We have successfully demonstrated that the stress distribution of a metal substrate can be
directly displayed by coating SrAl2O4:Eu (SAO), a representative of strong mechanoluminescent
materials, on the surface of test objects. An aluminum plate with SAO sensing film had been applied to
experimental analysis of stress concentrations, and a numerical calculation via a finite element method
confirmed that the observed real time mechanoluminescence images displayed the stress distribution. As
a result, visualization of stress distribution on metal surface has been realized by ML images using SAO
sensing film, and this novel visualization technique can be applied for viewing the stress concentration in
various fields such as modeling, manufacturing and demonstration of an industrial product.
Dynamic visualization of stress distribution even due to a small deformation has been realized by
coating the surface of the test object of metal with a upgrade mechanoluminescence (ML) material
of SrAl2O4:Eu (SAO). In this paper we report the application of this ML sensing technique to stress
concentration analysis on an aluminium plate. And the comparison with a theoretical calculation
demonstrated that the ML intensity of SAO sensing film correlates linearly with von Mises stress on
metal surface and the observed real-time ML images quantitatively reflect stress concentration.
We have demonstrated a novel blue-violet emitting mechanoluminscent(ML) material with calcium
aluminosilicate(CaAl2Si2O8:Eu2+). The ML was clearly visible to the naked eye in the atmosphere
and showed a similar spectrum to photoluminescence with a peak at 430nm. In order to enhance the
ML intensity, various rare earth ions were selected as co-dopants including La, Nd, Sm, Gd, Tb, Dy,
Ho, Er, Tm, Yb and Lu. It was found that the intensity of ML was strongly dependent on the kinds
of the codoped rare earth ion, especially the co-doping of Ho3+ was found to greatly enhance the
ML intensity. From the results of thermoluminescence(ThL) measurements, the enhancement of the
ML intensity was closely related with the filled trap concentration and trap depth.
It is inevitable for the construction of subways to pass under the existing structures in the city; this will cause settlement of the existing structures and affect their safety. The soil is a complex mixture, and hence it is difficult to determine the damage caused by construction using tunnel boring machine (TBM) method to the stress balance of the surrounding soil. Normally, settlement and uplift of the surface are caused during tunneling. Therefore, large-scale 3D simulations are needed to study the interaction between mechanically driven tunnel construction and the surrounding soil to estimate the expected settlement and related damage risks to the existing structures, especially in tunnel construction in urban areas. Qingdao Metro Line 1 in the Haixiao section (Xiaocunzhuang and Haiboqiao stations) was taken up as the research object to study the trend and degree of the effect of TBM tunnel construction using the numerical simulation software Midas GTS NX. The numerical simulation results and measured data were used for the reliability analysis to study the influence of different digging speeds and pressures in TBM construction on ground subsidence, and the effect of vibrations generated at the tunnel face by the TBM cutter head on the ground structure. It is shown that when other factors remain unchanged, the faster the driving speed, the smaller the ground settlement; the higher the surrounding rock pressure, the smaller the ground settlement. The vibration of the ground structure caused by the TBM cutter head complies with the relevant specifications. During construction, the driving parameters should be selected suitably depending on the available budget.
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