Changes In Material Properties Research Articles

Theory for a non-invasive diagnostic biomarker for craniospinal diseases

Monitoring intracranial pressure (ICP) and craniospinal compliance (CC) is frequently required in the treatment of patients suffering from craniospinal diseases. However, current approaches are invasive and cannot provide continuous monitoring of CC. Dynamic exchange of blood and cerebrospinal fluid (CSF) between cranial and spinal compartments due to cardiac action transiently modulates the geometry and dielectric properties of the brain. The resulting impedance changes can be measured and might be usable as a non-invasive CC surrogate. A numerically robust and computationally efficient approach based on the reciprocity theorem was developed to compute dynamic impedance changes resulting from small geometry and material property changes. The approach was successfully verified against semi-analytical benchmarks, before being combined with experimental brain pulsation data to study the information content of the impedance variation. The results indicate that the measurable signal is dominated by the pulsatile displacement of the cortical brain surface, with minor contributions from the ventricular surfaces and from changes in brain perfusion. Different electrode setups result in complementary information. The information content from the investigated three electrode pairs was employed to successfully infer subject-specific brain pulsation and motion features. This suggests that non-invasive CC surrogates based on impedance monitoring could be established.

Sterilization effects on poly(glycerol dodecanedioate): A biodegradable shape memory elastomer for biomedical applications.

Biodegradable shape memory polymers provide unique regenerative medicine approaches in minimally invasive surgeries. Once heated, thermally responsive shape memory polymer devices can be compressed, programmed to fit within a small profile, delivered in the cold programmed state, and expanded when heated to body temperature. We have previously developed a biodegradable shape memory elastomer (SME), poly(glycerol dodecanedioate) (PGD), with transition temperatures near 37°C exhibiting nonlinear elastic properties like numerous soft tissues. Using SMEs in the clinic requires disinfection and sterilization methods that conserve physiochemical, thermomechanical, and shape recovery properties. We evaluated disinfection protocols using 70% ethanol and UV254 nm for research applications and ethylene oxide (EtO) gas sterilization for clinical applications. Samples disinfected with ethanol for 0.5 and 1 min showed no changes in physiochemical material properties, but after 15 min showed slower recovery rates than controls (p < .05). EtO sterilization at 54.4°C decreased transition temperatures and shape recovery rate compared to EtO sterilization at 37.8°C (p < .01) and controls (p < .05). Aging samples for 9 months in a vacuum desiccator significantly reduced shape recovery, and the recovery rate in EtO sterilized samples compared to controls (p < .001). Cytotoxicity testing (ISO-10993.5C:2012) revealed media extractions from EtO sterilized samples, sterilized at 37.8°C, and high-density polyethylene negative control samples exhibit lower cytotoxicity (IC50) than Ethanol 1min, UV 2h, and EtO 54.4°C. Cell viability of NIH3T3 fibroblasts on sterilized surfaces was equivalent on EtO 37.7°C, EtO 54.4°C and Ethanol sterilized substrates. Finally, chromogenic bacterial endotoxin testing showed endotoxin levels were below the FDA prescribed levels for devices contacting blood and lymphatic tissues for ethanol 1min, UV 120 min, EtO 37.7°C, EtO 54.4°C. These findings outline various disinfection and sterilization processes for research and pre-clinical application and provide a pathway for developing custom sterilization cycles for the translation of biomedical devices utilizing PGD shape memory polymers.

Rapid Determination of Changes in Material Properties of Water Turbines Blades

The changes in the material properties of water turbine blades are characterized an undesirable process, which could lead to the end of usable life or to the emergency conditions of this turbine. For this reason, it is important to determine of any material quality changes and continuously monitor them. Considering that, these essential parameters are showing the ability of material to resist the operational stress. It is necessary to choose rapid methods of the material testing which are without preparation of the samples (it is inadmissible to the functional blades) able to immediately monitor the state of the materials by non-destructive methods. Due to mechanical stress and operational wear, the losses and damage occur in the water turbine blades, as the result, it leads to the deformation changes. This article is focused on the methodology of determination mechanical properties of corrosion-resistant steel, which is used on a large scale for the production of hydraulic elements and especially blades of water turbines.

Effect of blank quenching on shear spinning forming precision of 2219 aluminum alloy complex thin-walled components

The quenching-spinning (Q-S) process, i.e., shear spinning after blank quenching, has been increasingly utilized to form 2219 aluminum alloy complex thin-walled components. However, the changes in material property, shape and stress of the blanks after quenching will affect the spinning forming precision. In this study, the rules and mechanisms of these effects are investigated based on a combined finite element (FE) model including blank quenching and component spinning process. The results indicate that the increase of material strength and the existence of distortion of the quenched blank lead to a notable increase in the non-uniformity of the circumferential compressive stress in the spinning area and the increase of the flange swing height during spinning. These changes result in an increase in the wall thickness and component-mandrel gap of the components. The quenching residual stress has little effect on wall thickness and roundness but can noticeably reduce the component-mandrel gap. This is because that the existence of quenching residual stress of the blank can lead to the decrease of the maximum circumferential compressive stress of the workpiece in spinning and an obvious drop in the maximum compressive stress after reaching the stress peak. Quenching distortion is the main factor affecting the roundness. Moreover, the optimized installation way of the blank for spinning is obtained.

Related Reviews: Multiband Planar Inverted Antenna for Mobile Communication

Research in the field of planar inverted antennas with multiband frequencies is currently being developed. Due to the hugely increased number of mobile users, at least every time a new generation is released, a mobile communication system is released with additional features. All additional features of a mobile communication system require an antenna that resonates over a specific frequency spectrum range, meaning multiple antennas are required in a single mobile device to function across all generations for all frequency spectrums. To reduce the number of antennas on a mobile communication system device, it is necessary to design a new type of antenna that operates in a different frequency range. The inverted planar multiband antenna is designed to have changing sizes, shapes, and material properties. Types of inverted planar antennas include planar inverted-L antennas (PILA) and planar inverted-F antennas (PIFA). After analysis, the antenna designed by Juan Zhang et al. is the best solution for mobile communication systems. The designed antenna has compact antenna dimensions and four frequency bands that can be applied to N1/N78/N79 5G and 5.8 GHz WLAN. The antenna has a high gain of almost 5dB in the 5.60–7.00 GHz frequency range. They also claim that the antenna has a beam efficiency of four very high-frequency antenna points and a small side lobe that appears only at the top at the highest frequency point. But unfortunately, the antenna cannot cover the entire frequency range that must exist in a mobile communication system

Determination of Grain Growth Kinetics of S960MC Steel.

Fine-grained high-strength low-alloyed (HSLA) steels are used for their advantageous combination of mechanical properties such as high yield strength, tensile strength, ductility, and good formability. These properties are mainly based on applied grain boundary strengthening, which as the only strengthening mechanism allows for the yield strength to increase without a decrease in ductility. Therefore, any changes in grain size lead to irreversible changes in material properties. Such changes also occur during welding in the heat-affected zone (HAZ), where there is a significant change in austenitic grain. In coarse-grain HAZ, this leads to a decrease in yield strength, ductility, toughness, and fatigue strength. The paper experimentally determines the growth kinetics of austenitic grain for fine-grained HSLA steel S960MC. As a result, the values of the activation energy required for grain growth Q and the proportional constant K0 are determined. Knowing these values is important for numerical predictions of austenitic grain size in the HAZ. Based on these predictions, the changes in yield strength, ductility, toughness, and fatigue strength can be estimated.

Acoustic radiation through a flexible shell in a bifurcated circular waveguide

The current study models and explains the fluid–structure coupled response of a flexible shell connected with two rigid coaxial shells via circular step discontinuities. Radiations from annular and inner regions of inlet rigid shells scatter on interfaces after interaction with the geometric variations and change of material properties. The flexible shell that supports vibrations along the shell is expressed though the Donnell–Mushtari formulation in the differential system. The mode‐matching technique is applied to solve the governing boundary value problem. The solution is projected on the orthogonal characteristics which in flexible casing is generalized as compared with the properties of acoustically rigid setting. The implication of generalized orthogonality relations governs additional constants that are found by defining the physical connection of shell with rigid disc. The clamped and pin‐jointed conditions are considered in this article. The scattering powers and transmission loss are analyzed against frequency, chamber length, and radii of shells for clamped and pin‐jointed edge conditions. It is found that the power propagation in annular shell and inner shell behave conversely. Moreover, configuration can be attenuated through the variation of dimensions of chamber and edge conditions.

Polyolefins Vitrimers: Design Principles and Applications

Less than 10% of plastics are recycled worldwide, among which polyolefins, which form two-thirds of all produced polymers, are the most discarded ones. This stems from the nonpolar nature of polyolefins, which limits their degradation and recycling. As such, any approach that may promote the recycling of polyolefins can significantly shift the statistics of polymer recycling toward a more sustainable future. To account for that, the vitrimer concept proposes a unique solution that not only increases the polarity of polyolefins, and as such promotes their degradation, but also expands the utility of polyolefin elastomers and compensates for the significant loss of mechanical properties upon sequential mechanical recycling in thermoplastic polyolefins. Vitrimers are polymer networks formed by reversible covalent cross-links that undergo percolation-conserving exchange reactions at high temperatures. Therefore, while they form a solid network at the service conditions, they can be reprocessed and recycled above a temperature threshold. Thanks to this, they have applications at the interface of thermoplastics and thermosets ranging from recyclable, self-healing, and adhesive materials to creep-resistant and shape-memory networks. This Review aims to classify cross-linking chemistries employed for the production of polyolefin-derived vitrimers and highlight subsequent changes in material properties and applications to promote further development of novel polyolefin vitrimers.

Aeroelastics-aware compensation system for soft aerial vehicle stabilization.

This paper describes a compensation system for soft aerial vehicle stabilization. Balancing the arms is one of the main challenges of soft UAVs since the propeller is freely tilting together with the flexible arm. In comparison with previous designs, in which the autopilot was adjusted to deal with these imbalances with no extra actuation, this work introduces a soft tendon-actuated system to achieve in-flight stabilization in an energy-efficient way. The controller is specifically designed for disturbance rejection of aeroelastic perturbations using the Ziegler-Nichols method, depending on the flight mode and material properties. This aerodynamics-aware compensation system allows to further bridge the gap between soft and aerial robotics, leading to an increase in the flexibility of the UAV, and the ability to deal with changes in material properties, increasing the useful life of the drone. In energetic terms, the novel system is 15-30% more efficient, and is the basis for future applications such as object grasping.

Residual magnetic field as a source of information about steel wire rope technical condition

Abstract Research has been undertaken to analyze the possibilities of using the residual magnetic field, as a result of local changes in the electromagnetic properties of the rope material, for identification of steel wire rope technical condition. Under the influence of cyclically changing workloads, due to the effects of magnetomechanics, changes in electromagnetic properties occur both in the wires and in the entire rope. The article presents the use of magnetic sensors to determine the relationship between the number of steel wire rope bends and its magnetic field induction value. This knowledge, referred to as ropes working on real objects, allows us to determine the state of stress prevailing in them as well as their technical condition.

Modified Polyethylene Foam for Critical Environments.

One of the most important priorities for all countries with property beyond the Arctic Circle and territories located in permafrost areas is the development of special construction technologies and systems. The required conditions are met by insulation systems based on seamless insulation shells made of polyethylene foam. The study of the strength and performance properties of polyethylene foam and its combinability was carried out according to standard methods and using the methods of experimental design and the analytical processing of the results. The change in material properties at negative temperatures was determined based on the results of climatic tests, followed by an evaluation of creep under load. The evaluation of the effectiveness of the design solutions was carried out using special computer programs. It was found that the performance characteristics of products made of polyethylene foam (rolls, mats) meet the requirements for insulation materials used at temperatures down to -60 °C. The resulting material is moderately combustible, which must be taken into account when developing recommendations for its use in insulation systems. A nomogram has been developed that makes it possible to predict the properties of a material and solve formulation problems. Insulation systems were developed, and a visualisation of the thermal fields of the insulation systems of the external walls and ceilings of a building was carried out.

Correlative surface and bulk analysis of deep cryogenic treatment influence on high-alloyed ferrous alloy

In this study we investigate the effect of deep cryogenic treatment (DCT) on a high-alloyed ferrous alloy (HAFA) to understand the resulting chemical and physical changes to the HAFA's microstructure and properties. Using multiple materials analysis techniques, we uncover the fundamental chemical changes to the HAFA with DCT, and link changes in material properties to changes in the microstructure. The increased carbide nucleation with DCT is linked to greater solute mobility resulting from the modified stress state of the material and modified chemical bonding of the solutes with the matrix. In turn this provides the possibility of prior formation of nucleation points for primordial carbide formation that act as accelerators for both nucleation and evolution of carbides. These result in modified chemical and microstructural homogeneity of the material that fundamentally led to changes in the surface properties and applicability of HAFA in advanced wear, corrosion and fatigue resistance demanding conditions.

Ultra-Rapid, Physics-Based Development Pathway for Reactor-Relevant RF Antenna Materials

This article presents a rapid, atomistically informed, experimental development pathway for fusion reactor-relevant radio-frequency (RF) antenna materials in the Cu-Cr-(Nb,Al,Zr) composition system, with the goal of improving upon GRCop-84. RF antennas in a tokamak fusion reactor will face a unique set of challenges as both structural and functional materials. The desired material must simultaneously achieve and maintain high electrical conductivity, high strength, high thermal conductivity, resist high temperatures, possess low nuclear activation, and incur low damage due to neutron bombardment. The GRCop-84 alloy serves as a starting point for iterative improvement, with the desire to reduce or eliminate Nb from the material to minimize nuclear activation. The rapid development pathway makes use of a multi-target combinatorial thick-film sputtering process to produce full ternary phase diagrams on a Si wafer substrate. Transient grating spectroscopy (TGS), a laser-ultrasonic method, will determine spatially varying thermoelastic properties, while four terminal electrical conductivity measurements will map out the best performing regions of the sample for in-depth study at larger length scales. High-energy proton and self-ion irradiation emulates the effects of neutron damage on the thermal/electric properties. With rapid turnaround time (~days) in terms of mapping radiation damage-induced material property changes in the full ternary system, these techniques allow rapid iteration toward an optimal material, testing hundreds of nearby compositions in the time it took to test one. Focused testing of larger, single composition samples (produced in an arc furnace or by laser sintering) provides data on structural and high-power RF properties and validates our thick-film-based workflow.

Surface ionization waves propagating over non-planar substrates: wavy surfaces, cut-pores and droplets

Atmospheric pressure plasmas intersecting with dielectric surfaces will often transition into surface ionization waves (SIWs). Several applications of these discharges are purposely configured to be SIWs. During propagation of an SIW over a dielectric surface, the plasma charges the surface while responding to changes in geometrical and electrical material properties. This is particularly important for non-planar surfaces where polarization of the dielectric results in local electric field enhancement. In this paper, we discuss results from computational investigations of negative and positive SIWs propagating over nonplanar dielectrics in three configurations—wavy surfaces, cuts through porous materials and water droplets on flat surfaces. We found that negative SIWs are particularly sensitive to the electric field enhancement that occurs at the crests of non-planar surfaces. The local increase in ionization rates by the electric field enhancement can result in the SIW detaching from the surface, which produces non-uniform plasma exposure of the surface. Positive SIWs tend to adhere to the surface to a greater degree. These trends indicate that treatment of pathogen containing droplets on surfaces may be best performed by positive SIWs. The same principles apply to the surfaces cut through pores. Buried pores with small openings to the SIW may be filled by plasma by either flow of plasma into the pore (large opening) or initiated by photoionization (small opening), depending on the size of the opening compared to the Debye length.

Natural frequency analysis of imperfect GNPRN conical shell, cylindrical shell, and annular plate structures resting on Winkler-Pasternak Foundations under arbitrary boundary conditions

The goal of the present research is to examine the Natural Frequencies (NFs) of perfect and imperfect Graphene Nanoplatelet Reinforced Nanocomposite (GNPRN) structures of revolution (conical and cylindrical shells and annular plate structures) resting on elastic foundations under general boundary conditions (BCs). The graphene nanoplatelet material is implemented to compose the nanocomposite enhanced by a polymeric matrix including porosities. The springs technique is applied to define the general BCs of GNPRN structures of revolution. Elastic foundations are described by two parameters, i.e., Winkler-Pasternak Foundations (WPFs). Additionally, Donnell's hypothesis and first-order shear deformation theory (FSDT) are employed to figure out the primary formulations associated with the GNPRN structures of revolution. In contrast, the equations of motion are found using Hamilton's principle. Then the equations of motion are then discretized using the well-known Generalized Differential Quadrature Method (GDQM). Next, the standard eigenvalue solution is assigned to obtain the NFs of the perfect/imperfect GNPRN structures of revolution. Finally, various benchmarks are addressed to verify the approach suggested for evaluating the NFs of the perfect/imperfect GNPRN structures of revolution. Furthermore, several novel examples highlight the effects of the change in geometrical and material properties, arbitrary boundary conditions, and WPFs on the NFs of the perfect/imperfect GNPRN structures of revolution.

Tuning material properties via disorder: From crystalline alloy to metallic glass

Pathways to tune the electronic, chemical, mechanical, and optical properties of solids without modifying their composition represent a new paradigm in the design of functional and sustainable materials. The level of structural disorder - from perfectly crystalline to fully amorphous – for example, induces remarkable changes in material properties. Typically, disorder is introduced by altering the composition of a material, adding to the misconception that these two properties cannot be decoupled. Here, we demonstrate that striking differences in the optical, electronic, and corrosion properties of CuZr are achieved by deliberately and reproducibly engineering the level of structural disorder in pulsed laser deposited thin films of a constant composition. This approach allows tuning the structure of CuZr from polycrystalline to fully amorphous, switching the nature of charge transport from metallic to semiconductor-like, the optical properties in the visible regime from opaque to transparent, and the corrosion behavior in air from mixed oxidation to the formation of a protective Zr oxide overlayer. Our results highlight the tunability of structural disorder in alloys and its remarkable effect on material properties, providing the opportunity to design sustainable functional materials based on customizing properties beyond their composition.

Evaluation of fatigue damage of a railhead using an indentation test, acoustic methods and microstructural observations

The paper presents an investigation of the railhead steel R260. Brinell hardness was measured, spherical microindentation tests were performed and the microstructure was analysed using optical microscopy and SEM images. Fatigue damage in various near-surface regions of the railhead was estimated on the basis of local deterioration of elastic modulus and the development of plastic work in cyclic microindentation tests. There is a clear difference in hardness and fatigue damage between the used and the virgin regions of the railhead. The Brinell hardness and ultrasonic measurements show a change in material properties due to rail manufacturing process.

Energy and daylighting performance of a building containing an innovative glazing window with solid-solid phase change material and silica aerogel integration

Responding to the appeal of realizing carbon neutrality in response to the field of buildings, minimizing the energy demand and improving the energy management of the buildings by the development of energy saving technologies related to transparent components are considered as promising means. In this paper, an innovative glazing window integrated with solid-solid phase change material and silica aerogel is proposed, and a parametric study is conducted with a focus on evaluating the implementation potential of our innovative window in the severe cold region of China. Firstly, to address the issue that the transparent media such as phase change material and silica aerogel cannot be directly incorporated into glazing elements of EnergyPlus software, an equivalent model of the innovative window compatible with the modeling capabilities of EnergyPlus is developed. Then, the contributions of the thermal and optical properties of phase change material to energy savings are quantitively distinguished via sensitivity analysis. Additionally, the energy performance of the building containing the innovative window under different thermal and optical properties of phase change material is numerically investigated aiming to provide guidance to the design strategies of phase change material parameters adopted in the innovative window. Finally, in light of counterbalancing the need for energy saving and daylighting performance indoors, the optimal silica aerogel thickness employed in the innovative window is studied. The results show that the phase change material properties of melting temperature, latent heat, absorption coefficient, and refractive index are of remarkable relevance to the energy performance of the buildings in conditions of 10 % property variations. In comparison to the 4 mm single glazing window installed, the maximum energy saving of the building containing the innovative window can be realized by 18.22 % within the realistic range of phase change material properties. Moreover, for the sake of providing the maximum possibility of energy saving under the premise of meeting the daylighting design standards in China, the thickness of silica aerogel is recommended to be selected as 10 mm in the innovative window.

Factors affecting the numerical response and fracture location of the GHBMC M50 rib in dynamic anterior-posterior loading

Rib fractures are common traumatic injuries, with links to increased morbidity and mortality. Finite element ribs from human body models have struggled to predict the force-displacement response, force and displacement at fracture, and the fracture location for isolated rib tests. In the current study, the sensitivity of a human body model rib with updated anisotropic and asymmetric material models to changes in boundary conditions, material properties, and geometry was investigated systematically to quantify contributions to response. The updated material models using uncalibrated average material properties from literature improved the force-displacement response of the model, whereas the cross-sectional geometry was the only parameter to effect fracture location. The resulting uncalibrated model with improved material models and cross-sectional geometry closely predicted experimental average force-displacement response and fracture location.

Influence of temperature on the compression behavior of pharmaceutical excipients

Tableting on an industrial scale is characterized by an increase in temperature, which is dependent on numerous factors. The aim of this study was to examine the glass transition temperature of frequently used polymers as a critical parameter on tablet properties. Tablets were produced in a tablet press equipped with a temperature-controlled die at four different temperatures ranging from 22 to 70 °C. While pure polymers were characterized for their temperature-dependent compressibility behavior using Heckel analysis, tableting was performed from binary blends containing lactose as a filler and the polymer to be examined (ratio 9:1). Tablets were characterized in terms of tabletability, compactibility and their correlation with the glass transition temperature. The decrease in mean yield pressure upon temperature rise could clearly be correlated to the glass transition temperature of a given polymer, whereby polymers with low glass transition temperatures proved to be more responsive to temperature changes. Tablet properties were equally affected by the applied temperature despite the low polymer content. Thus, polymers with higher glass transition temperatures should be preferred in a full-production scale to avoid an alteration of tablet characteristics, whereas polymers with lower glass transition temperatures could be advantageous if a change of material properties is desired.