Effect of notch-depth ratio on intermittent electromagnetic radiation from Cu-Ni alloy under tension

Abstract

This paper presents some experimental results on the effect of the notch–depth ratio on intermittent electromagnetic radiation during the progressive plastic deformation of a Cu-Ni alloy sheet specimen under tension. An electromagnetic antenna was used for receiving the electromagnetic waves emitted by the deforming specimen. The specimens (with varied notch-depth ratios) first emit electromagnetic radiation near yield which is always oscillatory in nature. However, the axial strain at the initial emission of the electromagnetic radiation increases with an increase in the notch-depth ratio. The nature of electromagnetic radiation signals changes from oscillatory to exponential until instability is reached. This shows that the viscous coefficient of the material of the specimens increases during strain-hardening. The paper also presents a correlation between electromagnetic radiation emission parameters and the radius of the plastic zone created ahead of the advancing crack tip, an important parameter in fracture mechanics. With an increase in the plastic zone size, the amount of intermittent electromagnetic radiation decreases asymptotically: the first electromagnetic radiation amplitude increases linearly and a maximum energy burst first decreases the electromagnetic radiation frequency parabolically. Initial electromagnetic radiation characteristics differ considerably from optimum electromagnetic radiation emissions within the strain-hardening region. These experimental results show a novel technique for studying various fracture mechanics parameters and also for developing a non-contact crack growth monitor.

Influence of an Engineered Notch on the Electromagnetic Radiation Performance of NiTi Shape Memory Alloy

“…The failure occurs because of the influence of a stress-free boundary on the stress field surrounding the fracture tip. As a result, it is suggested that an ideal 2a/w range of 0.45 to 0.55 [19] is maintained.…”

“…Figure 3 shows the stress-strain plot depicting the stages of intermittent EMR emission for 2a/w = 0.33. The EMR signal for various metallic materials [13][14][15][16][17][18][19] exhibits exponential decaying and damped oscillating characteristics. Figure 4a shows the first EMR emission signal near yielding for 2a/w = 0.33, indicating an oscillating damping nature.…”

“…The roots p 1n and p 2n of the governing equation for dislocation motion are given by the following [19]:…”

“…Experiments using intermittent EMR in the plastic deformation of Cu-Ni alloys during tension and compression revealed that the compression viscosity coefficient increases during plastic deformation [18]. The plastic zone radius was correlated with the notch-depth ratio in tensile tests conducted on the Cu-Ni alloy [19]. Anand and Kumar's [20] review of EMR emission and the mathematical models for different metallic materials provides a solid foundation on this topic.…”

A review on deformation-induced electromagnetic radiation detection: history and current status of the technique

“…It was observed that the changes in the ratio change the nature of EMR, i.e. from oscillatory to exponential, and have also helped to develop the correlation between the EMR emission parameters and the radius of the plastic zone [184]. Recently Oraon and Sharma presented an experimental investigation to determine EMR radiation during incremental microforming of a thin aluminium sheet.…”