Peel Model Research Articles

Unraveling and in-situ observation on the interfacial mechanical behavior of the NEPE propellant reinforced by NPBA via molecular dynamics simulation

Excellent mechanical properties are the lifeline for the application of solid propellants. Understanding the strengthening mechanism of bonding agent is of great significance for design and application of high-performance bonding agents. In this study, the strengthening mechanism of neutral polymer bonding agent (NPBA) for the NEPE propellant and dynamic mechanical response were explored through MD simulation. Significant difference in bonding role for RDX and HMX surface is first revealed with a more effective improvement in HMX surface. NPBA requires higher peak pulling force to achieve conformational transformation compared with binder throughout the peeling process. The chain orientation and movement undergo significant changes in nitroglycerin environment and an interface peeling model is proposed to reveal the potential mechanism. Finally, the effect of NPBA insertion on interfacial micro-peeling process indicates that no significant detachment of NPBA until the binder was severely deformed, resulting in a higher pulling force required.

Development of a neural network model for peeling–ballooning stability analysis in the KSTAR tokamak pedestals

The neural network model, MISHKA-NN is developed to mitigate the computational burden associated with the linear ideal magnetohydrodynamic (MHD) stability analysis of the pedestal based on the peeling–ballooning (P–B) model. By utilizing both 1D plasma profiles (current density, pressure gradient, and safety factor) and 0D parameters (plasma geometry, total current, and toroidal mode number), the model predicts linear growth rate of edge-localized ideal MHD instability in a given equilibrium state. By enabling the prediction of each instability within a second, the model reduces the time required for plotting a pedestal P–B stability diagram ( j−α diagram) from approximately 100 CPU hours to a few CPU minutes. Notably, even with the utilization of parametric pressure and current profiles and plasma boundary shapes for the training dataset, the model shows a satisfactory level of performance in benchmarking the j−α diagram for the reconstructed equilibrium from a KSTAR tokamak experiment. We anticipate the model to serve as a versatile alternative to 2D linear MHD stability codes, alleviating numerical costs.

Simulation Analysis and Multiobjective Optimization of Pulverization Process of Seed-Used Watermelon Peel Pulverizer Based on EDEM

To enhance the utilization of seed-used watermelon peel and mitigate environmental pollution, a hammer-blade seed-used watermelon peel crusher was designed and manufactured, and its structure and working parameters were optimized. Initially, the seed-used watermelon peel crusher and seed-used watermelon peel model were constructed, and the model’s parameters were calibrated. Subsequently, the discrete element method (EDEM2022) was employed to investigate the effects of spindle speed (MSS), the number of hammers (NCB), and feeding volume (FQ) on the pulverizing process. Multivariate nonlinear regression prediction models were developed for the percentage of pulverized particle size less than 8 mm (Psv), pulverizing efficiency (Ge), and power density (Ppd), followed by the analysis of influencing factors and prediction models using ANOVA. The multiobjective optimization of the prediction model utilizing the improved hybrid metacellular genetic algorithm CellDE resulted in solutions of 90.02%, 89.57%, and 8.35 × 10−3 t/(h-kw) for Psv-opt, Ge-opt, and Ppd-opt, respectively. The corresponding optimal interaction values of MSS, NCB, and FQ were determined to be 1500 r/min, 108, and 150 kg/min. Finally, a prototype test was conducted by combining the optimal factor interaction values, yielding statistically calculated values of 96.63%, 92.37%, and 7.76 × 10−3 t/(h-kw) for Psv-pr, Ge-pr, and Ppd-pr, respectively. The results indicate that the optimized values of Psv-opt, Ge-opt, and Ppd-opt models have an error of less than 8% compared to the statistically calculated values of the prototype test and outperform the values of Psv-ori, Ge-ori, and Ppd-ori obtained under the original parameters.

Physicochemical indicators coupled with statistical tools for comprehensive evaluation of the novel infrared peeling on tomatoes

The peelability of fruit is influenced by numerous factors; thus, it is critical to identify key factors to anticipate peelability. This study aimed to examine variations in peelability and key indices of tomatoes at various infrared (IR) parameters, and their quantitative relationships, using Pearson's correlation and multiple linear regression (MLR) statistical tools. Results showed that the peelability during IR treatment could be quantitatively reflected by content, esterification degree (DE), intrinsic viscosity of pectin, surface temperature, intracellular and extracellular resistance, and relative electrolyte leakage (REL). Among them, contributions of REL, pectin content, DE of pectin, and surface temperature to peelability were more significant. This is because as IR's time and temperature increased, tomatoes' surface temperature increased, leading to the degradation of pectin, and changes in DE of pectin and REL. This contributed to thermal softening of peel and decreased adhesions of cells, leading to skin loosening. Skin loosening along with accumulated pressure improved skin rupture, improving peelability. This peeling model was statistically significant (Adjust R2 = 0.971, Sig. of F-test <0.01), with no outliers, and residuals were independent and normally distributed. Overall, this model can simplify data collection, assist in determining more suitable infrared peeling parameters, and improve the peelability of tomatoes.

Rate-dependent peeling behavior of the viscoelastic film-substrate system

In contrast to the well-understood peeling behavior of an elastic film-substrate system, the peeling behavior of a viscoelastic film bonded to a rigid substrate remains unclear. This paper established a theoretical peeling model, assuming a uniformly distributed cohesive interfacial interaction, to study the steady-state peeling behavior of a viscoelastic film. The rate-dependent behaviors of the steady-state peeling force and the cohesive zone length are mainly analyzed in the present paper. It reveals that there exist 3 typical peeling force-peeling velocity relations relying on the viscous dissipation within the film and the rate-dependent extent of the interfacial adhesion. In addition to the film's viscoelasticity and the peeling velocity, the film thickness, interfacial toughness, and interfacial strength are also identified as factors that influence the steady-state peeling force. For the cohesive zone length of peeling a viscoelastic film, the analytical expression is obtained which demonstrates a dependence on peeling velocity, film viscoelasticity, film thickness, interfacial toughness, and interfacial strength. The present theoretical findings are validated by the finite element simulation and are believed to facilitate the fundamental understandings and practical applications for viscoelastic film-substrate systems.

V-shaped double peeling of films from curved rigid substrates

The peeling phenomenon of films from rigid substrates has been extensively studied, most of which have focused on flat substrates. However, in natural environments, curved substrates with irregular geometries are more prevalent. In this study, the peeling behavior of films from curved rigid substrates is studied. The theoretical model for V-shaped double peeling (VDP) of hyperelastic films from semi-cylindrical substrates has been proposed based on the Griffith’s energy equilibrium theory. An implicit mathematical expression of the relationship between vertical displacement and peeling length is obtained. The peeling length, peeling angle, peeling force and energy change during the peeling process are analyzed and discussed. Subsequently, experimental tests of V-shaped double peeling are carried out affirming the reliability and accuracy of the model. Finally, a simple and efficient new method for evaluating the adhesive energy release rate is proposed.

Multiple kinds of peeling processes and instabilities in heterogeneous film peeling

Although it has been demonstrated that heterogeneous film can enhance adhesion properties without modifying the interface, there is still a dearth of comprehensive studies in the literature regarding the peeling process of such film and the potential instability that may occur during the peeling process. To address these issues, a peeling model based on the cohesion zone model and Euler-Bernoulli beam equation is proposed in this study. Our analysis revealed four previously unknown peeling behaviors: Firstly, there are nine kinds of peeling processes for heterogeneous film. Only one is stable, static peeling process, while the other eight exhibit instability when the peeling front reaches a certain position. Secondly, instability may occur at the interface from the stiff section to the compliant section of the homogeneous film, as well as at stiff section or compliant section. Moreover, two of these peeling processes experience two instabilities within one peeling period – one at the interface from the stiff section to the compliant section and another at stiff section. Thirdly, an optimal length fraction of the stiff section for enhancing adhesive performance exists and its value is largely determined by the strength of the interface material. Specifically, higher interfacial strength results in smaller values of the optimal length fraction. Finally, the maximum peeling force is positively correlated with the bending stiffness ratio, interfacial strength, interfacial toughness, and period length of heterogeneous film. But it is inversely related to the bending stiffness. These findings are crucial for understanding the peeling behavior of heterogeneous film and strongly adhesive interfaces found in nature, and can be applied to optimize adhesive design and performance in practical engineering applications.

Coupled Excitation Strategy for Crack Initiation at the Adhesive Interface of Large-Sized Ultra-Thin Chips

The initial excitation of interface crack of large-size ultra-thin chips is one of the most complicated technical challenges. To address this issue, the reversible fracture characteristics of a silicon-based chip (chip size: 1.025 mm × 0.4 mm × 0.15 mm) adhesive layer interface was examined by scanning electron microscope (SEM) tests, and the characteristics of a cohesive zone model (CZM) unit were obtained through peel testing. The fitting curve of the elastic bilinear model was in high agreement with the experimental data, with a correlation coefficient of 0.98. The maximum energy release rate required for stripping was GC = 10.3567 N/m. Subsequently, a cohesive mechanical model of large-size ultra-thin chip peeling was established, and the mechanical characteristics of crack initial excitation were analyzed. The findings revealed that the larger deflection peeling angle in the peeling process resulted in a smaller peeling force and energy release rate (ERR), which made the initial crack formation difficult. To mitigate this, a coupling control method of structure and force surface was proposed. In this method, through structural coupling, the change in chip deflection was greatly reduced through the surface coupling force, and the peeling angle was greatly improved. It changed the local stiffness of the laminated structure, made the action point of fracture force migrate from the center of the chip to near the edge of the chip, the peeling angle was increased, and the energy release rate was locally improved. Finally, combined with mechanical analysis and numerical simulation of the peeling process, the mechanical characteristics of peeling were analyzed in detail. The results indicated that during the initial crack germination process, the ERR of the peel interface is significantly increased, the maximum stress value borne by the chip is significantly reduced, and the peel safety and reliability are greatly improved.

Capillary Transfer of Self-Assembled Colloidal Crystals.

Colloidal self-assembly has attracted significant interest in numerous applications including optics, electrochemistry, thermofluidics, and biomolecule templating. To meet the requirements of these applications, numerous fabrication methods have been developed. However, these are limited to narrow ranges of feature sizes, are incompatible with many substrates, and/or have low scalability, significantly limiting the use of colloidal self-assembly. In this work, we study the capillary transfer of colloidal crystals and demonstrate that this approach overcomes these limitations. Enabled by capillary transfer, we fabricate 2D colloidal crystals with nano-to-micro feature sizes spanning 2 orders of magnitude and on typically challenging substrates including those that are hydrophobic, rough, curved, or structured with microchannels. We developed and systemically validated a capillary peeling model, elucidating the underlying transfer physics. Due to its high versatility, good quality, and simplicity, this approach can expand the possibilities of colloidal self-assembly and enhance the performance of applications using colloidal crystals.

Influence of particle deposition on heat transfer characteristics for nanofluid free impinging jet: A numerical study

Based on the two-body collision model, a nanoparticle collision, deposition and peeling model is established to describe the nanoparticle deposition process during SiO2-water nanofluid jet impinging on a heated copper column. The model is loaded with the Euler-Lagrange multiphase model in Ansys Fluent 19.1, and its accuracy is verified by comparing with the experimental data. Then the nanoparticle deposition processes during nanofluid jet impinging are studied with different inlet Reynolds numbers (Re), nanofluid volume fractions and impact heights (H/D). Result shows that the amount of nanoparticle deposition increases with the increasing nanofluid volume fraction, and it has a tendency of first increasing and then decreasing with the increasing inlet Reynolds number and the impact height, which reaches a maximum value when Re = 8849 and H/D = 4. Result also shows that it is easier to deposit at the junction between the impact zone and the wall jet zone with a deposition amount approximately 2 times of that at the outlet. A nanoparticle thermal resistance layer and a high-density nanofluid layer are formed in the near-wall region, and velocity slip between phases in the layer could reach 2.824m/s, which significantly enhance the base-fluid’s micro-flow intensity and the particles’ movement, thus strengthening the momentum exchange and energy exchange between phases and wall. The maximum heat transfer coefficient could reach 27857.4 W/(K·m2), and the average heat transfer coefficient has a 67.9% increment with 3% SiO2-water nanofluid volume fraction.

A 3D Griffith peeling model to unify and generalize single and double peeling theories

It has been shown in recent years that many species in Nature employ hierarchy and contact splitting as a strategy to enhance the adhesive properties of their attachments. Maximizing the adhesive force is however not the only goal. Many animals can achieve a tunable adhesive force, which allows them to both strongly attach to a surface and easily detach when necessary. Here, we study the adhesive properties of 3D dendritic attachments, which are structures that are widely occurring in nature and which allow to achieve these goals. These structures exploit branching to provide high variability in the geometry, and thus tunability, and contact splitting, to increase the total peeling line and thus the adhesion force. By applying the same principles presented by A.A. Griffith 100 years ago, we derive an analytical model for the detachment forces as a function of their defining angles in 3D space, finding as limit cases 2D double peeling and 1D single peeling. We also develop a numerical model, including a nonlinear elastic constitutive law, for the validation of analytical calculations, allowing additionally to simulate the entire detachment phase, and discuss how geometrical variations influence the adhesive properties of the structure. Finally, we also realize a proof of concept experiment to further validate theoretical/numerical results. Overall, we show how this generalized attachment structure can achieve large variations in its adhesive and mechanical properties, exploiting variations of its geometrical parameters, and thus tunability. The in-depth study of similar basic structural units and their combination can in future lead to a better understanding of the mechanical properties of complex architectures found in Nature.

Peeling under large bending deformations: Follower versus fixed loads. A unified approach for concentrated or distributed loads

In the non-dissipative regime, the potential energy is the difference between the strain energy of the deforming solid and the work done by the external forces. For configuration-dependent external forces, whose direction is perpendicular to the deformed shape, we obtain a simple formula for the strain energy release rate of peeled strips experiencing large deformations and prove rigorously that the same formula applies for external forces having fixed direction.We then apply Griffith’s criterion for fracture to calculate critical loads for two cases: peeling produced by a uniform follower pressure distributed along the flexible strip and peeling produced by a localized follower shear force applied at the edge of the strip.We found that for these loads, the critical pressure for peeling follows approximately qc∼ΓL−1, where Γ is the solid–solid interface energy and L is the initial peeling length; for the shear force, the corresponding critical value instead follows Q0c∼Γ, independently of the initial length.These formulas are, unexpectedly, independent of the bending stiffness EI of the strips and differ from the ones predicted for small deformations, i.e. qc∝L−2EIΓ and Q0c∝L−1EIΓ.We apply our results to predict the critical hydrodynamic load necessary to exfoliate graphene sheets from graphite, a fluid–structure interaction problem where the load is of the follower type. We find that a follower load peeling model gives significantly improved predictions than fixed load peeling. For the same Γ, L and b, the critical hydrodynamic follower load is always lower than the one with fixed forces: approximately half for the case with uniform pressure, and one third for the case with shear force.

Peeling in electroadhesion soft grippers

Electroadhesion endows robots with super-human abilities: mechanical geckoes that climb vertical walls and soft grippers that grasp the most delicate objects. Based on electrostatics, the adhesion forces are turned on and off by an electrical signal, promising extremely fast operation, from silent fully solid-state devices. Practical applications of electroadhesion have however been limited to date by two main challenges: (1) the adhesion forces can vary over 1000x by simply changing the angle between the electroadhesive tape and the object, (2) release is often slow due to residual adhesion when voltage is removed.This paper describes a solution to both these issues by understanding and leveraging peeling in electroadhesion. We present simple models for peeling of electroadhesive tapes, predicting a change in peeling force from < 1 mN to over 1 N by changing the angle between the tape and the object from 90° to 0°. The models are in excellent agreement with our peeling experiments with 30 mm long, 20 mm wide, 300μm thick electroadhesion tapes made of silicone rubber with carbon electrodes.We demonstrate an electroadhesion soft gripper that uses motorized fingers to control the peeling angle, as a practical application of our peeling models. By moving the fingers to ensure a low peeling angle (0°) when grasping, the same gripper can successfully pick up from a 10 g cherry tomato (2.5 cm wide) to a 600 g Mango (9 cm wide). By then setting a high peeling angle (> 30°), the gripper reliably and rapidly (< 300 ms) releases those objects, despite residual adhesion.Electroadhesion soft grippers have many advantages, including grasping without squeezing, silent operation, low power consumption (< 1 W) and low weight (1 g per soft finger). Understanding and modelling contact mechanics in electroadhesion devices was an essential missing step for practical applications of electroadhesion in robots and grippers. This paper sheds light on how peeling influences electroadhesion and provides practical tools to design and operate electroadhesion systems.

Interfacial Competitive Debonding of a Bilayer Elastic Film on a Rigid Substrate

Abstract Different from the system of a single-layer elastic film on a rigid substrate, the debonding interface is difficult to determine in a bilayer or multilayer film-substrate system. A peeling model of a bilayer elastic film on a rigid substrate is established in the present paper, in order to predict which interface debonding occurs first. The interfacial competitive debonding mechanism is theoretically analyzed with the help of the beam bending theory. A criterion of which interface debonding occurs first is proposed. It is found that the interfacial debonding path is mainly controlled by five dimensionless parameters, i.e., the strength ratio and the critical separation distance ratio of the upper and lower interfaces, the Young's modulus ratio and the thickness ratio of the upper and lower films, and the possible initial cantilever length for ease of loading. The corresponding competitive debonding map is well obtained. From the map, which interface debonding occurs first can be easily predicted. It is interesting to find that the interfacial debonding path can be well tuned by any one of the five parameters. The results of the finite element calculation further confirm the theoretical predictions. The present work can not only provide a theoretical method to determine the interfacial debonding path but also be helpful for the optimal design of multilayer film-substrate systems in practical applications.

Numerical investigation on the influence of particle deposition on nanofluid turbulent flow and heat transfer characteristics

Based on the two-body collision model, a particle collision, deposition and peeling model is established to investigated the influence of nanoparticle deposition process on TiO2 -water nanofluid turbulent flow and heat transfer characteristics in a horizontal circular tube by compiling, linking and executing a program with the Euler-Lagrange multiphase model in Ansys Fluent 19.1. Compared with four different multiphase flow models, this model has a better consistency with the pressure drop of experimental data. And it is applied to study the influence of particle deposition on the flow field and heat transfer. The flow characteristics is analysed from micro-flow perspective to reveal the nanofluid heat transfer enhancement mechanism. Result shows that the nanoparticle deposition layer grows as clusters during flow process, the nanofluid velocity boundary layer becomes thinning, it is easier to deposit at the entrance and the amount can reach more than 7 times of that minimum near the outlet. The velocity difference value between phases is larger as much as 1.23642 m/s, which directly enhances the momentum exchange and energy exchange between phases and wall. That plays a main role of heat transfer enhancement.

Simulation of nanosecond laser cleaning the paint based on the thermal stress

Laser cleaning is a non-contact and straight forward method to remove the paint from the substrate, based on the mechanism of thermal stress. In order to understand the mechanism detailly, it is crucial to investigate the relationship between the laser fluence, interaction time and the temperature rise quantitatively. Herein, we exhibit thermal stress is the primarily mechanism in the paint removal process by nanosecond (ns) laser pulses. Based on this, a theoretical model of nanosecond laser peeling off the paint is developed successfully. It is worth mentioning that the formation of plasma, plasma shielding effect and temperature dependent absorptivity are critical factors, which is considered in this model. The model can predict the theoretical cleaning and damage thresholds based on the mechanism of thermal stress. According to the temperature distribution in this model, it could be found the optimized parameter is at the laser fluence of 1.56 J/cm2. Together, it is expected that this study could provide a theoretical reference regarding to nanosecond laser cleaning the paint layers and pave the way for reducing the substrate damage in various industrial applications.

Micromechanics of liquid-phase exfoliation of a layered 2D material: A hydrodynamic peeling model

We present a micromechanical analysis of flow-induced peeling of a layered 2D material suspended in a liquid, for the first time accounting for realistic hydrodynamic loads. In our model, fluid forces trigger a fracture of the inter-layer interface by lifting a flexible “flap” of nanomaterial from the surface of a suspended microparticle. We show that the so far ignored dependence of the hydrodynamic load on the wedge angle produces a transition in the curve relating the critical fluid shear rate for peeling to the non-dimensional adhesion energy. For intermediate values of the non-dimensional adhesion energy, the critical shear rate saturates, yielding critical shear rate values that are drastically smaller than those predicted by a constant load assumption. Our results highlight the importance of accounting for realistic hydrodynamic loads in fracture mechanics models of liquid-phase exfoliation.

A theoretical-numerical model for the peeling of elastic membranes

The adhesive behavior of biological attachment structures such as spider web anchorages is usually studied using single or multiple peeling models involving “tapes”, i.e. one-dimensional contacts elements. This is an oversimplification for many practical problems, since the actual delamination process requires the modeling of complex two-dimensional adhesive elements. To achieve this, we develop a theoretical-numerical approach to simulate the detachment of an elastic membrane of finite size from a substrate, using a 3D cohesive law. The model is validated using existing analytical results for simple geometries, and then applied in a series of parametric studies. Results show how the pull-off force can be tuned or optimized by varying different geometrical or mechanical parameters in various loading scenarios. The length of the detachment boundary, known as the peeling line, emerges as the key factor to maximize adhesion. The approach presented here can allow a better understanding of the mechanical behavior of biological adhesives with complex geometries or with material anisotropies, highlighting the interaction between the stress distributions at the interface and in the membrane itself.

Structure optimization method based on automatic vectorization

Structure is used more extensively used in program such as scientific computing. But the non-continuity and the non-aligment of vectorization structure array have a dramatic influence on the efficiency of program’s vectorizaton. To reduce the access to these addresses during the SIMD vectorization, a structure peeling model is proposed based on the structure which combines domain access affinity and domain data type. At the same time, to meet t the requirement of memory access continuity and alignment in the vectorization of structured array, an address conversion method is proposed which structure arrays are mapped one by one map to two-dimensional arrays, further reducing the failure rate of cache. By using the test suites of gcc_vec, spec2000 and spec2006, the experimental results on the compiler of automatic vector show that the performance of optimized method can be improved by more than 8%.

Production of D-lactic acid by L. delbrueckii growing on orange peel waste hydrolysates and model monosaccharide solutions: effects of pH and temperature on process kinetics

D-lactic acid is a key monomer of polylactic acid (PLA) and other biopolymers. In this work, the effects of temperature and pH on the D-lactate production with Lactobacillus delbrueckii in model sugar solutions and real orange peel waste hydrolysates (OPWH) have been studied and modeled with a non-structured non-segregated kinetic model. Lactobacillus delbrueckii ssp. delbrueckki CECT 286 yields 0.88 g/g of D-lactate (purity 97%) with a productivity of 2.56 g/L·h in the best tested conditions (40 °C and pH 5.8). The proposed kinetic model is able to describe the performed runs, and its kinetic parameters reflect the influence of temperature and pH on the uptake of monosaccharides, D-lactic acid production, and bacterium growth. Moreover, it can be applied to simulate runs with real OPWH supplemented with MRS broth or corn steep liquor (CSL) as a nitrogen source.