There is expounded the theory of＂gravitational＂ wave propagation from the volcano crater （magma） under changing density of magma mass inside the volcano. It was revealed that while the abruptly accelerated magma m...There is expounded the theory of＂gravitational＂ wave propagation from the volcano crater （magma） under changing density of magma mass inside the volcano. It was revealed that while the abruptly accelerated magma movement during starting period began eruption, the registered ＂gravitational＂ waves were being emitted and were propagating with the velocity greater than that of sound and seismic waves velocity. Alteration of ＂gravitational＂ waves velocity under the magma movement can be additional feature in prognosis of the start time of volcano eruption. The considered method might be effective when making up prognoses of underwater volcano eruption.展开更多
The theoretical design method of enhanced sensitivity fiber grating （FBG） strain sensors was given, and moreover high qualified strain sensors were developed and fabricated, whose sensing properties were good for pr...The theoretical design method of enhanced sensitivity fiber grating （FBG） strain sensors was given, and moreover high qualified strain sensors were developed and fabricated, whose sensing properties were good for practical applications. The strain sensor with cylindrical shell encapsulation contained three tubular structures, due to the uneven surface structure, in the area of the strain concentration, improving the sensitivity. It could achieve the embedment strain measurement and surface measurement and had the advantages of the easy installation. The good agreement was obtained between the measurements and theoretical simulation results. After each calibration test, twenty-four FBG strain sensors and six FBG temperature compensation sensors have been installed on the undersurface of the box girder of Diaoshuiyan bridge in Yongtaiwen highway. Finally, we built up a long-term structure health system for the highway bridge.展开更多
The indentation test is a localized testing technique;therefore,the role of the material size-effect and local non-uniformity is of much importance.The influence of the heterogeneity in size-independent materials has ...The indentation test is a localized testing technique;therefore,the role of the material size-effect and local non-uniformity is of much importance.The influence of the heterogeneity in size-independent materials has been studied previously.The present work detailedly investigated the influence of the material size-effect and heterogeneity(inclusions near the indenter tip)on the indentation hardness using a size-dependent strain gradient plastic theory.And it was found that when considering the material size-ffect,shallow hard inclusions in the heterogeneous materials more significantly enhance the material indentation hardness compared with the size-independent materials which are based on the conventional plastic theory.This hardening effect is be-lieved to be related to the elevation of the load and local constraints of large deformation.The effect of material inhomogeneity mainly comes from the non-uniformity of the structure rather than the inclusion modulus itself especially when the size-effect is involved,and the transition range of the inclusion modulus'influence is pretty narrow.The effect of non-uniformity becomes negligible after the initial inclusion depth is larger than its diameter.The horizontal offset of the indenter from the inclusion is also of much sensitivity to the influence of the heterogeneous indentation.This paper focuses on the scaling relationships in micro-and nanoindentation,the influence of non-uniformity in microscopic materials is studied and supplemented as well.展开更多
文摘There is expounded the theory of＂gravitational＂ wave propagation from the volcano crater （magma） under changing density of magma mass inside the volcano. It was revealed that while the abruptly accelerated magma movement during starting period began eruption, the registered ＂gravitational＂ waves were being emitted and were propagating with the velocity greater than that of sound and seismic waves velocity. Alteration of ＂gravitational＂ waves velocity under the magma movement can be additional feature in prognosis of the start time of volcano eruption. The considered method might be effective when making up prognoses of underwater volcano eruption.
文摘The theoretical design method of enhanced sensitivity fiber grating （FBG） strain sensors was given, and moreover high qualified strain sensors were developed and fabricated, whose sensing properties were good for practical applications. The strain sensor with cylindrical shell encapsulation contained three tubular structures, due to the uneven surface structure, in the area of the strain concentration, improving the sensitivity. It could achieve the embedment strain measurement and surface measurement and had the advantages of the easy installation. The good agreement was obtained between the measurements and theoretical simulation results. After each calibration test, twenty-four FBG strain sensors and six FBG temperature compensation sensors have been installed on the undersurface of the box girder of Diaoshuiyan bridge in Yongtaiwen highway. Finally, we built up a long-term structure health system for the highway bridge.
基金the National Natural Science Foundation of China(Grant Nos.11890681,12032001,and 11521202).
文摘The indentation test is a localized testing technique;therefore,the role of the material size-effect and local non-uniformity is of much importance.The influence of the heterogeneity in size-independent materials has been studied previously.The present work detailedly investigated the influence of the material size-effect and heterogeneity(inclusions near the indenter tip)on the indentation hardness using a size-dependent strain gradient plastic theory.And it was found that when considering the material size-ffect,shallow hard inclusions in the heterogeneous materials more significantly enhance the material indentation hardness compared with the size-independent materials which are based on the conventional plastic theory.This hardening effect is be-lieved to be related to the elevation of the load and local constraints of large deformation.The effect of material inhomogeneity mainly comes from the non-uniformity of the structure rather than the inclusion modulus itself especially when the size-effect is involved,and the transition range of the inclusion modulus'influence is pretty narrow.The effect of non-uniformity becomes negligible after the initial inclusion depth is larger than its diameter.The horizontal offset of the indenter from the inclusion is also of much sensitivity to the influence of the heterogeneous indentation.This paper focuses on the scaling relationships in micro-and nanoindentation,the influence of non-uniformity in microscopic materials is studied and supplemented as well.
