Indentation Load Research Articles

The research of tool wear criterion in micro cutting using the elastic recovery ratio of high-strength elastic alloy 3J33B

In this study, indentation experiments were conducted on high-strength elastic alloy 3J33B material with a Berkovich indenter to study the elastic recovery of material. The experimental data showed that the load and material properties influence elastic recovery ratio of material. The functional expressions of elastic recovery ratio and load were established by regression analysis of experimental data. Therefore, the depths of elastic recovery of 3J33B can be controlled by adjusting the indentation load. Alloy 3J33B has the property of high elastic energy, so it is easy to produce large elastic recovery in the machining. Based on the functional expressions of elastic recovery ratio and load, it can be obtained that the relationships among the elastic recovery ratio of the machined surface, the yield strength of the material, the clearance angle, the average sliding friction coefficient between the tool and the workpiece, the wear width of the flank face and the cutting width. Then, the critical values of tool wear at different clearance angles can be obtained when the yield strength of material, the average sliding friction coefficient between the tool and the workpiece and the cutting width are known. Then, a group of micro milling experiments were conducted on alloy 3J33B using several single-edge micro milling cutters. Finally, it can be obtained that the clearance angle of cutting tool should not be more than 34° in micro cutting in order to reduce the tool wear.

On the origins of ultra-high hardness and strain gradient plasticity in multi-phase nanocrystalline MoNbTaTiW based refractory high-entropy alloy

In this paper, we report a remarkably high hardness in fully-dense nanocrystalline multi-phase MoNbTaTiW based refractory high-entropy alloy which was prepared by ball milling and spark plasma sintering. A single phase BCC structure was realized after 30 h of milling whereas sintering led to the decomposition of the as-milled complex lattice into a BCC and two FCC phases. Vickers microindentation performed at various loads led to the observation of pronounced indentation size effect with hardness in the range 18.87-13.89 GPa. It appears that Ti and Fe (from processing media) are responsible for the multi-phase structure realized as well as extraordinarily high absolute hardness (13.89 GPa at 500 g load) and “density-normalized hardness”. These values are the highest reported so far in the family of MoNbTaW alloys. Comprehensive analysis on strengthening mechanisms responsible for the extraordinarily high hardness observed in this alloy indicates that solid solution strengthening and grain boundary (Hall-Petch) strengthening are the dominant factors while lattice frictional stress and Taylor hardening also contribute to some extent. The strain gradient plasticity appears to follow the considerations based on the concept of geometrically necessary dislocations and the characteristic multi-phase structure of this alloy. The back stress that would develop in order to have compatible deformation during the indentation at low loads is also expected to contribute to higher hardness values observed at low indentation loads. The depth-independent hardness of 11.80 GPa and a characteristic length scale of 1.07 μm were realized from the analysis. Achieving of ultra-high hardness in this alloy suggests that careful microstructural engineering as well as optimal addition of alloying elements would be beneficial towards development of novel structural materials based on multi-principal element approach.

Toughness and R-curve behaviour of laminated Si3N4/SiCw ceramics

Laminated Si3N4/SiCw ceramics were successfully prepared by tape casting and hot-pressing. Its mechanical properties were measured and the impact resistance was discussed. The toughness of the laminated Si3N4/SiCw ceramics was 13.5 MPa m1/2, which was almost 1.6 times that of Si3N4/SiCw composite ceramics, namely 8.5 MPa m1/2. Moreover, the indentation strength of laminated Si3N4/SiCw ceramics was not sensitive to increasing indentation loads and exhibited a rising R-curve behaviour, indicating that the laminated Si3N4/SiCw ceramics had excellent impact resistance. The improved toughness and impact resistance of laminated Si3N4/SiCw ceramics was attributed to the residual stress caused by a thermal expansion coefficient mismatch between the different layers, resulting in crack deflection and bridging of SiC whiskers in the interface layer, thus consuming a large amount of fracture work.

Collagen fibres determine the crack morphology in articular cartilage

Cracks in articular cartilage compromise tissue integrity and mechanical properties and lead to chondral lesions if untreated. An understanding of the mechanics of cracked cartilage may help in the prevention of cartilage deterioration and the development of tissue-engineered substitutes. The degeneration of cartilage in the presence of cracks may depend on the ultrastructure and composition of the tissue, which changes with aging, disease and habitual loading. It is unknown if the structural and compositional differences between immature and mature cartilage affect the mechanics of cartilage cracks, possibly predisposing one to a greater risk of degeneration than the other. We used a fibre-reinforced poro-viscoelastic swelling material model that accounts for large deformations and tension-compression non-linearity, and the finite element method to investigate the role of cartilage structure and composition on crack morphology and tissue mechanics. We demonstrate that the crack morphology predicted by our theoretical model agrees well with the histo-morphometric images of young and mature cracked cartilages under indentation loading. We also determined that the crack morphology was primarily dependent on collagen fibre orientation which differs as a function of cartilage depth and tissue maturity. The arcade-like collagen fibre orientation, first discussed by Benninghoff in his classical 1925 paper, appears to be beneficial for slowing the progression of tissue cracks by ‘sealing’ the crack and partially preserving fluid pressure during loading. Preservation of the natural load distribution between solid and fluid constituents of cartilage may be a key factor in slowing or preventing the propagation of tissue cracks and associated tissue matrix damage. Statement of significanceCracks in articular cartilage can be detrimental to joint health if not treated, but it is not clear how they propagate and lead to tissue degradation. We used an advanced numerical model to determine the role of cartilage structure and composition on crack morphology under loading. Based on the structure and composition found in immature and mature cartilages, our model successfully predicts the crack morphology in these cartilages and determines that collagen fibre as the major determinant of crack morphology. The arcade-like Benninghoff collagen fibre orientation appears to be crucial in ‘sealing’ the tissue crack and preserves normal fluid-solid load distribution in cartilage. Inclusion of the arcade-like fibre orientation in tissue-engineered construct may help improve its integration within the host tissue.

Abrasive Sensitivity of Martensitic and a Multi-Phase Steels under Different Abrasive Conditions.

The wear behaviour of two martensitic and one multiphase steel targeted for abrasion and erosion applications in agriculture and mining industry were investigated in three abrasive test systems with different complexity. Scratch tests were performed with different indenter radii, shapes, and loads. The material behaviour was also investigated in multi-asperity contact systems. Pin-on-disc tests were performed with various loads and abrasive particles, as well as abrasive slurry-pot tests with different sliding velocities, distances, and impact angles of the abrasive media were performed. Comparing the test systems, the tested materials ranked similarly based on their wear performance, however, in each configuration, the dominant variable of the wear mechanism differed. The significance and contributions of test paramecenterters, the material’s mechanical properties (H, , , E, , , W, , ) and the dimensionless numbers formed from them were investigated on the wear behaviour and the surface deformation. Correlation between parameters was established by multiple linear regression models. The sensitivity of the tested materials to abrasion was evaluated taking into account the wide range of influencing parameters.

Quantitative kink boundaries strengthening effect of Mg-Y-Zn alloy containing LPSO phase

This study represents the quantitative kink-band strengthening effect using uniaxial hot-compressed Mg-9%Y-6%Zn alloy. When room-temperature micro-Vickers indentation was performed on a specific area containing kink boundaries under a low indentation load of 10 gf, the magnitude of increase in hardness due to kink-band strengthening was closely related with the number of kink boundaries beneath the indentation, i.e., the kink-band strengthening effect can be expressed by the number of kink boundaries. It is noted that this increased value is calculated by subtraction from the hardness value of the matrix without kink boundaries. The present estimated kink-band strengthening values via microscopic empirical analysis is in a similar range to those of prior macroscopic analysis obtained from the results of compression tests using bulk specimens.

An overview of instrumented indentation technique for the study of micromechanical properties in food: A case study on bean seed coat

Food texture features depend on the structure–property-functionality relationship and mechanical properties. This work describes the application of the instrumented indentation technique (IIT) to determine the micromechanical properties of the bean seed coat evaluating different indentation loads. The bean seed coat's multilayer structure is composed of a cuticle (C), palisade cells (PAL), subepidermal pillar cells (SE), and spongy parenchyma cells (SP). Values of Ra and Rq revealed a rough surface due to the waxes and minerals present in the C. In the indentation tests, the C was indented at loads below 20 mN exhibiting values of hardness (H) and elastic modulus (E) of 383 ± 58 MPa and 11 ± 5 GPa, respectively. For PAL, when the load increased to 400 mN, H and E decreased to 198 ± 29 MPa and 3 ± 0.8 GPa, indenting 10% of the total thickness of the seed coat (103 ± 9 μm). The values of H and E decreased as the applied indentation load increased. This variability is influenced by the composition (waxes, lignin, condensed tannins, and CaOx crystals) and the effect of the layer-substrate system of multilayer structure of the seed coat.

나노압입시험을 통한 양극산화 알루미늄의 두께에 따른 물성 측정

Anodic aluminum oxide (AAO) is widely used in various industrial fields to increase the mechanical property or corrosion resistance of the product surface. In this study, mechanical properties were measured according to the thickness of AAO through the nanoindentation test. The maximum indentation load, elastic modulus, and hardness were measured for different thicknesses of AAO. It was confirmed that the majority of the mechanical property values increased with the thickness. Various fracture shapes based on the thickness were analyzed by observing pressure marks on the surface using FE-SEM equipment. Apparently, it is proposed that the optimum AAO thickness with desired mechanical properties can be obtained, which is expected to possess immense economic value as per the optimization of the production time of AAO based products.

Revealing the relation between microstructural heterogeneities and local mechanical properties of complex-phase steel by correlative electron microscopy and nanoindentation characterization

Compositional and microstructural heterogeneity are characteristics of modern multiphase steels. However, the quantitative characterization of these heterogeneities is rarely considered in scientific publications. We characterized the compositional and microstructural heterogeneity of a commercial complex-phase steel (CP800) by combining various electron microscopy techniques and nanoindentation. Compositional gradients of C and Mn were characterized qualitatively and quantitatively through electron probe microanalysis (EPMA). Electron backscatter diffraction (EBSD) results were utilized to identify and segment the microstructural constituents. A novel nanoindentation approach was used to obtain hardness maps. Cube-corner indenter and micro-newton load were applied to limit the indent depth and spacing between adjacent indents to the nanometer scale. A high-resolution hardness map was obtained and successfully overlapped with EPMA and EBSD results, based on which the correlation between compositional heterogeneity and hardness variation in complex-phase microstructure was successfully established.

A dislocation-based yield strength model for nano-indentation size effect

This paper presents a dislocation-based yield strength model for the nano-indentation size effect. The model is based on functional expressions involving the densities of statistically stored dislocations and geometrically necessary dislocations. A single-phase austenitic stainless steel (316L) and a ferrite-austenite dual-phase steel (2205) are used here as the case-study materials to validate the proposed model. Experimental testing and finite element modelling of nano-indentation of the two materials are presented. Experimental tests are performed in the indentation load range from 1000[Formula: see text] to 10000[Formula: see text]. For 2205 steel, finite element modelling is performed using a dual-phase microstructure-based model. It is shown that, with consideration of statistically stored dislocations and geometrically necessary dislocations, finite element modelling results can reproduce measured load–displacement curves and hence, the size effect, within an error range of about 5%.

A phenomenological study of the influence of the hardening type on the indentation F-h cyclic curve

This paper is a phenomenological study representing the influence of the hardening type on the instrumented indentation F-h curve. Spherical instrumented indentation and inverse analysis techniques (IAT) are used and two metallic materials (DP600 and AA2017) are investigated. Pure isotropic (Voce) and combined (Chaboche 1986) hardening laws are adopted for describing the plastic behavior of the studied materials. The influence of the hardening type on the indentation loading curve is studied first. Kinematic hardening results in softening the indentation loading curve. This is due to some regions in the indented zone that undergo different loading paths during loading. Hardening types (kinematic & isotropic) should be considered to accurately characterize the mechanical behaviour of different metallic materials using indentation curves. The influence of the hardening type on the indentation unloading-reloading curve (hysteresis loop) is then studied. Kinematic hardening has an important influence on the hysteresis loop. This influence has been investigated closely and a methodology is proposed for estimating the contribution of each hardening type in the overall hardening behavior. This methodology is based on geometrical parameters directly influenced by the hardening type and presents great potential if considered in future works aiming to identify parameters of relatively complex hardening laws using the instrumented indentation technique (IIT).

EFFECTS OF PARTICLE SIZE AND SINTERING TEMPERATURE ON SUPERELASTICITY BEHAVIOR OF NiTi SHAPE MEMORY ALLOY USING NANOINDENTATION

The present study investigates the superelasticity properties of spark plasma sintered (SPS) nickel titanium shape memory alloy (NiTi SMA) with the influence of sintering temperature and particle size. The nanoindentation is conducted on the surface of the NiTi SMA at various loads such as 100, 300 and 500[Formula: see text]mN. The nanoindentation technique determines the quantitative results of elasto-plastic properties such as depth recovery in the form of superelasticity, stiffness, hardness and work recovery ratio from load–depth ([Formula: see text]–[Formula: see text]) data during loading and unloading of the indenter. Experimental findings show that the depth and work recovery ratio increases with the decrease of indentation load and particle size. In contrast, increasing the sintering temperature exhibited a better depth and work recovery due to the removal of pores which could enhance the reverse transformation. The contact stiffness is influenced by [Formula: see text] which leads to attain a maximum stiffness at the highest load (500[Formula: see text]mN) and particle size (45[Formula: see text][Formula: see text]m) along with the lowest sintering temperature (700∘C). NiTi alloy exhibited a maximum hardness of 9.46[Formula: see text]GPa when subjected to indent at the lowest load and particle size sintered at 800∘C. The present study reveals a better superelastic behavior in NiTi SMA by reducing the particle size and indentation load associated with the enhancement of sintering temperature.

In-situ synthesis of Boron Nitride Nanotube reinforced aluminum oxide composites by molecular mixing

Boron Nitride Nanotube (BNNT)/Al2O3 composite powders were prepared by molecular mixing of aqueous nanotube dispersions and aluminum ions. The composite powder was consolidated by spark plasma sintering where the ceramic phase underwent phase transformation to α-Al2O3 (amorphous→γ→α) while anchoring molecularly mixed BNNTs. The addition of 1.5 vol% BNNTs reduced the Al2O3 grain size by 50%, whereas microhardness increased by 22%. With an increasing BNNTs content from 0 to 1.5 vol%, high load (100 N) indentation showed that the residual indention area decreased by 65%, and morphology changed from severely brittle fracture to no visible cracks. Thus the addition of BNNTs leads to simultaneous improvement of strength and toughness of Al2O3. Crack bridging, BNNT pull-out, and crack deflection are the prime toughening mechanisms. Grain refinement of the Al2O3 matrix and effective load sharing is attributed to in-situ and homogeneously dispersed BNNTs, which are chemically bonded with the Al2O3 matrix at the molecular level.

Shear behavior of human skull bones

A shear-punch test (SPT) experimental method was developed to address the lack of shear deformation and failure response data for the human skull as a function of local bone microarchitecture. Improved understanding of skull deformation and fracture under varying stress-states helps implement mechanism-based, multi-axial material models for finite element analysis for optimizing protection strategies. Shear-punch coupons (N = 47 specimens) were extracted from right-parietal and frontal bones of three fresh-frozen-thawed human skulls. The specimens were kept as full through-thickness or segmented into the three skull constituent layers: the inner and outer cortical tables and the middle porous diploë. Micro-computed x-ray tomography (μCT) before and after SPT provided the bone volume fraction (BVF) as a function of depth for correlation to shear mechanisms in the punched volumes. Digital image correlation was used to track displacement of the punch above the upper die to minimize compliance error. Five full-thickness specimens were subjected to partial indentation loading to investigate the process of damage development as a function of BVF and depth. It was determined that BVF dominates the shear yield and ultimate strength of human skull bone, but the imposed uniaxial loading rate (0.001 and 0.1 s−1) did not have as strong a contribution (p = 0.181–0.806 > 0.05) for the shear yield and ultimate strength of the skull bone layer specimens. Shear yield and ultimate strength data were highly correlated to power law relationships of BVF (R2 = 0.917–0.949). Full-thickness and partial loaded SPT experiments indicate the diploë primarily dictates the shear strength of the intact structure.

Investigation of the Mechanical Integrity of Prismatic Li-Ion Batteries Under Multi-Position Indentation

Abstract Understanding the mechanical, thermal, and electrical properties of prismatic lithium-ion batteries (LIBs) is vital to battery safety design, which is key to electric vehicle safety. This study investigated prismatic LIBs subjected to multiple-position indentation loading. The side face of an intact prismatic LIB cell is divided into 15 compressed sections. Experimental results indicate that indentation loading of all sections could initiate thermal runaway. Among the sections studied, that near the positive terminal shows the highest risk of thermal runaway, whereas that near the top-right corner is relatively safe. Failure mode analysis reveals that short circuits may result from contact between the positive and negative current collectors.

Viscoelastic characterization of porcine brain tissue mechanical properties under indentation loading

The goal of this study was to measure the mechanical properties of porcine brain tissue and determine if they were dependent on anatomical region or direction. Multistep stress relaxation indentations with a cylindrical probe were performed at 10, 20, and 30% nominal strain on multiple regions in the sagittal, horizontal, and coronal planes. Linear and nonlinear (using the quasilinear theory of viscoelasticity [QLV]) constitutive formulations were applied to extract parameters to capture the mechanical behavior of brain tissue. The linear viscoelastic analytic approach provided the best fit to the experimental data of the models tested. Within each directional plane there were region-dependent differences. The cerebellum was the softest region within each loading direction. Although the majority of the regions were isotropic, the cerebellum white matter and thalamus were anisotropic. The characterization of these mechanical properties can be used to inform finite element models of the pig brain to help predict a more biofidelic response in animal models of traumatic brain injury. Statement of SignificanceFinite element models been developed to predict brain tissue response to traumatic brain injury (TBI) to advance protective and preventative strategies. In order to improve the accuracy of these computational models, appropriate mechanical experimentation is required to identify brain viscoelasticity, heterogeneity, and anisotropy. Our custom indentation design allows for high spatial resolution to characterize mechanical properties based on anatomical region and loading direction. Due to the challenges in procuring human brain tissue, porcine brain models are a suitable substitute to study TBI based on its structural similarities to that of human brains. This study will further illuminate the complexity of brain tissue mechanics in response to injury loading.

Analysis of micro indentation hardness of thiourea added L-histidine crystals (TLH)

Vickers microhardness analysis was carried out to identify the mechanical stability of the thiourea added L-histidine crystals (TLH) which were grown by slow evaporation solution growth technique at room temperature with different indentation loads. Indentation size effect (ISE) was investigated by analyzing the theoretical models. The microhardness values of the single crystal were calculated by using Meyer Law, proportional specimen resistance model, elastic/plastic deformation model and the Hays–Kendall (HK) approach. The results show that the HK approach is the most successful model to explain the deformations in the TLH single crystal. It is concluded that the RISE is a result of the specimen cracking during the indentation.

Effective Folding Line Processing with a Press Method in Origami Forming Using a Low-cost and Simple V-shaped Punch Tool System

Bent products have recently been applied widely in various structures. The method of sharp bending has the advantage of producing bent products with a fine appearance. Meanwhile, it has been recently shown that origami forming can be applied as a free manufacturing method that creates a fine appearance using complex folding lines. Sharp bending and origami forming both require folding lines. Folding lines are produced to make a V-groove before bending. Cutting V-grooves for folding lines requires machining center plants and long working times, which are not suitable for mass production. This paper presents newly developed and convenient V-shaped punch tools for folding line processing in sharp bending and origami forming. As a result, origami forming is expected to be adopted as a press method using V-shaped punch tools. Additionally, this paper reports on the findings of deformation behavior and mechanism obtained in experiments on folding line processing. The investigation for three-dimensional plate deformation around the V-shaped punch terminal shows extended folding line by terminal effect. Phenomena and the required load of V-shape punch indentation are considered in determining the mechanism of V-shape punch indentation from the results of finite element analyses and experiments on groove formation using V-shaped punch tool system.

Development and mechanical characterizations of Kevlar/C-glass epoxy hybrid composites

The work presents the mechanical investigation of Hybrid composite laminates that were fabricated following the Hand lay-up process which required matrix as epoxy been reinforced through Kevlar woven 29 grade type fiber and C glass type of hybrid fiber with different configurations. The obtained data from the mechanical tests of Hybrid composites by Indentation (hardness), impact, bending and tensile loads. ASTM standards were followed to conduct the tests. Images from the SEM helped to analyze and understand the interaction of matrix with reinforcement and its area of fracture which occurred under mechanical loads. Hybrid Composites with Kevlar as outer layer with glass fiber of category C in the hybrid arrangement in the reinforcements indicates improved results when compared with to bending, tensile strength, and energy from impact as well as hardness.

Nanoindentation study in cold gas dynamic sprayed thin films using molecular dynamics simulation

Abstract To enhance the efficiency of the cold gas dynamic spray (CGDS) technology-based metal composite membrane, it is extremely important to examine the mechanical characteristics of the CGDS coated thin films at the atomistic level. The nanoindentation test was performed in the present study on vanadium, copper and palladium thin film coated on niobium substrate by using molecular dynamic (MD) simulation. At the indentation region, the thermosetting control is applied with temperature variance from 300 K to 700 K. The results show that as the temperature decreases, the indentation load increases for loading and unloading processes. nanoindentation test was also performed at a different nanoindentation loading rate of 0.5–2.5 A/ps. The measured average hardness of the thin films by nanoindentation method increases in the order of vanadium, copper and palladium with the nanoindentation loading rate.