The elastic properties of single-crystalline ω (hexagonal) phase of titanium are studied. Understanding the elastic properties is important for the development of biomedical titanium alloys with a ...low Young’s modulus. However, the elastic properties of the ω phase have remained unclear because of the difficulty in preparing a large single crystal consisting of a single phase of the ω phase, even though the ω phase has been believed to exhibit a higher elastic modulus than the β (body-centered cubic) phase. In this work, pure titanium was severely deformed by high-pressure torsion processing, to obtain polycrystalline specimens consisting exclusively of the ω phase, which is metastable at room temperature. For the ω-phase polycrystal, the complete set of elastic stiffness components was measured by RUS combined with laser Doppler interferometery. By analyzing the elastic stiffness of the ω-phase polycrystal on the basis of an inverse Voigt–Reuss–Hill approximation, the elastic stiffness components of the single-crystalline ω phase were determined. The Young’s modulus of the ω phase along 〈0001〉 was found to be clearly higher than that along 〈112¯0〉, and the shear modulus also exhibited anisotropy. Importantly, the Young’s modulus and shear modulus of the metastable ω phase were higher than those of the β phase and also higher than those of the α (hexagonal close-packed) phase, which is stable at room temperature. Furthermore, analysis by a micromechanics model using the determined elastic stiffness deduced the effect of ω phase formation on the elastic properties of β-phase titanium alloys.
We developed a pitch-catch system based on electromagnetic acoustic transducers (EMATs) for pipe inspection, which moves inside the pipe in the axial direction. The first higher mode, T(0,2), of the ...torsional guided wave is transmitted and detected, and variations of amplitude and phase are measured while moving the EMATs. Several aluminum pipes containing dish-shaped defects are inspected, and the amplitude and phase show enough detection sensitivity. It is found that the phase measurement has better potential as a tool for quantitative inspection. The applicability of the technique for steel pipe is also confirmed.
A very typical and important application of Electromagnetic Acoustic Transducers (EMATs) is the inspection of ferritic steels with normal bias field transducers. In this case, a controversy has ...arisen in the literature, as some older studies have indicated the Lorentz force as the main transduction mechanism, while more recent research has claimed that magnetostriction can be two order or magnitudes larger than the Lorentz effect. This is not merely an academic issue, as depending on which physical phenomena dominates, the performance of EMATs on different steel grades might significantly vary and the design of the transducer could be optimized accordingly.
This paper analyzes in depth two main assumptions made in the more recent studies, highlighting some inconsistencies. A previously experimentally validated Finite Element model, is used to test the controversial assumptions. It is demonstrated that the mechanical boundary conditions were not modelled correctly leading to a gross overestimation of the role of magnetostriction. The main conclusion is that the magnetostriction force is typically not order of magnitudes larger than the Lorentz force; actually the Lorentz force is the larger transduction effect in non-oxidized ferromagnetic steels, and magnetostriction is only a fraction of it.
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