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The primary purpose of this paper is to analyze the overall behavior of fractional Maxwell model. The approach used in our study is known as the combined Caputo fractional derivative with pioneer work: the extension Laplace transform (ELT) which broaden the lower limit of the classical Laplace transform. Through the ELT and the Stehfest method, we obtain the strain response of the fractional Maxwell model with different parameters. It is concluded that the obtained results show the variation trend of strain response in a more accurate way.

In this work, we report a giant strain (0.42%) in lead-free ceramics of (1–x) (0.79Bi0.5Na0.5TiO3–0.20 Bi0.5K0.5TiO3–0.01NaNbO3)–xSrTiO3 with x=0.03. Most importantly, ultra-high temperature stability was simultaneously achieved under this giant strain with the variation less than 10% in the range of 20 °C and 140 °C. Systematic temperature dependent Raman spectra measurements and Ginzburg–Landau–Devonshire thermodynamic theory analysis revealed that the intrinsic lattice strain and electric field induced relaxor-ferroelectric phase transition provide reverse strain response with the increase of temperature, jointly conducive to the ultra-high temperature stability of strain property. These materials are extremely competitive in practical application of actuators.

Systems biology and synthetic biology are increasingly used to examine and modulate complex biological systems. As such, many issues arising during scaling-up microbial production processes can be addressed using these approaches. We review differences between laboratory-scale cultures and larger-scale processes to provide a perspective on those strain characteristics that are especially important during scaling. Systems biology has been used to examine a range of microbial systems for their response in bioreactors to fluctuations in nutrients, dissolved gases, and other stresses. Synthetic biology has been used both to assess and modulate strain response, and to engineer strains to improve production. We discuss these approaches and tools in the context of their use in engineering robust microbes for applications in large-scale production.

It is expected that the vortex-induced vibration response of long flexible tubular structures exposed to a shear current will consist of multiple modes of standing and traveling waves simultaneously. The vibration characteristics of traveling wave caused by VIV and its effect on the vibration form for a flexible pipe model are presented in this paper. Two methods are proposed to reveal the characteristics of standing and traveling waves from the perspective of an instantaneous illustration and a time-averaged statistical analysis separately. The first is associated with the adoption of an illustration method depending upon an instantaneous local upper envelope to identify the dominance of the standing or traveling wave. It is found that the in-line and cross-flow wave types show synchronization in that the wave types are mostly changeless or occasionally transform from one type to the other nearly simultaneously. In both the in-line and cross-flow directions, it is evident that the vibration response is not dominated by the standing wave characteristics but can often be characterized by the alternate presence of a traveling wave and a hybrid standing-traveling wave. The second method is associated with the adoption of the significant strain peak concept proposed to estimate the occurrence of the peak strain response and fatigue damage risk. It is found that the strain peak value attributed to in-line static strain accounts for a large proportion of the final equivalent significant strain peak near the pipe end with high reduced velocities, especially when the flow velocity is high. With the occurrence of a hybrid pattern of standing-traveling wave for higher velocities, the distribution of the significant cross-flow strain peak becomes uniform and its corresponding wave shape is apt to be flat.

The technical feasibility of commercial gas production from microbially enhanced coalbed methane (MECBM) reservoirs can be divided into two broad categories: microbial treatment procedures and reservoir suitability. At this time, studies investigating the changes in reservoir-scale properties of coal as a result of bioconversion are lacking. This paper, first of a two-part series, presents the experimental work aimed at investigating the changes in sorption-induced strain response of coal to helium and methane flooding as a result of bioconversion. The strain and its variation, critical to producing methane after bioconversion, were established for coal treated for three periods, 15, 30 and 60 days. The results indicated a softer coal post-bioconversion which, in turn, resulted in inelastic strain with initial helium injection. However, past this initial compression, the bioconverted coal behavior was similar to untreated coal during continued helium injection/depletion. Methane flooding resulted in decreased sorption-induced shrinkage post-treatment, the decrease in Langmuir pressure and volume constants becoming larger with continued treatment. The observed results were used to understand the changes in coal structure for production of biogenic coalbed methane (BCBM) from depleted CBM reservoirs, recharged with methane using the bioconversion technology. The second part presents a detailed analysis of the experimental results to evaluate the behavior and performance of BCBM reservoirs.

In this study, a Johnson–Cook model was used as an example to analyze the relationship of compressive stress-strain response of engineering materials experimentally obtained at constant engineering and true strain rates. There was a minimal deviation between the stress-strain curves obtained at the same constant engineering and true strain rates. The stress-strain curves obtained at either constant engineering or true strain rates could be converted from one to the other, which both represented the intrinsic material response. There is no need to specify the testing requirement of constant engineering or true strain rates for material property characterization, provided that either constant engineering or constant true strain rate is attained during the experiment.

A dent is a common type of defect that occurs during pipeline service. A dented region on a pipe usually creates a strong stress concentration that may become a threat to the safety and integrity of the pipeline. Therefore, such issues are major concerns for pipeline managers. To investigate the strain history behaviour of a dented steel pipeline subjected to increasing internal pressure, a full-scale experimental burst test was performed, and a nonlinear finite element method was used to compare the numerical and experimental results in this study. The paper first discusses the test specimens and test results. Then, the finite element numerical results are verified using the experimental measurement results. Subsequently, the strain behaviour at measurement points and the deformation behaviour of the test pipes were analysed in detail. Furthermore, a sensitivity analysis of strain in the axial and circumferential directions from the dent centre was performed. Deformation analysis reveal that an outward convex phenomenon occurred in axial shoulders on both sides of the dent when the Pipewall Yield Pressure reached. Test results and finite element analysis show that the strain in the dented regions changes rapidly and sharply with a large range, which can easily lead to fatigue under operation pressure for an unconstrained dent.

A multiscale experimental approach is introduced that facilitates correlating globally applied stress to the local material response at yarn scale. Using a high-resolution optical digital image correlation , low and high strain zones in off-axis woven composite samples loaded in uniaxial tension are identified and the corresponding full-field strains are quantified. The local strain response quantified over low and high strain domains are used along with the continuum scale deformation to establish a correlation between global and local deformation behavior as a function of fiber orientation. In addition, global stress-local strain curves are extracted for low and high strain domains at different fiber orientation angles. A simple plasticity model in conjunction with the obtained stress-strain curves is implemented and utilized to develop a phenomenological model that enables correlating global stress with the locally developed strain at different locations in a composite specimen subjected to off-axis tensile load .

Extending blades of wind turbine in service is the most effective method for increasing energy production. Adhesively bonding technology increases less mass and has simpler operation process, which is more suitable for extending blades in service. But unsteady aerodynamic loads on the blades due to stochastic turbulent inflow may lead to fatigue damage and even failure. This paper presented a study on strain response and fatigue life of adhesively bonded extended composite wind turbine blade suffering unsteady aerodynamic loads. Firstly, a loading method that applies periodic distributed aerodynamic loads on the blade was proposed to accurately simulate the unsteady distributed loads on the real extended blades in service. Secondly, strain response behaviors to unsteady aerodynamic loads and strain distribution behaviors in the adhesively bonded area were revealed. Finally, fatigue damage was predicted with unsteady aerodynamic load spectrums, rainflow cycle-counting algorithm, Goodman diagram and Miner's linear superposition principle. Based on the findings obtained from this study, the feasibility of adhesively bonding technology for extending blade was affirmed and a few potential future directions of study were addressed to reduce the risk of adhesively bonded structures.

This paper introduces a new method for quantifying the morphological evolution of the strain response envelope (SRE). The Fourier series approximation was used to trace the morphological characteristics of SREs. Two SREs computed via numerical simulations using the Modified Cam Clay (MCC) model and three SREs obtained from stress-probing experiments on Chicago clay were used to validate the proposed method of Fourier series approximation. The results show that using a harmonic number of 1 or 2, the target shape of the SRE can be approximated within a 10% error.

A dent is a typical defect found in oil and gas pipelines and poses a significant threat to their safety and integrity. In this study, the buckling behavior and limit strain capacity of pipelines with kinked dents under bending moment loads were investigated. First, four-point bending tests of full-scale pipelines with kinked dents were conducted in a laboratory, and the critical buckling load and strain response of the pipelines during buckling failure were tested. The test results revealed that the existence of kinked dents, specifically those with large depths, could weaken the bending resistance of the pipelines. During the buckling process of the pipeline, a considerable compressive strain was generated at the bottom center of the dent, which was considerably higher than the strain value at the corresponding position of the intact pipeline. However, the strain at both axial sides of the dent gradually changed from compressive strain at the initial bending stage to tensile strain after buckling failure. Then, nonlinear finite element (FE) models of buckling failure for pipelines with kinked dents under bending moment loads were developed, and the reliability of the FE models was verified through comparison with the test results. In addition, a parametric sensitivity study was conducted to determine the effect of parameters, such as dent depth, dent angle, diameter-to-thickness ratio of the pipe, and yield ratio of the pipe steel, on the compressive strain capacity of the pipeline. Finally, based on a large number of FE simulation results, a model for predicting the buckling compressive strain capacity of pipelines with kinked dents was developed, which can be used for evaluating buckling instability failure of pipelines with kinked dents subjected to bending moment loads.

Experiments were performed in this study to investigate the influence of damage caused by low-velocity impact (LVI) and shear after impact (SAI) behavior of grid stiffened composite panels . Two positions were subsequently impacted with the same energy and the mechanical response curves were analyzed. Significant stiffener/skin debonding of specimens can be observed even if the impact points were far away from the stiffener . The SAI experiments were conducted with a comparison of shear on virgin specimens. The results demonstrated that the buckling modes of grid stiffened stiffener were the superposition of local buckling and global buckling. According to the strain response and failure modes, the delamination propagation after stiffener fracture was the trigger leading to the failure and the stress concentration near the impact point changed the failure path of skin.

Constrained dents normally cause serious plastification on the pipe under internal pressure due to the restraint of the indenter. Therefore, in this work, the strain response of the API 5 L X80 (referred to as X80 in the remainder part) steel pipeline containing a constrained dent was investigated. Firstly, the formation process of the constrained dented pipeline was numerically simulated by establishing a 3D finite element (FE) model. The model was then verified against the test results of other researchers. The validated model was employed to investigate the equivalent plastic strain distributions of the constrained dent created during the pipe construction and pipe operation stages. Finally, an extensive parametric study was conducted to examine the effects of the internal pressure, dent depth, diameter-to-thickness ratio, indenter size and shape on the strain response of the constrained dented pipe in detail. The results show that the maximum equivalent strain of shallow dents locates at the pipe inner wall at the dent center. As the dent depth increases, the maximum strain position deviates from the dent center and moves outwards along the pipe circumferential direction. Compared with the constrained dent formed during the pipe construction period, the maximum equivalent strain of the in-service constrained dented pipelines is larger under the identical dent depth. The maximum strain increases significantly as increasing the dent depth and internal pressure. It is noted that the wall thickness has a greater influence on the equivalent plastic strain distributions of the constrained dented pipe than that of the pipe diameter. The equivalent plastic strain caused by a small indenter is more serious than the large one due to the high strain concentration. It is noteworthy that circumferential dent (dent length is less than dent width) can be considered as the most severe form of dent defects on the pipe in comparison to the axial dent (dent length is greater than dent width) and dome dent (dent length is approximately equal to dent width).

An approach of composition modification in (Bi,Na,Ba,Sr)(Ti,Nb,Zr)O3 (BNSTNZ)–modified 0.65Bi1.05FeO3–0.35BaTiO3 (BF35BT) piezoelectric materials was investigated. Introducing BNSTNZ into BF35BT ceramics led from the normal-ferroelectric to relaxor-ferroelectric- phase. At the optimum composition, large dynamic piezoelectric coefficient (d33*) of 583 pm/V under the applied field of 5 kV/mm and relatively high static piezoelectric coefficient (d33) of 135 pC/N with high maximum temperature (Tm ≤ 400 °C) were obtained. The unipolar strain and d33* of BNSTNZ into BF35BT ceramics with x = 0.005 increased up to 0.251% and 718 pm/V at 90 °C. The remarkably enhanced field-induced strain response of BF35BT-based compositions is believed to be attributed to the optimum grain size, high tetragonality and the ferroelectric-relaxor phase coexistence. It is noted that this composition can be a favorable lead-free candidate for high-temperature piezoelectric applications.

Recent advances in concrete technology and construction have promoted an increasing utilization of concrete in fatigue-critical structures, such as wind turbine towers. While research into concrete fatigue is not a new topic and has been going on for several decades, a large majority of this research has primarily been focused on the determination of concrete fatigue capacity. However, understanding and advancing concrete fatigue behavior (e.g., fatigue stress vs. strain response) has received limited attention, even though this is also crucial, especially considering the inherently nonlinear behavior of concrete. To address this knowledge gap and further advance our understanding of concrete fatigue behavior, an experimental investigation consisting of uniaxial compressive fatigue testing of concrete cylinder specimens until failure was undertaken, and axial strains were recorded throughout the duration of fatigue loading. The behavior and evolution of concrete axial strains, including the rate of accumulation of strains, through the fatigue loading process were extensively analyzed and are reported. Additionally, the influence of key parameters, such as peak stress levels and number of cycles to failure, on peak strain evolution were investigated and are described. Magnitudes of peak axial strain at the end of the stable strain accumulation phase, as well as at failure, are also reported, and recommendations are made for estimating strain magnitudes at these critical junctures when conducting fatigue analysis and design. The results will help advance the understanding of concrete axial strain behavior under compressive fatigue loading. The results also provide guidelines for estimating the magnitudes of concrete strains under fatigue loads, which in turn will be beneficial to designers, as it allows them to also consider structural performance during the analysis and design of fatigue critical concrete structures.

The collapse mechanics and ultimate strength of a stiffened plate with pitting damage are investigated experimentally with specimens with circular shaped holes representing the pits in the plate. A series of compressive tests has been conducted to investigate the effect of pitting corrosion, including the initial imperfections. The pit location, pit diameter and pit depth are examined to determine the influence of the pitting on the ultimate strength. The experimental results of load-displacement relationship, the strain response and the ultimate strength under compressive loads are analysed. The ultimate strength reduction is related with the degree of pitting or volume loss.

The collapse mechanics and ultimate strength of crack damaged stiffened plates are investigated by testing stiffened plates with an initial crack. A series of stiffened plates with initial distortions and with a crack are subjected to in-plane compression until achieving their ultimate strength. The crack position, length and the angle between the crack and longitudinal stiffener are changed for determining the influence of the crack on the plate ultimate strength. The ultimate strength and the strain response of the panels are reported. Finally, the ultimate strength reduction related with the presence of the crack and the failure mode are discussed for establishing a damage tolerant procedure for the design of ship structures.

The development of all-steel tube-in-tube buckling controlled brace (TinT-BCB) is presented. The efficiency of the TinT-BCBs is evaluated experimentally and numerically. The cyclic behavior and fracture life of TinT-BCBs was first investigated through physical testing, followed by FE-based simulations revealing the inherent correlation between fracture and peak cyclic strain in load-bearing braces. The cyclic strain in plastic zones was recorded up to 0.02 strain range during the cyclic tests, enabling the study to use the recorded strain in verifying the FE simulation models. The strain response of plastic zones was captured by the FE simulation up to fracture in conventional large-size braces. The paper concludes that (1) the TinT-BCB, developed based on the buckling-controlling concept, has demonstrated stable and symmetrical cyclic response, with global and local buckling controlled up to 0.035–0.04 story drift ratio; (2) the TinT-BCB is proven to be effective in elongating cyclic fracture life of conventional CBF from 2% SDR to 3.5–4% SDR by adding simple buckling controller. The cost for adding the buckling controller is low in comparison with the substantially increased lateral strength and energy dissipation capacity; and (3) the efficiency of the TinT-BCB in improving overall cyclic behavior in general and elongating fracture life of braces in particular is attributed to its ability in controlling highly concentrated strain in plastic zones of conventional braces. By spreading the concentrated strain demand throughout the entire length, the buckling controller is shown to reduce excessive peak strains in conventional braces by 7–8 times.

The relationship between electrocaloric effect (ECE) and electrostrictive strain over a broad electric field was studied in (1-x)(Sr 0.7 Bi 0.2 )TiO 3 +x(Na 0.5 Bi 0.5 )TiO 3 relaxor based lead-free ceramics, where the electric field induced strain can reach the level of 0.28% at 12 MV/m. The experimental data revealed that the composition with highest strain response also generated the largest ECE near room temperature, e.g., ΔS=3.6 J kg −1 K −1 and an adiabatic temperature change ΔT=2.4 K at 13 MV/m. This research provides an effective approach for designing new ECE materials.

The beam-column connection, called ‘Que Ti’, is the key component of historic Tibetan timber buildings to transfer shear, compression and bending loads from one structural element to another. This kind of connections can reduce the internal forces and improve the structure’s ability to resist earthquakes. Its structure is very complicated and there is little information about the behaviour of this kind of semi-rigid connections. In this paper, a temperature-based response sensitivity method is proposed to identify the connection stiffness of the ‘Que-Ti’ in typical historical Tibetan buildings from temperature and strain response measurements. The semi-rigid connection is modeled as two rotational springs and one compressive spring. The temperature is treated as a measurable input and the thermal loading on the structure can be determined from the temperature variation. The numerical results show the method is effective and reliable to identify both unknown boundary conditions and the connection stiffness of the structure accurately even with 10% noise in measurements. A long-term monitoring system has also been installed in a typical historical Tibetan building and the monitoring data are used to further verify the proposed method. The experimental results show that the identified stiffnesses by the proposed method are consistent with that by finite element model updating from ambient vibration measurements.

The obvious conflicts between large piezoelectricity and high strain could be solved by adding new components in BNT. Moreover, this urgent problem has been solved and induced a large strain as well as a high piezoelectricity in BNT. Large normalized strain ( d 33 * =526–597 pm/V) and high strain (0.342%–0.388%) were achieved at the composition range of 0.0025≤x≤0.0050, suggesting that such a system is a promising lead-free candidate for electromechanical actuator applications. Furthermore, high d33 values of 141–204 pC/N have also been attained at the above composition range due to adding new components.

textured (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O 3 (BCZT) lead-free piezoelectric ceramics were fabricated by templated grain growth using plate-like BaTiO 3 as template. The effects of orientation degree on the microstructure and resulting changes in dielectric, ferroelectric, piezoelectric, and strain properties were systematically investigated to develop the lead-free piezoelectric materials with an excellent actuating performance. The electromechanical properties were found to increase monotonously with the increase in the degree of texturing and dramatically enhanced for the textured BCZT ceramics in the optimized microstructure compared with randomly-oriented counterparts. Highly textured ceramics showed excellent electromechanical properties of d 33 =462 pC/N, k p =47%, S =0.187%, and S max / E max =621 pm/V at room temperature. These results indicates that the textured ceramics are promising candidates for environmentally friendly actuator devices with high performance.

The strain sensors that are used to evaluate structural members have a limited lifespan and thus have shown limitations to perform long-term structural health monitoring (SHM). This study presents a convolutional neural network (CNN)-based strain prediction technique that allows for structural safety evaluations in case of absence or defect of strain sensors. In the proposed method, CNNs were used to establish a relationship between the dynamic structural response and the strain response measured in the structure. A number of dynamic structural responses and the structural member’s strain response that are measured before the strain sensor malfunctions are used as input data and output data, respectively, to train the CNNs. The trained CNNs can estimate the strain and evaluate the structural safety even when the later strain measurement response cannot be used. Dynamic acceleration and displacement responses are used as input data in the two CNNs presented in this study, called CNN_A and CNN_D respectively. A numerical study of a beam-like structure and an experimental study which includes shaking table tests on a reinforced concrete frame specimen were conducted to confirm the validity of the strain predictions by the proposed method with CNN_A and CNN_D. The strain prediction performance of the proposed CNNs is compared in these applications. This study also examines the proposed technique’s strain prediction performance according to the amount of data used to train the CNNs. In addition, this study discusses influences of variations in the number of locations for measuring the dynamic structural responses that are used as the CNNs’ input data on the strain prediction performance.

In this work, a simple fiber Fabry-Perot air-cavity interferometer (FPI) is formed by splicing a 246 μm long hollow core silica tube (HCST) between two single mode fibers (SMFs). In the thermal characterization test, the FPI exhibits limited linear range up to 700 °C in the first cycle of isochronal annealing treatment from room temperature up to 1000 °C. However, after a series of repeated isochronal thermal annealing, the temperature response of the proposed FPI is extended further to 1000 °C with a good thermal repeatability. Meanwhile, the annealed FPI has linear axial strain sensitivities up to 1000 μe from room temperature up to 800 °C. The proposed fiber structure is a potential sensor for high-temperature or stress measurement in aeronautical or metallurgical fields.

The structural fatigue damage caused by vortex-induced vibration (VIV) is one of the most important failure reasons for flexible cylinders in offshore engineering applications. Helical strakes are often employed to reduce the VIV of slender marine structures. Based on a previous experimental investigation, this paper further investigates the effects of the yaw angle on the VIV fatigue damage of a yawed flexible cylinder with or without helical strakes in a uniform flow. Four yaw angles (α= 0°, 15°, 30° and 45°) are considered. The rain-flow counting (RFC) procedure and the Miner-Palmgren hypothesis are adopted to calculate the fatigue damage of the flexible cylinder. The influence of the yaw angle on the strain response, fatigue damage distribution and maximum fatigue damage of the flexible cylinder are investigated and discussed. The fatigue damage levels in the cross-flow (CF) and in-line (IL) directions of the flexible cylinder are obviously reduced by helical strakes. The VIV fatigue damage of the smooth cylinder is nearly independent of the yaw angle, while that of the straked cylinder is extremely sensitive to the yaw angle. As the yaw angle increases from 0° to 45°, the fatigue damage of the straked cylinder caused by VIV increases several orders of magnitude.

Identifying crack stress thresholds of rocks under different loading conditions, e.g. long-term monotonic or cyclic loads, are crucial in the design of rock excavations and underground openings. The evaluation of the performance of damage thresholds, i.e. crack closure, crack initiation and crack damage stresses, for a variety of rocks, is crucial to assess the most suitable method to capture the stages of rock strength degradation for rock having different strengths subjected to different confining pressures expected to in the field. In this study, several uniaxial and triaxial tests on different rock specimens (Uniaxial compressive strengths from 5 to 278 MPa) were performed to investigate the application and performance of different criteria to determine damage threshold values, using their stress–strain response. It was found that the volumetric strain response of the rock is the most promising parameter to identify crack stress thresholds. For the rocks having different strength values and subjected to different confining pressures, on average, ratios of crack closure, crack initiation and crack damage to the peak strength are found to be 0.21, 0.33 and 0.80 respectively. Effect of rock strength on crack closure and crack initiation stress thresholds was found to be negligible. Crack damage threshold, however, increases with a rock strength increase. This was mainly attributed to the brittle failure behaviour of stronger rocks when compared to weaker rocks. In triaxial compressive testing, crack closure partially occurs during rock consolidation and therefore, crack closure stress decreases with confining pressure increase. Furthermore, a limiting effect on the generation and further growing of lateral cracks in the rocks did lead to an increase in the stress to induced crack damage with an increase in the confining pressure. On the other hand, the effect of confining pressure on the crack initiation stress was observed to be different in different rocks.

This study investigated the strain response of different asphalt binders when subjected to multiple creep and recovery cycles. Test was conducted at three altered temperatures (40, 50 and 60 °C) and four stress amplitudes (0.1, 3.2, 5 and 10 kPa). Burgers four element model and a Power law model were used to simulate the measured response. It was demonstrated that the modified binders outperformed the conventional binders at all the test conditions. Conventional binders were found to be highly sensitive to change in stress level and temperature. It was proved from the test results that the traditional Superpave criteria for characterizing rutting behavior of asphalt binders is not appropriate. Both the Burgers and Power model gave poor experimental fit for the recovery domain, mainly for the modified binders. The viscous parameter ηM of the Burgers model correlated well with the non-recoverable creep compliance (JnR) and R value. The modified Power model, as proposed in the study, was in good agreement with the measured creep and recovery response for all the binders. The new model parameter ‘α’ was found to be able to predict the delayed elastic response of the binders. Critical values of ηM and α were assigned corresponding to different traffic levels and suggested as a rutting measuring tool.

In this work 0.94Na 0.5 Bi 0.5 TiO 3 –0.06BaZrO 3 (NBT–BZ) ceramics were prepared by a reactive templated grain growth (RTGG) method using 15 wt% NBT template. The as synthesized NBT–BZ textured ceramics were sintered at 1150 °C for different soaking times (2–15 h) and their crystal structure, microstructure, dielectric, ferroelectric and field-induced strain properties were investigated and compared. Results show that all textured NBT–BZ ceramics have ( h 00) preferred orientation, which increases with increase in the sintering soaking time. No significant change in the depolarization temperature was observed in NBT–BZ textured ceramics with change in the sintered time. However, the field induced strain response increased by 20% when the sintering time was increased from 2 h to 15 h.

This paper presents an experimental investigation into a self-designed single-layer cylindrical explosion containment vessel (CECV) and a new multi-layer CECV composed of single-layer CECV and aluminum foam sacrificial inner lining subjected to non-uniformly distributed internal blast loading. Based on the experimental results, the characteristics of the blast loading acting on the inner wall of the vessel and the strain response of the vessel shell are analyzed through theoretical analysis and numerical simulation. The analysis results show that the pole of the ellipsoidal end cap is the most dangerous position of the vessel when subjected to internal blast loading produced by a cylindrical charge at the geometric center of the vessel. At the same time, the analysis results confirm the possibility of nonlinear modal coupling to cause strain growth in a CECV. For the multi-layer CECV composed of single-layer CECV and aluminum foam sacrificial inner lining, analysis results demonstrate that the inner lining has a certain protective effect on the CECV as a whole, but may play a counteraction on the cylindrical shell portion of the vessel. This study can guide the design and safety assessment of explosion containment vessels.

This research investigated direct tensile stress versus strain response of ultra-high-performance fiber-reinforced concrete (UHPFRC) with various sizes and geometries. The UHPFRC in this research contained 1% macro twisted and 1% micro smooth steel fibers by volume. The effects of gauge length, section area, volume and thickness of the specimens on the measured tensile response of the UHPFRC were experimentally discovered. The different sizes and geometries of specimens did not generate significant influence on the post cracking strength of UHPFRC whereas they produced clear effects on the strain capacity, energy absorption capacity and multiple cracking behavior of UHPFRC. The strain capacity, energy absorption capacity and the number of multiple micro cracks within unit length obviously decreased as the gauge length, section area and volume of UHPFRC specimens increased. In contrast, as the thickness of the specimen increased, different tendency was observed.

Limited experimental data exist comparing the mechanical response of the tibial cortex between fixed and rotating platform (RP) total knee arthroplasty (TKA), particularly in the revision setting. We asked if RP-TKA significantly affects tibiofemoral torque and cortical stain response in both the primary and revision settings. Fixed and RP tibial trays were implanted into analogue tibias and biomechanically tested under axial and torsional loading. Torque and strain response were analyzed using digital image correlation. Fixed bearing designs exhibited 13.8 times greater torque (P0.01), and 69% (P0.01) higher cortical strain than RP designs. Strain response was similar in the primary and revision cohorts. The decrease in torque transfer could act as a safeguard to reduce stress, micromotion and torsional fatigue in scenario of poor bone stock.

This paper presents an analytical approach to predict the uniaxial compression behavior of circular and square reinforced concrete (RC) columns strengthened with reactive powder concrete (RPC) jackets and wrapped with fiber reinforced polymer (FRP). The analytical axial load-axial strain responses of the strengthened RC columns were compared with experimental axial load-axial strain responses. The analytical approach presented in this study conservatively predicted the ultimate axial load of the strengthened RC columns. Also, a parametric study was carried out to investigate key factors that influence the axial load-axial strain response of the strengthened RC columns. It was found that the ratio of the RPC jacket thickness to the diameter or side length of the base RC column significantly influenced the service axial load, ultimate axial load and ductility of a strengthened RC column.

Asphalt concrete materials exhibit nonlinear viscoelastic responses at high stress/strain levels. The traffic loading induces multi-axial stress states within the asphalt concrete pavement structure. Therefore, it is imperative to characterize the nonlinear viscoelastic responses of asphalt concrete under the realistic multi-axial stress states. Available methods in the literature for characterizing the viscoelastic nonlinearity are mostly based on simple uniaxial creep-recovery tests without considering the effect of confinement stress levels. In this paper, the nonlinear viscoelastic properties of asphalt concrete materials are characterized considering the effects of confinement pressure. It is shown that the confinement pressure significantly affects the nonlinear viscoelastic response of asphalt concrete materials. The viscoelastic nonlinearity is characterized as a function of triaxiality ratio in order to capture the combined effects of confinement level and deviatoric stress. Cyclic creep-recovery tests are performed at 55 °C and at different confinement levels. An equation is proposed to relate the nonlinear viscoelastic parameters to the triaxiality ratio based on the test results. The analyses showed that the triaxiality ratio has substantial effect on the nonlinear strain response of the asphalt concrete.

A temperature sensor based on a multimode-singlemode-multimode (MSM) fiber structure has been proposed and experimentally demonstrated. By utilizing the interference between fiber core and cladding modes, temperature measurement is exploited by monitoring the selected resonant dips shift of the transmission spectrum. A high temperature sensitivity of 50.65 pm/oC is achieved at a certain resonant dip, accompanied by a suppressed strain sensitivity of only 0.587 pm/μe. The sensor reveals the advantages of easy fabrication and interrogation, low cost and small axial strain response.

The fatigue behavior of recycled aggregate concrete (RAC) with 100% recycled coarse aggregate (RCA) replacement percentage under uniaxial compression was experimentally investigated in this study. Key quantities, including the residual strain variation, fatigue strain variation and the fatigue modulus of RAC, were calculated and analyzed to correlate the strain response and fatigue damage behavior of RAC. It is found that there exist no obvious differences of compressive fatigue behavior between RAC and natural aggregate concrete (NAC). Based on the experimental results and continuum damage mechanics, a fatigue model relating the fatigue strain variation and the fatigue modulus degradation to the fatigue damage evolution is proposed. Furthermore, RAC with 100% RCA replacement percentage was also tested under cyclic bend loading. It is found that the fatigue life of RAC is lower than that of NAC for the same stress level under cyclic bend loading.

An experimental programme to obtain the behaviour of blind bolted extended end plate joints to circular or square concrete-filled steel tubular (CFST) columns under monotonic loading has been conducted. In order to enhance the strength and stiffness of the connections, the anchorage extensions are provided to the blind bolts to link the connection back into the concrete with the tubular. This paper investigated the effect of the end plate thickness and the column section type on the static behaviour and failure modes of the tested connections. The structural performance of the blind bolted extended end plate connections was evaluated in terms of the moment–rotation relationship, connection rigidity, the deformation pattern and the strain response. The test results showed that the blind bolted extended end plate connection to CFST columns exhibits high strength and stiffness, while its connection rotation capacity satisfies the ductility requirement for earthquake resistance in aseismic region. The experimental studies also demonstrated that the strength and stiffness of the connections can be improved by providing anchorage extensions to the blind bolts, and utilising moderately thick end plates leads to joints approaching full strength for the extended end plate connections.

Electric fatigue tests were carried out on [001]-oriented Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMN–0.32PT) single crystals at different electric fields: lower and higher than the coercive field. For the crystals fatigued at low (1.5 kV/cm) electric field, the polarization fatigue and piezoelectric constant degradation are weak (

Research has been conducted to better understand the effect of fillers in bolted steel connections. In a companion paper, the results of sixteen experiments on bolted steel slip-critical connections with fillers are presented along with proposed design recommendations. In this paper, detailed behavior of the specimens is documented through an examination of deformation and strain response. Additionally, mechanisms are proposed that clarify key aspects of the behavior of bolted connections with fillers, including prediction of slip and shear strengths. A stochastic analysis, using order statistics, is employed to quantify the detrimental effects of multiple possible slip surfaces on expected slip strength. The use of multiple plies and the effects of developing the filler plate are investigated with respect both to the experimental results and the proposed behavioral mechanisms. The results indicate that the use of multiple plies exacerbates the detrimental effects on slip strength and, to a lesser extent, on shear strength. Furthermore, filler development reduces and in many cases eliminates the reduction in slip and shear strengths.

The experimental identification of fatigue damage mechanisms and evaluation of their development rate, based on changes in material respond on cycle loading, has been presented in the work. The research has been conducted on hyper-eutectic cast alloy AlSi8Cu3. The microstructure and fracture analyses were performed. The high cycle fatigue tests were conducted with frequency of 20 Hz under constant nominal stress amplitude with monitoring the strain response of material during the test. The ratcheting was found as the main mechanism of the fatigue damage. It was established that the linear fatigue accumulation law should not be used for fatigue life prediction in case of the tested cast aluminum alloy.

In this paper, strain gauges are used to measure the dynamic response during drop impact. A set of high-speed data acquisition system is used to capture the real-time strain response of critical locations. Finite Element Modelling is used to determine where to place the strain gauges. Two board level drop impact test methods, A and B, are compared by the strain gauge measurements. Results show significant differences in strain amplitude, strain rate, frequency, rebound, and damping. Method B produces higher strain amplitude, stronger rebound, and less damping, while method A produces higher frequency and strain rate. Damping and rebound are important factors for both test methods. The differences of two test methods are due to the contributions from test condition and test board. Combination test were conducted to investigate the contribution of test condition and test board. Results show that test board dominates strain amplitude, frequency, mode and damping, while test condition shows influence on strain amplitude and rebound. Test condition A produces higher strain amplitude, while test condition B produces stronger rebound. Test board A produces higher frequency, while test board B produces higher strain amplitude and less damping. Test board contributes more to the strain amplitude than test condition. Strain rate is dependent on both the test condition and test board.

Lifetime models for both creep and thermo-mechanical fatigue are presented for P23 steel. The models are the result of the joint European RFCS project ALoAS. The creep model, developed for robust creep strain modeling, here adjusted to describe the strain response of the ALoAS data, i.e. P23 pipe material fabricated by TenarisDalmine and plate material heat fabricated by Industeel. The creep modeling range covers 550–660 °C in temperature and 80–180 MPa in stress. The thermo-mechanical fatigue model is adjusted to the acquired data on thick walled P23 pipe material fabricated by TenarisDalmine. The load range covers 20–625 °C and up to 16,000 cycles to failure. A good description of the data has been achieved for both creep and fatigue models.

This paper describes an elasto-plasticity damage model, termed the EPDI model, of the interface between a structure and gravelly soil. The formulations are derived on the basis of a new model framework, with test-basis concepts and assumptions, for a unified description of monotonic and cyclic behavior of such an interface. The model parameters, with physical meaning, are easily determined from a group of cyclic shear tests and a confining compression test. The comparisons of model predictions with the results for a series of tests under varying loading conditions demonstrate that the EPDI model is effective in accurate description of monotonic and cyclic stress-strain relationship of the interface between a structure and gravelly soil with capturing new features, including: 1) shear stress-strain relationship and comprehensive volumetric strain response (e.g., partly dependent on shear strain); 2) volumetric strain response that is dependent on the shear direction; and 3) evolution of behavior of the interface associated with the evolution of physical state.

The response of 4 strains of laying hens fed diets varying in ME with and without Avizyme 1500 (AVI) supplementation was evaluated in a factorial arrangement study. The strains of laying hens (Hy-Line W-36, Hy-Line Brown, Babcock B300, and Shaver White) were fed 3 diets: moderate ME (2,900 kcal/kg), low ME (2,810 kcal/kg), and low ME with AVI for 28 wk commencing at 22 wk of age. No significant effects of diet, strain, or their interaction on feed intake and BW change were observed. Lack of an effect on feed intake was surprising given the different levels of ME. It is hypothesized that the reduced dietary ME was not low enough to elicit a response. Of course, dietary level of ME did change caloric intake among hens, with hens fed moderate ME consuming more calories than those fed low ME with or without AVI. There was an interesting dietary ME × strain interaction effect on egg production (EP). Babcock B300 hens fed moderate ME and low ME with AVI had greater EP compared with the B300 hens fed low ME, whereas the Shaver White hens had a greater EP when fed a low-ME diet compared with feeding a moderate-ME diet or low-ME diet with AVI. Egg weight and egg mass were significantly affected by strain but not by diet ME. Hy-Line Brown and Babcock B300 hens laid eggs with greater weight and mass in contrast to Hy-Line W-36 or Shaver White. Hy-Line Brown eggs were the largest, whereas Shaver White had greatest egg-specific gravity. Strain significantly affected proportions of albumen vs. yolk in the egg. Across all strains, Hy-Line Brown had more albumen percentage, whereas Hy-Line W-36 had higher wet yolk and yolk solids percentages. The low-ME level fed to laying hens may have been too high to evoke an enzyme response to improve energy utilization by birds. This is important, because to obtain an economic benefit, producers would need to know the proper ME level to feed with the supplemental enzymes.

Extensive experimental studies have been conducted and proved the efficiency of bonding fibre-reinforced polymers (FRPs) systems on structural elements such as reinforced concrete (RC) beams. However, the scarcity of experimental data on the FRP-structural member durability when subjected to extreme loading conditions is unanimously recognized. This paper presents an experimental project undertaken in order to assess the durability of RC beams strengthened with carbon-fibre-reinforced polymers (CFRPs). Small-scale beams were loaded in fatigue for various numbers of cycles and load conditions and then tested monotonically to failure. CFRP–concrete joint appears to be altered by the fatigue loading without affecting the ultimate capacity of the beams. Load–deflection curves and strain responses provide an insight on the performance of CFRP-strengthened beams subjected to severe loading conditions.

This paper presents both modelling and experimental test data to characterise the performance of four non-destructive tests. The focus is on determining the presence and rough magnitude of thermal fatigue cracks within the solder joints for a surface mount resistor on a strip of FR4 PCB. The tests all operate by applying mechanical loads to the PCB and monitoring the strain response at the top of the resistor. The modelling results show that of the four tests investigated, three are sensitive to the presence of a crack in the joint and its magnitude. Hence these tests show promise in being able to detect cracking caused by accelerated testing. The experimental data supports these results although more validation is required.

We report on the fatigue behavior of ultrafine grained (UFG) copper obtained by equal channel angular extrusion (ECAE). Cyclic stress–strain response and fatigue life data were determined in fatigue tests conducted in the low-cycle fatigue (LCF) regime. The early stages of the fatigue process were examined in a scanning electron microscope equipped with a small-scale load frame that allowed for in situ fatigue observations. The ECAE route 16E gives superior fatigue performances as it provides for stable cyclic stress–strain response and more homogeneous plastic deformation than routes that are composed of lower number of ECAE passes. Still, the in situ fatigue tests indicated that fatigue damage occurs on a very localized scale, and thus, additional strengthening mechanisms need to be exploited to obtain UFG materials that display enhanced microstructural stability.

Molecular dynamics simulations are used to investigate polymer networks made by either end-linking or randomly crosslinking a melt of linear precursor chains. The resulting network structures are very different, since end-linking leads to nearly ideal monodisperse networks, while random crosslinking leads to polydisperse networks, characterized by an exponential strand length distribution. Networks with average strand length 20 and 100 were generated. These networks were used to study the effects of disorder in the network connectivity on observables averaged either over the entire network or selected sub-structures. Heterogeneities in the randomly crosslinked networks cause significant differences in the localization of monomers, however, neither the localization of crosslinks nor the microscopic strain response are significantly affected. Compared to end-linked networks, randomly crosslinked networks have a slightly increased tube diameter, and as a result a slightly decreased shear modulus, but otherwise identical stress–strain behavior. For the investigated systems, we conclude that the microscopic strain response, tube diameter, and stress–strain relation are all insensitive to the heterogeneities due to the linking process by which the network were made.

A comprehensive comparison of laminate failure models was established to assess the state-of-the-art in laminate modeling technologies on an international level (known as the Worldwide Failure Olympics Exercise) [1]. This paper represents one contribution (Part A) to the Exercise, where predictions for laminate response and failure behavior of various laminates under a broad range of loading conditions are made. A method for predicting the nonlinear stress/strain response and failure behavior of composite laminates is described. Predictions are based on an incremental formulation of a well-established three-dimensional laminated media analysis [2] coupled with a progressive-ply failure methodology. Nonlinear lamina constitutive relations for the composites are represented using the Ramberg–Osgood equation [3]. Piece-wise linear increments in laminate stress and strain are calculated and superimposed to formulate the overall effective nonlinear response. Individual ply stresses and strains are monitored to calculate instantaneous ply stiffnesses for the incremental solution and to establish ply failure levels. The progressive-ply failure approach allows for stress unloading in a ply and discrimination of the various potential modes of failure. Laminate response and failure predictions for 14 different cases are presented. The cases include prediction of the effective nonlinear stress-vs.-strain responses of laminates, as well as, initial and final ply failure envelope predictions under multi-axial loading. Comparison of predictions with actual experimental data will be made in a companion paper to be published in Part B of the Exercise.