scholarly journals Erratum: “Indentation responses of time-dependent films on stiff substrates” [J. Mater. Res. 19, 2487 (2004)]

2004 ◽  
Vol 19 (10) ◽  
pp. 3120-3121
Keyword(s):  
Power Law ◽  
Peak Load ◽  
Indentation Load ◽  
Small Peak ◽  
Peak Loads ◽  
Materials Research ◽  
Indentation Tests ◽  
Unloading Rate ◽  
Loading And Unloading ◽  
Load Displacement

This article appeared in the August 2004 issue of Journal of Materials Research. The following corrections are required.Section II. Experiments p. 2488The third paragraph in the Experiments section should appear as follows:One mechanism to explore changes in the shape of an indentation load-displacement response is to normalize the trace by its peak point. It has been demonstrated that the normalized [h/h(PMAX), P/PMAX] experimental responses for bulk polymers indented at constant loading- and unloading rate with the same rise time (but at different peak load levels) are identical. Figure 1(a) shows raw load-displacement data for indentation tests performed at small peak loads in the thickest polymer film (Epon) in the current study. The peak loads, 1 and 2 mN, were chosen to correspond to depths less than 10% of the film thickness in both cases. The responses normalize to the same shape [Fig. 1(b)]. When the 1-mN normalized response is compared with those from much greater load levels (50 and 500 mN), there are clear changes in the shape of the response, both loading and unloading [Fig. 1(c)]. In particular, the loading response shifts from slightly less than quadratic (power law fit with exponent 1.8) for the 1-mN response, as would be expected for a quadratic material with some creep effect; to a response between quadratic and cubic (power law fit with exponent 2.6) for the 500-mN response. The unloading response is also altered in shape, with a steeper unloading tangent at the larger load.

Indentation responses of time-dependent films on stiff substrates

2004 ◽  
Vol 19 (8) ◽  
pp. 2487-2497 ◽  
Author(s):  
Michelle L. Oyen ◽  
Robert F. Cook ◽  
John A. Emerson ◽  
Neville R. Moody
Keyword(s):  
Peak Load ◽  
Elastic Response ◽  
Depth Sensing ◽  
Indentation Tests ◽  
Unloading Rate ◽  
Loading And Unloading ◽  
Load Displacement ◽  
Film Substrate ◽  
Single Set ◽  
Substrate Influence

A viscous-elastic-plastic indentation model was extended to a thin-film system, including the effect of stiffening due to a substrate of greater modulus. The system model includes a total of five material parameters: three for the film response (modulus, hardness, and time constant), one for the substrate response (modulus), and one representing the length-scale associated with the film-substrate interface. The substrate influence is incorporated into the elastic response of the film through a depth-weighted elastic modulus (based on a series sum of film and substrate contributions). Constant loading- and unloading-rate depth-sensing indentation tests were performed on polymer films on glass or metal substrates. Evidence of substrate influence was examined by normalization of the load-displacement traces. Comparisons were made between the model and experiments for indentation tests at different peak load levels and with varying degrees of substrate influence. A single set of five parameters was sufficient to characterize and predict the experimental load-displacement data over a large range of peak load levels and corresponding degrees of substrate influence.

scholarly journals Application of Nanoindentation in the Characterization of a Porous Material with a Clastic Texture

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4579
Author(s):  
Sathwik S. Kasyap ◽  
Kostas Senetakis
Keyword(s):  
Materials Science ◽  
Complex Structure ◽  
Elastic Stiffness ◽  
Indentation Load ◽  
Nanoindentation Test ◽  
Displacement Curve ◽  
Indentation Tests ◽  
Materials Science And Engineering ◽  
Loading And Unloading ◽  
Load Displacement

In materials science and engineering, a significant amount of research has been carried out using indentation techniques in order to characterize the mechanical properties and microstructure of a broad range of natural and engineered materials. However, there are many unresearched or partly researched areas, such as, for example, the investigation of the shape of the indentation load–displacement curve, the associated mechanism in porous materials with clastic texture, and the influence of the texture on the constitutive behavior of the materials. In the present study, nanoindentation is employed in the analysis of the mechanical behavior of a benchmark material composed of plaster of Paris, which represents a brand of highly porous-clastic materials with a complex structure; such materials may find many applications in medicine, production industry, and energy sectors. The focus of the study is directed at the examination of the influence of the porous structure on the load–displacement response in loading and unloading phases based on nanoindentation experiments, as well as the variation with repeating the indentation in already indented locations. Events such as pop-in in the loading phase and bowing out and elbowing in the unloading phase of a given nanoindentation test are studied. Modulus, hardness, and the elastic stiffness values were additionally examined. The repeated indentation tests provided validations of various mechanisms in the loading and unloading phases of the indentation tests. The results from this study provide some fundamental insights into the interpretation of the nanoindentation behavior and the viscoelastic nature of porous-clastic materials. Some insights on the influence of indentation spacing to depth ratio were also obtained, providing scope for further studies.

Study on behaviour of geometrically scaled glass reinforced epoxy tubes subjected to non-coincident quasi static-indentation

2018 ◽  
Vol 9 (5) ◽  
pp. 675-692
Author(s):  
Fahad Almaskari ◽  
Farrukh Hafeez
Keyword(s):  
Peak Load ◽  
Repeated Loading ◽  
Damage Growth ◽  
Content Type ◽  
Starting Point ◽  
Static Indentation ◽  
Indentation Tests ◽  
Loading And Unloading ◽  
Force Displacement ◽  
Practical Implications

Purpose The purpose of this paper is to study the behaviour of glass reinforced epoxy tubes subjected to repeated indentation loads at two non-coincident indentations 180° apart. Design/methodology/approach Four geometrically scaled specimens ranging from 100 to 400 mm diameter were used in repeated indentation tests. Force, displacement and damage growth were recorded for loading and unloading until the indenter returned to its original starting point. Findings Similar scaled trends were observed between the non-coincidental loadings. Unlike reported response form coincidental loadings, the responses from non-coincidental loadings yield lower values for bending stiffness and peak load. Research limitations/implications The differences in behaviour of the specimen between non-coincident loadings were attributed to reductions in fracture toughness and circumferential modulus. Practical implications Distant non-interacting damage and delamination around the circumference does reduce the structural performance. Originality/value Behaviour of composite tubes under different loading conditions, for example low speed impact or quasi static indentation, is widely studied, however little attention has been given to the repeated loading incidents.

Numerical Derivative Analysis of Load-Displacement Curves in Depth-Sensing Indentation

2003 ◽  
Vol 791 ◽  
Author(s):  
Tom Juliano ◽  
Vladislav Domnich ◽  
Tom Buchheit ◽  
Yury Gogotsi
Keyword(s):  
Thin Film ◽  
Single Crystal Silicon ◽  
Indentation Load ◽  
Fused Silica ◽  
Depth Sensing ◽  
Crystal Silicon ◽  
Derivative Analysis ◽  
Loading And Unloading ◽  
Load Displacement ◽  
Carbide Derived Carbon

ABSTRACTThe use of load-displacement derivative behavior and power-law curve fitting is applied to find the location of events for a number of different materials during depth-sensing indentation. Load-displacement curves for Berkovich indentations on fused silica, fullerene thin film on sapphire, CdTe thin film on silicon, single crystal silicon, carbide derived carbon, and a polymethylmethacrylate/hydroxyapatite (PMMA/HA) particle composite are examined. The analysis is applied to quantify the location of different events that occur during material loading and unloading.

An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments

1992 ◽  
Vol 7 (6) ◽  
pp. 1564-1583 ◽  
Author(s):  
W.C. Oliver ◽  
G.M. Pharr
Keyword(s):  
Elastic Modulus ◽  
Peak Load ◽  
Soda Lime ◽  
Indentation Load ◽  
Fused Silica ◽  
Soda Lime Glass ◽  
Flat Punch ◽  
Analysis Technique ◽  
Load Displacement ◽  
Improved Technique

The indentation load-displacement behavior of six materials tested with a Berkovich indenter has been carefully documented to establish an improved method for determining hardness and elastic modulus from indentation load-displacement data. The materials included fused silica, soda–lime glass, and single crystals of aluminum, tungsten, quartz, and sapphire. It is shown that the load–displacement curves during unloading in these materials are not linear, even in the initial stages, thereby suggesting that the flat punch approximation used so often in the analysis of unloading data is not entirely adequate. An analysis technique is presented that accounts for the curvature in the unloading data and provides a physically justifiable procedure for determining the depth which should be used in conjunction with the indenter shape function to establish the contact area at peak load. The hardnesses and elastic moduli of the six materials are computed using the analysis procedure and compared with values determined by independent means to assess the accuracy of the method. The results show that with good technique, moduli can be measured to within 5%.

Techniques for Determining Mechanical Properties of Power-Law Materials by Instrumented Indentation Tests

2007 ◽  
Vol 340-341 ◽  
pp. 555-562 ◽  
Author(s):  
J. Lin ◽  
J. Luo ◽  
Trevor A. Dean
Keyword(s):  
Mechanical Properties ◽  
Power Law ◽  
Plastic Material ◽  
Optimization Approach ◽  
Mechanical Properties Of Materials ◽  
Indentation Tests ◽  
Loading And Unloading ◽  
Properties Of Materials ◽  
Elastic Plastic Material

A novel optimization approach is proposed to extract mechanical properties of a power law material from its given experimental nano-indentation P-h curves. A set of equations have been established to relate the P-h curve to mechanical properties, E, σ y and n, of a material. Using the proposed optimization approach, convergence studies were carried out for the determination of the mechanical properties of materials. It was found that the mechanical properties of an elastic-plastic material usually cannot be uniquely determined using a single loading and unloading P-h curve. Thus a technique has also been developed to determine the material properties from indentation p-h curves using indenters with two different angles. This enables the mechanical properties of materials to be uniquely determined.

Uniqueness of reverse analysis from conical indentation tests

2004 ◽  
Vol 19 (8) ◽  
pp. 2498-2502 ◽  
Author(s):  
K.K. Tho ◽  
S. Swaddiwudhipong ◽  
Z.S. Liu ◽  
K. Zeng ◽  
J. Hua
Keyword(s):  
Material Properties ◽  
Plastic Material ◽  
Large Strain ◽  
Indentation Load ◽  
Initial Slope ◽  
Displacement Curve ◽  
Maximum Indentation Depth ◽  
Indentation Tests ◽  
Reverse Analysis ◽  
Load Displacement

The curvature of the loading curve, the initial slope of the unloading curve, and the ratio of the residual depth to maximum indentation depth are three main quantitiesthat can be established from an indentation load-displacement curve. A relationship among these three quantities was analytically derived. This relationship is valid for elasto-plastic material with power law strain hardening and indented by conical indenters of any geometry. The validity of this relationship is numerically verified through large strain, large deformation finite element analyses. The existence of an intrinsic relationship among the three quantities implies that only two independent quantities can be obtained from the load-displacement curve of a single conical indenter. The reverse analysis of a single load-displacement curve will yield non-unique combinations of elasto-plastic material properties due to the availability of only two independent quantities to solve for the three unknown material properties.

Prediction, Testing, and Analysis of a 50 m Long Pile in Soft Marine Clay

2019 ◽  
Vol 13 (2) ◽  
Author(s):  
Bengt Fellenius
Keyword(s):  
Peak Load ◽  
Pile Head ◽  
Marine Clay ◽  
Loading Test ◽  
Head Displacement ◽  
Floating Pile ◽  
Peak Loads ◽  
Static Loading Test ◽  
Beta Coefficient ◽  
Load Movement

On April 4, 2018, 209 days after driving, a static loading test was performed on a 50 m long, strain-gage instrumented, square 275-mm diameter, precast, shaft-bearing (“floating”) pile in Göteborg, Sweden. The soil profile consisted of a 90 m thick, soft, postglacial, marine clay. The groundwater table was at about 1.0 m depth. The undrained shear strength was about 20 kPa at 10 m depth and increased linearly to about 80 kPa at 55m depth. The load-distribution at the peak load correlated to an average effective stress beta-coefficient of 0.19 along the pile or, alternatively, a unit shaft shear resistance of 15 kPa at 10 m depth increasing to about 65 kPa at 50 m depth, indicating an α-coefficient of about 0.80. Prior to the test, geotechnical engineers around the world were invited to predict the load-movement curve to be established in the test—22 predictions from 10 countries were received. The predictions of pile stiffness, and pile head displacement showed considerable scatter, however. Predicted peak loads ranged from 65% to 200% of the actual 1,800-kN peak-load, and 35% to 300% of the load at 22-mm movement.

Identification of Hardening Parameters of Metals From Spherical Indentation Tests

2001 ◽  
Vol 123 (3) ◽  
pp. 245-250 ◽  
Author(s):  
S. Kucharski ◽  
Z. Mro´z
Keyword(s):  
Indentation Test ◽  
Strain Curve ◽  
Load Level ◽  
Spherical Indentation ◽  
Indentation Tests ◽  
Geometric Sequence ◽  
Loading And Unloading ◽  
Plastic Hardening ◽  
Hardening Curve ◽  
Two Parameters

The identification method of hardening parameters specifying stress-strain curve is proposed by applying spherical indentation test and measuring the penetration depth during loading and unloading. The loading program is composed of a geometric sequence of loading and partial unloading steps from which the variation of permanent penetration with load level is determined. This data is used for specification of two parameters k and m occurring in the plastic hardening curve εp=σ/k1/m, where εp denotes the plastic strain.

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