An Insight into Amorphous Shear Band in Magnetorheological Solid by Atomic Force Microscope

Abstract

Micro mechanism consideration is critical for gaining a thorough understanding of amorphous shear band behavior in magnetorheological (MR) solids, particularly those with viscoelastic matrices. Heretofore, the characteristics of shear bands in terms of formation, physical evolution, and response to stress distribution at the localized region have gone largely unnoticed and unexplored. Notwithstanding these limitations, atomic force microscopy (AFM) has been used to explore the nature of shear band deformation in MR materials during stress relaxation. Stress relaxation at a constant low strain of 0.01% and an oscillatory shear of defined test duration played a major role in the creation of the shear band. In this analysis, the localized area of the study defined shear bands as varying in size and dominantly deformed in the matrix with no evidence of inhibition by embedded carbonyl iron particles (CIPs). The association between the shear band and the adjacent zone was further studied using in-phase imaging of AFM tapping mode and demonstrated the presence of localized affected zone around the shear band. Taken together, the results provide important insights into the proposed shear band deformation zone (SBDZ). This study sheds a contemporary light on the contentious issue of amorphous shear band deformation behavior and makes several contributions to the current literature.

Morphological Effects of Strain Localization in the Elastic Region of Magnetorheological Elastomers

“…Figure 3 shows the condition of the MRE sample after the durability evaluation, particularly after the 115,000-cycle test duration established previously in a related study [ 21 ]. Following the durability performance evaluation, a preliminary observation of the cut MRE micrography using FESEM, in general, revealed more intriguing morphology, reflecting the MRE’s narrower dimensions and less volumetrically suffered area than previously reported [ 21 ].…”

“…Figure 3 shows the condition of the MRE sample after the durability evaluation, particularly after the 115,000-cycle test duration established previously in a related study [ 21 ]. Following the durability performance evaluation, a preliminary observation of the cut MRE micrography using FESEM, in general, revealed more intriguing morphology, reflecting the MRE’s narrower dimensions and less volumetrically suffered area than previously reported [ 21 ]. The cut area was chosen based on the torsional shear mathematical theory, which states that a sample’s shear center point is not precipitated by any torsional deformation (imaginary point); the torsional deformation was then compared to the shearing acting on the sample’s edge, which contributed to the greatest angular displacement.…”

“…Based on previously published results [ 4 , 8 , 17 , 28 ], the application of a 0.1 wt% curing agent, the ready mixture of 30 wt% matrices, and 70 wt% CIPs were chosen for this study. Finally, a circular disc sample of the MRE was punched out using a hollow-hole punch tool from the original prepared MRE disc sheet to the required diameter of 20 mm and nominal thickness of 1 mm, and it had a 20% less surface-to-volume ratio than that in the previous related study [ 21 ].…”

“…This is the main technical contribution of this work. An evaluation is performed on a much narrower area of an MRE sample than that previously reported [ 21 ] to make a comparison of the surface-to-volume ratio. Concomitantly, a field-emission scanning electron microscope (FESEM) and an atomic force microscope (AFM) are used in this study to investigate stress relaxation and strain localization phenomena in MRE.…”