Identification Of Material Properties Research Articles

Material Property Identification of Damper Constrained by Thin Foil and Its Application to an Automotive Vehicle

Material Property Identification of Damper Constrained by Thin Foil and Its Application to an Automotive Vehicle

Effects of anti-resorptive treatment on the material properties of individual canine trabeculae in cyclic tensile tests.

Osteoporosis is defined as a decrease of bone mass and strength, as well as an increase in fracture risk. It is conventionally treated with antiresorptive drugs, such as bisphosphonates (BPs) and selective estrogen receptor modulators (SERMs). Although both drug types successfully decrease the risk of bone fractures, their effect on bone mass and strength is different. For instance, BP treatment causes an increase of bone mass, stiffness and strength of whole bones, whereas SERM treatment causes only small (4%) increases of bone mass, but increased bone toughness. Such improved mechanical behavior of whole bones can be potentially related to the bone mass, bone structure or material changes. While bone mass and architecture have already been investigated previously, little is known about the mechanical behavior at the tissue/material level, especially of trabecular bone. As such, the goal of the work presented here was to fill this gap by performing cyclic tensile tests in a wet, close to physiologic environment of individual trabeculae retrieved from the vertebrae of beagle dogs treated with alendronate (a BP), raloxifene (a SERM) or without treatments. Identification of material properties was performed with a previously developed rheological model and of mechanical properties via fitting of envelope curves. Additionally, tissue mineral density (TMD) and microdamage formation were analyzed. Alendronate treatment resulted in a higher trabecular tissue stiffness and strength, associated with higher levels of TMD. In contrast, raloxifene treatment caused a higher trabecular toughness, pre-dominantly in the post-yield region. Microdamage formation during testing was not affected by either anti-resorptive treatment regimens. These findings highlight that the improved mechanical behavior of whole bones after anti-resorptive treatment is at least partly caused by improved material properties, with different mechanisms for alendronate and raloxifene. This study further shows the power of performing a mechanical characterization of trabecular bone at the level of individual trabeculae for better understanding of clinically relevant mechanical behavior of bone.

Degradation of elastic characteristics of the CFRP used in the design of a gas turbine engine as a result of high-cycle fatigue damage

Carbon fiber reinforced polymers (CFRP) are increasingly being used in heavily loaded parts of aircraft engines. CFRP fan blades, vanes must successfully resist fracture due to high-cycle fatigue. One of the consequences of fatigue damage is a decrease in the rigidity of the material and a drop in the natural vibration frequencies of parts. These effects are of interest when developing fatigue fracture models and predicting durability. The purpose of this article is to develop a method and obtain experimental data on the decrease of elastic characteristics of CFRP as a result of progressive fatigue damage. The developed technique consists of two stages. During the first one, the natural frequencies and eigenmodes of the samples during their fatigue testing are experimentally obtained. During the second stage, the four elasticity parameters of the CFRP laminate monolayer are identified via the natural frequencies. The inverse numerical/experimental technique for material properties identification is applied. The dependences of elastic characteristics on the relative fatigue life are obtained as experimental results of both modal and fatigue tests. The results can be useful in studying the fatigue behavior of the examined materials and in creating methods for calculating fatigue life.

Change of the Elastic Characteristics of a Fiber-Reinforced Laminate as a Result of Progressive Fatigue Damage

It is a widely known fact that the stiffness of polymer composite materials decreases with the accumulation of fatigue damage under cyclic loading. The purpose of this article is to develop a method and obtain experimental data on decrease of the elastic characteristics of a fiber-reinforced laminate, as a result of progressive fatigue damage. The developed technique consists of two stages. At the first one, the natural frequencies and eigenmodes of the samples during their fatigue testing are experimentally obtained. The dependences of the natural frequencies of the samples on the number of loading cycles are found. At the second stage, the four elasticity parameters of the laminate monolayer (two Young modules, the shear module and Poisson's ratio) are identified via the natural frequencies. The inverse numerical/experimental technique for material properties identification is applied. The dependences of the natural frequencies and mentioned elastic characteristics on the relative fatigue life are obtained as experimental results of both modal and fatigue tests. The results can be useful to study the fatigue behavior of the investigated materials and to create methods for calculating fatigue life.

Identification of Material Properties and Optimal Design of Magnetically Shielded Rooms

In this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor.

Fiber splay precludes the direct identification of ligament material properties: Implications for ACL graft selection

Anterior cruciate ligament (ACL) injuries typically require surgical reconstruction to restore adequate knee stability. The middle third of an injured patient’s patellar tendon (PT) is a commonly used graft for ACL reconstruction. However, many clinicians and researchers question whether it is the best option, as several studies have suggested that it is a stiffer material than the ACL. Still, there is little to no consensus on even the most basic material property of ligaments/tendons: the tangent modulus in the fiber direction, or slope of the linear portion of the uniaxial stress–strain curve. In this study, we investigate the effect of fiber splay (the tendency of collagen fibers to spread out near the enthesis) on the apparent tangent modulus. Using a simplified theoretical model, we establish a quantity we call the splay ratio, which describes the relationship between splay geometry and the apparent tangent modulus. We then more rigorously investigate the effect of the splay ratio on the apparent tangent modulus of the ovine PT and anteromedial and posterolateral regions of the ACL using experimental and computational methods. Both approaches confirmed that splay geometry significantly affects the apparent material behavior. Because true material properties are independent of geometry, we conclude that the macroscopic response of ligaments and tendons is not sufficient for the characterization of their material properties, but rather is reflective of both material and structural properties. We further conclude that the PT is probably not a stiffer material than ACL, but that the PT graft is likely a stiffer structure than either ACL region.

Model-based bone material property identification

Abstract Correct torqueing of bone screws is important for orthopaedic surgery. Surgeons mainly tighten screws ad hoc, risking inappropriate torqueing. An adaptive torque-limiting screwdriver may be able to measure the torque-rotation response and use parameter identification of key material properties to recommend optimal torques. This paper analyses the identifiability and sensitivity of a model of the bone screwing process. The accuracy with which values of the Young modulus (E) of the bone were identified depended on the value of E, with larger values being less accurately identified. The error in identified σ u t s {\sigma _{uts}} (Tensile strength) values was less than 0.5 % over all the cases tested, with no discernible dependence on the co-identified values of E. Experimental validation is still required for the model and identification process, but this approach is feasible and promising from a theoretical perspective.

Investigation of the 2D assumption in the image‐based inertial impact test

AbstractThe image‐based inertial impact (IBII) test has shown promise for measuring properties of composites at strain rates where existing test methods become unreliable due to inertial effects (> 102 s−1). Typically, the IBII tests are performed with a single camera, and therefore, to use surface measurements for material property identification, it is necessary to assume that the test is two‐dimensional. In this work, synchronised ultra‐high‐speed cameras are used to quantify the relevance of this assumption when nonuniform, through‐the‐thickness loading is applied to interlaminar samples. Initial experiments revealed that an angular misalignment of approximately 1° between the impact faces of the waveguide and projectile created a bending wave that propagated along the sample behind the axial pulse. Even under these conditions, consistent measurements of stiffness were made by assuming a linear distribution of the behaviour through‐the‐thickness. When the misalignment was reduced to 0.2°, the effects on single‐sided measurements were significantly reduced. The two alignment cases were compared to show that three‐dimensional loading had a small effect on stiffness identification (approximately 5% bias) relative to failure stress (approximately 30% bias). This study highlights the importance of impact alignment for reliable characterisation of the interlaminar failure stress and was used to establish guidelines for diagnosing loading issues from single‐sided measurements.

Experimental & Computational Fluid Dynamics Study of the Suitability of Different Solid Feed Pellets for Aquaculture Systems

Fish feed delivery is one of the challenges which fish farmers encounter daily. The main aim of the feeding process is to ensure that every fish is provided with sufficient feed to maintain desired growth rates. The properties of fish feed pellet, such as water stability, degree of swelling or floating time, are critical traits impacting feed delivery. Some considerable effort is currently being made with regard to the replacement of fish meal and fish oil with other sustainable alternative raw materials (i.e., plant or insect-based) with different properties. The main aim of this study is to investigate the motion and residence time distribution (RTD) of two types of solid feed pellets with different properties in a cylindrical fish tank. After experimental identification of material and geometrical properties of both types of pellets, a detailed 3D computational fluid dynamics (CFD) study for each type of pellets is performed. The mean residence time of pellets injected at the surface of the fish tank can differ by up to 75% depending on the position of the injection. The smallest residence time is when the position is located at the center of the liquid surface (17 s); the largest is near the edge of the tank (75 s). The maximum difference between the two studied types of pellets is 25% and it increases with positions closer to the center of the tank. The maximum difference for positions along the perimeter at 3/4 tank radius is 8%; the largest residence times are observed at the opposite side of the water inlet. Based on this study, we argue that the suitability of different solid feed pellets for aquaculture systems with specific fish can be determined, and eventually the pellet composition (formula) as well as the injection position can be optimized.

A Nonlinear Hanning-Windowed Chirplet Model for Ultrasonic Guided Waves Signal Parameter Representation

Parametric signal representation techniques with Chirplet models have attracted much attention in ultrasonic guided waves-based research of material property identification and structural integrity evaluation. The known Chirplet models are established using either the Gaussian windows or the linear chirp function. This is inconsistent with practical situations where the excitation is a Hanning-windowed sinusoidal signal, and the received signals have a nonlinear phase and asymmetric envelope due to the dispersive nature of the waves. A nonlinear Hanning-windowed Chirplet (NHWC) model was proposed to eliminate the above inconsistencies in which a nonlinear phase modulation term was designed to modulate the classical Hanning-window and the sine function. The phase modulation term was established with the hyperbolic tangent function. The mathematical properties of the nonlinear phase modulation term and the NHWC model were analyzed mathematically, including the time variability, parity, concavity, and convexity of the phase. These were used to guide the parameter setting in parametric signal representation techniques. The NHWC model can characterize various characteristics of guided waves signals, including the symmetric or asymmetric Hanning envelopes and the phase nonlinearity. Finally, an adaptive genetic algorithm was adopted to verify the effectiveness of the NHWC model in the parameter representation of experimentally measured ultrasonic signals.

An inverse meshfree thermoelastic analysis for identification of temperature-dependent thermal and mechanical material properties

In many practical problems, a body is subjected to a thermal load and experience a temperature change. In some cases, the temperature change can be very high and it would be better to consider thermal and mechanical properties as a function of temperature whereas in many cases, temperature-dependent thermal and mechanical properties are unknown. In this article, an inverse method is presented for identification of the thermal conductivity, the specific heat, the coefficient of thermal expansion, and the elastic modulus, where all the properties are considered as functions of temperature. It is assumed that these four material properties are simultaneously unknown. In the proposed method, the unknown parameters of the inverse problem are calculated using measured data from a transient thermomechanical experiment. Sensitivity analysis is carried out by an analytical direct differentiation method and a meshfree technique. Several important factors affecting the identification of the thermal and mechanical properties, such as the error of measuring sensors, the number of sensors, and the number of sampling data are studied in the numerical analyses. The obtained results show that identification of the properties using the proposed inverse method can be achieved with a suitable accuracy even in the cases with measurement errors.

A novel methodology for estimating tensile properties in a small punch test employing in-situ DIC based deflection mapping

Determining tensile properties from small punch test is being pursued actively in the nuclear industry due to the limited volume of material such tests use compared with standard tests which can be critical when considering active or development samples. One of the crucial challenges in harnessing the full potential of this technique is formulating methodologies which correlate the small punch specimen’s deflection to equivalent uniaxial tensile properties. Existing approaches for correlation rely on deflection obtained from a single point on the small punch test specimen, used with empirical equations to make the correlation. However, the deflection and strain accumulation in a small punch specimen is highly heterogeneous and data from a single point does not represent the gross deformation evolving in the specimen. This data when used in conjunction with the empirical formulations for deriving equivalent uniaxial tensile properties, would not result in accurate identification of material properties. In this work we offer an alternative approach which uses the full field deflection of the specimen mapped through in-situ digital image correlation. The use of digital image correlation combined with inverse finite element analysis augments the existing method of material properties identification from single point deflection data thereby significantly improving the reliability of the measurements.

Electro-Thermal Modelling and Experimental Verification of Power Semiconductor Diode

The aim of the proposed paper is discussing problematics related to the thermal modelling of power electronic components. More in detail, the electro-thermal relationship is investigated for the selected power diode, while analysis shall serve for system optimization considering thermal performance with the use of highly accurate 3D simulation model. The presented approach describes the procedure of the simulation model development, whereby the main part is discussing necessities relevant for material property identification through the indirect procedure, i.e, material properties are not known from the manufacturer. Electro-thermal dependencies are defined within the proposed model, while this model enables parametric changes of the geometrical properties of the device. Added value of this procedure is the possibility of its use in exact determination of the lifetime of a semiconductor component using mathematical models taking into account operational variables (current, voltage, temperature, etc.). The proposed model is verified and validated through thermovision experimental measurements within defined operational conditions.

Combining Freehand Ultrasound-Based Indentation and Inverse Finite Element Modeling for the Identification of Hyperelastic Material Properties of Thigh Soft Tissues.

Finite element analysis (FEA) is a numerical modeling tool vastly employed in research facilities to analyze and predict load transmission between the human body and a medical device, such as a prosthesis or an exoskeleton. Yet, the use of finite element modeling (FEM) in a framework compatible with clinical constraints is hindered by, among others, heavy and time-consuming assessments of material properties. Ultrasound (U.S.) imaging opens new and unique opportunities for the assessment of in vivo material properties of soft tissues. Confident of these advances, a method combining a freehand U.S. probe and a force sensor was developed in order to compute the hyperelastic constitutive parameters of the soft tissues of the thigh in both relaxed (R) and contracted (C) muscles' configurations. Seven asymptomatic subjects were included for the experiment. Two operators in each configuration performed the acquisitions. Inverse FEM allowed for the optimization of an Ogden's hyperelastic constitutive model of soft tissues of the thigh in large displacement. The mean shear modulus identified for configurations R and C was, respectively, 3.2 ± 1.3 kPa and 13.7 ± 6.5 kPa. The mean alpha parameter identified for configurations R and C was, respectively, 10 ± 1 and 9 ± 4. An analysis of variance showed that the configuration had an effect on constitutive parameters but not on the operator.

Prediction of Nanoscale Friction for Two-Dimensional Materials Using a Machine Learning Approach

Several two-dimensional (2D) materials such as graphene, molybdenum disulfide, or boron nitride are emerging as alternatives for lubrication additives to control friction and wear at the interface. On the other hand, the initiative to accelerate materials discovery through data-driven computational methods has identified numerous novel topologies and families of 2D materials that can potentially be designed as low-friction additives. Hence, generating a structure–property (friction) correlations for 2D material-based additives that present a large variation in atomic composition is the next big challenge. Herein, we present a machine learning (ML) method using the Bayesian modeling and transfer learning approach to predict the maximum energy barrier (MEB) of the potential surface energy (correlated to intrinsic friction) of ten different 2D materials that were previously unexplored for their tribological properties. The descriptors (or properties) required to train the ML model with high accuracy are identified by taking into account the established physical models for dissipation in 2D materials. As a result, a difference of less than 8% in MEB values as predicted via the ML model presented here and the PES profiles generated using molecular dynamics simulations, for a select few 2D materials, was obtained. The model also enabled the identification of material properties that present the highest sensitivity to the corrugated potential, hence enabling the development of design routes for the synthesis of 2D materials with optimal tribological properties.

Prediction of Load-Bearing Capacity of Composite Parts with Low-Velocity Impact Damage: Identification of Intra- and Inter-Ply Constitutive Models

Assessments of residual load-carrying capacity are often conducted for composite structural components that have received impact damage. The availability of a verified simulation methodology can provide significant cost savings when such assessments are required. To support the development of a reliable and accurate simulation methodology, this study investigated the predictive capabilities of a stacked solid-shell finite element model of a cylindrical composite component with a damage mechanics-based description of the intra-ply material response and a cohesive contact model used for simulation of the inter-ply behavior. Identification of material properties for the model was conducted through mechanical characterization. Special attention was paid to understanding the influence of non-physical parameters of the intra- and inter-ply material models on predicting compressive failure load of damaged composite cylinders. Calibration of the model conducted using the response surface methodology allowed for identifying rational values of the non-physical parameters. The results of simulations with the identified and calibrated finite element model showed reasonable correlation with experimental data in terms of the predicted failure loads and post-impact and post-failure damage modes. The investigated modeling technique can be recommended for evaluating the residual load-bearing capacity of flat and curved composite parts with impact damage working under the action of compressive loads.

Inverse identification of cell-wall material properties of closed-cell aluminum foams based upon Vickers nano-indentation tests

This study aims to develop an inverse approach to identifying the cell-wall material properties of closed-cell aluminum (Al) foams, which is based upon indentation tests, numerical simulation and optimization technique. Vickers nano-indentation tests are conducted on the cell-wall of foams, and the residual surface deformation is measured by a high definition confocal microscopy. To enhance identification efficiency, a combined 2D with 3D micromechanics modeling strategy is proposed here, in which the load-depth curve and residual imprint (pile-up) of the indentation tests are considered. In this study, the cell-wall material properties such as the yield strength and strain-hardening exponent are identified using this proposed inverse approach, while the Young's modulus is obtained directly for the unloading part of the indentation load-depth curves. The identification results indicate that the proposed inverse procedure can provide a well-posed solution to the cell-wall material properties by introducing the pile-up information. Microscopic computed tomography (μCT) technique is also utilized to reconstruct accurate 3D image-based representative volume element (RVE) model of foam structure, through which the numerical simulation is conducted for uniaxial compression. The identified cell-wall material parameters are validated by comparing the numerical simulation with the experimental data in terms of the deformation/failure modes and quantitative results. It is noted that the cell-wall of aluminum foams that are commonly made of melt foaming processes exhibits a quite different stress-strain relation when compared with the raw material of cell-wall. This study is expected to provide an effective approach for identifying the material properties that may be not easily determined through conventional testing methods.

Assessment of the Impact Resistance of a Composite Material with EN AW-7075 Matrix Reinforced with α-Al2O3 Particles Using a 7.62 × 39 mm Projectile.

The paper presents the results of studies on the effects of shooting composite materials produced by pressure infiltration with the EN AW-7075 alloy as a matrix and reinforcement in the form of preforms made of α-Al2O3 particles. Composite materials were made with two reinforcement contents (i.e., 30% and 40% vol. of α-Al2O3 particles). The composites produced in the form of 12 mm thick plates were subjected to impact loads from a 7.62 × 39 FMJ M43 projectile fired from a Kalashnikov. The samples of composites with different contents of strengthening particles were subjected to detailed microscopic examination to determine the mechanism of destruction. The effect of a projectile impact on the microstructure of the material within the perforation holes was identified. There were radial cracks found around the puncture holes and brittle fragmentation of the front surfaces of the specimens. The change in the volume of the reinforcement significantly affected the inlet, puncture and outlet diameters. The observations confirmed that brittle cracking dominated the destruction mechanism and the crack propagation front ran mainly in the matrix material and along the boundaries of the α-Al2O3 particles. In turn, numerical tests were conducted to describe the physical phenomena occurring due to the erosion of a projectile hitting a composite casing. They were performed with the use of the ABAQUS program. Based on constitutive models, the material constants developed from the identification of material properties were modelled and the finite element was generated from homogenization in the form of a representative volume element (RVE). The results of microscopic investigations of the destruction mechanism and numerical investigations were combined. The conducted tests and analyses shed light on the application possibilities of aluminium composites reinforced with Al2O3 particles in the construction of add-on-armour protective structures.

Characterization and Uncertainty Analysis of the Interlaminar Inelastic Properties of Unidirectional Fibre-reinforced Composites

The compression failure mode has been achieved through changing the SBS (Short Beam Shear) experiment parameters, and the nonlinear constitutive relationship along thickness direction for the typical specimens loaded in 1-3 principal material plane has been computed iterative by FEMU with the reconstruction strain field and the numerical simulated stress data of FEM model. The uncertainly of the constitutive parameters is induced by the measurement system noise in the DIC technique and the approximation error in the displacements and strains smoothing algorithm. The covariance matrix of the extracted material constitutive parameters has been given explicitly. Three material constitutive parameters were identified from a customized short-shear experiment simultaneously using an estimated optimal reconstruction mesh size as an illustration. Sensitivity of measurement noise and reconstruction parameter on extracted material properties has been investigated. The effects of region of interest (ROI) and DIC image number on uncertainties of extracted material properties have been addressed. It is suggested that there exist an appropriate ROI and the number of images, from which reliable material parameters can be identified, but much more data used in identification process always lead to smaller standard deviation and COV. It is observed that the material constants used to characterize the interlaminar stress-strain behavior show strong robustness to the measurement noise. Another key finding is that the reconstruction parameter in the global finite-element based approximation approach is critical for reliable material properties identification. Its value has to stay close to optimum for guaranteeing reliable identification of material properties.

A Computational Systems Approach to Rational Design of Nose-to-Brain Delivery of Biopharmaceutics

In this work, a computational systems approach, comprising models at different time and length scales, is developed to elucidate the fundamental chemical, physical, transport, and biological processes in relation to the design of a novel nose-to-brain drug delivery system for the treatment of neurodegenerative diseases. In particular, a kinetic model is established to describe the formation of a hydrogel patch, via the enzymatic cross-linking of tyramine-modified hyaluronic acid, on the olfactory cleft. A fluid transport model is employed to describe the flow of a cross-linkable viscoelastic polymer solution through an applicator in terms of tube and reactive fluid characteristics (e.g., tube geometry, volumetric flow rate, and viscosity). The spreading of the deposited HA droplet on a mucus substrate is modeled via the development of a dynamic droplet deformation model. Subsequently, a dynamic drug release model is formulated to quantify the release rate of an active pharmaceutical ingredient (e.g., long-acting insulin analogues) from a distributed population of drug-loaded polymeric carriers embedded into a hydrogel matrix in terms of molecular and morphological properties of the hydrogel–drug carriers system. Finally, the drug flux from the hydrogel–mucosa interface to the olfactory bulb via the epithelium and lamina propria olfactory sublayers is modeled with a series of dynamic mass transport models. The various mathematical models are integrated together following a multiscale modeling approach to aid the identification of key design system parameters and material properties that can lead to the optimization of the complex drug carriers–hydrogel, droplet deposition, film formation, and drug delivery system to achieve a desired therapeutic effect over a two-week delivery time.