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The high‐temperature creep–fatigue (CF) interaction on the service damage of P92 welded joint was uncovered based on the evolution of local creep behaviour by nanoindentation. The creep resistance and high‐angle grain boundary (HAGB) distributions of the different regions of welded joint were investigated for the specimens under individual creep (stress relaxation [RS]), fatigue and CF loadings interrupted at lifetime fractions of 10%, 20%, 30%, 60% and 100%. According to structure evolution including the changes of HAGB and dislocation densities during high‐temperature deformation, the local variation mechanism of creep behaviour at different microstructural zones was systematically discussed.
Yuxuan Song; Furao Qin; Jianan Chen; Zhouxin Pan; Xianwei Huang; Zhenyu Ding; Zengliang Gao; Taihua Zhang; Yi Ma. On the microstructural evolution and room‐temperature creep behaviour of 9%Cr steel weld joint under prior creep–fatigue interaction. Fatigue & Fracture of Engineering Materials & Structures 2020, 44, 444 -460.
AMA StyleYuxuan Song, Furao Qin, Jianan Chen, Zhouxin Pan, Xianwei Huang, Zhenyu Ding, Zengliang Gao, Taihua Zhang, Yi Ma. On the microstructural evolution and room‐temperature creep behaviour of 9%Cr steel weld joint under prior creep–fatigue interaction. Fatigue & Fracture of Engineering Materials & Structures. 2020; 44 (2):444-460.
Chicago/Turabian StyleYuxuan Song; Furao Qin; Jianan Chen; Zhouxin Pan; Xianwei Huang; Zhenyu Ding; Zengliang Gao; Taihua Zhang; Yi Ma. 2020. "On the microstructural evolution and room‐temperature creep behaviour of 9%Cr steel weld joint under prior creep–fatigue interaction." Fatigue & Fracture of Engineering Materials & Structures 44, no. 2: 444-460.
Subsurface damage (SSD) introduced from abrasive machining significantly degrades the reliability and lifetime of glass ceramics. In this work, nanoindentation tests were performed on the cross section near the lapped surface to determine the nanomechanical properties of subsurface layer of a lapped BK7. Remarkable differences were found between SSD layer and its bulk counterpart in terms of load-displacement characteristics and nanomechanical response. The nanomechanical parameters (hardness and elastic modulus) of subsurface layer follow an exponential descending trend with the shortening of distance from lapped surface, which is consistent with the increase of crack density. The ratio of hardness to elastic modulus decreases exponentially with increasing subsurface depth until it reaches bulk material, which suggests that SSD layer has lower plasticity. Furthermore, the crack distribution becomes a critical parameter for characterizing the hardness gradient in SSD layer.
Huadong Wang; Yi Ma; Guangjian Peng; Wei Hang; Weifeng Jiang; Heng Chen; Chengwu Wang; Julong Yuan; Taihua Zhang. Evaluation of subsurface damage layer of BK7 glass via cross-sectional surface nanoindentation. Precision Engineering 2020, 67, 293 -300.
AMA StyleHuadong Wang, Yi Ma, Guangjian Peng, Wei Hang, Weifeng Jiang, Heng Chen, Chengwu Wang, Julong Yuan, Taihua Zhang. Evaluation of subsurface damage layer of BK7 glass via cross-sectional surface nanoindentation. Precision Engineering. 2020; 67 ():293-300.
Chicago/Turabian StyleHuadong Wang; Yi Ma; Guangjian Peng; Wei Hang; Weifeng Jiang; Heng Chen; Chengwu Wang; Julong Yuan; Taihua Zhang. 2020. "Evaluation of subsurface damage layer of BK7 glass via cross-sectional surface nanoindentation." Precision Engineering 67, no. : 293-300.
Recently, instrumental nanoindentation has been widely applied to detect time-dependent plastic deformation or creep behavior in numerous materials, particularly thin films and heterogeneous materials. However, deformation mechanism at nanoindentation holding stage has not been well revealed hitherto. In the current work, nanoindentation holding tests with high loads were performed on a brittle LiTaO3 single crystal. The surface morphologies of residual impressions with various holding times were investigated. It was indicated that generation of secondary cracks and propagation of both main and secondary cracks were the dominating mechanism for time-dependent plastic deformation at the initial holding stage, and the density and length of cracks were invariable at the steady-state holding stage, which suggested a nonlocalized plastic deformation beneath the indenter. It could be concluded that time-dependent plastic deformation of brittle ceramic under nanoindentation is composed of instant cracking as the continuation of loading sequence and homogeneous creep flow by high shear-compression stress at room temperature.
Shengyun Zhou; Xianwei Huang; Congda Lu; Yunfeng Liu; Taihua Zhang; Yi Ma. Revealing the Plastic Mode of Time-Dependent Deformation of a LiTaO3 Single Crystal by Nanoindentation. Micromachines 2020, 11, 878 .
AMA StyleShengyun Zhou, Xianwei Huang, Congda Lu, Yunfeng Liu, Taihua Zhang, Yi Ma. Revealing the Plastic Mode of Time-Dependent Deformation of a LiTaO3 Single Crystal by Nanoindentation. Micromachines. 2020; 11 (9):878.
Chicago/Turabian StyleShengyun Zhou; Xianwei Huang; Congda Lu; Yunfeng Liu; Taihua Zhang; Yi Ma. 2020. "Revealing the Plastic Mode of Time-Dependent Deformation of a LiTaO3 Single Crystal by Nanoindentation." Micromachines 11, no. 9: 878.
Zamak 3 alloy treatment by sliding-friction treatment (SFT) was investigated by nanoindentation to explore the influence of microstructure and strain rate on nanoscale deformation at room temperature. The results show that obvious material softening occurs in the ultrafine-grained (UFG) Zn alloy and strain-hardening happens in the twinning-deformed layer, respectively. It can be concluded that almost constant values of V in the UFG Zn alloy contribute to the dislocations moving along the grain boundary (GB) not cross the grain interior. In the twinning-deformed layer, the highly frequent dislocation–twinning boundary (TB) interactions are responsible for subsequent inverse Cottrell–Stokes at lower stress, which is quite different from dislocation–dislocation reaction inside the grain in their coarse-grained (CG) counterpart.
Jiangjiang Hu; Shuo Sun; Wei Zhang; Guangjian Peng; Shuang Han; Xu Sun; Yusheng Zhang; Taihua Zhang. Softening Behaviors of Severely Deformed Zn Alloy Studied by the Nanoindentation. Coatings 2020, 10, 803 .
AMA StyleJiangjiang Hu, Shuo Sun, Wei Zhang, Guangjian Peng, Shuang Han, Xu Sun, Yusheng Zhang, Taihua Zhang. Softening Behaviors of Severely Deformed Zn Alloy Studied by the Nanoindentation. Coatings. 2020; 10 (9):803.
Chicago/Turabian StyleJiangjiang Hu; Shuo Sun; Wei Zhang; Guangjian Peng; Shuang Han; Xu Sun; Yusheng Zhang; Taihua Zhang. 2020. "Softening Behaviors of Severely Deformed Zn Alloy Studied by the Nanoindentation." Coatings 10, no. 9: 803.
To evaluate the mechanical properties of structures in service, a portable micro-indentation device was developed and built. The basic design principle of the indentation device, i.e. measurement of the indentation depth and the indentation force with sufficient accuracy, was discussed. To avoid using load cell to decrease the machine compliance, a new method that using the current through voice coil motor to calculate the indentation force was proposed. After analyzing the equivalent mechanical model of the developed device, an eddy current displacement sensor was installed on the device to improve the measurement accuracy of indentation depth. Indentation tests were performed on polymethylmethacrylate (PMMA) and unplasticized polyvinyl chloride (UPVC) with the developed device and the commercial indentation device ZHU2.5 to demonstrate the validity and accuracy of the developed micro-indentation device.
Guangjian Peng; Fenglei Xu; Jianfeng Chen; Yahao Hu; Huadong Wang; Taihua Zhang. A cost-effective voice coil motor-based portable micro-indentation device for in situ testing. Measurement 2020, 165, 108105 .
AMA StyleGuangjian Peng, Fenglei Xu, Jianfeng Chen, Yahao Hu, Huadong Wang, Taihua Zhang. A cost-effective voice coil motor-based portable micro-indentation device for in situ testing. Measurement. 2020; 165 ():108105.
Chicago/Turabian StyleGuangjian Peng; Fenglei Xu; Jianfeng Chen; Yahao Hu; Huadong Wang; Taihua Zhang. 2020. "A cost-effective voice coil motor-based portable micro-indentation device for in situ testing." Measurement 165, no. : 108105.
Residual stresses, existed in engineering structures, could significantly influence the mechanical properties of structures. Accurate and non-destructive evaluation of the non-equibiaxial residual stresses in these structures is of great value for predicting their mechanical performance. In this work, investigating the mechanical behaviors of instrumented spherical indentation on stressed samples revealed that non-equibiaxial residual stresses could shift the load-depth curve upwards or downwards and cause the residual indentation imprint to be an elliptical one. Through theoretical, experimental, and finite element (FE) analyses, two characteristic indentation parameters, i.e., the relative change in loading curvature and the asymmetry factor of the residual indentation imprint, were found to have optimal sensitivity to residual stresses at a depth of 0.01R (R is the radius of spherical indenter). With the aid of dimensional analysis and FE simulations, non-equibiaxial residual stresses were quantitatively correlated with these two characteristic indentation parameters. The spherical indentation method was then proposed to evaluate non-equibiaxial residual stress based on these two correlations. Applications were illustrated on metallic samples (AA 7075-T6 and AA 2014-T6) with various introduced stresses. Both the numerical and experimental verifications demonstrated that the proposed method could evaluate non-equibiaxial surface residual stresses with reasonable accuracy.
Guangjian Peng; Fenglei Xu; Jianfeng Chen; Huadong Wang; Jiangjiang Hu; Taihua Zhang. Evaluation of Non-Equibiaxial Residual Stresses in Metallic Materials via Instrumented Spherical Indentation. Metals 2020, 10, 440 .
AMA StyleGuangjian Peng, Fenglei Xu, Jianfeng Chen, Huadong Wang, Jiangjiang Hu, Taihua Zhang. Evaluation of Non-Equibiaxial Residual Stresses in Metallic Materials via Instrumented Spherical Indentation. Metals. 2020; 10 (4):440.
Chicago/Turabian StyleGuangjian Peng; Fenglei Xu; Jianfeng Chen; Huadong Wang; Jiangjiang Hu; Taihua Zhang. 2020. "Evaluation of Non-Equibiaxial Residual Stresses in Metallic Materials via Instrumented Spherical Indentation." Metals 10, no. 4: 440.
We investigated the characteristic of first pop-in event under spherical nanoindentation in the typical orientation (0 1 1¯ 2), i.e., Y-42° plane of a LiTaO3 single crystal. Three spherical tips with different radii were adopted to probe yield stress and its stochastic behavior as the incipient plasticity occurred. The values of yield stress were 10.75 ± 0.78, 6.3 ± 0.44 and 5.36 ± 0.4 GPa, which were equivalent to E/14, E/30 and E/36 under spherical tips with radii of 0.76, 2.95 and 9.8 μm, respectively. The occurrence of incipient plasticity exhibited a uniform and scattering distribution in a wide range under all the tips. The activation volumes of plastic unit were computed based on the statistical distribution of yield stress, which were 6, 12 and 12 Å3 for 0.76, 2.95 and 9.8 μm tips. A strong indentation size effect was revealed on the threshold stress for evoking incipient plasticity and the critical volume for plastic unit activation. Furthermore, incipient plasticity of LiTaO3 single crystal was confirmed to be loading history-independent. The obtained yield stress and its statistic distribution were similar within the range of loading rate from 0.125 to 2 mN/s.
Yi Ma; Xianwei Huang; Wei Hang; Min Liu; Yuxuan Song; Julong Yuan; Taihua Zhang. Nanoindentation size effect on stochastic behavior of incipient plasticity in a LiTaO3 single crystal. Engineering Fracture Mechanics 2020, 226, 106877 .
AMA StyleYi Ma, Xianwei Huang, Wei Hang, Min Liu, Yuxuan Song, Julong Yuan, Taihua Zhang. Nanoindentation size effect on stochastic behavior of incipient plasticity in a LiTaO3 single crystal. Engineering Fracture Mechanics. 2020; 226 ():106877.
Chicago/Turabian StyleYi Ma; Xianwei Huang; Wei Hang; Min Liu; Yuxuan Song; Julong Yuan; Taihua Zhang. 2020. "Nanoindentation size effect on stochastic behavior of incipient plasticity in a LiTaO3 single crystal." Engineering Fracture Mechanics 226, no. : 106877.
Relying on nanoindentation technology, we investigated the elastic-to-plastic transition via first pop-in event and estimated the corresponding shear stress for incipient plasticity, i.e., yielding in the three typical orientations, i.e., X-112°, Y-36°, and Y-42° planes. The occurrence of incipient plasticity exhibited a stochastic distribution in a wide range for the three orientations. Accordingly, the obtained values of yield stress were uniform and scattered in the range from about 4 to 7 GPa for LiTaO3 single crystal. The orientation effect on yield stress at the nano-scale was revealed to be insignificant in LiTaO3 single crystal. The yield stresses were 5.44 ± 0.41, 5.74 ± 0.59, and 5.34 ± 0.525 GPa for the X-112°, Y-36°, and Y-42° planes, respectively. The activation volumes of dislocation nucleation were computed based on the cumulative distribution of yield stress, which were 12 Å3, 8 Å3, and 9 Å3 for the X-112°, Y-36°, and Y-42° planes. The results indicated that point-like defects could be the source of plastic initiation on the surface of LiTaO3 single crystal.
Yi Ma; Xianwei Huang; Yuxuan Song; Wei Hang; Julong Yuan; Taihua Zhang. Orientation-Independent Yield Stress and Activation Volume of Dislocation Nucleation in LiTaO3 Single Crystal by Nanoindentation. Materials 2019, 12, 2799 .
AMA StyleYi Ma, Xianwei Huang, Yuxuan Song, Wei Hang, Julong Yuan, Taihua Zhang. Orientation-Independent Yield Stress and Activation Volume of Dislocation Nucleation in LiTaO3 Single Crystal by Nanoindentation. Materials. 2019; 12 (17):2799.
Chicago/Turabian StyleYi Ma; Xianwei Huang; Yuxuan Song; Wei Hang; Julong Yuan; Taihua Zhang. 2019. "Orientation-Independent Yield Stress and Activation Volume of Dislocation Nucleation in LiTaO3 Single Crystal by Nanoindentation." Materials 12, no. 17: 2799.
Nanoindentation technology has been widely adopted to study creep behavior in small regions. However, nanoindentation creep behavior of metallic glass is still not well understood. In the present work, we investigated nanoindentation size effects on creep deformation in a Zr-based bulk metallic glass at room temperature. The total creep strain and strain rate of steady-state creep were gradually decreased with increasing holding depth under a Berkovich indenter, indicating a length-scale-dependent creep resistance. For a spherical indenter, creep deformations were insignificant in elastic regions and then greatly enhanced by increasing holding strain in plastic regions. Strain rate sensitivities (SRS) decreased with increasing holding depth and holding strain at first, and then stabilized as holding depth was beyond about 500 nm for both indenters. SRS values were 0.4–0.5 in elastic regions, in which atomic diffusion and free volume migration could be the creep mechanism. On the other hand, evolution of the shear transformation zone was suggested as a creep mechanism in plastic regions, and the corresponding SRS values were in the range of 0.05 to 0.3.
Z. Y. Ding; Y. X. Song; Y. Ma; X. W. Huang; T. H. Zhang. Nanoindentation Investigation on the Size-Dependent Creep Behavior in a Zr-Cu-Ag-Al Bulk Metallic Glass. Metals 2019, 9, 613 .
AMA StyleZ. Y. Ding, Y. X. Song, Y. Ma, X. W. Huang, T. H. Zhang. Nanoindentation Investigation on the Size-Dependent Creep Behavior in a Zr-Cu-Ag-Al Bulk Metallic Glass. Metals. 2019; 9 (5):613.
Chicago/Turabian StyleZ. Y. Ding; Y. X. Song; Y. Ma; X. W. Huang; T. H. Zhang. 2019. "Nanoindentation Investigation on the Size-Dependent Creep Behavior in a Zr-Cu-Ag-Al Bulk Metallic Glass." Metals 9, no. 5: 613.
The crystal orientation effect on mechanical heterogeneity of LiTaO3 single crystals is well known, whilst the time-dependent plastic behavior, i.e., creep is still short of understanding. Relying on nanoindentation technology, we systematically studied room-temperature creep flows at various holding depths (100 nm to 1100 nm) in three typical orientations namely the X-112°, Y-36° and Y-42° planes. Creep resistance was much stronger in the X-112° plane than the others. In the meanwhile, creep features were similar in the Y-36° and Y-42° planes. The orientation effect on creep deformation was consistent with that on hardness. The nanoindentation length scale played an important role in creep deformation that creep strains were gradually decreased with the holding depth in all the planes. Based on strain rate sensitivity and yield stress, the activation volumes of dislocation nucleation were computed at various nanoindentation depths. The activation volumes ranged from 5 Å3 to 23 Å3 for the Y-36° and Y-42° planes, indicating that a point-like defect could be the source of plastic initiation. In the X-112° plane, the activation volume was between 6 Å3 and 83 Å3. Cooperative migration of several atoms could also be the mechanism of dislocation activation at deep nanoindentation.
Yi Ma; Xianwei Huang; Yuxuan Song; Wei Hang; Taihua Zhang. Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation. Materials 2019, 12, 1683 .
AMA StyleYi Ma, Xianwei Huang, Yuxuan Song, Wei Hang, Taihua Zhang. Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation. Materials. 2019; 12 (10):1683.
Chicago/Turabian StyleYi Ma; Xianwei Huang; Yuxuan Song; Wei Hang; Taihua Zhang. 2019. "Room-Temperature Creep Behavior and Activation Volume of Dislocation Nucleation in a LiTaO3 Single Crystal by Nanoindentation." Materials 12, no. 10: 1683.
Friction stir welding (FSW) is a promising welding method for welding dissimilar materials without using welding flux. In the present work, 5A06-H112 and 6061-T651 aluminium alloys were successfully welded by friction stir welding with forced air cooling (FAC) and natural cooling (NC). Nanoindentation tests and microstructure characterisations revealed that forced air cooling, which can accelerate the cooling process and suppress the coarsening of grains and the dissolution of precipitate phases, contributes to strengthening and narrowing the weakest area of the joint. The tensile strength of joints with FAC were commonly improved by 10% compared to those with NC. Scanning electron microscopy (SEM) images of the fracture surface elucidated that FSW with FAC tended to increase the number and reduce the size of the dimples. These results demonstrated the advantages of FSW with FAC in welding heat-sensitive materials and provide fresh insight into welding industries.
Guangjian Peng; Qi Yan; Jiangjiang Hu; Peijian Chen; Zhitong Chen; Taihua Zhang. Effect of Forced Air Cooling on the Microstructures, Tensile Strength, and Hardness Distribution of Dissimilar Friction Stir Welded AA5A06-AA6061 Joints. Metals 2019, 9, 304 .
AMA StyleGuangjian Peng, Qi Yan, Jiangjiang Hu, Peijian Chen, Zhitong Chen, Taihua Zhang. Effect of Forced Air Cooling on the Microstructures, Tensile Strength, and Hardness Distribution of Dissimilar Friction Stir Welded AA5A06-AA6061 Joints. Metals. 2019; 9 (3):304.
Chicago/Turabian StyleGuangjian Peng; Qi Yan; Jiangjiang Hu; Peijian Chen; Zhitong Chen; Taihua Zhang. 2019. "Effect of Forced Air Cooling on the Microstructures, Tensile Strength, and Hardness Distribution of Dissimilar Friction Stir Welded AA5A06-AA6061 Joints." Metals 9, no. 3: 304.
Room-temperature creep tests are performed at the plastic regions of two different metallic glassy films under Berkovich nanoindetation. Relying on the strain rate sensitivity of the steady-state creep curve, shear transformation zone (STZ) size is estimated based on the cooperative shear model (CSM). By applying various indentation depths, loading rates, and holding times, the testing effects on the STZ size of metallic glasses are systematically studied. Experimental results indicate that STZ size is greatly increased with increased indentation depth and shortened holding time. Meanwhile, STZ size is weakly dependent on the loading history. Both the intrinsic and extrinsic reasons are discussed, to reveal the testing effects on the nanoindentation creep flow and STZ size.
Yi Ma; Yuxuan Song; Xianwei Huang; Zhongli Chen; Taihua Zhang. Testing Effects on Shear Transformation Zone Size of Metallic Glassy Films Under Nanoindentation. Micromachines 2018, 9, 636 .
AMA StyleYi Ma, Yuxuan Song, Xianwei Huang, Zhongli Chen, Taihua Zhang. Testing Effects on Shear Transformation Zone Size of Metallic Glassy Films Under Nanoindentation. Micromachines. 2018; 9 (12):636.
Chicago/Turabian StyleYi Ma; Yuxuan Song; Xianwei Huang; Zhongli Chen; Taihua Zhang. 2018. "Testing Effects on Shear Transformation Zone Size of Metallic Glassy Films Under Nanoindentation." Micromachines 9, no. 12: 636.
Aluminum alloy AA 6061-T651 and 5A06-H112 rolled plates were successfully welded by friction stir welding (FSW) at three rotation speeds of 600, 900, and 1200 rpm with two transverse speeds of 100 and 150 mm/min. Mechanical properties and strain field evolution of FSW AA 6061-AA 5A06 were characterized by the uniaxial tension and digital image correlation (DIC) tests. Furthermore, the hardness distribution map of whole cross section was obtained via the nanoindentation method with 700 indents. Both DIC and nanoindentation results reveal that the heat-affected zone (HAZ) of AA 6061 alloy is the softest area in the weldment, and the fracture happens in this region. The microstructure evolution characterized by electron-backscatter diffraction (EBSD) indicates that the continuous dynamic recrystallization is the primary grain structure evolution in the stirring zone, and the grain refinement helps improve the mechanical properties. Analyses of the micro- and macrofeatures of the fracture surfaces via scanning electron microscopy (SEM) and optical microscope suggest that the increasing of heat input could enlarge the size of HAZ and reduce the slant angle of HAZ and thus lead the fracture angle to decrease and cause the dimples change from inclined ones to normal ones.
Guangjian Peng; Yi Ma; Jiangjiang Hu; Weifeng Jiang; Yong Huan; Zhitong Chen; Taihua Zhang. Nanoindentation Hardness Distribution and Strain Field and Fracture Evolution in Dissimilar Friction Stir-Welded AA 6061-AA 5A06 Aluminum Alloy Joints. Advances in Materials Science and Engineering 2018, 2018, 1 -11.
AMA StyleGuangjian Peng, Yi Ma, Jiangjiang Hu, Weifeng Jiang, Yong Huan, Zhitong Chen, Taihua Zhang. Nanoindentation Hardness Distribution and Strain Field and Fracture Evolution in Dissimilar Friction Stir-Welded AA 6061-AA 5A06 Aluminum Alloy Joints. Advances in Materials Science and Engineering. 2018; 2018 ():1-11.
Chicago/Turabian StyleGuangjian Peng; Yi Ma; Jiangjiang Hu; Weifeng Jiang; Yong Huan; Zhitong Chen; Taihua Zhang. 2018. "Nanoindentation Hardness Distribution and Strain Field and Fracture Evolution in Dissimilar Friction Stir-Welded AA 6061-AA 5A06 Aluminum Alloy Joints." Advances in Materials Science and Engineering 2018, no. : 1-11.
For instrumented spherical indentation, the presence of equibiaxial residual stress in a material will lead the indentation load–depth curve to shift upward or downward. The load differences between the stressed and stress-free curves were used to estimate the equibiaxial residual stress. Using dimensional analysis and finite element simulations, the equibiaxial residual stress was related to the elastic–plastic parameters and the relative load difference at a fixed normalized indentation depth (h/R = 0.1). Based on these expressions, and together with the method for determining elastic–plastic parameters established in our previous work, an integrated method was proposed to estimate the equibiaxial residual stress and elastic–plastic parameters of metals simultaneously via instrumented spherical indentation. This method avoids preknowledge of the yield strength and measuring the contact area. Applications were illustrated on Al 2024, Al 7075, and Ti Grade 5 with introduced stresses. By comparing the results determined by this integrated method with the reference values, the maximum relative error is generally within ±10% for the yield strength, within ±15% for the elastic modulus, and within ±20% for the equibiaxial residual stress.
Guangjian Peng; Zhike Lu; Yi Ma; Yihui Feng; Yong Huan; Taihua Zhang. Spherical indentation method for estimating equibiaxial residual stress and elastic–plastic properties of metals simultaneously. Journal of Materials Research 2018, 33, 884 -897.
AMA StyleGuangjian Peng, Zhike Lu, Yi Ma, Yihui Feng, Yong Huan, Taihua Zhang. Spherical indentation method for estimating equibiaxial residual stress and elastic–plastic properties of metals simultaneously. Journal of Materials Research. 2018; 33 (8):884-897.
Chicago/Turabian StyleGuangjian Peng; Zhike Lu; Yi Ma; Yihui Feng; Yong Huan; Taihua Zhang. 2018. "Spherical indentation method for estimating equibiaxial residual stress and elastic–plastic properties of metals simultaneously." Journal of Materials Research 33, no. 8: 884-897.
Nanoindentation tests were performed at room temperature, to study the coupling effects of grain size and strain rate on the indentation size effect (ISE), pop-in effect and creep behavior of refine-grained AZ31 alloys. The relatively inconspicuous ISE of the refine-grained AZ31 alloys compared with its coarse-grained (CG) counterpart is the result of more density of statistically stored dislocations involved in the plastic deformation. The gradually disappeared pop-in effects in the nanocrystalline (NC)/ultrafine-grained (UFG) AZ31 are associated with no/few deformation twinning involved in the plastic deformation. For the NC/UFG AZ31, the highly unstable dislocation absorption and interactions between dislocation and high-angle GBs are responsible for the primary and latter nanoindentation creep behaviors, respectively. While for the CG+twinning/CG AZ31, the relevant mechanisms are the relatively stable dislocation motion and interactions between dislocation and low-angle GBs.
Jiangjiang Hu; Wei Zhang; Guangjian Peng; Taihua Zhang; Yusheng Zhang. Nanoindentation deformation of refine-grained AZ31 magnesium alloy: Indentation size effect, pop-in effect and creep behavior. Materials Science and Engineering: A 2018, 725, 522 -529.
AMA StyleJiangjiang Hu, Wei Zhang, Guangjian Peng, Taihua Zhang, Yusheng Zhang. Nanoindentation deformation of refine-grained AZ31 magnesium alloy: Indentation size effect, pop-in effect and creep behavior. Materials Science and Engineering: A. 2018; 725 ():522-529.
Chicago/Turabian StyleJiangjiang Hu; Wei Zhang; Guangjian Peng; Taihua Zhang; Yusheng Zhang. 2018. "Nanoindentation deformation of refine-grained AZ31 magnesium alloy: Indentation size effect, pop-in effect and creep behavior." Materials Science and Engineering: A 725, no. : 522-529.
Nanolaminates consisting of individual amorphous Cu-Zr-Al layers and nanocrystalline Cu layers on Si substrates were prepared by alternatively magnetron sputtering and hardness measurements were conducted upon nanoindentation with a standard Berkovich indenter. Indentation hardness showed a strong size effect in single Cu-Zr-Al film, its decline trend was slower in the nanolaminates with thinner amorphous layers. While experimental hardness was obviously below the expected rule-of-mixture value for all the nanolaminates. Finite element modelling (FEM) analysis was performed in each sample to explore stress distribution beneath indenter. A higher proportion of Cu layers has been involved into plastic region than the nominal value. Besides, interfacial barrier strength was estimated for each sample. The experimental results could be well described by the modified rule of mixture integrated with true ratio of Cu to Cu-Zr-Al in plastic region and the interface strengthen effect.
Y. Ma; G.J. Peng; H. Chen; W.F. Jiang; T.H. Zhang. On the nanoindentation hardness of Cu-Zr-Al/Cu nanolaminates. Journal of Non-Crystalline Solids 2018, 482, 208 -212.
AMA StyleY. Ma, G.J. Peng, H. Chen, W.F. Jiang, T.H. Zhang. On the nanoindentation hardness of Cu-Zr-Al/Cu nanolaminates. Journal of Non-Crystalline Solids. 2018; 482 ():208-212.
Chicago/Turabian StyleY. Ma; G.J. Peng; H. Chen; W.F. Jiang; T.H. Zhang. 2018. "On the nanoindentation hardness of Cu-Zr-Al/Cu nanolaminates." Journal of Non-Crystalline Solids 482, no. : 208-212.
Nanoindentation morphologies of crystalline copper have been probed at the grain scale. Experimental tests have been conducted on nanocrystalline (NC), ultrafine-grained (UFG), and coarse-grained (CG) copper samples with a new Berkvoich indenter at the strain rate of 0.04/s without holding time at an indentation depth of 2000 nm at room temperature. As the grain size increases, the height of the pile-up around the residual indentation increases and then exhibits a slightly decrease in the CG Cu. The maximum of the pile-up in the CG Cu obviously deviates from the center of the indenter sides. Our analysis has revealed that the dislocation motion and GB activities in the NC Cu, some cross- and multiple-slip dislocations inside the larger grain in the UFG Cu, and forest dislocations from the intragranular Frank-Read sources in the CG Cu would directly induce this distinct pile-up effect.
Jiangjiang Hu; Yusheng Zhang; Weiming Sun; Taihua Zhang. Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size. Crystals 2017, 8, 9 .
AMA StyleJiangjiang Hu, Yusheng Zhang, Weiming Sun, Taihua Zhang. Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size. Crystals. 2017; 8 (1):9.
Chicago/Turabian StyleJiangjiang Hu; Yusheng Zhang; Weiming Sun; Taihua Zhang. 2017. "Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size." Crystals 8, no. 1: 9.
Discontinuous shear thickening observed in many dense suspensions is rather complicated but takes place as a transient. Its details after jamming are still not clear. By using a modified rheometer with an analog-to-digital converter, we show that there are three amplitude regimes of shear strain after jamming. First, the shear modulus and the force chain angle increase with strain; the jammed state gradually deepens. Second, the jammed state is stable against a further increase in shear stress; the force chain angle is constant and the force network is stable. Third, the jammed state cannot resist a further increase in shear stress; with the increase in the force chain angle, the force chain network is broken.
Weifeng Jiang; Guangjian Peng; Yi Ma; Heng Chen; Jiangjiang Hu; Chao Jia; Taihua Zhang. Measuring the mechanical responses of a jammed discontinuous shear-thickening fluid. Applied Physics Letters 2017, 111, 201906 .
AMA StyleWeifeng Jiang, Guangjian Peng, Yi Ma, Heng Chen, Jiangjiang Hu, Chao Jia, Taihua Zhang. Measuring the mechanical responses of a jammed discontinuous shear-thickening fluid. Applied Physics Letters. 2017; 111 (20):201906.
Chicago/Turabian StyleWeifeng Jiang; Guangjian Peng; Yi Ma; Heng Chen; Jiangjiang Hu; Chao Jia; Taihua Zhang. 2017. "Measuring the mechanical responses of a jammed discontinuous shear-thickening fluid." Applied Physics Letters 111, no. 20: 201906.
At room temperature, the indentation morphologies of crystalline copper with different grain size including nanocrystalline (NC), ultrafine-grained (UFG) and coarse-grained (CG) copper were studied by nanoindentation at the strain rate of 0.04/s without holding time at indentation depth of 2000 nm. As the grain size increasing, the height of the pile-up around the residual indentation increases and then has a slightly decrease in the CG Cu, While the area of the pile-up increases constantly. Our analysis has revealed that the dislocation motion and GB activities in the NC Cu, some cross- and multiple-slips dislocation insides the larger grain in the UFG Cu, and forest dislocations from the intragranular Frank-Read sources in the CG Cu, would directly induce these distinct pile-up effect.
Jiangjiang Hu; Weiming Sun; Taihua Zhang; Yusheng Zhang. Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size. 2017, 1 .
AMA StyleJiangjiang Hu, Weiming Sun, Taihua Zhang, Yusheng Zhang. Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size. . 2017; ():1.
Chicago/Turabian StyleJiangjiang Hu; Weiming Sun; Taihua Zhang; Yusheng Zhang. 2017. "Nanoindentation-Induced Pile-Up in the Residual Impression of Crystalline Cu with Different Grain Size." , no. : 1.
In order to investigate the effect of applied stress on mechanical properties in metallic glasses, nanoindentation tests were conducted on elastically bent Zr-Cu-Ag-Al metallic glasses with two different structure states. From spherical P-h curves, elastic modulus was found to be independent on applied stress. Hardness decreased by ~8% and ~14% with the application of 1.5% tensile strain for as-cast and 650 K annealed specimens, while it was slightly increased at the compressive side. Yield stress could be obtained from the contact pressure at first pop-in position with a conversion coefficient. The experimental result showed a symmetrical effect of applied stress on strengthening and a reduction of the contact pressure at compressive and tensile sides. It was observed that the applied stress plays a negligible effect on creep deformation in as-cast specimen. While for the annealed specimen, creep deformation was facilitated by applied tensile stress and suppressed by applied compressive stress. Strain rate sensitivities (SRS) were calculated from steady-state creep, which were constant for as-cast specimen and strongly correlated with applied stress for the annealed one. The more pronounced effect of applied stress in the 650 K annealed metallic glass could be qualitatively explained through the variation of the shear transformation zone (STZ) size.
Heng Chen; Taihua Zhang; Yi Ma. Effect of Applied Stress on the Mechanical Properties of a Zr-Cu-Ag-Al Bulk Metallic Glass with Two Different Structure States. Materials 2017, 10, 711 .
AMA StyleHeng Chen, Taihua Zhang, Yi Ma. Effect of Applied Stress on the Mechanical Properties of a Zr-Cu-Ag-Al Bulk Metallic Glass with Two Different Structure States. Materials. 2017; 10 (7):711.
Chicago/Turabian StyleHeng Chen; Taihua Zhang; Yi Ma. 2017. "Effect of Applied Stress on the Mechanical Properties of a Zr-Cu-Ag-Al Bulk Metallic Glass with Two Different Structure States." Materials 10, no. 7: 711.