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 実験力学先端技術国際会議（ATEM07，日本機械学会材料機械部門 催）発表論文



■　Fracture evaluation on civil materials/structures by means of AE


　 Tomoki Shiotaniand  Dimitrios Aggelis 

■概要　
　Ageing of infrastructures is an un-avoidable issue. To sustain those as longaspossible
evenwith reasonable budgets, proper investigations giving quantitative evaluation of
soundness should be carried out at appropriate timing. Acoustic emissionamong NDT
techniques seems quiteuseful to monitor the global integrity ofcivil structures sinceone
sensor covers a wider range than other techniques and onlydamage-relatedcracks/defects 
induce the AE activity.In the paper,several damageindices obtained from AEparameters are
ntroduced and such applicationsas formaterials characterization and for in-situ 
structural evaluationare discussed.Through the applications, it is concludedthat AE 
monitoringhas potential to be a crucial monitoring technique contributing to expand
the service life of civil structures.





■　Stress wave scattering: an enemy or a friendof concrete non destructive testing


　 Dimitrios Aggelisand  Tomoki Shiotani 

■概要　
　Cementitious materials are by definition inhomogeneous containing cementpaste, sand,
aggregates as well as air voids. Wave propagation in such a material is characterizedby 
scattering phenomena.Damage in the form of microor macro cracks certainly enhances 
scattering influence. Its most obvious manifestation is the velocity variation with
 frequency and excessiveattenuation. The influence becomes stronger with increased mis
-match of elastic properties ofconstituentmaterials and higher crack content. Therefore,
in many cases of large concrete structures,field application of stress wavesis hindered
 since attenuation makes the acquisition of reliable signals troublesome.However, measured
 wave parameters, combined with investigation with scattering theory can revealmuch about
the internal condition and supply information that cannot be obtained in any other way.
The size and propertiesof the scatterers leave their signature on the dispersionand 
attenuationcurves making thus the characterization more accuratein case of damage
 assessment, repair evaluation as well as composition inspection. In this paper, threeind
icative cases of scattering influence arepresented.Namely, theinteraction of actual 
distributed damage, as well as the repair materialinjectedin an old concrete structurewith 
the wave parameters. Other cases are the influenceof light plastic inclusions inhardened 
mortarand the influence of sand and water content in the examination of freshconcrete.
 Inall the above cases, scattering seems to complicate the propagation behaviorbut also 
offers the way for a moreaccurate characterization of the quality of the material.

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