Workpiece rotational grinding is widely used in the ultra-precision machining of hard and brittle semiconductor materials,including single-crystal silicon,silicon carbide,and gallium arsenide.Surface roughness and sub...Workpiece rotational grinding is widely used in the ultra-precision machining of hard and brittle semiconductor materials,including single-crystal silicon,silicon carbide,and gallium arsenide.Surface roughness and subsurface damage depth(SDD)are crucial indicators for evaluating the surface quality of these materials after grinding.Existing prediction models lack general applicability and do not accurately account for the complex material behavior under grinding conditions.This paper introduces novel models for predicting both surface roughness and SDD in hard and brittle semiconductor materials.The surface roughness model uniquely incorporates the material’s elastic recovery properties,revealing the significant impact of these properties on prediction accuracy.The SDD model is distinguished by its analysis of the interactions between abrasive grits and the workpiece,as well as the mechanisms governing stress-induced damage evolution.The surface roughness model and SDD model both establish a stable relationship with the grit depth of cut(GDC).Additionally,we have developed an analytical relationship between the GDC and grinding process parameters.This,in turn,enables the establishment of an analytical framework for predicting surface roughness and SDD based on grinding process parameters,which cannot be achieved by previous models.The models were validated through systematic experiments on three different semiconductor materials,demonstrating excellent agreement with experimental data,with prediction errors of 6.3%for surface roughness and6.9%for SDD.Additionally,this study identifies variations in elastic recovery and material plasticity as critical factors influencing surface roughness and SDD across different materials.These findings significantly advance the accuracy of predictive models and broaden their applicability for grinding hard and brittle semiconductor materials.展开更多
Nanogrinding of SiC wafers with high flatness and low subsurface damage was proposed and nanogrinding experiments were carried out on an ultra precision grinding machine with fine diamond wheels. Experimental results ...Nanogrinding of SiC wafers with high flatness and low subsurface damage was proposed and nanogrinding experiments were carried out on an ultra precision grinding machine with fine diamond wheels. Experimental results show that nanogrinding can produce flatness less than 1.0μm and a surface roughness Ra of 0.42nm. It is found that nanogrinding is capable of producing much flatter SiC wafers with a lower damage than double side lapping and mechanical polishing in much less time and it can replace double side lapping and mechanical polishing and reduce the removal amount of chemical mechanical polishing.展开更多
We present an improved angle polishing method in which the end of the cover slice near the glue layer is beveled into a thin,defect-free wedge,the straight edge of which is used as the datum for measuring the depth of...We present an improved angle polishing method in which the end of the cover slice near the glue layer is beveled into a thin,defect-free wedge,the straight edge of which is used as the datum for measuring the depth of subsurface damage. The bevel angle can be calculated from the interference fringes formed in the wedge. The minimum depth of the subsurface damage that can be measured by this method is a few hundred nanometers. Our results show that the method is straightforward, accurate, and convenient.展开更多
A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an ...A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an atomic scale. The results show that when the cutting edge radius decreases in the nanometric grinding process with the same cut-depth and grinding speed, the depth of the damage layers and the potential energy between the silicon atoms decrease too. Also, when the cut depth increases, both the depth of the damage layers and the potential energy between silicon atoms increase. When the grinding speed is between 20 and 200m/s,the depth of the damage layers does not change much with the increase of the grinding speed under the same cutting edge radius and cut depth conditions. This means that the MD simulation is not sensitive to changes in the grinding speed, and thus increasing the grinding speed properly can shorten the sion,the subsurface damage of monocrystal silicon is silicon atoms, which is verified by the ultra-precision simulation time and enlarge the simulation scale. In conclumainly based on the change of the potential energy between grinding and CMP experiments.展开更多
Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechani?cal and physical properties. It is detrimental to the strength,performance and lifetime of a machined ...Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechani?cal and physical properties. It is detrimental to the strength,performance and lifetime of a machined part. To manu?facture a high quality part,it is necessary to detect and remove the machining induced subsurface damage by the subsequent processes. However,subsurface damage is often covered with a smearing layer generated in a machining process,it is rather di cult to directly observe and detect by optical microscopy. An e cient detection of subsur?face damage directly leads to quality improvement and time saving for machining of hard and brittle materials. This paper presents a review of the methods for detection of subsurface damage,both destructive and non?destructive. Although more reliable,destructive methods are typically time?consuming and confined to local damage infor?mation. Non?destructive methods usually su er from uncertainty factors,but may provide global information on subsurface damage distribution. These methods are promising because they can provide a capacity of rapid scan and detection of subsurface damage in spatial distribution.展开更多
Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica o...Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica optics were characterized quantitatively by changes in the fluorescence intensity of feature points. The fluorescence intensity vs scan depth revealed that the maximum fluorescence intensity decreases sharply when the scan depth exceeds a critical value. The subsurface damage depth could be determined by the actual embedded depth of the quantum dots. Taper polishing and magnetorheological finishing were performed under the same conditions to verify the effectiveness of the nondestructive fluorescence method. The results indicated that the quantum dots effectively tagged subsurface defects of fused-silica optics, and that the nondestructive detection method could effectively evaluate subsurface damage depths.展开更多
A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials.Postulated conditio...A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials.Postulated condition of the model was that subsurface damage depth and peak-to-valley surface roughness are equal to depth of radial and lateral cracks in brittle surface induced by small-radius(radius≤200 μm)spherical indenter,respectively.And contribution of elastic stress field to the radial cracks propagation was also considered in the loading cycle.Subsurface damage depth of ground BK7 glasses was measured by magnetorheological finishing spot technique to validate theoretical ratio of subsurface damage to surface roughness.The results show that the ratio is directly proportional to load of abrasive grains and hardness of optical materials,while inversely proportional to granularity of abrasive grains and fracture toughness of optical materials.Moreover,the influence of the load and fracture toughness on the ratio is more significant than the granularity and hardness,respectively.The measured ratios of 80 grit and 120 grit fixed abrasive grinding of BK7 glasses are 5.8 and 5.4,respectively.展开更多
In this work,we propose to reveal the subsurface damage(SSD)of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching.Under UV illumination,SSD acts as a photoluminescence-blac...In this work,we propose to reveal the subsurface damage(SSD)of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching.Under UV illumination,SSD acts as a photoluminescence-black defect.The selective photo-chemical etching reveals SSD as the ridge-like defect.It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion.The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines,which are typical features of scratches.This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers.SSD is incorporated into 4H-SiC wafers during the lapping,rather than the chemical mechanical polishing(CMP).展开更多
Potassium dihydrogen phosphate(KDP)is an important electro-optic crystal,often used for frequency conversion and Pockels cells in large aperture laser systems.To investigate the influence of anisotropy to the depth of...Potassium dihydrogen phosphate(KDP)is an important electro-optic crystal,often used for frequency conversion and Pockels cells in large aperture laser systems.To investigate the influence of anisotropy to the depth of subsurface damage and the profiles of cracks in subsurface of KDP crystal,an experimental study was made to obtain the form of subsurface damage produced by scratches on KDP crystal in[100],[120]and[110]crystal directions on(001)crystal plane.The results indicated that there were great differences between depth and crack shape in different directions.For many slip planes in KDP,the plastic deformation and cracks generated under pressure in the subsurface were complex.Fluctuations of subsurface damage depth at transition point were attributed to the deformation of the surface which consumed more energy when the surface deformation changed from the mixed region of brittle and plastic to the complete brittle region along the scratch.Also,the process of subsurface damage from shallow to deep,from dislocation to big crack in KDP crystal with the increase of radial force and etch pit on different crystal plane were obtained.Because crystallographic orientation and processing orientation was different,etching pits on(100)crystal plane were quadrilateral while on(110)plane and(120)plane were trapezoidal and triangular,respectively.展开更多
As for the ultra-precision grinding of the hemispherical fused silica resonator,due to the hard and brittle nature of fused silica,subsurface damage(SSD)is easily generated,which enormously influences the performance ...As for the ultra-precision grinding of the hemispherical fused silica resonator,due to the hard and brittle nature of fused silica,subsurface damage(SSD)is easily generated,which enormously influences the performance of such components.Hence,ultra-precision grinding experiments are carried out to investigate the surface/subsurface quality of the hemispherical resonator machined by the small ball-end fine diamond grinding wheel.The influence of grinding parameters on the surface roughness(SR)and SSD depth of fused silica samples is then analyzed.The experimental results indicate that the SR and SSD depth decreased with the increase of grinding speed and the decrease of feed rate and grinding depth.In addition,based on the material strain rate and the maximum undeformed chip thickness,the effect of grinding parameters on the subsurface damage mechanism of fused silica samples is analyzed.Furthermore,a multi-step ultra-precision grinding technique of the hemispherical resonator is proposed based on the interaction influence between grinding depth and feed rate.Finally,the hemispherical resonator is processed by the proposed grinding technique,and the SR is improved from 454.328 nm to 110.449 nm while the SSD depth is reduced by 94%from 40μm to 2.379μm.The multi-step grinding technique proposed in this paper can guide the fabrication of the hemispherical resonator.展开更多
This paper proposes a method for the rapid detection of subsurface damage(SSD)of Si C using atmospheric inductivity coupled plasma.As a plasma etching method operated at ambient pressure with no bias voltage,this meth...This paper proposes a method for the rapid detection of subsurface damage(SSD)of Si C using atmospheric inductivity coupled plasma.As a plasma etching method operated at ambient pressure with no bias voltage,this method does not introduce any new SSD to the substrate.Plasma diagnosis and simulation are used to optimize the detection operation.Assisted by an Si C cover,a taper can be etched on the substrate with a high material removal rate.Confocal laser scanning microscopy and scanning electron microscope are used to analyze the etching results,and scanning transmission electron microscope(STEM)is adopted to confirm the accuracy of this method.The STEM result also indicates that etching does not introduce any SSD,and the thoroughly etched surface is a perfectly single crystal.A rapid SSD screening ability is also demonstrated,showing that this method is a promising approach for the rapid detection of SSD.展开更多
The subsurface damage(SSD)layers of monocrystalline germanium wafers lapped by three different ways were measured and compared by the method of nanoindentation and micro morphology.Three ways such as ice-fixed abrasiv...The subsurface damage(SSD)layers of monocrystalline germanium wafers lapped by three different ways were measured and compared by the method of nanoindentation and micro morphology.Three ways such as ice-fixed abrasive,thermosetting fixed abrasive and free abrasive lappings are adopted to lap monocrystalline germanium wafers.The SSD depth was measured by a nanoindenter,and the morphology of SSD layer was observed by an atomic force microscopy(AFM).The results show that the SSD layer of monocrystalline germanium wafer is mainly composed of soft corrosion layer and plastic scratch and crack growth layer.Compared with thermosetting fixed abrasive and free abrasive lappings,the SSD depth lapped with ice-fixed abrasive is shallower.Moreover,the SSD morphology of monocrystalline germanium wafer lapped with ice-fixed abrasive is superior to those of two other processing ways.展开更多
Laser-induced damage in fused silica optics greatly restricts the performances of laser facilities. Gray haze damage,which is always initiated on ceria polished optics, is one of the most important damage morphologies...Laser-induced damage in fused silica optics greatly restricts the performances of laser facilities. Gray haze damage,which is always initiated on ceria polished optics, is one of the most important damage morphologies in fused silica optics.In this paper, the laser-induced gray haze damages of four fused silica samples polished with CeO2, Al2O3, ZrO2, and colloidal silica slurries are investigated. Four samples all present gray haze damages with much different damage densities.Then, the polishing-induced contaminant and subsurface damages in four samples are analyzed. The results reveal that the gray haze damages could be initiated on the samples without Ce contaminant and are inclined to show a tight correlation with the shallow subsurface damages.展开更多
Silicon Carbide (SiC) wafers have been widely used in micro- and nano-devices due to their excellent optical and material properties. However, polishing SiC wafers has been challenging and inefficient, tending to caus...Silicon Carbide (SiC) wafers have been widely used in micro- and nano-devices due to their excellent optical and material properties. However, polishing SiC wafers has been challenging and inefficient, tending to cause significant surface crack and subsurface damage. This work proposed modifying SiC surface properties by ion implantation to improve machining efficiency, suppress surface crack, and reduce damage. High-energy ion implantation disrupted the SiC crystal lattice, reducing hardness and elastic modulus while increasing brittle-ductile transition depth, thus changing the removal mode from brittle fracture to plastic removal. Theoretical models of material removal rate and surface roughness were established for abrasive polishing of the SiC wafers. Polishing experiments were conducted on ion-implanted, modified SiC samples. The improvement mechanisms of ion implantation on surface damage, removal rate, morphology, and residual stress were investigated. The effect of ion implantation on the polished surface quality of SiC was investigated through orthogonal experiments. The results showed that ion implantation can significantly improve the average material removal rate of the SiC samples. Additionally, the ion-implanted samples had exhibited remarkable reductions in surface roughness, surface damage, and tensile residual stress.展开更多
In deep underground engineering construction,the dominant rock failure mode,whether by tension or shear,influences the engineering instability.Therefore,the critical triggering conditions that induce shear or tensile ...In deep underground engineering construction,the dominant rock failure mode,whether by tension or shear,influences the engineering instability.Therefore,the critical triggering conditions that induce shear or tensile fractures in rocks urgently need further investigation.This paper designs direct shear tests on intact limestone under different normal stress conditions,using binarization methods supplemented by scanning electron microscopy to explore the two-dimensional fracture damage characteristics of limestone joint surfaces.Based on the three-dimensional morphological characteristics of limestone joint surfaces,a method for automatically identifying the three-dimensional curvature of rock joint surfaces is proposed,quantifying the changes in curvature distribution under different normal stresses.Further analysis focused on the proportion of shear damage and high-curvature areas on the upper and lower joint surfaces of limestone.The study examined changes in the cumulative energy of pre-peak acoustic emission and damage under varying effective normal stress-to-shear stress ratios.These results were used to identify and validate the critical threshold range for inducing shear fractures in limestone.The conclusions indicate that the proportion of shear damage area of limestone joint surfaces is positively correlated with effective normal stress.The proportion of high curvature of limestone joint surfaces decreases with increasing normal stress.Both the rapid growth stage of shear damage area and the rapid descent stage of high curvature proportion occur in the effective normal stress to shear stress ratio range of[1.4,1.6].The cumulative energy of pre-peak acoustic emission and damage under different effective normal stress to shear stress ratios increase sharply around the ratio of 1.6,further verifying that the effective normal stress to shear stress ratio range of[1.4,1.6]is the critical threshold range for inducing shear fractures in limestone.展开更多
Nickel-based single-crystal superalloy DD98M is widely used in high-temperature components such as aero-engines and gas turbines.Since it has only one crystal grain,the theory of slip deformation along the grain bound...Nickel-based single-crystal superalloy DD98M is widely used in high-temperature components such as aero-engines and gas turbines.Since it has only one crystal grain,the theory of slip deformation along the grain boundary of polycrystalline material is not suitable for the machining of a single crystal part.Therefore,micro-drilling of nickel-based single crystal superalloy still faces problems such as unclear cutting formation me-chanism and unclear surface/subsurface damage mechanism.In this paper,the formation mechanism and morphological characteristics of chips and burrs were studied by a single-factor experiment,and the plastic deformation rule and damage mechanism were investigated,combined with the changes of subsurface structure and grain type.Finally,the influence of the law and reason of tool wear condition on the hole wall and the drilled subsurface is analyzed.The experimental results indicate that drill chips mainly exhibit three morphologies.Their free surfaces feature a serrated appearance,while the contact surfaces are smooth.The entrance burrs are mainly flanging burrs.With the increase of spindle speed,the burr height decreases from 49.38 to 9.39μm.As the feed speed increases,the burr height increases from 6.50 to 63.87μm.The drilled subsurface can be divided into a white layer region,a plastic deformation region,and the matrix according to the microstructural change.As the depth from the machined surface increases,the degree of plastic deformation of the material decreases,the grain size gradually reduces,and the dislocation density decreases.Stacking fault and twinning mostly occur in the high-plastic deformation region,and recrystallization occurs on the machined surface.As the drilling length increases,the degree of tool wear increases,and the adhesion and ablation area on the hole wall surface increase.Moreover,the thickness of the white layer increases from 0 to 8.75μm,and the thickness of the plastic deformation layer increases from 1.28 to 11.31μm.The study has significant theoretical and practical implications for the efficient and low-damage machining of micro-holes in the nickel-based single crystal superalloy.展开更多
AIM:To investigate the impact of depression-like behavior on ocular surface homeostasis in a mouse model,with a focus on dry eye-like alterations.METHODS:Male C57BL/6J mice(10-12 weeks old)were randomly assigned to co...AIM:To investigate the impact of depression-like behavior on ocular surface homeostasis in a mouse model,with a focus on dry eye-like alterations.METHODS:Male C57BL/6J mice(10-12 weeks old)were randomly assigned to control or restraint stress(RS)groups.The RS group underwent three intermittent 24-hour restraint sessions to induce depressive-like behavior.Behavioral testing,tear secretion measurement,and corneal Oregon Green Dextran(OGD)staining were performed.Postmortem analyses included histological evaluation of lacrimal glands,goblet cell quantification using periodic acid-Schiff staining,and assessment of key inflammatory and apoptotic markers:interleukin(IL)-17,matrix metalloproteinases(MMP)-3,MMP-9,IL-13,interferon(IFN)-γ,and cleaved caspase-3 and-8.RESULTS:Repeated RS induced depression-like behavior and significant ocular surface changes.RStreated mice showed increased corneal OGD uptake and upregulation of gene/protein expression of IL-17,MMP-3,and MMP-9(P<0.05).Goblet cell density and IL-13 protein expression were reduced,while IFN-γprotein expression was elevated(P<0.05).Cleaved caspase-3 and-8 levels were significantly increased in both cornea and conjunctiva.Tear volume and lacrimal gland size were unchanged;however,mild inflammatory infiltration was observed in lacrimal glands.CONCLUSION:Repeated RS leads to ocular surface inflammation and dry eye-like pathology,including corneal barrier disruption,goblet cell loss,and epithelial apoptosis.These findings suggest that depression contributes to the pathogenesis of dry eye disease via immune-mediated mechanisms.展开更多
Powdering/exfoliating of coatings and scratching galvanized steels and high strength steels （HSS）, are the main forms of surface damage in the forming of which result in increased die maintenance cost and scrap rate...Powdering/exfoliating of coatings and scratching galvanized steels and high strength steels （HSS）, are the main forms of surface damage in the forming of which result in increased die maintenance cost and scrap rate. In this study, a special rectangular box was developed to investigate the behavior and characteristics of surface damage in sheet metal forming （SMF） processes. U-channel forming tests were conducted to study the effect of tool hardness on surface damage in the forming of high strength steels and galvanized steels （hot-dip galvanized and galvannealed steels）. Experimental results indicate that sheet deformation mode influences the severity of surface damage in SMF and surface damage occurs easily at the regions where sheet specimen deforms under the action of compressive stress. Die corner is the position where surface damage initiates. For HSS sheet, surface damage is of major interest due to high forming pressure. The HSS and hot-dip galvanized steels show improved ability of damage-resistance with increased hardness of the forming tool. However, for galvannealed steel it is not the forming tool with the highest hardness value that performs best.展开更多
Deuterated potassium dihydrogen phosphate damage performance at 351 nm is studied on a large-aperture laser system. Bulk and rear-surface damage are initiated under the 3ω fluences of 6.T J/cm2 and 33/cm2, and show d...Deuterated potassium dihydrogen phosphate damage performance at 351 nm is studied on a large-aperture laser system. Bulk and rear-surface damage are initiated under the 3ω fluences of 6.T J/cm2 and 33/cm2, and show different growth characteristics under multiple laser irradiations with the fluence of 6 J/cm2. The size and number of bulk damage keep unchanged once initiated. However, surface damage size also does not grow, while surface damage number increases linearly with laser shots. Different damage thresholds and growth behaviors suggest different formations of bulk and surface damage precursors. The cause of surface damage is supposed to be near-surface absorbing particles buried under the sol-gel coating.展开更多
In order to clarify the fatigue damage evolution of concrete exposed to flexural fatigue loads,ultrasonic pulse velocity(UPV),impact-echo technology and surface electrical resistance(SR) method were used.Damage variab...In order to clarify the fatigue damage evolution of concrete exposed to flexural fatigue loads,ultrasonic pulse velocity(UPV),impact-echo technology and surface electrical resistance(SR) method were used.Damage variable based on the change of velocity of ultrasonic pulse(Du) and impact elastic wave(Di)were defined according to the classical damage theory.The influences of stress level,loading frequency and concrete strength on damage variable were measured.The experimental results show that Du and Di both present a three-stages trend for concrete exposed to fatigue loads.Since impact elastic wave is more sensitive to the microstructure damage in stage Ⅲ,the critical damage variable,i e,the damage variable before the final fracture of concrete of Di is slightly higher than that of Du.Meanwhile,the evolution of SR of concrete exposed to fatigue loads were analyzed and the relationship between SR and Du,SR and Di of concrete exposed to fatigue loads were established.It is found that the SR of concrete was decreased with the increasing fatigue cycles,indicating that surface electrical resistance method can also be applied to describe the damage of ballastless track concrete exposed to fatigue loads.展开更多
基金supported by the National Key Research and Development Program of China(2022YFB3605902)the National Natural Science Foundation of China(52375411,52293402)。
文摘Workpiece rotational grinding is widely used in the ultra-precision machining of hard and brittle semiconductor materials,including single-crystal silicon,silicon carbide,and gallium arsenide.Surface roughness and subsurface damage depth(SDD)are crucial indicators for evaluating the surface quality of these materials after grinding.Existing prediction models lack general applicability and do not accurately account for the complex material behavior under grinding conditions.This paper introduces novel models for predicting both surface roughness and SDD in hard and brittle semiconductor materials.The surface roughness model uniquely incorporates the material’s elastic recovery properties,revealing the significant impact of these properties on prediction accuracy.The SDD model is distinguished by its analysis of the interactions between abrasive grits and the workpiece,as well as the mechanisms governing stress-induced damage evolution.The surface roughness model and SDD model both establish a stable relationship with the grit depth of cut(GDC).Additionally,we have developed an analytical relationship between the GDC and grinding process parameters.This,in turn,enables the establishment of an analytical framework for predicting surface roughness and SDD based on grinding process parameters,which cannot be achieved by previous models.The models were validated through systematic experiments on three different semiconductor materials,demonstrating excellent agreement with experimental data,with prediction errors of 6.3%for surface roughness and6.9%for SDD.Additionally,this study identifies variations in elastic recovery and material plasticity as critical factors influencing surface roughness and SDD across different materials.These findings significantly advance the accuracy of predictive models and broaden their applicability for grinding hard and brittle semiconductor materials.
基金Project (50975040) supported by the National Natural Science Foundation of China
文摘Nanogrinding of SiC wafers with high flatness and low subsurface damage was proposed and nanogrinding experiments were carried out on an ultra precision grinding machine with fine diamond wheels. Experimental results show that nanogrinding can produce flatness less than 1.0μm and a surface roughness Ra of 0.42nm. It is found that nanogrinding is capable of producing much flatter SiC wafers with a lower damage than double side lapping and mechanical polishing in much less time and it can replace double side lapping and mechanical polishing and reduce the removal amount of chemical mechanical polishing.
文摘We present an improved angle polishing method in which the end of the cover slice near the glue layer is beveled into a thin,defect-free wedge,the straight edge of which is used as the datum for measuring the depth of subsurface damage. The bevel angle can be calculated from the interference fringes formed in the wedge. The minimum depth of the subsurface damage that can be measured by this method is a few hundred nanometers. Our results show that the method is straightforward, accurate, and convenient.
文摘A molecular dynamics （MD） simulation is carried out to analyze the effect of cutting edge radius,cutdepth, and grinding speed on the depth of subsurface damage layers in monocrystal silicon grinding processes on an atomic scale. The results show that when the cutting edge radius decreases in the nanometric grinding process with the same cut-depth and grinding speed, the depth of the damage layers and the potential energy between the silicon atoms decrease too. Also, when the cut depth increases, both the depth of the damage layers and the potential energy between silicon atoms increase. When the grinding speed is between 20 and 200m/s,the depth of the damage layers does not change much with the increase of the grinding speed under the same cutting edge radius and cut depth conditions. This means that the MD simulation is not sensitive to changes in the grinding speed, and thus increasing the grinding speed properly can shorten the sion,the subsurface damage of monocrystal silicon is silicon atoms, which is verified by the ultra-precision simulation time and enlarge the simulation scale. In conclumainly based on the change of the potential energy between grinding and CMP experiments.
基金Supported by National Natural Science Foundation of China(Grant No.51575084)the Science Fund for Creative Research Groups of NSFC(Grant No.51621064)the Science Challenge Project(Grant No.JCKY2016212A506–0101)
文摘Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechani?cal and physical properties. It is detrimental to the strength,performance and lifetime of a machined part. To manu?facture a high quality part,it is necessary to detect and remove the machining induced subsurface damage by the subsequent processes. However,subsurface damage is often covered with a smearing layer generated in a machining process,it is rather di cult to directly observe and detect by optical microscopy. An e cient detection of subsur?face damage directly leads to quality improvement and time saving for machining of hard and brittle materials. This paper presents a review of the methods for detection of subsurface damage,both destructive and non?destructive. Although more reliable,destructive methods are typically time?consuming and confined to local damage infor?mation. Non?destructive methods usually su er from uncertainty factors,but may provide global information on subsurface damage distribution. These methods are promising because they can provide a capacity of rapid scan and detection of subsurface damage in spatial distribution.
基金Project(JCKY2016212A506-0503) supported by the Science Challenge Project of ChinaProject(51475106) supported by the National Natural Science Foundation of China
文摘Subsurface defects were fluorescently tagged with nanoscale quantum dots and scanned layer by layer using confocal fluorescence microscopy to obtain images at various depths. Subsurface damage depths of fused silica optics were characterized quantitatively by changes in the fluorescence intensity of feature points. The fluorescence intensity vs scan depth revealed that the maximum fluorescence intensity decreases sharply when the scan depth exceeds a critical value. The subsurface damage depth could be determined by the actual embedded depth of the quantum dots. Taper polishing and magnetorheological finishing were performed under the same conditions to verify the effectiveness of the nondestructive fluorescence method. The results indicated that the quantum dots effectively tagged subsurface defects of fused-silica optics, and that the nondestructive detection method could effectively evaluate subsurface damage depths.
基金Project(50375156) supported by the National Natural Science Foundation of China
文摘A theoretical model of relationship between subsurface damage and surface roughness was established to realize rapid and non-destructive measurement of subsurface damage of ground optical materials.Postulated condition of the model was that subsurface damage depth and peak-to-valley surface roughness are equal to depth of radial and lateral cracks in brittle surface induced by small-radius(radius≤200 μm)spherical indenter,respectively.And contribution of elastic stress field to the radial cracks propagation was also considered in the loading cycle.Subsurface damage depth of ground BK7 glasses was measured by magnetorheological finishing spot technique to validate theoretical ratio of subsurface damage to surface roughness.The results show that the ratio is directly proportional to load of abrasive grains and hardness of optical materials,while inversely proportional to granularity of abrasive grains and fracture toughness of optical materials.Moreover,the influence of the load and fracture toughness on the ratio is more significant than the granularity and hardness,respectively.The measured ratios of 80 grit and 120 grit fixed abrasive grinding of BK7 glasses are 5.8 and 5.4,respectively.
基金supported by “Pioneer” and “Leading Goose”R&D Program of Zhejiang (Grant No. 2022C01021)National Key Research and Development Program of China (Grant No.2018YFB2200101)+3 种基金National Natural Science Foundation of China (Grant Nos. 91964107, 61774133)Fundamental Research Funds for the Central Universities (Grant No.2018XZZX003-02)Natural Science Foundation of China for Innovative Research Groups (Grant No. 61721005)Zhejiang University Education Foundation Global Partnership Fund
文摘In this work,we propose to reveal the subsurface damage(SSD)of 4H-SiC wafers by photo-chemical etching and identify the nature of SSD by molten-alkali etching.Under UV illumination,SSD acts as a photoluminescence-black defect.The selective photo-chemical etching reveals SSD as the ridge-like defect.It is found that the ridge-like SSD is still crystalline 4H-SiC with lattice distortion.The molten-KOH etching of the 4H-SiC wafer with ridge-like SSD transforms the ridge-like SSD into groove lines,which are typical features of scratches.This means that the underlying scratches under mechanical stress give rise to the formation of SSD in 4H-SiC wafers.SSD is incorporated into 4H-SiC wafers during the lapping,rather than the chemical mechanical polishing(CMP).
基金supported by Key National Natural Science Foundation of China(Grant No.50535020)
文摘Potassium dihydrogen phosphate(KDP)is an important electro-optic crystal,often used for frequency conversion and Pockels cells in large aperture laser systems.To investigate the influence of anisotropy to the depth of subsurface damage and the profiles of cracks in subsurface of KDP crystal,an experimental study was made to obtain the form of subsurface damage produced by scratches on KDP crystal in[100],[120]and[110]crystal directions on(001)crystal plane.The results indicated that there were great differences between depth and crack shape in different directions.For many slip planes in KDP,the plastic deformation and cracks generated under pressure in the subsurface were complex.Fluctuations of subsurface damage depth at transition point were attributed to the deformation of the surface which consumed more energy when the surface deformation changed from the mixed region of brittle and plastic to the complete brittle region along the scratch.Also,the process of subsurface damage from shallow to deep,from dislocation to big crack in KDP crystal with the increase of radial force and etch pit on different crystal plane were obtained.Because crystallographic orientation and processing orientation was different,etching pits on(100)crystal plane were quadrilateral while on(110)plane and(120)plane were trapezoidal and triangular,respectively.
基金This work was supported by the National Key Research and Development Program of China(No.2022YFB3403600)the National Natural Science Foundation of China(No.52293403)Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(No.SKLRS202204C).
文摘As for the ultra-precision grinding of the hemispherical fused silica resonator,due to the hard and brittle nature of fused silica,subsurface damage(SSD)is easily generated,which enormously influences the performance of such components.Hence,ultra-precision grinding experiments are carried out to investigate the surface/subsurface quality of the hemispherical resonator machined by the small ball-end fine diamond grinding wheel.The influence of grinding parameters on the surface roughness(SR)and SSD depth of fused silica samples is then analyzed.The experimental results indicate that the SR and SSD depth decreased with the increase of grinding speed and the decrease of feed rate and grinding depth.In addition,based on the material strain rate and the maximum undeformed chip thickness,the effect of grinding parameters on the subsurface damage mechanism of fused silica samples is analyzed.Furthermore,a multi-step ultra-precision grinding technique of the hemispherical resonator is proposed based on the interaction influence between grinding depth and feed rate.Finally,the hemispherical resonator is processed by the proposed grinding technique,and the SR is improved from 454.328 nm to 110.449 nm while the SSD depth is reduced by 94%from 40μm to 2.379μm.The multi-step grinding technique proposed in this paper can guide the fabrication of the hemispherical resonator.
基金supported by the National Natural Science Foundation of China(52035009,52005243)the Science and Technology Innovation Committee of Shenzhen Municipality(JCYJ20200109141003910,GJHZ20180928155412525)。
文摘This paper proposes a method for the rapid detection of subsurface damage(SSD)of Si C using atmospheric inductivity coupled plasma.As a plasma etching method operated at ambient pressure with no bias voltage,this method does not introduce any new SSD to the substrate.Plasma diagnosis and simulation are used to optimize the detection operation.Assisted by an Si C cover,a taper can be etched on the substrate with a high material removal rate.Confocal laser scanning microscopy and scanning electron microscope are used to analyze the etching results,and scanning transmission electron microscope(STEM)is adopted to confirm the accuracy of this method.The STEM result also indicates that etching does not introduce any SSD,and the thoroughly etched surface is a perfectly single crystal.A rapid SSD screening ability is also demonstrated,showing that this method is a promising approach for the rapid detection of SSD.
基金supported by the National Natural Science Foundation of China(No.51375237)the Postdoctoral Science Foundation of China(No.2015T80547)
文摘The subsurface damage(SSD)layers of monocrystalline germanium wafers lapped by three different ways were measured and compared by the method of nanoindentation and micro morphology.Three ways such as ice-fixed abrasive,thermosetting fixed abrasive and free abrasive lappings are adopted to lap monocrystalline germanium wafers.The SSD depth was measured by a nanoindenter,and the morphology of SSD layer was observed by an atomic force microscopy(AFM).The results show that the SSD layer of monocrystalline germanium wafer is mainly composed of soft corrosion layer and plastic scratch and crack growth layer.Compared with thermosetting fixed abrasive and free abrasive lappings,the SSD depth lapped with ice-fixed abrasive is shallower.Moreover,the SSD morphology of monocrystalline germanium wafer lapped with ice-fixed abrasive is superior to those of two other processing ways.
文摘Laser-induced damage in fused silica optics greatly restricts the performances of laser facilities. Gray haze damage,which is always initiated on ceria polished optics, is one of the most important damage morphologies in fused silica optics.In this paper, the laser-induced gray haze damages of four fused silica samples polished with CeO2, Al2O3, ZrO2, and colloidal silica slurries are investigated. Four samples all present gray haze damages with much different damage densities.Then, the polishing-induced contaminant and subsurface damages in four samples are analyzed. The results reveal that the gray haze damages could be initiated on the samples without Ce contaminant and are inclined to show a tight correlation with the shallow subsurface damages.
基金support from the China Postdoctoral Science Foundation(No.2023M742735)the Postdoctoral Fellowship Program of CPSF,China(No.GZC20232029)+5 种基金the National Natural Science Foundation of China(No.52475530)the Shaanxi Postdoctoral Science Foundation,China(No.2023BSHEDZZ175)the Innovation Capability Support Program of Shaanxi Province,China(No.2021TD-23)the Key Industrial Chain Core Technology Research Project in Xi’an,China(No.23LLRH0029)the Natural Science Basic Research Program of Shaanxi,China(No.2024JC-YBQN-0490)the Fundamental Research Funds for the Central Universities,China(No.ZYTS24023).
文摘Silicon Carbide (SiC) wafers have been widely used in micro- and nano-devices due to their excellent optical and material properties. However, polishing SiC wafers has been challenging and inefficient, tending to cause significant surface crack and subsurface damage. This work proposed modifying SiC surface properties by ion implantation to improve machining efficiency, suppress surface crack, and reduce damage. High-energy ion implantation disrupted the SiC crystal lattice, reducing hardness and elastic modulus while increasing brittle-ductile transition depth, thus changing the removal mode from brittle fracture to plastic removal. Theoretical models of material removal rate and surface roughness were established for abrasive polishing of the SiC wafers. Polishing experiments were conducted on ion-implanted, modified SiC samples. The improvement mechanisms of ion implantation on surface damage, removal rate, morphology, and residual stress were investigated. The effect of ion implantation on the polished surface quality of SiC was investigated through orthogonal experiments. The results showed that ion implantation can significantly improve the average material removal rate of the SiC samples. Additionally, the ion-implanted samples had exhibited remarkable reductions in surface roughness, surface damage, and tensile residual stress.
基金Projects(52004147,51974173)supported by the National Natural Science Foundation of ChinaProject(GJNY-20-113-19)supported by the Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining,China。
文摘In deep underground engineering construction,the dominant rock failure mode,whether by tension or shear,influences the engineering instability.Therefore,the critical triggering conditions that induce shear or tensile fractures in rocks urgently need further investigation.This paper designs direct shear tests on intact limestone under different normal stress conditions,using binarization methods supplemented by scanning electron microscopy to explore the two-dimensional fracture damage characteristics of limestone joint surfaces.Based on the three-dimensional morphological characteristics of limestone joint surfaces,a method for automatically identifying the three-dimensional curvature of rock joint surfaces is proposed,quantifying the changes in curvature distribution under different normal stresses.Further analysis focused on the proportion of shear damage and high-curvature areas on the upper and lower joint surfaces of limestone.The study examined changes in the cumulative energy of pre-peak acoustic emission and damage under varying effective normal stress-to-shear stress ratios.These results were used to identify and validate the critical threshold range for inducing shear fractures in limestone.The conclusions indicate that the proportion of shear damage area of limestone joint surfaces is positively correlated with effective normal stress.The proportion of high curvature of limestone joint surfaces decreases with increasing normal stress.Both the rapid growth stage of shear damage area and the rapid descent stage of high curvature proportion occur in the effective normal stress to shear stress ratio range of[1.4,1.6].The cumulative energy of pre-peak acoustic emission and damage under different effective normal stress to shear stress ratios increase sharply around the ratio of 1.6,further verifying that the effective normal stress to shear stress ratio range of[1.4,1.6]is the critical threshold range for inducing shear fractures in limestone.
基金Supported by National Natural Science Foundation of China(Grant Nos.52475433,52305453)Hebei Provincial Natural Science Foundation(Grant No.E2022501004)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2023GFYD002)Shijiazhuang Municipal Science and Technology Plan Project(Grant No.241790747A).
文摘Nickel-based single-crystal superalloy DD98M is widely used in high-temperature components such as aero-engines and gas turbines.Since it has only one crystal grain,the theory of slip deformation along the grain boundary of polycrystalline material is not suitable for the machining of a single crystal part.Therefore,micro-drilling of nickel-based single crystal superalloy still faces problems such as unclear cutting formation me-chanism and unclear surface/subsurface damage mechanism.In this paper,the formation mechanism and morphological characteristics of chips and burrs were studied by a single-factor experiment,and the plastic deformation rule and damage mechanism were investigated,combined with the changes of subsurface structure and grain type.Finally,the influence of the law and reason of tool wear condition on the hole wall and the drilled subsurface is analyzed.The experimental results indicate that drill chips mainly exhibit three morphologies.Their free surfaces feature a serrated appearance,while the contact surfaces are smooth.The entrance burrs are mainly flanging burrs.With the increase of spindle speed,the burr height decreases from 49.38 to 9.39μm.As the feed speed increases,the burr height increases from 6.50 to 63.87μm.The drilled subsurface can be divided into a white layer region,a plastic deformation region,and the matrix according to the microstructural change.As the depth from the machined surface increases,the degree of plastic deformation of the material decreases,the grain size gradually reduces,and the dislocation density decreases.Stacking fault and twinning mostly occur in the high-plastic deformation region,and recrystallization occurs on the machined surface.As the drilling length increases,the degree of tool wear increases,and the adhesion and ablation area on the hole wall surface increase.Moreover,the thickness of the white layer increases from 0 to 8.75μm,and the thickness of the plastic deformation layer increases from 1.28 to 11.31μm.The study has significant theoretical and practical implications for the efficient and low-damage machining of micro-holes in the nickel-based single crystal superalloy.
基金Supported by the Key Program of the National Natural Science Foundation of China(No.82530034)the National Natural Science Foundation of China(No.82271054)the Nature Science Foundation of Xiamen,China(No.3502Z20227121).
文摘AIM:To investigate the impact of depression-like behavior on ocular surface homeostasis in a mouse model,with a focus on dry eye-like alterations.METHODS:Male C57BL/6J mice(10-12 weeks old)were randomly assigned to control or restraint stress(RS)groups.The RS group underwent three intermittent 24-hour restraint sessions to induce depressive-like behavior.Behavioral testing,tear secretion measurement,and corneal Oregon Green Dextran(OGD)staining were performed.Postmortem analyses included histological evaluation of lacrimal glands,goblet cell quantification using periodic acid-Schiff staining,and assessment of key inflammatory and apoptotic markers:interleukin(IL)-17,matrix metalloproteinases(MMP)-3,MMP-9,IL-13,interferon(IFN)-γ,and cleaved caspase-3 and-8.RESULTS:Repeated RS induced depression-like behavior and significant ocular surface changes.RStreated mice showed increased corneal OGD uptake and upregulation of gene/protein expression of IL-17,MMP-3,and MMP-9(P<0.05).Goblet cell density and IL-13 protein expression were reduced,while IFN-γprotein expression was elevated(P<0.05).Cleaved caspase-3 and-8 levels were significantly increased in both cornea and conjunctiva.Tear volume and lacrimal gland size were unchanged;however,mild inflammatory infiltration was observed in lacrimal glands.CONCLUSION:Repeated RS leads to ocular surface inflammation and dry eye-like pathology,including corneal barrier disruption,goblet cell loss,and epithelial apoptosis.These findings suggest that depression contributes to the pathogenesis of dry eye disease via immune-mediated mechanisms.
基金supported by the National Natural Science Foundation of China under grant No. 50605043
文摘Powdering/exfoliating of coatings and scratching galvanized steels and high strength steels （HSS）, are the main forms of surface damage in the forming of which result in increased die maintenance cost and scrap rate. In this study, a special rectangular box was developed to investigate the behavior and characteristics of surface damage in sheet metal forming （SMF） processes. U-channel forming tests were conducted to study the effect of tool hardness on surface damage in the forming of high strength steels and galvanized steels （hot-dip galvanized and galvannealed steels）. Experimental results indicate that sheet deformation mode influences the severity of surface damage in SMF and surface damage occurs easily at the regions where sheet specimen deforms under the action of compressive stress. Die corner is the position where surface damage initiates. For HSS sheet, surface damage is of major interest due to high forming pressure. The HSS and hot-dip galvanized steels show improved ability of damage-resistance with increased hardness of the forming tool. However, for galvannealed steel it is not the forming tool with the highest hardness value that performs best.
基金Supported by the National Natural Science Foundation of China under Grant No 61505187
文摘Deuterated potassium dihydrogen phosphate damage performance at 351 nm is studied on a large-aperture laser system. Bulk and rear-surface damage are initiated under the 3ω fluences of 6.T J/cm2 and 33/cm2, and show different growth characteristics under multiple laser irradiations with the fluence of 6 J/cm2. The size and number of bulk damage keep unchanged once initiated. However, surface damage size also does not grow, while surface damage number increases linearly with laser shots. Different damage thresholds and growth behaviors suggest different formations of bulk and surface damage precursors. The cause of surface damage is supposed to be near-surface absorbing particles buried under the sol-gel coating.
基金Funded by the National Natural Science Foundation of China(Nos.U1934206,52208299,and 52108260)the 2021 Tencent XPLORER PRIZE。
文摘In order to clarify the fatigue damage evolution of concrete exposed to flexural fatigue loads,ultrasonic pulse velocity(UPV),impact-echo technology and surface electrical resistance(SR) method were used.Damage variable based on the change of velocity of ultrasonic pulse(Du) and impact elastic wave(Di)were defined according to the classical damage theory.The influences of stress level,loading frequency and concrete strength on damage variable were measured.The experimental results show that Du and Di both present a three-stages trend for concrete exposed to fatigue loads.Since impact elastic wave is more sensitive to the microstructure damage in stage Ⅲ,the critical damage variable,i e,the damage variable before the final fracture of concrete of Di is slightly higher than that of Du.Meanwhile,the evolution of SR of concrete exposed to fatigue loads were analyzed and the relationship between SR and Du,SR and Di of concrete exposed to fatigue loads were established.It is found that the SR of concrete was decreased with the increasing fatigue cycles,indicating that surface electrical resistance method can also be applied to describe the damage of ballastless track concrete exposed to fatigue loads.
