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Although the cage slip of cylindrical roller bearings has been measured and studied experimentally, it is difficult to use current experimental measurement to detect the cage slip of the bearing in actual service or engineering environment. The problem is attributed to the limit on the space for current test instruments that can be installed arbitrarily in laboratory, but not in actual environment. A novel measurement based on strain detection is presented. This measurement can be used to obtain the cage slip of the bearing in service or large bench test. The technique is demonstrated and validated in principle by an experimental system. The system is developed to obtain the strain signal of the outer ring in loaded zone as well as the speed signal of the cage and the inner ring at the same time. Under given test load–speed conditions, the cage slip based on strain detection was compared with the cage slip based on speed detection. Experimental results showed that cage slip ratio curves based on strain responses agreed very well with those based on speed signals. In this way, it is revealed that frequency characteristics of strain signals can be used to obtain internal cage slip of cylindrical roller bearings.

Low-velocity impact (LVI) events in carbon fiber reinforced plastic (CFRP) structures are a major concern as they result in barely visible impact damage which can reduce the strength and stiffness of impacted structure. Detection of such impact events in terms of location and severity will be a significant milestone for aerospace structural health monitoring applications. This can result in well-targeted inspection programs thereby reducing the time and cost of periodic inspections. One of the easy and efficient ways of getting the impact response of a structure is through strain measurement. LVI event monitoring using fiber Bragg grating sensors has evolved as an attractive choice in recent years along with various soft computing algorithms and advanced signal processing techniques. Machine learning techniques such as artificial neural networks and support vector machine are widely used to localize impact events. Getting information regarding the ensuing damage due to LVI event from the strain response is not straight forward as it could involve estimation of intermediate parameters like energy/force of impact, which are further related with probable damage size. This paper demonstrates least square support vector regression-based algorithm to localize impact event in terms of $X$ - and $Y$ -coordinates and its energy on a CFRP plate-like structure and its comparison with other algorithms cited in the literature.

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.

Many benefits can be derived from in situ monitoring of the growth, load response, and condition of human bone. In particular, bone monitoring offers opportunity to advance understanding and designing of osseointegrated mechanical components fixated into bones such as artificial joints and more recently osseointegrated prosthetic limbs. In this study, a bio-compatible wireless inductive strain-sensing system is proposed, which is designed to monitor the growth and strain response of bone-hosting implants. Thin-film circuit fabrication methods based on lithography are adopted to develop a conformable wireless strain sensor designed as a passive resistive–inductive–capacitive circuit. Two forms of strain sensing are designed into the thin-film sensor. First, parallel-plate capacitors fabricated from metal electrodes and a polyimide dielectric layer are introduced to modulate bone strain onto a resonant frequency of the thin-film sensor. A second resonant frequency is introduced in the sensor design to measure circumferential bone growth using a highly nonlinear titanium-resistive element, whose resistance exponentially increases well after 1000 µε under monotonic increasing hoop strain. To ensure the possibility for implantation in animal subjects in future study, the thin-film sensing system is fabricated using mainly bio-compatible polymers (e.g. polyimide) and metals (e.g. titanium and gold). Fabricated prototypes inductively coupled using an impedance analyzer are experimentally tested. Results reveal linear response of the first resonant frequency to low levels of strain with a sensitivity of 4.555 Hz per unit microstrain. The second resonant frequency is sensitive to the resistive fuse with nonlinear fuse behavior initiated above 1000 µε and impedance phase increasing exponentially thereafter.

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.

Qualification for weld strength is typically accomplished using cross weld tensile testing. This style of testing only gives the global behavior of the welded joint and limited materials properties, such as elongation at failure and tensile strength of the material where final failure occurs. Qualification for welded structures usually requires the weldment fails in the base metal. Final failure in cross weld tensile tests in the base metal does not provide information about the actual weld metal and heat affected zone properties. There may be weaker points in the microstructure that cannot be identified in a global cross weld tensile test due to being constrained by surrounding microstructures. Additionally, the traditional cross weld tensile test does not quantify how strain accumulates and transfers in the microstructure at various loads. Using Digital Image Correlation (DIC) in combination with tensile testing, local strain of the various microstructures present across the weld was obtained for ferritic to austenitic dissimilar metal welds (DMW), as well as for a typical “matching” ferritic steel filler metal weld with a higher tensile strength than the base metal. This test also showed where and how strain accumulated and transferred during tensile loading of various welded microstructures. Local yield stresses of each region were also obtained. Obtaining such local properties provides insight into design and service limits of welded components in service.

Fault-crossing tunnels are often severely damaged under seismic dynamics. Study of the dynamic response characteristics of tunnels crossing faults is thus of great engineering significance. Here, the Xianglushan Tunnel of the Central Yunnan Water Diversion Project was studied. A shaking table experimental device was used, and four sets of dynamic model tests of deep-buried tunnels with different fault inclination angles were conducted. Test schemes of model similarity ratio, similar material selection, model box design, and sine wave loading were introduced. The acceleration and strain data of the tunnel lining were monitored. Analysis of the acceleration data showed that when the input PGA was 0.6 g, compared with the ordinary tunnel, the acceleration increases by 117% when the inclination angle was 75°, 127% when the inclination angle was 45°, and 144% when the inclination angle was 30°. This indicates that the dynamic response of the cross-fault tunnel structure was stronger than that of the ordinary tunnel, and the effect was more obvious as the fault dip angle decreased. Analysis of the strain data showed that the strain response of the fault-crossing tunnels was more sensitive to the fault dip. The peak strain and increase in fault-crossing tunnels were much larger than those of ordinary tunnels, and smaller fault dips led to larger increases in the strain peak, consequently, the tunnel would reach the ultimate strain and break down when the input PGA was smaller. Generally, the influence of fault inclination on the dynamic response of the tunnel lining should receive increased consideration in the seismic design of tunnels.

Enhancement of soil engineering properties with biopolymers has been shown recently as a viable and environmentally benign alternative to cement and chemical stabilization. Interest in biopolymer-treated soil is evident from the upsurge of related research activities in the last five years, most of which have been of experimental nature. However, biopolymers have not yet found their way into engineering practice. One of the reasons for this may be the absence of computational models that would allow engineers to incorporate biopolymer-treated soil into their designs. Therefore, the main goal of this study is to numerically capture a macroscopic stress-strain response and investigate the effect of biopolymers on the onset of strain localization. Several diagnostic strain localization analyses were conducted, thus providing strain and stress levels at the onset of strain localization, along with the orientations of the deformation band. Several unconfined compression and triaxial tests on the plain and biopolymer-treated soils were modeled. Results showed that biopolymers significantly improved the mechanical behavior of the soil and affected the onset of strain localization. The numerical results were confirmed by the digital image analysis of the unconfined compression tests. Digital image processing successfully captured high strain concentrations, which tend to occur close to the peak stress.

The aim of the paper was to investigate the helical rolling parameters (a number of passes) for the microstructural modification and the low-temperature impact toughness improvement of the 09Mn2Si High Strength Low-Alloyed (HSLA) steel. In order to achieve this purpose, work spent to crack initiation and propagation was analyzed and compared with patterns of fracture surfaces. The microstructure and impact toughness values were presented in the temperature range from +20 to –70°C. Also, the fracture mechanisms in individual regions on the fracture surfaces were discussed. In addition, a methodology for computer simulation of the process was developed and implemented within the framework of the excitable cellular automata method and its integration with the kinetic theory of fracture. Finally, a theoretical analysis of the effect of grain shapes and orientations on the strain response patterns of a certain meso-volume simulating the material after the helical rolling was carried out.

The influence of pre-strain on the very-low-cycle loading behavior as occurring, for example during roller leveling of sheet metals, is not yet fully understood. A key factor in this context is the stiffness of the material and its changes upon processing. To study the general mechanical property changes during low-cycle loading with small amplitudes for a wide variety of metals, sheet samples of mild steel DC01, pure copper CU-DHP and α-titanium are subjected to low-cycle tension–compression tests. The general influences of pre-strain and the applied strain amplitude are investigated regarding material hardening and changes in the elastic properties. It is shown that all tested materials feature changes in the Bauschinger behavior during cycling. The apparent elastic modulus of the materials decreases with increasing accumulated plastic strain, and the evolution depends on the strain amplitude and the pre-strain. For all three materials, changes in technical springback are present and depend on the loading history.

Athletes participating in contact sports are exposed to repetitive subconcussive head impacts that may have long-term neurological consequences. To better understand these impacts and their effects, head impacts are often measured during football to characterize head impact exposure and estimate injury risk. Despite widespread use of kinematic-based metrics, it remains unclear whether any single metric derived from head kinematics is well-correlated with measurable changes in the brain. This shortcoming has motivated the increasing use of finite element (FE)-based metrics, which quantify local brain deformations. Additionally, quantifying cumulative exposure is of increased interest to examine the relationship to brain changes over time. The current study uses the atlas-based brain model (ABM) to predict the strain response to impacts sustained by 116 youth football athletes and proposes 36 new, or derivative, cumulative strain-based metrics that quantify the combined burden of head impacts over the course of a season. The strain-based metrics developed and evaluated for FE modeling and presented in the current study present potential for improved analytics over existing kinematically-based and cumulative metrics. Additionally, the findings highlight the importance of accounting for directional dependence and expand the techniques to explore spatial distribution of the strain response throughout the brain.

The stress wave force balance is used to measure forces in aerodynamic facilities like shock tunnels and wind tunnels. For accurate measurement of forces, the shape and size of the model and the balance are of importance. The dimensions of the balance mounted inside the model (internal balance) depend on the internal diameter of the model. However, the effect of the length of the stress bar is independent of the model dimensions. This paper describes the variation in transient strain responses at various locations of the stress bar with the variation of the length of the stress bar. Impulse force of 10 N magnitude with 1 ms duration was applied at the tip of a hemispherical model, and the strain responses were observed at various locations along the stress bar. Impulse forces of various magnitudes were applied at the tip of the model, and the strain responses were observed. From the simulation results, it was observed that as the length of the stress bar increases, the strain increases. The strain response was also found to be steady with the increase in length of the stress bar.

In elite ice hockey, concussions occur from a variety of impact sources with different compliances, such as player-to-player collisions, impacts on the ice, boards, and glass. The effectiveness of ice hockey helmets to manage an impact under varying compliance conditions is currently unknown. The objective of this research was to determine the effect of striker compliance on ice hockey helmet performance. Striking caps of different compliance were used to impact a helmeted and unhelmeted Hybrid III headform at three locations. The headform kinematics was measured in linear and rotational acceleration, rotational velocity. The linear and rotational time histories were then used as input to a finite element model of the human brain to determine maximum principal strain response. Helmeted conditions produced significantly lower linear and rotational acceleration, and rotational velocity for the three levels of compliance at the three impact locations. The reductions through the use of a helmet were higher at low compliance in comparison to the other compliance conditions. Considering player-to-player collisions are the most common source of concussion in adult ice hockey, and also the most compliant, these data support the development of helmet technologies that can mitigate impacts under higher compliance conditions to reduce the risk of brain trauma.

Understanding the workings of the novel coronavirus (SARS-CoV-2) is crucial to develop counter therapeutic measures. SARS-CoV-2 gains entry into human cell by binding its receptor Binding Domain (RBD) of Spike protein (S1) to ACE2 receptors. In order to study the effect of mechanical stress on the RBD of SARS-CoV-2, it is modelled as viscoelastic material using Burgers Model. Strain response of RBD under constant stress is analyzed, which gives useful insights into the conformational transitions of RBD at 0K and physiological temperatures. The theoretical underpinning has shown that with increase in the number of stress cycles, the binding affinities of RBD conformational states to ACE2 receptor decrease, decreasing the binding reaction rate between ACE2 receptor and SARS-CoV-2. This analysis gives theoretical evidence that ultrasonic therapy and photo therapy (UV) can be potential candidates to reduce binding reaction rates between ACE2 and SARS-COV-2.

Bridge weigh-in-motion (BWIM) is a technique for detecting overloaded vehicles crossing a bridge without requiring them to stop. It may also be useful for monitoring the structural health of the bridge itself. To achieve accurate weighing of each vehicle, its properties, such as speed, locus, and wheel positions, should be estimated in advance. Conventionally, such information has been obtained via additional sensors such as cameras or via peak-signal detection, using multiple sensors installed across the bridge. This may require substantial computational resources or expensive synchronization between sensors, and the complexity of the overall BWIM system may lead to frequent breakdowns. In this paper, we propose a single-sensor-based BWIM system that utilizes a deep neural network. First, a vehicle’s properties are obtained via feature extraction from the bridge strain response, as sampled by a single strain sensor. BWIM is then performed, using the same response data. The model parameters for vehicle detection are optimized automatically by consulting a surveillance camera while obtaining ground-truth data for a large number of vehicles crossing the bridge. After the model is optimized for the target bridge, the camera may be removed. Our proposal paves the way toward low-cost, compact, and single-sensor BWIM systems.

Purpose To measure the ex vivo pressure-induced strain response of the human optic nerve head and analyze for variations with glaucoma diagnosis and optic nerve axon damage. Methods The posterior sclera of 16 eyes from 8 diagnosed glaucoma donors and 10 eyes from 6 donors with no history of glaucoma were inflation tested between 5 and 45 mm Hg. The optic nerve from each donor was examined for degree of axon loss. The posterior volume of the lamina cribrosa (LC) was imaged with second harmonic generation and analyzed using volume correlation to calculate LC strains between 5 and 10 and 5 and 45 mm Hg. Results Eye length and LC area were larger in eyes diagnosed with glaucoma (P ≤ 0.03). Nasal-temporal EXX and circumferential Eθθ strains were lower in the LC of diagnosed glaucoma eyes at 10 mm Hg (P ≤ 0.05) and 45 mm Hg (P ≤ 0.07). EXX was smaller in the LC of glaucoma eyes with 25% axon loss than in glaucoma eyes with milder damage (P = 0.004, 10 mm Hg). Conclusions The stiffness of the LC pressure-strain response was greater in diagnosed glaucoma eyes and varied with glaucomatous axon damage. Lower LC strains in glaucoma eyes with milder damage may represent baseline biomechanical behavior that contributes to axon loss, whereas greater LC strain and altered radial LC strain variation in glaucoma eyes with more severe damage may be caused by glaucoma-related remodeling.

Strain caused by earthquakes give rise to many earthquake-related hydrological changes. Mechanisms responsible for them are different from place to place, depending on whether the trigger is the static strain or dynamic strain. Theoretic calculation indicates that the great difference in dependence on epicentral distance is robust enough to discriminate them, however, few studies based on direct strain measurements have tested this hypothesis. The 2016 M6.2 Hutubi Earthquake is a reverse event occurred in the northern Chinese Tien Shan, and the coseismic strain responses have been recorded by nine 4-component RZB borehole strainmeters at the distance from near field to far field. The nearest four stations have recorded resolvable static strain responses, and all stations have perfectly recorded the dynamic strain waves. Our result shows that the difference in the dependence on distance is truly reliable to differentiate static strains from dynamic strains, the static strain is of the same magnitude with the dynamic strain in the near field, and as the distance increase to intermediate and far field, the static strain are a few magnitude smaller. Yet the ratio between them is a complex index relating to the rupturing process itself, the tectonic background, and the seismic wave radiation pattern. Furthermore, the calibrated static strain were also used to relocate the fault plane through a grid-search method, and the result shows that the seismogenic fault is surprisingly a high-angle backthrust fault. The determined fault parameters are 279°/70°/87°, which are also consistent with the aftershock distribution. It indicates that the high-angle backthrust in the Chinese Tien Shan are capable of breaking individually. Considering the high vertical displacement, and their abundance inside the Tien Shan orogenic belt, the high-angle backthrust faults may had also played a significant role in building the modern ultra-high relief in Tien Shan.

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.

This paper aims to investigate the seismic behavior of blind bolted end plate composite frames between square or circular concrete filled steel tubular (CFST) columns and steel beams. Two composite frames were tested under a constant axial load on the CFST columns and a lateral cyclic load on the frame. Each specimen composed of CFST columns and steel beams was selected to represent a plan frame in an assembly building. Failure pattern of the type of frames was analyzed to comprehend the structural response. The seismic resistance ability of the blind bolted CFST frames was also estimated in terms of hysteretic curves, ductility and energy dissipation etc. The effect of column section type and end plate type on the type of semi-rigid CFST frames was studied. The test results showed that at the same steel ratio of the column section, the bearing capacity and energy dissipation of square CFST frame were higher than those of circular CFST frame at ultimate state. Strain response of main members in each CFST frame was also estimated. The internal force analysis of the test CFST frames with semi-rigid connections was discussed and evaluated the effect of the bending moment distribution. It was concluded that the novel typed CFST frames exhibited excellent seismic performance and structural internal force redistribution. The experimental studies will be useful for design and application of the blind bolted CFST frames in fabricated steel structure building.

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 .

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.

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.