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Numerical study of pile-up in bulk metallic glass during spherical indentation

Science China(Physics,Mechanics & Astronomy) 2008年第4期51卷 379-386页

作者： AI Ke DAI LanHong State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100080China

pile-up around indenter is usually observed during instrumented indentation tests on bulk metallic glass. Neglecting the pile-up effect may lead to errors in evaluating hardness,Young’s modulus,stress-strain response,etc. Finite element analysis was employed to implement numerical simulation of spherical indentation tests on bulk metallic glass. A new model was proposed to describe the pile-up effect. By using this new model,the contact radius and hardness of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass were obtained under several different indenter loads with pile-up,and the results agree well with the data generated by numerical simulation.

关键词： bulk metallic glass spherical indenter pile-up contact radius hardness

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Influence of pile-up on nanoindentation measurements in Cu-2wt.%Be samples with precipitates

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Transactions of Nonferrous Metals Society of China 2019年第11期29卷 2340-2350页

作者： S.MONTECINOS S.TOGNANA W.SALGUEIRO IFIMAT Facultad de Ciencias ExactasUniversidad Nacional del Centro de la Provincia de Buenos AiresPinto 3997000 TandilArgentina Consejo Nacional de Investigaciones Científicas y Técnicas CONICET Av.Rivadavia 1917C1033AAJ Buenos AiresArgentina CIFICEN(UNCPBA-CICPBA-CONICET) Pinto 3997000 TandilArgentina Comisión de Investigaciones Científicas de la Provincia de Bs.As. Calle 526 entre 10 y 111900 La PlataArgentina

The influence of pile-up on the nanoindentation measurements in Cu 2wt.%Be samples with precipitates was carefully *** precipitates were formed by aging treatments for 1 h at different temperatures between 540 and 680 *** load depth curves were analyzed using the classical Oliver and Pharr method,and the obtained elastic modulus and hardness were compared with values estimated by other *** important level of pile-up was found in samples with precipitates and differences in the load depth curves were observed between the unaged and aged samples.A correction of the contact depth considering the pile-up proposed by Loubet was used for hardness *** the determination of the elastic modulus,an approach based on the relation between the ratio of unloading work to indentation total work,with the ratio H/Er(H is the hardness;Er is the reduced modulus),was employed.A specific relation between both parameters was developed.

关键词： pile-up nanoindentation measurement copper alloy precipitation microstructure mechanical properties

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Effects of elastic-plastic properties of materials on residual indentation impressions in nano-indentation using sharp indenter

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中国有色金属学会会刊：英文版 2012年第S3期22卷 585-595页

作者： Jung-Min LEE Chan-Joo LEE Kyung-Hun LEE Byung-Min KIM Dongnam Regional Division Korea Institute of Industrial Technology Precision Manufacturing Systems Division Pusan National University School of Mechanical Engineering Pusan National University

One of the primary features of nano-indentation technique is that the contact area induced by an indenter is indirectly measured by a relationship between the penetration depth and the known geometry of the ***,this indirect measurement occasionally leads to inaccurate properties of the indented *** objective of this study is to investigate the effects of E/σr and the strain hardening exponents n of materials on the behaviors of pile-up and sink-in in nano-indentation and to predict n values of materials from the residual indentation *** relations between the residual indentation profile and n value of the indented material were identified by dimensional ***,they were numerically formulated using FE analysis of nano-indentation for 140 different combinations of elastic-plastic parameters such as E,σy and *** parameters of hrp/hm,herp/hm,Rr/hm and HO&P/Hreal were introduced as various dimensionless parameters to represent and quantify the residual indentation profile after *** were subsequently characterized as dimensionless functions using n and E/σr ***,the validity of these functions was verified through 3D FE analysis of nano-indentation for Al 6061-T6 and AISI 1010 materials.

关键词： nano-indentation pile-up sink-in strain hardening exponent FE simulation

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The performance of out-of-time events of the follow-up X-ray telescope onboard Einstein probe

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Radiation Detection Technology and Methods 2024年第2期8卷 1148-1154页

作者： Hai-Sheng Zhao Juan Zhang Ju Guan Cheng-Kui Li Shu-Mei Jia Li-Ming Song Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of Sciences19B Yuquan RoadBeijing100049People’s Republic of China

Purpose:The purpose of this study is to investigate the performance of out-of-time events(OoT events)in the Follow-up X-ray Telescope(FXT)onboard the Einstein *** OoT events,registered on the PN-CCD during its readout time,can provide information on the sources,e.g.,spectral indices,and diagnose the behavior of ***:In order to analyze the characteristics of OoT events,we simulated sources,each of which had been modeled using an absorbed power law combined with Gaussians,in different FXT modes and different *** allowed us to determine the OoT spectral indices and pile-up ***:In the timing mode of FXT,the OoT events occupy a large proportion and the OoT correction must be done with the assumption that all photons originate from the source position on the *** for some bright sources,the OoT events may be sufficient to derivate the source spectra,especially when pile-up occurs,particularly in the full frame mode and the partial window mode of ***:We conclude that the OoT events can provide additional information about the celestial sources and can be used to estimate whether the pile-up occurs or not and the scope of ***,they can be also used to determine the new sources and improve the detection significance of a source.

关键词： Out-of-time Event PN-CCD pile-up

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Energy Parameter Correlation of Failure Life Data between Cyclic Ball Indentation and Low Cycle Fatigue

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Open Journal of Metal 2012年第1期2卷 31-36页

作者： Aneesh Bangia Raghu V. Prakash Department of Mechanical Engineering Indian Institute of Technology Madras Chennai India

Material properties provide important information about the fatigue life which makes life extension of critical components in various industries possible. The conventional methods of determining tensile strength and fatigue life through ASTM or equivalent standard specimen have their limitations due to size requirements of test specimen. Automated Ball Indentation (ABI) is a semi-invasive technique that is useful for determining the material properties. A tungsten carbide ball of diameter 1.57 mm is used to load the test specimen and the force vs. displacement response is used to estimate material properties. Methods have been formulated in the past to predict the fatigue life of the specimen by correlating Cyclic Indentation and Low Cycle fatigue data. In this work, investigation of the role of plastic dissipation energy in failure and its correlation for the two processes by Finite Element simulations in ABAQUS is attempted. Results such as force vs. displacement response, residual depth and plastic diameter with Haggag’s [1] formulation and experimental results are validated first. Then, the plastic dissipation energy density, which is a comparable parameter, is plotted for both Cyclic Indentation and Low Cycle Fatigue. A reasonably good correlation is obtained which also validates the failure life predicted from knee-point approach. Dependence of the pile-up profile of variables such as method of loading and the friction between the contacting bodies is also discussed.

关键词： Cyclic Indentation Fatigue Plastic Dissipation Energy Density pile-up

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Volume, Side-Area, and Force Direction of Berkovich and Cubecorner Indenters, Novel Important Insights

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Advances in Materials Physics and Chemistry 2021年第11期11卷 212-241页

作者： Gerd Kaupp University of Oldenburg Oldenburg Germany

The iteration-free physical description of pyramidal indentations with closed mathematical equations is comprehensively described and extended for creating new insights in this important field of research and applications. All calculations are easily repeatable and should be programmed by instrument builders for even easier general use. Formulas for the volumes and side-areas of Berkovich and cubecorner as a function of depth are deduced and provided, as are the resulting forces and force directions. All of these allow for the detailed comparison of the different indenters on the mathematical reality. The pyramidal values differ remarkably from the ones of so-called “equivalent cones”. The worldwide use of such pseudo-cones is in severe error. The earlier claimed and used 3 times higher displaced volume with cube corner than with Berkovich is disproved. Both displace the same amount at the same applied force. The unprecedented mathematical results are experimentally confirmed for the physical indentation hardness and for the sharp-onset phase-transi- tions with calculated transition energy. The comparison of both indenters provides novel basic insights. Isotropic materials exhibit the same phase transition onset force, but the transition energy is larger with the cube corner, due to higher force and flatter force direction. This qualifies the cube corner for fracture toughness studies. Pile-up is not from the claimed “friction with the indenter”. Anisotropic materials with cleavage planes and channels undergo sliding along these

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The Accuracy in Prediction of Elastic Modulus of Elasto-plastic Materials by Spherical Indentation

The Accuracy in Prediction of Elastic Modulus of Elasto-plas...

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2012年海峡两岸破坏科学/材料试验学术会议

作者： Qianhua Kan Guozheng Kang Wenyi Yan Han Jiang Yujie Liu School of Mechanics and Engineering Southwest Jiaotong University Department of Mechanical and Aerospace Engineering Monash University School of Mechanics and Engineering Southwest Jiaotong Universit

Micro- or nano-indentation tests are commonly applied to determine mechanical properties of elastic-plastic materials at small *** indenters have been popularly applied to numerically investigate indentation technique in order to avoid plastic *** accuracy of the prediction of the elastic modulus by using the popular Field-Swain and Oliver-Pharr method for spherical indentation was investigated *** show that both methods exhibit significant depth-sensitive error in predicted elastic modulus of elastic-plastic materials due to the non-geometrical similarity of spherical indenter and pile-up ***,the advantages of both Field-Swain and Oliver-Pharr methods were combined to improve the accuracy in prediction of elastic ***,the modified method was numerically and experimentally validated.

关键词： Spherical Indentation pile-up Sink-in Elastic Modulus Finite Element Analysis

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