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1. chinaXiv:201902.00003 [pdf]

Magnetic field-dependent reversal effect of the electromagnet- induced normal stress of magnetorheological materials

Taixiang Liu; Yangguang Xu; Ke Yang; Lianghong Yan; Beicong Huang; Zhuo Zhang; Xiaodong Jiang; Hongwei Yan
Subjects: Materials Science >> Materials Mechanics

Magnetorheological (MR) materials are a type of magnetoactive smart materials, whose physical or mechanical properties can be altered by applying a magnetic field. In usual, MR materials can be prepared by mixing magnetic particles into non-magnetic matrices. In this work, the electromagnet-induced (or non-uniform magnetic field-induced) normal stress of MR materials is studied. It shows that the stress does not vary monotonically along with the enhancement of the applied magnetic field. There exists a field-dependent reversal effect of the variation of the stress. The reversal effect is thought resulting from that the ratio of interparticle repellent of parallel magnetic particles to the particle-electromagnet attraction gets enlarged along with the enhancement of the field.

submitted time 2019-02-01 Hits31947Downloads2301 Comment 0

2. chinaXiv:201810.00123 [pdf]

Hydrofluoric acid-based etching effect on the surface pit, crack, scratch, and laser damage site of fused silica optics

Taixiang Liu; Ke Yang; Zhuo Zhang; Lianghong Yan; Beicong Huang; Heyang Li; Chuanchao Zhang; Xiaodong Jiang; Hongwei Yan
Subjects: Chemistry >> Chemical Physics

Large-scale, high-power laser facility is currently a basis for the research of inertial confinement fusion (ICF). In the laser facility, fused silica optics plays irreplaceable role to conduct extremely high-intensity ultraviolet laser to fusion target. However, the surface fractures, such as surface pit, crack, scratch, and laser damage site, of the optics will lower the beam quality of transmitted laser, weaken the laser damage-resistance, shorten the lifetime of the optics, and thus limit the output performance of the laser facility. In this work, to mitigate the surface fractures, hydrofluoric acid-based (HF-based) etching effect on the surface fractures is experimentally and theoretically studied. From the experimental study, with the result of three-dimensional (3D) morphological evolution of surface fractures, it is shown that the surface fractures will be passivated and their profiles will get smoothed after etching, indicating HF-based etching is a promising way to improve the local surface quality of the fractures. Especially, it is found HF-based etching can greatly suppress the laser damage growth of laser damage site by mitigating its surface and subsurface fractures, and thus is a promising wet chemical method for repairing laser-induced damage optics. In the theoretical study, an explicit local-curvature dependent etching model is proposed. Based on this model, the result from finite difference time domain (FDTD) simulation agrees very well with that of experiment, which can reveal the detailed physical process of HF-based etching. It is demonstrated that the FDTD simulation can be a reliable and efficient way to predict the morphological evolution of the surface fractures during etching.

submitted time 2018-11-28 Hits4875Downloads2217 Comment 0

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