Changes In Material Properties Research Articles

Wurtzite nanowires strain control by DC electrical stimulation

Nanomechanics is a highly developed area of research, given the significant reported changes in material properties at the nanometer scale, requiring the development of new theories to explain the underlying mechanisms. Such theories must be based on measurements that are as accurate as possible, but unfortunately, conventional experimental techniques do not apply to such small components. Here we present a unique new method to control electro-mechanical forces on quasi −1D nanostructures through static electric fields with multiple ways of control of GaAs nanowires’ strain directly on the growth substrate.

Experimental study on time dependent behaviour of coarse aggregate concrete mixture for 3D construction printing

This experimental study analyses coarse aggregate-containing and coarse aggregate-free materials from the perspective of additive manufacturing. The primary objective is to identify, through a series of experiments, the fundamental equations that characterise material behaviour at early ages in order to formulate a digital material model. During the research, a previously unreported phenomenon, namely the contradictory development of Young's modulus and cohesion, was observed. In addition, the sensitivity of buildability to changes in material properties was discussed and demonstrated with a motivating example using a spatiotemporal simulation of 3D-printed concrete.

Testing of a Polymer Drill String Protector under Conditions close to Borehole

With today's proliferation of various polymers, it is necessary to assess the feasibility and feasibility of replacing rubber with more modern materials. The purpose of the tests was to study the effect of abrasive wear, the effect of temperature on material properties, resistance to chipping and other types of wear. This will allow assessing the possibility of application in well conditions, as well as determining the magnitude of the effect of each type of wear on the product. We were faced with the task of testing new protectors in conditions close to full-scale ones. For this, a stand was designed, which allows you to reproduce the lateral load, add abrasive and corrosive agents that affect the wear of the product, ensure circulation of the model fluid, with the characteristics of the drilling fluid, as well as study the effect of elevated temperature on the change in material properties. Due to the fact that in a real well the protector is not under constant load, especially in the vertical sections of the wellbore, but can rotate on the pipe, a day on the test bench can be equivalent to months when the protector is in the well. Therefore, the tests carried out can predict the wear of tread parts, as well as assess the reliability of the use of treads made of polymer materials.

Thermoluminescent characterization and defect studies of graphite-rich media under high dose neutron exposure

Thermoluminescence (TL) materials have a broad variety of uses in various fields, such as clinical research, individual dosimetry, and environmental dosimetry, amongst others. However, the use of individual neutron dosimetry has been developing more aggressively lately. In this regard, present study establishes a relationship between the neutron dosage and the optical property changes of graphite-rich materials caused by high doses of neutron radiation. This has been done with the intention of developing a novel, graphite-based radiation dosimeter. Herein, the TL yield of commercially graphite-rich materials (i.e. graphite sheet, 2B and HB grade pencils) irradiated by neutron radiation with doses ranging from 250 Gy to 1500 Gy has been investigated. The samples were bombarded with thermal neutrons as well as a negligible amount of gamma rays, from the nuclear reactor TRIGA-II installed at the Bangladesh Atomic Energy Commission. The shape of the glow curves was observed to be independent of the given dosage, with the predominant TL dosimetric peak maintained within the region of 163 °C–168 °C for each sample. By studying the glow curves of the irradiated samples, some of the most well theoretical models and techniques were used to compute the kinetic parameters such as the order of kinetics (b), activation energy (E) or trap depth, frequency factor (s) or escape probability, and trap lifetime (τ). All of the samples were found to have a good linear response over the whole dosage range, with 2B grade of polymer pencil lead graphite (PPLGs) demonstrating a higher level of sensitivity than both HB grade and graphite sheet (GS) samples. Additionally, the level of sensitivity shown by each of them is highest at the lowest dosage that was given, and it decreases as the dose increases. Importantly, the phenomenon of dose-dependent structural modifications and internal annealing of defects has been observed by assessing the area of deconvoluted micro-Raman spectra of graphite-rich materials in high-frequency areas. This trend is consistent with the cyclical pattern reported in the intensity ratio of defect and graphite modes in previously investigated carbon-rich media. Such recurrent occurrences suggest the idea of employing Raman microspectroscopy as a radiation damage study tool for carbonaceous materials. The excellent responses of the key TL properties of the 2B grade pencil demonstrate its usefulness as a passive radiation dosimeter. As a consequence, the findings suggest that graphite-rich materials have the potential to be useful as a low-cost passive radiation dosimeter, with applications in radiotherapy and manufacturing.

High temperature annealing of irradiated nuclear grade graphite

Previous work has shown that the material properties of nuclear grade graphite are substantially affected by the atomic and microstructural changes that occur during neutron-irradiation. The parameters that play a role in these changes are irradiation dose, temperature, graphite composition and the initial microstructure of the graphite. Understanding the details of how these material changes occur and exactly what the changes consists of will enable the prediction of the material property changes as a function of these variables. Other work has shown these atomic level and microstructural changes can be healed or annealed out by raising the irradiated graphite above its irradiation temperature. In this work, experiments were carried out to investigate how the properties of irradiated graphite recover when heated. By showing property recovery as a function of annealing temperature or energy, insight is provided into the type of damage that occurred during neutron-irradiation. The data presented here shows recovery of thermal diffusivity, coefficient of thermal expansion, Young's modulus and electrical resistivity between annealing temperatures of 500 °C and 2380 °C. Graphite grades NBG-18, IG-110 and PCEA are considered that were both stressed and unstressed during irradiation.

Significant reduction of fatigue crack non-propagation limit caused by damage accumulation mode fatigue crack propagation in a precipitation-hardened punched steel plate

Precipitation-hardened steel exhibits specific characteristics due to the punching process that deteriorates its strength. To investigate these characteristics, fatigue tests were conducted with artificial micro defects on the punching processed surface that imitate the flaws caused by the process. The authors found that changes in material properties and the flaws change the fatigue strength properties. Specifically, the fatigue crack extends in the damage accumulation mode, which does not have the non-propagation mechanism and reduces the crack non-propagation limit. Furthermore, the damage accumulation mode fatigue crack propagation changes the fatigue limit's physical meaning from the fatigue crack non-propagation limit to the initiation limit. Finally, processing conditions that improve the fatigue strength characteristics were proposed.

Static and free vibration analysis of functionally graded annular plates using stress-driven nonlocal theory

This study presents analytical and numerical solutions of the bending and the free vibration analysis of a functionally graded annular nanoplate based on the stress-driven nonlocal theory. The nonlocal equation is obtained using the classical plate theory; the power law distribution is assumed to model changes in material properties throughout the thickness. The governing differential equation is analytically solved for different types of edge supports. The explicit analytical solution is obtained in terms of special functions, namely, hypergeometric and Meijer functions. Furthermore, based on the Galerkin technique, a finite element method is introduced to figure out the nanoplate’s flexural deformation and natural frequencies. The analytical and numerical solutions are compared with those available in the literature. The size effects in the nonlocal theory and FGM’s gradient properties have been discussed, considering clamped and simply supported boundary conditions. According to the stress-driven nonlocal model, size-dependent flexural responses of the plate demonstrate stiffening behavior with increasing nonlocal parameters. Which, in general, leads to a decrease in the value of transversal deformation and an increase in natural frequencies when compared to the plate’s local solutions.

One-dimensional large strain electroosmotic consolidation of ultra-soft geomaterials

Electrokinetic (EK) consolidation has been proven to effectively consolidate ultra-soft geomaterials, such as coal washeries, mine tailings, oil sands tailings and so on. The conventional consolidation model based on the small strain theory encountered difficulties with these geomaterials due to continuous changes in material properties during consolidation. This research developed a one-dimensional large strain EK (LSEK-1D) consolidation model for ultra-soft geomaterials. The model is validated using experimental laboratory results regarding settlements and times on mature fine oil sand tailings (MFT), a major environmental challenge for the oil industry in Northern Alberta, Canada. Moreover, the effects of initial sample heights and applied current densities on consolidation times are evaluated. The experimental data on consolidation times of MFT is consistent with the LSEK-1D model. The LSEK-1D model was used to find the scale effect of drainage path on the EK consolidation behaviour of MFT. The model can also be used for other ultra-soft geomaterials and to facilitate the geotechnical engineering design for EK application.

A Sensitivity Analysis of Geometric Parameters of 4D-Printed Bidirectional Shape-Memory Composite in Architectural Façade Design

The 4D-printable two-way shape memory effect (TWSME) is not well known to building engineering and architecture. To better understand the thermo-mechanical complexity of TWSME in building skin design, this paper investigates the parametric uncertainty in basic deformation of a rectangular façade surface module. To this end, a 4D-printed TWSME composite was prototyped by 3D-printing shape memory polymer (SMP, digital elastomers DM9850 and 9885) design with shape memory alloy (SMA) wires (Ni 55.5%-Ti 44.5%wt.) inserted. A simulation-based global sensitivity analysis was conducted on the maximum displacement and force of the composite through the homogenized 1D approximation of bending and material property change in four different phases. It was identified that the simplified simulation well predicted the actual maximum reversible displacement of ~3.5 mm with a sectional area ratio of SMP to SMA of ~105 between 30℃ and 65℃. Our findings indicate that sectional geometry of the bending part (width and height in the rectangle) and the intensity of the SMA pre-strain determined by a degree of fiber bending are the most critical factors to predict the maximum displacement and recovery force of TWSME. The potential building application of thermo-responsive phenomena contributes to extending smart material use in architecture and knowledge in making design decisions in self-shaping climate-adaptive building.

MIST – Mechanical In-situ Stage with Temperature control for X-ray computed tomography

X-ray Computed Tomography (CT) in combination with a tensile/compression stage can deliver great insights in the damage mechanisms of a material. As the material properties change at low and high temperatures, materials may perform differently as they do at room temperature. In this paper, a novel Mechanical In-situ Stage with Temperature control (MIST) for the usage in laboratory CT devices for high resolution - (3 μm)³ - acquisitions is presented. Since the specimen temperature is controlled by air flow, the MIST stage is suitable for testing polymers and allows cooling and heating in one test cycle (-10 °C to +100 °C). The MIST stage is a modification of the CT500 DEBEN tensile/compression stage. It enables mechanical tests that combine the application of force and temperature on a sample at the same time. A technical description of the developed stage is presented. Furthermore, its advantages compared to existing devices are explored and application fields of the MIST are shown.

Study on the effect of modified porous materials on heavy metal remediation in agricultural fields

With the rapid development of modern agriculture, the problem of heavy metal pollution and degradation of soil quality in agricultural soils has become increasingly serious, and the search for efficient, economical and environment-friendly heavy metal passivation materials has become a research hotspot for the solidification and stabilization of heavy metals in agricultural soils. In this paper, we summarize the remediation effect of porous materials on soil heavy metal pollution in view of existing studies, and analyze the changes of porous material properties and the influence on heavy metal remediation ability after modification and aging. Finally, the performance improvement of porous materials and their industrial application in the field of heavy metal pollution remediation are prospected.

Change in the corneal material mechanical property for small incision lenticule extraction surgery.

Purpose: To assess the distribution characteristics and related factors of stress-strain index (SSI) values and discuss changes in biomechanical parameters, including SSI, after small incision lenticule extraction (SMILE) surgery. Methods: This study included 253 patients who underwent SMILE (253 eyes). SSI and other biomechanical parameters were measured using corneal visualization Scheimpflug technology before and 3months after surgery. The data collected included SSI, central corneal thickness (CCT), and eight other dynamic corneal response parameters. The Kolmogorov-Smirnov test, Pearson and partial correlation analyses, and paired-sample t-tests were used for statistical analyses. Results: Both pre-op SSI and ΔSSI follow a normal distribution, while post-op SSI does not follow a normal distribution. The decline in SSI after SMILE surgery was not statistically significant, and the data dispersion of SSI after SMILE surgery was close to that before surgery (p > 0.05). No statistical correlation was noted between SSI values and age and pre-op CCT (all p > 0.05). However, both pre- and post-op SSI values decreased with increasing degree of myopia (all p < 0.05), and weakly correlated with preoperative intraocular pressure and biomechanically corrected intraocular pressure (all p < 0.05). Other biomechanical parameters changed significantly after surgery (all p < 0.001). After SMILE, the magnitude of the deformation at the highest concave, deformation ratio, and integral radius increased significantly (all p < 0.001), while the Ambrosio relational thickness horizontal, stiffness parameter A1, and Corvis biomechanical index decreased significantly (p < 0.001). Conclusion: SSI, which reflects essential corneal material attributes, differs from other corneal biomechanical parameters and remains stable before and after SMILE surgery, and can be used as an indicator to evaluate changes in corneal material properties after SMILE surgery.

Research on Thermal Structure Analysis Technology of Supersonic Missile Rudder

A method of thermal structure analysis is developed for supersonic missile rudder. The method calculates the aerodynamic heat based on Eckert reference enthalpy method, and calculates the temperature field by finite element method. The temperature field is taken as the volume load while calculating the thermal stress gradient and time history. Considering the influence of thermal stress, the natural vibration characteristics such as the mode and vibration frequency with time are obtained. The numerical computation results show that the aerodynamic heat is distributed unevenly across the rudder, such as stagnation point, laminar flow, transition and turbulence. The solid blocks of rudder shaft, longitudinal and transverse wall plates cause local low temperature, and large temperature gradient leads to higher thermal stress. Due to the change of material properties and thermal stress, the natural vibration frequency of the rudder has a significant decrease at sometime. The software of ANSYS was used to calculate and output cloud diagrams. The software of Microsoft Office was used to make curve graphics. The developed APDL command flow is very efficient and portable, which is convenient for complex structural model, and can provide technical support for supersonic missile rudder.

Experimental study on the effects of scale on the static and dynamic behaviour of Glulam and hybrid-Glulam beams

The research and development of timber and timber-hybrid systems depends heavily on the testing of large or full-scale structural components, which is often limited by laboratory space and budget constraints. Testing of small-scale samples is an alternative approach which can avoid costly experimental campaigns; however, little is known about evaluation of serviceability performance measures, including natural frequency and stiffness, which typically govern the design of elements in timber and timber-hybrid long-span systems. Downscale testing of timber is known to be susceptible to changes in material properties with size, the so-called ‘size effect’, but existing research into the size effect in timber focuses on strength rather than serviceability parameters. This work explores the effect of scaling down Glulam and hybrid carbon fibre (CFRP) reinforced Glulam beams, by comparing the dynamic and static performance of beams tested at both full-scale and approximately half scale. Outcomes of this experimental study indicate that serviceability parameters present small variations with scale, whereas strength parameters are affected by size effect in being consistently smaller in the full-scale samples when compared to their small-scale versions. It was also observed that tension-only reinforcement in hybrid CFRP–timber beams appeared to reduce the size effect in both static and dynamic parameters.

A Tiny Flexible Differential Tension Sensor.

Modern applications of Internet of Things (IoT) devices require cheap and effective methods of measurement of physical quantities. Cheap IoT devices with sensor functionalities can detect a lack or excess of substances in everyday life or industry processes. One possible use of tension sensors in IoT applications is the automated replenishment process of fast moving consumer goods (FMCG) on shop shelves or home retail automation that allows for quick ordering of FMCG, where the IoT system is a part of smart packaging. For those reasons, a growing demand for cheap and tiny tension sensors has arisen. In this article, we propose a solution of a small flexible tension sensor fabricated in an amorphous InGaZnO (a-IGZO) thin-film process that can be integrated with other devices, e.g., near-field communications (NFC) or a barcode radio frequency identification (RFID) tag. The sensor was designed to magnify the slight internal changes in material properties caused by mechanical stress. These changes affect the dynamic electrical properties of specially designed inverters for a pair of ring oscillators, in which the frequencies become stress-dependent. In the article, we discuss and explain the approach to the optimum design of a ring oscillator that manifests the highest sensitivity to mechanical stress.

Development of Alkali-Activated Porous Concrete Composition from Slag Waste

In this paper, a porous alkali-activated slag concrete was developed that can be used in the construction sector as a sustainable building material and potentially as an alternative to the aerated concrete products currently on the market. Ferrous slag from the metallurgical industry (Finland) and phosphogypsum from a fertilizer plant (Lithuania) were used as precursors in alkali-activated systems. The addition of hydrogen peroxide and phosphogypsum led to positive changes in the final properties of the test material. Porous concrete based on alkali-activated slag was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) methods. The compressive strength, density, thermal conductivity and porosity of the hardened specimens were evaluated as well. Research is being conducted with the material in question to create a cheap, particularly low-energy demanding building material. This material must have suitable mechanical properties for the structure and, at the same time, suitable thermal conductivity properties. It was determined that this porous concrete had compressive strength in the range of 2.12-7.95 MPa, density from 830 kg/m3 to 1142 kg/m3, and thermal conductivity in the range of 0.0985-0.2618 W/(m·K). The results indicate that the recommended content of phosphogypsum in alkali-activated material is 3-5% due to the optimal distribution of the mechanical and thermal properties and the conductivity. Alkali-activated slag and phosphogypsum material can be used in the manufacture of low-strength insulation blocks and to protect structures from the effects of high temperatures.

Effects of alpha-synuclein and synaptic vesicles on the material properties of synapsin condensates.

Biomolecular condensates can recruit and segregate client molecules and are involved in various physiological processes. The material properties of a biomolecular condensate, as a mesoscale manifestation of intermolecular interactions, are crucial to its biological and pathological functions. Despite emerging reports about the changes in material properties of condensates in disease-related proteins, quantitative studies of the material properties of condensates are still rare. Here, we apply a calibration-free micropipette aspiration (MPA) assay to quantify the surface tension and viscosity of synapsin condensates. Furthermore, we investigated the effect of alpha-synuclein and synaptic vesicles (SVs) on the material properties of synapsin condensate. The results suggest that the recruitment of alpha-synuclein will increase the viscosity of synapsin condensate, and indicate the potential effects of SVs in mediating the material properties of synapsin condensates. Synapsin condensates are known to be essential for the formation of SV clusters. Therefore, our findings will help understand the regulation of SV dynamics during neurotransmission.

On the Sensitivity of a Tool–Workpiece Thermocouple to Chemical Composition and Microstructure

Meeting the increasing demands on part quality and profitability of manufacturing processes despite difficult-to-machine materials is only possible with a deep understanding of the process. Herein, knowledge about the process temperature is of critical importance since it affects the material properties, such as hardness or forming behavior, as well as the chemical and physical interactions between the tool, workpiece, and lubricant. A proven thermoelectric method of temperature measurement in machining, forming, and blanking is a tool–workpiece thermocouple. Herein, instantaneous measurement of the temperature development is allowed in this setup during the manufacturing process in situ at the contact area of the tool and workpiece. The accuracy of this method is dependent on the calibration of the thermocouple, for which the Seebeck coefficients of the tool and workpiece material have to be determined. Usually, material samples from different batches are used for this purpose, although the resulting measurement errors due to slight changes in material properties are hardly known. Herein, the effects of small changes in the chemical composition and the transformation of the crystal lattice due to hardening on the Seebeck coefficient are investigated for the first time to allow precise quantification of the measurement error resulting from the calibration process.

Effects of plaster choice on conservation of the original acoustical character of historical mosques

The study aims to contribute acoustic characteristics of two monumental mosques in Western Anatolia: focusing on the change of material properties of the prayer hall and its effects on the perceived acoustical environment during history. Preserving the authentic auditory environments of historical mosques has great importance. Because the acoustical perception of the prayer hall affects users as much as their visual perception. Field measurements and acoustical simulations were held in two historical mosques with similar room volumes but different dome combinations to compare the present and probable original acoustical environments. The values of T30, EDT and STI are investigated by focusing on the change of plaster properties during restoration works. It is found that the original mortars could be differentiated for both cases and they might sound very different when the time they were first built. Acoustic documentation of such important historical monuments of Anatolia is quite a good contribution to the field of archaeoacoustics and historical conservation. However, the study focused on the change of material properties. The findings of the paper can raise the question; of whether it is possible to comment on the originality of materials of a historical space by measuring its current acoustical character.

Temperature Patterns in TSA for Different Frequencies and Material Properties: A FEM Approach

Thermography techniques are gaining popularity in structural integrity monitoring and analysis of mechanical systems’ behavior because they are contactless, non-intrusive, rapidly deployable, applicable to structures under harsh environments, and can be performed on-site. More so, the use of image optical techniques has grown quickly over the past several decades due to the progress in the digital camera, infrared camera, and computational power. This work focuses on thermoelastic stress analysis (TSA), and its main goal was to create a computational model based on the finite element method that simulates this technique, to evaluate and quantify how the changes in material properties, including orthotropic, affect the results of the stresses obtained with TSA. The numeric simulations were performed for two samples, compact and single lap joints. when comparing the numeric model developed with previous laboratory tests, the results showed a good representation of the stress test for both samples. The created model is applicable to various materials, including fiber-reinforced composites. This work also highlights the need to perform laboratory tests using anisotropic materials to better understand the TSA potential and improve the developed models.