Bending Strain Distribution Research Articles

Experimental investigation on adhesively bonded timber-self-compacting concrete composite beams with a thin slab

This study presents an experimental investigation of the failure characteristics, interface slip, strain distribution, and load-deflection response of adhesively bonded timber-concrete composite (TCC) beams fabricated using wet or dry processes. A total of six adhesively bonded TCC beams were produced with a span of 3.2 m and subjected to four-point bending tests. Wet and dry fabricated TCC beams revealed distinct failure modes. The results emphasized the critical role of bonding integrity in ensuring effective composite action and shared contribution mechanism. Wet-fabricated TCC beams exhibited a rigid bonding characterized by a consistent neutral axis alignment and load distribution along the beam span, while dry-fabricated beams experienced interface separation and compromised load-shared contribution, resulting in a significant reduction of the ultimate bending capacity of TCC beams. The outcomes showed that wet and dry TCC beams exhibited comparable load-to-mid-span deflection responses before failure, highlighting uniform behaviour and alignment with fully composite characteristics under the imposed loads. Furthermore, an analytical model for calculating TCC beams is presented and validated. The foundation of the analytical model is established upon the γ-method derived from Eurocode 5. The analytical model is compared with experimental results, highlighting its reliability and precision. Load-deflection responses, bending strain distributions, and ultimate failure loads are accurately captured, affirming the model's capability to anticipate the TCC beam behaviour.

Global formability and bendability of ultra-high strength steels: Effect of mechanical properties on the strain distribution and behaviour in air-bending

Bendability is a key property for ultra-high strength steels, that affects their usability in many industrial applications. Previous research and efforts on improving the bendability of high-strength steels have focused mostly on the minimum bend radius. However, as the minimum bend radius has been deemed insufficient as a measure of bendability, a new approach may be necessary for further advancements in bendability research. In this paper, bendability of nine materials is investigated from a global formability perspective, through bending tests and tensile tests. Digital image correlation is used for strain measurement in both the bending and tensile tests. Linear regression is used for determining the relationships between the obtained tensile test results and bending strain distributions. The findings of this paper show that applying a “local/global formability” approach to bendability could be beneficial for future research, as better description of the bending behaviour can be obtained and the factors affecting certain bending behaviours can be thoroughly investigated.

Longitudinal mechanical response of tunnels under active normal faulting

This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations. Four 1 g condition model tests were reviewed and reanalysed to highlight the key characteristics of the tunnel response under normal faulting: S-shaped deformation and inverted S-shaped bending strain distribution in the longitudinal direction; the main affected zone of faulting is approximately six times the tunnel diameter to the fault plane. A three-dimensional finite element model was also established and verified, followed by a sensitivity analysis of key parameters, including the fault dislocation, dip angle, tunnel rigidity and relative stiffness between the hanging wall and footwall. All results reveal that the longitudinal mechanical response under normal faulting is dominated by a combination of bending, tension, and shearing. Bending and shearing are induced by the large unbalanced rock pressure at the vault in the hanging wall and the inverted arch in the footwall; the value of unbalanced rock pressure is directly proportional to the dislocation but negatively correlated with the dip angle. Although the main part of the tunnel stays in tension, axial compressive strain exists around the fault plane when the dip angle is greater than 70°, which may be related to the ovaling effect of the tunnel. Such an ovaling effect is caused by the compression at the cross-section of the tunnel and may lead to more complicated internal strain.

Bending Strain and Bending Fatigue Lifetime of Flexible Metal Electrodes on Polymer Substrates.

As the technology of flexible electronics has remarkably advanced, the long-term reliability of flexible devices has attracted much attention, as it is an important factor for such devices in reaching real commercial viability. To guarantee the bending fatigue lifetime, the exact evaluation of bending strain and the change in electrical resistance is required. In this study, we investigated the bending strains of Cu thin films on flexible polyimide substrates with different thicknesses using monolayer and bilayer bending models and monitored the electrical resistance of the metal electrode during a bending fatigue test. For a thin metal electrode, the bending strain and fatigue lifetime were similar regardless of substrate thickness, but for a thick metal film, the fatigue lifetime was changed by different bending strains in the metal electrode according to substrate thickness. To obtain the exact bending strain distribution, we conducted a finite-element simulation and compared the bending strains of thin and thick metal structures. For thick metal electrodes, the real bending strain obtained from a bilayer model or simulation showed values much different from those from a simple monolayer model. This study can provide useful guidelines for developing highly reliable flexible electronics.

Direct Visualization of Cross-Sectional Strain Distribution in Flexible Devices.

For flexible devices that inevitably undergo repetitive deformations, it is important to evaluate and control the mechanical strain imposed on the flexible systems for enhancing the reliability. In this paper, a novel experimental method to directly visualize cross-sectional strain distribution in the thin flexible devices is proposed. Digital image correlation (DIC) is effectively adapted by using microscopic images of the cross section for accurate analysis of the microscale deformations. To conduct the DIC strain analysis, speckle patterning is accomplished by using microparticles from diamond-abrasive suspensions with optimized fabrication conditions. First, the cross-sectional micro-DIC analysis is performed successfully for 100 μm-thick substrates. Full-field strain quantification and easy inspection of a neutral plane are demonstrated and compared with results of finite element analysis simulation. Using the presented method, generation of multiple neutral planes is clearly visualized for a trilayer structure with a very soft adhesive midlayer, where strain decoupling occurs by severe shear deformation of the soft adhesive layer. Furthermore, bending strain distribution in a flexible fabric-reinforced polymer (FRP) substrate is also investigated to analyze and predict fatigue fracture in thecomplex inner structure under repetitive bending loading.

Measurement of Bending Strain Distribution in Steel Sheets for Can by Synchrotron X-ray Diffraction

Measurement of Bending Strain Distribution in Steel Sheets for Can by Synchrotron X-ray Diffraction

Mechanical response of buried High-Density Polyethylene pipelines under normal fault motions

Permanent ground deformation is one of the most damaging hazards for continuous buried lifelines. In this paper, numerical models using a Finite Element Method (FEM) were developed to analyze the buried High-Density Polyethylene (HDPE) pipelines subjected to the normal fault motions. The numerical predictions, were compared with those from ASCE Guidelines and with the experimental results obtained from geotechnical centrifuge tests. Moreover, the paper focuses on the effects of the design parameters such as, pipe diameter and thickness, pipeline burial depth, friction angle and density of the soil surrounding the pipe on the maximum bending strain as well as bending strain distribution along the pipeline. The results show that numerical models using a finite element method could produce reasonable predictions. However, the maximum predicted bending strains from the ASCE Guidelines are larger than those from experiments. The pipe deformation mechanisms are also significantly influenced by variation in burial depth, pipe surface characteristics, and backfill type.

Numerical Modeling of Buried HDPE Pipelines Subjected to Strike-Slip Faulting

A systematic study of buried pipeline response to strike-slip faulting was performed wherein advanced computational simulations were conducted in parallel with a series of physical tests employing split-boxes within the geotechnical centrifuge at Rensselaer Polytechnic Institute and the full-scale testing facility at Cornell University. This article describes the numerical modeling and simulations of the experimental tests. The buried pipeline and the surrounding soil are modeled using nonlinear beam (shell) elements and elasto-plastic springs distributed along the pipeline, respectively. Using the finite element method, reasonable predictions are obtained for the axial and bending strain distributions measured during the tests. It is also shown that finite element analysis using pipe beam elements and a modified soil spring model can accurately predict the pipeline seismic behavior due to strike-slip fault rupture, especially when the pipe is subjected to combined bending and tension. In addition, existing closed-form solutions are evaluated.

Modeling analysis of irreversible bending strain distribution and critical current distribution at low bending strains of Bi2223-composite tape

Under applied strain, the damage behavior of bent (Bi,Pb)2Sr2Ca2Cu3O10+δ (Bi2223) composite tape is different from specimen to specimen. Accordingly, the irreversible bending strain and critical current differ among specimens. The present work attempted to reveal the irreversible bending strain distribution and the critical current distribution in low bending strain region. For analysis, a damage model, in which the shape of the core where the current transporting Bi2223 filaments are bundled into Ag, and the damage strain parameter given by the difference between the intrinsic tensile damage strain and residual strain of the Bi2223 filaments, were incorporated to describe the damage evolution in the core and its relation to critical current, was employed. The model was applied to the experimental results measured at limited bending strains. With the present approach in combination with a statistical analysis, the irreversible bending strain distribution and the variation of the critical current distribution with bending strain in low bending strain range were revealed successfully.

A Generalized Method for Calculating Strain for a Circular Cross-Section Specimen Subject to Axial Force and Bending

Abstract A theoretical analysis was performed with multiple-point measurements of the bending strain distribution along the circumferential cross section of a cylindrical alignment cell. A simple and general equation for representing the maximum bending strain was developed to unify the expression of bending strain. Also, both the general equation for the net bending contributions, due, respectively, to the testing machine and the specimen and the equation for the general orientation angle after separation of the testing machine component and the specimen component are provided.

Analysis of the effect of Nb 3Sn strand bending on CICC superconductor performance

Assessment of measured values of the mechanical stiffness of Nb 3Sn cable-in-conduit conductors (CICC) suggests that longitudinal strand bending due to local magnetic loads, transverse to the conductor axis, is sufficiently high to affect the superconductor performance when the magnetic field is over about 10 T. A current diffusion model is applied to simulated current transfer between filaments inside a Nb 3Sn strand in a cable during a T cs (ramped temperature at constant current) measurement. It can be shown that the effect of cyclic bending strains along such strands, with a characteristic wavelength of about 5 mm, can be to produce a drop in the effective ` n' value (the power factor in the voltage–current relation) of the strand as it starts to enter the current sharing region, for electric fields up to 100 μV/m, from 30 to under 10. The effect is dependent on the internal resistivity of the strands as well as the bending strain distribution, but estimates suggest that for transverse resistivity ranges typical of Nb 3Sn strands, both the ` n' value can be reduced and/or the eventual voltage runaway point can decrease. Strands with a high mean stress level (as is expected with a steel jacket) are predicted to be more sensitive than those operating near zero mean intrinsic strain (as with an incoloy or titanium jacket). Although clearly not the only factor, this effect could explain recent experimental results on large coils as well as short conductor samples, where unexpectedly low cable ` n' values have been found. By providing a link between strain and ` n', it also suggests a mechanism by which current (and hence magnetic load) cycling can affect the superconducting performance, as observed in some recent tests.

On the effect of time-dependent deformations on the behaviour of patch-repaired reinforced concrete short columns

This paper reports the results of an experimental study of the effect of time-dependent deformations (such as shrinkage and creep) of concrete repair materials on the ability of patch repairs to contribute to the structural function of reinforced concrete short columns. Prior to repair, strain measurements were taken from loaded columns with preformed cavities; cavity depths varied between columns. One polymeric and one polymer-modified concrete repair material were used for repair, all repairs being performed under zero load. After repair, the distribution of strain was measured from columns subjected to axial service load and from similar columns observed under zero load. Test results indicate that in the short term both the repair materials assist the repaired column to carry load, but in the long term the contribution of the polymer-modified material is reduced substantially while that of the polymeric material is sustained. It is observed that shrinkage of the repair material can induce bending in the repaired column and that this bending increases with patch repair cavity depth. Within the repaired zone, bending strain distributions were linear which would suggest that conventional methods of structural analysis are appropriate for such members.

3-D Elasto-Plastic Finite Element Analyses of Pile Foundations Subjected to Lateral Loading

ABSTRACT This paper is a study based on a number of model tests of free- or fixed-headed pile groups, each composed of nine piles, subjected to lateral loading. The model piles made of aluminum were set in dry sand and laterally loaded. The behaviors of the pile groups were then analyzed by the 3-D elasto-plastic finite element method (FEM), which represents a realistic model to simulate the problem. This model includes elasto-plastic soil behavior with no-tension characteristics, as well as thin frictional elements for slippage on the pile-soil interface. Parameter values for the sand used in the analyses were determined from conventional triaxial compression tests. It is shown that the experimental results can be precisely simulated by the analysis. Furthermore, field tests of a prototype foundation of steel pile group (3 × 3 piles) subjected to lateral loading at its footing were performed. The 3-D FE analyses were conducted to simulate the results. Parameter values for FEM have been adjusted, using the back analysis technique, so as to simulate a load-displacement curve obtained from the single pile loading test. As for the lateral load-displacement relationship and the bending strain distributions along each pile, a good correlation between the experiments and the analyses can be seen in the case of the pile group.

The large deformation analysis of a graphite fishing rod

The purpose of this paper is to present the analysis and design considerations of a graphite fishing rod. A large displacement and small strain analysis was performed and good agreement was obtained with experimental data. In addition, the following was found: The bending strain distribution of the fishing rod varies with the load level and the point which shows the maximum bending strain travels from the tip to butt area with increasing load. The fracture of the fishing rod occurs at the load when the bending strain reaches the smaller of the material failure strain and the critical buckling strain. By the computer aided design method proposed here, analytical predictions of the fracture load and the fracture location were calculated, and good correlation was obtained with experimental data.

Bending of Wide Thick Mild Steel Plate (the 2nd report)

In the first report, stress and strain distribution of a thick steel plate under uniform plastic bending in plane strain state was analysed, and a new method of bending test was proposed.In this paper, bending stress and strain distribution of the plate in plane stress field was analysed and calculated results were compared with experiment ones, and some differences in bending stress and strain distribution between the two cases were discussed.True stress and true strain relations of the material used in these analysis were obtained by tension test of wide thin plate and compression test of short round bar cut from the same material used in bending tests, and these relations were compared with Bridgeman's corrected one.From these results, the following conclusions were obtained.(1) Stress and strain relation by tension test of wide thin plate is more effective rather than Bridgeman's corrected one for analysis of uniform bending in the both cases.(2) Bending strain in compressive side of the plate in plane stress field is a little smaller than one in plane strain field, but slope of bending strain distribution on convex surface of the plate in the both fields is nearly equal at the same bending strain level on convex surface of the plate.(3) Bending stress on convex surface of the plate in plane stress field is smaller than one in plane strain field, and slope of bending stress distribution on convex surface of the plate in plane stress field is a little smaller than one in plane strain field at the same bending strain level on convex surface of the plate.(4) Bending moment of the plate in plane stress field is a little smaller than one in plane strain field at the same bending strain level on convex surface of the plate.