The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be s...The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies.展开更多
A piezoelectric accelerometer with optical fiber to measure the dynamic parameter of 3 dimensions is presented. The operation equations on X, Y and Z axes are divided, and the test results of 3 dimensional sensitiviti...A piezoelectric accelerometer with optical fiber to measure the dynamic parameter of 3 dimensions is presented. The operation equations on X, Y and Z axes are divided, and the test results of 3 dimensional sensitivities and frequency response, are given as well as experiment results of vibration test with this setup.展开更多
Glass-forming ability is a long-standing concern in the field of metallic glasses(MGs),which greatly limits their maximum casting size and extensive applications.In this work,we report an ultrasonic-assisted rapid col...Glass-forming ability is a long-standing concern in the field of metallic glasses(MGs),which greatly limits their maximum casting size and extensive applications.In this work,we report an ultrasonic-assisted rapid cold welding of bulk MGs without using any additives.MGs with various compositions are welded together under a 20,000-Hz highfrequency ultrasonic vibration without losing their amorphous nature.The ultrasonic technology offers the advantages of rapid bonding(<1 s)at low temperature(near room temperature)and low stress(<1 MPa).According to the phenomenon observed in the experiment,the activated fresh atoms diffuse through the broken channel port under continuous rupture of the oxide layer,and the ultrasonic vibration accelerates the atomic-diffusion process.Finally,stable bonding of the MG interface is realized.This universal ultrasonic-assisted welding process can realize the composition design of dissimilar MGs as well as tuning of new materials with new performance.展开更多
We focus on the hysteretic characteristics of the varying compliance(VC) principal resonance in a ball bearing. The branches of the periodic VC response are traced by the harmonic balance method and the alternating fr...We focus on the hysteretic characteristics of the varying compliance(VC) principal resonance in a ball bearing. The branches of the periodic VC response are traced by the harmonic balance method and the alternating frequency/time domain technique(HB-AFT) embedding Arc-length continuation, and the stability of these solutions is investigated by using Floquet theory. We find that the resonant response displays a swallow-tail structure due to the coupling nonlinearities between the Hertzian contact and the bearing clearance, which differs from the soft hysteresis of the non-loss Hertzian contact resonances. Furthermore, we find that period-1 VC branch cannot completely characterize the response of the system for a large bearing clearance, because multiple instability regions may occur from the cyclic fold, the secondary Hopf bifurcations, supercritical and subcritical period doubling bifurcations, in which case co-existences of period-1, period-2, and even quasi-periodic VC motions emerge in the hysteretic resonant range.展开更多
基金Supported by National Natural Science Foundation of China (No. 50978156 and No. 50908183)
文摘The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies.
文摘A piezoelectric accelerometer with optical fiber to measure the dynamic parameter of 3 dimensions is presented. The operation equations on X, Y and Z axes are divided, and the test results of 3 dimensional sensitivities and frequency response, are given as well as experiment results of vibration test with this setup.
基金supported by the Key Basic and Applied Research Program of Guangdong Province,China(2019B030302010)the National Natural Science Foundation of China(51871157,51971150 and 51775351)+2 种基金the Science and Technology Innovation Commission Shenzhen(JCYJ20170412111216258)the National Key Research and Development Program of China(2018YFA0703605)Shenzhen Basic Research Project(JCYJ20190808152409578).
文摘Glass-forming ability is a long-standing concern in the field of metallic glasses(MGs),which greatly limits their maximum casting size and extensive applications.In this work,we report an ultrasonic-assisted rapid cold welding of bulk MGs without using any additives.MGs with various compositions are welded together under a 20,000-Hz highfrequency ultrasonic vibration without losing their amorphous nature.The ultrasonic technology offers the advantages of rapid bonding(<1 s)at low temperature(near room temperature)and low stress(<1 MPa).According to the phenomenon observed in the experiment,the activated fresh atoms diffuse through the broken channel port under continuous rupture of the oxide layer,and the ultrasonic vibration accelerates the atomic-diffusion process.Finally,stable bonding of the MG interface is realized.This universal ultrasonic-assisted welding process can realize the composition design of dissimilar MGs as well as tuning of new materials with new performance.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2015CB057400)the China Postdoctoral Science Foundation(Grant No.2013M541360)the National Natural Science Foundation of China(Grant Nos.10632040 and 11302058)
文摘We focus on the hysteretic characteristics of the varying compliance(VC) principal resonance in a ball bearing. The branches of the periodic VC response are traced by the harmonic balance method and the alternating frequency/time domain technique(HB-AFT) embedding Arc-length continuation, and the stability of these solutions is investigated by using Floquet theory. We find that the resonant response displays a swallow-tail structure due to the coupling nonlinearities between the Hertzian contact and the bearing clearance, which differs from the soft hysteresis of the non-loss Hertzian contact resonances. Furthermore, we find that period-1 VC branch cannot completely characterize the response of the system for a large bearing clearance, because multiple instability regions may occur from the cyclic fold, the secondary Hopf bifurcations, supercritical and subcritical period doubling bifurcations, in which case co-existences of period-1, period-2, and even quasi-periodic VC motions emerge in the hysteretic resonant range.
