity formation at grain boundaries in the heat-affected zone causing lower fracture ductility.

Multiple Toughening Mechanisms of Laminated Ti-TiBw/Ti Composites Fabricated by Diffusion Welding

Laminated Ti-TiBw/Ti composites behave a moderate loading capacity and high fracture ductility with non-castropic failure stage under three-point bending test. Fracture characteristics of laminated composites reveal many extrinsic toughening behaviors, such as, interfacial delamination, bucking and crack deflection, and the interfacial delamination is attributed to the weak bonding strength. Many strengthening and toughening mechanisms are presented in the TiBw/Ti composite layer, such as de-bonding effects of TiB whiskers, multi-fracture of TiB whiskers, crack trapping effect and crack bridging effect.

Performance of Cross Bracings under Reverse Cyclic Loading

Steel braces are widely used in seismic retrofit of buildings. However, their tendency of buckling under compression impairs their efficacy. In this paper, characteristics of a cross bracing with rigid intersection, including its bearing capacity, hysteretic property and fracture ductility are investigated. With the analysis results, performance-based design requirements of a steel cross bracing are proposed based on its width-thickness ratio and effective slenderness ratio.

Fracture Test on High Strength Steel Plates with Elliptical Hole

In order to study fracture mechanics of high strength steel with the moderate thickness, fracture tests were performed on 10 plates with elliptical hole fabricated from high strength steel Q345 with the thickness of 16mm. The effect of the notch sharpness (the ratio of the length of short axis to that of long axis of elliptic hole, b/a) and the notch depth (the ratio of the length of long axis of the elliptic hole to the width of plate, 2a/w) on fracture model of high strength steel was examined. Test results show that the first crack initiates at the notch edge. The fracture ductility is lower for the specimens with the sharper notch (a smaller ratio b/a) and the deeper notch (a larger ratio 2a/w), and the point of crack load lies in hardening phase of load-displacement curve. The fracture ductility is higher for the specimens with the obtuse notch (a larger ratio b/a), and the point of fracture load lies in necking phase of load-displacement curve. The ultimate strength of notched plates is independent of the notch sharpness (b/a) and the notch depth (2a/w).