Changes In Material Parameters Research Articles

Analysis of compact tension specimens with deflected cracks for orthotropic materials

Anisotropic materials, such as alloy, wood and fiber-reinforced composites, are widely used in load-bearing components. Accurately obtaining its fracture performance is crucial for safety assessment. However, existing testing methods based on compact tension (CT) specimen have not taken into account material anisotropic characteristics and crack deflection. In this work, the systematic finite element analysis (FEA) was conducted for CT specimens with deflected cracks made of orthotropic materials. A wide range of geometric (crack deflection angle, β, and ratio of crack length to width, ap/W) and orthotropic material (λ and ρ) parameters were discussed. Complete solutions of the stress intensity factor (KI and KII) and load-line compliance (C) were determined for the first time. The results showed that the geometric dimensions and material parameters have a significant coupling influence on the fracture parameters. The influence of the λ is generally greater than that of the ρ. Changes of material parameters can make fracture parameters’ dependence on β vary. The variation of β and ap/W could enlarge or minish even dismiss the impact of λ and ρ. In addition, to further verify the importance of the obtained fracture parameters, the CT fracture tests of carbon fiber-reinforced epoxy resin under various orientations were conducted. The solutions will promote the optimization of the fracture toughness testing standards for CT specimens made of anisotropy materials.

Improving the efficiency and stability of betavoltaic batteries based on understanding efficiency fluctuations and gaps with theoretical limits

Wide-bandgap semiconductors are regarded as preferred materials for preparing semiconductor conversion devices in betavoltaic batteries due to their high theoretical conversion efficiency (ηc). However, there are a few comprehensive analytical studies on why the experimental values of ηc are generally much lower than the theoretical limit of ηc (ηc-limit) and how to improve ηc and its stability. In this work, combined with the energy deposition distributions of Ti3H2, 63Ni, and 147Pm2O3 radioactive sources in SiC obtained from Monte Carlo simulations, a multi-physical mechanism, multi-parameter coupling numerical model was established. This model can comprehensively analyze the output characteristics of betavoltaic batteries under the influence of actual device structural and material parameter changes. Our results show that changes in structural and material parameters cause significant variations in the collection efficiency (Q) of the radiation-generated electron–hole pair (RG-EHP). Considering structural parameters are easy to control, instabilities in actual SiC material parameters, which include electron diffusion length (Ln), hole diffusion length (Lp), and surface recombination velocity (S), are the main reason that ηc fluctuates significantly and is generally far lower than ηc-limit. Due to differences in the distribution of RG-EHP produced by different radioactive sources in SiC, the dominant parameters causing ηc fluctuations differ. By analyzing differences in recombination loss mechanisms under different radioactive sources, the device structures were designed in a targeted manner to make ηc closer to ηc-limit. Meanwhile, when the SiC material quality fluctuates, the stability of ηc increases by 58.5%, 35.3%, and 48.2% under Ti3H2, 63Ni, and 147Pm2O3, respectively.

Sensitivity analysis of fibrous thick-walled tubes with mechano-sensitive remodeling fibers in homeostasis

In this article, we apply the sensitivity analysis method to capture the influence of various parameters on the inflation pressure, axial force, and the deformation for an inflated and axially stretched cylinder. The material consists of an isotropic ground substance material reinforced with fibers that undergo a continuous and mechano-sensitive remodeling process. The input parameters of the mechanical system are assumed to be distributed according to the uniform probability distribution function. In the sensitivity analysis, we apply the Sobol method to determine how the variations of input parameters affect the inflation as well as the axial force in the cylinder. Special attention is given to the fiber remodeling process associated with a homeostatic balance between the constant fiber creation process and the strain-stabilized fiber dissolution. The results may help to understand the importance of the effect of material parameter changes, for example, due to remodeling processes in the context of diseases or recovering processes, on the overall tissue behavior.

Chirality, anisotropic viscosity and elastic anisotropy in three-dimensional active nematic turbulence

Various active materials exhibit strong spatio-temporal variability of their orientational order known as active turbulence, characterised by irregular and chaotic motion of topological defects, including colloidal suspensions, biofilaments, and bacterial colonies.In particular in three dimensions, it has not yet been explored how active turbulence responds to changes in material parameters and chirality.Here, we present a numerical study of three-dimensional (3D) active nematic turbulence, examining the influence of main material constants: (i) the flow-alignment viscosity, (ii) the magnitude and anisotropy of elastic deformation modes (elastic constants), and (iii) the chirality. Specifically, this main parameter space covers contractile or extensile, flow-aligning or flow tumbling, chiral or achiral elastically anisotropic active nematic fluids. The results are presented using time- and space-averaged fields of defect density and mean square velocity. The results also discuss defect density and mean square velocity as possible effective order parameters in chiral active nematics, distinguishing two chiral nematic states—active nematic blue phase and chiral active turbulence. This research contributes to the understanding of active turbulence, providing a numerical main phase space parameter sweep to help guide future experimental design and use of active materials.

Frictional Slip and Incremental Dynamic Analysis of Plate-rubber Bearing Continuous Girder Bridge by Ambient Temperature in Cold Region

Special mechanical environment, the environmental temperature or stress transformation easily to the final mechanical properties of the bridge components performance changes. The impact of the cold zone environment on the plate rubber-bearing beams is the object of study, Jining Road refined mechanics finite element analysis of the structural dynamic response study under seismic action. The results show that low temperature leads to bearing friction slip and material parameter changes, which affects the self-oscillation frequency and seismic susceptibility of the bridge. Due to the temperature-induced changes in the material properties and mechanical properties of the bearings, the first principal period of the bridge increases by 3% at high temperature for the EH and decreases by 19% at low temperature for the EL when compared to the first principal period under normal temperature conditions. Under different extreme temperature conditions, the fundamental period of the bridge is longitudinal, and the effective mode vibration participation mass is more than 90%. The maximum crossover frequency VALmax reaches 75.6 dB. Compared with room temperature, the bearing stress increased by 27.6% to 45.5%. The effect of EL stress change should be considered in the design of bridges in the alpine region.

Connecting material degradation and power loss of PV modules using advanced statistical methodology

The presented work focuses on the influence of different stress combinations (in climate-specific ageing tests) on polymer material degradation and electrical power loss of PV modules and how these data can be linked using advanced statistical methods. The statistical analysis is divided into three parts: in the first part, the direct effects of the climatic stresses on the electrical performance are assessed. The second part aims to correlate the electrical degradation behaviour with changes in the encapsulation material, and the third part does the same for the backsheet material of the modules.Time series of electrical data are extracted from IV curves and correlated with changes in material parameters obtained from fluorescence spectroscopy of the encapsulant as well as infrared spectroscopy and colour measurements of the backsheet. The data set analyzed consists of measurements that were taken throughout accelerated ageing experiments simulating stressors typically found for arid, tropical, moderate, and alpine climate zones. Significant correlations were found between the material changes - as indicated by the spectral measurements - and the electrical power loss of the test modules in the course of climate-specific ageing.The results of the analysis provide valuable input for possible measures of preventive maintenance based on condition monitoring of single modules. The methodology developed in this paper allows for an estimation of the power output for modules with identical design and bill of materials using simple, non-destructive measurement methods. The results from accelerated lab tests and the correlations determined from them can be used to predict the electrical power output of installed PV modules. As a result, deviations in module performance can be detected at an early stage and preventive maintenance measures in PV systems can be carried out.

Detection of electromagnetic phase transitions using a helical cavity susceptometer.

Fast and sensitive phase transition detection is one of the most important requirements for new material synthesis and characterization. For solid-state samples, microwave absorption techniques can be employed for detecting phase transitions because it simultaneously monitors changes in electronic and magnetic properties. However, microwave absorption techniques require expensive high-frequency microwave equipment and bulky hollow cavities. Due to size limitations in conventional instruments, it is challenging to implement these cavities inside a laboratory cryostat. In this work, we designed and built a susceptometer that consists of a small helical cavity embedded into a custom insert of a commercial cryostat. This cavity resonator operated at sub-GHz frequencies is extremely sensitive to changes in material parameters, such as electrical conductivity, magnetization, and electric and magnetic susceptibilities. To demonstrate its operation, we detected superconducting phase transition in Nb and YBa2Cu3O7-δ, metal-insulator transitions in V2O3, ferromagnetic transition in Gd, and magnetic field induced transformation in meta magnetic NiCoMnIn single crystals. This high sensitivity apparatus allows the detection of trace amounts of materials (10-9-cc) undergoing an electromagnetic transition in a very broad temperature (2-400K) and magnetic field (up to 90 kOe) ranges.

Resonant radiation emitted by solitary waves via cascading in quadratic media.

We present a systematic investigation of the resonant radiation emitted by localized soliton-like wave-packets supported by second-harmonic generation in the cascading regime. We emphasize a general mechanism which allows for the resonant radiation to grow without the need for higher-order dispersion, primarily driven by the second-harmonic component, while radiation is also shed around the fundamental-frequency component through parametric down-conversion processes. The ubiquity of such a mechanism is revealed with reference to different localized waves such as bright solitons (both fundamental and second-order), Akhmediev breathers, and dark solitons. A simple phase matching condition is put forward to account for the frequencies radiated around such solitons, which agrees well with numerical simulations performed against changes of material parameters (say, phase mismatch, dispersion ratio). The results provide explicit understanding of the mechanism of soliton radiation in quadratic nonlinear media.

SIMULATION OF THE ROLLING PROCESS

The article presents the results of mathematical modeling of the process of rolling a heat-resistant nickel alloy disk blank. Modeling is carried out by the finite element method using a material model developed on the basis of the results of testing samples for compression and tension at temperatures of 1050, 1100 and 1150 °C and different strain rates. The material model is based on the theory of plastic flow with combined hardening. The developed model makes it possible to take into account the features of material deformation that occur during its cyclic loading at a variable speed, including the change in material parameters during the transition from one speed to another. The model is generalized to the case of non-isothermal loading. A method for identifying the parameters of the model is based on the results of the tests carried out and the obtained material functions are provided. The problem of the rolling process modeling is solved in a three-dimensional setting. To carry out the simulation, the developed model was introduced into the SimuliaAbaqus software package using a user subroutine. Based on the results of the calculation, cartograms of residual stresses, maximum values of plastic deformation, and values of displacements in the axial and radial directions at the end of the rolling process were obtained. The dependence of the change in plastic deformation in the process of rolling in the axial and radial directions is obtained, on the basis of which conclusions are drawn about the features of the deformation of the material in the process of rolling. The reliability of the results of mathematical modeling, the developed deformation model and the method for determining the material functions was confirmed by comparing the disk shape obtained as a result of the calculation with the disk shape obtained during the rolling process.

Parameters optimization of heterojunction ZnSe/CdS/CIGS/Si solar cells using SCAPS-1D software

It is required to simulate the performance of a photovoltaic solar cell performance to enhance it. Simulation optimization has the benefit of being inexpensive and straightforward, and it allows us to identify the optimum parameters that contribute to the enhancement of the cell. An alternative ZnSe/CdS/CIGS/Si structure has been presented using a solar cell capacitance simulator (SCAPS-1D). This paper aims to increase device efficiency by improving the physical characteristics of the many layers involved in cell realisation. We also tried to investigate the variation of electrical characteristics such as Voc, Jsc, , and FF with the changes in material parameters, notably the absorber layer thickness (CIGS, p-Si) (CIGS, p-Si). On the other hand, the temperature dependency has been simulated to guide device manufacturers to attain higher efficiency in varied temperature circumstances. The calculation result shows that excellent performance can be reached by varying the parameters, and the highest efficiency (24,94 %) of the solar cell can be reached under certain conditions, where the thicknesses of ZnSe, CdS, CIGS, and Si are 0.2m, 0.09m, 1.4m, and 0.6m respectively and for the optimal value of temperature equal to 295K.

Addendum: Multiaxial resonant MEMS force sensor (2018 J. Micromech. Microeng. 28 105002)

In this letter we present an MEMS Sensor to measure displacement in at least two directions. The sensor device is a resonant, Lorentz force driven and cross-shaped sensing structure whereas the measurement signal equals the change of the resonance frequency induced by the deformation of the sensor-frame. This device is a pre-study to implement the sensor in a two-dimensional micro manipulation system for which the team uses a micro system analyzer to detect the resonance frequencies of the different vibration modes. The sensor-frame deformation between 0.1 and 2 µm is generated by four piezo actuators. With this setup, the sensor achieves a sensitivity of up to 20 nm Hz−1. The device is fabricated from a 100 mm SOI wafer with standard CMOS processes and has two Pt1000 elements integrated on the device layer to compensate any effects caused by thermal extension of the structure or temperature induced changes of material parameters.

Sound absorption performance analysis of anechoic coating under hydrostatic pressure considering cavity pressure

Objectives An underwater anechoic coating layer laid on the hull surface of a submarine is squeezed under the action of high hydrostatic pressure, changing its shape and material parameters, which has a great impact on sound absorption performance. Therefore, studying the sound absorption performance of underwater anechoic coating layers under high hydrostatic pressure is of great significance for the stealth performance of submarines. Methods Considering the effects of cavity pressure on deformation and sound absorption performance of the annechoic coating layer under hydrostatic pressure, this paper uses axisymmetric finite element simulation to calculate the deformation of single cell with a cylindrical cavity, and the sound absorption coefficient curve is then obtained by converting the deformations into one-dimensional theoretical model. After that, structural-acoustic coupling analysis with the geometric model after deformation is carried out to verify the effectiveness of theorectical and numerical approaches for soloving the sound absorption coefficient. Results The results indicate that, without considering the changes of material parameters, the unit cells of the layer shrink axially and the cavity shrinks radially under hydrostatic pressure, while the sound absorption curve moves towards high frequency. The air pressure inside the cavity resists contraction under the action of hydrostatic pressure, weakening the trend of moving to high frequency. The sharp valley in the sound absorption curve is caused by the excitation of cavity mode. Conclusions The results of this study can provide valuable references for predicting the sound absorption performance of an anechoic coating layer under hydrostatic pressure.

The Analysis of Polyethylene Hip Joint Endoprostheses Strength Parameters Changes after Use inside the Human Body.

The influence of dynamic loads resulting from human motor activity and electrocorrosion inside the human body on the strength parameters of artificial joint elements has not yet been investigated. Hip joint arthroplasty is the most common surgical procedure in the world that allows doctors to remove pain and restore motor skills in people with severe hip diseases, after accidents, and in the elderly. Based on the reports, this article assesses changes in the number of implanted endoprostheses in the years 2005–2019 and determines the trends and estimated changes in the number of implanted hip prostheses in the following decades. The study assesses changes in selected strength parameters of UHMW-PE polyethylene inserts of hip joint endoprostheses during their use in the human body. The research was carried out on appropriately collected samples from UHMW-PE cups removed from the human body with a known history and lifetime from 4 to 10 years. Patients’ body weight ranged from 735 [N] to 820 [N], and the declared physical activity was similar in the entire research group. As part of the research, the values of changes in dynamic modules and the mechanical loss coefficient were determined in relation to the share of the crystalline and amorphous phases of artificial UHMW-PE cups, removed from the human body after different periods of exploitation under similar operating conditions. The analysis of selected strength parameters was performed at a temperature of 40 °C, which corresponds to the working conditions inside the human body. On the basis of numerical studies, the influence of changes in material parameters on the deformation of the artificial acetabulum during the patient’s motor activity, which is one of the causes of fatigue destruction, was determined.

Probing the effect of chiral dopant fluorination on dielectric and electro-optical properties of the ferroelectric liquid crystalline mixture

In this article, fluorinated chiral dopant-assisted tuning of dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) material is presented. Five new FLC mixtures with room temperature ferroelectric phase were formulated by fluorinating the phenyl core of chiral dopant at different positions and with a different number of fluorine atoms. The dielectric and electro-optical properties of all the FLC mixtures were systematically studied. It is found that the permittivity value of ferroelectric mesogens can be tuned between 5 and 36 (at 100 Hz) with fluorination. Also, the dielectric loss factor decreases owing to fluorination of chiral dopant with a shift in phason mode relaxation towards the low-frequency side. In addition, there is a significant change in material parameters of FLC, such as phase transition temperature, response time, spontaneous polarization, and rotational viscosity due to fluorination in chiral dopant. The presence of highly electronegative fluorine acts as a source of potentially repulsive force. It partially screens the molecular chirality of the dopant, which resulted in a change in the material parameters of FLCs. Interestingly, there is no considerable change in the mesogenic structure and orientation with the addition of fluorine, which is confirmed through wide-angle X-ray scattering. These studies open up a new avenue for tailoring the dielectric and electro-optical properties of mesogens for advanced device applications based on FLCs.

Tunable Magnetic Fano Resonances on Au Nanosphere Dimer–Dielectric–Gold Film Sandwiched Structure

The Fano resonance demonstrates excellent performance due to its narrow asymmetrical spectral line shape, and its sensitivity to structure and material parameter changes. Compared to conventional Fano resonances, the Fano resonance generated by the magnetic dipole is more advantageous because of its high absorption and low loss. In this study, we propose an Au nanosphere dimer–dielectric–gold film sandwiched structure that supports the magnetic Fano resonance mode. And the Fano resonance can be efficiently tuned from visible to near-infrared wavelength by changing the size of the gold nanospheres and the thickness of the dielectric layer. Different from the single gold nanosphere–dielectric–film structure, the results suggest that the proposed structure is sensitive to the polarization direction of the excitation light. Considering the above characteristics, the proposed structure can be applied in multi-band sensing, surface-enhanced Raman spectroscopy, and dynamically adjustable optical switches.

Transportation of topological spin textures at material boundaries

Using skyrmions or skyrmionium as information storage, e.g., racetrack memory, requires a basis of knowledge on how these topological spin structures react to changes in material parameters, which can be, for instance, purposed for stable storing, efficient writing, and faster transportation. Here, we examine the dynamics of topological spin textures, magnetic skyrmions and skyrmionium at the boundaries where material properties vary. Using micromagnetic simulations, we investigated the dependence of the location and radius variation in exchange stiffness, magnetic saturation, Dzyaloshinskii–Moriya Interaction, and anisotropy. There is also a comparison made between the feasibility of skyrmionium as an alternative to skyrmions as a method of storing and transportation information.

Electric properties of olive oil under pressure

The main purpose of the experiment was a thermodynamic research with use of the electric methods chosen. The substance examined was olive oil. The paper presents the resistance, capacitive reactance, relative permittivity and resistivity of olive. Compression was applied with two mean velocities up to 450 MPa. The results were shown as functions of pressure and time and depicted on the impedance phase diagram. The three first order phase transitions have been detected. All the changes in material parameters were observed during phase transitions. The material parameters measured turned out to be the much more sensitive long-time phase transition factors than temperature. The values of material parameters and their dependence on pressure and time were compared with the molecular structure, arrangement of molecules and interactions between them. Knowledge about olive oil parameters change with pressure and its phase transitions is very important for olive oil production and conservation.

A time series classification approach to non-destructive hardness testing using magnetic Barkhausen noise emission

The process setup of manufacturing processes is generally knowledge-based and carried out once for a material batch. Industry experts observe fluctuations in product quality and tool life, albeit the process setup remains unchanged. These fluctuations are mainly attributed to fluctuations in material parameters. An in-situ detection of changes in material parameters would enable manufacturers to adapt process parameters like forces or lubrication before turbulences like unexpectedly high tool wear or degradation in product quality occurs. This contribution shows the applicability of a deep learning time series classification architecture that does not rely on handcrafted feature engineering for the classification of hardness fluctuations in a sheet-metal coil using magnetic Barkhausen noise emission. This methodology is not limited to the detection of hardness fluctuations in sheet-metal coils and can potentially be applied for the in-situ material property classification in different manufacturing processes and for different material parameters.

A numerical study on the effects of spatial and temporal discretization in cardiac electrophysiology.

Millions of degrees of freedom are often required to accurately represent the electrophysiology of the myocardium due to the presence of discretization effects. This study seeks to explore the influence of temporal and spatial discretization on the simulation of cardiac electrophysiology in conjunction with changes in modeling choices. Several finite element analyses are performed to examine how discretization affects solution time, conduction velocity and electrical excitation. Discretization effects are considered along with changes in the electrophysiology model and solution approach. Two action potential models are considered: the Aliev-Panfilov model and the ten Tusscher-Noble-Noble-Panfilov model. The solution approaches consist of two time integration schemes and different treatments for solving the local system of ordinary differential equations. The efficiency and stability of the calculation approaches are demonstrated to be dependent on the action potential model. The dependency of the conduction velocity on the element size and time step is shown to be different for changes in material parameters. Finally, the discrepancies between the wave propagation in coarse and fine meshes are analyzed based on the temporal evolution of the transmembrane potential at a node and its neighboring Gauss points. Insight obtained from this study can be used to suggest new methods to improve the efficiency of simulations in cardiac electrophysiology.

Constitutive model for epoxy shape memory polymer with regulable phase transition temperature

ABSTRACT The epoxy shape memory polymer (SMP) with adjustable phase transition temperature is a kind of high-performance shape memory polymer, which can change its phase transition temperature and improve its mechanical properties through the process of photo curing. An epoxy SMP constitutive model combining phase transition and viscoelasticity is established by discretizing the epoxy SMP into several glass phase units and rubbery phase units in this paper. The model includes the viscoelastic constitutive equations of glass phase units and rubber phase units, the parameter expression during shape memory process, and material parameter equation during photocuring process. And the stress relaxation behavior of epoxy SMP at different temperatures and the change of material parameters during the photo-curing process are simulated numerically, and the simulation results perform consistency with the experimental data. The model can not only relate shape memory effect and phase transformation in physics but also better characterize the viscoelastic properties of SMP and predict the shape memory response of SMP.