Changes In Strain Distribution Research Articles

Analisis Karakteristik Material Baja dengan Metode Digital Image Correlation (DIC)

The use of steel materials in building construction opens new opportunities for sustainable development, as steel exhibits corrosion resistance, durability, and reliability in terms of strength and ductility. Digital Image Correlation (DIC) is non-contact technique in which digital images of the surface of a test object are captured using high-resolution cameras. This study conducted measurements of strain distribution on the specimen's surface using the DIC method throughout the entire tensile testing process. The study particularly focuses on examining changes in strain distribution during the melting phase and the local deformation phase leading to fracture. In this research, a comparison will be made between the load-displacement curves obtained from experimental laboratory testing and the results analyzed using the DIC method for SS400-grade steel material. Based on the results of the tensile test and DIC analysis that have been conducted, conclusions have been drawn in the research. The tensile test results of SS400 steel material with a thickness of 6 mm, 8 mm, 10 mm, and 12 mm meet the quality requirements in the tested specification standards, and the results of the force-displacement curve between the experimental test results and the DIC method obtained a minimum deviation with a value below 10%,. Therefore, it can be concluded that the DIC method exhibits a reasonably good level of accuracy, making it suitable for validating the results of experimental tests.

Prevalence and genetic diversity of rotavirus among children under 5 years of age in China: a meta-analysis.

This meta-analysis was performed to assess the prevalence and circulating strains of rotavirus (RV) among Chinese children under 5 years of age after the implantation of the RV vaccine. Studies published between 2019 and 2023, focused on RV-based diarrhea among children less than 5 years were systematically reviewed using PubMed, Embase, Web of Science, CNKI, Wanfang and SinoMed Data. We synthesized their findings to examine prevalence and genetic diversity of RV after the RV vaccine implementation using a fixed-effects or random-effects model. Seventeen studies met the inclusion criteria for this meta-analysis. The overall prevalence of RV was found to be 19.00%. The highest infection rate was noted in children aged 12-23months (25.79%), followed by those aged 24-35 months (23.91%), and 6-11 months (22.08%). The serotype G9 emerged as the most predominant RV genotype, accounting for 85.48% of infections, followed by G2 (7.70%), G8 (5.74%), G1 (4.86%), and G3 (3.21%). The most common P type was P[8], representing 64.02% of RV cases. Among G-P combinations, G9P[8] was the most frequent, responsible for 78.46% of RV infections, succeeded by G8P[8] (31.22%) and G3P[8] (8.11%). Despite the variation of serotypes observed in China, the G1, G2, G3, G8 and G9 serotypes accounted for most RV strains. The genetic diversity analysis highlights the dynamic nature of RV genotypes, necessitating ongoing surveillance to monitor changes in strain distribution and inform future vaccine strategies.

Electrode pattern definition in ultrasound power transfer systems

We use a high pattern-fidelity technique on piezoelectric electrodes to selectively excite high-order vibration modes, while isolating other modes, in multi-layered through-wall ultrasound power transfer (TWUPT) systems. Physical mechanisms, such as direct and inverse piezoelectric effects at transmitting and receiving piezoelectric elements, as well as wave propagation across an elastic barrier and coupling layers, all contribute to TWUPT. High-order radial modes in a TWUPT system feature strain nodes, where the dynamic strain distribution changes sign in the direction of disks' radii. This study explains theoretically and empirically how covering the strain nodes of vibration modes with continuous electrodes results in substantial cancelations of the electrical outputs. A detailed analysis is given for predicting the locations of the strain nodes. The electrode patterning for creating the transmitter and receiver shapes is determined by the regions where local force and charge cancelation do not occur, i.e., the two modal principal stress components have the same sign. Patterning for creating the electrode shapes is performed by high-fidelity numerical modeling supported by experiments. Using differential excitation on the transmitter side while monitoring transmitted power and efficiency on the reception side at various vibration modes is made possible by the unique nature of TWUPT systems. Due to an improvement in system quality and power factors, it is determined that employing the proposed electrode pattern designs enhances overall device efficiency and active power. The suppression of other modes makes up a filter feature that is paired with the enhancement at the mode under consideration.

Formation mechanism of high-strain bands in commercially pure titanium

In textured α-Ti, band-like high-strain regions at approximately 45° to the loading direction are commonly observed under tensile deformation. Herein, such high-strain regions were called high-strain bands (HSB), and the reasons for the formation mechanism of HSBs were investigated by a uniaxial tensile test and crystal plasticity finite element (CPFE) analyses. First, we conducted a uniaxial tensile test of commercially pure titanium (CP–Ti) with a TD-split texture, where aggregates of (0001) split and incline in the transverse direction, and changes in strain distributions with deformation were observed by digital image correlation. The strain distributions showed that HSBs of approximately 45° to the loading direction were formed from the initial stage of deformation. Second, a geometric model including crystal orientation information was constructed from the crystal orientation map of the CP-Ti specimen obtained by electron back-scattered diffraction, and the cause of the formation of HSBs was investigated by CPFE analysis. The stress–strain relationship and strain distributions obtained by CPFE analysis correlated well with those obtained experimentally, and the HSBs were successfully reproduced. Finally, CPFE analyses were conducted when the loading conditions, critical resolved shear stress (CRSS), or elastic constants were changed. These results show that the HSBs formed from the initial stage of deformation and the distributions formed by elastic deformation changed depending on the elastic anisotropy. However, the distribution of HSBs after plastic deformation was unchanged by elastic anisotropy. This may be because the directions of easy deformation by elastic and plastic deformation coincided. Elastic anisotropy did not affect the distributions of HSBs formed by plastic deformation, and elastic and plastic deformations were predominantly determined by elastic constants and CRSS, respectively. Curved HSBs were also observed when plastic deformation-resistant regions occupied a large area in the specimen. In this case, the distributions of HSBs, caused by elastic deformation did not coincide with those of the plastic deformation.

Digital image correlation (DIC) based damage detection for CFRP laminates by using machine learning based image semantic segmentation

Vision-based damage detection in carbon fiber-reinforced plastic (CFRP) composites can be interfered by such factors as surface texture, stains and lighting. A digital image correlation (DIC) based surface strain monitoring technique, on the other hand, enables to track the change of strain distribution. It is promising to develop a new approach for online structural health monitoring (SHM), in which the DIC strain contours can be scrutinized automatically and the results are no longer substantially subjected to human interference. In this study, a convolutional neural network (CNN) based image semantic segmentation technique is proposed for pixel-level classification of DIC strain field images. A DeepLabv3+ encoder-decoder architecture combined with different feature extraction networks is investigated. The training dataset and validation of the model are obtained through finite element (FE) simulation. The images of quasi-static axial tensile strain field obtained from 2D-DIC are used to test the accuracy and efficiency of the trained CNN model. It is found that use of a pre-trained ResNet-50 CNN model as the backbone network of DeepLabv3+ architecture through a transfer learning algorithm can make the semantic segmentation results reach a mean intersection over union of 0.9236. The prediction accuracy of the semantic segmentation model trained from the FE data is comparable with that of the model trained from the experimental data, which demonstrates that the proposed machine learning approach for DIC measurement is cost-effective.

Skull Sutures and Cranial Mechanics in the Permian Reptile Captorhinus aguti and the Evolution of the Temporal Region in Early Amniotes

While most early limbed vertebrates possessed a fully-roofed dermatocranium in their temporal skull region, temporal fenestrae and excavations evolved independently at least twice in the earliest amniotes, with several different variations in shape and position of the openings. Yet, the specific drivers behind this evolution have been only barely understood. It has been mostly explained by adaptations of the feeding apparatus as a response to new functional demands in the terrestrial realm, including a rearrangement of the jaw musculature as well as changes in strain distribution. Temporal fenestrae have been retained in most extant amniotes but have also been lost again, notably in turtles. However, even turtles do not represent an optimal analog for the condition in the ancestral amniote, highlighting the necessity to examine Paleozoic fossil material. Here, we describe in detail the sutures in the dermatocranium of the Permian reptileCaptorhinus aguti(Amniota, Captorhinidae) to illustrate bone integrity in an early non-fenestrated amniote skull. We reconstruct the jaw adductor musculature and discuss its relation to intracranial articulations and bone flexibility within the temporal region. Lastly, we examine whether the reconstructed cranial mechanics inC. aguticould be treated as a model for the ancestor of fenestrated amniotes. We show thatC. agutilikely exhibited a reduced loading in the areas at the intersection of jugal, squamosal, and postorbital, as well as at the contact between parietal and postorbital. We argue that these “weak” areas are prone for the development of temporal openings and may be treated as the possible precursors for infratemporal and supratemporal fenestrae in early amniotes. These findings provide a good basis for future studies on other non-fenestrated taxa close to the amniote base, for example diadectomorphs or other non-diapsid reptiles.

Microstructural correlation with formability aspects of low carbon steels during deep drawing operations

Mechanical and fluid assisted (hydro-mechanical) deep drawing operations were performed on drawing quality (DQ) and interstitial free (IF) steels at various forming depths. The evolving microstructure in terms of textural developments, in-grain misorientations and residual stresses measurements were significantly different between the two grades and deep drawing processes. In all the deformed microstructures, however, clear formation of near boundary gradient zones (NBGZs) was observed, quantified from electron backscattered diffraction (EBSD) data. The effective presence and extent of the NBGZs appeared to be the primary source of differences in deformed microstructure developments leading to changes in strain distributions between two different forming processes. It was observed that the formation of NBGZ was lower in hydro mechanical deep drawing (HMDD) operations. Moreover, the estimated statistical parameter strain non-uniformity index (SNI) confirmed the development of uniform strain distributions during HMDD operations. The determined correlation coefficient R2 values showed best fit for HMDD operations.

Strengthening Mechanism of Studs for Embedded-Ring Foundation of Wind Turbine Tower

The embedded-ring wind turbine foundations were widely applied in the early development stage of wind power industries because of its properties such as easy installation and adjustment. However, different damages occurred on some embedded-ring wind turbine foundations in recent years. Based on the common damage phenomena of embedded-ring wind turbine foundations, the structural defects and damage mechanisms of embedded-ring wind turbine foundations are analyzed in a gradual way. Cheese head studs are proposed to be welded on the lateral wall of the steel ring to strengthen the connection between the steel ring and the foundation concrete. The foundation pier is elevated 1 m to increase the embedded depth of the steel ring. The circumferential confining pressure is applied on the lateral side of the foundation pier to lead it into a state of pressure. One simplified method is proposed to calculate the contribution of welding studs in this strengthening method. Taking an embedded-ring wind turbine foundation as an example, the numerical analyses for the original foundation and the reinforced one are carried out to compare the stress and strain distribution changes. Based on the numerical results corresponding to the peak and valley value loads, the fatigue life of the concrete and studs are evaluated according to the relevant design codes. The numerical results show that this strengthening method can coordinate the deformation of the embedded steel ring and the foundation concrete by circumferential prestressing and welding studs. The maximum principal stresses of the foundation pier and the fatigue stress range of the concrete around the bottom of the steel ring have been greatly reduced after strengthening. The gaps between the embedded steel ring and the foundation pier are also obviously decreased because of these strengthening measures. The stress concentration phenomena of the concrete around the T-shaped flange have been remarkably improved. The fatigue life can meet the requirements of relevant design codes after strengthening. Therefore, it can be concluded that the safety performance and service life of the embedded-ring foundation can be guaranteed.

Impact of surgical alignment, tray material, PCL condition, and patient anatomy on tibial strains after TKA

Bone remodeling after total knee arthroplasty is regulated by the changes in strain energy density (SED), however, the critical parameters influencing post-operative SED distributions are not fully understood. This study aimed to investigate the impact of surgical alignment, tray material properties, posterior cruciate ligament (PCL) balance, tray posterior slope, and patient anatomy on SED distributions in the proximal tibia.Finite element models of two tibiae (different anatomy) with configurations of two implant materials, two surgical alignments, two posterior slopes, and two PCL conditions were developed. The models were tested under the peak loading conditions during gait, deep knee bending, and stair descent. For each configuration, the contact forces and locations and soft-tissue loads of interest were taken into consideration. SED in the proximal tibia was predicted and the changes in strain distributions were compared for each of the factors studied.Tibial anatomy had the most impact on the proximal bone SED distributions, followed by PCL balancing, surgical alignment, and posterior slope. In addition, the thickness of the remaining cortical wall after implantation was also a significant consideration when evaluating tibial anatomy. The resulting SED changes for alignment, posterior slope, and PCL factors were mainly due to the differences in joint and soft-tissue loading conditions. A lower modulus tray material did result in changes in the post-operative strain state, however, these were almost negligible compared to that seen for the other factors.

Change in Strain Distribution of Cu–35mass%Zn Alloy by Applying Torsional Moment in Cold Upsetting

Change in Strain Distribution of Cu–35mass%Zn Alloy by Applying Torsional Moment in Cold Upsetting

The role of microcracking on the compressive strength and stiffness of cracked concrete with different crack widths and angles evaluated by DIC

In this study, uniaxial compression tests using cracked concrete with different crack widths and angles were conducted. The purpose of this study is to clarify influence of crack angle on the compressive fracture process and to understand the reduction mechanism of compressive strength and tangential stiffness due to a primary crack. In this experiment, the changes in strain distribution at the cutting surface during loading were determined by DIC, with the stress-strain relationship and tangential stiffness change during loading clarified. As a result, it was found that the relationships between compressive strength reduction and crack width change corresponding to crack angle. The reduction of compressive strength due to a primary crack in a direction intersecting with the loading axis (crack angle of 0–60°) is related to microcracks generated by shear deformation in a crack plane with accompanying aggregate interlock and closure of the primary crack. The reduction mechanism of compressive behaviors due to a primary crack parallel to the loading axis (crack angle of 90°) is also related to microcracks around the primary crack. However, the reduction of compressive strength and maximum tangential stiffness are lower in comparison to a crack angle of 60° due to area where the microcracking occurs being smaller due to aggregate interlock and closure of the primary crack occurring at only the crook of the primary crack. Finally, it was found out that the reduction mechanism could be interpreted by generation and propagation of microcracks from the primary crack even if the crack angle varies.

Monitoring and structural analysis of a rehabilitated box girder bridge based on long-gauge strain sensors

Structural rehabilitation is playing an increasingly important role in civil engineering owing to issues with aging infrastructure. In this context, a feasible inspection and monitoring system is needed to draw up effective structural rehabilitation projects. This article presents a case study of a real box girder bridge strengthened via external post-tensioning. With the aim of evaluating the strengthening project and the structural behavior changes, a large-scale strain sensing system containing four sensing areas was installed on the bridge before strengthening, and the static and dynamic strain distribution changes were recorded during annual inspections. The text focuses on discussing and comparing the variations of strain distribution across the bridge before and after strengthening, as well as the yearly changes the rehabilitated bridge has undergone. From the measured strain responses, we accurately determined that the rehabilitated bridge had undergone an unexpected reduction in its flexural stiffness as well as a torsion action. Moreover, finite element analysis results of three different damage models are discussed to understand the detailed cause for this.

Intracranial Pressure Influences the Behavior of the Optic Nerve Head.

In this work, the biomechanical responses of the optic nerve head (ONH) to acute elevations in intracranial pressure (ICP) were systematically investigated through numerical modeling. An orthogonal experimental design was developed to quantify the influence of ten input factors that govern the anatomy and material properties of the ONH on the peak maximum principal strain (MPS) in the lamina cribrosa (LC) and postlaminar neural tissue (PLNT). Results showed that the sensitivity of ONH responses to various input factors was region-specific. In the LC, the peak MPS was most strongly dependent on the sclera thickness, LC modulus, and scleral canal size, whereas in the PLNT, the peak MPS was more sensitive to the scleral canal size, neural tissue modulus, and pia mater modulus. The enforcement of clinically relevant ICP in the retro-orbital subarachnoid space influenced the sensitivity analysis. It also induced much larger strains in the PLNT than in the LC. Moreover, acute elevation of ICP leads to dramatic strain distribution changes in the PLNT, but had minimal impact on the LC. This work could help to better understand patient-specific responses, to provide guidance on biomechanical factors resulting in optic nerve diseases, such as glaucoma, papilledema, and ischemic optic neuropathy, and to illuminate the possibilities for exploiting their potential to treat and prevent ONH diseases.

Time change in strain distribution on the lateral and plantar surfaces of the foot during walking

Time change in strain distribution on the lateral and plantar surfaces of the foot during walking

Magmatic cycles pace tectonic and morphological expression of rifting (Afar depression, Ethiopia)

The existence of narrow axial volcanic zones of mid-oceanic ridges testifies of the underlying concentration of both melt distribution and tectonic strain. As a result of repeated diking and faulting, axial volcanic zones therefore represent a spectacular topographic expression of plate divergence. However, the submarine location of oceanic ridges makes it difficult to constrain the interplay between tectonic and magmatic processes in time and space. In this study, we use the Dabbahu–Manda Hararo (DMH) magmatic rift segment (Afar, Ethiopia) to provide quantitative constraints on the response of tectonic processes to variations in magma supply at divergent plate boundaries. The DMH magmatic rift segment is considered an analogue of an oceanic ridge, exhibiting a fault pattern, extension rate and topographic relief comparable to intermediate- to slow-spreading ridges. Here, we focus on the northern and central parts of DMH rift, where we present quantitative slip rates for the past 40 kyr for major and minor normal fault scarps in the vicinity of a recent (September 2005) dike intrusion. The data obtained show that the axial valley topography has been created by enhanced slip rates that occurred during periods of limited volcanism, suggestive of reduced magmatic activity, probably in association with changes in strain distribution in the crust. Our results indicate that the development of the axial valley topography has been regulated by the lifetimes of the magma reservoirs and their spatial distribution along the segment, and thus to the magmatic cycles of replenishment/differentiation (<100 kyr). Our findings are also consistent with magma-induced deformation in magma-rich rift segments. The record of two tectonic events of metric vertical amplitude on the fault that accommodated the most part of surface displacement during the 2005 dike intrusion suggests that the latter type of intrusion occurs roughly every 10 kyr in the northern part of the DMH segment.

Increasing the performance of energy harvesting in vibration mode shapes

This paper presents a method of design for the energy harvesting of a piezoelectric cantilever beam. Vibration modes have strain nodes where the strain distribution changes in the direction of the beam length. Covering the strain nodes of the vibration modes with continuous electrodes effects a cancellation of the voltages outputs. The use of segmented electrodes avoids cancellations of the voltage for multi-mode vibration. The resistive load affects the voltage and generated power. The optimum resistive load is considered for segmented and continuous electrodes, and then the power output is verified. One of the effective parameters on energy harvesting performance is the existence of concentrated mass. This topic is studied in this paper. Resonance and off-resonance cases are considered for the harvester. In this paper, both theoretical and experimental methods are used for satisfactory results.

Numerical and experimental study of the taper-rolling process for producing a helical blade from a metal strip

In-depth understanding and quantification of the forming characteristics of the taper-rolling process are crucial for process design and parameters determination in order for producing a desired precise helical blade from a metal strip. To this end, a quantitative study is carried out on this process through finite element (FE) simulation and experiment. For the FE simulation, a 3D model is established by handling problems observed in experiments about strip bite, sideways movement, and interference with the rolls and then is calibrated in numerically dynamic effect and validated by experiment. The results show that the plastic hoop and thickness strain components exhibit linearly increasing distributions from the inner to outer rim of the blade, which is a result of the hyperbolic-curve distributed roll gap. Thus, small radial strain that coordinates the deformation in hoop and thickness directions varies from positive to negative across the blade width. As a result, less spread and smaller bending radius have been achieved on the blade than that on the in-plane bent ring under the same conditions. Screw diameter increases with increasing initial position of the strip (H), initial roll gap (S1) and rolls offset (S2), and screw pitch increases with increasing S1 and S2 but is uncertain with increasing H, the rules of which are quantified. The reason is attributed to the change of roll gap and thus the change of strain distribution with varying H, S1, and S2. Then, three forming defects (turning-I, turning-II, and wrinkling) are defined and correspondingly the stable condition is determined as 0.9 <= az/b0 <= 1.6 and t1/t0 ≥ 0.3. Thus, a formable window of H, S1, and S2 for sound formation is determined, within which the forming limit defined as the achievable minimum relative bending radius Rin/b0 is quantified by simulation and validated by experiment.

A strain-based wire breakage identification algorithm for unbonded PT tendons

Tendon failures in bonded post-tensioned bridges over the last two decades have motivated ongoing investigations on various aspects of unbonded tendons and their monitoring methods. Recent research shows that change of strain distribution in anchor heads can be useful in detecting wire breakage in unbonded construction. Based on this strain variation, this paper develops a damage detection model that enables an automated tendon monitoring system to identify and locate wire breaks. The first part of this paper presents an experimental program conducted to study the strain variation in anchor heads by generating wire breaks using a mechanical device. The program comprised three sets of tests with fully populated 19-strand anchor head and evaluated the levels of strain variation with number of wire breaks in different strands. The sensitivity of strain variation with wire breaks in circumferential and radial directions of anchor head in addition to the axial direction (parallel to the strand) were investigated and the measured axial strains were found to be the most sensitive. The second part of the paper focuses on formulating the wire breakage detection framework. A finite element model of the anchorage assembly was created to demonstrate the algorithm as well as to investigate the asymmetric strain distribution observed in experimental results. In addition, as almost inevitably encountered during tendon stressing, the effects of differential wedge seating on the proposed model have been analyzed. A sensitivity analysis has been performed at the end to assess the robustness of the model with random measurement errors.

Grain Boundary Plane Effect on Pr Segregation Site in ZnO Σ13 [0001] Symmetric Tilt Grain Boundaries

As grain boundary (GB) and GB segregation often have significant impact on various properties of polycrystalline materials, their atomic structures as well as the location of segregated dopant should be intensively investigated. We have thus reported several papers about segregation of Pr (praseodymium) in ZnO (zinc oxide) GBs for case study. In this study, we study the atomic structure of Pr‐doped ZnO [0001]/(130) Σ13 symmetric tilt GB, and the results are compared with that for the (250) GB [Sato et al., Phys. Rev. B, 87,140101 (2013)]. Although atomic arrangements of these GBs can be characterized using the same kinds of structural units (SUs), Pr segregation sites relative to the SU vary with GBs. It is suggested that change in strain distribution for different GBs would cause the variation in the segregation sites and Pr would prefer the Zn site of locally highest tension.

Mechanical behaviours and design strengths of single shear bolted connections fabricated with aluminium alloy 7075-T6

In the study, experimental study has been performed to investigate the mechanical behaviours such as ultimate strength and fracture mode of single shear bolted connections with aluminium alloy 7075-T6. Main variables are bolt arrangement and end distance. As a result, the specimens failed by shear-out fracture and block shear fracture. Some specimens with a long end distance were accompanied by curling (out of plane deformation). The curling led to a sudden ultimate strength reduction. Moreover, the change of strain distribution was investigated according to curling occurrence. The reliability of design rules for single shear bolted connection in AAA, AISI and AIJ specification is evaluated through comparison between test results and predictions by each current design standard. Lastly, the strength equations considering curling effect and bolt arrangement were proposed and compared with test results.