Behavior Of Sheets Research Articles

Coexistence of Crumpling and Flat Sheet Conformations in Two-Dimensional Polymer Networks: An Understanding of Aggrecan Self-Assembly.

We investigate the conformational properties of self-avoiding two-dimensional (2D) ideal polymer networks with tunable mesh sizes as a model of self-assembled structures formed by aggrecan. Polymer networks having few branching points and large enough mesh tend to crumple, resulting in a fractal dimension of d_{f}≈2.7. The flat sheet behavior (d_{f}=2) emerges in 2D polymer networks having more branching points at large length scales; however, it coexists with crumpling conformations at intermediate length scales, a feature found in scattering profiles of aggrecan solutions. Our findings bridge the long-standing gap between theories and simulations of polymer sheets.

Finite Element Analysis of DP600 Steel Strips in Deformation Tests

DP600 steels are high strength steels used in structural elements of vehicles. However, they can be used in other sectors, but this requires a study in different working conditions, with the help of tools that facilitate the realization of predictions about the mechanical properties of these materials.The "Design Expert" software was used during this research. In it, the combinable input variables are introduced, which in this case are only the size of the pin and the folding angle of the sheet, so that employing simple combinatorial operations tells us how many and which experiments we will have to perform to cover the different possibilities.Simulations have been carried out with the Deform-2D software, applying the finite element method, to know in advance what is going to be the behavior of the metal sheets interacting with the rotating pin, in processes like drawing.

Effect of Magnetic Field on Deformation Behavior of a Steel Sheet in Uniaxial Tension

Abstract This paper discusses the effect of magnetic fields on the tensile properties of high-strength carbon-manganese steel sheets in uniaxial tension. An electromagnetic tool was designed and fabricated such that it produced a constant magnetic field of 0.35 T in the gauge length of a tensile specimen during testing. Experimental measurements of magnetic flux density distribution confirm the model, which is further validated with theoretical analysis. The tensile properties are examined with and without the effect of a magnetic field. A significant improvement is observed in tensile strength and normal anisotropy of the material because of the effect of the magnetic field. Samples were taken from the middle of specimens that were tested with 20 % plastic strain for microstructural investigations using the electron backscattered diffraction technique, and in all cases experiments were performed with and without the magnetic field. Geometrically necessary dislocations maps exhibiting the measure of dislocation density during plastic deformation show lesser accumulation of dislocations at the grain boundaries with the effect of the magnetic field, which indicates hindrance to the movement of dislocations as a result of the severe interaction of dislocations with the magnetic domains. The results also show an increase in grain size and the development of a weak texture for the tested specimens with the applied magnetic field as compared with the specimens tested without the magnetic field. The microstructural findings correlate with changes in the tensile properties.

Revisiting the timing of Saginaw lobe ice retreat and implications for drainage adjustments across southern Michigan, USA

Understanding the behavior of paleo-ice sheets in response to past climate change and land surface processes can provide insights into the interplay between the atmosphere, ocean surface, and the cryosphere, which helps update current climate models and understand landscape evolution. The timing of the advancement and retreat of ice lobes along Quaternary ice sheet margins and their link to ocean surface temperature fluctuation are of particular interest. The Saginaw lobe along the southern margin of the Laurentide Ice Sheet (LIS) was bound by the Lake Michigan and Huron-Erie lobes. It flowed out of Saginaw Bay, across Lower Michigan, and into northern Indiana. All three of these lobes retreated across the region asynchronously, with the Saginaw lobe retreating first. The asynchronous behavior of the lobes allowed the Lake Michigan and Huron-Erie lobes to overprint and alter landscapes once occupied by Saginaw lobe ice.Lacustrine sediments within the Sturgis Moraine, deposited during the Saginaw lobe retreat in extreme southwestern Michigan, yielded optically stimulated luminescence (OSL) ages of 30.1 ± 1.8, 28.7 ± 1.5 and 25.2 ± 1.9 ka. An additional radiocarbon date (22.22 ± 0.8 cal ka) was measured from bryophytes sampled near the base of an ice-walled lake plain atop the moraine. These dates indicate that deglaciation of the Saginaw lobe could have been underway in southwestern Michigan between ∼ 30 and 22 ka, while ice margins of the Huron-Erie and Lake Michigan lobes were further south in Indiana and Illinois. The new dates indicate that southwestern Michigan may have witnessed ice-free conditions four thousand years earlier than previously thought. Moreover, the paleo-hydrological analyses of southwestern Michigan using detailed surficial geology mapping, Lidar-based longitudinal and terrace profiles along meltwater channels, and OSL data indicate that meltwater originating from the Saginaw—Huron-Erie interlobate area drained westward across the Saginaw lobe terrain between ∼ 18.0 to 14.6 Ka ago. The findings call for revisiting the current understanding of the timing and behavior of the southern margins of the LIS and the Holocene landscape evolution in Michigan.

Effect of Fireproof Coatings on the Post-Fire Behavior of CFRP Composite Sheets

This study examines the effect of two self-developed novel fireproof coatings on the fire resistance of carbon fiber-reinforced polymer (CFRP) composite sheets. The post-fire flexural properties were chosen as important indicators of fire resistance. This research involves two distinct fire conditions, the standard fire condition and the large-space fire condition, to simulate general interior fires and large-space fires. The post-fire flexural performance of CFRP sheets coated with two different self-developed fireproof coatings was evaluated through three-point bending tests after fire exposure. The experimental findings demonstrated a significant reduction of up to 80% in the post-fire flexural properties of CFRP sheets without fireproof coatings. However, CFRP sheets coated with fireproof coatings exhibited a substantial enhancement in their post-fire flexural properties. Under the large-space fire condition, the fire-resistance duration of CFRP sheets coated with fireproof coatings of at least 25 mm thickness exceeded 2 h, satisfying the requirements of GB50016-2014 fire-resistance class III (columns), class I (beams), and class I (floor slabs), respectively. Under the standard fire condition, CFRP sheets covered by fireproof coatings of 35 mm thickness exhibited a fire-resistance duration of 0.75 h, meeting the requirements of GB50016-2014 fire-resistance class IV (columns), class IV (beams), and class III (floor slabs), respectively.

Appropriateness of hydrostatic pressure-based modeling for strength differential effect in advanced high strength steel

Although numerous models have been proposed to describe the strength differential (SD) effect, their appropriateness and efficiency in the case of advanced high strength steel (AHSSs) have not been investigated. To this end, this study investigates the SD effect in AHSS using a hydrostatic-pressure-dependent plasticity theory. Although pressure model can effectively predict the SD effect in AHSSs with only one coefficient, the original formulation is experimentally inconsistent in the first quadrant of a yield surface. Hence, this study developed a new formulation to remove the inconsistency in a simple manner and validated the pressure model using new experimental data reported for two recently developed AHSSs: DP980 and MART1500Y. The SD effect is characterized based on monotonic compression and tension tests in three different directions with respect to the rolling direction to obtain the stress–strain curves and r-values. Next, the pressure model is used to predict the plastic behavior of both steel sheets. The parallel transition of flow stress and similarity in r-values between the tension and compression states supports the appropriateness of the proposed pressure-based modeling. Furthermore, these insights substantiate the fact that deformation mechanisms cannot explain the SD effect in both steel sheets. Therefore, complex yield functions that describe the SD effect in general materials are not necessary in the case of AHSS. Additionally, the pressure model is incorporated into a distortional plasticity model for applying it to springback in the bending process. The distortional plasticity model with and without the pressure model is calibrated using tension–compression curves, thereby revealing that the SD significantly affects the calibration. Finally, a U-draw bending experiment and the corresponding finite element simulation are conducted to compare the springback; the results show that considering the SD effect improves the springback simulation accuracy.

Cyclic deformation behavior of non-oriented electrical steel sheets

The cyclic deformation behavior of a fully processed, non-oriented electrical steel sheet is investigated in dependence on loading condition and control mode. Therefore, strain- and stress-controlled fatigue tests are performed to determine cyclic deformation curves in the low- and high-cycle fatigue regimes. With symmetric strain control, continuous cyclic hardening occurs, while in asymmetric stress control with non-zero mean stress, pronounced ratcheting takes place. Depending on the loading condition, the material can exhibit a transitional period with cyclic softening. This effect is present at intermediate amplitudes in the yield point region. It emerges as the dislocation movement is initially inhibited, while at higher amplitudes, cyclic hardening occurs from the very beginning. The evolving dislocation structures are characterized by the predominantly planar slip behavior of the alloy.

Modelling the post‐buckling behaviour of steel sheets under induction heating

AbstractInduction heating has many engineering applications. To accurately describe the induction heating process of thin steel sheets one needs to account for their mechanical deformation. This might strongly affect the magnetic configuration since thin sheets are prone to thermal buckling, leading to large supercritical deformations. We suggest a modelling strategy combining a computationally highly efficient structural mechanical shell description for the thin sheet with a standard continuum model for eddy current and thermal problems through an iterative coupling algorithm. All benchmark problems are solved numerically using the finite element method.

Flexural behaviour of concrete thin sheets prestressed with basalt-textile reinforcement

While the recently emerged textile-reinforced concrete (TRC) composites offer a more durable alternative to conventional reinforced concrete, these composites are susceptible to cracking and high deformations under service loads, which hinders their widespread application for the development of load-bearing structural components. Aiming at addressing this issue, the present paper experimentally investigates the flexural response of non-prestressed and prestressed basalt-based textile-reinforced concrete plates. Basalt is chosen as an emerging low-carbon reinforcement for TRC composites. The first series of tests is focused on non-prestressed TRCs and consists of eleven reinforcement configurations considering the role of reinforcement ratio, position and coating on the flexural behaviour of TRCs. The second series, focused on prestressed TRCs, considered the role of prestressing level (13%, 25% and 35% of the fabric’s ultimate tensile load), releasing time, testing age and coating type on the flexural behaviour.

Investigation on bonding behavior of basalt fiber reinforced polymer (BFRP) sheet reinforced concrete beam

Although basalt fiber reinforced polymer (BFRP) sheet offers promising benefits including environmental friendliness and excellent mechanical performance in concrete reinforcement, its full potential is still hindered by the lack of understanding about their bonding mechanism. Therefore, the comprehensive investigation of the bonding behavior of BFRP sheet reinforced concrete is necessary. This work aims to address the research gap between the analytical design and industrial application of BFRP sheet reinforced concrete due to the complicated bonding behavior. Analytical method, experimental measurement, and numerical simulation are employed to comprehensively investigate the bonding behavior of BFRP sheet reinforced concrete. According to the mechanical model and assumptions of the reinforcement, analytical solutions for interfacial stress and strain are derived. In addition, four-point bending test are conducted on specimens, and multi-view digital image correlation (DIC) technique is used to analyze the deformation on concrete part and BFRP sheet simultaneously. Based on analytical and experimental results, finite element model (FEM) is applied to simulate mechanical behavior of BFRP sheet reinforced concrete beam, and parametric analysis is further conducted. Results reveals that the maximum interfacial stress appears at the end of bonding region so that BFRP debonding at the end is the main failure mode. The strain distribution of BFRP sheet obtained by multi-view DIC indicates that there is an effective bonding region. Besides, strain can be used as a variable to validate numerical model by analytical and experimental results. The validated numerical simulation could be conducted for the internal response study and application design of BFRP sheet reinforcement.

On-line heating rolling behavior of Mg9999 sheets under large single pass reduction

Pure magnesium foil has a great potential for rechargeable magnesium battery anode application, the formation of edge crack and break during Mg sheet rolling highly decreases the yield and thus increase the cost. In this paper, pure magnesium sheets of different thicknesses (0.3 mm, 0.4 mm, 0.5 mm and 0.6 mm) were prepared from 1 mm pure magnesium sheets by on-line heating rolling in a single pass. The edge cracking and breaking behavior of pure magnesium sheets were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), electron backscatter diffractometer (EBSD), energy dispersive spectroscopy (EDS) and laser scanning confocal fluorescence microscope (LSCM). The results show that the number of edge cracks of pure magnesium sheets increases with the increase of rolling reduction. As the rolling reduction increases to 70%, due to the severe edge crack of 0.3 mm thick sheet and the formation of grooves on the magnesium sheet surface, the breaking of pure magnesium sheets occurs. The mechanism of edge cracking and breaking of ultra-thin pure magnesium rolled sheet is discussed.

Local twinning behavior of ZK61m magnesium alloy sheet under multiaxial stress during drawing-pressing with Erichsen test machine

In order to find a more effective method to preset twins and to explore the microstructure and twin evolution of magnesium alloy sheet under multi-axial stress state deformation, drawing-pressing deformation with Erichsen test machine is used as a sheet processing method to process ZK61m magnesium alloy sheet in this experiment. During repeated drawing-pressing deformation, the central area of the plate was subjected to annular tensile and compressive stress. In the process of deformation under unidirectional force, the slip direction of some grains is in hard orientation and it is difficult for the slip to operate, while the annular tensile and compressive stress state will provide the grains with multidirectional slipping options. Electron back-scattered diffraction (EBSD) technique was used to analyze the microstructure of magnesium alloy plates with different drawing-pressing times and different positions from local deformation center to edge. In this study, the complex circumferential force environment will weaken the anisotropy of deformation structure during repeated drawing-pressing, and the effect of prefabricated twins is more obvious. Based on the modified generalized Schmid factor (GSF) analysis, it is easier to show a variety of twin variation behaviors within a grain during Erichsen deformation. After the plate is deformed by Erichsen processing, the mechanical properties of magnesium alloy sheet have also been effectively improved.

Towards the best strength, ductility, and toughness combination: High entropy alloys are excellent, stainless steels are exceptional

Remarkable mechanical properties have been reported for CoCrFeMnNi-based high entropy alloys (HEAs) in recent literature, making these HEAs potentially attractive candidates for future cryogenic applications. However, the damage and fracture behaviour of HEAs is not fully understood yet, especially at low temperature. Here, the mechanical behaviour and fracture resistance of CoCrFeMnNi and CoCrNi sheets are investigated at room and cryogenic temperatures and compared to more conventional alloys. Very good properties were confirmed for HEAs, but outperformed by stainless steels under similar conditions, in terms of ductility, strength, and fracture toughness combination. Exceptional low temperature fracture energy up to 2500 kJ/m2 was found for stainless steels compared to 700 kJ/m2 for HEAs. A predictive model was developed and validated experimentally in order to connect the thin sheet fracture toughness to the strain hardening capacity through separating the necking and damage work spent in the fracture process zone, providing guidelines for further optimization.

Numerical analysis for tangent-hyperbolic micropolar nanofluid flow over an extending layer through a permeable medium

The principal purpose of the current investigation is to indicate the behavior of the tangent-hyperbolic micropolar nanofluid border sheet across an extending layer through a permeable medium. The model is influenced by a normal uniform magnetic field. Temperature and nanoparticle mass transmission is considered. Ohmic dissipation, heat resource, thermal radiation, and chemical impacts are also included. The results of the current work have applicable importance regarding boundary layers and stretching sheet issues like rotating metals, rubber sheets, glass fibers, and extruding polymer sheets. The innovation of the current work arises from merging the tangent-hyperbolic and micropolar fluids with nanoparticle dispersal which adds a new trend to those applications. Applying appropriate similarity transformations, the fundamental partial differential equations concerning speed, microrotation, heat, and nanoparticle concentration distributions are converted into ordinary differential equations, depending on several non-dimensional physical parameters. The fundamental equations are analyzed by using the Rung-Kutta with the Shooting technique, where the findings are represented in graphic and tabular forms. It is noticed that heat transmission improves through most parameters that appear in this work, except for the Prandtl number and the stretching parameter which play opposite dual roles in tin heat diffusion. Such an outcome can be useful in many applications that require simultaneous improvement of heat within the flow. A comparison of some values of friction with previous scientific studies is developed to validate the current mathematical model.

Chad's cabinet of icy curiosities: Sharpening the interpretation of subglacial and ice marginal environments during the LPIA glaciation of the Ennedi Plateau

The Ennedi Plateau in Chad in north-central Africa exposes an outstanding example of a palaeo-ice stream glacial landsystem of late Palaeozoic age, with an assemblage of geomorphological structures of comparable preservation quality to those found in Quaternary deglaciated landscapes. Satellite images and various methods to combine acquired satellite data (e.g. band-ratio technique) have been used to interpret proglacial, ice-marginal and subglacial structures. The main goal of the study is to produce a detailed and more in-depth analysis of newly found structures that enhance our understanding of ice sheet behaviour in the Ennedi Plateau during the LPIA.We report the first known evidence of soft-sediment striated surfaces from outcrop, testifying to the existence of a soft-deformable bed. This deformable bed interpretation can probably be upscaled to explain the extensive swarms of mega-scale glacial lineations mapped previously across the plateau. Furthermore, we identify the first known fully preserved grounding zone wedge (GZW), replete with three-dimensional geometry, in the rock record. This unique structure exhibits a well pronounced slope and a convex topography. Its presence allows the position of the former coastline to be reconstructed as it is assumed that ice streams terminated into a former ocean basin. Building on the studies by Le Heron (2018) and Kettler et al. (this issue), our analyses permit unprecedented insights into the behaviour of a significant, mid-latitude, marine-terminating ice sheet during the LPIA.

Effect of five typical vacancy defects on the tribological behaviors of MoS2 sheet: A molecular dynamics study

The tribological behavior of the defective MoS2 sheet has been investigated under different normal loads by molecular dynamics simulations. Five typical vacancy defects have been introduced to estimate the anti-friction and anti-wear properties of defective MoS2 sheets. The existence of vacancy defects increases the local friction of the MoS2 sheet and accelerates wear failure. The degree of vacancy defect influence on the anti-friction and anti-wear properties of MoS2 is as follows: VMo < VS < VS2 < VMoS3 < VMoS6. The atomic frictional deviation of the a-C tip and the potential energy surfaces of the defective MoS2 sheet have been analyzed to reveal the potential mechanisms of the atomic pinning effect. The enhancements of atomic pinning and energy barrier induced by vacancy defects are the main contributions for the increased local friction in the MoS2 sheet. The S atomic vacancies in the bottom S layer have been further considered. The top layer S atom tends to transfer and fill the bottom S vacancy under a certain normal load of 130nN. The transformation of vacancy defect further increases the surface friction of defective MoS2 sheets.

Ductile fracture of anisotropic QP980 steel sheet by using the isotropic/anisotropic modified Mohr-Coulomb models

The modified isotropic Mohr-Coulomb (iso-MMC) fracture model, which utilizes the Mises yield function and isotropic hardening law, was calibrated through tensile tests on various specimens. The resulting calibrated model was constructed in (η, L, ε¯f) space to represent the isotropic fracture locus of QP980 steel sheet. Subsequently, this calibrated model was utilized to predict the ductile fracture behavior of QP980 steel sheet loaded along rolling direction under different stress states. To comprehensively consider the impact of anisotropic properties on fracture evolution, an anisotropic MMC (aniso-MMC) ductile fracture model was developed in terms of strain space. Under the assumption of plane stress, the Mohr-Coulomb (MC) criterion was converted from stress space to strain space through an anisotropic constitutive model in order to characterize ductile fracture in QP980 steel sheet. The quadratic yield function of Hill's 48 yield function with the isotropic hardening law was employed to characterize the plastic behavior during loading. The anisotropic fracture loci of QP980 steel sheet were obtained in various loading directions. The scanning electron microscope (SEM) was utilized to characterize the microscopic morphology of the fracture surfaces of QP980 steel sheet, investigating the fracture mechanism of anisotropic ductility under different stress states. The results of both tensile experiments and simulations have confirmed that the plastic anisotropy of materials plays a critical role in determining ductile fracture behavior. The aniso-MMC fracture model was ultimately validated through hole expansion tests and equi-biaxial tensile tests, demonstrating its capability to predict ductile fracture behavior under both proportional and non-proportional loading conditions.

Evaluation of forming limit diagram and bending stiffness of SS316L/polyurethane/SS316L sandwich sheets

Abstract In this study, SS316L/polyurethane/SS316L was produced by warm roll bonding and direct adhesion without using any adhesive. By changing the polymer core thickness in the sandwich sheet, its mechanical properties, such as tensile behavior and flexural bending strength, were investigated. Also, by performing the Erichsen test and getting the experimental forming limit diagram, the forming behavior of the sandwich sheets in various thicknesses was investigated and compared with that of the monolithic steel sheet. The experimental results showed that by increasing the thickness of the sandwich sheets with polymeric core thickness of 2 mm to 2.5 and 3 mm, the bending stiffness was raised by 111% and 288%; also, the displacement in the second region of the bending test diagram, indicating the bending ability without delamination, was increased from 100% to 109%. Forming limit diagrams of the sandwich sheets were higher than those of the steel sheet, which indicates that the forming behavior of them are higher than that of the monolithic steel sheet.

Mechanical characterization and modeling of microstructural deformation of Si anode sheet

Battery anodes generally have a layered structure consisting of an active material layer (including binder, conductive carbon, and active material) and a foil layer of the current collector (copper foil). Such layered structures bring grand challenges to our understanding of the mechanical behaviors of the Si-based anode sheets since the large deformation of the Si particles, and solid-solid interfacial interactions (particle-particle and particle-binder) are key knowledge in high-energy, safe, and durable batteries. Herein, we characterize a typical commercialized Si-based anode with detailed microstructure morphology. Representative mechanical tests, including tensile and compression tests, are conducted to characterize the constitutive behaviors of the anode materials. Further, we propose a 3D computational model with detailed descriptions of the microstructures of the active material is established to enable a fundamental understanding of the deformation behaviors. Results present a comprehensive understanding of the Si-based anode materials for the first time and provide a powerful model for the future design of the anode for the next-generation batteries.

Complex dynamics, released energy, and multistability in a single-layered graphene sheet under periodic loads

Graphene was found in 2004. It’s a carbon allotrope built around a single layer of atoms organized in a two-dimensional (2D) honeycomb lattice nanostructure. In the contribution, the complex behavior of a graphene sheet under periodic loads is investigated using the usual nonlinear analysis tools. From the dynamic states and the material’s symmetry investigations, it is found that the graphene model considered in this work can exhibit the simultaneous existence of up to six different patterns by varying initial conditions for fixed parameters. The Helmholtz theorem is also used to calculate the Hamilton energy of excited graphene. As a result, when the damping coefficient and the nonlocal parameter were close to zero, the system’s energy was null. This supports the fact that when graphene is in its resting state, vibrations are null inside the material. In contrast, when the damping coefficient and the nonlocal parameter were simultaneously increased, the energy of the graphene sheet increased until it reached a peak value, justifying the oscillations observed in the material. The dependency of the material on the initial condition is also used to support the coexistence of the energy found.