Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding bead...Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.展开更多
The first pictures of the earth were taken from a balloon in the mid-19^(th) century and thus started‘earth observation’.Aerial missions in the 20^(th) century enabled the build-up of outstanding photographic librar...The first pictures of the earth were taken from a balloon in the mid-19^(th) century and thus started‘earth observation’.Aerial missions in the 20^(th) century enabled the build-up of outstanding photographic libraries and then with Landsat-1,the first civilian satellite launched in 1972,digital images of the earth became an operational reality.The main roles of earth observation have become scientific,economic and strategic,and the role of synthetic aperture radar(SAR)is significant in this overall framework.Radar image exploitation has matured and several operational programs regularly use SAR data for input and numerous applications are being further developed.The technological development of interferometry and polarimetry has helped further develop these radar based applications.This paper highlights this role through a description of actual applications and projects,and concludes with a discussion of some challenges for which SAR systems may provide significant assistance.展开更多
基金CONACyT-México for the scholarship providedCONACyT (Project 736)SIP-IPN are also acknowledged for funds given to conduct this research
文摘Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.
文摘The first pictures of the earth were taken from a balloon in the mid-19^(th) century and thus started‘earth observation’.Aerial missions in the 20^(th) century enabled the build-up of outstanding photographic libraries and then with Landsat-1,the first civilian satellite launched in 1972,digital images of the earth became an operational reality.The main roles of earth observation have become scientific,economic and strategic,and the role of synthetic aperture radar(SAR)is significant in this overall framework.Radar image exploitation has matured and several operational programs regularly use SAR data for input and numerous applications are being further developed.The technological development of interferometry and polarimetry has helped further develop these radar based applications.This paper highlights this role through a description of actual applications and projects,and concludes with a discussion of some challenges for which SAR systems may provide significant assistance.
