Plastic Transition Research Articles

Modeling of load-displacement relationships for corrugated cardboard containers

This article discusses the nonlinear behavior of the corrugated packaging during compression. The model of this behavior is a load-displacement curve with an ascending branch, a peak point and a descending branch. In some cases, the descending branch shows signs of plastic transition and/or loss of stability of the container walls. The purpose of this work is to predict the transition point of a corrugated container into a plastic (or pseudo-plastic) state. This condition is unacceptable because there are residual deformations that reduce the quality of the container. The article proposes and implements an approach based on the joint application of the well-known equation of the dependence of the load on displacement and the differential fracture criterion. The simulation results are consistent with experiments known from the literature. The conducted research makes a certain contribution to the creation of new tools, the use of which expands the possibilities of analyzing the mechanical behavior of corrugated cardboard containers for the purpose of rational use of resources in accordance with the concept of sustainable development.

Physico-mechanical properties and brittle to plastic transition of a thermally cracked marble under uniaxial tension

Thermal stress induces severe changes in rock microstructures, resulting in the variations of physical and mechanical properties. To study thermal effects on rock physical properties and tensile behaviors, monotonic and cyclic tension tests were conducted on marble samples heated at different temperatures. The results show that marble samples are weakened by thermal damage, showing a decrease in tensile strength and P-wave velocity, and an increase in porosity. The changing trends of Young's modulus and failure strain with temperature appear to be scattering and complicated probably depending on the deformation types (i.e., nonlinear elastic deformation and plastic deformation). Nonlinearity is a fundamental feature of tensile stress versus strain curves, which is enhanced when the sample is heated at higher temperature. Even under low tensile stress levels, permanent damages are always observed, highlighting a hysteresis in the stress-strain curves obtained from cyclic tension tests. A transition from the nonlinear elastic deformation to the plastic deformation occurs at approximately 300 - 400°C. A crack density based constitutive model is introduced for the nonlinear elastic deformation (25 - 300°C). A modified Voce exponential function is recommended to capture the tensile stress and strain relationships for the plastic deformation (400 - 700°C).

Circular plastics packaging – Prioritizing resources and capabilities along the supply chain

Implementing the circular economy (CE) in the plastic packaging sector is considered a crucial step towards the adoption of more sustainable practices. However, despite the presence of regulatory CE targets, the plastic packaging sector's transition is not speeding up sufficiently to reach them.Individual companies need to reconfigure their resource base and develop complementary resources and capabilities to improve the systems performance. Based on the resource-based view, this study identifies and prioritizes the most important resources and capabilities for a circular transition along the plastic packaging supply chain. Accordingly, expert opinion was analyzed using a combination of a real-time Delphi method and an analytic hierarchy process. Two aspects were of utmost importance for the experts: collaboration capabilities between upstream and downstream actors, and design capabilities that create simpler and recyclable products. When prioritizing resources and capabilities, potential conflicts between reactive and proactive CE strategies were found. Further research is proposed to (i) develop adequate framework conditions to enable higher waste management targets, (ii) apply dynamic, natural and extended resource-based views to better understand the effects of collaboration networks in CE and their dynamics, and (iii) investigate supply chain power relationships to understand the impacts of supply chain transformations.

Failure and Mechanical Properties of Glassy Diblock Copolymer Thin Films

Block copolymer self-assembly is affected by nanoscale confinement, which has long been known to affect interchain entanglements and dynamics of polymers. While most previous work on confined polymer glasses has focused on the properties of homopolymers, the mechanical response of glassy block copolymer thin films is still relatively unexplored. By uniaxially deforming glassy lamellar diblock copolymer films with different morphologies via molecular dynamic simulations, we demonstrate that the toughness of the films with fingerprint morphologies is higher compared to homopolymers and oriented lamellar films due to the increase in the randomness of domain orientations and entanglements. We show that the thickness impact on the mechanical properties of the block copolymers is not as big as that of the homopolymer systems. In the strain localization analysis of the block copolymer films, there are the plastic rearrangements initially clustered at the boundary between the two phases of the lamellae until close to failure when the plasticity transitions to the center of a domain. In the block copolymer systems, crazes in the thinnest films exhibit distinct behaviors compared to thicker films. Our studies of the film mechanics provide molecular insights into how segmental mobility and entanglements interplay with position and morphology to control the mechanics of thin polymer films.

Multistimuli-Responsive Plasticity Transitions of a Phototransistor Conferred by Using Thermoresponsive Polyfluorene Block Copolymers

Multistimuli-Responsive Plasticity Transitions of a Phototransistor Conferred by Using Thermoresponsive Polyfluorene Block Copolymers

Epithelial-Mesenchymal Plasticity and Endothelial-Mesenchymal Transition in Cutaneous Wound Healing.

Epithelial and endothelial cells possess the inherent plasticity to undergo morphological, cellular, and molecular changes leading to their resemblance of mesenchymal cells. A prevailing notion has been that cutaneous wound reepithelialization involves partial epithelial-to-mesenchymal transition (EMT) of wound-edge epidermal cells to enable their transition from a stationary state to a migratory state. In this review, we reflect on past findings that led to this notion and discuss recent studies that suggest a refined view, focusing predominantly on in vivo results using mammalian excisional wound models. We highlight the concept of epithelial-mesenchymal plasticity (EMP), which emphasizes a reversible conversion of epithelial cells across multiple intermediate states within the epithelial-mesenchymal spectrum, and discuss the critical importance of restricting EMT for effective wound reepithelialization. We also outline the current state of knowledge on EMP in pathological wound healing, and on endothelial-to-mesenchymal transition (EndMT), a process similar to EMT, as a possible mechanism contributing to wound fibrosis and scar formation. Harnessing epithelial/endothelial-mesenchymal plasticity may unravel opportunities for developing new therapeutics to treat human wound healing pathologies.

Synaptic Modulation of Conductivity and Magnetism in a CoPt‐Based Electrochemical Transistor

Among various types of neuromorphic devices toward artificial intelligence, the electrochemical synaptic transistor emerges, in which the channel conductance is modulated by the insertion of ions according to the history of gate voltage across the electrolyte. Despite the striking progress in exploring novel channel materials, few studies report on the ferromagnetic metal‐based synaptic transistors, limiting the development of spin‐based neuromorphic devices. Herein, synaptic modulation of both conductivity and magnetism based on an electrochemical transistor with a metallic channel of ferromagnetic CoPt alloy is presented. Its essential synaptic functionalities in the transistor are demonstrated, including depression and potentiation of synaptic weight and paired‐pulse facilitation (PPF). Then, short‐to‐long‐term plasticity transition induced by different gate parameters, such as amplitude, duration, and frequency, is shown. Furthermore, the device presents multilevel and reversible nonvolatile states in both conductivity and coercivity. The results demonstrate simultaneous modulation of conductivity and magnetism, paving the way for building future spin‐based multifunctional synaptic devices.

An Eulerian thermodynamical formulation of size-dependent plasticity

The objective of this work is to develop a finite-deformation, thermodynamically-consistent theory to model the size-dependent irreversible behavior of metals at the micron-scale. In contrast with other approaches, the proposed Eulerian formulation introduces an evolution equation directly for an elastic distortional deformation measure without the need for defining total or plastic deformation measures. Motivated both by experimental observations and by the literature on generalized continua, the proposed theory assumes tensorial fields separately describing macro-plasticity and micro-plasticity. An additional evolution equation defines a Nye–Kröner-like tensor that depends on the curl of the non-symmetric micro-plasticity distortional rate. By drawing inspiration from higher-order strain gradient plasticity, the micro-plasticity distortional rate is determined by a micro-plasticity balance equation with associated boundary conditions. A quadratic function of the Nye–Kröner-like tensor contributes to the Helmholtz free energy, which leads to an energetic stress entering the micro-plasticity balance that controls the material size-dependent response. The theory is designed to allow the onset of micro-plasticity to occur at a stress level below that triggering macro-plasticity and, regarding size-effects, the response characterized by macro-plasticity alone is the strongest one. In addition, the formulation uses a smooth elastic–plastic transition model for rate-independent response. The theory is specialized to the case of small strains and rotations and applied to the constrained simple shear problem, which allows the derivation of an analytical solution able to demonstrate the predictive capabilities ensuing from the rich interplay between micro- and macro-plasticity.

IGZO nanofiber photoelectric neuromorphic transistors with indium ratio tuned synaptic plasticity

Synaptic plasticity divided into long-term and short-term categories is regarded as the origin of memory and learning, which also inspires the construction of neuromorphic systems. However, it is difficult to mimic the two behaviors monolithically, which is due to the lack of time-tailoring approaches for a certain synaptic device. In this Letter, indium-gallium-zinc-oxide (IGZO) nanofiber-based photoelectric transistors are proposed for realizing tunable photoelectric synaptic plasticity by the indium composition ratio. Notably, short-term plasticity to long-term plasticity transition can be realized by increasing the ratio of indium in the IGZO channel layer. The spatiotemporal dynamic logic and low energy consumption (<100 fJ/spike) are obtained in devices with low indium ratio. Moreover, the symmetric spike-timing-dependent plasticity is achieved by exploiting customized light and electric pulse schemes. Photoelectric long-term plasticity, multi-level characteristics, and high recognition accuracy (93.5%) are emulated in devices with high indium ratio. Our results indicate that such a composition ratio modulated method could enrich the applications of IGZO nanofiber neuromorphic transistors toward the photoelectric neuromorphic systems.

Design of Deep Eutectic Systems: Plastic Crystalline Materials as Constituents.

Deep eutectic solvents (DESs) are a class of green and tunable solvents that can be formed by mixing constituents having very low melting entropies and enthalpies. As types of materials that meet these requirements, plastic crystalline materials (PCs) with highly symmetrical and disordered crystal structures can be envisaged as promising DES constituents. In this work, three PCs, namely, neopentyl alcohol, pivalic acid, and neopentyl glycol, were studied as DES constituents. The solid–plastic transitions and melting properties of the pure PCs were studied using differential scanning calorimetry. The solid–liquid equilibrium phase diagrams of four eutectic systems containing the three PCs, i.e., L-menthol/neopentyl alcohol, L-menthol/pivalic acid, L-menthol/neopentyl glycol, and choline chloride/neopentyl glycol, were measured. Despite showing near-ideal behavior, the four studied eutectic systems exhibited depressions at the eutectic points, relative to the melting temperatures of the pure constituents, that were similar to or even larger than those of strongly nonideal eutectic systems. These findings highlight that a DES can be formed when PCs are used as constituents, even if the eutectic system is ideal.

Stabilizing defective coherent twin boundaries for strong and stable nanocrystalline nanotwinned Cu

Manipulating coherent twin boundaries (CTBs) opens an avenue to design strong nanostructured materials. However, below a critical TB spacing, these inherently defective CTBs decorated with kink-like steps (abbreviated by kinks) and intersected with grain boundaries (GBs) will suffer from the thermal/mechanical instability, leading to the degradation of material properties. Here, utilizing Cr-segregation at kinks and GBs via a minor (1 at.%) Cr-doping, we report the nanocrystalline-nanotwinned (NNT) Cu-Cr alloy manifests continuous strengthening reaching 1.2 GPa at extremely fine TB spacing of ∼ 2 nm, associated with excellent structural-mechanical stability after high-temperature (0.5Tm of Cu) annealing. The underlying mechanism mainly originates from the highly stabilized defective CTBs controlled by Cr-segregation at kinks and TB-GB junctions, which facilitates the plastic deformation mode transition: from detwinning dislocation nucleation to stacking faults (SFs) accumulation for ultrahigh strength. Under elevated temperature, the stabilized TBs inhibit GB motion and therefore result in enhanced thermal stability of NNT Cu-Cr alloys, which is quantitatively explained via a modified Zenner pinning model. Our findings not only deepen the understanding of deformation mechanisms in nanotwinned metals, but also provide a new perspective to design plainified Cu alloys with high performances.

Polyethylene terephthalate (PET) waste plastic as natural aggregate replacement in geopolymer mortar production

This work investigates the recycling potential of polyethylene terephthalate (PET) bottle wastes as natural sand substitute in geopolymer (GP) mixtures to reduce plastic pollution and transition to a circular economy. Fresh and hardened properties of coal fly ash-based GP mortars with replacement of quartz sand by grinded fine PET particles of 0.315–1.25 mm in size (20%, 40%, 60%, 80% and 100%) were evaluated. It was found out that an increase in plastic aggregate content leads to a decrease in compressive strength and flexural strength of geopolymer mortars. In turn, the splitting tensile strength increased slightly when up to 40% of the sand volume was replaced by plastic aggregate. At this replacement level, the fresh geopolymer mixes had workability close to that of conventional mortar. The flake-like PET particles contributed to the reduction of cracking of the specimens and more ductile failure modes. Furthermore, GP mortars containing recycled PET bottle wastes at the full replacement level of natural aggregate showed advantages in lightweight (up to 15%), water absorption (up to 26%) and thermal insulation properties (up to 59%), enabling production of sustainable construction materials with environmental and economic benefits.

Adaptive convexification of microsphere-based incremental damage for stress and strain softening at finite strains

The brief history of relaxation in continuum mechanics ranges from early application of non-convex plasticity and phase transition formulations to small and large strain continuum damage mechanics. However, relaxed continuum damage mechanics formulations are still limited in the following sense that their material response lack to model strain softening and the convexification of the non-convex incremental stress potential is computationally costly. This paper presents a reduced model for relaxed continuum damage mechanics at finite strains which includes strain softening by a fiber-specific damage in the microsphere approach. Computational efficiency is achieved by novel adaptive algorithms for the fast convexification of the one-dimensional fiber material model. The algorithms are benchmarked against state-of-the-art methods, and the choice of quadrature schemes for the microsphere approach is discussed. This contribution is finalized by a mesh independence test.

Subloading-friction model with saturation of tangential contact stress

The incorporation of the saturation of the tangential contact stress with the increase of the normal contact stress is required for the analysis of the friction phenomenon of solids and structures subjected to a high normal contact stress, which cannot be described by the Coulomb friction condition, in which the tangential contact stress increases linearly with the increase of the normal contact stress. In this article, the subloading-friction model, which is capable of describing the smooth elastic—plastic transition, the static—kinetic transition, and the recovery of the static friction during the cease of sliding, is extended to describe this property. Further, some numerical examples are shown, and the validity of the present model will be verified by the simulation of the test data on the linear sliding of metals.

Macrophage induced ERK-TGF-β1 signaling in MCF7 breast cancer cells result in reversible cancer stem cell plasticity and epithelial mesenchymal transition

BackgroundBreast cancer is a heterogenous disease composed of multiple clonal populations and the mechanism by which the tumor microenvironment induces cancer stem cell plasticity is not fully understood. MethodsMCF7 breast cancer cells were treated with macrophage conditioned medium (MɸCM). PD98059 and SB431542 were used for ERK and TGF-βR inhibition respectively. Epithelial-mesenchymal transition (EMT) and cancer stem cell markers (CSC) were studied using qRT-PCR and flowcytometry. SCID mice were used for animal experiments. ResultsMɸCM- induced ERK/TGF-β1 signaling led to enrichment of CSC and EMT in MCF7 cells and mammospheres. These effects were abrogated by both MEK inhibitor PD98059 (TGF-β1 synthesis) and SB431542 (TGF-β1 signaling). The increase in CSC was both hybrid (ALDH1+) and mesenchymal (CD44+ CD24− cells). Increase in hybrid E/M state was at a single cell level as confirmed by the increase in both claudin-1 (E) and vimentin (M). This did not have any growth advantage in SCID mice and monitoring of CSC and EMT markers before and after growth in SCID mice indicated reversal of these markers in tumor cells recovered from mice. Removal of MɸCM and neutralization of TNF-α, IL-6 and IL-1β in MɸCM abrogated ERK phosphorylation, TGF-β and CSC enrichment indicating the requirement of continuous signaling for maintenance. ConclusionsERK signaling plays an important role in MɸCM- induced EMT and CSC plasticity which is completely reversible upon withdrawal of signals. General significanceOur experimental observations support the semi-independent nature of EMT-stemness connection which is very dynamic and reversible depending on the microenvironment.

FFT-based investigation of the shear stress distribution in face-centered cubic polycrystals

The onset of nonlinear effects in metals, such as plasticity and damage, is strongly influenced by the heterogeneous stress distribution at the grain level. This work is devoted to studying the local stress distribution in fcc polycrystals using FFT-based solvers. In particular, we focus on the distribution of shear stresses resolved in the slip systems as the critical driving force for plastic deformations. Specific grain orientations with respect to load direction are investigated in the linear elastic regime and at incipient plastic deformations based on a large ensemble of microstructures. The elastic anisotropy of the single crystal is found to have a crucial influence on the scatter of the stress distribution, whereas the Young’s modulus in the respective crystal direction governs the mean stress in the grain. It is further demonstrated that, for higher anisotropy, the shear stresses deviate from the normal distribution and are better approximated by a log-normal fit. Comparing the full-field simulations to the Maximum Entropy Method (MEM), reveals that the MEM provides an excellent prediction up to the second statistical moment in the linear elastic range. In a study on the spatial distribution of shear stresses, the grain boundary is identified as a region of pronounced stress fluctuations and as the starting point of yielding during the elastic–plastic transition.

Analytical model for viscous and elastic Rayleigh–Taylor instabilities in convergent geometries at static interfaces

Great attention has been attracted to study the viscous and elastic Rayleigh–Taylor instability in convergent geometries, especially for their low mode asymmetries that behave distinctively from the planar counterparts. However, most analyses have focused on the instability at static interfaces that excludes the studies of the Bell–Plesset effects and the elastic–plastic transition since they involve too complex mathematics. Herein, we perform detailed analyses on the dispersion relations by applying the viscous and elastic potential flow method to obtain their approximate growth rates compared with the exact ones to demonstrate: (i) The approximate growth rates based on potential flow method generally coincide with the exact ones. (ii) An alternative expression is proposed to overcome the discrepancy for the low mode asymmetries at fluid/fluid interface. (iii) Extra care must be taken in solids since the maximum discrepancies occur at the n = 1 mode and at the mode proximate to the cutoff. This analytical method of great simplicity is essential to describe the dynamic interface by including the overall motion of the interface based on the static construction, while the exact analysis involves too complex mathematics to be extended by including the Bell–Plesset effects and the elastic–plastic properties. To sum up, the approximate analytical dispersion relations derived in convergent geometries, have the potential for dealing with dynamic interfaces where Bell–Plesset effects are combined with elastic–plastic transition.

Pseudotachylyte-Mylonites Record of Transient Creep From Inter-Seismic Ductile to Co-Seismic Rupture

Transient creep during an earthquake cycle is very important to understand the rheology of fault and deformation mechanisms in the brittle–plastic transition zone. In this paper, we analyzed the microstructures of samples for mylonites, pseudotachylyte, and cataclasite under optical microscope, SEM, and EBSD, which were collected from the Red River fault in southwest of China, where we uncovered a series of ductile to brittle deformed rocks which recorded transient creep related to earthquakes. The results show that mylonites formed at the inter-seismic creep were overprinted by pseudotachylyte and cataclasite which were produced during co-seismic rupture, and cracks in cataclasite were healed during the post-seismic relaxation. Based on the analysis of the microstructures and deformation mechanism of fault rocks, we propose the oscillation deformation model to explain transient creep of the brittle–plastic transition zone during the seismic cycle in the Red River fault.

Elastic–plastic transition of compressional shocks in a perfect 2D Yukawa crystal

Molecular dynamical simulations are performed to systematically investigate the elastic–plastic transition of compressional shocks in a perfect two-dimensional Yukawa crystal. Following the tradition in the theory of elasticity, a stress tensor is used to characterize the state of stress of the simulated systems, and then the variation of the maximum shear stress in the postshock region is precisely obtained. It is found that, as the compression level gradually increases in the 2D Yukawa crystal, the maximum shear stress first increases linearly with the compressional speed until it reaches its extreme value, then decreases drastically to a much lower level. This obtained extreme value of the maximum shear stress is just at the elastic–plastic transition point, corresponding to one-half of the yield stress, which represents the ability to resist the maximum applied shear for the simulated Yukawa crystal. Our calculated Voronoi diagrams and pair correlation functions in the direction perpendicular to the shock compression further confirm this elastic–plastic transition point. It is also found that the critical compressional speed of the elastic–plastic transition point increases with the coupling parameter and decreases with the screening parameter of the 2D Yukawa crystal.

Remote in-line evaluation of acousto-elastic effects during elastic–plastic transition in an aluminum plate under uniaxial tensile and dynamic fatigue loading by laser generated, optically detected surface acoustic waves

Early detection and monitoring of heavy load induced plastic deformation in the structure is crucial for timely intervention before cracking occurs and the material completely fails. Ultrasound can be used for detecting plastic deformation provided the mechanical modulus, which can be probed via changes in velocities. This work presents a measurement scheme that makes use of optically detected, laser-induced surface acoustic waves (SAWs) for remote, real-time, online monitoring of the wave velocity during the elastic–plastic transition occurring in an aluminum plate undergoing a uniaxial tensile test and a dynamic fatigue test. Monochromatic SAWs were photoacoustically generated in a wavelength-controlled way through a transient thermal grating based laser ultrasonics excitation scheme. The SAWs were detected by a home-built photorefractive interferometer. The results reveal both regions of acceleration and slowing down, indicating that the material first stiffens and then starts to form microcracks that make it behave effectively softer for propagating SAWs.