An analytical method for assessing the initiation and interaction of cracks in fused silica subjected to contact sliding

Understanding the fracture behavior of fused silica in contact sliding is important to the fabrication of damage-free optics.This study develops an analytical method to characterize the stress field in fused silica under contact sliding by extending the embedded center of dilation(ECD)model and considering the depth of yield region.The effects of densification on the stress fields were considered by scratch volume analysis and finite element analysis.Key mechanisms,such as crack initiation and morphology evolution were comprehensively investigated by analyzing the predicted stress fields and principal stress trajectories.The predictions were validated by Berkovich scratching experiment.It was found that partial conical,median and lateral cracks could emerge in the loading stage of the contact sliding,but radial and lateral cracks could be initiated during unloading.It was also found that the partial conical crack had the lowest initiation load.The intersection of long lateral cracks makes the material removal greater.

Vector analysis of electric-field-induced antiparallel magnetic domain evolution in ferromagnetic/ferroelectric heterostructures

Electric field(E-field)control of magnetism based on magnetoelectric coupling is one of the promising approaches for manipulating the magnetization with low power consumption.The evolution of magnetic domains under in-situ E-fields is significant for the practical applications in integrated micro/nano devices.Here,we report the vector analysis of the E-field-driven antiparallel magnetic domain evolution in FeCoSiB/PMN-PT(011)multiferroic heterostructures via in-situ quantitative magneto-optical Kerr microscope.It is demonstrated that the magnetic domains can be switched to both the 0°and 180°easy directions at the same time by E-fields,resulting in antiparallel magnetization distribution in ferromagnetic/ferroelectric heterostructures.This antiparallel magnetic domain evolution is attributed to energy minimization with the uniaxial strains by E-fields which can induce the rotation of domains no more than 90°.Moreover,domains can be driven along only one or both easy axis directions by reasonably selecting the initial magnetic domain distribution.The vector analysis of magnetic domain evolution can provide visual insights into the strain-mediated magnetoelectric effect,and promote the fundamental understanding of electrical regulation of magnetism.

A trapezoidal cantilever density sensor based on MEMS technology

A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems （MEMS） technology. The sensor measures fluid density through the relationship between the density and the resonant frequency of the cantilever im-mersed in the fluid. To improve the sensitivity of the sensor, the modal and harmonic response analyses of trapezoidal and rec-tangular cantilevers are simulated by ANSYS software. The higher the resonant frequency of the cantilever immersed in the fluid, the higher the sensitivity of the sensor; the higher the resonant strain value, the easier the detection of the output signal of the sensor. Based on the results of simulation, the trapezoidal cantilever is selected to measure the densities of dimethyl silicone and toluene at the temperature ranges of 30 to 55 ℃ and 26 cantilever density sensor has a good performance. to 34 ℃, respectively. Experimental results show that the trapezoidal cantilever density sensor has a good pertbrmance.