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Study on mechanism of crack propagation of sapphire single crystals of four different orientations under impact load and static load
摘要： Sapphire has a wide range of applications due to its excellent physical properties. Sapphire is a typical anisotropic material, whose parts are usually employed in the complex conditions, including static and dynamic load. The mechanism of crack propagation under different loading conditions has important significance for successful application of sapphire. In this study, impact and static load tests have been performed on the A-plane, C-plane, M-plane and R-plane of sapphire by the high frequency cyclic impact test device, respectively. The force signals applied to sapphire have been obtained under different test conditions. The crack propagation has been analyzed based on the fracture morphology of specimen. It is found that sapphire will quickly crack and break under impact load, and then enter the fatigue stage. In the static load indentation tests, the force applied to sapphire seems to increase linearly with the linear increase of load, but this relationship is not yet linear in the unloading procedure. The crack propagation is affected by the crystal orientation, which leads to different characteristics of the surface morphology of the different crystal orientations sapphire after fracture. So four different models of crack system are proposed for A-plane, C-plane, M-plane and R-plane respectively. In addition, the three-dimensional morphology of sapphire is observed by a white-light interferometer. It seems that the Hertzian cone crack occurs only on the R-plane sapphire after impact load, but it cannot be sure whether the cone crack occurs when impacting A-, C-, and M-planes sapphire.
关键词： Impact load,Static load,Sapphire,Crystal orientations,Crack propagation,Crack system
更新于2025-09-23 15:23:52
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White light interferometry and MountainsMap? - case studies in static load capacity of bearings and surface finish optimisation of orthotic knee joints
摘要： This paper deals with two case studies demonstrating the combined use of white light interferometry and MountainsMap? software to: 1) accurately measure indentation diameters on race elements with an accuracy of a 1/100th of a micrometer and to examine static load capacity of bearings compared to the industry standard. In this case study, static load capacity of the ball bearings was shown to be 31% lower than that specified by ISO and ANSI/ABMA bearing standards; 2) characterise machined surfaces with 2D and 3D parameters, with the goal of producing optimal surface finish on orthotic knee joints used by Cerebral Palsy patients. In this case study, 2D roughness parameters Ra, Rq, Rp, Rz, and 3D roughness parameters Sa, Sq, Sp, Sz, were improved by 34%, 31%, 8%, 20%, and 36%, 33%, 6%, 6% respectively. Both case studies demonstrate the significance of modern topography techniques in enhancing the measurement accuracy of surface characteristics.
关键词： robust design,MountainsMap?,surface roughness,signal-to-noise (S/N) ratio,interferometry,WLI,static load capacity,white light,ball bearing indentations
更新于2025-09-23 15:22:29
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On the problem of laser error correction of multi-axis influence of loading on laser accuracy correction of multi-axis systems
摘要： The paper considers a method of error correction for numeric-controlled multi-axis systems (such as machine-tools or CMMs). The paper adds influence of static load research to previous author’s papers. The paper features loaded and unloaded machine`s error correction results. The migration of “zero point” described in previous papers is considered.
关键词： static load,laser error correction,volumetric accuracy,multi-axis systems
更新于2025-09-23 15:19:57
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Spectral Properties of Magnetohydrodynamic Turbulence Revealed by Polarization Synchrotron Emission with Faraday Rotation
摘要： Sensors of stress or strain currently used in geotechnical and civil engineering applications have the disadvantage that a large quantity of measuring points would result in large bundles of cables. Based on the principle of resistive strain gauge, a type of smart sensor that supports serial communication over RS-485 is developed for the measurement of strain or stress of foundation piles, which has the benefit of good noise tolerance. All the sensors installed along a pile could share a common cable for power supply and communication, and there is no actual limits to pile length. The installation in the field is simple, convenient and efficient. The sensor has a compact structure with reliable waterproof protection. The internal measurement circuit mainly consists of a Wheatstone bridge excitation module, a signal conditioning module, a microcontroller with ADC, a precision voltage reference, and a RS-485 communication module. A group of sensors were calibrated after being assembled, and the calibration results obtained have shown their functionality and reliability.
关键词： smart sensor,axial strain sensor,static load testing,RS-485 communication,foundation piles
更新于2025-09-11 14:15:04