Fracture toughness is an important index in safety evaluation for materials and structures.Its convenient and accurate characterization has attracted extensive attention.For small specimens,traditional testing methods...Fracture toughness is an important index in safety evaluation for materials and structures.Its convenient and accurate characterization has attracted extensive attention.For small specimens,traditional testing methods of fracture toughness are not suitable due to limitations in sample size and shape.In this work,a new formula is proposed to determine the fracture toughness of glasses using scratch tests with a Vickers indenter based on dimensional analysis and finite element analysis.Fracture toughness of glasses could be calculated with elastic modulus,crack depth of scratched materials and normal force applied during the scratch tests.The effects of plastic deformation and interfacial friction between the Vickers indenter and scratched materials are considered,and the crack shape is consistent with experimental observations.The proposed formula is verified by comparing the fracture toughness of soda-lime and borosilicate glasses obtained from scratch tests with those obtained via indentation tests.This work provides an alternative method to determine the fracture toughness of glass materials.展开更多
This paper proposes a methodology to construct logs of rock strength from the cutting force signal recorded in scratch tests conducted in the ductile regime.The approach,which is based on the application of discrete w...This paper proposes a methodology to construct logs of rock strength from the cutting force signal recorded in scratch tests conducted in the ductile regime.The approach,which is based on the application of discrete wavelet transforms,recognizes the existence of two length scales[c and[r.The strength length scale[c represents the length over which it is meaningful to measure strength,while the repeatability length scale[r is related to the resolution at which the force signal must be observed to become insensitive to the stochastic micro-failure events triggered by the motion of the cutter.It is postulated that the original cutting force signal,assumed to be sampled at a high enough frequency,can be decomposed into a deterministic signal intrinsic to the rock and a stochastic one resulting from discrete rock failure events.The technique of multiresolution analysis based on the maximal overlap discrete wavelet transform is applied as a low-pass filter to the original cutting force signals so as to wipe out the high-frequency components associated with the stochastic rock failure events.A criterion to determine the optimum cutoff frequency of the low-pass filter and the corresponding repeatability length scale is discussed in terms of the correlation coefficients between different filtered signals.It is shown that the low-pass filtered signals obtained at the optimum cutoff frequency have two salient features:(i)repeatability over different tests conducted at the same depth of cut on the same sample,and(ii)variability along the cutting distance.The excellent repeatability reveals that the deterministic background trend of the original force signals is relevant to the rock strength property,and the variability of the background trend captures the spatial variation of the rock strength.展开更多
In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematica...In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined byscratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data arediscussed.展开更多
Micro-scale abrasion testing is widely used to determine the abrasion resistance of thin film coatings; it is a simple technique that can easily be used as part of a quality control procedure, but it has got the disad...Micro-scale abrasion testing is widely used to determine the abrasion resistance of thin film coatings; it is a simple technique that can easily be used as part of a quality control procedure, but it has got the disadvantage of not allowing an easy study of the wear mechanisms involved: it is difficult to estimate the load applied on each abrasive particles in the contact between the loaded ball and the specimen. The possibility of using progressive loading scratch testing, a method widely used to assess the adhesion of thin film coatings, to model the abrasive wear of coatings has been studied in the past; the use of multiple scratch tests to study the wear mechanisms corresponding to a single abrasion scratch event has also been studied in the case of bulk materials (ceramics and hard metals). Two coatings, deposited by Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUBMSIP) on ASP23 powder metallurgy steel substrate are chosen to be representative of the use of protective coatings in industry: titanium nitride, which is widely used to prevent tool wear, and TCL Graphit-iC?, which is widely used as a wear resistant solid lubricant coating. The two coatings are first characterised by using a standard quality control procedure: their thickness is determined by the cap grinding method, their adhesion by progressive loading scratch. Then micro-scale abrasion tests performed with a slurry at a concentration which promotes grooving wear, and medium load multiple scratch tests performed with diamond indenters are completed; the results of these tests are analysed and compared to determine if there is any correlation between the two sets of results; the multiple scratch tests wear tracks are also observed to determine the wear mechanisms involved.展开更多
Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are ...Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are attractive at different scales.Each method requires minimal sample volume,is low cost,and includes a relatively rapid measurement turnaround time.However,recent micro-scale test results–including scratch test results and nanoindentation results–exhibit tangible variance and uncertainty,suggesting a need to correlate mineral composition mapping to elastic modulus mapping to isolate the relative impact of specific minerals.Different research labs often utilize different interpretation methods,and it is clear that future micro-mechanical tests may benefit from standardized testing and interpretation procedures.The objectives of this study are to seek options for standardized testing and interpretation procedures,through two specific objectives:(1)Quantify chemical and physical controls on micro-mechanical properties and(2)Quantify the source of uncertainties associated with nanoindentation measurements.To reach these goals,we conducted mechanical tests on three different scales:triaxial compression tests,scratch tests,and nanoindentation tests.We found that mineral phase weight percentage is highly correlated with nanoindentation elastic modulus distribution.Finally,we conclude that nanoindentation testing is a mineralogy and microstructure-based method and generally yields significant uncertainty and overestimation.The uncertainty of the testing method is largely associated with not mapping pore space a priori.Lastly,the uncertainty can be reduced by combining phase mapping and modulus mapping with substantial and random data sampling.展开更多
Abrasiveness as an intrinsic property of rocks defines the extent of wear or loss when interacting with other materials.In engineering sectors like hard rock mining and tunnelling,comprehending rock abrasiveness holds...Abrasiveness as an intrinsic property of rocks defines the extent of wear or loss when interacting with other materials.In engineering sectors like hard rock mining and tunnelling,comprehending rock abrasiveness holds paramount importance due to its direct effect on tool wear during excavation.Among the diverse methods for assessing rock abrasiveness,the Cerchar abrasivity test emerges as the most widely used approach.Over time,the Cerchar test has garnered substantial attention from scholars,who have delved into the factors influencing test results due to testing conditions and examined the connection between the physical-mechanical parameters of rocks and their abrasiveness.Recent advancements in testing instrument have expanded our ability to measure additional parameters during rock cutting or drilling,yielding fresh insights for abrasiveness assessment,tool wear prediction,tool performance evaluation and rock excavatability estimation.The Cerchar abrasivity test,coupled with recent developments in testing instrument and parameter measurement,holds promising potential for enhancing our comprehension of rock abrasiveness and its practical implications.This review systematically traces the evolution of the test.It commences with an overview of the test origin and progression,emphasizing its pivotal role in assessing rock abrasiveness.Furthermore,it consolidates and categorizes the research contributions from various scholars regarding the test.This includes enhancements and refinements of the testing apparatus,as well as investigations into various testing orientations and their effects on different types of rocks.Moreover,this review illuminates the broader applications and interdisciplinary possibilities of this test,not only in material science but also in tribology.It underscores how the insights gleaned from the Cerchar test can be extrapolated to diverse areas of research beyond the scope of rock engineering.展开更多
Shale reservoirs have been a significant focus of hydrocarbon production over the past few decades,and the mechanical assessment of target shale reservoirs has been critical to successful field operations,especially i...Shale reservoirs have been a significant focus of hydrocarbon production over the past few decades,and the mechanical assessment of target shale reservoirs has been critical to successful field operations,especially in hydraulic fracturing and well completions.The Unconfined compressive strength(UCS)and Poisson's ratio(ν)are critical mechanical properties in shale reservoir assessment.The estimation and measurement of shale mechanical properties are often erroneous by not accounting for their heterogeneous and pre-existing features,which yield variability of shale mechanical properties along their lithostratigraphy.Thus,there is a need to investigate the degree of correlation and accuracy in multiscale mechanical evaluations of heterogeneous shales,and the correlation between such micromechanical and macromechanical measurements.This study investigated the impact of inherent heterogeneity on the measurement of continuous micromechanical and macromechanical properties of shale reservoirs using scratch test(ST)and uniaxial compression test(UCT)methods,and the degree of correlation(correlation coefficient,r)of measurements in shale was further assessed for the variability of their measured properties.Shale core samples from three distinct shale formations were utilized and studied,and the core samples were subjected to ST and UCT,respectively.The results from this study showed that despite inherent heterogeneous anomalies and natural fractures in the shale samples analyzed,there is a good degree of correlation(UCS:r=0.73;ν:r=0.89)in the micro-and macro-mechanical properties of shales using two independent experimental tests(ST and UCT).This study provides insights for improving the accuracy of mechanical evaluations and numerical modeling in shales with a high degree of heterogeneity and pre-existing natural fractures.The results indicate that when considering the structural complexity and heterogeneity of unconventional reservoirs such as shales,the ST method can provide a better continuous micromechanical assessment of shales.In contrast,the UCT can provide a better bulk macromechanical measurement of shales.展开更多
The interface adhesion strength(or interface toughness)of a thin film/substrate system is often assessed by the micro-scratch test.For a brittle film material,the interface adhesion strength is easily obtained through...The interface adhesion strength(or interface toughness)of a thin film/substrate system is often assessed by the micro-scratch test.For a brittle film material,the interface adhesion strength is easily obtained through measuring the scratch driving forces.However,to measure the interface adhesion strength(or in- terface toughness)for a metal thin film material(the ductile material)by the micro- scratch test is very difficult,because intense plastic deformation is involved and the problem is a three-dimensional elastic-plastic one.In the present research,using a double-cohesive zone model,the failure characteristics of the thin film/substrate system can be described and further simulated.For a steady-state scratching pro- cess,a three-dimensional elastic-plastic finite element method based on the double cohesive zone model is developed and adopted,and the steady-state fracture work of the total system is calculated.The parameter relations between the horizontal driving forces(or energy release rate of the scratching process)and the separation strength of thin film/substrate interface,and the material shear strength,as well as the material parameters are developed.Furthermore,a scratch experiment for the Al/Si film/substrate system is carried out and the failure mechanisms are explored. Finally,the prediction results are applied to a scratch experiment for the Pt/NiO material system given in the literature.展开更多
The nanoscratch behaviors of La0.7Sr0.3MnO3＋δ films, which were deposited with ratio of O2/（O2＋Ar）, ranging from 4.4% to 45.6% by DC magnetron sputter, were investigated by a nanoindentation technique. The result...The nanoscratch behaviors of La0.7Sr0.3MnO3＋δ films, which were deposited with ratio of O2/（O2＋Ar）, ranging from 4.4% to 45.6% by DC magnetron sputter, were investigated by a nanoindentation technique. The results indicated that the friction coefficient between the films and the diamond tip depended on the loading critical load. The friction coefficient was about 0.08-0.12 when the loading normal load was less than the loading critical load. The films displayed excellent elastic recovery after unloading. When the loading load was larger than the loading critical load, plastic deformation and ploughing appeared for the films. The friction coefficient was about 0.43 when the film was damaged completely. The suitable decrease in ratio of O2/（O2＋Ar） could improve the nanoscratch resistance of the films. The film deposited with O2/（O2＋Ar）=25% possessed better scratch resistance due to good elastic recovery, high nanohardness, and critical load. The loading critical load of the film was larger than 80 raN.展开更多
A challenge in the restoration of historical buildings is strengthened in order to guarantee their durability and the evaluation of the correct identification of materials which need to be the results of consolidation...A challenge in the restoration of historical buildings is strengthened in order to guarantee their durability and the evaluation of the correct identification of materials which need to be the results of consolidation treatments which may be applied during their repair. Methods which make such a complex characterization possible are rare. This paper presents an investigation carried out at the University of Mons （Belgium） in collaboration with the technical support and control unit, restoration directorate, of the Walloon region, aiming to evaluate the effectiveness of consolidants used to strengthen stone masonry. The characterization of the materials is based on a novel semi-destructive scratching method which allows tomographic representation of the strength of the damaged and treated areas. This paper describes the experimental methodology and presents results from laboratory experiments as well as a case study.展开更多
Objective: To introduce the concept that there might be “nothing to smell” to the Brief Smell Identification Test (B-SIT), with a view to masking olfactory deficits, particularly from healthy control participants in...Objective: To introduce the concept that there might be “nothing to smell” to the Brief Smell Identification Test (B-SIT), with a view to masking olfactory deficits, particularly from healthy control participants in research studies. Methods: Seventy-one elderly individuals, healthy for their age, were recruited to the study. They were blindfolded and carried out a modified B-SIT where one item had been replaced with a placebo, and one odour alternative answer to three other items was replaced by the alternative “none/other” (actual odour unchanged). Results: There was no overall difference in the median or mean score achieved by the cohort compared to results obtained previously using the conventional B-SIT. The replacement of the item “turpentine” with a placebo resulted in an improved score for the item in a Norwegian setting. The overall scores were not improved. Conclusions: It is possible to introduce the concept that there may be “nothing to smell” to the B-SIT without compromising the test for healthy control individuals. This may be a more appropriate approach to olfactory testing of control individuals or patients with suspected early neurodegenerative diseases.展开更多
Experimental scratch tests and first-principles calculations were used to investigate the adhesion property of AlCrNbSiTi high-entropy alloy(HEA)coatings on zirconium substrates.AlCrNbSiTi HEA and Cr coatings were dep...Experimental scratch tests and first-principles calculations were used to investigate the adhesion property of AlCrNbSiTi high-entropy alloy(HEA)coatings on zirconium substrates.AlCrNbSiTi HEA and Cr coatings were deposited on Zr alloy substrates using multi-arc ion plating technology,and scratch tests were subsequently conducted to estimate the adhesion property of the coatings.The results indicated that Cr coatings had better adhesion strength than HEA coatings,and the HEA coatings showed brittleness.The special quasi-random structure approach was used to build HEA models,and Cr/Zr and HEA/Zr interface models were employed to investigate the cohesion between the coatings and Zr substrate using first-principles calculations.The calculated interface energies showed that the cohesion between the Cr coating and the Zr substrate was stronger than that of the HEA coating with Zr.In contrary to Al or Si in the HEA coating,Cr,Nb,and Ti atoms binded strongly with Zr substrate.Based on the calculated elastic constants,it was found that low Cr and high Al content decreased the mechanical performances of HEA coatings.Finally,this study demonstrated the utilization of a combined approach involving first-principles calculations and experimental studies for future HEA coating development.展开更多
基金the financial support from National Natural Science Foundation of China(Nos.12072324 and U1804254)Natural Science Foundation of Henan Province for Excellent Young Scholars(212300410087).
文摘Fracture toughness is an important index in safety evaluation for materials and structures.Its convenient and accurate characterization has attracted extensive attention.For small specimens,traditional testing methods of fracture toughness are not suitable due to limitations in sample size and shape.In this work,a new formula is proposed to determine the fracture toughness of glasses using scratch tests with a Vickers indenter based on dimensional analysis and finite element analysis.Fracture toughness of glasses could be calculated with elastic modulus,crack depth of scratched materials and normal force applied during the scratch tests.The effects of plastic deformation and interfacial friction between the Vickers indenter and scratched materials are considered,and the crack shape is consistent with experimental observations.The proposed formula is verified by comparing the fracture toughness of soda-lime and borosilicate glasses obtained from scratch tests with those obtained via indentation tests.This work provides an alternative method to determine the fracture toughness of glass materials.
基金provided by the National Science Foundation of USA(Grant No.1742823)。
文摘This paper proposes a methodology to construct logs of rock strength from the cutting force signal recorded in scratch tests conducted in the ductile regime.The approach,which is based on the application of discrete wavelet transforms,recognizes the existence of two length scales[c and[r.The strength length scale[c represents the length over which it is meaningful to measure strength,while the repeatability length scale[r is related to the resolution at which the force signal must be observed to become insensitive to the stochastic micro-failure events triggered by the motion of the cutter.It is postulated that the original cutting force signal,assumed to be sampled at a high enough frequency,can be decomposed into a deterministic signal intrinsic to the rock and a stochastic one resulting from discrete rock failure events.The technique of multiresolution analysis based on the maximal overlap discrete wavelet transform is applied as a low-pass filter to the original cutting force signals so as to wipe out the high-frequency components associated with the stochastic rock failure events.A criterion to determine the optimum cutoff frequency of the low-pass filter and the corresponding repeatability length scale is discussed in terms of the correlation coefficients between different filtered signals.It is shown that the low-pass filtered signals obtained at the optimum cutoff frequency have two salient features:(i)repeatability over different tests conducted at the same depth of cut on the same sample,and(ii)variability along the cutting distance.The excellent repeatability reveals that the deterministic background trend of the original force signals is relevant to the rock strength property,and the variability of the background trend captures the spatial variation of the rock strength.
文摘In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined byscratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data arediscussed.
文摘Micro-scale abrasion testing is widely used to determine the abrasion resistance of thin film coatings; it is a simple technique that can easily be used as part of a quality control procedure, but it has got the disadvantage of not allowing an easy study of the wear mechanisms involved: it is difficult to estimate the load applied on each abrasive particles in the contact between the loaded ball and the specimen. The possibility of using progressive loading scratch testing, a method widely used to assess the adhesion of thin film coatings, to model the abrasive wear of coatings has been studied in the past; the use of multiple scratch tests to study the wear mechanisms corresponding to a single abrasion scratch event has also been studied in the case of bulk materials (ceramics and hard metals). Two coatings, deposited by Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUBMSIP) on ASP23 powder metallurgy steel substrate are chosen to be representative of the use of protective coatings in industry: titanium nitride, which is widely used to prevent tool wear, and TCL Graphit-iC?, which is widely used as a wear resistant solid lubricant coating. The two coatings are first characterised by using a standard quality control procedure: their thickness is determined by the cap grinding method, their adhesion by progressive loading scratch. Then micro-scale abrasion tests performed with a slurry at a concentration which promotes grooving wear, and medium load multiple scratch tests performed with diamond indenters are completed; the results of these tests are analysed and compared to determine if there is any correlation between the two sets of results; the multiple scratch tests wear tracks are also observed to determine the wear mechanisms involved.
基金support of this project through the Southwest Regional Partnership on Carbon Sequestration(Grant No.DE-FC26-05NT42591)Improving Production in the Emerging Paradox Oil Play(Grant No.DE-FE0031775).
文摘Geomechanical properties of rocks vary across different measurement scales,primarily due to heterogeneity.Micro-scale geomechanical tests,including micro-scale“scratch tests”and nano-scale nanoindentation tests,are attractive at different scales.Each method requires minimal sample volume,is low cost,and includes a relatively rapid measurement turnaround time.However,recent micro-scale test results–including scratch test results and nanoindentation results–exhibit tangible variance and uncertainty,suggesting a need to correlate mineral composition mapping to elastic modulus mapping to isolate the relative impact of specific minerals.Different research labs often utilize different interpretation methods,and it is clear that future micro-mechanical tests may benefit from standardized testing and interpretation procedures.The objectives of this study are to seek options for standardized testing and interpretation procedures,through two specific objectives:(1)Quantify chemical and physical controls on micro-mechanical properties and(2)Quantify the source of uncertainties associated with nanoindentation measurements.To reach these goals,we conducted mechanical tests on three different scales:triaxial compression tests,scratch tests,and nanoindentation tests.We found that mineral phase weight percentage is highly correlated with nanoindentation elastic modulus distribution.Finally,we conclude that nanoindentation testing is a mineralogy and microstructure-based method and generally yields significant uncertainty and overestimation.The uncertainty of the testing method is largely associated with not mapping pore space a priori.Lastly,the uncertainty can be reduced by combining phase mapping and modulus mapping with substantial and random data sampling.
文摘Abrasiveness as an intrinsic property of rocks defines the extent of wear or loss when interacting with other materials.In engineering sectors like hard rock mining and tunnelling,comprehending rock abrasiveness holds paramount importance due to its direct effect on tool wear during excavation.Among the diverse methods for assessing rock abrasiveness,the Cerchar abrasivity test emerges as the most widely used approach.Over time,the Cerchar test has garnered substantial attention from scholars,who have delved into the factors influencing test results due to testing conditions and examined the connection between the physical-mechanical parameters of rocks and their abrasiveness.Recent advancements in testing instrument have expanded our ability to measure additional parameters during rock cutting or drilling,yielding fresh insights for abrasiveness assessment,tool wear prediction,tool performance evaluation and rock excavatability estimation.The Cerchar abrasivity test,coupled with recent developments in testing instrument and parameter measurement,holds promising potential for enhancing our comprehension of rock abrasiveness and its practical implications.This review systematically traces the evolution of the test.It commences with an overview of the test origin and progression,emphasizing its pivotal role in assessing rock abrasiveness.Furthermore,it consolidates and categorizes the research contributions from various scholars regarding the test.This includes enhancements and refinements of the testing apparatus,as well as investigations into various testing orientations and their effects on different types of rocks.Moreover,this review illuminates the broader applications and interdisciplinary possibilities of this test,not only in material science but also in tribology.It underscores how the insights gleaned from the Cerchar test can be extrapolated to diverse areas of research beyond the scope of rock engineering.
文摘Shale reservoirs have been a significant focus of hydrocarbon production over the past few decades,and the mechanical assessment of target shale reservoirs has been critical to successful field operations,especially in hydraulic fracturing and well completions.The Unconfined compressive strength(UCS)and Poisson's ratio(ν)are critical mechanical properties in shale reservoir assessment.The estimation and measurement of shale mechanical properties are often erroneous by not accounting for their heterogeneous and pre-existing features,which yield variability of shale mechanical properties along their lithostratigraphy.Thus,there is a need to investigate the degree of correlation and accuracy in multiscale mechanical evaluations of heterogeneous shales,and the correlation between such micromechanical and macromechanical measurements.This study investigated the impact of inherent heterogeneity on the measurement of continuous micromechanical and macromechanical properties of shale reservoirs using scratch test(ST)and uniaxial compression test(UCT)methods,and the degree of correlation(correlation coefficient,r)of measurements in shale was further assessed for the variability of their measured properties.Shale core samples from three distinct shale formations were utilized and studied,and the core samples were subjected to ST and UCT,respectively.The results from this study showed that despite inherent heterogeneous anomalies and natural fractures in the shale samples analyzed,there is a good degree of correlation(UCS:r=0.73;ν:r=0.89)in the micro-and macro-mechanical properties of shales using two independent experimental tests(ST and UCT).This study provides insights for improving the accuracy of mechanical evaluations and numerical modeling in shales with a high degree of heterogeneity and pre-existing natural fractures.The results indicate that when considering the structural complexity and heterogeneity of unconventional reservoirs such as shales,the ST method can provide a better continuous micromechanical assessment of shales.In contrast,the UCT can provide a better bulk macromechanical measurement of shales.
基金The project supported by the National Natural Science Foundation of China (19891180 and 19925211)Bai Ren Plan of CAS
文摘The interface adhesion strength(or interface toughness)of a thin film/substrate system is often assessed by the micro-scratch test.For a brittle film material,the interface adhesion strength is easily obtained through measuring the scratch driving forces.However,to measure the interface adhesion strength(or in- terface toughness)for a metal thin film material(the ductile material)by the micro- scratch test is very difficult,because intense plastic deformation is involved and the problem is a three-dimensional elastic-plastic one.In the present research,using a double-cohesive zone model,the failure characteristics of the thin film/substrate system can be described and further simulated.For a steady-state scratching pro- cess,a three-dimensional elastic-plastic finite element method based on the double cohesive zone model is developed and adopted,and the steady-state fracture work of the total system is calculated.The parameter relations between the horizontal driving forces(or energy release rate of the scratching process)and the separation strength of thin film/substrate interface,and the material shear strength,as well as the material parameters are developed.Furthermore,a scratch experiment for the Al/Si film/substrate system is carried out and the failure mechanisms are explored. Finally,the prediction results are applied to a scratch experiment for the Pt/NiO material system given in the literature.
基金supported by the Program for New Century Excellent Talents in University
文摘The nanoscratch behaviors of La0.7Sr0.3MnO3＋δ films, which were deposited with ratio of O2/（O2＋Ar）, ranging from 4.4% to 45.6% by DC magnetron sputter, were investigated by a nanoindentation technique. The results indicated that the friction coefficient between the films and the diamond tip depended on the loading critical load. The friction coefficient was about 0.08-0.12 when the loading normal load was less than the loading critical load. The films displayed excellent elastic recovery after unloading. When the loading load was larger than the loading critical load, plastic deformation and ploughing appeared for the films. The friction coefficient was about 0.43 when the film was damaged completely. The suitable decrease in ratio of O2/（O2＋Ar） could improve the nanoscratch resistance of the films. The film deposited with O2/（O2＋Ar）=25% possessed better scratch resistance due to good elastic recovery, high nanohardness, and critical load. The loading critical load of the film was larger than 80 raN.
文摘A challenge in the restoration of historical buildings is strengthened in order to guarantee their durability and the evaluation of the correct identification of materials which need to be the results of consolidation treatments which may be applied during their repair. Methods which make such a complex characterization possible are rare. This paper presents an investigation carried out at the University of Mons （Belgium） in collaboration with the technical support and control unit, restoration directorate, of the Walloon region, aiming to evaluate the effectiveness of consolidants used to strengthen stone masonry. The characterization of the materials is based on a novel semi-destructive scratching method which allows tomographic representation of the strength of the damaged and treated areas. This paper describes the experimental methodology and presents results from laboratory experiments as well as a case study.
文摘Objective: To introduce the concept that there might be “nothing to smell” to the Brief Smell Identification Test (B-SIT), with a view to masking olfactory deficits, particularly from healthy control participants in research studies. Methods: Seventy-one elderly individuals, healthy for their age, were recruited to the study. They were blindfolded and carried out a modified B-SIT where one item had been replaced with a placebo, and one odour alternative answer to three other items was replaced by the alternative “none/other” (actual odour unchanged). Results: There was no overall difference in the median or mean score achieved by the cohort compared to results obtained previously using the conventional B-SIT. The replacement of the item “turpentine” with a placebo resulted in an improved score for the item in a Norwegian setting. The overall scores were not improved. Conclusions: It is possible to introduce the concept that there may be “nothing to smell” to the B-SIT without compromising the test for healthy control individuals. This may be a more appropriate approach to olfactory testing of control individuals or patients with suspected early neurodegenerative diseases.
基金supported by Stability Supports Research Project of Treasury Department(No.197801)Talent Fund of CIAE(No.219213)。
文摘Experimental scratch tests and first-principles calculations were used to investigate the adhesion property of AlCrNbSiTi high-entropy alloy(HEA)coatings on zirconium substrates.AlCrNbSiTi HEA and Cr coatings were deposited on Zr alloy substrates using multi-arc ion plating technology,and scratch tests were subsequently conducted to estimate the adhesion property of the coatings.The results indicated that Cr coatings had better adhesion strength than HEA coatings,and the HEA coatings showed brittleness.The special quasi-random structure approach was used to build HEA models,and Cr/Zr and HEA/Zr interface models were employed to investigate the cohesion between the coatings and Zr substrate using first-principles calculations.The calculated interface energies showed that the cohesion between the Cr coating and the Zr substrate was stronger than that of the HEA coating with Zr.In contrary to Al or Si in the HEA coating,Cr,Nb,and Ti atoms binded strongly with Zr substrate.Based on the calculated elastic constants,it was found that low Cr and high Al content decreased the mechanical performances of HEA coatings.Finally,this study demonstrated the utilization of a combined approach involving first-principles calculations and experimental studies for future HEA coating development.
