scholarly journals Electromagnetically excited acoustic resonance for evaluating attenuation coefficient and grain size in polycrystalline metals

1994 ◽  
Vol 64 (17) ◽  
pp. 2217-2219 ◽  
Author(s):  
M. Hirao ◽  
H. Ogi
Keyword(s):  
Grain Size ◽  
Attenuation Coefficient ◽  
Acoustic Resonance ◽  
Polycrystalline Metals

scholarly journals Relation between Sub-grain Size and Dislocation Density During Steady-State Dislocation Creep of Polycrystalline Cubic Metals

2018 ◽  
Vol 7 (4) ◽  
pp. 26 ◽  
Author(s):  
Manabu Tamura
Keyword(s):  
Grain Size ◽  
Steady State ◽  
Dislocation Density ◽  
Martensitic Steel ◽  
Empirical Relation ◽  
Dislocation Creep ◽  
Theoretical Relation ◽  
Cross Sectional ◽  
Cubic Metals ◽  
Polycrystalline Metals

The sub-grain size, d, during steady-state dislocation creep of polycrystalline metals is theoretically formulated to be inversely proportional to the dislocation density, ρ, which is defined as the number of dislocations swept out of a sub-grain divided by the cross-sectional area of the sub-grain. This dislocation density differs from the typically observed dislocation density inside a sub-grain after unloading, ρ_ob. In the current work, the ρ_ob values inside sub-grains in steadily crept specimens of Al, Cu, Fe, Fe–Mo alloy, austenitic stainless steel, and high-Cr martensitic steel reported in the literature were used to evaluate the relation ρ_ob=ηρ. It was confirmed that η≈1 for pure metals (regardless of the type of metal) crept at high temperatures and low stresses or for long durations and η>1 for Mo-containing alloys and martensitic steel crept at low temperatures and/or high stresses. Moreover, it is suggested that the condition η>1 corresponds to a state of excess immobile dislocations inside the sub-grain. The theoretical relation d_ob (≈d)∝η∙〖ρ_ob〗^(-1), where d_ob is the observed sub-grain size, essentially differs from the well-known empirical relation d_ob∝〖ρ_ob〗^(-0.5).

Measurement of Adhesive Bonding Strength With an EMAT in the Resonant Mode

2019 ◽  
Vol 2 (4) ◽  
Author(s):  
Tianhao Liu ◽  
Haiqiang Zhou ◽  
Cuixiang Pei ◽  
Zhenmao Chen
Keyword(s):  
Attenuation Coefficient ◽  
Bonding Strength ◽  
Adhesive Bonding ◽  
Signal To Noise Ratio ◽  
Plate Thickness ◽  
Acoustic Resonance ◽  
Resonant Mode ◽  
Imperfect Interface ◽  
Electromagnetic Acoustic Transducer ◽  
Strength Evaluation

Abstract The electromagnetic acoustic resonance (EMAR) method with shear wave is sensitive to boundary conditions and plate thickness. In this paper, a new noncontact ultrasonic testing method based on the electromagnetic acoustic transducer (EMAT) in the resonant mode is proposed for the bonding strength evaluation in metal-based adhesive structures. Different from the conventional pulse-echo method using short-burst excitation for bonding inspection, the attenuation coefficient feature of the resonant ultrasonic signal with long-burst excitation is applied to increase the signal-to-noise ratio (SNR) and detecting sensitivity of the EMAT for adhesive bonding strength evaluation. A theoretical model for adhesive bonding testing with EMAT signals in the resonant mode is established. To extract the signal feature representing the reflection coefficient, the time-domain signal was processed by Hilbert transformation and exponential curve fitting. Through the simulation on the received signal, the correlation between the attenuation coefficient of the exponent fitted curve and the strength on the adhesive imperfect interface were confirmed. Finally, the proposed correlation is verified by an experiment on stainless steel plates bonded with polymethyl methacrylate plates by epoxy adhesion via a permanent magnetic EMAT.

Deformation Twinning During Impact of a Titanium Cylinder: Numerical Investigation

2000 ◽  
Author(s):  
I. Lapczyk ◽  
K. R. Rajagopal ◽  
A. R. Srinivasa
Keyword(s):  
Grain Size ◽  
Major Effect ◽  
Deformation Twinning ◽  
Galerkin Finite Element Method ◽  
Galerkin Finite Element ◽  
Grain Sizes ◽  
Polycrystalline Metals ◽  
Taylor Impact ◽  
Inelastic Processes ◽  
Titanium Specimen

Abstract It is well known that polycrystalline metals (especially those with bcc or hcp structures), when subjected to impact, undergo two inelastic processes — slip and twinning. Since the work of Taylor (1948) the former one has been studied extensively; while more recently, deformation twinning has attracted attention of some researchers, e.g. Bolling & Richman (1965), Armstrong & Worthington (1974) and Zerilli & Armstrong (1988). Zerilli and Armstrong (1988) suggested that the major effect of twinning is a refinement of the grain size. Based on this assumption, they proposed a model for twinning and showed that much better agreement with experiments can be obtained if, in addition to deformation by slip, deformation twinning is also considered. Similar conclusions were reached by Holt, Mock, Zerilli and Clark (1994) who analyzed the Taylor impact of a titanium specimen. In this study, we model the Taylor impact of a titanium cylinder. We assume that the problem is axisymmetric and solve the full dynamic equations by using the Galerkin finite element method. Our results show that the energy absorbed during twinning and the deformation due to twinning are relatively small. We also demonstrate the dependence of the results on the initial grain size of the material. Specifically, by modeling two materials of widely differing grain sizes, we show that the long-grained material twins substantially more than the small-grained material.

Evaluation of mean grain size using the multi-scale ultrasonic attenuation coefficient

2015 ◽  
Vol 72 ◽  
pp. 25-32 ◽  
Author(s):  
Xiongbing Li ◽  
Yongfeng Song ◽  
Feng Liu ◽  
Hongwei Hu ◽  
Peijun Ni
Keyword(s):  
Grain Size ◽  
Attenuation Coefficient ◽  
Ultrasonic Attenuation ◽  
Multi Scale ◽  
Mean Grain Size

Application of the acoustic resonance method to evaluate the grain size of low carbon steels

1999 ◽  
Vol 32 (2) ◽  
pp. 85-89 ◽  
Author(s):  
Bongyoung Ahn ◽  
Seung Seok Lee ◽  
Soon Taik Hong ◽  
Ho Chul Kim ◽  
Suk-Joong L. Kang
Keyword(s):  
Grain Size ◽  
Resonance Method ◽  
Acoustic Resonance ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels

scholarly journals Characterization of Grain Size in 316L Stainless Steel Using the Attenuation of Rayleigh Wave Measured by Air-Coupled Transducer

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1901
Author(s):  
Meng Wang ◽  
Yangguang Bu ◽  
Zhaojie Dai ◽  
Shengyang Zeng
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Rayleigh Wave ◽  
Longitudinal Wave ◽  
Attenuation Coefficient ◽  
Rayleigh Waves ◽  
316L Stainless Steel ◽  
Wave Attenuation ◽  
Heat Treated ◽  
Comparison Results

Grain size is an important parameter in evaluating the properties of microstructures in metals. In this paper, the attenuation coefficient of Rayleigh waves is introduced to characterize grain size in heat treated 316L stainless steel. Rayleigh wave attenuation is measured using an angle beam wedge transducer as the transmitter and an air-coupled transducer as the receiver. The results show that the grain size in 316L stainless steel increases due to heat treatment time, the hardness decreases accordingly, and the attenuation coefficient of Rayleigh waves increases. This indicates that the Rayleigh wave attenuation is sufficient in distinguishing the changes in the properties of the heat-treated stainless steel. It is found that compared with the measurement method using an angle beam wedge receiver, the measured results are efficient, more stable and less influenced by the surface state when an air-coupled receiver is used. In addition, comparison results also show that the Rayleigh wave attenuation is more sensitive to changes in material properties than the longitudinal wave attenuation, as the wavelength of the Rayleigh wave is shorter than that of the longitudinal wave at the same frequency.

Sign in / Sign up

Export Citation Format

Share Document