Strain Transfer Research Articles

Understanding the High-Temperature Fatigue Crack Growth from Exceptional Nano-\u03b1 Phases and {10 bar{1} 2} Deformation Twins in Hot Deformed Titanium Alloy

In this study, the fatigue crack growth rate (FCGR) of Ti-6Al-4V alloy at 723 K was measured by direct current potential drop (DCPD) method, and exceptional nano-α phases and {10 bar{1} 2} deformation twins were newly found at the crack tip in Ti-6Al-4V alloy. The results showed that nano-α phases have Burgers orientation relationships (OR) (0001)α//(110)β, [ bar{2} 110]α//[ bar{1} 11]β with β phases. The terraced-structure interface consisted of (0 bar{1} 10)α//(1 bar{1} 2)β and (10 bar{1} 0)α//(1 bar{1} 0)β. Numerous dislocations accumulated in the β phase and became the diffused channels of O and V atoms. The α stabilizers (O element) diffused into the crystal lattice and β stabilizers (V element) spread out of the crystal lattice which accelerated the nano-α phases nucleation. <a> and <c + a> dislocations piled up at the primary α grain, interface and low angle grain boundaries (LAGBs), and dissociated into twinning dislocations to promote the twin nucleation. Dislocation transformation enabled nano-twins to grow through the primary α/β interface and strain transfer led that deformation twins nucleated in the adjacent primary α grains. With the effects of nano-α phases, LAGBs and twins, the resistance of crack propagation increased and the driving force decreased, and resulted in the low FCGR.Graphic

Geomorphic expression of the Lenglong Ling area, eastern Qilian Shan, and its coupling relationship with the deep structures

Located at the outer edge of the northeastern Tibetan Plateau, the Qilian Shan has long been considered to be the key area to address the issue of how the Tibetan Plateau generates its high topography. However, in spite of the fruitful achievements on the growth pattern and subtle crustal structures of the Qilian Shan, what we know about the regional topography evolution and its relationship with the deep structures are still lacking. In this study, the landscape features of the eastern Qilian Shan and the probable drainage evolution history of the Lenglong Ling, located within the central part of the eastern Qilian Shan, are investigated, based on the multiple geomorphic analyses (i.e., HI and steepness distributions, and the Gilbert and χ metrics). The topographic results show that high HI and steepness values distribute mainly in areas controlled by active faults (i.e., the mountain areas). In addition, the Gilbert and χ metrics suggest that the main Lenglong Ling divide is stable. According to the drainage divide stability criteria, we suggest that the presence of the uplift rate gradient in the eastern Qilian Shan (i.e., with higher uplift in the Lenglong Ling area), which is suggested by the topographic results, has driven the main divide to migrate southward and is now “holding” the divide in place. Taking the previously published magnetotelluric imaging into account, we reveal the coupling relationship between the deep structures and the regional geomorphic features, and further suggest that the Lenglong Ling Fault, or the Qilian‐Haiyuan Fault, makes a difference in regional strain transferring and relief generation.

Block motions and strain partition on active faults in Northeast Tibet and their geodynamic implications

AbstractAn updated GPS velocity field and set of focal mechanism solutions have allowed us to quantify the detailed tectonic deformation of Northeast Tibet. By employing block kinematic modelling, we show how the relative motion of modelled blocks is accommodated by deformation on major fault structures across the region, from the Eastern Kunlun Range to the Qilian Shan, with the slip rate decrease from the centre towards the east in the Kunlun, the Haiyuan and the Altyn Tagh Fault, as well as strain partitioning on these faults. The deflection of both the derived block strains and the focal stress from the west to the east also implies the strain transfer from the strike‐slip shearing to crustal shortening. Combining the different faulting regimes in each block with the distinctive distribution of the strain ratios, our results support a model of diffusive deformation associated with strain partition along tectonic boundary faults.

Strain transfer effect in distributed fiber optic sensors under an arbitrary field

Optical fibers with protective coatings have been used as distributed strain sensors for automated inspection in the construction, operation, and maintenance of various engineering structures. The presence of the protective coatings causes strain transfer effect, which can change the strain measurement of the distributed sensors. This study quantitatively evaluates the strain transfer for distributed fiber optic sensors subjected to an arbitrary strain field for the first time. Theoretical studies are performed to derive closed-form solutions for describing the strain transfer, and high-resolution (sub-millimeter) strain distributions were measured to validate the theoretical study. This study demonstrates that the strain transfer effect is dependent on the strain field in the host matrix, and the derived formulae enable correct interpretation of the strain measurement from the distributed sensor. This study provides theoretical foundations for using distributed fiber optic sensors to accurately measure strain distributions in engineering structures.

Strain Transfer Characteristics of Multi-Layer Optical Fiber Sensors with Temperature-Dependent Properties at Low Temperature

Optical fiber sensors have been potentially expected to apply in the extreme environment for their advantages of measurement in a large temperature range. The packaging measure which makes the strain sensing fiber survive in these harsh conditions will commonly introduce inevitable strain transfer errors. In this paper, the strain transfer characteristics of a multi-layer optical fiber sensing structure working at cryogenic environment with temperature gradients have been investigated theoretically. A generalized three-layer shear lag model incorporating with temperature-dependent properties of layers was developed. The strain transfer relationship between the optical fiber core and the matrix has been derived in form of a second-order ordinary differential equation (ODE) with variable coefficients, where the Young’s modulus and the coefficients of thermal expansion (CTE) are considered as functions of temperature. The strain transfer characteristics of the optical sensing structure were captured by solving the ODE boundary problems for cryogenic temperature loads. Case studies of the cooling process from room temperature to some certain low temperatures and gradient temperature loads for different low-temperature zones were addressed. The results showed that different temperature load configurations cause different strain transfer error features which can be described by the proposed model. The protective layer always plays a main role, and the optimization geometrical parameters should be carefully designed. To verify the theoretical predictions, an experiment study on the thermal strain measurement of an aluminum bar with optical fiber sensors was conducted. LUNA ODiSI 6100 integrator was used to measure the Rayleigh backscattering spectra shift of the optical fiber at a uniform temperature and a gradient temperature under liquid nitrogen temperature zone, and a reasonable agreement with the theory was presented.

Efficient Mechanical Stress Transfer in Multilayer Graphene with a Ladder-like Architecture.

We report that few graphene flakes embedded into polymer matrices can be mechanically stretched to relatively large deformation (>1%) in an efficient way by adopting a particular ladder-like morphology consisting of consecutive mono-, bi-, tri-, and four-layer graphene units. In this type of flake architecture, all of the layers adhere to the surrounding polymer inducing similar deformation on the individual graphene layers, preventing interlayer sliding and optimizing the strain transfer efficiency. We have exploited Raman spectroscopy to quantify this effect from a mechanical standpoint. The finite element method and molecular dynamics simulations have been used to interpret the above experimental findings. The results suggest that a step pyramid-like architecture of a flake can be ideal for efficient loading of layered materials embedded into a polymer and that there are two prevailing mechanisms that govern axial stress transfer, namely, interfacial shear transfer and axial transmission through the ends. This concept can be easily applied to other two-dimensional materials and related van der Waals heterostructures fabricated either by mechanical exfoliation or chemical vapor deposition by appropriate patterning. This work opens new perspectives in numerous applications, including high volume fraction composites, flexible electronics, and straintronic devices.

Methanol electrooxidation on core-shell Ag@Pdx catalysts

The performance of a direct methanol fuel cell (DMFC) is strongly dependent on the catalytic anode. A high-performance anode is expected to offer enhanced intrinsic activity and/or a large electrochemical surface area. Herein, a series of Ag-core/Pd-shell (Ag@Pdx, x = 1,3,5) catalysts are synthesized in which the thickness of the Pd shell is varied. Both tensional strain and electron transfer between the Ag core and the Pd shell are found to affect the intrinsic activity of these Ag@Pdx catalysts. Of these, the Ag@Pd3 catalyst exhibits the best performance for the methanol oxidation reaction (MOR), showing 4.1 times higher mass activity and 2.6 times higher specific activity than a Pd/C catalyst. Furthermore, density functional theory calculations show that this high MOR performance stems from a stronger adsorption of CH3OH and OH on the Pd active sites. This catalyst is thus a promising candidate for inclusion in a high-performance DMFC.

Electrical response with temperature and magnetoelectric coupling of multiferroic nanocomposites

Magnetoelectric Zn0.5Co0.5Fe2O4 – PbZr0.58Ti0.42O3 nanocomposites are synthesized considering chemical reaction process at low temperature and solid-state reaction technique. Structural characterization is performed by X-ray diffraction analysis, which shows two types of nanometric grains coexisting simultaneously. The materials surface morphology displays that the fabrication method is quite effective for preparation of nanocomposites. Crystallite size of different constituent phases is observed to in manometer range. The dependency of temperature on electrical response and dielectric constant of nanocomposites are analyzed with a variation of frequency. The dielectric constant with temperature decreases attributing the thermal excitation of electrons. Moreover, we have evaluated the magnetoelectric coefficient in two configurations (longitudinal and transverse) with increasing applied magnetic field. The coupling coefficient is observed to ∼0.8 mV/cm-Oe in transverse configuration, whereas in longitudinal configuration it is increasing in behavior with measured magnetic field. At room temperature, the observing magnetoelectric coupling may be as a cause of magnetic field dependent strain transfer to the piezoelectric phase to the piezomagnetic phase of the nanocomposites.

Strain transfer characteristics of fiber Bragg grating sensor in aerostat flexible composite skin deformation

In order to improve the strain transfer efficiency of the fiber Bragg grating (FBG) sensor for the deformation monitoring of the aerostat airbag skin, the strain transfer characteristics of FBG for the flexible composite skin monitoring were studied. According to the structural characteristics of the flexible composite skin material, a three-layer strain transfer model of FBG-adhesive layer-skin was established and the strain transfer function was deduced. The strain transfer at each point of the FBG sensor was carried out by analytical and finite element methods. The influence of the relevant parameters of adhesive layer and skin structure on the transmission rate was analyzed and the best packaging parameters of the surface bonded FBG sensing structure were obtained. The research results show that the calculation error of the analytical and numerical methods is less than 5% for the strain transfer efficiency in the middle of the sensor. When the elastic modulus of the adhesive layer is 0.5 GPa, the adhesive length is 40 mm, the adhesive width is 6 mm, and the thickness of the upper and lower adhesive layers are 0.2 mm and 0.1 mm respectively, the strain transfer rate of the fiber grating strain transfer model after packaging parameters optimization can reach 97.04%. It can meet the sensitivity requirements of aerostat airbag deformation monitoring.

Distributed Fiber Optic Sensor-Based Strain Monitoring of a Riveted Bridge Joint Under Fatigue Loading

Riveted steel bridges, which were built in the early 20th century, require their regular structural integrity assessment to avoid any catastrophic failure. This article presents continuous strain monitoring of a single riveted lap joint, which is a representative critical element of riveted steel bridges through an optical frequency domain reflectometry (OFDR)-based distributed fiber optic sensor (DFOS). The aim of this study was to instrument a DFOS on a single riveted lap joint for monitoring the surface and critical strains experienced by the rivet joint under two fatigue loading conditions and also to compare the strain transfer between the two commonly used adhesives for bonding the DFOS. Initially, through finite element analysis (FEA), a location for installing the DFOS was identified, and also a strategy was developed for monitoring the critical location of the joint during fatigue loading. Subsequently, the DFOS was instrumented on the riveted joint at the identified location in two segments, where similar strain levels were expected with the aid of two types of adhesives: cyanoacrylate and epoxy. The strains on the rivet joint were monitored under high cycle fatigue (HCF) for up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times {10}^{6}$ </tex-math></inline-formula> loading cycles with constant stress amplitude and followed by low cycle fatigue (LCF) loading with increasing stress amplitude until the failure of the specimen. The results showed that the DFOS could continuously sense the cyclic peak strain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 223\,\,\mu \varepsilon $ </tex-math></inline-formula> under HCF conditions and a peak maximum strain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 1244\,\,\mu \varepsilon $ </tex-math></inline-formula> under LCF conditions. Furthermore, the internal critical strain on the rivet joint during loading could be monitored with the application of the developed damage monitoring strategy and DFOS strain data. Finally, the DFOS segment bonded using cyanoacrylate measured marginally high strains than epoxy adhesive during the HCF test.

Optical characterization of strain sensing cables for Brillouin optical time domain analysis

Two innovative optical fibre cable layouts designed to improve BOTDA strain measurement accuracy through improved strain transfer efficiency are presented, discussed and tested through experiments, analytical and numerical modelling. The second improved design presents good features to minimize the mismatch between measured and actual strain.

Study on Strain Transfer Mechanism of Three Dimensions Printing Encapsulated Fiber Bragg Grating Sensor

Study on Strain Transfer Mechanism of Three Dimensions Printing Encapsulated Fiber Bragg Grating Sensor

Study on establishing and testing for strain transfer model of distributed optical fiber sensor in concrete structures

When using distributed optical fibers for structural health monitoring, in order to ensure the survival rate of the optical fibers, it is usually necessary to insert the optical fibers into the structure for protection. The coupling performance between the optical fibers and the structure determines the accuracy of the monitoring results. In order to explore the strain transfer law of optical fibers in structures, a strain transfer model based on shear lag theory was established. From analyzing the strain transfer mechanism of optical fibers in structures, the expression of strain transfer efficiency of optical fibers was deduced and the accuracy of the deduced results was verified by comparing with the numerical results. Based on BOFDA technology, two groups of loading tests were carried out to test the strain transfer effect of distributed optical fibers embedded in the test beam. The results have shown that the two ends of the structure were low-efficiency strain transfer zones of optical fibers, which could not fully transfer the strain of the test beam. The middle part of the structure was high-efficiency strain transfer zone of optical fibers, which could completely transfer the strain of the structure. The experimental results were basically consistent with the theoretical deduction. The above research can provide reference for the application of distributed optical fiber technology in engineering structure monitoring.

Development of fiber Bragg grating strain sensor with temperature compensation for measurement of cryogenic structures

It is important to discriminate between mechanical strain and thermal output (apparent strain) in fiber Bragg grating (FBG) strain sensors, due to their sensitivity to both mechanical strain and thermal output. Additionally, when FBG sensors are directly bonded on monitored structures, the transverse effect and the strain-transfer error must be considered to correctly measure the strain. The objectives of this study are to develop pre-tension packaged FBG strain sensors with temperature compensation for use in cryogenic environments and to clarify the performance of the developed sensors in the range from room temperature to 4 K. A developed FBG sensor comprises sensor mounting parts and two FBG that are placed in a row on a single fiber. The one of the FBGs is a strain sensor and the other is a temperature compensation sensor. The developed FBG sensor intrinsically prevents both the transverse effect and the strain transfer error. Experimental investigations are conducted to clarify the performance in the temperature range from room temperature to 4 K for the developed FBG strain sensors. Results confirm that the developed FBG strain sensor demonstrates superior gauge factor stability and a reasonable temperature compensation function. Moreover, the compressive fatigue strength of the developed FBG strain sensor is investigated due to its importance in cryogenic structures that are subjected to cyclic compressive deformations by the repeated operation of cooling and warming processes.

New approach for designing bulk multiferroic composites made of two perovskite oxides with enhanced direct magnetoelectric coupling

The scarcity of single-phase magnetoelectric multiferroics has motivated active research towards the design of composites where polarization and magnetization are coupled through elastic strain at their interfaces. Up to now, most of bulk multiferroic composites are made of immiscible constituents that thus suffer from weak interface connectivity between them. Here, we propose an approach for designing particulate composites with constituents of perovskite ABO3 structure that exhibit solid solubility, by acting on the lowering of the sintering temperature. We show that a BiFe0.95Co0.05O3–PbZr0.52Ti0.48O3 multiferroic composite with improved magnetoelectric coupling can be formed before a solid solution is reached. A Bi-rich interface promotes elastic strain transfer between the two constituents resulting in twice stronger direct magnetoelectric coefficient compared to pure BiFe0.95Co0.05O3. These findings provide an easy and effective strategy for producing upgraded and original multiferroic composites made of constituents with the perovskite structure, known to host a wide variety of functionalities.

Structural Behavior of Hollow Reinforced Concrete Beams: A Review

This paper reviews some experimental and numerical results about the hollow reinforced concrete beams (HRCB). Any subtraction in concrete quantity within the structural members without a considerable lack in load carrying capacity represents a common research trend nowadays due to the decrease in sections dimensions, reinforcing steel and lateral inertia forces in severe earthquakes as well as the sustainability gain for the resulting inhibiting of CO2 emission. In addition, the possibility of passing the electrical and mechanical facilities comprises another good feature of such type of structural members. During the traditional beam design process, the tension concrete is considered as strain transfer agent and do not have any role for structural resistance. As a result, longitudinal holes can be made within this area to produce the hollow reinforced concrete beams (HRCB). In this paper some remarkable research works are summarized with the most important conclusions within this field.

Study of Machining Process of SiCp/Al Particle Reinforced Metal Matrix Composite Using Finite Element Analysis and Experimental Verification

In this paper, a two-dimensional orthogonal cutting simulation model of SiCp/Al composite was established. The geometry and material constitutive model of the particle, the matrix, and the interface layer have been modeled respectively. In view of the distribution of the particles in the matrix, this paper proposed respectively a two-dimensional particle random distribution to simulate particles randomly distributed in the matrix. Then, the cutting state of SiC reinforced particles was analyzed, the novel approach was adopted the geometric shapes of SiC particles in this study is taken as an oval shape. Three different locations of SiC particle relative to the cutting tool path were simulated to analyze the cutting state such as particle removal. The interface layer was introduced to the case that the particle was on the cutting path to study the influence on the stress and strain transfer. Through the post-processing of simulation results, the influence of interface property on the composite reinforcement effect was studied quantificationally. Finally, the cutting process of SiCp/Al composite material was simulated. This paper studied the influence on the machined surface morphology, chip morphology, stress distribution, and cutting force of many factors of the cutting speed and the cutting thickness. The single factor orthogonal cutting experiment was designed the influence of cutting speed and feed rate on the cutting force. The cutting force results of the experiment and the simulation were compared through the deviation analysis, which verified the simulation model.

English

Rise of antibiotic resistant Staphylococcus aureus is a higher risk and great concern to global health. Zoonotic transfer of such strains is well documented. Present study evaluated the presence of resistant S. aureus from mastitic Nilli Ravi buffaloes and nasal carriage of milkers. Phenotypic profile of S. aureus isolates was conducted against penicillin, ampicillin, and cefoxitin. PCR analysis revealed presence of blaZ gene and mecA gene from S. aureus isolated from milk and milkers samples. Sequence and phylogenetic analysis depicts the divergence of mecA gene originated from bovine and human but for the blaZ gene, no divergence was detected. The high degree of genetic relatedness among blaZ and mecA genes in bovine and human S. aureus isolates from same farm suggests the potential transfer of antimicrobial resistance genes between buffaloes and milkers, highlighting the importance of one-health approach to promote global health

Fibre Bragg grating sensors for sutural expansion assessment in rapid palatal expanders: an ex‐vivo validation

This study presents the development and validation of a fibre Bragg gratings (FBGs)-based sensor system for the assessment of strain in the midpalatal suture in subjects using rapid palatal expanders (RPEs). The ex-vivo experiments were made by means of positioning two RPEs in a porcine palatal region. The RPEs used were the Hyrax, a tooth-borne expander and MARPE (microimplant-assisted rapid palatal expansion), a bone-borne expander. In order to define the regions in the palatal region for the sensors positioning, a finite-element analysis was performed in a porcine head subjected to the loadings caused by an RPE. In addition, a strain transfer model was used to obtain a correction coefficient that approximates the strain estimated by the FBG to the actual strain in the structure under shear and normal stress. Results show high linearity in the sensors characterisation tests with the advantages of compactness, intrinsic safe operation and multiplexing capabilities of FBGs. In the RPE analysis, a higher strain was estimated in the anterior region, which is in accordance with the simulation and previously reported results, where MARPE showed a higher strain (with an exponential pattern) than Hyrax as the number of activations increase.

Formation of Coherent 1H-1T Heterostructures in Single-Layer MoS2 on Au(111).

Heterojunctions of semiconductors and metals are the fundamental building blocks of modern electronics. Coherent heterostructures between dissimilar materials can be achieved by composition, doping, or heteroepitaxy of chemically different elements. Here, we report the formation of coherent single-layer 1H-1T MoS2 heterostructures by mechanical exfoliation on Au(111), which are chemically homogeneous with matched lattices but show electronically distinct semiconducting (1H phase) and metallic (1T phase) character, with the formation of these heterojunctions attributed to a combination of lattice strain and charge transfer. The exfoliation approach employed is free of tape residues usually found in many exfoliation methods and yields single-layer MoS2 with millimeter (mm) size on the Au surface. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS) have collectively been employed to elucidate the structural and electronic properties of MoS2 monolayers on Au substrates. Bubbles in the MoS2 formed by the trapping of ambient adsorbates beneath the single layer during deposition, have also been observed and characterized. Our work here provides a basis to produce two-dimensional heterostructures which represent potential candidates for future electronic devices.