Papers by Keyword: Spherical Indenter

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Authors: P.M. Ogar, V.A. Tarasov
Abstract: We Consider a Layered Elastic Body, Consisting of Base Material with Young's Modulus E0 and Poisson's Ratio ν0 and Coating Thickness δ, Respectively, with E1 и ν1. the Thickness of the Base Is much Greater than the Thickness of the Coating. A Stiffness Model of the Layered Body with Loading His Axisymmetric Load, which Allows to Determine its Elastic Characteristics Is Proposed. the Quantitative Effect of the Relative Thickness of the Coating, the Ratio of the Elastic Properties of the Materials and Forms of the Applied Load Is Shown. an Expression for Determining the Elastic Modulus of the Coating when the Effective Modulus of Elasticity of the Layered Body Indentation Determined by the Method of Oliver-Farr Is Got. the Thickness of a Covering and Elastic Constants of the Main Material and Intentor Are Thus Considered.
Authors: Jaroslav Čech, Petr Haušild, Ondřej Kovářík, Marek Škereň
Abstract: Actual shape of the diamond spherical indenter of nominal radius 20 μm was investigated in this study. 3D reconstruction was performed by atomic force microscope and by the method of stereopair using SEM images of the tip taken under several different angles. The results were compared with the shape obtained indirectly by the calibration performed on specimens with known Young’s modulus. It was found that lower effective values of tip radius for the small penetration depths are caused by the irregular geometry of contact between indenter and specimen surface. With increasing penetration depth the radius increased to the theoretical values and it decreased again for high penetration depths. The stress-strain curves were determined using corrected effective indenter radius.
Authors: Ju Young Kim, Jung Jun Lee, Yun Hee Lee, Jae Il Jang, Dong Il Kwon
Abstract: Surface roughness is main source of error in instrumented microindentation when it is not negligible relative to the indentation depth. The effect of a rough surface on the results of instrumented microindentation testing using spherical indenter was analyzed by applying the contact depth model, which takes surface roughness into account. Improved variations in hardness and Young’s modulus were shown for W and Ni when the results were analyzed by this rough-surface model, while these values were underestimated with increasing surface roughness when analyzed by the flat-surface model. The deformation state of asperities underneath spherical indenter was also discussed.
Authors: Takahiro Takechi, Junichi Tamaki, Akihiko Kubo, A.M.M. Sharif Ullah
Abstract: Single-point fly cutting and nanoindentation test of quartz glass were performed using three different cutting tools, namely, a V-shaped cutting tool, a Vickers indenter and a spherical indenter, to investigate the elastic and plastic behaviors of quartz glass in ductile-regime machining. It was found that these behaviors depend on tool shape and that the V-shaped cutting tool is most effective for removing quartz glass material followed by the Vickers indenter and spherical indenter.
Authors: Peter Ogar, Denis Gorokhov, Ilya Phedorov
Abstract: Energy hardness is defined as energy density of material plastic displacement from the initial surface level. It is convenient to determine it from the kinetic indentation diagram constructed in the coordinates , where is a relative load, is a relative penetration of a spherical indenter. It dhould be note that a relative energy density is equal to multiplied by the parameter where varies within a narrow range for constructional materials used in machine building. A mean relative error in finding energy hardness by this approach does not exceed 5%. It is shown that for the majority of mechanical engineering materials energy hardness is intermediate between plastic hardness and Meyer’s hardness.
Authors: P.M. Ogar, V.A. Tarasov, D.B. Gorokhov
Abstract: Energy hardness is defined as energy density of material’s plastic displacement from the initial surface level. It is convenient to determine it from the kinetic indentation diagram constructed in coordinates P - h, where P is the relative load, h is the relative penetration of a spherical indenter. With that the relative energy density is equal P/h multiplied by the parameter Cp(h) , where varies within a range narrow for the constructional materials. The relative error of the energy hardness determination by this approach does not exceed 5%.
Authors: P.M. Ogar, V.A. Tarasov
Abstract: Kinetic indentation diagram has been used for the mathematical description of the contact interaction between a sphere and elastoplastic half-space. The unloading curve exponent m has been determined. It has been shown that the value of m is independent of the load distribution on the contact surface, and does depend on the ratio c2h/R (or hc/R). Based on the deformation characteristics similitude, the sphere penetration value h has been determined for the areas of constrained and developed elastoplasticity. The new parameter khy,n) has been introduced to account for the material hardening.
Authors: Michael V. Swain
Authors: M. Saadatfar, A. Soleimani
Abstract: The study of polymer/clay nanocomposites has attracted major research and commercial interests due to their superior mechanical and thermal properties to those of the neat polymers. The present work is to modelling the spherical nanoindentation of exfoliated polymer /clay nanocomposite that has nonlinear elastic behavior using numerical simulation. A two dimensional simulation is done and the effect of friction coefficient and indenter radius on load-displacement curve is investigated. It is observed that the simulation results of nanoindentation do not depend on the friction coefficient of indenter and specimen significantly.
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