Heterogeneous Microstructure-Induced Creep Failure Responses in Various Sub-Zones of Modified 310S Welded Joints

In order to reveal the creep failure behavior of novel modified 310S austenite steel welded joints, the creep life and microstructure evolution of the 310S austenite steel welded joints were investigated in this study. The rupture life was assessed to estimate the damage of the welded joint based on creep rupture tests performed at 600 °C in the stress range of 170–238 MPa. Compared with WM, HAZ facilitated the occurrence of creep failure in long term creep due to the combination of a smaller hardness value, a more heterogenous microstructure accompanied by coarsened M23C6, a larger grain size, higher KAM and Schmid factor. Discontinuous Laves phases appeared near the boundaries between the δ-ferrite and γ-austenite grains in the WM, and dislocation strengthening and precipitation strengthening were observed near the boundary in the BM. Furthermore, segregation elements were detected by APT and EDS adjacent to the boundary. Cr and C segregation near grain boundaries weaken the creep resistance in long term creep service.

Detecting Long-Term Deformation of a Loess Landslide from the Phase and Amplitude of Satellite SAR Images: A Retrospective Analysis for the Closure of a Tunnel Event

Information about the long-term spatiotemporal evolution of landslides can improve the understanding of landslides. However, since landslide deformation characteristics differ it is difficult to monitor the entire movement of a landslide using a single method. The Interferometric Synthetic Aperture Radar (InSAR) and pixel offset tracking (POT) method can complement each other when monitoring deformation at different landslide stages. Therefore, the InSAR and improved POT method were adapted to study the pre- and post-failure surface deformation characteristics of the Gaojiawan landslide to deepen understanding of the long-term spatiotemporal evolution characteristics of landslides. The results show that the deformation displacement gradient of the Gaojiawan landslide exhibited rapid movement that exceeded the measurable limit of InSAR during the first disaster. Moreover, the Gaojiawan landslide has experienced long-term creep, and while studying the post-second landslide’s failure stability, the acceleration trend was identified via time series analysis, which can be used as a precursor signal for landslide disaster warning. Our study aims to provide scientific reference for local governments to help prevent and mitigate geological disasters in this region.

Creep Behavior of Polyamide 12, Produced By Selective Laser Sintering With Different Build Orientations

The successful use of components, produced by selective laser sintering as a rapid manufacturing process, requires a comprehensive understanding of the material. In this study, the effect of specimen build orientation on the mechanical properties of selective laser sintered polyamide 12 was investigated in detail. Samples were printed with an orientation of 0°, 15°, 45° and 90° to the build platform. Additionally to quasi-static tensile tests, Creep tests under different loads (5 MPa, 10 MPa, 15 MPa and 20 MPa) and for different times (10 hours and 1,000 hours) with and without relaxation were performed. Creep behavior was analyzed using the Burgers model. Therefore, the elastic strain, the relaxant strain, the viscous strain and the total deformation were determined. Results show that the build orientation has no significant influence on the long-term creep behavior, at small stresses. Short-term creep and relaxation tests show, that the elastic and viscous strain are only slightly influenced by the build orientation. However, the viscoelastic strain is affected by the build orientation. Furthermore, the deformations resulting from creep and relaxation have no significant influence on the mechanical behavior as shown by tensile tests.