scholarly journals Evaluation of Brie cheese maturity from indentation test

2010 ◽  
Vol 58 (5) ◽  
pp. 281-288
Author(s):  
Šárka Nedomová
Keyword(s):  
Rheological Properties ◽  
Viscoelastic Properties ◽  
Indentation Test ◽  
Constant Speed ◽  
Stress Strain ◽  
Displacement Response ◽  
Indentation Force ◽  
Force Displacement

Rheological properties of Brie cheese with different time of ripening (1, 3, 4, 5, 6, 7 and 8 weeks) were evaluated. This evaluation has been performed using the indentation test at the constant speed of the indentor penetration (20 mm/min). Two types of the indentors (bar and ball) have been used. The hardness of the cheese increased during the first three weeks of the ripening and than it decreased. The properties evaluated from the indentation test approved the isotropic behaviour of the tested cheese. The viscoelastic properties of the tested cheese have been obtained. The se pro­per­ties were achieved using a methodology enabling to convert the indentation force–displacement response into the stress–strain relations. The obtained viscoelastic properties are independent on the used type of the indentor.

scholarly journals An Investigation of Nanomechanical Properties of Materials using Nanoindentation and Artificial Neural Network

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Hyuk Lee ◽  
Wai Yeong Huen ◽  
Vanissorn Vimonsatit ◽  
Priyan Mendis
Keyword(s):  
Work Hardening ◽  
Stress Strain ◽  
Indentation Force ◽  
Wide Range ◽  
Indentation Tests ◽  
Strain Relationship ◽  
Properties Of Materials ◽  
Artificial Neural ◽  
Hardening Power ◽  
Force Displacement

Abstract Mechanical properties of materials can be derived from the force-displacement relationship through instrumented indentation tests. Complications arise when establishing the full elastic-plastic stress-strain relationship as the accuracy depends on how the material’s and indenter’s parameters are incorporated. For instance, the effect of the material work-hardening phenomenon such as the pile-up and sink-in effect cannot be accounted for with simplified analytical indentation solutions. Due to this limitation, this paper proposes a new inverse analysis approach based on dimensional functions analysis and artificial neural networks (ANNs). A database of the dimensional functions relating stress and strain parameters of materials has been developed. The database covers a wide range of engineering materials that have the yield strength-to-modulus ratio (σy/E) between 0.001 to 0.5, the work-hardening power (n) between 0–0.5, Poisson’s ratio (v) between 0.15–0.45, and the indentation angle (θ) between 65–80 degrees. The proposed algorithm enables determining the nanomechanical stress-strain parameters using the indentation force-displacement relationship, and is applicable to any materials that the properties are within the database range. The obtained results are validated with the conventional test results of steel and aluminum samples. To further demonstrate the application of the proposed algorithm, the nanomechanical stress-strain parameters of ordinary Portland cement phases were determined.

scholarly journals The Influence of the Addition of Nuts on the Thermal and Rheological Properties of Wheat Flour

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3969
Author(s):  
Karolina Pycia ◽  
Lesław Juszczak
Keyword(s):  
Rheological Properties ◽  
Wheat Flour ◽  
Viscoelastic Properties ◽  
Control Sample ◽  
Scanning Calorimetry ◽  
Creep And Recovery ◽  
Research Material ◽  
Pasting Characteristics ◽  
Tan Δ ◽  
Weak Gels

The aim of the study was to assess the influence of replacing wheat flour with hazelnuts or walnuts, in various amounts, on the thermal and rheological properties of the obtained systems. The research material were systems in which wheat flour was replaced with ground hazelnuts (H) or walnuts (W) in the amount of 5%, 10%, and 15%. The parameters of the thermodynamic gelatinization characteristics were determined by the differential scanning calorimetry method. In addition, the pasting characteristics were determined with the use of a viscosity analyzer and the viscoelastic properties were assessed. Sweep frequency and creep and recovery tests were used to assess the viscoelastic properties of the tested gels. It was found that replacing wheat flour with nuts increased the values of gelatinization temperature, gelatinization, and retrogradation enthalpy, and the degree of retrogradation. The highest viscosity was characteristic of the control sample (2039 mPa·s), and the lowest for the paste with 15% addition of walnuts (1120 mPa·s). Replacing the flour with nuts resulted in a very visible reduction in the viscosity of such systems. In addition, gels based on the systems with the addition of H and W were weak gels (tan δ = G″/G′ > 0.1), and the values of G′ and G″ parameters decreased with the increased share of nuts in the systems. Creep and recovery analysis indicated that the systems in which wheat flour was replaced with hazelnuts were less susceptible to deformation compared to the systems with the addition of W.

Semi-inverse method for predicting stress–strain relationship from cone indentations

2003 ◽  
Vol 18 (9) ◽  
pp. 2068-2078 ◽  
Author(s):  
A. DiCarlo ◽  
H. T. Y. Yang ◽  
S. Chandrasekar
Keyword(s):  
A Priori ◽  
Model Material ◽  
Material Behavior ◽  
The Finite Element Method ◽  
Stress Strain ◽  
Indentation Tests ◽  
Strain Relationship ◽  
Initial Force ◽  
Relationship Of ◽  
Force Displacement

A method for determining the stress–strain relationship of a material from hardness values H obtained from cone indentation tests with various apical angles is presented. The materials studied were assumed to exhibit power-law hardening. As a result, the properties of importance are the Young's modulus E, yield strength Y, and the work-hardening exponent n. Previous work [W.C. Oliver and G.M. Pharr, J. Mater. Res. 7, 1564 (1992)] showed that E can be determined from initial force–displacement data collected while unloading the indenter from the material. Consequently, the properties that need to be determined are Y and n. Dimensional analysis was used to generalize H/E so that it was a function of Y/E and n [Y-T. Cheng and C-M. Cheng, J. Appl. Phys. 84, 1284 (1999); Philos. Mag. Lett. 77, 39 (1998)]. A parametric study of Y/E and n was conducted using the finite element method to model material behavior. Regression analysis was used to correlate the H/E findings from the simulations to Y/E and n. With the a priori knowledge of E, this correlation was used to estimate Y and n.

Seismic assessment of reinforced concrete columns with short lap splices

2021 ◽  
pp. 875529302199483
Author(s):  
Eyitayo A Opabola ◽  
Kenneth J Elwood
Keyword(s):  
Reinforced Concrete ◽  
Failure Mode ◽  
Failure Modes ◽  
Concrete Columns ◽  
Seismic Assessment ◽  
Rc Columns ◽  
Lap Splices ◽  
Displacement Response ◽  
Force Displacement ◽  
Probable Failure

Existing reinforced concrete (RC) columns with short splices in older-type frame structures are prone to either a shear or bond mechanism. Experimental results have shown that the force–displacement response of columns exhibiting these failure modes are different from flexure-critical columns and typically have lower deformation capacity. This article presents a failure mode-based approach for seismic assessment of RC columns with short splices. In this approach, first, the probable failure mode of the component is evaluated. Subsequently, based on the failure mode, the force–displacement response of the component can be predicted. In this article, recommendations are proposed for evaluating the probable failure mode, elastic rotation, drift at lateral failure, and drift at axial failure for columns with short splices experiencing shear, flexure, or bond failures.

Can indentation technique measure unique elastoplastic properties?

2009 ◽  
Vol 24 (3) ◽  
pp. 784-800 ◽  
Author(s):  
Ling Liu ◽  
Nagahisa Ogasawara ◽  
Norimasa Chiba ◽  
Xi Chen
Keyword(s):  
Critical Strain ◽  
Indentation Test ◽  
Strain Curve ◽  
Spherical Indentation ◽  
Plastic Behavior ◽  
Displacement Curve ◽  
Application Range ◽  
Indentation Technique ◽  
Elastoplastic Properties ◽  
Force Displacement

Indentation is widely used to extract material elastoplastic properties from measured force-displacement curves. Many previous studies argued or implied that such a measurement is unique and the whole material stress-strain curve can be measured. Here we show that first, for a given indenter geometry, the indentation test cannot effectively probe material plastic behavior beyond a critical strain, and thus the solution of the reverse analysis of the indentation force-displacement curve is nonunique beyond such a critical strain. Secondly, even within the critical strain, pairs of mystical materials can exist that have essentially identical indentation responses (with differences below the resolution of published indentation techniques) even when the indenter angle is varied over a large range. Thus, fundamental elastoplastic behaviors, such as the yield stress and work hardening properties (functions), cannot be uniquely determined from the force-displacement curves of indentation analyses (including both plural sharp indentation and deep spherical indentation). Explicit algorithms of deriving the mystical materials are established, and we qualitatively correlate the sharp and spherical indentation analyses through the use of critical strain. The theoretical study in this paper addresses important questions of the application range, limitations, and uniqueness of the indentation test, as well as providing useful guidelines to properly use the indentation technique to measure material constitutive properties.

scholarly journals Comparison of waveform-derived corneal stiffness and stress-strain extensometry-derived corneal stiffness using different cross-linking irradiances: an experimental study with air-puff applanation of ex vivo porcine eyes

2020 ◽  
Vol 258 (10) ◽  
pp. 2173-2184 ◽  
Author(s):  
Robert Herber ◽  
Mathew Francis ◽  
Eberhard Spoerl ◽  
Lutz E. Pillunat ◽  
Frederik Raiskup ◽  
...  
Keyword(s):  
Experimental Study ◽  
Ex Vivo ◽  
Cross Linking ◽  
Displacement Curve ◽  
Stress Strain ◽  
Strain Measurements ◽  
Deflection Amplitude ◽  
Force Displacement ◽  
Stiffening Effect ◽  
Porcine Eyes

Abstract Purpose To assess corneal stiffening of standard (S-CXL) and accelerated (A-CXL) cross-linking protocols by dynamic corneal response parameters and corneal bending stiffness (Kc[mean/linear]) derived from Corvis (CVS) Scheimpflug-based tonometry. These investigations were validated by corneal tensile stiffness (K[ts]), derived from stress-strain extensometry in ex vivo porcine eyes. Methods Seventy-two fresh-enucleated and de-epithelized porcine eyes were soaked in 0.1% riboflavin solution including 10% dextran for 10 min. The eyes were separated into four groups: controls (n = 18), S-CXL (intensity in mW/cm2*time in min; 3*30) (n = 18), A-CXL (9*10) (n = 18), and A-CXL (18*5) (n = 18), respectively. CXL was performed using CCL Vario. CVS measurements were performed on all eyes. Subsequently, corneal strips were extracted by a double-bladed scalpel and used for stress-strain measurements. K[ts] was calculated from a force-displacement curve. Mean corneal stiffness (Kc[mean]) and constant corneal stiffness (Kc[linear]) were calculated from raw CVS data. Results In CVS, biomechanical effects of cross-linking were shown to have a significantly decreased deflection amplitude as well as integrated radius, an increased IOP, and SP A1 (P < 0.05). Kc[mean]/Kc[linear] were significantly increased after CXL (P < 0.05). In the range from 2 to 6% strain, K[ts] was significantly higher in S-CXL (3*30) compared to A-CXL (9*10), A-CXL (18*5), and controls (P < 0.05). At 8% to 10% strain, all protocols induced a higher stiffness than controls (P < 0.05). Conclusion Several CVS parameters and Kc[mean] as well as Kc[linear] verify corneal stiffening effect after CXL on porcine eyes. S-CXL seems to have a higher tendency of stiffening than A-CXL protocols have, which was demonstrated by Scheimpflug-based tonometry and stress-strain extensometry.

Viscoelastic Properties of PVB Interlayer for Laminated Glass Structures Used in Building Reconstructions

2019 ◽  
Vol 808 ◽  
pp. 115-122
Author(s):  
Miroslav Vokáč ◽  
Tomáš Hána ◽  
Klára V. Machalická ◽  
Martina Eliášová
Keyword(s):  
Viscoelastic Properties ◽  
Thermoplastic Polyurethane ◽  
Maxwell Model ◽  
Polyvinyl Butyral ◽  
Laminated Glass ◽  
Building Structures ◽  
Structural Element ◽  
Stress Strain ◽  
Existing Building ◽  
Material Parameters

Laminated glass is a structural element used extensively in a reconstruction of existing building structures because of its transparency and simplicity. When using laminated glass as a glass staircase, balustrades, transparent flooring, facades or other structural elements, it is advisable to consider the shear interaction of individual glass panes in the cross-section. A conservative approach where the glass panes shear interaction is not considered, is uneconomical. This interaction depends on the properties of polymeric interlayers used in lamination process. Various commercial products based on PVB (polyvinyl butyral), EVA (ethylene vinyl acetate), ionomer, or thermoplastic polyurethane (TPU) are used. Stiffness of polymers depends on temperature and duration of a load. Interlayers exhibit the viscoelastic properties and temperature dependency usually described by the generalized Maxwell model and WLF model (Williams-Landel-Ferry). Parameters of these models are the most effectively determined by Dynamic Mechanical Thermal Analysis (DMTA), where the material is cyclically loaded at different frequencies and temperatures. Material parameters were found by DMTA in shear for PVB type of interlayer Trosifol® BG R20. In addition, the experimental quasi-static loading tests in shear were performed at different loading rates and at various temperatures. These experimental stress-strain diagrams were compared to the theoretical stress-strain relations obtained from Maxwell model with material parameters based on DMTA testing. All tests were performed in Klokner Institute CTU in Prague.

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