Application of wavelet to strength log from scratch test

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.

Determination of the Fracture Toughness of Glasses via Scratch Tests with a Vickers Indenter

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.

Adhesion property of AlCrNbSiTi high-entropy alloy coating on zirconium:experimental and theoretical studies

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.

A method for predicting critical load evaluating adhesion of coatings in scratch testing

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.

Nanoscratch behaviors of La_(0.7)Sr_(0.3)MnO_(3+δ) thin films

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.

Evaluation of the Effectiveness of MasonryConsolidation Treatments Based on ScratchingTomography

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.

关节镜治疗顽固性网球肘临床疗效观察

目的探讨在关节镜下行单纯清理术治疗顽固性网球肘的临床疗效,为关节镜治疗顽固性网球肘提供临床依据。方法回顾性分析南昌市洪都中医院2016年-2017年收治的顽固性肱骨外上髁炎患者24例,在关节镜下行单纯清理肱骨外上髁伸肌肌腱止点病变组织。比较手术前后肘关节活动度,包括屈曲角度、旋前及旋后角度,并采用VAS评分、Mayo肘关节功能评分及患者满意度评价术后疗效。结果术后所有患者均获得随访,平均随访17.5个月。肘关节术前屈曲角度(91.4±6.3)°,旋前角度(60.4±5.3)°;术后屈曲角度(126.8±4.6)°,旋前角度(76.7±7.4)°。手术前后差异有统计学意义(P<0.05);而术前旋后角度(76.7±4.5)°,术后旋后角度(77.5±4.3)°,手术前后差异无统计学意义(P>0.05)。疼痛VAS评分分为术前休息时、术前活动时、术后休息时及术后活动时,手术前后比较差异有统计学意义(P<0.05)。术后Mayo肘关节功能评分较术前高。术后患者完全满意21例,基本满意3例,不满意0例,总满意率为100%。结论关节镜下依据Scratch Test原则行单纯清理术对治疗顽固性网球肘具有良好疗效,值得临床推广应用。

Study of the material removal mechanism of glass-ceramics based on consecutive incremental loading in ductile-regime grinding

Glass-ceramics have many excellent properties and are widely used in various fields. During the grinding process,the workpiece surface is typically subject to material removal by grit of incremental heights, which has rarely been the focus of research. As such, it is necessary to study the material removal mechanism of glass-ceramics under consecutive incremental loading, which more closely reflects the actual grinding process. In this paper,to analyze the plastic deformation and residual stress of lithium aluminosilicate(LAS) glass-ceramics, a finite element model is established based on the Drucker–Prager yield criterion for ductile regimes. A nano-scratch test was also conducted and the test results show that both the residual depth and residual stress increase with an increase in the number of increments, and that consecutive incremental loading promotes the plastic deformation of glass-ceramics and increases the residual stress of the material in the ductile-regime process. These findings provide guidance for achieving higher dimensional accuracy in the actual grinding of glass-ceramics parts.

Tribology Performance and Adhesive Strength Evaluation of TiAlSiN Coating

Scratch test and friction test were performed to evaluate the internal and external interface behaviors of TiAISiN coating, respectively. The critical compressive and shearing stress of coating failure during scratch test were calculated and the values are 30.84 MPa and 4.98 MPa respectively. The average friction coefficients of TiAISiN coat- ing against 2Crl2Ni4Mo3VNbN steel are 0.70 （sliding speed 50 m/rain）, 0.63 （sliding speed 100 m/min）, and 0.81 （sliding speed 150 m/min）. The elements diffusion was analyzed by EDS. A1 and Si element of coating material dif- fuse to the steel disc, except Ti element. The oxidation decreases with the increase of sliding speed, but the adhesion increases with the increase of sliding speed. More A1 element diffuses to the steel disc at the high sliding speed, but the diffusion of Si element keeps almost constant at dlfferent sliding speeds.

Assessment of inherent heterogeneity effect on continuous mechanical properties of shale via uniaxial compression and scratch test methods

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.

An Improvement on Adhesion of Sputtered TiC Coating to Steel Substrate

Introducing N_2 during sputtering and pre-oxidation of substrate were investigated to improve the adhesion of sputtered TiC coating to steel substrate. The results show that yeactive gas N_2 increases the adhesion of TiC coating to steel because of a graded interface existing between coating and substrate. The interaction of discharge plasma with the surface of substrate was discussed. Pre-oxidation of substrate is effective for improving the adhesion due to the fomation of FeTi0_3 which appeared as an inteylayer between coating and pre-oxidized substrate.

EVALUATION OF ADHESION AND PLASTICITY OF PVD FILMS

Evaluation of adhesion of PVD Ti and TiN films on steel A_3 was carried out with constant rate pulling test(CRPT)at 0.05 mm/min under simultaneous SEM observation. As a criterion,the critical elongations of the film/substrate system for the initial cracking and spelling of the film may be applied to evaluate the plasticity and adhesion of the film to substrate.The conventional scratch test was also made for evaluation of the adhesion for the same systems.Both methods give the coordinate assessment for all the systems. In addition,the influence of the films on the ultimate yield strength of the substrate was discussed and another criterion of conherent work was proposed for the evaluation.

Modification of the Brief Smell Identification Test by Introduction of a Placebo

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.

Coatings of needle/stripe-like fluoridated hydroxyapatite on H2O2-treated carbon/carbon composites prepared by induction heating and hydrothermal methods

A hydroxyapatite （HA） coating was achieved on H2O2-treated carbon/ carbon （C/C） composite through hydrothermally treating and induction heating deposited CaHPO4 coating in an ammonia solution under ultrasonic water bath. Then, this HA coating was placed in a NH4F solution and hydrothermally treated again to fabricate fluorinated hydroxyapatite （FHA） coatings for 24 h at 353, 373, 393 and 413 K, respectively. The structure, morphology and chemical composition of the HA and FHA coatings were characterized by SEM, XRD, EDS and FTIR, and the adhesiveness and chemical stability of these FHA coatings were examined by a scratch test and an immersion test, respectively. The results showed that the as-prepared FHA coatings contained needle-like or stripe-like crystals, different from those of the HA coating. As the fluoridation temperature rose, the adhesiveness of the FHA coating first increased from 34.8 to 40.9 N at a temperature between 353 and 393 K, and then decreased to 24.2 N at 413 K, while the dissolution rate of the FHA coating decreased steadily. The reasons for the property variation of the FHA coatings were proposed by analyzing the morphology, composition and structure of the coatings.