Residual Plastic Research Articles

Mitigation of Stress Corrosion Cracking in Additively Manufactured Stainless Steel by Laser Shock Peening

Abstract Use of laser powder bed fusion (LPBF) stainless steel in corrosive environments is attractive due to material's high corrosion resistance and fine feature resolution, which is advantageous for fluidic applications. For this implementation to be optimized, LPBF stainless steel parts must have reduced susceptibility to stress corrosion cracking (SCC), a failure mode that is of high risk for stainless steels. Laser shock peening (LSP) surface processing has been used to improve SCC resistance in wrought metals and has also been used to improve other material properties of additively manufactured metals. However, LSP has yet to be investigated for the improvement of SCC behavior in LPBF stainless steel. This article demonstrates that not only does LSP improve time to crack initiation of LPBF 316L stainless steel in SCC testing but also improves SCC behavior differently when applied to different surfaces of the build. To explain these results, residual stress, texture, dislocation distribution, hardness, microstructure, and fracture surfaces are investigated, linking different hydrogen embrittlement mechanisms to each of the two build orientations as well as the peened and un-peened conditions. These results are supported by matching the observed crack morphologies to those simulated with dynamic crack modeling, thereby demonstrating the impact of residual stress and plastic versus brittle failure upon the observed outcome.

Adding Rare Earth Oxide Markers to Polyoxymethylene to Improve Plastic Recycling through Tracer-Based Sorting.

Engineering plastics, such as polyoxymethylene (POM), are high-performance thermoplastics designed to withstand high temperature or mechanical stress and are used in electronic equipment, the automotive industry, construction, or specific household utensils. POM is immiscible with other plastics but due to a low volume of production, no methods were developed to separate it from the residual plastic waste stream. Therefore, POM recycling is minimal despite its high market value. This paper provides a proof of concept for tracer-based sorting (TBS) as a potential solution for increasing the separation efficiency of low-volume, high-quality polymers. For this purpose, yttrium oxide (Y2O3) and cerium (IV) oxide (CeO2) have been embedded into the POM matrix. Mechanical tests of samples at varying concentrations (0.1 to 1000 ppm) of both tracers were conducted, followed by an analysis of detectability and dispersibility using a portable X-ray fluorescence spectrometer (p-XRF), subsequently optimizing detection time and tracer concentration. Finally, an experimental scenario was developed to test the fate and potential recovery of the tracer material after the thermal treatment of plastics. A low detectable concentration, short measurement time, low influence on mechanical parameters of the compound, and low loss ratio after simulated recycling prove Y2O3 to be a suitable tracer for the industrial implementation of TBS.

Study on the Characteristics of Residual Film–Soil–Root Stubble Complex in Maize Stubble Fields of the Hexi Corridor and Establishment of a Discrete Element Model

Plastic film mulching is one of the key technologies for improving agricultural productivity in arid and semi-arid regions. However, residual plastic film can severely disrupt the structure of the topsoil in farmland, leading to a decrease in crop yield. The Hexi Corridor, as the largest seed maize production base in the arid regions of Northwest China, is facing an increasingly prominent issue of residual plastic film recovery. This study designed experiments based on the typical maize planting model in the Hexi Corridor. A discrete element simulation model of the residual film–soil–root stubble complex was established using the Bonding-V2 model and API rapid filling technology. The reliability of the simulation model was verified through shear and puncture tests. The study revealed that the soil type in the Hexi Corridor is heavy sandy soil. The differences between the average maximum shear forces in the simulated and actual shear tests for root stubble–soil complexes at depths of 30 mm, 50 mm, and 100 mm were 4.8%, 6.4%, and 6.5%, respectively. Additionally, the differences in the average maximum vertical loading forces in the simulated and actual puncture tests for root stubble–soil complexes at depths of 50 mm and 100 mm were 6.4% and 12.37%, respectively. The small discrepancies between the simulated and actual values, along with the consistency of particle movement trends with real-world conditions, confirmed the reliability and accuracy of the simulation model. This indicates that the established discrete element flexible model can effectively represent actual field conditions, providing discrete element model parameters and theoretical support for optimizing the design of key components in China’s mechanized root stubble handling and residual film recovery machinery.

Impact of microplastic residues from polyurethane films on crop growth: Unraveling insights through transcriptomics and metabolomics analysis

The utilisation of coated controlled-release fertilizers (CRFs) leads to the persistence of residual plastic films in agricultural soils, posing a potential threat to crop health. This study investigates the impacts of four residual films (0.39 %, w/w) derived from CRFs in soil, including petrochemical polyether, bio-based polyether, castor oil polyester, and wheat straw polyester polyurethane on wheat growth. This study found that PecPEUR significantly reduced wheat plant height, stem diameter, leaf area, and aboveground fresh weight by 24.8 %, 20.2 %, and 25.7 %. Through an in-depth exploration of transcriptomics and metabolomics, it has been discovered that all residual films disrupted glycolysis-related metabolic pathways in wheat roots, affecting seedling growth. Among them, PecPEUR significantly reduced the fresh weight of aboveground parts by 20.5 %. In contrast, polyester polyurethane residue had no discernible impact on aboveground wheat growth. This was attributed to the enrichment of wheat root genes in jasmonic acid and γ-aminobutyric acid metabolic pathways, thus mitigating oxidative stress, enhancing stress resistance, and ensuring normal plant growth. This study, for the first time, provides comprehensive insights into the effects of polyurethane film residue on wheat seedling growth, underscoring its potential as a promising alternative to conventional plastics in soil.

Dual skin effect and deep heterostructure of titanium alloy subjected to high-frequency electropulsing-assisted laser shock peening

Laser shock peening, an advanced technology for severe surface plasticity peening, encounters challenges such as shallow hardened layers and surface spalling when dealing with difficult-to-machine materials. In this study, we introduced a high-frequency electropulsing-assisted laser shock peening (HFEP-LSP) technique that coupled laser shock peening with high-frequency electric pulses to achieve a significant and deeper plastic deformation layer. In the HFEP-LSP technique, we first considered the dual “skin effect”, which coupled the skin effect of high-frequency electric pulses with the “skin effect” of the mechanical effect induced by the laser shock wave. An integrated experimental platform comprising an electric pulse generator, laser shock peening equipment, and a control system was built. A >1.6 mm deep compressive residual stress layer was obtained, and the depth of the plastic deformation layer increased by 83.3 %. Furthermore, we elucidated the dual “skin effect”-induced complex heterostructure and βm phase transition. A comprehensive analysis revealed the factors contributing to the deeper strengthening layer induced by HFEP-LSP, including the compressive residual stress and plastic deformation layers. In addition, the effects of laser shock peening and HFEP-LSP on the mechanical properties were investigated. Compared to the annealed samples, the ultimate tensile strength and elongation of the HFEP-LSP-treated samples were increased by 12.3 % and 57.1 %, respectively, with a fatigue life improvement of 176.4 %. The mechanism of synergistic improvement in strength and ductility was demonstrated.

Fatigue Life Prediction for 2060 Aluminium–Lithium Alloy with Impact Damage

The paper investigates the issue of post-impact fatigue damage of the 2060 aluminium–lithium alloy, a representative material of third-generation aluminium–lithium alloys extensively employed in the fuselage of C919 aircraft due to its notable attributes of high specific stiffness and strength. Initial impact damage is identified utilizing a residual stress–strain field obtained from a quasi-static simulation. Then, the continuum damage mechanics approach is applied to predict the fatigue life of the impacted 2060 aluminium–lithium alloy plates accounting for the combined effects of residual stress, plastic damage, and fatigue loading. A comparative analysis between calculated and experimental results is conducted to validate the efficacy of the proposed methodology.

Residual plastic film decreases crop yield and water use efficiency through direct negative effects on soil physicochemical properties and root growth

Film mulching has been extensively used to improve agricultural production in arid regions of China. However, without sufficient mulch film recovery, large amounts of residual film accumulated in the farmland, which would affect crop yield and water use efficiency (WUE). In order to comprehensively analyze the effects of residual film on crop yield and WUE, and clarify its influencing mechanism, present study adopted a meta-analysis to systematically evaluate the impacts of residual film on soil physicochemical properties, crop root growth, yield, and WUE. The results showed that residual film significantly increased soil bulk density and the soil moisture content in 0–20 cm soil layer, but decreased soil porosity, soil organic matter, soil total nitrogen content, and soil moisture content in >20 cm soil layer, especially when residual film amount was >400 kg ha−1. Residual film significantly reduced crop root dry weight, root length, root diameter, root volume and root surface area. Generally, crop yield and WUE decreased with the increase of residual film amount; and crop yield was reduced by about 14.00 % when the residual film amount increased by 1000 kg ha−1. In average, crop yield and WUE under film residual condition were significantly decreased by 13.46 % and 9.21 %, respectively. The negative effects of residual film on root growth, yield and WUE were greater for cash crops (cotton, tomato and potato) than for cereal crops (wheat, maize). The structural equation model indicated that residual film generated indirect negative effects on crop yield and WUE by directly affecting soil physicochemical properties and crop root growth, with the standard path coefficients of −0.302 and − 0.217, respectively. The results would provide a theoretical basis for reducing residual film pollution on farmland and promoting the green and sustainable development of agriculture.

A comprehensive analysis of cermet design and thermal cyclic stability via elasto-viscoplastic crystal plasticity modeling

Ceramic-metal composites, or cermets, exhibit beneficial properties resulting in their use in many industrial applications. One challenge with cermets is mismatches in the coefficient of thermal expansion (CTE) values between the ceramic and metal phases that lead to residual stresses after processing, plasticity in the metal phase, internal stresses, and instability after thermal cycling. In order to make predictions of these properties to inform the design of cermets, we employ an incremental elasto-viscoplastic, self-consistent formulation to calculate the thermal, elastic, and plastic strains in two-phase polycrystalline cermet materials. This framework is extended to include temperature dependent properties, which are called implicitly within the temperature-dependent, incremental elasto-viscoplastic, self-consistent (TE-VPSC) model. Temperature-induced cooling and thermal cycling simulations are conducted using the TE-VPSC framework to study the residual stresses and plastic strains in the metal phases. Two materials are discussed in detail exhibiting stark differences based on the CTE between their ceramic and metal phases, WC/57-vol% Cu (exhibiting a pronounced CTE mismatch) and Y2O3/27-vol% Nb (exhibiting a negligible CTE mismatch). The model demonstrates high residual stresses in the Cu phase during processing and reverse plasticity leading to recovery of plastic strain during thermal cycling of the WC/Cu cermet. Moreover, the model demonstrates relatively low residual stresses and plasticity in Y2O3/Nb and a thermal stability point of 1251 °C, below which no plasticity develops in the cermet. We employ the TE-VPSC model as a design tool for cermets to systematically investigate the effects of process-induced microstructure variations (volume fraction, grain aspect ratio, and crystallographic texture are investigated) and compositional differences (19 compositions are explored) on the residual stress, degree of plasticity in the metal phase, and thermal stability point. The computational efficiency of the TE-VPSC framework makes it a desktop design tool that can be used to quantify the impact of changing composition, processing, and thermo-mechanical loading on the performance of the cermet, which can help reduce the number of time intensive and costly high temperature experiments.

Innovative Methods to Improve the Seismic Performance of Precast Segmental and Hybrid Bridge Columns under Cyclic Loading

This paper investigates the seismic performance of prefabricated segmental bridge columns (PSBCs) with hybrid post-tensioned tendons and energy dissipation (ED) bars under cyclic loading. PSBCs with unbonded and hybrid bonded prestressed tendons and columns incorporating ED bars are designed to improve the lateral strength, energy dissipation, and limit the residual drift. The PSBCs under cyclic loading were investigated using the three-dimensional finite element (FE) modeling platform ABAQUS. The FE model was calibrated against experimental results, with an overall error of less than 10%. The seismic performance of the proposed PSBCs was evaluated based on critical parameters, including lateral strength, residual plastic displacement, and the energy dissipation capacity. The results show that bonding the tendons in the plastic hinge region as opposed to the overall bonding along the column leads to a better cyclic performance. The lateral strength, and recentering abilities are further improved by bonding tendons up to 2/3 of the length in the plastic hinge region, along with 100–300 mm in the footing. It was also found that selecting a longitudinal length of ED bars crossing multiple precast segmental joints and having a circumferential spread of 70–90% of core concrete results in a higher bearing capacity and energy dissipation compared to ED bars crossing the single joint.

Elasto-plastic residual stress analysis of selective laser sintered porous materials based on 3D-multilayer thermo-structural phase-field simulations

Residual stress and plastic strain in additive manufactured materials can exhibit significant microscopic variation at the powder scale, profoundly influencing the overall properties of printed components. This variation depends on processing parameters and stems from multiple factors, including differences in powder bed morphology, non-uniform thermo-structural profiles, and inter-layer fusion. In this research, we propose a powder-resolved multilayer multiphysics simulation scheme tailored for porous materials through the process of selective laser sintering. This approach seamlessly integrates finite element method (FEM) based non-isothermal phase-field simulation with thermo-elasto-plastic simulation, incorporating temperature- and phase-dependent material properties. The outcome of this investigation includes a detailed depiction of the mesoscopic evolution of stress and plastic strain within a transient thermo-structure, evaluated across a spectrum of beam power and scan speed parameters. Simulation results further reveal the underlying mechanisms. For instance, stress concentration primarily occurs at the necking region of partially melted particles and the junctions between different layers, resulting in the accumulation of plastic strain and residual stress, ultimately leading to structural distortion in the materials. Based on the simulation data, phenomenological relation regarding porosity/densification control by the beam energy input was examined along with the comparison to experimental results. Regression models were also proposed to describe the dependency of the residual stress and the plastic strain on the beam energy input.

Motor imagery-based brain–computer interface rehabilitation programs enhance upper extremity performance and cortical activation in stroke patients

BackgroundThe most challenging aspect of rehabilitation is the repurposing of residual functional plasticity in stroke patients. To achieve this, numerous plasticity-based clinical rehabilitation programs have been developed. This study aimed to investigate the effects of motor imagery (MI)-based brain–computer interface (BCI) rehabilitation programs on upper extremity hand function in patients with chronic hemiplegia.DesignA 2010 Consolidated Standards for Test Reports (CONSORT)-compliant randomized controlled trial.MethodsForty-six eligible stroke patients with upper limb motor dysfunction participated in the study, six of whom dropped out. The patients were randomly divided into a BCI group and a control group. The BCI group received BCI therapy and conventional rehabilitation therapy, while the control group received conventional rehabilitation only. The Fugl–Meyer Assessment of the Upper Extremity (FMA-UE) score was used as the primary outcome to evaluate upper extremity motor function. Additionally, functional magnetic resonance imaging (fMRI) scans were performed on all patients before and after treatment, in both the resting and task states. We measured the amplitude of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), z conversion of ALFF (zALFF), and z conversion of ReHo (ReHo) in the resting state. The task state was divided into four tasks: left-hand grasping, right-hand grasping, imagining left-hand grasping, and imagining right-hand grasping. Finally, meaningful differences were assessed using correlation analysis of the clinical assessments and functional measures.ResultsA total of 40 patients completed the study, 20 in the BCI group and 20 in the control group. Task-related blood-oxygen-level-dependent (BOLD) analysis showed that when performing the motor grasping task with the affected hand, the BCI group exhibited significant activation in the ipsilateral middle cingulate gyrus, precuneus, inferior parietal gyrus, postcentral gyrus, middle frontal gyrus, superior temporal gyrus, and contralateral middle cingulate gyrus. When imagining a grasping task with the affected hand, the BCI group exhibited greater activation in the ipsilateral superior frontal gyrus (medial) and middle frontal gyrus after treatment. However, the activation of the contralateral superior frontal gyrus decreased in the BCI group relative to the control group. Resting-state fMRI revealed increased zALFF in multiple cerebral regions, including the contralateral precentral gyrus and calcarine and the ipsilateral middle occipital gyrus and cuneus, and decreased zALFF in the ipsilateral superior temporal gyrus in the BCI group relative to the control group. Increased zReHo in the ipsilateral cuneus and contralateral calcarine and decreased zReHo in the contralateral middle temporal gyrus, temporal pole, and superior temporal gyrus were observed post-intervention. According to the subsequent correlation analysis, the increase in the FMA-UE score showed a positive correlation with the mean zALFF of the contralateral precentral gyrus (r = 0.425, P < 0.05), the mean zReHo of the right cuneus (r = 0.399, P < 0.05).ConclusionIn conclusion, BCI therapy is effective and safe for arm rehabilitation after severe poststroke hemiparesis. The correlation of the zALFF of the contralateral precentral gyrus and the zReHo of the ipsilateral cuneus with motor improvements suggested that these values can be used as prognostic measures for BCI-based stroke rehabilitation. We found that motor function was related to visual and spatial processing, suggesting potential avenues for refining treatment strategies for stroke patients.Trial registration: The trial is registered in the Chinese Clinical Trial Registry (number ChiCTR2000034848, registered July 21, 2020).

Elastoplastic properties of ion exchangers based on cross-linked polyelectrolytes

In this paper, we dilatometrically studied the elastoplastic properties of spherical grains of industrial weakly acidic and strongly acidic ion-exchanger in experiments with constant uniaxial compression and a subsequent unload at room temperature, depending on the ionic form and concentration of the electrolyte solution. It was found that the ionic form of polyacrylate and polymethacrylate cross-linked with triethylene glycol dimethacrylate and divinylbenzene, respectively, and the concentration of the external solution affects their elastoplastic properties. In dilute solutions of sodium chloride and calcium chloride, the gels exhibited elastic properties with close relative amplitudes of deformation. The amplitude of deformation of the grain of polymethacrylate crosslinked with divinylbenzene, in the Ni form, in a dilute nickel chloride solution was significantly lower than that of the Ca form, with significant plastic deformation. With an increasing concentration of the external solution of calcium and nickel chlorides under mechanical load on the grain of polymethacrylate cross-linked with divinylbenzene, the total deformation of the granule and the magnitude of elastic deformation decreased, while the residual (plastic) deformations increased. In concentrated solutions of CaCl2 and NiCl2, such an ion-exchanger became an inelastic rigid material. Even under increased mechanical load, the magnitude of its elastic compressive deformation was very small. The K-form of a swollen in water strongly acidic polystyrene cation-exchanger with grafted sulpho groups cross-linked with divinylbenzene is also characterized by elastic deformations, i.e. the polymer is in a highly elastic state. However, the polystyrene matrix is more rigid compared to polyacrylic and polymethacrylic cation-exchangers in the alkali metal ion form, so the amplitude of deformation is significantly smaller. For such a cation-exchanger in Ca- and Ni- forms, elastic deformations prevail even in concentrated solutions.

Limpet-inspired design and 3D/4D printing of sustainable sandwich panels: Pioneering supreme resiliency, recoverability and repairability

Sandwich panels, characterized by their solid exterior and thick, soft core, find extensive applications ranging from maritime to aerospace sectors due to their exceptional resilience and energy absorption/dissipation capabilities. The natural limpet, known for its resilience to mechanical loading, serves as inspiration in the present research to introduce innovative repairable core shells. Limpet-inspired shells with elasto-plastic and brittle behaviors are designed and 3D/4D printed using polylactic acid (PLA) filaments and resins via fused filament fabrication (FFF) and liquid crystal display (LCD) techniques. While PLA filament exhibits an elasto-plastic response with a shape-recovery feature, the resin results in brittle structures for LCD-printed design. The study demonstrates that the FFF-printed PLA shell can fully recover residual plastic deformations, while the LCD-printed PLA shell exhibits a mechanical fracture behavior very similar to the natural limpet with brittle properties. A nonlinear finite element model (FEM) is also developed to replicate the large deformations of the samples under quasi-static compression with a high level of accuracy. Experimental and numerical results reveal that the samples with material, mechanical behavior, and geometry close to the natural limpet result in the maximum energy dissipation per unit mass. Two bio-inspired cores are then tessellated to introduce a new class of sustainable sandwich panels with supreme recoverability, resiliency, and repairability. A three-point bending test is numerically carried out on sandwich panels using FEM, and their energy absorption and dissipation capacities are studied. Results demonstrate that the proposed sandwich panels can achieve almost 7.33 and 1.17 times higher energy dissipation per unit mass than those developed based on a recycled thermoplastic bottle cap core. This pioneering research sets a new benchmark for structural design in terms of resiliency, recoverability, repairability, and sustainability.

Effects of Different Film Types on Cotton Growth and Yield under Drip Irrigation

To address residual plastic film in fields in which mulched drip irrigation technology is applied, a sprayable degradable film (consisting of 1–5% clay, 5–20% humic acid, 0.5–5% crosslinker, and 0.5–5% auxiliary and water) can be used as a superior alternative to the plastic film applied in drip-irrigated fields. A field experiment was conducted in Xinjiang, Northwest China, to test the impacts of five different mulching treatments (SF1, sprayable degradable film applied at 1900 kg ha−1; SF2, sprayable degradable film applied at 1900 kg ha−1; SF3, sprayable degradable film applied at 2500 kg ha−1; PF, plastic film; and NF, no film mulching) on cotton growth and development, yield, and water use efficiency. The results showed that, compared to the NF treatment, sprayable degradable film mulching (SF1, SF2, and SF3) positively impacted the soil hydrothermal environment, promoted root growth, significantly increased plant height and leaf area, and enhanced physiological characteristics, which, in turn, increased yield and water use efficiency by 11.79–15.00% and 21.88–30.21%, respectively. The maximum yield and water use efficiency were observed in the PF treatment, amounting to 5345 kg ha−1 and 1.28 kg m−3, respectively, and they had no significant differences from those in the SF3 treatment. In general, applying moderate amounts of sprayable degradable film at a rate of 2500 kg ha−1 represents an effective agronomic strategy for managing residual film contamination while maintaining stable cotton yields.

Effect of Accumulative Roll Bonding Cycles and Postprocessing Heat Treatment Temperature on Shape Memory Properties of Cu–Al–Ag Alloys

Herein, Cu/Al/Ag‐layered composites with two silver powder concentrations (2 wt% and 3 wt%) are fabricated with the aid of accumulative roll bonding (ARB). The ARB‐ed samples are heat treated at different temperatures (750, 850, 950, and 1050 °C), times (30, 45, and 60 min), and cycles (1–9 cycles) to produce Cu–Al–Ag shape memory alloys. The samples are characterized by X‐ray diffraction, scanning electron microscope, and electron backscattering diffraction. Phase transformation temperatures are measured by differential scanning calorimetry. Strain recovery and shape memory behavior are evaluated by bending and tensile tests, respectively. The results indicate that alloys containing 2 wt% Ag, rolled till 9 cycles, heat treated at 950 °C for 60 min, and samples with 3 wt% Ag, fabricated by 9 cycles, annealed at 850 °C for 60 min show maximum β martensite phase amount. The strain recovery ratios of the first and second samples are 71.7% and 71.2%, respectively. Additionally, the tensile test shows that the residual plastic strain and the recovered strain for the first sample with 2 wt% Ag are equal to 0.7% and 3.0%, respectively. These results for the second sample with 3 wt% Ag are 1.2% and 3.4%, respectively.

Alkali, thermal, or thermo-alkali pre-treatment to improve the anaerobic digestion of poly(lactic acid)?

Replacing petroleum-based plastics with biodegradable polymers is a major challenge for modern society especially for food packaging applications. To date, poly(lactic acid) represents 25 % of the total biodegradable plastics and it is estimated that, in the future, it could become the main contributor to the biodegradable plastics industry. Anaerobic digestion is an interesting way for the poly(lactic acid) end of life, even if its biodegradability is limited in mesophilic conditions. The aims of this study were to identify the best pre-treatment for maximizing the methane yield, minimizing the anaerobic digestion duration and limiting residual plastic fragments in the digestate. A systematic comparison was carried out between thermal, chemical, and thermo-chemical pre-treatment. Pre-treatment with 4 M KOH for 48 h at 35°C was effective in improving the mesophilic anaerobic digestion of the poly(lactic acid). Such pre-treatment allows obtaining 90 % of the theoretical methane potential, in 24 - 30 days. Importantly, such pre-treatment completely solubilized the poly(lactic acid), leaving no solid residues in the digestate. In addition, using KOH permits to avoid the sodication of the soil due to the digestate application as fertilizer.

Mean-field analysis of the glassy dynamics of an elastoplastic model of super-cooled liquids

We present a mean-field theory of a coarse-grained model of a super-cooled liquid in which relaxation occurs via local plastic rearrangements. Local relaxation can be induced by thermal fluctuations or by the long-range elastic consequences of other rearrangements. We extract the temperature dependence of both the relaxation time and the length scale of dynamical correlations. We find two dynamical regimes. First, a regime in which the characteristic time and length scales diverge as a power law at a critical temperature T c . This regime is found by an approximation that neglects activated relaxation channels, which can be interpreted as akin to the one found by the mode-coupling transition of glasses. In reality, only a crossover takes place at T c . The residual plastic activity leads to a second regime characterised by an Arrhenius law below T c . In this case, we show that the length scale governing dynamical correlations diverges as a power law as , and is logarithmically related to the relaxation time.

Machine learning-based characterization of friction stir welding in aluminum alloys

This research presents a machine learning (ML) approach that integrates Bayesian theorem to predict residual stress, plastic deformation, and peak temperature in friction stir welding (FSW) of different types of aluminum alloys. The training data was acquired from extensive numerical simulations of FSW conducted across various input parameter configurations. The regression analysis exhibits strong predictive performance for residual stress, peak temperature, and plastic deformation, achieving determination coefficients of 0.969, 0.955, and 0.919, respectively. The high prediction performance of the developed model is primarily attributed to Bayesian optimization, distinguishing it from other conventional ML methods. The results further demonstrate the efficacy of the proposed model in assessing the relevance of input features to prediction efficiency and output targets. For instance, concerning processing parameters, the predictive performance is closely correlated with the significance of preheating, traverse speed, and rotational speed in FSW, compared to welding force and plate thickness. On the other hand, considering material properties, it was observed that the hardness value of aluminum alloys emerged as a crucial predictor in the model so that alloys with moderate hardness values showed greater welding consistency and significantly enhanced prediction accuracy.

Experimental study of combustion and performance efficiency of diesel engine fuelled with various blends of waste plastic oil

To find the alternatives to the non renewable energy sources are futures demand and disposal of plastic waste is today’s need. Recovery of fuel oil from waste plastic gives the best option on both problems facing all over the world. The present experimental study deals with to analyze the performance and combustion parameters of oil synthesized by catalytic pyrolysis of waste polyethene; as it can be an alternative to diesel which is non renewable energy resource. Commercial diesel blend with condensed plastic oil as well as with residual plastic oil in the ratio of 10% (diesel 90% and plastic oil 10%), 20% (diesel 80% and plastic oil 20), 30% (diesel 70% and plastic oil 30%) and 50% (diesel 50% and plastic oil 50%) in volume. Combustion analysis and performance studies was carried out at 25%, 50%, 75% and 100% load condition in internal combustion engine set up under test is Kirloskar TV1 to understand the feasibility of utilizing plastic oil as substitute fuel to commercial diesel. This study proved that 50% blending gives satisfactory results for performance and combustion parameters than 100% use of commercial diesel.

Mixed experimental-numerical method for quantitative measurement of mode II fibre/matrix interface debonding and comparison of fibre sizings in single short fibre composites

In short fibre composites, debonding cracks usually initiate from fibre tips and their growth is governed by the properties of the fibre/matrix interface. These properties are ideally acquired from a model test similar to the real composite, while excluding the effects of fibre fractures and the induced debonding interactions. Therefore, in this study, debonding growth was examined in detail, using novel single short fibre specimens, which were fabricated using a new methodology. These experiments were further complemented with a continuous fibre case study, where the established single fibre fragmentation specimens were evaluated. The progression of debonding and pull-out damages versus remote stress was studied for two fibre sizings utilizing real-time in-situ polarized light microscopy. A finite element model was built to obtain the fibre/matrix interfacial fracture toughness considering thermal residual stresses, friction and matrix plasticity, and a very good correlation was obtained between the model and the experiments.