Showing papers on "Indentation published in 1991"
TL;DR: A physically-based theoretical model for describing the phenomenon of indentation creep over the whole temperature range, from 300 K to melting, was developed in this paper, in agreement with experimental data.
Abstract: A physically-based theoretical model is developed for describing the phenomenon of indentation creep over the whole temperature range, from 300 K to melting. In agreement with experimental data col ...
211 citations
TL;DR: In this paper, electron micrographs of indents in (111) silicon reveal that a thin layer of material immediately adjacent to the indenter is plastically extruded, which indicates that the material can be deformed in this way.
Abstract: Scanning electron micrographs of indents in (111) silicon reveal that a thin layer of material immediately adjacent to the indenter is plastically extruded. The fact that the material can be deformed in this way indicates that it has metallic-like mechanical properties. This is presented as new evidence that a pressure-induced phase transformation to the metallic state occurs during the indentation of silicon.
208 citations
IBM1
TL;DR: The microindenter has proven to be a powerful device in the characterization of the mechanical properties of thin films as discussed by the authors, which allows for other mechanical properties, in addition to hardness, to be acquired.
Abstract: The microindenter has proven to be a powerful device in the characterization of the mechanical properties of thin films. The machine has both high resolution in the applied load and penetration depth measurements, as well as the versatility to perform different types of testing. The former provides the capability to deal with extremely thin films, while the latter allows for other mechanical properties, in addition to hardness, to be acquired. Four types of tests, namely indentation, scratch, load relaxation, and indentation fatigue tests can currently be conducted using the microindenter via different operating procedures. Only the scratch and load relaxation techniques will be covered in this paper. In a microscratch test, the normal load, tangential load, scratch length, and acoustic emission are monitored simultaneously during an entire scratch process for the purposes of measuring the critical load and studying the failure mechanisms of the deposited films. The adhesion strength, scratch hardness, fracture toughness, and friction are the mechanical properties which are possible to obtain by using this technique. Results from aluminum, carbon, and zirconia coatings will be discussed. The load relaxation test provides information on the creep properties of the films and results in an empirical constitutive relation between the applied stress and plastic strain rate. The creep properties of DC sputtered Al films will be used as an illustration of this.
197 citations
TL;DR: In this article, tension-tension cyclic loading tests have been conducted on a coarse-grained alumina ceramic that exhibits toughness-curve behavior by grain-interlock bridging and fatigue effects are observed in the regions of both short cracks and long cracks.
Abstract: Tension-tension cyclic loading tests have been conducted on a coarse-grained alumina ceramic that exhibits toughness-curve behavior by grain-interlock bridging Fatigue effects are observed in the regions of both short cracks, using indentation flaws, and long cracks, using compact-tension specimens A true mechanical fatigue effect is demonstrated by running the tests below the static fatigue limit A custom-made device for in situ observation of crack propagation in the scanning electron microscope enables us to identify bridge degradation as a cause of the fatigue process
182 citations
TL;DR: In this paper, the impact behavior of several laminate systems has been studied, defined by impact force, damage size and energy absorption, and it was found that the damage growth process during impact as the force surged to its maximum value can be visualized from the static indentation damage induced at incrementally increased force levels.
Abstract: The low velocity impact behavior of several laminate systems has been studied. Instrumented impact tests were compared with static indentation tests using the same specimen and test configurations. The impact behavior, defined by impact force, damage size and energy absorption, was found to be similar to the static indentation response. The damage growth process during impact as the force surged to its maximum value can be visualized from the static indentation damage induced at incrementally increased force levels. Delamination impact damage suddenly appeared only when the impact force reached a threshold value which was dependent on laminate fracture toughness. Further force increase resulted in gradual damage size growth until fiber damage caused the force to level off. There was evidence that laminate fracture toughness also affected the level-off force. Fiber damage not only absorbed significant energy but also allowed for further delamination damage growth. Overall, the characteristics of impact for...
137 citations
TL;DR: In this article, Young's modulus and hardness of TiN films are reported, which fall to within 3% of stoichiometry and have a 〈111〉 texture.
Abstract: Young’s modulus and hardness of TiN films are reported. The films, deposited on 440C stainless steel, range between 0.25 and 1.0 μm in thickness. They fall to within 3% of stoichiometry and have a 〈111〉 texture. Within experimental resolution, the properties of films with different thickness are indistinguishable: calculated values of Young’s modulus and hardness are 550±50 GPa and 31±4 GPa, respectively. Properties are obtained from a continuous indentation technique. A new correlation is used for identifying whether all films have the same properties, independent of thickness, and for measuring hardness of thin films. The same correlation is utilized for measuring machine compliance and obtaining the profile of the indenter tip. An elasticity analysis aids in obtaining elastic modulus from compliance data.
132 citations
110 citations
TL;DR: In this article, the authors used both continuous indentation and x-ray diffraction techniques to characterize stress relaxation in aluminum films of several thicknesses and found that the results of the indentation data from thicker films do not compare well to the x-rays data due to the presence of a residual stress distribution.
Abstract: Stress relaxation in aluminum films of several thicknesses was characterized by using both continuous indentation and x-ray diffraction techniques. Results of the indentation and x-ray stress measurements compare closely for films of small thicknesses. Indentation data from thicker films do not compare well to the x-ray data due to the presence of a residual stress distribution.
97 citations
TL;DR: In this paper, an elastoplastic analysis of axisymmetric conical indentation has been made using the finite element method, and the results show that the shapes of the plastic zones depend strongly on both indenter angle and the ratio of Young's modulus to yield strength.
86 citations
TL;DR: In this article, the authors describe a dynamic indentation (DI) technique suitable for the determination of the high strain rate flow behavior of ductile metals and alloys and illustrate its use by characterizing the high-strain rate flow behaviour of iron and OFHC copper.
Abstract: The objective of the paper is to describe a dynamic indentation (DI) technique suitable for the determination of the high strain rate flow behaviour of ductile metals and alloys and illustrate its use by characterizing the high strain rate flow behaviour of iron and OFHC copper. The DI technique is first described in detail and the dynamic hardness-strain data of iron and copper obtained using the technique is presented. It is also demonstrated that it is a suitable technique for characterizing the high strain rate flow behaviour as long as certain validity conditions are met. It is shown that these validity conditions are fully met in the case of copper and at low strain levels in iron. The reliability of the DI technique is finally demonstrated by comparing the present data with the literature data on similar materials and finally a critique of the DI technique is provided.
84 citations
15 Aug 1991-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a normalized Meyer's law was proposed to explain the Knoop microhardness anisotropy by applying the effective resolved shear stress concept advanced by Brookes and coworkers, yielding P 2P c n d d d 0 ∗ η where Pc is a critical test load indicative of the region where hardness is independent of the indentation test load and d 0 is a characteristic indentation dimension.
Abstract: Knoop microhardness profiles were determined for lanthanum hexaboride (LaB6) on the (100), (110) and (111) planes for indentation test loads from 50 to 300 gf. These profiles were analyzed with respect to possible slip systems to explain the Knoop microhardness anisotropy by applying the effective resolved shear stress concept advanced by Brookes and coworkers. As the results of this study, the predicted slip systems for LaB6 are {100}〈011〉,{110}〈111〉 and {111}〈110〉. The load dependence of the microhardness was initially addressed in terms of the classical Meyer's law P = Adn for which the two parameters A and n were observed to be related. The peculiar dimensionality of the classical Meyer's law coefficient A was addressed by applying the concepts of a load-independent “true” microhardness, critical indentation load and characteristic indentation size. Subsequently the development of a normalized Meyer's law was directly demonstrated, yielding P= 2P c n d d 0 ∗ η where Pc is a critical test load indicative of the region where hardness is independent of the indentation test load and d 0 ∗ is a characteristic indentation dimension, below which the indentation size effect is significant. It is suggested that this normalized Meyer's law may have universal applicability to different hardness tests and materials.
TL;DR: In this paper, a Multigrid extension of a stationary solver is outlined for the EHL solution of a line contact under transient conditions, which is applied to calculate pressure and film thickness profiles at each time step.
Abstract: In this paper a Multigrid extension of a stationary solver is outlined for the EHL solution of a line contact under transient conditions. The solver is applied to calculate pressure and film thickness profiles at each time step when an indentation is moving through the contact, which results in an asymmetric pressure profile. The time-dependent results are compared with the stationary solutions. The pressure as a function of time is presented as well as the integrated pressure (over time) as a function of the spatial coordinate. These time-dependent pressures are used to compute the sub-surface stress field, which shows higher stresses below the trailing edge of the indentation. Therefore the risk of fatigue is higher below the trailing edge of the indentation, as is experimentally observed. The transient pressures can be used for a fundamental study of the emitted frequency spectrum of rolling bearings, as used in condition monitoring.
TL;DR: The mechanical properties of single-quasicrystals of decagonal AlCoCuSi have been studied for the first time by applying the Vickers indentation method as discussed by the authors.
Abstract: The mechanical properties of single-quasicrystals of decagonal AlCoCuSi have been studied for the first time by applying the Vickers indentation method. The hardness has been determined as H ≃ 9.6 MPa. Estimates for the modulus of elasticity and the fracture toughness are given. The quasicrystals are highly strained internally. Scratching experiments show slight anisotropies in the abrasive friction coefficient. The dominant abrasive mechanism is microplowing.
TL;DR: A fracture mechanics model for subthreshold indentation flaws is described in this article, which describes the initiation and extension of a micro-crack from a discrete deformation-induced shear-fault (shear crack) within the contact zone.
Abstract: A fracture mechanics model for subthreshold indentation flaws is. described. The model describes the initiation and extension of a microcrack from a discrete deformation-induced shear “fault” (shear crack) within the contact zone. A stress-intensity factor analysis for the microcrack extension in residual-contact and applied-stress fields is used in conjunction with appropriate fracture conditions, equilibrium in Part I and non-equilibrium in Part II, to determine critical instability configurations. In Part I, the K-field relations are used in conjunction with the Griffith requirements for crack equilibrium in essentially inert environments to determine: (i) the critical indentation size (or load) for spontaneous radial crack pop-in from a critical shear fault under the action of residual stresses alone; (ii) the inert strengths of surfaces with subthreshold or postthreshold flaws. The theory is fitted to literature data for silicate glasses. These fits are used to “calibrate” dimensionless parameters in the fracture mechanics expressions, for later use in Part II. The universality of the analysis in its facility to predict the main features of crack initiation and propagation in residual and applied fields will be demonstrated. Special emphasis is placed on the capacity to account for the significant increase in strength (and associated scatter) observed on passing from the postthreshold to the subthreshold domain.
TL;DR: In this paper, the temperature dependence of hardness and micro-cracking in single-crystal 9.5-mol pct-Y2O3-fully-stabilized cubic-ZrO2 was studied as a function of orientation.
Abstract: The temperature dependence of hardness and microcracking in single-crystal 9.5-mol pct-Y2O3-fully-stabilized cubic-ZrO2 was studied as a function of orientation. Crack lengths increased with increased temperature up to 500 C; above 800 C, no cracks were found, indicating an indentation brittle-to-ductile transition of about 800 C. The temperature dependence of hardness was reduced around 500 C. Etching studies to delineate the plastic zone around and below indents identified the operative slip systems. The role of dislocations and their interactions within the plastic zone on the hardness and indentation fracture behavior of cubic-ZrO2 are discussed.
TL;DR: In this article, the authors evaluated the constraint factor associated with the indentation process as a function of strain in the case of metallic materials exhibiting a wide range with respect to elastic modulus, strength, and strain-hardening rate.
Abstract: It is generally accepted that the constraint factor (CF) associated with the indentation of metallic materials by a much harder indentor is in the range of 2.8 to 3.0. Invariably, the CF is assumed to have a constant value in the above range irrespective of the material indented while correlating the hardness of the material indented with its uniaxial strength properties. The objective of the present investigation is to assess the above assumption by evaluating the CF associated with the indentation process as a function of strain in the case of metallic materials exhibiting a wide range with respect to elastic modulus, strength, and strain-hardening rate. The results indicate that the CF is not really a constant but is dependent on the various material properties. The experimental CF-strain relationship observed in all of the test materials has been rationalized on the basis of elastic-plastic and fully plastic indentation models. While the theoretical models can explain the trend of the data, they are not capable of making adequately accurate quantitative predictions.
TL;DR: In this paper, a relation between average coordination number and Vickers hardness number for chalcogen-rich glasses was refined and discussed in relation to rigid percolation concepts.
Abstract: Several high purity chalcogenide glasses were prepared by vacuum melting of previously distilled and/or surface oxide removed 5 to 6-nines pure Ge, Sb, Se, As and Te. Vickers hardness number and indentation toughness were measured using the microindentation technique. A previously proposed empirical relation between average coordination number and Vickers hardness number for chalcogen-rich chalcogenide glasses was refined and is discussed in relation to ‘rigidity percolation’ concepts.
TL;DR: In this paper, two separate phenomena occur during the low-load indentation of silicon which make its behavior distinctly different from that of most materials, and they are documented and discussed.
Abstract: Two separate phenomena occur during the low-load indentation of silicon which make its behavior distinctly different from that of most materials. First, silicon is one of only a very few materials whose hardness exceeds the pressure needed to transform it to a denser crystalline (or amorphous) form, and because of this, a reversible, pressure-induced phase transformation occurs during indentation. The transformation enhances the electrical conductivity of the material and creates a region around the indenter which flows like a soft metal. Second, silicon cracks when indented by a Berkovich or Vickers indenter at loads of less than 100 mN, i.e., loads typically used in nanoindentation experiments. These two phenomena, which account for a number of unusual features in the indentation load-displacement behavior, are documented and discussed.
TL;DR: In this article, the fracture toughness of chemically vapor-deposited diamond is estimated by a Vickers indentation method using a microhardness tester using a load range of 5 to 8 N. The average fracture toughness is estimated as 5.3 ± 1.3 MPA · m 1/2.
Abstract: The fracture toughness of chemically vapor-deposited diamond is estimated by a Vickers indentation method. Freestanding diamond films of 400-μm thickness are produced with plasma-enhanced chemical vapor deposition and highly polished for indentation testing. Indentation testing was performed with a microhardness tester using a load range of 5 to 8 N. The average fracture toughness is estimated as 5.3 ± 1.3 MPA · m1/2.
TL;DR: In this article, a Hertzian indentation test for debonding of thin refractory coatings between two oxides has been investigated by developing a new simple indentation technique.
Abstract: Debonding of thin refractory coatings between two oxides has been investigated by developing a new, simple indentation test technique. The method is based on a Hertzian indentation approach, modified to incorporate crack propagation down an interface plane beneath and parallel to the indented surface. The test method has been analyzed using finite elements and the results validated by experiments on homogeneous solids. Test materials have been selected to distinguish coatings capable of debonding from those immune from debonding. The implications for fiber coatings suitable for use in high temperature oxide based composites have been discussed.
Patent•
10 May 1991
TL;DR: In this article, a preload indicating washer is described, in which a plurality of protuberances, struck and partially sheared from the annular body of the washer, are pushed under load back into a corresponding plurality of indentations.
Abstract: A pre-load indicating washer in which a plurality of protuberances, struck and partially sheared from the annular body of the washer, are pushed under load back into a corresponding plurality of indentations in the annular body which are formed when the protuberances are formed. The mass of material defined by each protuberance/indentation pair is concentrated along the lengthwise central region of the protuberance/indentation pair, thereby stiffening the protuberance, so that when load is applied to the washer, the protuberance will first undergo elastic deformation prior to collapsing back into the indentation from which it was formed.
TL;DR: In this article, the Vickers hardness of nanocrystalline (N-) TiO2 was measured in the temperature range 25° to 1200°C and it was compared with that of polycrystalline(P-)TiO2 in the same temperature range.
Abstract: Vickers hardness of nanocrystalline (N-) TiO2 was measured in the temperature range 25° to 1200°C and it was compared with that of polycrystalline (P-) TiO2 in the same temperature range. N-TiO2 showed a lower hardness than P-TiO2 at temperatures up to 800°C which resulted in the lack of indentation crack traces for N-TiO2 presumably implying more plasticity.
TL;DR: In this article, the authors evaluated the applicability of the indentation test as compared with tensile tests for estimating the stress exponent of Pb and Pb-Cu alloys with small Sn, Se and Pd additions.
Abstract: Stress exponent values have been determined in Pb and Pb-Cu alloys with small Sn, Se and Pd additions by indentation methods (long time hardness tests) to evaluate their applicability as compared with tensile tests. Homogeneous, fine grained alloys were obtained by induction melting and thermo-mechanical treatments. Grain size was 38–60 μm in alloys and 183 μm in pure lead. Stress exponent values, i.e. of 11–12 agree between different methods of derivation and, in fine grained material, with tensile methods. The largest differences in pure lead, i.e. 10–11 versus 7–8 are attributed to high strain rates when indentation size is comparable to grain size. In all cases indentation and tensile tests indicate the same deformation mechanism, namely slip creep. The indentation test is thus considered useful, within limits, to acquire information on the deformation mechanism.
TL;DR: In this article, the influence of environment on the cyclic fatigue behavior of a high-purity alumina bioceramic was investigated using the repeated indentation technique, and it was concluded that the effects of fluid environments on the growth of cyclically driven cracks must be an integral part of the mechanism responsible for cyclic fatigues in ceramics.
Abstract: The influence of environment on the cyclic fatigue behavior of a high-purity alumina bioceramic was investigated using the repeated indentation technique. Tests were conducted in the presence of water, a variety of alcohols, toluene, and simulated physiological fluid environments. The results show that these environments do not have any detectable effect on the damage produced by single indentations, but those containing water cause a significant degradation in cyclic fatigue resistance which cannot be quantified in terms of known subcritical crack growth behavior in static fatigue. It is concluded that the effects of fluid environments on the growth of cyclically driven cracks must be an integral part of the mechanism responsible for cyclic fatigue in ceramics.
TL;DR: In this paper, the authors measured fracture toughness on the major planes of single-crystal silicon using the controlled surface flaw (CSF) and indentation fracture (IF) methods at room temperature.
Abstract: Fracture toughness (KIC) values were measured on the major planes of single-crystal silicon using the controlled surface flaw (CSF) and indentation fracture (IF) methods at room temperature. The values of KIC on the surface orientations {100}, {110}, {111} and {112} obtained by the CSF method were found to be 1.13, 1.12-1.14, 1.18 and 1.11-1.18MPa·m0.5, respectively. It was found that these KIC values increased slightly with increasing the Young's modulus perpendicular to the fracture surfaces. Though KIC values obtained by the IF method, on the other hand, were scattered significantly (0.82-1.18MPa·m0.5), its Young's modulus dependence was similar to that obtained by CSF method.
TL;DR: In this paper, an indentation method was used to measure the toughness of Y-TZP and the K 1c value was calculated using different indentation equations, and it was shown that all the indentation cracks were Palmqvist cracks.
TL;DR: In this article, a method for measuring the fracture toughness of ceramics using small disk-shaped samples 3 mm in diameter was proposed, which involves the Vickers indentation of specimens ranging in thickness from 300 to 700 m, and testing them in a ring-on-ring bending mode.
Abstract: Novel apparatus and methodology have been developed for measuring the fracture toughness of ceramics using small disk-shaped samples 3 mm in diameter. The method involves the Vickers indentation of specimens ranging in thickness from 300 to 700 {mu}m, and testing them in a ring-on-ring bending mode. Experiments on ZnS grown by chemical vapor deposition (CVD) have been used to evaluate the technique. The apparent fracture toughness of this material increases with crack length (R-curve behavior). This behavior is analyzed using established equations in conjunction with a new graphical method that obviates the need for measuring the apparent toughness of samples containing very large cracks. The fracture toughness at infinite'' crack length, 0.86{plus minus}0.08 MPa{center dot}m{sup 1/2}, is in very good agreement with the values obtained by conventional methods. The effect of sample size on the accuracy of the results is thoroughly discussed. The thickness, {ital t}, of the sample should exceed by a factor of ten the initial crack length produced by the indentation. Also, since samples are tested at various indentation loads, {ital P}, the ratio of their thicknesses should be chosen to satisfy the condition {ital t}{proportional to}{ital P}{sup 2/3}. The importance of several parameters in the designmore » of the apparatus is also discussed.« less
TL;DR: In this article, the authors investigated the indentation behavior of Ce-TZP, Y-TzP, and Mg-PSZ between room temperature and 1300 C. Hardness decreased with increasing temperature for all three materials.
Abstract: Indentation behavior of Ce-TZP, Y-TZP, and Mg-PSZ between room temperature and 1300 C was investigated. Hardness decreased with increasing temperature for all three materials, but indentation cracking increased with increasing temperature. The opposing temperature dependences are discussed in terms of dislocation and transformation plasticity.
TL;DR: In this paper, the boundary fractal dimension of planar sections through particles produced by fracturing a series of brittle intermetallic V3Au materials with increasing oxygen content provides a single parameter that describes the surface roughness.
Abstract: Determination of the boundary fractal dimension of planar sections through particles produced by fracturing a series of brittle intermetallic V3Au materials with increasing oxygen content provides a single parameter that describes the surface roughness. This is observed to correlate with the measured fracture toughness, K1c, as determined with an indentation cracking test. The correlation agrees quantitatively with results obtained on several brittle ceramics by other workers.