Papers by Keyword: In Situ Experiment

Abstract: Natural physical cavity. Quantification of annual temperature regime of natural physical cavity by in-situ experiment. Annual course of temperature of outdoor climate. Annual course of maximum temperature of natural physical cavity of optimal south-west orientation. Concept of new possibilities for energy utilization of air from natural physical cavities. Two-stage system for utilization of renewable energy sources.

Abstract: A coupled finite element–thin layer element (FE-TLE) model for the prediction of subway induced vibrations was developed. With this model, the soil-tunnel system is divided into two parts, i.e., the tunnel structure and layered soil with a tunnel type hole. The tunnel structure is simulated by finite elements and the layered soils with hole by thin layer elements. The model fully accounts for the dynamic interaction between the tunnel and the soil. The numerical models for train-induced ground-borne vibrations were validated by in-situ experiments.

Abstract: Seismic subsidence of loess is a kind of disaster induced by strong ground motion in loess area, while seldom example of this subsidence was found in long time study, usually instead of laboratory test. An explosion ground motion in a typical loess field was designed to verify seismic subsidence of loess with natural condition and laboratory test of loess seismic subsidence was conducted in China. The result proved seismic subsidence of loess could be induced by explosion ground motion, while the maxmuim settlement of 3.3cm in the case of experiment is much less than 53cm with a moderate or strong dynamic stress in laboratory due to an incomplete seismic subsidence of loess in this field. The seismic subsidence of toper loess layers is less than the below in the field test although it is opposite to in laboratory test due to closer distance between the below layers and explosion shots.

Abstract: The understanding of the dynamics of substructures during deformation and annealing is fundamental in our ability to predict microstructural and physical properties such as rheological behaviour of crystalline materials. Here, we present an overview of new insights into substructure dynamics through a combination of in-situ heating experiments, detailed Electron Backscatter Diffraction (EBSD) analysis and numerical modelling.

Abstract: The combination of high temperature (1050°C -1150°C) testing and in situ high energy X-Ray diffraction measurements using synchrotron Three Crystal Diffractometry may give various insights into the mechanical behaviour of superalloys: measurement of the lattice mismatch, order within the ' phase, elastic constants, and dynamic response to changes in the experimental conditions. Several examples are given on the rafted AM1 superalloy, resulting from experiments at the ID15A (ESRF) and BW5 (DESY) high energy beamlines.

Abstract: One of the major ingredients of modelling the mechanical behaviour of superalloys is the knowledge of dislocation densities and strain distribution. Both can be measured using post mortem BF TEM and CBED, but such methods do not allow following their variations during a test. The aim of the present work is to investigate the usefulness of in situ X-Ray Three Crystal Diffractometry (TCD) to measure the density and distribution of dislocations within a rafted superalloy, i.e. during stage II of high temperature creep. As the instrument contribution is very low, the two-peaked experimental profiles are representative of the lattice parameter distribution within the material. The profiles were measured within bulk specimens at the BW5 high energy beamline Hasylab (DESY), during high temperature (1050°C to 1180°C) tests under loads between 0 MPa and 300 MPa. The peak shapes were observed to change with varying experimental conditions. The peak width follows different patterns under low and high stress, i.e. with low and high strain rates. The distribution of elastic strains was calculated by assuming two main contributions: dislocation segments trapped at the γ/γ’ interfaces in a more or less regular network, and dislocations moving within the γ’ rafts. A comparison between experimental and simulated peaks shows that several features of their behaviour can be explained: the absolute magnitude of the peak width, the observed decrease of the peak width under low loads with increasing interfacial dislocation densities. The larger increase in the width of the γ’ peak under high load (and strain rate) may be attributed to a dislocation density within the 1013 m-2 range within the rafts. The present results are presently being cross-checked by post mortem TEM observations.

Abstract: Time-resolved X-Ray Diffraction (TRXRD) experments were carried out to identify the phase transformation during welding in-situ. For the martensitic steel weld with different chemical compositions, the solidification behavior was directly analyzed in the time-resolution of 0.01 seconds. The halo pattern from the weld pool gives basis to observe the phase transformation during solidification process of weld. Furthermore, the latest development of TRXRD system was outlined. The importance of detector area was discussed and brand-new TRXRD system in real and reciprocal lattice space was presented.

Abstract: When the Al/Ge/SiO2 bilayer films are annealed in-situ in a scanning electron microscope (SEM) at the temperatures lower than the crystallization temperature of amorphous Ge itself, the so-called metal-mediated-crystallization (MMC) takes place. In the course of MMC, crystalline Ge aggregates (Ge clusters) form in the bilayer films, which results in the formation and the evolution of impressive fractal patterns with branching on the free surface. In-situ SEM observations of annealed Al/Ge/SiO2 bilayer films indicate that the grain size of polycrystalline Al-layer influences the nucleation of Ge clusters and hence of fractal patterns. For the bilayer films containing larger Al grains, the nucleation rate of fractal patterns (Ge clusters) is faster and the number of patterns is larger.

Abstract: High-energy synchrotron X-ray diffraction is a novel and powerful tool for bulk studies of materials. In this study, it is applied for the investigation of an intermetallic γ-TiAl based alloy. Not only the diffraction angles, but also the morphology of reflections on the Debye-Scherrer rings are evaluated in order to approach lattice parameters and grain sizes as well as crystallographic relationships. An in-situ heating cycle from room temperature to 1362 °C has been conducted starting from massively transformed γ-TiAl which exhibits high internal stresses. With increasing temperature the occurrence of strain relaxation, chemical and phase separation, domain orientations, phase transitions, recrystallization processes, and subsequent grain growth can be observed. The data obtained by high-energy synchrotron X-ray diffraction, extremely rich in information, are interpreted step by step.

Abstract: Variations in the lattice parameters of γ and γ' phases perpendicular to the [001] tensile axis were recorded in situ at ~10 minutes intervals using the Triple Axis Diffractometer of the High Energy (ID15) beamline at ESRF. Testing was carried out on an AM1 superalloy specimen with a raft microstructure at high temperature (1072°C) under load steps between 0 MPa and 300 MPa. These data were used to evaluate the Young modulus and the effective (Von Mises) stresses within the γ' rafts and γ corridors, as well the average plastic strain rates of each phase. The recorded stress data scatter was within the MPa range, and should be good enough to probe the elementary mechanisms of plasticity.