Higher Shear Deformation Research Articles

Compatibilization of Polymer Blends under Conditions of High Pressure and Shear Deformation

AbstractStructural changes in polylactide/polybutylene terephthalate (PLA/PBT) and glycol‐modified polyethylene terephthalate/polybutylene terephthalate (PET‐G/PBT) polymer blends at a pressure of 1 GPa and room temperature in combination with shear deformation are investigated. High pressure torsion (HPT) is chosen as the compatibilization technique. Based on solid‐state NMR data, it is found that the compatibility of immiscible polymers is significantly improved under high pressure conditions in combination with shear deformation. It is assumed that the thickness of the deformed polymer layers decreases to the thickness of the interphase and it can be a fully interphase material.

Experimental investigations on prefabricated interlocking prestressed tendon composite joint and its application to beam-column connection

This study proposes an interlocking prestressed tendon composite joint (I-PTCJ) that can be applied to a beam–column connection of the multi-story structure. First, the main structure and prefabrication process of the I-PTCJ were introduced. Next, three beam–column specimens using local and integral I-PTCJs (named specimens PT1 and PT2) and a traditional interlocking joint (I-J, specimen named TG1) were designed and manufactured. Furthermore, quasi-static experiments were performed on these three specimens to evaluate their seismic performance. In addition, the influence of the prestressed tendons (PTs) and the arrangement mode (local or integral) of the I-PTCJs were investigated in detail. Finally, a preliminary comparative analysis between the experimental and simulated results was carried out. The results showed that the introduction of the PTs reduced the degree of damage within the PT installation area, delayed the cracking of the interlocking interface, and improved the bond performance of the longitudinal rebar. However, it also aggravated the degree of damage outside the PT installation area and reduced the displacement ductility and energy dissipation capacity of the specimen. Compared with TG1 (using the traditional I-J), PT1 (using the local I-PTCJ) had a higher peak load, lower displacement ductility, higher shear deformation, gentler rigidity deterioration, and lower cumulative energy dissipation. Compared with PT1, PT2 (using the integral I-PTCJ) had a higher peak load, lower displacement ductility, lower shear deformation, lower cumulative energy dissipation, and better bond performance of the longitudinal rebar. Both the yield displacement angle and ultimate displacement angle met the deformability requirement of the existing building design codes. Thus, the proposed I-PTCJ can be applied to the beam-column connection of multi-story structures.

Investigation of the physical characteristics of Bi4Ti3O12, Bi2Ti4O11, Bi12TiO20, Bi2Ti2O7 ternary semiconductors

The mechanical, thermodynamics, electronic, optical properties of Bi4Ti3O12, Bi2Ti4O11, Bi12TiO20 and Bi2Ti2O7 ternary semiconductor materials were calculated and analyzed using first-principles calculations. The structural optimizations demonstrate that four ternary semiconductors are structurally stable. The mechanical parameters of Bi2Ti2O7 exhibit the highest resistance to deformation and average bonding strength, while Bi2Ti4O11 demonstrates the high shear deformation resistance. The Debye temperatures for these bismuth titanate semiconductors are in the following order: Bi2Ti4O11>Bi2Ti2O7>Bi4Ti3O12>Bi12TiO20. Both Bi12TiO20 and Bi2Ti2O7 exhibit high light absorption energies within specific ranges. Through the computational analysis presented in this paper, the theoretical data of bismuth-based semiconductors are enriched for further experimental investigations.

Interface Shear Strength Behavior of Cement-Treated Soil under Consolidated Drained Conditions

This paper presents a series of laboratory tests to determine the shear strength and interface shear strength of cement-treated silty soil under consolidated and drained conditions. The test variables include the effective normal stress, cement content, and curing period. Experimental results indicated that the effective shear strength and interface shear strength of cement-treated soil specimens increased significantly as the cement content increased. After 28 days, the average shear strength ratio increased from 1.28 to 2.4, and the average interface efficiency factor improved from 1.15 to 1.55 as the cement content increased from 3% to 10%. It resulted from an increase in grain size and the fraction of sand-sized particles in the treated soils, approximately in two-time increments for the specimens treated with 10% cement content after 28 days of curing. In addition, the peak and residual values of the shear strength and interface shear strength of the cement-treated soil specimens were determined to assess their brittle behavior under high shear deformation. Last, two new empirical models are introduced herein. The first power equation is to predict the shear strength ratio of cement-treated soil at 28 days of curing using the soil-water/cement content ratio. The other proposed model is useful for assessing the rate of shear strength and interface shear development of cement-treated soil specimens within 56 days of curing.

Physicochemical properties of cricket (Gryllus bimaculatus) gel fraction with soy protein isolate for 3D printing-based meat analogue

Cricket (Gryllus bimaculatus) gel was fractionated and mixed with different soybean protein isolate (SPI) concentrations, and its characteristics were evaluated to determine its potential use as a meat analog. Crushed crickets were separated into the filtrate, supernatant, and pellet fractions by centrifugation and freeze-drying, and powdered and mixed with 18% SPI at different concentrations (5%–20%). The filtrate fraction had the lowest protein content and the highest fat and carbohydrate content among the nutrient fractions. Conversely, the supernatant and pellet fractions had high protein, low fat, and low carbohydrate content. SDS-PAGE detected relatively low-molecular weight proteins. Numerous muscle proteins were identified, including actin, myosin, and hemocyanin, a protein that transports oxygen in insects. Regarding the rheological characteristics of the cricket fraction, the entire fraction exhibited G'>G" in both the frequency and the temperature sweep tests, revealing a tendency for gel-like viscosity. In all cricket fractions, both G' and G" increased with increasing fraction powder concentration. When printed, supernatant fractions had no structural stability, pellet fractions had 5%–15% stability, and filtrate fractions had 5%–20% stability. The three interval thixotropy test revealed that the pellet fraction had a recovery rate of over 90% after high shear deformation. Texture profile analysis showed an increase in both hardness and chewability. After heat treatment, cohesiveness was higher than adhesiveness, indicating greater elasticity. Field-emission scanning electron microscopy results revealed that the pellet fraction was denser than the other fractions, particularly at higher concentrations. Based on the overall characteristics, 15% pellets were found to be the most appropriate fraction and concentration.

Tension–compression biaxial test with ±45° symmetric angle-ply laminates for determining the pure shear response in principal material directions of a lamina

The tension–compression biaxial test with cruciform specimens using ±45° symmetric angle-ply laminates is proved to be suitable for determining the in-plane pure shear response of a lamina in principal material directions. The full stress–strain evolution presents a linear stage followed by an inelastic region with high shear deformations. At the linear stage a pure and homogeneous shear strain state is measured by Digital Image Correlation (DIC). Afterwards, the DIC registers the initiation of a shear band in the measurement region at 45° from the loaded directions that leads to the final failure plane. It is verified that the arms of the specimen, which are uniaxially loaded, do not develop pseudo-ductile effects during testing that could affect the central response. For comparison purposes, the ability to obtain an accurate shear elastic response from uniaxial loading with ±45° angle-ply laminates is investigated. Based on the elastic strain energy involved in the linear stage of the testing process, it is concluded that both uniaxial tensile and compressive tests could overestimate the shear stiffness. Moreover, if the material has higher tensile than compressive elastic properties, the uniaxial tensile tests should provide a slightly better approximation of the shear elastic modulus than uniaxial compressive tests.

Vortex Structure Topology Analysis of the Transonic Rotor 37 Based on Large Eddy Simulation

Highly three–dimensional and complex flow structures are closely related to the aerodynamic losses occurring in the transonic axial–flow compressor. The large eddy simulation (LES) approach was adopted to study the aerodynamic performance of the NASA rotor 37 for the cases at the design, the near stall (NS), and the near choke (NC) flow rate. The internal flow vortex topology was analyzed by the Q–criterion method, the omega (Ω) vortex identification method, and the Liutex identification method. It was observed that the Q–criterion method was vulnerable to being influenced by the flow with high–shear deformation rate, especially near the end–wall regions. The Ω method was adopted to recognize the three–dimensional vortex structure with a higher precision than that of the Q–criterion method. Meanwhile, the Liutex vortex identification method showed a good performance in vortex identification, and the corresponding contribution of Liutex components in the vortex topology was analyzed. The results show that the high–vortex fields around the separation line and reattachment line had high vortex components in the x–axis, the tip clearance vortices presented a high–vortex component in the y–axis, and the suction side corner vortex possessed high–vortex components in the y– and z–axes.

Rheological behavior of the galactomannan fraction from Gleditsia triacanthos seed in aqueous dispersion

The purpose of the current study was to explore the influence of hydrochloric acid and sodium hydroxide, and sodium chloride on the rheological behavior of the galactomannan fraction from Gleditsia triacanthos seeds in aqueous solution. The flow (shear and extensional) and viscoelastic behavior as well as the dielectric properties were analyzed. The results indicated the existence of an interconnected microstructure, mainly in the macromolecular systems dispersed in HCl aqueous-solution, whose macromolecular arrangement leads to higher shear and extensional viscosity profiles, and contributes to improve the resistance to high shear deformation of this systems. The electrical conductivity profile of the Gledi -galactomannan in NaOH, HCl and NaCl aqueous-solution would indicate an increase or improvement in the continuity of the macromolecular arrangements compared to the polysaccharide in water. The conjugation of the galactomannan with Cl − ions would contribute to stabilize the microstructure. These results contribute to understand how the galactomannan fraction from Gleditsia triacanthos seeds could influence the microstructure and texture of ended-products, helping to consider its future applications. • Gledi -galactomannan in HCl-solution showed the highest shear and extensional viscosity. • Gledi -galactomannan developed a more interconected microstructure in HCl-solution. • HCl-solution improved the resistance of the Gledi -galactomannan arrangement. • Gledi -galactomannan and Cl − ions conjugation could contribute to stabilize the microstructure.

Impact-induced deformation and ignition related to localized viscous shear flow heating for high-ductility composite energetic materials

Understanding the impact-induced deformation and ignition properties of high-ductility composite energetic material (CEM), including high-energy propellants and casted high explosives, is fundamental to the safety design and usage of rockets and warheads and has been a broad concern in the fields of aerospace and defence. In this study, an impact ignition experiment is designed using a Split Hopkinson Pressure Bar to quantitate the continuum deformation and reaction responses of a high-ductility CEM sample undergone periodic impact loading pulses. The relation between macroscopic shear deformation rate and localized viscous shear flow heating, melting, and reaction is further investigated utilizing a macro-mesoscopic thermomechanical model. The results show that CEM sample is severely crushed to 2% of the original thickness and laterally extruded with a high shear rate (∼105 s−1). High shear deformation rate contributes to the localized viscous shear flow heating, thereby inducing temperature rise spike (∼200 K) and following ignition. Ignition of CEM sample occurs in the third compression pulse because the thinner sample exhibits a high velocity gradient, which causes a high viscous shear flow heating rate.

Transition of deformation mechanisms from twinning to dislocation slip in nanograined pure cobalt

• Gradient nanograined structures were prepared by plastic deformation in a pure cobalt sample. • Atomic-scale observation for microstructure characteristics was conducted in nanograined cobalt. • Comparing deformation mechanisms between nanograins and submicron-grains indicates a transition of governing deformation mechanism as reducing the gain size to nanoscale. Deformation mechanisms of nanograined and submicron-grained pure cobalt processed by means of high strain rate shear deformation at cryogenic temperatures were studied. Microstructural analysis revealed a transition of governing deformation mechanism from deformation twinning and < a > dislocation slip in submicron-grains to < c + a > and < a > dislocations slip in nanograins. Microhardness tests illustrated that the Hall-Petch relation slope changes consequently with the transition of deformation mechanism.

Atomistic understanding of extreme strain shear deformation of Copper-Graphene composites

Copper-Graphene (Cu-Gr) composites demonstrate high strength, lubricity, and enhanced electrical and thermal conductivity compared to pure copper. A homogeneous dispersion of graphene/graphitic domains in Cu is highly desirable, which can be achieved by solid-state shear-assisted processing. A detailed understanding of structure evolution of Cu-Gr under deformation is needed. Here we subjected Gr coated Cu foils to high strain shear deformation using a tribometer to observe the distribution and reallocation of Gr in Cu matrix. A rupture and smearing of Gr layer into Cu were observed reducing the Cu grain size from 67 ± 14 μm to <10 nm, in maximum shear region close to surface. While a gradual strain accumulation further below resulted in grain rotations and dynamic recrystallization. During deformation, the Gr film was first observed to fracture into flakes and then embed into the Cu matrix. Graphitic domains observed in the Cu evinced the metastable composite microstructure with a sandwich layer of Cu2O on the interface. The local conductance, measured by conductive atomic force microscopy, shows a fivefold increase in Cu-Gr composite region compared to pure Cu. Our study shows the feasibility of shear processing to create fine-grained Cu-Gr composites with enhanced conductivity.

Assessing effects of parameters of viscoelastic foundation on the dynamic response of functionally graded plates using a novel HSDT theory

In this study, vibration response of functionally graded plate resting on a viscoelastic foundation is studied. An analytical solution is proposed using a high-order shear deformation theory with only four unknowns, which means that the current theory has few unknowns compared to the first and other high shear deformation theories. The present theory uses a displacement field with integer terms instead of derivative terms by also including the shear deformation effect without introducing the shear correction factors. The mathematical model of the foundation used followed the Winkler–Pasternak two-coefficient model, with an additional term added to represent the damping effect. The governing equations were generated using the principle of virtual works. Subsequently, the analytical solution is based on Navier's principle to solve the vibration problem of a simply supported FG plate resting on a viscoelastic foundation. Some numerical results are presented to demonstrate the impact of the material index, the type of elastic foundation and the damping coefficient of the foundation on the dynamic response of FG plates resting on viscoelastic foundations. In the end, it is concluded that the current results with the proposed theory are found to be in good agreement with the other available results and this theory can easily be used to solve the free vibration problems of FGM plates resting on visco-Pasternak medium.

Static and dynamic response analysis of corrugated core sandwich plates under patch loading

Static and dynamic response analysis of sandwich plates having corrugated core under patch loading is presented in this paper. In this work, the problem formulation is made using finite element-based higher shear deformation theory. The influence of various parameters like aspect ratio, corrugated plate thickness, core thickness, corrugation angle, boundary conditions, ratio of face thickness to corrugation plate thickness on transverse deflection, stresses, and dynamic bending responses are revealed. In the present investigation, a MATLAB program is developed with nine nodded seven degrees of freedom per node of element. The obtained results are verified with available results in the literature to check the program’s efficiency. It is found that transverse deflection increases with increase in corrugation angle, and maximum rotation about the ‘x’ and y-axis increases with increase in the area of the plates exposed to patch loading. Edge constraints have a significant effect on transverse deflection and stress.

Microstructural and Texture Evolution in Pure Niobium during Severe Plastic Deformation by Differential Speed Rolling.

The evolution of the microstructure and texture in body-centered cubic (BCC) niobium (Nb) during conventional rolling and high-ratio differential rolling (HRDSR) at room temperature were compared. More effective grain refinement of the initial microstructure through continuous dynamic recrystallization (CDRX) occurred in the samples processed by HRDSR, but the overall degree of grain refinement was small, despite having undergone severe plastic deformation due to the low rate of CDRX. CDRX more preferentially proceeded on {111}<uvw> γ-fiber grains than on {001}<110> α-fiber grains. The HRDSR-processed samples exhibited weaker α-fiber and stronger γ-fiber than the conventionally processed samples, which indicates that the high shear deformation induced by HRDSR discourages the development of α-fiber while promoting the development of γ-fiber. The HRDSR processed Nb showed a high tensile strength of 450 MPa, and the major strengthening mechanism for the HRDSR-processed Nb was dislocation-density strengthening at large thickness reductions.

Modeling and Analyzing the Free Vibration of Simply Supported Functionally Graded Beam

Euler, Timoshenko and high shear deformation theories to analyze the free vibration of the functionally graded (FG) beam were developed. The mechanical properties of this beam were assumed to differ in thickness direction according to the model of a power-law distribution. The principle of Hamilton was used to find equations of motion. For free vibration, the analytical solution of these equations was presented using the Navier method. The effect of power index, aspect ratio, modulus ratio, and deformation theories on dimensionless frequency were studied numerically by Ansys software and analytically according to different beam theories using the Fortran program. The obtained results from these programs were compared with each other and with some previous research. Results showed an excellent agreement with the previous research. The numerical and analytical results showed that the use of this new FG beam model especially based on first and high shear deformation theories leads to the reduction of dimensionless frequency. It may be concluded that, the including of shear’s effect leads to a decrease in the dimensionless frequency. From the modeling and analysis of this model, it is possible to know what is the appropriate design for this FG beam model to reduce the vibration.

The onset of alloying in Cu-Ni powders under high-shear consolidation

Friction consolidation (FC) is a solid phase processing methodology that densifies a material through high-shear deformation and pressure at elevated temperature. The method has garnered interest in the scientific community because of its ability to produce extremely refined and homogeneous microstructures, off-axis texture development, and improved material properties. This manuscript presents an investigation of Cu and Ni material mixing via evaluation of morphological evolution, grain boundary characterization, and compositional analysis to provide insights on the operational alloying mechanisms occurring under high shear and elevated temperature. Using correlative microscopy techniques, we show alloying progresses via a combination of grain boundary diffusion and interfacial roughening at heterophase boundaries. Evidence supporting Cu infiltration along Ni-Ni grain boundaries along with asymmetric diffusion of Cu into Ni grains is highlighted. The resultant, consolidated microstructure was produced directly from a powder compact in ∼30 s and exhibited a submicrometer, equiaxed grain size.

3D printing of porcelain: finite element simulation of anisotropic sintering

Sintering is a key step that determines the mechanical performances and shape quality of 3D printed ceramics. In this domain, there is an increasing interest in complex thin structures and low fill density shapes. However, these complex structures may suffer from distortions by gravity forces developed on the light structure, friction with supports, shrinkage anisotropy, or thermal gradients. Finite element simulation of the sintering process is then of high importance for predicting the specimens distortions. This paper focuses on the identification of the model parameters in the special case of anisotropic sintering of porcelain with final stage swelling. This study points out the printed specimen high resistance to high temperature shear deformation due to the alignment of the printed rods. A mesoscale simulation has been carried out to explain this mechanism. The resulting model was tested for the sintering of a thin wall cup shape.

Late Cretaceous felsic intrusions in oceanic plateau basalts in SW Ecuador: Markers of subduction initiation?

Felsic magmatic rocks (tonalites and trondhjemites) with calc-alkaline affinity were emplaced in SW Ecuador (Pascuales area; North Guayaquil) at ~87–89 Ma intruding the top of the basalts of the Caribean Large Igneous Province (CLIP), prior to the development of typical well-known island arcs from ~85 to 80 Ma onwards. A clear depletion of REE distinguishes the Pascuales felsic rocks from the more differentiated lavas of the Rio Cala Arc in Ecuador and from other Late Cretaceous arc-like felsic intrusives emplaced within the CLIP in Colombia and the Antilles. In addition, the Pascuales tonalites have very low K2O (<0.4 wt%), TiO2 (<0.4 wt%) and P2O5 (<0.15 wt%) contents compared to dacitic rocks of the Rio Cala Arc. In contrast, their geochemistry and their similar age suggest that the Pascuales tonalites are an equivalent of the Las Orquideas dacitic volcanic rocks. The Pascuales felsic rocks have the less radiogenic Nd compositions of the whole spectrum of Ecuadorian oceanic plateau rocks, nevertheless shearing similarities with some Totoras amphibolites. The geochemical characteristics of the Pascuales intrusives and Las Orquideas dacites are similar to those formed by hydrous partial melting of mafic protoliths. The dacitic magmas must have been in equilibrium with residual mineral assemblages largely dominated by amphibole + Fe–Ti oxides (no garnet). This requires two conditions: 1) low-pressure melting under high water content and 2) a source rock extremely depleted in minor incompatible elements (K, Ti, P, Y) and REE. These conditions are fulfilled by partial melting of mafic-ultramafic cumulates undergoing high temperature and shear deformation at the base of the oceanic plateau triggered by new basaltic intrusions. The Pascuales felsic rocks emplaced at the SW border of the oceanic plateau during its final stage of building; they can thus be related to asthenopheric upwelling during the initial stage of island arc magmatism.

Copper carbon composite wire with a uniform carbon dispersion made by friction extrusion

Copper-carbon composites are a group of materials with excellent mechanical, electrical, thermal, and tribological properties. However, bulk size copper-carbon composites made by the traditional manufacturing processes, like rolling or extrusion, fall short of reaching some of these properties predicted by theory or demonstrated only by samples at centimeter scale or smaller. The two main challenges to the successful scaling-up are: 1) to uniformly disperse carbon in the metal matrix; 2) to avoid degradation due to oxidation or reaction from overheating. In this work, we first demonstrate friction extrusion as a new method to make bulk-size void-free copper-carbon composite wires with homogenized carbon dispersion. Three different carbon varieties, graphite powder, graphene nanopowder, and carbon nanotubes, were added to the copper matrix with the concentration ranging from 0.5 wt% to 15 wt%. Special tooling, processing parameters, and procedures were developed, especially for high carbon content samples. Ten-fold reductions of both copper grain size and carbon particle size were achieved and attributed to the high shear deformation. Energy dispersive X-ray spectrometry indicates the carbon powder was refined to a sub-micron level and uniformly dispersed in the copper matrix. Compared with that of pure copper, the thermal capacity of the composite wire increases by 30 % while density reduces by 29 %.

Metallic Composites, Prepared by Deformation Processing

The main point of successful manufacture of metallic composites by direct bonding of dissimilar materials is achieving a homogeneous interface bonding. Two different types of deformation techniques for fabrication of metal composites were investigated. The first one was developed on the basis of high pressure torsion associated with a high energy impact on the material where part of energy involved can be dissipated via non equilibrium phase transition realization. This deformation due to high shear deformations allows not only to form a nanostructure, but also to bond dissimilar metals. Moreover, this method allows for a relatively short time and in a number of compounds to receive in one step at room temperature monolithic composites of sufficient size to certify the structure and properties. The second technique is diffusion bonding which integrate one material with the other by pressure under high temperature. In order to clarify the bonding mechanism by plastic deformation of dissimilar materials, the microstructural and some mechanical properties were studied in the processed samples.