Electromechanical-Mode Coupling Model and Failure Prediction of CFRP under Three-Point Bending

Carbon fiber reinforced polymer materials (CFRP) cause CFRP to bend or fail when subjected to external loads or impacts. In the case of static three-point bending, using the conductive properties of the carbon fiber inside the CFRP, the overall damage detection and failure prediction can be carried out by electromagnetic methods. The eddy current coil is used to realize real-time monitoring of damage, and the measured voltage value can be mapped to obtain the load of the sample. This paper conducts theoretical analysis and experimental verification, and obtains the relationship between CFRP stress damage and spatial conductivity change, and proposes a CFRP electromechanical coupling model under quasistatic three-point bending. Combined with the theory of electrically ineffective length, the CFRP three-point bending electromechanical coupling model was revised. Experimental results prove that the revised model can describe the load-conductivity change trend of three-dimensional braided CFRP more accurately, which provides a theoretical basis for monitoring the structural health of CFRP through electromagnetic methods.

Code control for parametric models of induction heaters

In this paper, we describe our approach to building controllable models of induction heaters. Parameters of equivalent circuits of aluminum heating inductors include certain components tied to secondary elements. As long as metal properties are subject to change during the heating process, resistive and reactive parts of equivalent circuits should be taken into account. Adjustable resistive components have rarely been used in circuit models. To control equivalent resistive two-terminal parts, we offer pulse code control of impedance-changing switches. Controlling switching time in models with series, parallel, and mixed connection provides required softness of resistive conductivity change. Control characteristics of current and voltage were obtained with use of a simulator. As the result of our numerical experiment, the set of operating parameters for an induction device was determined.

Low-molecular components of colostrum as a regulator of the organism redox-system and biological antidote

The protein composition in the diapason of molecular masses from 4800 to 9500 Dа has been studied in colostrum, taken from different cows, and manifested the expressed biological activity. For this aim, an influence of low-molecular components of colostrum on some physiological parameters (change of body mass and temperature) at intoxication of animals (Wistar rats) by blue stone has been studied. An influence of colostrum low-molecular components on parameters of the organism redox-system (content of hyperperoxides of lipids and activity of glutathione peroxidase) in the blood serum of animals has been studied. For determining integral characteristics of colostrum components, electric conductivity of skim colostrum and one of colostrum with low-molecular proteins (less than 10 000 Dа), taken from different cows, were used. The aim of this work is to study interconnections of an influence of colostrum low-molecular proteins on models of organism intoxication by cooper ions. It is demonstrated, that the colostrum composition includes 25–35 different proteins with a molecular mass from 4800 to 9500 Dа. The number and ratio between protein fractions depend on individual physiological-biochemical characteristics of producers. It has been revealed, that there is no direct dependence between the protein content in a measuring cell (2 mg/ml, 4 mg/ml and 10 mg/ml) with skim colostrum and electric conductivity change, and this dependence is different for skim colostrum, taken from different cows. Individual differences are manifested both at electric conductivity change and by the content of colostrum low-molecular proteins in a measuring cell. It is demonstrated, that colostrum low-molecular components can eliminate the toxic effect of blue stone on the organism, which mechanisms are connected with a balance shift in the system “prooxidants↔antioxidants” towards antioxidants. The electric conductivity of colostrum components may be used as an express-method for evaluating biologically active substances of colostrum

Imaging Conductivity Changes in Monolayer Graphene Using Electrical Impedance Tomography

Recently, graphene has gained a lot of attention in the electronic industry due to its unique properties and has paved the way for realizing novel devices in the field of electronics. For the development of new device applications, it is necessary to grow large wafer-sized monolayer graphene samples. Among the methods to synthesize large graphene films, chemical vapor deposition (CVD) is one of the promising and common techniques. However, during the growth and transfer of the CVD graphene monolayer, defects such as wrinkles, cracks, and holes appear on the graphene surface. These defects can influence the electrical properties and it is of interest to know the quality of graphene samples non-destructively. Electrical impedance tomography (EIT) can be applied as an alternate method to determine conductivity distribution non-destructively. The EIT inverse problem of reconstructing conductivity is highly non-linear and is heavily dependent on measurement accuracy and modeling errors related to an accurate knowledge of electrode location, contact resistances, the exact outer boundary of the graphene wafer, etc. In practical situations, it is difficult to eliminate these modeling errors as complete knowledge of the electrode contact impedance and outer domain boundary is not fully available, and this leads to an undesirable solution. In this paper, a difference imaging approach is proposed to estimate the conductivity change of graphene with respect to the reference distribution from the data sets collected before and after the change. The estimated conductivity change can be used to locate the defects on the graphene surface caused due to the CVD transfer process or environment interaction. Numerical and experimental results with graphene sample of size 2.5 × 2.5 cm are performed to determine the change in conductivity distribution and the results show that the proposed difference imaging approach handles the modeling errors and estimates the conductivity distribution with good accuracy.

A numerical study on the effect of conductivity change in cell kill distribution in irreversible electroporation

Introduction: irreversible electroporation (IRE) is a tissue ablation technique and physical process used to kill the undesirable cells. In the IRE process by mathematical modelling we can calculate the cell kill probability and distribution inside the tissue. The purpose of the study is to determine the influence of electric conductivity change in the IRE process into the cell kill probability and distribution.Methods: cell death probability and electric conductivity were calculated with COMSOL Multiphysics software package. 8 pulses with a frequency of 1 Hz, pulse width of 100 µs and electric field intensity from 1000 to 3000 V/Cm with steps of 500 V/Cm used as electric pulses.Results: significantly, the electrical conductivity of tissue will increase during the time of pulse delivery. According to our results, electrical conductivity increased with an electric field intensity of pulses. By considering the effect of conductivity change on cell kill probability, the cell kill probability and distribution will change.Conclusion: we believe that considering the impact of electric conductivity change on the cell kill probability will improve the accuracy of treatment outcome in the clinic for treatment with IRE.

Stretching-Induced Thermal Conductivity Change in Shape-Memory Polymer Composites

Active thermal materials like thermal diodes, regulators, and switches have the potential to revolutionize thermal management, creating an opportunity for significant energy savings. We present results on a thermal switching composite that changes its thermal conductivity based on applied strain. The composite is constructed of highly-crystalline, high aspect ratio cellulose nanocrystal (CNC) nanorods embedded in a shape-memory polymer matrix. The properties of the matrix allow for changes to the thermal state to be indefinitely retained and also for the state to be reversed. A switching ratio of two is achieved for this proof-of-concept composite. By comparing the measured results to a Maxwell mixing model, the primary drivers of the thermal conductivity change are traced to changes in crystallinity of the matrix and CNC alignment.