Variation Of Material Properties Research Articles

Mathematical Formulation and Numerical Simulation of the Mechanical Behavior of Ceramic/Metal (TiB/Ti) FG Sheets Subjected to Spherical Indenter

The main motivation for the present work is to provide an improved description of the response of Functionally Graded (FG) structures under a spherical indenter, considering material nonlinearities. This is achieved through the implementation of elastoplastic material behavior using integration points to avoid the division of the structure into multiple layers. The current paper proposes a numerical investigation into the mechanical response of functionally graded materials (FGMs) in contact with a rigid hemispherical head indenter. The numerical model considers both the Mori–Tanaka model and self-consistent formulas of Suquet to accurately model the smooth variation of material properties through the thickness of the elastoplastic FG material. The model execution involves a UMAT user material subroutine to implement the material behavior into ABAQUS/Standard. The user material UMAT subroutine is employed to introduce material properties based on the integration points, allowing for an accurate representation and analysis of the material’s behavior within the simulation. The developed numerical model is validated through a comparison with experimental results from the literature, showing a good correlation that proves the efficiency of the proposed model. Then, a parametric study is conducted to analyze the effect of the indenter dimension, the indentation depth and the gradient index on the indentation force, the contact pressure evolution, von Mises equivalent stress and equivalent plastic strain distributions located on the vicinity of the contact zone. The results showed that the elastoplastic response of TiB/Ti FG plates is significantly influenced by the gradient index, which determines the properties of the FG composite through the thickness. These results may help development engineers choose the optimal gradation for each industrial application in order to avoid contact damage.

An electromagnetic Hopkinson bar for low wave impedance material and complex stress paths loading tests

The split Hopkinson bar has been widely used for testing the dynamic mechanical properties of various materials. However, there are still difficulties in ensuring stress uniformity when testing some low wave impedance materials such as soft materials and brittle materials and difficulty in achieving true multi-axial and multi-directional synchronous loading experiments and other issues. To overcome these issues, this paper uses an electromagnetic Hopkinson bar for experimental research and introduces its principle and implementation process. Finite element analysis and experimental methods were used to verify the feasibility of the electromagnetic Hopkinson bar in addressing the relevant issues. The superiority of the new device was demonstrated by its capability in performing compression experiments on two typical low wave impedance materials: polymethacrylates (PMMA) and polyurethane (PU), and two-way tension experiments on 2024 aluminum alloy. The results indicate that the electromagnetic Hopkinson bar can effectively solve the problem of uniform stress in low wave impedance materials testing, and can achieve synchronous loading of complex stress paths.

Analysis of an interfacial crack between two nonhomogeneous piezoelectric materials using a new domain-independent interaction integral

Considering the difficulties introduced by piezoelectric material non-homogeneity and discontinuities to interfacial crack analysis, a domain-independent interaction integral (DII-integral) is proposed to derive the stress intensity factors (SIFs) and electric displacement intensity factor (EDIF) of an interfacial crack between nonhomogeneous piezoelectrics. For continuously varying material properties, traditional interaction integral (I-integral) needs to compute the derivatives of material parameters with respect to the x1 direction of the local coordinate system, while the proposed DII-integral is demonstrated to be unrelated to any derivatives of material parameters. Furthermore, a significant improvement is achieved that the new formulation of I-integral remains valid even when the integration domains include intricate and multiple interfaces, as long as the material interfaces are perfectly bonded. Firstly, the intensity factors (IFs) calculated by the combination of the DII-integral and the extended finite element method are compared with the analytical solutions, and it is found that the relative errors of the IFs are all less than 1.79 % with various crack lengths, which verifies the accuracy of the proposed method. For the piezoelectric bi-material model with continuously nonhomogeneous properties, the calculated IFs match each other well (relative deviation < 1.3 %) for different sizes of integration domains. In addition, for the perfectly bonded interface with discontinuous electromechanical properties, the IFs are almost identical (relative deviation < 0.85 %) whether or not the integration domain contains the material interface, which further numerically verifies the good domain-independence of the established DII-integral. For an interfacial crack near extra interfaces, the differences in elastic stiffness and piezoelectric coefficient between interface sides have an obvious influence on mode-I SIF, but mode-II SIF and EDIF are affected mainly by piezoelectric coefficient and dielectric permittivity.

Analysis of microstructure, surface morphology, and scratch resistance of high velocity oxy-fuel coated nickel based hybrid nano-composites

In recent years, high velocity oxygen fuel (HVOF) coating technology has gained significant interest in the field of surface engineering. In this study, we have investigated the microstructure, surface morphology, and scratch resistance of HVOF coated Nickel based novel hybrid nano-composites. The coatings were prepared using a high-velocity oxy-fuel (HVOF). HVOF coatings have the ability to enhance the surface properties of various materials, making them more resistant to wear, corrosion, and erosion. Thermal spraying technique, and the microstructure and surface morphology of the coatings were analyzed using scanning electron microscopy (SEM). The scratch test was performed using a TR-101, DUCOM made Scratch tester to evaluate the scratch resistance of the coatings. The results of the study revealed that the HVOF coated novel hybrid nano-composites exhibited a fine-grained microstructure with a dense and homogeneous surface morphology. The scratch resistance of the coatings was significantly improved due to the addition of nano composites. The load required to cause the first visible scratch on the coated surface was found to be significantly higher than that of the uncoated substrate. The scratch morphology of the coatings was also studied, which revealed that the scratch-induced damage was mainly due to the plastic deformation of the coating material. The results suggest that the HVOF coated novel hybrid nano composites have great potential in improving the surface properties of various engineering materials and can be used in applications where high wear resistance is required. Overall, the study demonstrates that the combination of HVOF coating technology and hybrid nano-composites can result in coatings with improved microstructure, surface morphology, and scratch resistance, which makes them ideal for use in applications wherever wear resistance is critical.

Application of Pomegranate Rind Extract for Improvement of Functional Properties of Various Materials—A Critical Review

Application of Pomegranate Rind Extract for Improvement of Functional Properties of Various Materials—A Critical Review

Molecular and material property variations during the ideal degradation and mechanical recycling of PET

To verify if PET mechanical recycling is feasible, we need to acknowledge chemical and material property variations. This review highlights the relevance of the connectivity of these variations as a function of the number of recycling cycles.

Investigação de um sistema alternativo para o monitoramento de deformações em estruturas de concreto armado

Abstract In civil engineering, variations in material properties together with the application of different construction techniques and environmental conditions may not be fully considered in structural designs, which could lead to structural damages. Structural Health Monitoring (SHM) makes it possible to follow the behavior of a structure, allowing the evaluation of its conditions and the investigation of its damages and need for interventions. However, SHM is not commonly applied yet due to its high instrumentation cost and the complexity of its procedures. Therefore, the present work aims the development of a low-cost strain measurement system for reinforced concrete structures composed of strain gages, amplifiers, signal converters, and microprocessors. Thus, an easy-to-use and low-cost data system composed of an AD620 amplifier module and an ADS1115 converter was built. Additionally, to facilitate field instrumentations, a steel plate with strain gages arranged in a full Wheatstone bridge was also built. The evaluation of the system was conducted by lab testing a column, four-point bending tests of four beams, and the field monitoring of two columns in a residential building during construction. The results showed that the proposed system performed satisfactorily, being able to accurately measure the strains in reinforced concrete structures.

Study on material-data-driven process parameterization in fine blanking

In industrial sheet-metal processing, processes are parameterized based on the material specifications. However, the manufacturing process of sheet-metal coils determines the material properties and as every manufacturing process is subject to variations, variations in material properties occur in the semi-finished product influencing the subsequent sheet-metal processing. The production of high-quality parts requires considering these varying material properties to adapt the processes accordingly. This paper shows that material data from non-destructive eddy current measurements and process data of the coil production enable decision support for the parameterization of fine blanking processes. A material-data-driven approach using material data recorded in an industrial setting is employed to investigate the influence of parameter settings in the fine blanking process on specific quality characteristics of fine blanked workpieces.

Novel Reliability Evaluation of Existing Structures Using Digital Image Processing and Random Finite Element Simulation

Reinforced concrete (RC) structures are susceptible to deterioration as a result of concrete cracking and steel corrosion. Evaluations of current RC structures are undertaken to ascertain adherence to building codes, the necessity for enhancements, or to rectify structural inadequacies. Reliability techniques are utilized to quantitatively assess the structural integrity of existing RC structures, taking into account the inherent uncertainties related to the applied loads and the resistance of the structure. The main difficulty in evaluating the safety of current RC structures, namely in determining the reliability index, is to formulate accurate resistance models. This problem is particularly pronounced when observable indications of structural deterioration, such as cracking and steel corrosion, are evident. The primary aim of this research is to implement a new computational framework for evaluating the structural integrity of RC elements. This framework utilizes digital image processing (DIP) techniques in conjunction with random finite element (RFE) simulation. In this approach, actual images of the structure under investigation are employed to construct finite element (FE) models, while random fields are utilized to represent the spatial variability in material properties. The recommended framework is proven to enhance the accuracy of the reliability estimate by mitigating the uncertainty associated with the concrete crack pattern and minimizing the uncertainty related to the corrosion process in steel.

The Effect of Earthquake Motion on Rockfall with Material Property Variation

The Effect of Earthquake Motion on Rockfall with Material Property Variation

Fibrotaxis: gradient-free, spontaneous and controllable droplet motion on soft solids

Most passive droplet transport strategies rely on spatial variations of material properties to drive droplet motion, leading to gradient-based mechanisms with intrinsic length scales that limit the droplet velocity or...

An open-source moose implementation of phase-field modeling of fracture in functionally graded materials

Fracture analysis of functionally graded plates is a challenging problem in materials engineering due to the complex material behavior and the presence of cracks. In this study, we propose an efficient open-source MOOSE implementation of phase field fracture analysis of functionally graded. Automatically oriented exponential finite elements are used to discretize the model, which allows for efficient and accurate computation of the fracture behavior. The functionally graded material properties are modeled using a power law function, which captures the variation of material properties along the thickness direction of the plate. The phase field model is coupled with a finite element solver to simulate the mechanical response of the plate under loading. The proposed implementation is validated using several benchmark problems available in literature. The results show that the proposed MOOSE implementation provides accurate predictions of the crack propagation and fracture behavior of functionally graded plates.

Elasticity tunes mechanical stress localization around active topological defects.

Mechanical stresses are increasingly found to be associated with various biological functionalities. At the same time, topological defects are being identified across a diverse range of biological systems and are points of localized mechanical stress. It is therefore important to ask how mechanical stress localization around topological defects is controlled. Here, we use continuum simulations of nonequilibrium, fluctuating and active nematics to explore the patterns of stress localization, as well as their extent and intensity around topological defects. We find that by increasing the orientational elasticity of the material, the isotropic stress pattern around topological defects is changed substantially, from a stress dipole characterized by symmetric compression-tension regions around the core of the defect, to a localized stress monopole at the defect position. Moreover, we show that elastic anisotropy alters the extent and intensity of the stresses, and can result in the dominance of tension or compression around defects. Finally, including both nonequilibrium fluctuations and active stress generation, we find that the elastic constant tunes the relative effect of each, leading to the flipping of tension and compression regions around topological defects. This flipping of the tension-compression regions only by changing the elastic constant presents an interesting, simple, way of switching the dynamic behavior in active matter by changing a passive material property. We expect these findings to motivate further exploration tuning stresses in active biological materials by varying material properties of the constituent units.

Ratio Variation of Maltodextrin and Gum Arabic as Encapsulant on White Jack Bean Tempe Protein Concentrate

The physical and chemical properties of encapsulated substance is directly influenced by the choice of the encapsulant. Different ratios of maltodextrin (MD) and Gum Arabic (GA) produce varying material properties. Therefore, this study aimed to obtain the optimal encapsulant ratio for white jack bean tempe protein concentrate based on physical and chemical characteristics. To achieve this, a descriptive method was employed along with One-Way ANOVA. The results showed that varying encapsulant ratio led to distinct protein content, moisture content, encapsulation efficiency, and yield. The treatment with maltodextrin and Gum Arabic ratio of 20:80 showed the highest effectiveness, with protein content, moisture content, encapsulation efficiency, and yield at 26.10 ± 0.45%, 7.93 ± 0.42%, 95.84 ± 0.71%, and 14.27%, respectively.

Determination of dynamic parameters of free vibrating materials (Nizhny Novgorod)

The most commonly used methods for determination of dynamic properties are expensive and difficult to reproduce without specialised equipment. There is a need to develop simplified techniques that allow to determine specific material properties, avoiding the use of complex laboratory tests.Purpose: The aim of this work is to develop and test a simplified methodology for determining dynamic properties of various materials using pine wood as an example.Methodology: Experimental modelling using up-to-date measuring devices and analytical processing of the obtained results.Research findings: The dynamic modulus of elasticity of pine wood is determined with high accuracy and coincides with reference values. The coefficient of vibration damping is obtained for the calculation of dynamic systems in near-resonance zones.Practical implications: The proposed methodology can be used to determine the dynamic properties of new materials in order to enter these characteristics in software databases and computer complexes.Originality: The proposed method of determining the dynamic parameters of the material is based on the analysis of two-support beam vibrations registered by an accelerometer.

Irradiation-induced age-related degradation mechanisms effect on integrity of baffle former bolts

For long-term operation of nuclear power plants, integrity of structures, systems and components should be ensured rigorously. In particular, since the complicated reactor vessel internals (RVIs) have been exposed to high temperature and neutron irradiation environment, materials reliability programs on the RVIs to resolve anticipated issues were conducted by several research institutes. The objectives of this research are to examine evaluation procedures derived from the previous works and to apply them for RVIs in two operating reactors with baffle former assembly from different electricity powers. Finite element (FE) analyses were performed employing five user-subroutines developed by the authors for reflection of multiple age-related degradation mechanisms (ARDMs) as well as pre- and post-processing. Temperature distributions due to gamma heatings, fuel cycles, typical normal operating temperature and pressure histories were considered with relevantly varying material properties. As results, effects of irradiation were quantified in terms of stresses, strains and irradiation assisted crack sensitivity parameters. Further assessment was carried out through not only investigating contribution of each ARDM but also comparing the present FE analysis results with those obtained from a different reactor type in detail.

Material Characteristics of Lime Plaster in Goguryeo Mural Tombs (I): Focusing on Lime Plaster Excavated from Anak Tomb No.3

Physical and chemical investigations were conducted on lime sample from Anak Tomb No.3 to determine the properties of the plaster material. The morphological and physical characteristics of the specimens were analyzed using both a microscope and a polarizing microscope. The constituent materials were identified through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer, and the qualities of the mixed material were established through thermal analysis. Additionally, micro-computed tomography was used to non-destructively confirm the internal structure and density characteristics. The lime sample was recognized as a lime plaster material with two unique layers. Each layer shows variations in material properties. It is speculated that this lime specimen was used to finish the edges of the authentic wall within Anak Tomb No.3. Through the synthesis of various morphological attributes and physical properties; the whiteness, durability, thinness, and repetition of the layers, as well as smoothness of the lime plaster used for Anak Tomb No. 3 indicate that a high level of lime wall plastering technique was used in Goguryeo Tomb. It was possible to evaluate the refined level of lime wall manufacturing technology in the Goguryeo era.

Exploring the mechanical response of functionally graded hollow disks: insights from rotation, gravity and variable heat generation

PurposeThe purpose of the study is to perform elastic stress and deformation analysis of a functionally graded hollow disk under different conditions (rotation, gravity, internal pressure, temperature with variable heat generation) and their combinations.Design/methodology/approachThe classical method of solution, Navier's equation, is used to solve the governing equation. The analysis considers thermal and mechanical boundary conditions and takes into account the variation of material properties according to a power law function of the radius of the disk and grading parameter.FindingsThe findings of the study reveal distinct trends and behaviors based on different grading parameters. The influence of gravity is found to be negligible, resulting in similar patterns to the pure rotation case. Variable heat generation introduces non-linear temperature profiles and higher displacements, with stress values influenced by grading parameters.Practical implicationsThe study provides valuable insights into the behavior of displacement and stresses in hollow disks, offering a deeper understanding of their mechanical response under varying conditions. These insights can be useful in the design and analysis of functionally graded hollow disks in various engineering applications.Originality/valueThe originality and value of this study lies in the consideration of various loading combinations of rotation, gravity, internal pressure and temperature with variable heat generation. Furthermore, the study of effect of various angular rotations, temperatures and pressures expands the understanding of the mechanical behavior of such structures, contributing to the existing body of knowledge in the field.

Equivalent geometric imperfection for interaction buckling of welded box-section columns - Stochastic analysis

The current paper investigates recently developed GMNIA-based equivalent global and local imperfections to be applicable in the FEM-based design of welded box-section columns. While these imperfections were developed independently for the local and global buckling problems, their applicability to coupled instability problems has not yet been investigated. Therefore, this study addresses this gap by investigating the effectiveness of these imperfections in predicting pure local, global and interaction buckling capacities by comparing them against accurate stochastic analyses using Monte Carlo simulations. The current simulations take into account the variations in geometrical and material properties as well as the imperfections, leading to a highly accurate estimation of the buckling capacity of welded box-section columns. Statistical measures are used to assess the accuracy of each imperfection type and imperfection combination. The discrepancy in deterministic resistance resulting from the application of imperfections and combinations is assessed by comparing them with the accurate buckling resistance. Based on the statistical evaluation, the numerical model uncertainty is also evaluated, serving as the input data of the model factor calculation. The present paper gives a unique introduction to the calculated model factors and presents its calculation methodology for local and global buckling problems.

Moisture Performance Requirements for Insulation in Exterior Wood-Frame Walls without a Vapour Barrier

An increased interest has been observed, especially among architects, in constructing the building envelope without using a vapour barrier membrane of polyethene (PE) foil. An increasing interest in biogenic building materials has also been expressed, as their use, besides storing embedded carbon, can reduce greenhouse gas emissions, replacing nonrenewable building components. Further, building envelope construction without a vapour barrier reduces expenses and the difficulty of the work process, especially around joints and penetrations. This study aims to determine the most important material properties of biogenic thermal insulation materials that influence the moisture-robustness of exterior wood-frame walls constructed without a vapour barrier. A literature study was performed to examine which material parameters have the most influence on the moisture conditions in an exterior wall without a vapour barrier. Hygrothermal simulations of lightweight exterior walls were performed to investigate the significance of variations in material properties (e.g., equilibrium moisture content and vapour diffusion resistance) and determine their necessary characteristics when used as thermal insulation material in an exterior wall without a vapour barrier in internal humidity class 3 (defined in EN ISO 13788). The moisture-robustness of the construction is assessed based on the risk of mould growth in the layer between the thermal insulation and wind barrier. The study suggests that the moisture capacity of the available common biogenic thermal insulation materials does not significantly affect the overall moisture performance of the wall. Simulations demonstrate that, for the thermal insulation layer in internal humidity class 3, at least one of the following requirements must be met to ensure moisture-robustness in exterior walls without a vapour barrier: (I) high diffusion resistance of the thermal insulation and (II) high moisture capacity of the thermal insulation material at relative humidity between 60% and 90%. Commercial biogenic thermal insulation materials on the market do not meet the latter requirement.