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Investigation on tool wear process of milling wave-transmitting Si <sub/>3</sub> N <sub/>4</sub> ceramics
摘要： Due to the low fracture toughness of wave-transmitting Si3N4 ceramics, the special material removal mechanism causes the tool wear to be different. The paper presents the tool wear forms and mechanism under different milling depth. The effect of tool wear on cutting force and machined surface morphology is discussed. Tests have been performed under typical conditions of cutting depth of 0.3 mm (in plastic-domain processing) and 0.4 mm (in brittle-domain processing). The results show that the abrasive wear caused by the chips is the main mechanism of the cutting edge wear and the flank wear, the increase of the side edge rear angle with tool wear is the main cause of the chipping phenomenon. The cutting depth is a significant influence parameter to the wear characteristics, and two types have been distinguished. As the material removal volume ascending, the cutting edge wear and the flank face wear has a stable period, and the root-mean-square deviation of processing surface increases to 1.6 μm, while that increase with the material removal volume continuously, and the processing surface decreases to 1.4 μm. It has been proved that the cutting force tends to increase first and then decrease as the material removal volume is about 4320 mm3.
关键词： ceramics,milling,morphology,plastic-domain,chipps,wear,Tool,brittle-domain,surface
更新于2025-09-23 15:23:52
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Modeling the Compressive Behavior of Anisotropic, Nanometer-Scale Structured Silica
摘要： Recently, large plastic deformations were observed during compression testing of biotemplated, anisotropic, and hierarchically structured silica monoliths. Based on the material’s nanometer-scale structuring, a dynamic model is devised in which parallel silica struts are compressed, and sheared in longitudinal direction. The resulting interfacial shear forces lead to successive plastic deformations during cyclic loading with incrementally increasing forces, matching observations by mechanical testing. The authors report on the physical parameter values obtained from fitting model curves to measured ones, their relation to prior structural observations, and their utility to tailor the intricate mechanical behavior of this novel material.
关键词： simulation,deformation,dynamic,fracture,nanoscale,silica,brittle
更新于2025-09-23 15:22:29
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Laser additive manufacturing of bimetallic structure from Ti-6Al-4V to Ti-48Al-2Cr-2Nb via vanadium interlayer
摘要： As a potential candidate material, Ti6Al4V (TC4) / Ti48Al2Cr2Nb (TiAl) bimetallic structure (BS) material has a good development prospects in the field of aerospace engineering, and has a broad application prospects for the integrated manufacture of aero-engine turbine blades (TiAl) and turbine disks (TC4). However, via the direct bonding of TC4/TiAl BS, it is easy to produce brittle intermetallic compounds which increases the crack sensitivity. Therefore, to a certain extent, the application of TC4/TiAl BS is limited. In this study, we use laser additive manufacturing (LAM) technology to prepare the TC4 / TiAl BS via a V interlayer, which further limits the formation of a brittle phase. The experimental results show that the V interlayer can effectively limit the formation of the brittle phase (Ti3Al), which reduces the crack sensitivity of the formed parts, and forms a good metallurgical joint at the TC4/TiAl BS interfaces. Results of room temperature tensile tests reveal that the tensile strength and elongation of the BS specimens are ~476 MPa, and ~2.8% respectively , which means that the strength of the joint exceeded that of the deposited TiAl alloy without the V interlayer.
关键词： Microstructure,Brittle phases,Ti/TiAl bimetallic structure,Tensile strength,Interfaces,Laser additive manufacturing
更新于2025-09-12 10:27:22
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A review on glass welding by ultra-short laser pulses
摘要： Glass welding by ultra-short pulsed lasers is a piece of technology that offers high strength joints with hermetic sealing. The joints are typically formed in glass that is transparent to the laser by exploiting nonlinear absorption effects that occur under extreme conditions. Though the temperature reached during the process is on the order of a few 1000 °C, the heat affected zone (HAZ) is confined to only tens of micrometers. It is this controlled confinement of the HAZ during the joining process that makes this technology so appealing to a multitude of applications because it allows the foregoing of a subsequent tempering step that is typically essential in other glass joining techniques, thus making it possible to effectively join highly heat sensitive components. In this work we give an overview on the process, development and applications of glass welding by ultra-short pulsed lasers.
关键词： ultra-short pulsed laser processing,glass joining,USP glass welding,brittle materials
更新于2025-09-11 14:15:04
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Effects of crystallographic orientation and negative rake angle on the brittle-ductile transition and subsurface deformation in machining of monocrystalline germanium
摘要： In this study, taper cutting experiments using a diamond tool were conducted to investigate the effects of negative rake angle and cutting orientation on the brittle-ductile transition and subsurface deformation of monocrystalline germanium cut on the (100), (101), and (111) planes. Confocal laser scanning microscopy and Raman spectroscopy were used to observe the three-dimensional surface topographies of the samples and characterize the subsurface deformation, respectively. The results showed that the negative rake angle and crystallographic orientation have a significant effect on the brittle-ductile transition and subsurface deformation mechanisms in ductile regime machining of monocrystalline germanium. A large negative rake angle alters the initial surface crack patterns, as well as anisotropic behavior of the ductile-brittle transition and subsurface deformation of monocrystalline germanium.
关键词： brittle-ductile transition,negative rake angle,crystallographic orientation,subsurface deformation,Germanium
更新于2025-09-10 09:29:36
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On-the-Fly Fast X-Ray Tomography Using a CdTe Pixelated Detector – Application in Mechanical Testing
摘要： Fast tomography measurements are still done almost exclusively within the domain of synchrotrons. However, recent progress in X-ray imaging instrumentation has enabled researchers to perform time-lapse computed tomography (4D-CT) even under laboratory conditions with standard X-Ray sources. Thus, fast time-dependent processes within materials with relatively high X-Ray attenuation can be monitored. The article describes the in-situ tomographic monitoring of crack formation and propagation in a quasi-brittle silicate matrix composite subjected to three point bending. A three-dimensional CT volume containing the region of interest (ROI) in the specimen is imaged over a period of time while the continuously increasing load causes crack initiation and propagation, creating a dynamic volume dataset. An acquisition time of 50 seconds for one full angle tomography with 400 projections makes this tomographic system one of the fastest systems in the world. The resulting visualizations provide qualitative information concerning progressive crack propagation within areas of lower material density. Differential images then allow displaying the spatial orientation of the crack over time. The results were further processed for a quantitative analysis of image quality using various methods of beam hardening correction.
关键词： X-ray imaging techniques,X-ray tomography,Materials characterization,Mechanical testing,Quasi-brittle material,Fracture mechanics,CdTe detectors
更新于2025-09-10 09:29:36
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Ductile behavior of optical glass in single point diamond turning
摘要： Single point diamond turning tests were carried out on a B270 type glass. Sub-micrometer cutting conditions were applied in order to generate ductile response during single point machining. The profile generated by the rapid removal of the tool tip from the machined surface, analyzed by atomic force microscopy, showed that the brittle-to-ductile transition occurs at a few tenths of micrometers. According to the machining results, the maximum feed rate capable of generating a ductile mode machining behavior is of 0.9 micrometer/revolution. Furthermore, it was shown that with the cutting depth lower than 0.100 micrometer/revolution, the material removal mechanism is totally ductile. Ribbon-like chips were not observed when ductile machining was performed, as commonly seen during ductile machining of semiconductor crystals. The chips removed had a small needle-like shape. This material’s fragile behavior during machining may be related to high densification during tool/material interaction with subsequent elastic recovery response.
关键词： soda-cal-silicates,Atomic Force Microscope,Brittle-to-ductile transition,diamond turning
更新于2025-09-09 09:28:46