Effect Of Internal Stresses Research Articles

Daily external stress, internal stress, dyadic coping, and relationship functioning of Turkish couples during the COVID-19: A daily diary study.

Stressors arising from the current COVID-19 pandemic have pernicious effects on relational functioning. However, the systemic transactional model (STM) addresses the buffering role of dyadic coping in couples' relationships. Therefore, the current study aimed to examine the possible buffering role of dyadic coping and investigate the negative consequences of external stressors related to the COVID-19 pandemic and internal stressors on relationship satisfaction and intimacy on within- and between-person levels. Data were collected from 100 couples through daily diary questions over 14 consecutive days. The mean age for females was 32.45years (SD=8.11), and for males, it was 34.79years (SD=8.79). The findings showed several significant within-person moderation effects. Specifically, simple slope analysis revealed that the associations between internal stress and relationship satisfaction, and intimacy were positive for both partners who reported particularly more dyadic coping on a given day. Conversely, interaction effect of dyadic coping with external stress has not been found significant on within-person level. Between-person effects revealed that dyadic coping buffers the negative association between external stress and relational outcomes and the negative effect of internal stress. The current study expanded the literature of the STM of dyadic coping within the context of an acute external crisis. In line with STM predictions, couples may benefit from interventions focused on enhancing coping strategies to navigate major and minor stressors, especially during significant life challenges, thereby maintaining high relationship quality.

Morphological and Dimensional Evolution of Nanosized Amorphous Silicon Nitride in α-Fe: Diffusional and Elastic Effects

We present a detailed analysis based on both experimental and 3D modelling approaches of the unique silicon nitride precipitation sequence observed in ferritic Fe-Si alloys upon nitriding. At 570 °C, Si3N4 silicon nitride was shown to form as an amorphous phase into α-Fe ferrite matrix, which is morphologically unstable over time. Precipitates nucleated with a spheroidal shape, then developed a cuboidal shape for intermediate sizes and octapod-like morphology for a longer time. Using transmission electron microscopy, we show that the transition between spheroid and cuboid morphology depended on particle size and resulted from competition between interfacial energy and elastic strain energy. The resulting morphology was then shown to be a cuboid shape whose faces were always parallel to the {100} planes of the α-Fe; the <100> directions of the matrix corresponded to the elastically soft directions. There was a critical size of around 45 nm for which the transition between the cuboid shape and the octapod-like morphology took place. This was characterised by a transformation of quasi-flat facets into concave ones and the development of lobes in the <111> directions of the bcc crystal. To better assess the kinetic effects of diffusion fields and internal stresses on the morphological instability observed, an original 3D model that explicitly coupled phase transformations and mechanical fields was developed and applied. The latter, validated on the basis of model cases, was shown to be able to describe the time-evolution of both chemical and mechanical fields and their interactions in diffusive mass transport. Using a model system, it was shown that the concentration field around the precipitates and the internal stresses played opposing roles in the cuboid to octapod-like morphological instability. This work gives some clarification regarding the morphological evolution of amorphous Si3N4 precipitates, an important point for controlling the mechanical properties of nitrogen steels.

Exploring the temperature dependence of magnetic properties and magnetoimpedance effect in Co-rich microwires

We studied the temperature dependence of the magnetic properties and giant magnetoimpedance, GMI, effect in as-prepared and annealed Co69.2Fe3.6Ni1B12.5Si11Mo1.5C1.2 glass-coated microwires with nearly-zero magnetostriction. Substantial changes in the GMI ratio, ΔZ/Z, value and magnetic field, H, dependence, and in the hysteresis loops upon heating were observed. The modification in the hysteresis loop shape upon heating correlates with a change in the ΔZ/Z (H) dependencies. In as-prepared and most of the heat treated samples the hysteresis loop transformation from inclined to squared upon heating correlates with the change in ΔZ/Z(H) dependencies from double-peak to single-peak. However, the stress-annealed at 118 MPa samples present better thermal stability of the ΔZ/Z(H) dependencies and hysteresis loops. In all the studied samples an increase in the GMI ratio at 300 °C was observed. The origin of the observed temperature dependences is discussed in terms of the Hopkinson effect, temperature dependence and relaxation of internal stresses, induced magnetic anisotropy, and temperature dependence of the magnetostriction coefficient.

Understanding the torsional mechanical behavior of twisting carbon nanotube ribbon with different boundary conditions

Twisting can generate internal stress and store torsional energy, which is widely used as actuators and energy harvesters in electronic and biomedical fields. However, uncovering the effect of internal stress remains unclear. Herein, the experimental and theoretical mechanical model of the twisted ribbon with different boundary conditions was derived and analyzed. The dynamic experimental results indicate that the polymer inclines to constrain the unraveling process of carbon nanotube fiber. Then the elastic/plastic theoretical equations reveal that the internal stress gradually increases as the twisted angle, and the simulated internal stress agrees well with the theoretical results. The simulation results also indicate that the twisting-induced deformation and failure behavior of twisted ribbons are affected by the strain-rate sensitivity of the matrix and the loading velocity. Then, the releasing of the stored energy for twisted ribbons with different boundary conditions demonstrates the contraction and repulsion behaviors. This work investigating the mechanical behavior of twisted ribbons could provide a better guideline for designing twisted actuators with high reliability.

Formation of Globally Uniaxial Strain in He+ Implanted Silicon-on-Insulator Wafers Based on the Size Effect of Internal Stress of Strip SiN Films

Formation of Globally Uniaxial Strain in He+ Implanted Silicon-on-Insulator Wafers Based on the Size Effect of Internal Stress of Strip SiN Films

Impacts of nanofiller shapes on the interface confinement effect in polymer nanocomposites

Shape effect of nanofillers (NFs) on the properties of nanocomposites has attracted considerable attention in recent research. The present study aims to examine how NF shapes influence the confinement effect of polymer-NF interface on the physical properties of nearby polymer (the interphase). Herein molecular dynamics simulations are performed to capture the shift of interphase properties when NFs change from nanosphere to nanocylinder and nanofilm geometry. A stress analysis is then carried out in the interphase to identify a key parameter for characterizing the stress-property coupling and revealing the pathway of the NF shapes to impact the interphase properties. It is shown that the peak hydrostatic stress σhyd quantifies the effect of internal stresses on the properties of the interphase. Specifically, the shape transition considered can substantially enhance the peak σhyd by flattening the stress space in the interphase without largely affecting the polymer-NF interaction. Increased peak σhyd in turn upshifts the interphase properties and thus, leads to the coupling between the NF shapes and interface confinement effect.

Mechanism of ratcheting deformation of HSLA steel: Effects of internal stresses and dislocation density

The objective of this study is to elucidate the mechanism of ratcheting deformation of HSLA steel in relation to the evolution of internal stresses i.e. effective stress (σef) and backstress (σb) associated with the generation of dislocations during asymmetric cyclic loading. Effective and back stresses are calculated from the stress-strain hysteresis loops and dislocation density is estimated from the X-ray diffraction technique. The results exhibit an increase in the accumulation of ratcheting strain associated with a sharp reduction in fatigue life by the increment in stresses. A continuous cyclic softening until the final failure is observed for all the ratcheting tests. It is noticed that the effect of stress amplitude is more prominent than the mean stress for controlling cyclic softening, which is evidenced by the evolution of effective stress and backstress in association with dislocation density. Additionally, transmission electron microscopic images are used to correlate strain conditions and substructural patterns.

Improving the high-temperature oxidation resistance of CrN coating by gradient deposition considering internal stress effects

In this study, two different CrN coatings were deposited on the surface of Zr-4 via a multi-arc ion-plating method using gradient and non-gradient deposition processes. The effects of two deposition processes on the high-temperature oxidation resistance and internal stress of the coatings were investigated. The microstructure and phase structure of the coatings were characterized by scanning electron microscopy, X-ray diffraction (XRD), and energy dispersive spectrometry. The high-temperature oxidation resistance of the specimens was investigated by performing thermal shock experiments and simulated loss-of-coolant accident high-temperature steam oxidation experiments. The residual stresses of both coatings during deposition were determined by XRD analysis. In addition, the thermal stresses of both coatings during the high-temperature oxidation tests were modeled and calculated. Under long-term high-temperature oxidation conditions, the gradient-deposited CrN coating exhibited improved high-temperature oxidation resistance performance than that exhibited by non-gradient-deposited CrN coating. In addition, the residual stresses of gradient-deposited CrN coating during deposition and thermal stresses during high-temperature oxidation were significantly lower than those of the non-gradient-deposited CrN coating. The results obtained herein confirm the promising potential of gradient-deposited CrN coating as an accident-tolerant fuel cladding material.

Study on induction hardening performance of 34CrNi3MoA steel crankshaft

The evolution of the temperature field, microstructure field, and residual stress field of a 34CrNi3MoA steel marine diesel engine crankshaft during medium-frequency induction hardening was studied based on an electromagnetic-thermal-transformation-stress coupled numerical model, which considers the effect of internal stress induced by transformation induced plasticity on residual stress. Using the equal conversion rate method, the austenitizing region of the crankshaft was determined during the induction heating stage. In the quenching stage, the parameters of the phase transformation model are derived from the continuous heating expansion curve and the continuous cooling transformation curve, and the phase transformation kinetics equation is used to analyze the phase transformation process of the crankshaft. The results indicate that extending the heating time can enhance the uniformity of the surface temperature of the crankshaft and the thickness of the hardened layer. The simulation results are validated by measurements of hardened layer, hardness and residual stress, and the simulation results are in good agreement with the experimental results.

Study of Interfacial Adhesion and Re-Ir Alloy Coating in Chalcogenide Glass Molding.

Precision glass molding (PGM) has become an efficacious technique to fabricate high-precision optics. Chalcogenide (ChG) glass is increasingly used in thermal imaging, night vision, etc., because of its excellent infrared optical properties. Nevertheless, glass-mold interfacial adhesion has emerged as a pivotal issue within the PGM process. The interfacial adhesion during PGM has the potential to significantly undermine the performance of molded optics and reduce the longevity of molds. It is important to investigate interfacial adhesion behaviors in the PGM. In this study, the interfacial adhesion mechanism between ChG glass and the nickel-phosphorus (Ni-P) mold is analyzed using the cylindrical compression test. The effect of ChG glass internal stress on physical adhesion is investigated by finite element method (FEM) simulation. The spherical preform is proven to be capable of reducing the stress concentration and preventing physical adhesion. More importantly, a rhenium-iridium (Re-Ir) alloy coating is deposited on the Ni-P mold surface by ion sputtering to prevent atomic diffusion and resolve the problem of chemical adhesion. Finally, ChG glass microstructures with high accuracy are fabricated using the spherical ChG glass preform and the Re-Ir-coated Ni-P mold by PGM.

Nanoscale morphology tailoring in plasma deposited CN x layers

Magnetron discharge plasma was applied for the synthesis of CN x thin layers using methane and nitrogen gas precursors. The incorporation of nitrogen in the carbon network resulted in the dramatic evolution of growth morphology: from a ‘buried’ porous layer observed at low nitrogen incorporation to aligned bundles of nanorods grown perpendicular to the substrate surface at maximum discharge power and nitrogen flow. The films deposited at the low discharge power and high nitrogen incorporation exhibited a mesoporous sponge-like morphology after vacuum annealing. Relevant physical mechanisms responsible for the formation of nano- and mesoshaped morphology are discussed in terms of the effects of internal mechanical stresses and plasma etching. In addition, the sensing properties of the sponge-like layer were preliminarily examined in water vapor and ammonia ambients. The CN x films showed enhanced sensitivity to ammonia and reverse electrical response to moisture in comparison with a nitrogen-free nanoporous carbon film, which were assigned to modification of the electronic properties of the nitridated surface.

Durability of low-carbon geopolymer mortar: Different responses to cryogenic attack caused by water content and freeze-thaw mediums

Durability is an important attribute that needs to be focused on during the life span of low-carbon geopolymer mortar (LCGM). The influence of water content (0.00%, 4.91%, and 6.46%) and freeze-thaw medium (air or water) on the performance of LCGM subjected to cryogenic attack up to −170 °C is evaluated by mass change, compressive strength, and microstructure. The results reveal that only water-saturated LCGMs subjected to air freeze-thaw medium experienced a mass loss of 0.66% and the other specimens exhibited different degrees of mass increase by up to 0.27%. Oven-dried and air-dried LCGMs in air freeze-thaw medium experienced a slight increase of compressive strength by about 4.0%. However, water-saturated LCGMs in the same condition experienced a compressive strength decrease of about 9.7%. Additionally, LCGMs exhibited an obvious compressive strength decrease of up to 24.3% in water freeze-thaw medium. The change of microstructure is responsible for the increase or decrease of compressive strength. The water transport and water-ice-water phase transition are the intrinsic motivation for LCGMs to exhibit different responses to cryogenic attack. The exposure of LCGMs to water freeze-thaw medium cryogenic attack exhibited the most severe performance deterioration, which is associated with the couple effect of internal frost-heave stress induced by phase transition and external frost-heave stress induced by ice contraction.

Loss analysis of magnetization annealed amorphous alloy replacement stator teeth

With the development of electric motors, high speed and high efficiency have become the new development trend. Therefore, reducing the iron loss of motors has become the focus of academia and industry. Amorphous alloys are gradually being used in high speed motors by virtue of their low loss characteristics at high frequencies. Amorphous alloys generate large internal stresses during the manufacturing process, and annealing is usually required to eliminate the effect of internal stresses on magnetism. Amorphous transformer cores are usually annealed by applying a magnetic field in the direction of the magnetic circuit to improve the magnetic domain state, increase the saturation density in that direction, and reduce iron loss. Since the magnetic field of the motor stator teeth is pulsating, and amorphous annealed under longitudinal magnetic field (AALM) has the most performance along the direction of the annealed magnetic field. Therefore, in this paper, the magnetic properties of AALM, annealed amorphous (AA), and unannealed amorphous (UA) are tested to prove the advantages of the material, and then AALM is spliced as the tooth of the motor. The advantages of this material in the motor species are further demonstrated by designing a comparative simulation scheme in the longitudinal direction (same material with different structure) and in the transverse direction (same structure with different material).

Internal stress effects on the piezoelectric properties of Pb(Zr,Ti)O3 superlattice thin films grown on Si substrates

Artificial superlattice thin films of lead zirconate titanate (PZT) were epitaxially grown on silicon substrates, and the influence of superlattice strain on their piezoelectric properties was investigated. The c-axis oriented PZT superlattice thin film consists of two different PZT layers, Pb(Zr0.65Ti0.35)O3 (PZT-65) and Pb(ZrxTi1−x)O3 (PZT-X: x = X/100 = 0.3–0.9), with a 4 nm period. Satellite peaks were clearly observed in x-ray diffraction patterns, and cross-sectional composition measurements confirmed the superlattice structure with good interfaces, showing an alternate change in Zr and Ti compositions. Ferroelectric properties varied significantly depending on the PZT-X composition, and in particular, the PZT-65/PZT-30 superlattice thin film showed nearly the same ferroelectricity as the tetragonal phase under a large compressive strain of PZT-65 from the PZT-30 layer. For the PZT-65/PZT-X (X = 30–58) superlattice thin films, the PZT-65 layers received a compressive strain, and a relatively large piezoelectric coefficient, which did not depend on the PZT-X composition, was obtained. However, a decrease in piezoelectricity was observed in PZT-65/PZT-X (X = 70 and 90), where the PZT-65 layers experienced tensile strain. This result indicates that the piezoelectric properties of PZT superlattice thin films can be controlled by the interlayer strain.

A further step toward the understanding of phase transformation mechanism between 10 wt. % dysprosia stabilized zirconia powders and ceramics

In this study, 10 wt. % dysprosia stabilized zirconia (10DySZ) ceramics were prepared by pressing and pretreatment method. The phase and structural evolution as well as the phase transformation behaviors of 10DySZ ceramics were investigated. Results show that the 10DySZ ceramics have the same phase composition as that of powders in final products. Differently, an asynchronous nucleation behavior of m- and c-DySZ can be recognized, the t→m martensite transformation was inhibited significantly during the incubation period of phase transformation. The phase transformation behaviors of 10DySZ ceramics were also confirmed to be followed the new phase nucleation and growth theory. In the early stage, the inhibition of phase transformation can be attributed to the comprehensive influence from steric hindrance, internal stress and critical size effect. However, in the later phase transformation explosion period, the rapid growth of new phases as well as the increased internal stress dominated the acceleration of phase transformation of 10DySZ ceramics.

Atomistic study of internal stress effect on scratching behavior in titanium single crystal

The internal stress effect on the scratching behavior in titanium single crystal is investigated by molecular dynamics simulations. It is introduced by applying the compressive/tensile pre-strain in this work. The friction force in the model with compressive pre-strain is higher than that with tensile pre-strain, which is related to the atomistic spacing and the distribution of pile-up. The dislocation mechanism is systematically illustrated that three types of <a> dislocations of edge dislocation loop, prism edge dislocation and screw dislocation dominate the plastic deformation. The coupling of dislocation loop and screw dislocation in the model with tensile pre-strain causes much more defects to remain in the matrix. However, when the model is applied by small compressive pre-strain, the dislocations left in the matrix are obviously decreased, reducing the internal crystal damage. Overall, the compressive/tensile internal stress has a distinguishing effect on the scratching behavior, which can be used for altering the friction and wear property of titanium.

Preparation and magnetic properties of Co2-based Heusler alloy glass-coated microwires with high Curie temperature

In this article, we studied the effect of annealing (600 °C for 1 h) and the applied magnetic field from 50 Oe to 20 kOe of Co2FeSi glass-coated microwires with ordered L21 structure prepared by Taylor–Ulitovsky technique on the magnetic behavior. The as-prepared and annealed samples show a ferromagnetic behavior at the range of measuring temperature (5 to 400 K) and magnetic field (50 Oe to 20 kOe). M–H loops of as prepared sample do not show a squared shape. Meanwhile, perfectly squared hysteresis loops have detected for the annealed sample. In addition, annealed sample shows high magnetization M/M5K ratio, coercivity, and anisotropy field, as-compared to the as-prepared one. The annealed sample shows considerable irreversibility when the magnetic behavior changes with temperature upon the applied magnetic field at 50 and 200 Oe. Such irreversibility does not found in the as-prepared sample measured at the same magnetic field due to mixed amorphous and crystalline structure. By increasing the external magnetic field higher than 200 Oe and up to 20 kOe a gradual changing in the magnetic behavior has been detected where the irreversibility disappeared at applying magnetic field about 1 kOe and the magnetic behavior is totally change by increasing the external magnetic field up to the maximum 20 kOe. The difference in the magnetic behavior of the annealed glass-coated Co2FeSi glass-coated microwires indicates the effect of internal stresses induced by the presence of the glass-coating and the annealing-induced recrystallization.

The effect of internal stress on the photocatalytic performance of the Zn doped BiOBr photocatalyst for tetracycline degradation

BackgroundThe serious environmental pollution caused by the massive deposition of antibiotics in the environment has aroused widespread concern. MethodsIn this work, stress engineering is used to modulate the visible-light-driven photodegradation of tetracycline (TC) by Zn-doped BiOBr flower microspheres, which were successfully prepared by a solvothermal method. Significant findingsCompared with pure BiOBr, zinc-doped BiOBr significantly improved the visible light catalytic degradation efficiency of TC. When increasing the content of Zn, a local n-type zone gradually formed in the p-type BiOBr matrix to form pseudo-heterojunction with lateral heterojunction properties, and the best photocatalytic performance is 12%Zn-BiOBr. In addition, the role of active species in TC photodegradation was evaluated by adding different trapping agents. The association with internal stress and photodegradation performance was established, and the mechanism to enhance the photodegradation performance under visible light irradiation of Zn-doped BiOBr photocatalysts was proposed.

Study of diffusion processes in contact areas of thermocouples with metals

Diffusion processes on the contact areas of the metal-solder-semiconductor system are experimentally studied in this work. Diffusion coefficients, activation energies and pre-exponential factors in samples commutated with solders based on Pb-Sb are determined. It has been established that lead-based solder has a significantly higher inertness to thermoelectric materials. Humans are currently facing complex challenges such as rising energy costs, pollution and global warming. To reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their ability to convert thermal energy directly into electricity through the Seebeck effect. Due to the unique advantages, they present, thermoelectric systems have emerged over the past decade as a promising alternative among other technologies for the production of clean energy. [1-11]. Switching is the most time-consuming and responsible operation in the manufacture of thermoelectric modules. In them, which include a significant number of junctions, failures most often occur due to broken contacts [2-8]. To prevent the harmful effects of internal mechanical stresses, in the manufacture of thermoelectric batteries, it is necessary to use a damping layer between the branch and the connecting plate [3-14]. The damping layer is made of a material with sufficient plasticity and low ohmic resistance. It is usually made from lead. The results of the research showed the advantages of using a single -wire technology for soldering with Pb - Sb eutectic solder using an anti -diffusion layer of chemically deposited nickel. In this case, the eutectic solder Pb - Sb in the contact simultaneously performs the role of a damper and a switching solder.

Nonlinear oscillations of a rod with residual stress in the presence of contact dry friction

Wave processes are studied in an elastic rod interacting with its environment according to the law of dry friction. Oscillations of the system at residual stresses are emerged under the influence of instantaneous unloading. Analytical solution of the partial differential equation of hyperbolic type with a nonlinear mechanism of energy dissipation is obtained. Thus, it makes it possible to describe the oscillatory process at various loading parameters of the system for an arbitrary section of the rod. The property, that for the class of problems under consideration dry friction does not change the natural frequency of the system, is shown additionally. The problem can be considered as a model for describing dynamic processes in rocks under the effect of internal stresses. Results of the modeling problem allow us to conclude: if we consider that rocks resist differently to tension and compression, such as resistance to tension is less than compression’ resistance, it is obvious that in the case of relatively rapid unloading of the system, the residual compressions will create stresses that correspond to the first maximal displacements of the end section, and that exceed the limit of tensile strength as well. In this case, the edge sections undergo the brittle fracture that can be sustained by the tensile stresses of the subsequent maximum displacements.