Relative Deformation Research Articles

Cryogenic tensile properties and deformation behavior of a fine-grained near alpha titanium alloy with an equiaxed microstructure

Different from previous research works on cryogenic titanium alloys with a lamellar microstructure, this study focused on cryogenic tensile properties and the related deformation mechanism of a fine-grained near alpha titanium alloy of equiaxed microstructure. The fine-grained equiaxed Ti–3Al–3Mo–3Zr alloy exhibited a remarkably enhanced cryogenic tensile strength until 20 K, but cryogenic ductility decreased sharply as temperature drops. Ultimate tensile strength jumped from 740 MPa at 298 K to 1290 MPa at 77 K and to 1535 MPa at 20 K, while elongation-to-fracture dropped from 20.0% to 12.5% and to 4.0%, respectively. Sharp decline of cryogenic ductility was considered to be directly influenced by the high-angle misoriented equiaxed α-Ti grains. Because dislocation motion got much difficult and twinning could not operate extensively in the fine equiaxed microstructure at cryogenic temperatures. Besides, slip and twinning could not transfer across α-Ti grain boundaries or α/β phase interfaces, resulting in premature cracking. Different from deformation of traditional counterpart with a lamellar microstructure, prismatic and basal slips invariably dominated at 298, 77 and 20 K. Only in certain α-Ti grains whose <0001> parallel to loading direction, {10 1‾ 2} type tension twins operated at 77 and 20 K. The present fine-grained near α-Ti alloy with an equiaxed microstructure is suggested to be applied at temperature not lower than 77 K.

A Grip Strength Estimation Method Using a Novel Flexible Sensor under Different Wrist Angles.

It is a considerable challenge to realize the accurate, continuous detection of handgrip strength due to its complexity and uncertainty. To address this issue, a novel grip strength estimation method oriented toward the multi-wrist angle based on the development of a flexible deformation sensor is proposed. The flexible deformation sensor consists of a foaming sponge, a Hall sensor, an LED, and photoresistors (PRs), which can measure the deformation of muscles with grip strength. When the external deformation squeezes the foaming sponge, its density and light intensity change, which is detected by a light-sensitive resistor. The light-sensitive resistor extended to the internal foaming sponge with illuminance complies with the extrusion of muscle deformation to enable relative muscle deformation measurement. Furthermore, to achieve the speed, accuracy, and continuous detection of grip strength with different wrist angles, a new grip strength-arm muscle model is adopted and a one-dimensional convolutional neural network based on the dynamic window is proposed to recognize wrist joints. Finally, all the experimental results demonstrate that our proposed flexible deformation sensor can accurately detect the muscle deformation of the arm, and the designed muscle model and convolutional neural network can continuously predict hand grip at different wrist angles in real-time.

Response and mechanism of a tunnel subjected to combined fault rupture deformation and subsequent seismic excitation

In this study, sophisticated numerical methods and constitutive models were used to study the effect of combined fault rupture deformation and subsequent seismic excitation on a tunnel. The weakening of the rock-tunnel interface under relative dislocation and degradation of the concrete material in the tunnel liner were considered. The deformation response and failure mechanism of the tunnel subjected to combined fault rupture deformation and subsequent seismic excitation were investigated. The time histories of the relative deformation, the plastic strain, and the tensile strain of the tunnel were studied. The performance of the “joint” design was numerically verified, followed by a detailed parametric study that aimed to provide deep insight into the design factors of the technique of “flexible jointing”. The influences of some important factors were investigated, such as the range of the joints, length of the segments, and length of joint.

The quantum moment problem for a classical random variable and a classification of interacting Fock spaces

The fact that any classical random variable with all moments has a quantum decomposition allows to associate to it a family of quantum moments. On the other hand, a classical random variable may have several inequivalent quantum decompositions, which lead to the same classical, but different quantum moments. Even in the simplest Central Limit Theorems (CLT), i.e. those of Bernoulli type, there are examples in which the corresponding quantum moments converge to the canonical quantum moments of the associated classical random variable, and examples in which this is not the case. This poses the problem to find a constructive criterium that characterizes the quantum moments associated to the canonical quantum decomposition (which is unique) with respect to the other ones. Theorem [Formula: see text] of the present paper provides such a criterium. Theorem [Formula: see text] deals with the case when one knows a priori that the quantum moments come from a central limit theorem (the motivation of the present paper arose in this context). It gives only a sufficient condition, but simpler to verify than the necessary and sufficient conditions of Theorem [Formula: see text]. Theorem [Formula: see text] naturally leads to a classification of Interacting Fock Spaces (IFS) into three types. We construct examples showing that all these possibilities can effectively take place. On the way, we prove that all the best known deformations of Heisenberg commutation relations can be obtained as special cases of a general construction within the algebraic approach to the theory of orthogonal polynomials.

Understanding the Geodetic Signature of Large Aquifer Systems: Example of the Ozark Plateaus in Central United States

AbstractThe continuous redistribution of water involved in the hydrologic cycle leads to deformation of the solid Earth. On a global scale, this deformation is well explained by the loading imposed by hydrological mass variations and can be quantified to first order with space‐based gravimetric and geodetic measurements. At the regional scale, however, aquifer systems also undergo poroelastic deformation in response to groundwater fluctuations. Disentangling these related but distinct 3D deformation fields from geodetic time series is essential to accurately invert for changes in continental water mass, to understand the mechanical response of aquifers to internal pressure changes as well as to correct time series for these known effects. Here, we demonstrate a methodology to accomplish this task by considering the example of the well‐instrumented Ozark Plateaus Aquifer System (OPAS) in the central United States. We begin by characterizing the most important sources of groundwater level variations in the spatially heterogeneous piezometer dataset using an Independent Component Analysis. Then, to estimate the associated poroelastic displacements, we project geodetic time series corrected for hydrological loading effects onto the dominant groundwater temporal functions. We interpret the extracted displacements in light of analytical solutions and a 2D model relating groundwater level variations to surface displacements. In particular, the relatively low estimates of elastic moduli inferred from the poroelastic displacements and groundwater fluctuations may be indicative of aquifer layers with a high fracture density. Our findings suggest that OPAS undergoes significant poroelastic deformation, including highly heterogeneous horizontal poroelastic displacements.

Advances in electrospun TiO2 nanofibers: Design, construction, and applications

• Structure control of electrospun TiO 2 NFs through various strategies was summarized. • Mechanical flexibility adjusting of electrospun TiO 2 NFs and related deformation mechanism were discussed. • Multifunctional applications of electrospun TiO 2 NFs in environment, energy, and sensors were introduced. • Current challenges and future perspectives on the development of electrospun TiO 2 NFs were proposed. One dimensional (1D) TiO 2 nanomaterials, as one of the most important semiconductor materials, which have attracted much attention due to their unique structural feature, outstanding optical or electronic properties. Electrospinning is one of the most facile and highly versatile approaches to fabricate 1D TiO 2 nanofibers (NFs) with high porosity, controllable dimensions, designed structures, and adjustable mechanics, which hold great promise in many areas including photocatalytic degradation, solar cells, lithium-ion batteries, water splitting, sensors, and catalyst supports. In this review, progress in structure/mechanics design, fabrication and multifunctional applications of electrospun TiO 2 NFs are presented. The strategies to prepare electrospun TiO 2 NFs with diverse structures involving porous, hollow, hierarchical, aligned, and 3D self-assembled nanostructures are introduced and analyzed. Moreover, the recent breakthrough in the construction of flexible TiO 2 nanofibrous materials and corresponding deformation mechanism have been concerned. Furthermore, some achievements associated with the potential applications of electrospun TiO 2 NFs in the areas of environmental remediation, energy, and sensors are discussed. Finally, a straightforward summary, main challenges and future outlooks about electrospun TiO 2 NFs are proposed. It is anticipated that this review could provide guidelines for designing and constructing novel TiO 2 -based nanofibrous materials for advanced applications.

Moiré patterns and carbon nanotube sorting

Moiré patterns (MPs), arising from the superposition of two lattices with close periods, are tightly related to the physicochemical properties of bilayer nanostructures. Here, we develop the theory of complex MPs emerging in twisted bilayer graphene and planar nets of double-walled nanotubes at significant relative twist and/or deformation of layers. The proposed theory clarifies the physicochemical regularities arising at sorting of single-walled carbon nanotubes (SWCNTs) by organic molecules, which self-assemble in regular coatings on both the tubes and planar graphene. We introduce and consider an outer tubular virtual lattice that is a parent structure for the deposited coating and due to this fact, its existence is crucial for the coating formation. As we show, such outer lattices exist only for successfully sorted SWCNTs and the superposition between the outer lattice and SWCNT forms a specific long-period MP. We explain known experimental results of SWCNT sorting by molecules of flavin group, poly(9,9-dioctylfluorene-2,7-diyl), and poly [(m-phenylenevinylene)-alt-(p-phenylenevinylene)]. Also, our approach points out other organic molecules and polymers suitable for effective carbon nanotube sorting.

Moment at elastic-plastic bending of steel sheet. Part 2. Cubic approximation of steel's hardening zone

The classical approximations by P. Ludwik and A. Nadai of the steel hardening zone do not accurately describe the plastic deformation of steel. That often leads to the significant errors (defects) in the final form of metal products made from a steel sheet during its forming (based on the preliminary analytical and numerical calculations of the given model of metallurgical production) on the presses and dies. For example, the Nadai&rsquo;s curve does not pass through the ultimate strength&rsquo;s point of the experimental curve, signifi cantly exceeding the ultimate strength at this point, which is not permissible at calculating stresses and deformations. The Ludwik&rsquo;s curve does not take into account the elastic deformation zone of the steel (immediately has a stress equal to the yield strength at zero relative deformation) and does not have the maximum (observed on the experimental curve) at the point of the ultimate strength. To eliminate the above-mentioned disadvantages, in the first published part of the paper, the author considered the parabolic approximations of the steel hardening zone in the form of the second-order polynomials, which satisfy three boundary conditions. The constructed parabolic approximations of the steel hardening zone turned out to be an order of magnitude more accurate than the classical approximations by Ludwik and Nadai. In this paper, the author considers even more exact cubic approximations of the steel hardening zone with the same supporting parameters of the experimental curve of the steel hardening zone. In this case, the cubic approximations already satisfy four boundary conditions. The constructed cubic approximations of the steel hardening zone are two orders of magnitude more accurate than the classical approximations by Ludwik and Nadai of the steel hardening zone.

Internal deformation monitoring for earth-rockfill dam via high-precision flexible pipeline measurements

The internal deformation of high earth-rockfill dam is an important parameter that reflects its safety. There is an urgent need to have a precise and reliable internal deformation monitoring technology due to the limitation of traditional sensors. We propose a novel method to monitor internal deformation of dam through continuous measurement of flexible pipelines that embedded in the dam. A pipeline robot is invented, with one inertial measurement unit and multiple odometers, to measure the deformation of the customized pipeline system. The proposed method is verified through filed tests and real dam in suit experiments. The results show that the relative deformation measurement precision is approximately 1/100,000 the length of the pipeline and millimeter-level deformation measurement over 300 m can be realized. This technology is promising for internal deformation monitoring of high-rockfill dams. Further research will focus on the miniaturization of measurement system and reliability improvement of this technology.

Deformation Performance Analysis of a Truss Structure Based on the Deformation Decomposition Method

Trusses are among the basic components of large-span bridges and large-space structures. A method is proposed to conduct a comprehensive deformation analysis of a truss in terms of the basic rigid body displacements and the tension and compression deformation based on complete mathematical orthogonality and mechanical equilibrium. The correctness of the proposed method is verified by comparison with a traditional strain analysis. Furthermore, a relative deformation decomposition of the mode shape is proposed to analyse in detail its relative displacement and deformation. The correctness and superiority of the proposed method are verified by comparison with the modal mass participation coefficient method and the animation from observation method. Additionally, the relative deformation decomposition of a plane truss structure is realized under any load conditions based on the superposition of mode shapes. The quantitative analysis of the basic deformation performance of a plane truss structure can also be conducted by countable mode shapes, which do not involve load conditions. Finally, the number of mode shapes that must be considered differs when using the maximum displacement and the tension and compression deformation analysis indicators.

A novel constitutive model for the porosity related super-large deformation and anisotropic behavior of wood under perpendicular to grain compression

A novel constitutive model for the porosity related super-large deformation and anisotropic behavior of wood under perpendicular to grain compression

3D Radiological Outcomes and Quality of Life of Patients With Moderate Idiopathic Scoliosis Treated With Anterior Vertebral Growth Modulation Versus Bracing: Two-Year Follow-up.

Observational cohort study. To test the hypothesis that anterior vertebral body growth modulation (AVBGM) achieves 3D deformity correction after 2-year follow-up while brace treatment limits curve progression for moderate idiopathic scoliosis (30-50°). For idiopathic scoliosis, bracing and AVBGM have overlapping indications in skeletally immature patients with moderate scoliosis curve angles, creating a grey zone in clinical practice between them. The relative 3D deformity control performance over a 2-year period between these fusionless treatments is still uncertain. A retrospective review of a prospective idiopathic scoliosis patients database, recruited between 2013 and 2018 was performed. Inclusion criteria were skeletally immature patients (Risser 0-2), with Cobb angles between 30° and 50° and a 2-year follow-up after bracing or AVBGM. 3D radiological parameters and health related quality of life (HRQoL) scores were evaluated. Unpaired t test was used. Thirty nine patients (12.7 ± 1.3 y.o.) with Cobb angles more than or equal to 30° treated with brace and 41 patients (11.8 ± 1.2 y.o.) with presenting Cobb angles less than or equal to 50° who received AVBGM were reviewed. The statistical analysis of 3D deformity measurements showed that at 2-year follow-up, only the 3D spine length and both sides apical vertebral heights changed significantly with brace treatment. While AVBGM treatment achieved statistically significant correction differences in thoracic and lumbar Cobb angles, TrueKyphosis, 3D spine length, and selective left apical vertebral height ( P < 0.05). 35% of brace patients had a curve progression of more than 5° at final follow-up while it was 0% for AVBGM. HRQoL assessment showed no statistically significant differences between pre and post SRS-22 total scores for each group ( P > 0.05). Even though these two cohorts are not fully comparable, bracing seems to control progression for a significant portion of patients with moderate scoliosis curves, while AVBGM significantly corrected and maintained 3D deformity parameters at 2-year follow-up.

Experimental and numerical analysis of the defects induced by the thermoforming process on woven textile thermoplastic composites

In the present work, a parallel numerical and experimental analysis of a critical type of defect is conducted, the shear deformation which is caused by the thermoforming process of thermoplastic-based composites reinforced with glass fiber textile. The numerical analysis is conducted a priori using a commercial finite element software, developed for this specific process. In parallel, an experimental thermoforming test was conducted using the exact same parameters used for simulating the process and, consecutively, measurements of the component characteristics such as the fiber relative deformation of the textile are taken. Aiming to validate the simulation and to obtain crucial information about this phenomenon, a comparison between the finite element process simulation and the measurements output is conducted revealing a satisfying agreement between them, leading also to useful conclusions about the validity of the simulation method as well as about the detection and measurement of the shear textile deformation using optical systems.

Mathematical Model for Assessing the Limits of Crack Resistance of Structural Steels of Large-Sized Structures

In metal structures under operating conditions, as well as in emergency situations due to overloads, the presence of stress concentrators, etc., plastic deformations may occur. Such deformation by tensile stresses introduces some damage to the structure of steel, which adversely affects its subsequent operation under cyclic loads. Preliminary relative plastic deformation, ∼ 1-6%, which occurs in structural steels under tension, unambiguously reduces plasticity. It negatively affects the endurance of the material and leads to the early formation of macrocracks. In addition, after unloading, an internal residual stress field at the meso-micro level remains in the structural elements, which also reduces the endurance limit. In causes the decrease of such an important indicator of reliability as fracture toughness, which reflects the resistance of the material to crack propagation. In this regard, designing structures, it seems important to improve the calculation methods for assessing and predicting their fatigue strength, taking into account the listed factors.The article is devoted to the development of a mathematical model that includes dependencies for assessing the fracture toughness of metal structures according to the fracture toughness limit for all sizes of defects in the form of cracks. Analytical dependences have been obtained for calculating the relative limit of crack resistance based on the main mechanical characteristics of the state of the material. The results of the study can be used to assess the crack resistance of structural elements and welded joints pre-deformed by tension.

Properties evolution of calcium sulfoaluminate cement blended with ground granulated blast furnace slag suffered from sulfate attack

In this work, sulfate resistance of calcium sulfoaluminate cement (CSAC) blended with ground granulated blast furnace slag (GGBFS) was studied. The mass change, compressive strength, corrosion resistance coefficient, relative dynamic elastic modulus and deformation of CSAC-GGBFS mortars exposed to 5% Na2SO4 solution for different time were monitored. At the same time, the mineral phases, pore structure and microstructure of hardened cement pastes after sulfate attack were determined using X-ray diffraction (XRD), thermal analysis, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Results showed that the relative dynamic elastic modulus and compressive strength of the CSAC-GGBFS mortars increased continuously when the specimens were immersed in 5% Na2SO4 solution; besides, after 360 days of exposure, the compressive strength was 12% higher than the specimens cured in water. Meanwhile, the specimens displayed good dimensional stability after sulfate attack. What's more, no new mineral phases were found for the CSAC-GGBFS mixtures suffered from sulfate attack for 360 days, while the amount of AFt and C–S–H gels increased and the total porosity reduced. The CSAC-GGBFS mixtures showed excellent resistance to sulfate attack and can be applied in high sulfate environment.

Size-dependent deformation mechanisms in copper gradient nano-grained structure: A molecular dynamics simulation

Gradient nano-grained (GNG) structures exhibit an excellent combination of high strength and toughness. In this paper, molecular dynamics (MD) simulations have been utilized to investigate the tensile properties and related deformation mechanisms of GNG copper structures. Results show that larger gradients give higher strength within a certain size scale range. In the GNG structure, the grain size heterogeneous leads to the non-uniform stress distribution, and the synergistic deformation induced inverse Hall-Petch phenomenon is observed. Furthermore, while both large- and small-grained layers begin to have plastic deformation simultaneously, the dominant deformation mechanism is found to vary with grain size. For grains with 30-100nm, dislocation slips emitted from grain boundaries (GBs) dominate deformation, whereas GB activities, such as GB sliding and/or grain rotation, become the main deformation carrier for grains with 10-20nm. Our results provide a deeper understanding of the deformation mechanisms of GNG copper structures and give guidance for design GNG copper structures.

The Palisades at Sheep Creek Canyon Geological Area

The Palisades is an impressive ridge within the Sheep Creek Canyon Geological Area—an area nestled on the north flank of the eastern Uinta Mountains not far from Flaming Gorge National Recreation Area. Sheep Creek cuts through the Palisades, as well as the heart of the geological area, to reveal about 800 million years of geology, from ancient environments to the rise and ultimate erosion of the Uinta Mountains. The oldest rocks exposed at the Palisades comprise the upper part of the Neoproterozoic (about 770 million years ago) Uinta Mountain Group, which have been thrusted upon the Mississippian (about 350 million years ago) Deseret Limestone (equivalent to the upper Madison Limestone). That thrust fault and others exposed along the north and south sides of the Palisades are part of the Uinta thrust fault zone, which is responsible for intense folding of both formations. Although the uplift of the Uinta Mountains and related deformation along the Uinta fault zone set the stage for development of the Palisades, it was erosion that revealed and shaped this spectacular feature.

A variational approach to the analysis of excavation-induced vertical deformation in a segmental tunnel

This paper aims to provide an analytical solution for evaluating the deformation of a segmental tunnel induced by upper basement excavation. To this end, a model considering shear dislocation and rotation of a segmental tunnel is proposed and the interaction between tunnel and ground is modeled using a two-parameter Pasternak foundation model. The vertical displacement of the tunnel is then approximated by the finite Fourier series. Energy balance equations for the tunnel and soil are obtained via energy method and then the governing equation is derived based on the principle of minimum potential energy. With the variational approach, expressions for the tunnel heave, relative vertical deformation, rotational angle and shear force between two tunnel rings are derived. The feasibility of the proposed model is validated against the field data and the results obtained using Euler-Bernoulli beam and Winkler beam, indicating that the proposed method can be used to effectively estimate the responses of a segmental tunnel to upper excavation. Finally, a parametric analysis is performed to examine the effects of different factors on the responses of existing shield tunnel to upper deep excavation.

Application of paper sludge and clay in manufacture of composite materials: Properties and biological susceptibility

With the aim of developing composite materials to be used on indoor wall systems, different composite materials (paper sludge (100 wt%) and paper sludge (60 wt% and 80 wt%) + clay (20 wt% and 40 wt%) were produced. Composite materials were tested for biological susceptibility, physic-mechanical characteristics (shrinkage, density, water erosion resistance, compressive stress at 10% relative deformation and Young's modulus, ultra sound propagation velocity, thermal conductivity) and microstructure. The granulometric composition of paper sludge and clay content of the samples are essential factors that affect the physic-mechanical characteristics of the composite materials. This study considered 2 types (S type and S* type) paper sludge granulometric compositions. S type composite materials (paper sludge particles were smaller than 8 mm) have the better thermal conductivity, S* type composite materials (paper sludge particles were smaller than 4 mm) show the better performances in terms of compressive stress at 10% relative deformation. Increasing clay content (20% and 40%, S* type composite materials) increases density, shrinkage, compressive stress at 10% relative deformation, also, decreases biological susceptibility (Rhizopus oryzae mould). The results showed that, all composite materials had bulk density around 0.65–1.12 g/cm3, shrinkage 1.7–6.0%, compressive stress at 10% relative deformation 0.95–7.0 MPa, thermal conductivity 0.072–0.154 W/(mK). Also, all composite materials have good resistance to water erosion.

Combining Salter-Harris and Dias-Tachdjian could be better at determining the prognosis of distal tibial physeal fractures

ObjectivesThe aim of this study is determining the factors that affect prognosis of distal tibial physeal fractures (DTPF) and analyzing whether Salter-Harris (SH) or Dias-Tachdjian (DT) classification is more predictive for outcomes. MethodsPatients treated for DTPF were retrospectively analyzed. Fracture patterns were classified according to SH and DT. Treatment methods and fracture characteristics were noted. Distal tibial angles and joint irregularities were analyzed on patient's final ankle radiographs followed by American Orthopedic Foot and Ankle Score questionnaire. Results75 patients followed-up between 6 and 96 months meeting the inclusion criteria were evaluated. Joint irregularity was observed in 41.3% and partial premature physeal closure (PPC) in 34.7% of the patients. Lateral distal tibial angle (LDTA) and talocrural angle related deformity were detected in 20% and 14.7% of the patients, respectively. Partial PPC and joint irregularities that have been developed in pronation-eversion-external rotation and supination-inversion injuries (SH type 3, 4) were 62% and 50%, and 42% and 75%, respectively. On follow-ups of supination-external rotation injuries (SH type 2) joint irregularity has never been observed. Following supination-external rotation and supination-plantar flexion injuries, a low rate of partial PPC have been developed; LDTA related deformity was revealed at a high rate of 39.1% after supination-inversion injuries. There weren't any differences observed between the initial displacement, residual displacement or surgical technique and PPC, joint irregularity and angular deformities. Patients treated by ORIF technique had lower AOFAS scores than patients treated by other surgical techniques. ConclusionsIn this study it was revealed that SH classification system is not sufficient alone to determine the prognosis of DTPF, the injury mechanisms causing SH types might be also significant in prediction of the prognosis of DTPF.