Surface layer measurements of early age mortar investigated by ultrasonic guided waves and finite element analysis

2008 ◽  
Author(s):  
Jacob L. Borgerson ◽  
Henrique Reis
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Surface Layer ◽  
Guided Waves ◽  
Ultrasonic Guided Waves ◽  
Early Age ◽  
Element Analysis

scholarly journals Shear-Actuation and Vibrometer Reception of Penetrating Ultrasonic Guided Wave Modes in Human Tibia

2020 ◽  
Vol 10 (23) ◽  
pp. 8397
Author(s):  
Anurup Guha ◽  
Michael Aynardi ◽  
Parisa Shokouhi ◽  
Cliff J. Lissenden
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Phase Velocity ◽  
Time Domain ◽  
Guided Waves ◽  
Ultrasonic Guided Waves ◽  
Appendicular Skeleton ◽  
Element Analysis ◽  
Human Tibia ◽  
Wave Modes

The hollow long bones of the human appendicular skeleton are known to support the propagation of ultrasonic guided waves, whose potential for diagnosing bone health is being investigated. In this study, ultrasonic guided waves propagating in the diaphysis of human tibia are characterized experimentally and numerically in the frequency range around 200 kHz. The experiment involves a unique combination of omni-directional shear transducer-based excitation and detection using a 1D laser Doppler vibrometer. The cluster of phase velocities obtained from a linear array of time-history data using space-time Fourier transform is found to be in the non-dispersive low-phase velocity region of the dispersion curves obtained for a tibial cross-section. Time-domain finite element analysis revealed that the displacement components normal to the surface are significant, even though the loading is from a shear transducer. Furthermore, semi-analytical finite element analysis revealed that the wave structures of the wave modes contained within the cluster of low-phase velocity modes are consistent with the displacement profiles obtained from the time-domain analysis. The experimental results show that the low-phase velocity mode cluster has sufficient intensity to propagate axially at least 85 mm in the mid-diaphyseal region.

Finite-Element Modeling and Analysis of Early-Age Cracking Risk of Cast-In-Place Concrete Culverts

2018 ◽  
Vol 2672 (27) ◽  
pp. 24-36 ◽  
Author(s):  
Yalin Liu ◽  
Anton K. Schindler ◽  
James S. Davidson
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Expansion ◽  
Lightweight Concrete ◽  
Coefficient Of Thermal Expansion ◽  
Early Age ◽  
Thermal Coefficient ◽  
Element Analysis ◽  
Joint Spacing ◽  
Cracking Risk

Extensive cracking was found in several cast-in-place concrete culverts in Alabama. This condition can decrease the long-term durability of the culverts. Early-age stress development in concrete is influenced by temperature changes, modulus of elasticity, stress relaxation, shrinkage, thermal coefficient of expansion, and the degree of restraint. The objective of this study is to determine means to mitigate early-age cracking in culverts by evaluating the cracking risk. Finite-element analysis was used to model the early-age stress by accounting for the following factors: construction sequencing, support restraint, concrete constituents, temperature effects, and the time-dependent development of mechanical properties, creep/relaxation, and drying shrinkage. Experimental results from restraint to volume change tests with rigid cracking frames were used to verify the accuracy of the finite-element analysis. A parametric study was performed to quantify the effect of changing joint spacing, joint type, construction sequence, concrete coefficient of thermal expansion, placement season, and concrete type on the risk of early-age cracking. The finite-element model results revealed that the use of the following measures will reduce the risk of early-age cracking in cast-in-place concrete culverts: concrete with lower coefficient of thermal expansion, contraction joints, sand-lightweight concrete or all-lightweight concrete, and scheduling the casting of the culvert wall to minimize the difference in its placement time relative to its previously cast base. Alternatively, to minimize the contribution of thermal effects on risk of cracking, the construction schedule should be developed to avoid concrete placement during hot weather conditions.

Finite element analysis of concrete cracking at early age

2011 ◽  
Vol 37 (5) ◽  
pp. 459-473 ◽  
Author(s):  
Mauren Aurich ◽  
Americo Campos Filho ◽  
Tulio Nogueira Bittencourt ◽  
Surendra P. Shah
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Early Age ◽  
Element Analysis ◽  
Concrete Cracking

Finite element analysis of guided waves in fluid-filled corrugated pipes

2007 ◽  
Vol 121 (3) ◽  
pp. 1313-1323 ◽  
Author(s):  
Matthias Maess ◽  
Jan Herrmann ◽  
Lothar Gaul
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Guided Waves ◽  
Element Analysis
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