Papers by Keyword: Nanoindentation

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Authors: Raffaella Aversa, Antonio Apicella
Abstract: Stiffness and elastic mechanical properties of the Zr44-Ti11-Cu10-Ni10-Be25 metal glass Alloy have been investigated by nanoindentation and Atomic Force Microscopy.Continuous stiffness measurements were carried out on the as received samples. Max indentation depth of 2000 Nm has been chosen. A 3D analysis of the indent traces has been performed using a Atomic Force Microscope: pile-up at the indentation edge was observed. These metallic glasses, therefore, although showing brittle like linear elastic behaviour up to failure are still capable of undergoing plastic shear flow at the nanoscale level that may potentially lead to high material ultimate properties. Elastic modulus of 116,2 ± 0,9 GPa has been found to be independent on indentation depth while a high hardness of 8,0 ± 0,8 GPa has been measured at low indentation depths (100 nm) that progressively reduces to a constant value of 7,0 ± 0,1 GPa at increasing depths (up to 2000 nm).
Authors: Yi Chuan Chen, C. Y. A. Tsao, Sy Cherng Yang, Chang Chuan Hsu
Abstract: Rapid solidification process was employed to make 6061 Al alloy powder. Powder size distribution was analyzed with SEM. Powder densities, i.e. apparent density and tap density, were measured. Thermal properties were measured via DSC. Surface condition and microstructures and their chemical compositions were characterized with XRD, OM, SEM/EDX. Nanoindentation was employed to obtain the hardness and Young’s modulus of the powders. The relationships among the atomization parameters, powder shapes and sizes, powder densities, thermal properties, microstructures and the mechanical properties were analyzed and rationalized.
Authors: Le Zhou, Anit Giri, Kyu Cho, Yong Ho Sohn
Abstract: The ferromagnetic shape memory and magnetocaloric properties of NiMnGa alloys are closely related to the martensitic transformation from high temperature austenitic phase to low temperature martensitic phase. The transformation temperature and the resulting microstructure and crystallography of the martensites can be very complex, but are crucial to the optimization of the material performance. A combinatorial study with a series of solid-to-solid diffusion couples and various characterization techniques, including scanning electron microscopy, focused ion beam, transmission electron microscopy, electron probe microanalysis, and nanoindentation, was carried out to investigate the microstructural and crystallographic development, and mechanical properties in NiMnGa alloys. Both austenitic and martensitic phases were found at room temperature in each diffusion couple with a clear interphase boundary. Crystallographic variations in martensitic phase, including non-modulated (NM) martensite and modulated (5M or 7M) martensite, were found in the diffusion couples. All martensitic microstructure consists of variants with different orientations and the twinning relationship. A decrease of reduced elastic modulus (Er) was observed with Ni substituting for Ga in the austenitic phase. However, an opposite trend of an increase in Er was found in the martensitic phase. The softening of the elastic constants near the vicinity of martensitic transformation contributed to a sharp decrease in Er near the interphase boundary. The measured Er had a larger scatter for the martensitic phase than that for the austenitic phase.
Authors: Seung Baek, Sung Kuen Cho, Chang Sung Seok
Abstract: In this study, we investigated indentation behavior by varying the tip radius in a finite element model. We measured the tip radius and shape of the nano-indenter by SPM (scanning probe microscope) and compared them with the simulation results. The tip radius of cube corner indenter was measured to be 39nm, in agreement with the common tip radius of such indenters, which range from 20~50nm.
Authors: Fei Wang, Ke Wei Xu
Abstract: The work of nanoindentation approach is developed and applied for measure of residual stress relaxation during indenter penetrates in thin films. The residual stress at given penetration depth is measured from the different integral area which under load-depth curve of different stress state. This method can measure residual stress relaxation without the need for estimating yield strength, strain hardening index and hardness.
Authors: Li Chang, Liang Chi Zhang
Abstract: It is known that silicon, during nanoindentation unloading, undergoes various phase transformations beneath the indenter. Investigations into the details are however not available. This paper studies the unloading behavior of silicon subjected to cyclic nanoindentations. The results show that the elastic unloading behavior of the material can be described by a power relationship, P = α∙hm, where P is the load, h is the elastic displacement, and α and m are material constants. It was found that the values of α and m were almost independent of the phase transition events, indicating that the elastic response of the material is mostly governed by the mechanical properties of Si-I phase while the influence of the phase transformations is negligible.
Authors: Aleš Materna, Petr Haušild
Abstract: The effect of the grain orientation of the stainless steel AISI 304 and the effect of the indenter orientation on the indentation moduli was numerically studied by means of the finite element method. The contact areas were evaluated numerically and the indentation moduli was determined according to the Oliver-Pharr method. As a result, the crystallographic orientations in which the indenter orientation plays the most important role were identified. However, the observed indentation moduli variation is within the scatter of the experimental data in practical applications.
Authors: Chih Ling Lin, Han Huang, Bronwen W. Cribb, Anthony Russell
Abstract: Human bone fracture associated with osteoporosis was hypothesized to be related to the alteration of mechanical properties in bones. In this work, cortical and trabecular bones from human femoral heads were studied. Bone samples of eight female and four male patients, with ages varying from 37 to 93 years, were collected from total hip replacement surgery. Reduced modulus (Er) and hardness (H) of osteons, interstitial lamellae and trabeculae were characterized by nanoindentation. The results showed both the reduced modulus and hardness of the interstitial lamellae were significant higher than those of osteons and trabeculae. Though there was no significant difference in microstructures in the Group A (age < 60 years) and B (age > 60 years), the Group B bones demonstrated to be stiffer.
Authors: K. Short, Richard Wuhrer, G. Collins, Wing Yiu Yeung
Authors: Ki Ho Cho, Hak Joo Lee, Jae Hyun Kim, Jong Man Kim, Yong Kweon Kim, Chang Wook Baek
Abstract: We have designed and fabricated diamond-shaped AFM cantilevers capable of performing multi-functioning tasks by using single crystal silicon (SCS) micromachining techniques. Structural improvement of the cantilever has clearly solved the crucial problems resulted from using conventional simple beam-AFM cantilever for mechanical testing. After forcecalibration of the cantilever, indentation tests are performed to determine the mechanical behaviors in micro/nano-scale as well as topographic imaging. A diamond Berkovich tip of which radius at the apex is approximately 20 nm is attached on the cantilever for the indentation test and 3D topography measurement. The indentation load-depth curves of nano-scale polymeric pattern (PAK01-UV curable blended resin) are measured and surface topography right after indenting is also obtained. Development of this novel cantilever will extend the AFM functionality into the highly sensitive mechanical testing devices in nano/pico scale.
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