Plastic Phase Research Articles

Effect of oil and surfactants on changes in some physical properties of soils

The paper shows that oil pollution of gray forest and soddy-podzolic soils led to a decrease in capillary water capacity, plasticity and solid phase of soils. As a result of the introduction of the nonionic surfactant tween-80 into the oil-contaminated soil, these indicators were partially restored, but their values remained lower than in soil samples subjected to oil treatment. The obtained materials allow us to speak about the fundamental possibility of using surfactants for the remediation of oil-contaminated soils.

A Theoretical and Experimental Investigation on the Fracture Mechanism of Center-Symmetric Closed Crack in Compacted Clay under Compression–Shear Loading

In this study, a modified maximum tangential stress criterion by considering T-stress and uniaxial compression tests have been utilized to theoretically and experimentally reveal the fracture initiation mechanism of a center-symmetric closed crack in compacted clay. The results show that wing cracks occur in the linear elastic phase of the stress-strain curve. In the plastic phase of the stress-strain curve, the wing cracks extend gradually and the shear cracks occur. The crack initiation stress and peak stress of compacted clay first decrease with the rise in pre-crack inclination angle (β = 0°–40°), and then increase with the rise in pre-crack inclination angle (β = 50°–90°). When the pre-crack inclination angle is relatively small or large (β ≤ 10° or β ≥ 70°), the crack type is mainly tension cracks. Secondary shear cracks occur when the pre-crack inclination angle is 10°–80°. When the dimensionless crack length is larger than 0.35, the crack types include wing-type tension cracks and secondary shear cracks. The experimental results were compared with the theoretical values. It was found that the critical size rc of compacted clay under compression-shear loading was 0.75 mm, smaller than the value calculated by the empirical formula (12 mm). The MTS criterion considering T-stress can be used to predict the compression-shear fracture behavior of compacted clay.

Comparative Analysis of Three Constitutive Models and Microstructure Characteristics of Nb521 during Hot Deformation

This study presents an exploration of the flow stress constitutive model and the deformation mechanism of Nb521, both critical for its practical application. Hot-compression experiments were performed on Nb521 at temperatures ranging from 1523 K to 1723 K and strain rates ranging from 0.01 to 10 s−1. In addition, the microstructure evolution was concurrently studied through scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). The stress–strain behaviour of Nb521 was assessed, leading to the development of three constitutive models: the Johnson–Cook model, the modified Johnson–Cook model and the Arrhenius model. In the course of the deformation process, it is consistently observed that the hardening effect surpasses the softening effect during the plastic phase, with no observable occurrence of a steady-state phase. The modified Johnson–Cook model offers superior predictive accuracy. Both grain elongation and torsion are the main deformation mechanisms of Nb521 and specific texture forms during stretching. This study also reveals that fractures at both room temperature and high temperatures are brittle in nature. The elucidation of the constitutive model and underlying deformation mechanisms in this study offers indispensable insights into the hot-deformation behaviour of Nb521.

Benign esophageal stricture model construction and mechanism exploration

Esophageal stricture is a debilitating condition that negatively impacts patients' quality of life after undergoing endoscopic mucosal resection (EMR). Despite its significance, this disease remains underexplored due to the lack of a stable animal model. Under direct visualization with choledochoscopy, we retrogradely damaged the esophageal mucosal layer through the gastrostomy to create a rat model of esophageal stricture. The development of histological defects in the mucosal layer was assessed over a 2-week period after model induction. Then the models were evaluated using X-ray barium radiography, Hematoxylin–Eosin, Masson’s trichrome, Sirius red, and Victoria blue staining, multiphoton microscopic imaging. Additionally, the molecular mechanisms of esophageal stricture were explored by conducting RNA transcriptome sequencing, PCR, immunohistochemistry, and immunofluorescence staining. We successfully established fifteen rat models of esophageal stricture by injuring the mucosal layer. In the model group, the mucosal defect initially occurs and subsequently repaired. The epithelium was absent and was plastically remodeled by collagen during the acute inflammatory phase (Day 1), proliferation phase (Day 7), anaphase of proliferation (Day 10), and plastic remodeling phase (Day 14). We observed increased expression of COL1A1, acta2, FGF, IL-1, and TGF-β1 pathway in the model group. We established a highly repeatable rat model of esophageal stricture, and our results suggest that the mucosal defect of the esophagus is a critical factor in esophageal stricture development, rather than damage to the muscularis layer. We identified Atp4b, cyp1a2, and gstk1 as potential targets for treating esophageal stricture, while the TGF-β pathway was found to play an important role in its development.

Excellent strength and toughness and multifunctional protein-based adhesive produced by polyether block sulfuretted polyamidoamine-epichlorohydrin via a dual-crosslinking strategy

Developing high-temperature soy-protein meal (HSM)-based adhesives equipped with excellent bonding strength, superb toughness, and versatility is challengeable due to their inherent high hydrophilicity and agglomeration. Though conventional chemical modifications can enhance the bonding strengths of HSM-based adhesives, few strategies can achieve simultaneous enhancement and toughening. To achieve this target, the polyether block sulfuretted polyamidoamine-epichlorohydrin (SPE-PEDE) was innovatively self-prepared. The SPE-PEDE can not only form a stiff chemical bond crosslinking network through the active azetidinium groups and disulfide bonds in sulfuretted polyamidoamine-epichlorohydrin (SPE) segment, but also can provide a plasticizer phase (PEDE) which can trigger dynamic hydrogen bonding and promote stress transfer among the adhesive system. Thus, forming an efficient dual-network strengthening and toughening system inside adhesives. The improved toughness of the HSM/SPE-PEDE15% sample prepared herein achieved a 306.31% compared to the neat sample, and it bonded plywood obtained a dry bonding strength of 2.90 MPa, a wet bonding strength of 1.11 MPa, and a pre-pressing bonding strength of 760 kPa, which were 82.39%, 258.06%, and 208.94%, respectively higher than the HSM sample. Besides, the modified adhesives also exhibit high solid contents, low moisture absorption, excellent mildew resistance, and antibacterial activity, thus showing the potential to promote the industrial production of HSM-based adhesives.

Deployment analysis of membranes with creases using a nonlinear torsion spring model

Membranes have been widely applied in spacecrafts, such as solar sails and deployable antenna structures, due to their light weight and high compact ratio. The geometric profile of deployed membranes has an important impact on the performance of a membrane-based spacecraft, which should be accurately predicted during the deployment process. However, some observable dynamic deployment characteristics of membranes are difficult to be simulated accurately. In this paper, an equivalent torsion spring model for the membrane crease is proposed and derived to accurately describe the complex deployment process of the membrane. The elastic and plastic phases of the equivalent spring are both considered and derived in this model. Based on this method, the experimentally-observed spring-back position and the corresponding torque of the membrane can be quantitatively predicted. Combining the equivalent torsion spring model with the finite element software, the deployment processes of a single-fold and a Miura-fold are simulated and compared with the experimental results, showing a good agreement. Finally, the deployment process of a 3-axis stabilized solar sail is simulated using this method.

HIGH-FAT DIET IN THE PERI-PUBERTAL PERIOD PROGRAMS CARDIOVASCULAR DYSFUNCTION IN ADULT MALE WISTAR RATS

Stress during peri-pubertal period can determine no communicable disease in adulthood. Thisstudy aims to evaluate whether high fat diet exposure during adolescence induces long-termcardiovascular dysfunctions. The ethic committee approved the animal protocol nº1527130815. Wistar rats, 30-days-old, were feed to a high fat diet (HFD, 35% lard w/w) until60-days-old, then fed a normal fat diet for a further 60 days dietary recovery. Control animalsate normal fat diet throughout life. Body weight and food intake were evaluated weekly. AtPN120, cardiovascular and histological analysis were done. Student´s T test were applied.PN120, feed by HFD during adolescence increase systolic and diastolic blood pressure (upper10% and 4%, respectively; p <0.05 and p <0.005). Using ganglionic blocker, hexamethonium(30 mg/kg, iv), blood pressure was greater in the HFD rats (26%; p <0,01). Increasedperivascular and interstitial fibrosis (42% and 62% respectively; p<0,01 and p<0,001) wereobserved in the HFD rats, accompanied by a left ventricular hypertrophy (29%; p<0,001).Rats who were fed with HFD during peri-pubertal age present hypertension, hyperactivity ofthe vascular sympathetic nervous system and morphological cardiac alterations in adulthood.Current study remarks that adolescence is a plastic phase which permit to programs diseaseslater in life.

Dipolar relaxation, conductivity, and polar order in AgCN.

By using dielectric spectroscopy in a broad range of temperatures and frequencies, we have investigated dipolar relaxations, the dc conductivity, and the possible occurrence of polar order in AgCN. The conductivity contributions dominate the dielectric response at elevated temperatures and low frequencies, most likely arising from the mobility of the small silver ions. In addition, we observe the dipolar relaxation dynamics of the dumbbell-shaped CN- ions, whose temperature dependence follows the Arrhenius behavior with a hindering barrier of 0.59eV (57 kJ/mol). It correlates well with a systematic development of the relaxation dynamics with the cation radius, previously observed in various alkali cyanides. By comparison with the latter, we conclude that AgCN does not exhibit a plastic high-temperature phase with free rotation of the cyanide ions. Instead, our results indicate that a phase with quadrupolar order, revealing dipolar head-to-tail disorder of the CN- ions, exists at elevated temperatures up to the decomposition temperature, which crosses over to long-range polar order of the CN dipole moments below about 475K. Dipole ordering was also reported for NaCN and KCN, and a comparison with these systems suggests a critical relaxation rate of 105-107Hz, marking the onset of dipolar order in the cyanides. The detected relaxation dynamics in this order-disorder type polar state points to glasslike freezing below about 195K of a fraction of non-ordered CN dipoles.

The early stage of adult ocular dominance plasticity revealed by near-infrared optical imaging of intrinsic signals

Long term monocular deprivation is considered to be necessary for the induction of significant ocular dominance plasticity in the adult visual cortex. In this study, we subjected adult mice to monocular deprivation for various durations and screened for changes in ocular dominance using dual-wavelength intrinsic signal optical imaging. We found that short-term deprivation was sufficient to cause a shift in ocular dominance and that these early-stage changes were detected only by near-infrared illumination. In addition, single-unit recordings showed that these early-stage changes primarily occurred in deep cortical layers. This early-stage ocular dominance shift was abolished by the blockade of NMDA receptors. In summary, our findings reveal an early phase of adult ocular dominance plasticity and provide the dynamics of adult plasticity.

On the low-cycle fatigue behavior of a multi-phase high entropy alloy with enhanced plasticity

A multi-phase non-equiatomic FeCrNiMnCo high entropy alloy (HEA) was fabricated using vacuum induction melting. Thermo-mechanical treatments consisting of cold rolling and annealing at 750 °C and 850 °C were employed to improve the mechanical properties of the HEA in focus. Tensile experiments revealed that yield strength and ultimate tensile strength levels can be enhanced significantly after thermo-mechanical processing (TMP). At the same time, ductility remains at an adequate level. Strain-controlled low-cycle fatigue (LCF) experiments were carried out in order to assess the mechanical properties of this HEA under cyclic loading conditions. At the same strain amplitude, the stress levels of the processed samples were considerably higher than that of the as-received counterpart. Similarly, fatigue lives of the former could surpass the base condition at the strain amplitudes of 0.2% and 0.4%; however, at the higher strain amplitudes, cyclic softening was observed. Electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) results revealed that phase transformation from face-centered cubic (FCC) to body-centered cubic (BCC/B2) took place at a higher occurrence with increasing strain amplitude (0.2% to 0.6%). Furthermore, transmission electron microscopy (TEM) studies confirm that upon tensile deformation additional plasticity mechanisms, i.e., deformation twinning and phase transformation, contribute to the overall mechanical behavior of the multi-phase HEA.

Effect of “pseudorotation” on cyclopentane isochoric thermal conductivity

The isochoric heat conductivity in plastic phases I and II solid cyclopentane(C5H10) is investigated. Various temperature dependents of heat conductivity indicate various characteristics of a rotary motion of molecules in these phases. In phase II, the motion of the molecules has mainly character of libration, and in phase I, is close to the hindered rotation. In a phase I of cyclopentane an increase in the slope of isochoric heat conductivity with the growth of the density of samples is revealed. Such behavior of heat conductivity is not characteristic of molecular crystals and can point to a contribution of “pseudorotation” to heat transfer. In phase II, cyclopentane the behavior of heat conductivity is close to a case of strong scattering of phonons.

Main Role of New High Strength, Toughness and Low-Density Steel in Artillery Lightweight

The new high strength, toughness and low density steel is a new generation of lightweight material with high protection, which is based on the theory of lattice dilution and lattice distortion and is manufactured by adding light elements to reduce its density. Furthermore, after impact process, the composite effects such as transformation induced plasticity (TRIP) effect, twinning induced plasticity (TWIP) effect, microbands induced plasticity (MBIP) effect and phase transformation precipitation occur in the microstructure. The specific strength and specific stiffness are better than those of aluminum, magnesium and titanium alloys, and the modulus is 3 times that of aluminum alloy and 2 times that of titanium alloy. Preliminary research shows that the application of low density steel in artillery system can greatly reduce the production cost. On the basis that all technical and tactical indexes meet the design requirements, it can realize lightweight, long-distance strategic delivery and battlefield real-time repair.

Numerical study on the fire behaviour of restrained steel-concrete composite beams

An elaborate solid-shell finite element model was developed to investigate the fire behavior of restrained steel-concrete composite beams. The model was validated against experimental results in literatures. Parametric studies were also performed to study the parameters including restraint stiffness, load ratio, span, exposure length, embedding depth, steel beam height and protective layer on the fire behavior of restrained composite beam. The analysis results show that the mechanical response of restrained composite beams goes through four phases: elastic, elasto-plastic, rapid plastic deformation and plastic catenary action phase. With the decrease of restraint stiffness, the increase of load and span, the failure mode of the restrained composite beam changes from overall lateral instability to a sharp increase in deformation rate, and the code BS476-20 and ISO834 underestimate the fire resistance of restrained composite beams. The negative bending moment at the beam end increases sharply and reaches the peak value within a short fire time. Therefore, reinforcement shall be provided at the top of the concrete slab near the support section. Furthermore, the difference in fire resistance of restrained composite beams is mainly reflected in the plastic catenary action phase. When the load ratio is less than 0.5, the fire resistance of restrained composite beams can be improved by reducing the fire range, beam height and span, and increasing the axial restraint stiffness. When the load ratio is 0.7, the fire resistance of restrained composite beam is hardly affected by the axial restraint stiffness and span, while with the exposure length reducing from 5 m to 4 m, embedded depth increasing from 0 mm to 50 mm, and the protective layer increasing from 0 mm to 10 mm, the fire resistance of the composite beams increases by 114 min and 160 min and 76 min, respectively.

Solid Electrolytes in the N-Propyl-N-methyl-pyrrolidinium Tetrafluoroborate—Lithium Tetrafluoroborate System

Solid electrolytes prepared by the addition of LiBF4 to the plastic phase of [N13pyr]BF4 were prepared, and their physical and electrical properties were investigated. The electrolytes [N13pyr]BF4-LiBF4 containing 8–20 wt% LiBF4 are solid at temperatures below 80 °C and have a high ionic conductivity ~10−3–10−2 S cm−1 at 60 °C. Based on the results of DSC and conductivity studies, the phase diagram of the [N13pyr]BF4-LiBF4 binary system was plotted, and the formation of a new compound, 3[N13pyr]BF4·2LiBF4 was proposed. The existence of the new phase was supported by X-ray diffraction data. Electrochemical measurements of cells with lithium electrodes were carried out to test the applicability of these materials in lithium batteries. The electrochemical window was determined to be more than 5 V. In contrast to earlier data obtained for similar systems, the preconditioning effect was not observed. Nevertheless, the solid electrolyte [N13pyr]BF4-LiBF4 system has high ionic conductivity and may be used in solid-state lithium-ion batteries.

Systematic investigation on the effect of processing procedures on the performance of oil‐resistant thermoplastic vulcanizates based on HNBR/TPEE

AbstractThe unique “sea‐island” phase of thermoplastic vulcanizates (TPVs) dictates an inseparable correlation between micro‐morphology and properties, the studies on the processing procedures in dynamic vulcanization are of great significance for the preparation of TPVs with desirable performance. Herein, a new type of oil‐resistant TPV with superior stretchability, low hardness, and high elasticity has been successfully fabricated based on hydrogenated acrylonitrile butadiene rubber (HNBR) and thermoplastic polyester elastomer (TPEE). The effect of processing procedures on the phase morphology, rubber network strength, mechanical properties, rheological performance, thermal stability, and oil resistance of HNBR/TPEE TPV was systematically investigated. In the masterbatch procedure, the homogeneous dispersion of the cross‐linking agent in the rubber phase contributes to stronger rubber networks and effectively reduces HNBR particle size. TPV prepared by masterbatch procedure exhibits a more comprehensive performance with improved mechanical properties, better rheological performance, enhanced thermal stability and oil resistance. In contrast, excessive dispersion of peroxide in the plastic phase during the pre‐compound procedure is demonstrated to the degradation of TPEE, resulting in large‐sized defective domains, while the deterioration of the rubber network leads to the inferior performance of TPV. This study provides new insights into the selection of the optimal procedure for preparing oil‐resistant TPVs.

Cyclo-hexane plastic phase I: single-crystal diffraction images and new structural model.

The plastic phase of cyclohexane (polymorph I) was studied by Kahn and co-workers, without achieving a satisfactory determination of the atomic coord-inates [Kahn et al. (1973). Acta Cryst. B29, 131-138]. The positions of the C atoms cannot be determined directly as a consequence of the disorder in a high-symmetry space group, an inherent feature of plastic materials. Given this situation, the building of a polyhedron describing the disorder was the main tool for determining the molecular structure in the present work. Based on the shape of reflections {111}, {200} and {113} in space group Fm 3 m, we assumed that cyclohexane is disordered through the action of rotation group 432. The polyhedral cluster of disordered molecules is then a rhombic dodecahedron centred on the nodes of an fcc Bravais lattice. The vertices of this polyhedron are the positions of C atoms for the cyclohexane molecule, which is disordered over 24 positions. With such a model, the asymmetric unit is reduced to two C atoms placed on special positions, and an acceptable fit between the observed and calculated structure factors is obtained.

Cold Compaction Behavior of Unsaturated Titanium Hydride Powders: Validation of Two Compaction Equations

Unsaturated titanium hydride (TiHX) powder has high formability and is a promising raw material for titanium-based powder metallurgy. In this work, TiH2, TiHX, and HDH Ti powders were characterized, the cold compaction behavior of the powders was investigated, and the densification mechanism was analyzed. The TiHX was a three-phase mixture containing an α plastic phase and δ and ε brittle phases through Rietveld refinement. The TiHX compacts had compressive strength of over 420 MPa (higher than TiH2 and similar to HDHTi) and relative density of over 80% (higher than TiH2 and HDH Ti) at 600 MPa. The Gerdemann–Jablonski and Cooper–Eaton equation were used to simulate the powder compaction curves and describe powder compaction behavior. The plastic deformation of TiHX powder is greater than TiH2, and the particle rearrangement is greater than HDH Ti during cold compaction. Such compaction behavior of TiHX causes an excellent green-strength–relative-density combination.

Enhancing the toughness of nano-composite coating for light alloys by the plastic phase transformation of zirconia

Toughness of ceramic coatings is essential for engineering deploys of light alloys, especially for the scenarios tackling with corrosion and wear. This work reports a toughened ZrO2/MgO coating on Mg alloy enabled by stress-induced martensite transformation from tetragonal zirconia (t-ZrO2) to monoclinic zirconia (m-ZrO2), which is achieved by the plasma electrolytic oxidation (PEO) process. Observations reveal that the interfaces between ZrO2 and MgO grains are essential in inducing phase transition during the toughening process. Interestingly, semi-coherent interfaces were found between t-ZrO2 and MgO, and the mismatched atoms at the interface cause local lattice distortions. These lattice distortions provide an appropriate dislocation density (2.2 × 105 /m2–4.1 × 105 /m2), which not only ensures the stability of the interface but also provides a stress transfer channel to induce martensite transformation of ZrO2. The plastic phase transformation is accompanied with volume expansion of ZrO2 grains, thus a compressive stress field is generated to resist the crack propagation with an enhancement of the plasticity of the composite ceramics. As a result, the toughness of the enhanced coating is about 1.15 times higher than that of the traditional PEO coating. This work provides an alternative strategy for designing toughened ceramic coatings for light alloys.

The structure and properties of mechanochemically modified acrylonitrile butadiene rubber (NBR)/poly (vinyl chloride) (PVC) scraps and fresh NBR composites

Vulcanized acrylonitrile-butadiene rubber (NBR)/poly (vinyl chloride) (PVC) blends are mainly served as insulation rubber-plastic materials. However, methods to reuse the waste NBR/PVC composites lack research. Here, we found that the mechanochemically modified waste NBR/PVC composites powders (WNPP) could be an alternative to fresh NBR. According to the results, the optimal replacement amount of WNPP for NBR was 20%, and the highest feasible proportion was 40%. WNPP treated by solid-state shear milling technology (S3M) would have a high degree of desulfurization, and the cross-linked chains within WNPP would be transformed into free chains. While co-vulcanizing, the sulfur agents and heat would induce the free chains of WNPP to react with the polymer chains of the NBR substrate, thereby generating dangling chains to form a robust interfacial layer. It was beneficial for the improvement of the mechanical properties of reclaimed products. And the strain of the excellent recycled sample (20C) reached 707%. Moreover, the modified WNPP in the co-vulcanized rubber represented heterogeneity because of the internal residual crosslinked network and the not-melting PVC plastic phase. Although the heterogeneity of WNPP damaged the continuity of the NBR matrix, it also brought a better hysteresis loss capability to the composite. In conclusion, this work expanded the mechanochemical application scope in recycling NBR/PVC wastes.

Influence of nano-indentation depth on the elastic–plastic transformation of 6H-SiC simulated

To investigate the effect of nano-indentation depth on the elastic–plastic transition mechanism of 6H-SiC, the loading process of nano-indentation on a 6H-SiC⟨0001⟩ crystal surface is analyzed by using the molecular dynamics method. Diamond indenters and 6H-SiC amorphous nanolayers are constructed; Tersoff and Vashishta potential functions are established to describe the interactions between atoms; and simulated environmental factors, such as relaxation conditions, ensemble, and loading speed, are optimized. The stress distribution and internal deformation characteristics are analyzed by combining load–displacement curves, radial distribution curves, dislocation nucleation, and their evolutive processes. The load–displacement curve deviates from the theoretical value at a depth of 3.8 nm and enters the elastic to plastic transition phase, where the shear stresses generated by friction on the contact surfaces cause the atoms on the stacked layers in the elastic phase to move in a directional manner and form dislocations: edge-type dislocations connecting the two layer dislocations and horizontal spiral dislocations. The plastic deformation phase starts at a depth of 5.9 nm, the atoms keep migrating and reorganizing, the original dislocation rings break to form incomplete dislocations, and the new dislocations formed by the combination of partial edge-type dislocation rings expand internally until fracture. The formation and expansion of dislocations contribute to the elasto-plastic transformation of 6H-SiC, and amorphous states are found to be involved in the deformation process at both the indentation contact surface and the deformation layer. Moreover, there are differences in the direction of dislocation expansion due to the inhomogeneous stress distribution at the contact surface.