The traditional way of determining the local interfacial shear strength (IFSS), τd, between the fiber and the matrix in microbond and pull-out test includes the measurement of the debond force, Fd, ...at which interfacial crack initiates, and subsequent τd calculation using the shear-lag analysis. However, for some fiber–matrix pairs the debond force, which manifests itself as a ‘kink’ in the force–displacement curve, cannot be reliably measured. We propose a new approach, based on measuring the maximum pull-out force, Fmax, and the initial post-debonding force, Fb, which does not require the knowledge of the Fd value. The comparison of the τd values calculated for several fiber–matrix pairs using three different methods of data reduction demonstrated that the new method yielded results very similar to the traditional one. Thus, it can be recommended as an alternative technique if the debond force is indeterminable.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Our ‘alternative’ method of determining interfacial strength parameters in the pull-out and microbond test, based on measuring the maximum pull-out force, Fmax, and the initial post-debonding force, ...Fb, has been extended to the energy-based approach (estimation of the interfacial toughness, Gic, and the interfacial frictional stress, τf). The comparison of the Gic values calculated using the proposed method and the traditional one (using the debond force, Fd, instead of Fb) for several fiber–matrix systems showed that both methods yielded very similar results. Thus, the new method can be recommended as an additional technique of Gic determination to be used instead of, or together with the traditional approach.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
For the establishment of a novel development process of new structural materials, short-term characterization methods capable of testing hundreds of spherical micro samples are needed. This paper ...introduces a compression test on spherical micro samples as a short-term characterization method to investigate the elastic-plastic deformation behavior. To demonstrate the potential of this newly developed method, the micro compression test is performed with a maximum loading of 300 N on 100Cr6 (AISI 52100 bearing steel) samples, with a diameter of 0.8 mm, in 15 different heat treatment conditions. The austenitizing temperature is varied between 800 and 1150 °C. Tempering of the samples is carried out in a differential scanning calorimetry process with temperatures of 180, 230 and 300 °C. Out of force-displacement curves and stress-strain relations, so-called descriptors (characteristic values) which are sensitive to the applied heat treatment can be extracted. The change of mechanical properties due to heat treatment and the resulting microstructure is presented by the trend of a stress descriptor in dependence of austenitizing and annealing temperature, which can be compared to the trend of the tensile strength as a material property obtained by conventional tensile tests. The trend of the descriptor determined in the compression test on spherical samples indicates the validity of this approach as a short-term characterization method.
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Mechanical response and energy absorption of aluminium foam sandwich panels subjected to quasi-static indentation loads were investigated experimentally. These sandwich panels consisted of two ...aluminium face-sheets and a closed cell aluminium foam core (ALPORAS®). Quasi-static indentation tests were conducted using an MTS universal testing machine, with sandwich panels either simply supported or fully fixed. Force–displacement curves were recorded and the total energy absorbed by sandwich panels was calculated accordingly. Videos and photographs were taken to capture the deformation of top face-sheets, foam cores and bottom face-sheets. Effects of face-sheet thickness, core thickness, boundary conditions, adhesive and surface condition of face-sheets on the mechanical response and energy absorption of sandwich panels were discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The interosseous membrane (IOM) of the forearm plays a crucial role in facilitating forearm function and mechanical load transmission between the radius and ulna. Accurate characterization of its ...biomechanical properties is essential for developing realistic finite element models of the forearm. This study aimed to investigate the mechanical behavior and material properties of the central fibrous regions of the IOM using fresh frozen cadavers. Ten forearms from five cadavers were dissected, preserving the IOM and identifying the distal accessory band (DAB), central band (CB), and proximal accessory band (PAB). Bone-ligament-bone specimens were prepared and subjected to uniaxial tensile testing, with the loading direction aligned with the fiber orientation. Force-displacement curves were obtained and converted to force-strain and stress–strain curves using premeasured fiber lengths and cross-sectional areas. The results demonstrated distinct mechanical responses among the IOM regions, with the PAB exhibiting significantly lower force-strain behavior compared to the DAB and CB. The derived force-strain and stress–strain relationships provide valuable insights into the regional variations in stiffness and strength of the IOM, highlighting the importance of considering these differences when modeling the IOM in finite element analysis. In conclusion, this study establishes a foundation for the development of advanced finite element models of the forearm that accurately capture the biomechanical behavior of the IOM.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
One of the most popular micromechanical techniques of determining the local interfacial shear strength (local IFSS,
) between a fiber and a matrix is the single fiber pull-out test. The
values are ...calculated from the characteristic forces determined from the experimental force⁻displacement curves using a model which relates their values to local interfacial strength parameters. Traditionally, the local IFSS is estimated from the debond force,
, which corresponds to the crack initiation and manifests itself by a "kink" in the force⁻displacement curve. However, for some specimens the kink point is hardly discernible, and the "alternative" method based on the post-debonding force,
, and the maximum force reached in the test,
, has been proposed. Since the experimental force⁻displacement curve includes three characteristic points in which the relationship between the current values of the applied load and the crack length is reliably established, and, at the same time, it is fully determined by only two interfacial parameters,
and the interfacial frictional stress,
, several methods for the determination of
and
can be proposed. In this paper, we analyzed several theoretical and experimental force⁻displacement curves for different fiber-reinforced materials (thermoset, thermoplastic and concrete) and compared all seven possible methods of
and
calculation. It was shown that the "alternative" method was the most accurate and reliable one, while the traditional approach often yielded the worst results. Therefore, we proposed that the "alternative" method should be preferred for the experimental force⁻displacement curves analysis.
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To determine the contact response and damage tolerance or strength degradation of a range of dental CAD/CAM ceramic materials including novel polymer-infiltrated-ceramic-network (PICN) materials by ...means of spherical indentations at various loads and indenter radii.
The seven tested materials included Mark II, PICN test materials 1 and 2, In-Ceram Alumina, VM 9, In-Ceram YZ (Vita Zahnfabrik, Bad Saeckingen, Germany) and IPS e.max CAD, (Ivoclar Vivadent, Schaan, Liechtenstein). To evaluate the damage tolerance and role of indenter size, indentations with tungsten carbide spheres (0.5mm and 1.25mm radius) were placed on bending bars with varying loads (1.96–1000N). The indented bending bars were subsequently loaded to fracture in three-point bending. The contact induced damage was analyzed by light microscopy (LM) and SEM. The spherical contact response was measured on polished surfaces.
The initial strengths for the individual materials were found to reduce above specific indentation loads, which were a function of the indenter radius. Employing a 0.5mm radius sphere resulted in the following strength degrading loads and ordering of materials: VM9 (98N)<MarkII–PICN1 (147N)<ICAlumina–e.maxCAD (300N)<PICN2–YTZP (500N). For the materials indented with the 1.25mm sphere, higher loads were required for the onset of strength degradation: VM9 (190N)<MarkII (300N)<PICN1 (400N)<e.maxCAD (500N)<ICAlumina (700N)<PICN2 (1000N)<YTZP (above 1000N). Two different damage modes were observed by SEM and LM – brittle cone cracking and plastic deformation. The PICN materials exhibited elastic–plastic behavior with creep. In contrast YTZP showed entirely elastic behavior upon loading with both spheres.
This study aims to emulate the likely clinical behavior of contact loading by opposing cusps to dental restorative ceramic materials by utilizing spherical indentations at various loads and sphere diameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The force-displacement relationship is a fundamental mechanical property of materials, and the ability to inversely customize a prespecified relationship is useful for complex energy absorption ...systems, substrates of wearable electronics, and programmable vibration control. The recent development of mechanical metamaterials introduces graded strength into porous frameworks, which, however, can only achieve designable strain-hardening behavior. This is because the soft layers always deform prior to the hard layers due to the minimum energy gradient principle, regardless of the spatial arrangement of the component strength. Inspired by the “Domino effect” of tube inversion where its deformation sequence is governed by its kinematic compatibility, this paper introduces graded strength into a progressive and sequential tube inversion process, and correspondingly achieves arbitrarily prescribable force-displacement curves. Parametric study, numerical simulations for 9 different target curves, theoretical modeling leading to an inverse design framework, and experiments are carried out. This strategy paves the way for the inverse design of materials with arbitrary nonlinear mechanical responses essential for various novel applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
9.
Mechanics of plant fruit hooks Chen, Qiang; Gorb, Stanislav N.; Gorb, Elena ...
Journal of the Royal Society interface,
04/2013, Volume:
10, Issue:
81
Journal Article
Peer reviewed
Open access
Hook-like surface structures, observed in some plant species, play an important role in the process of plant growth and seed dispersal. In this study, we developed an elastic model and further used ...it to investigate the mechanical behaviour of fruit hooks in four plant species, previously measured in an experimental study. Based on Euler–Bernoulli beam theory, the force–displacement relationship is derived, and its Young's modulus is obtained. The result agrees well with the experimental data. The model aids in understanding the mechanics of hooks, and could be used in the development of new bioinspired Velcro-like materials.
Actual shape of the indenter is very important parameter affecting the results and interpretation of nanoindentation tests. In this study, bluntness of the tip was determined by direct (atomic force ...microscopy) and indirect methods (indentation into reference materials) for different states of the indenter over its lifetime. It was found that the equivalent radius depends on the used analysis method. Moreover, equivalent radius changes with the distance from indenter apex. Axisymmetric 2D sphero-conical and 3D finite element models of the indenter geometry were used to predict force-displacement curves which were compared with experiment. It was shown, that there exists a significant difference between 2D and 3D models caused by the simplifications of actual 3D shape of Berkovich indenter by sphero-conical model. The sphero-conical model can serve as good estimator of indenter bluntness and it is convenient for the description of the indenter wear throughout its lifetime.
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•Bluntness of Berkovich indenter examined throughout the period of two years using AFM and indirect analyses.•Estimation of equivalent radius of spherical part depends on indenter state and analysis employed.•Equivalent radius of spherical part of Berkovich indenter increases with depth of penetration.•Proposed methods are suitable for monitoring of the indenter wear.
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