Plastic Analysis Research Articles

From crack line field analysis method to symmetric line analysis method: Elastic-plastic analysis of symmetry problems

The mathematical difficulty encountered in the elastic–plastic analysis of solids lies in solving the partial differential equations analytically in the theory of plasticity. Such a mathematical dilemma has existed for decades and analytical solutions are still waiting to be obtained. This paper extends the crack line field analysis method and puts forward a symmetric line analysis method, which uses the parity of the Taylor series expansion of the plastic stress field near the symmetric line to transform the problem of solving partial differential equations into ordinary ones, and so obtain the general Taylor series solution of the plastic stress field near the symmetric line. The symmetric line analysis method can give elastic–plastic solutions to plane and anti-plane symmetry problems that have not been analytically solved before, which achieves an essential leap forward in the analytical analysis of elastic–plastic solids in the theory of plasticity. In this paper, three types of symmetry problems are defined, and examples are given for the elastic–plastic analysis and solution of each type of symmetry problems of elastic-perfectly plastic solids with the symmetric line analysis method.

Legacy and Emerging Plasticizers and Stabilizers in PVC Floorings and Implications for Recycling.

Hazardous chemicals in building and construction plastics can lead to health risks due to indoor exposure and may contaminate recycled materials. We systematically sampled new polyvinyl chloride floorings on the Swiss market (n = 151). We performed elemental analysis by X-ray fluorescence, targeted and suspect gas chromatography-mass spectrometry analysis of ortho-phthalates and alternative plasticizers, and bioassay tests for cytotoxicity and oxidative stress, and endocrine, mutagenic, and genotoxic activities (for selected samples). Surprisingly, 16% of the samples contained regulated chemicals above 0.1 wt %, mainly lead and bis(2-ethylhexyl) phthalate (DEHP). Their presence is likely related to the use of recycled PVC in new flooring, highlighting that uncontrolled recycling can delay the phase-out of hazardous chemicals. Besides DEHP, 29% of the samples contained other ortho-phthalates (mainly diisononyl and diisodecyl phthalates, DiNP and DiDP) above 0.1 wt %, and 17% of the samples indicated a potential to cause biological effects. Considering some overlap between these groups, they together make up an additional 35% of the samples of potential concern. Moreover, both suspect screening and bioassay results indicate the presence of additional potentially hazardous substances. Overall, our study highlights the urgent need to accelerate the phase-out of hazardous substances, increase the transparency of chemical compositions in plastics to protect human and ecosystem health, and enable the transition to a safe and sustainable circular economy.

Calculation method for flexural capacity of composite girders with corrugated steel webs

Experimental and numerical simulation studies were conducted to investigate the differences in bending performance between steel I-girder composite girders with corrugated steel webs (CSWs) and traditional steel I-girder composite girders with flat steel webs (FSWs). The flexural capacity calculation method specified in Eurocode 4 is applied to steel I-girder composite girders with FSWs. However, using the method of steel I-girder composite girders with CSWs revealed an error of approximately 25% between the calculated results and the experimental results. This paper employed the continuous strength method to conduct an elastic–plastic analysis of steel I-girder composite girders with CSWs, considering both the bending contribution of CSWs and the strengthening effect of the steel girder. A calculation method for the flexural capacity suitable for composite girders with CSWs was also introduced. Remarkably, the research outcomes indicated that under ultimate loads, the webs of the steel I-girder composite girder with FSWs underwent buckling deformation. In contrast, the webs of the steel I-girder composite girder with CSWs remained intact, showcasing excellent buckling stability. Compared to the calculation results of the formula specified in Eurocode 4, the accuracy of the proposed calculation method in this paper is improved by 17%. This method can effectively predict the flexural capacity of composite girders with CSWs and is suitable for practical engineering applications.

Asymptotic analysis of single-slip crystal plasticity in the limit of vanishing thickness and rigid elasticity

Abstract We perform via Γ-convergence a 2d-1d dimension reduction analysis of a single-slip elastoplastic body in large deformations. Rigid plastic and elastoplastic regimes are considered. In particular, we show that limit deformations can essentially freely bend even if subjected to the most restrictive constraints corresponding to the elastically rigid single-slip regime. The primary challenge arises in the upper bound where the differential constraints render any bending without incurring an additional energy cost particularly difficult. We overcome this obstacle with suitable non-smooth constructions and prove that a Lavrentiev phenomenon occurs if we artificially restrict our model to smooth deformations. This issue is absent if the differential constraints are appropriately softened.

Rapid single-particle chemical imaging of nanoplastics by SRS microscopy.

Plastics are now omnipresent in our daily lives. The existence of microplastics (1 µm to 5 mm in length) and possibly even nanoplastics (<1 μm) has recently raised health concerns. In particular, nanoplastics are believed to be more toxic since their smaller size renders them much more amenable, compared to microplastics, to enter the human body. However, detecting nanoplastics imposes tremendous analytical challenges on both the nano-level sensitivity and the plastic-identifying specificity, leading to a knowledge gap in this mysterious nanoworld surrounding us. To address these challenges, we developed a hyperspectral stimulated Raman scattering (SRS) imaging platform with an automated plastic identification algorithm that allows micro-nano plastic analysis at the single-particle level with high chemical specificity and throughput. We first validated the sensitivity enhancement of the narrow band of SRS to enable high-speed single nanoplastic detection below 100 nm. We then devised a data-driven spectral matching algorithm to address spectral identification challenges imposed by sensitive narrow-band hyperspectral imaging and achieve robust determination of common plastic polymers. With the established technique, we studied the micro-nano plastics from bottled water as a model system. We successfully detected and identified nanoplastics from major plastic types. Micro-nano plastics concentrations were estimated to be about 2.4 ± 1.3 × 105 particles per liter of bottled water, about 90% of which are nanoplastics. This is orders of magnitude more than the microplastic abundance reported previously in bottled water. High-throughput single-particle counting revealed extraordinary particle heterogeneity and nonorthogonality between plastic composition and morphologies; the resulting multidimensional profiling sheds light on the science of nanoplastics.

PERFORMANCE OF CONCRETE SLAB REINFORCED BY CFRP BARS AND STRENGTHENED BY DIFFERENT LAYOUT OF CFRP LAMINATES

In recent years, Fiber Reinforced Polymer (FRP) rebar has been adopted to reinforce structural concrete elements such as slabs. FRP strips are also increasingly used to reinforce or strengthen concrete members that require higher carrying capacity or to restore damaged structural elements. Therefore, the reinforcement of concrete structures with this material is increasing but the effect of variables on CFRP-reinforced concrete slabs and externally bonded with CFRP laminates has not been evaluated in detail. This study presents a numerical analysis of the structural performance of concrete slabs reinforced by CFRP bars and strengthened by CFRP laminates using a finite element approach with ANSYS software. Six models with the same geometry (1550x1550x100 mm) were analyzed. Four models were reinforced with CFRP bars and externally strengthened with CFRP laminates, one model was reinforced with CFRP bars without external strength, and one reference model with traditional reinforcing bars (control specimen). Different parameters were adopted, such as amounts of FRP bars and CFRP laminates layout in which some models contained both CFRP bars and CFRP laminates. A uniformly distributed load that was calculated by plastic analysis was applied at the top surface area of each model. The plastic load considers the contribution of the laminated CFRP strips that increased the strength of the slab. Analysis results in the maximum strength carrying capacity in equivalent CFRP bars exhibit higher strength percentages of 5.07% of load capacity but differed in mode of failure than conventional reinforcements control slab.

Characterization of sago starch-based degradable plastic with agricultural waste cellulose fiber as filler

&lt;abstract&gt; &lt;p&gt;Sago starch and cellulose fiber can be used as a raw material for making degradable plastics to replace commercial plastics. This research used corn cob fiber and sugarcane bagasse fiber as filler to improve the properties of degradable plastic. The research method consists of several stages, cellulose fiber preparation, degradable plastic synthesis and plastic characterization. The result showed tensile strength of plastic with corn cob and sugarcane bagasse filler was 6.37–11.5 MPa and 9.70–16.47 MPa, respectively. The compound composition test through Fourier Transformation Infra-Red (FTIR) exhibited hydrophilic behavior, hence plastic easily degraded by soil. Differential Scanning Calorimetry (DSC) shows that degradable plastic with corn cob fiber filler denoted a melting point of 163.84 ℃, while sugarcane bagasse fiber filler at 163.47 ℃. Thermogravimetric Analysis (TGA) analysis indicated degradable plastic had a good thermal stability. Scanning Electron Microscopy (SEM) exhibited few white lumps and indentations on the surface, indicating that the solubility was not homogeny and could be due to the influence of stirring process. In term of ability to absorb water, both plastic with fiber filler had a small water absorption with a range of 5–6%. Melt Flow Rate (MFR) analysis of degradable plastics with corn cob fiber and sugarcane bagasse pointed the value that was suitable for injection molding processing technique. The degradation of both plastics ranged about 50–85 days to completely decomposed naturally in soil, as supported by FTIR analysis.&lt;/p&gt; &lt;/abstract&gt;

Viscoelastic–plastic stability analysis of large-section quasi-rectangular pipe-jacking tunnel under-passing box culvert

Viscoelastic–plastic stability analysis of large-section quasi-rectangular pipe-jacking tunnel under-passing box culvert

Assessment of Ratcheting in SGDHR Pipe Bend based on Linear and Bi-linear Analysis

The possibility of ratcheting in the 200 NB pipe bends of the SGDHR system has been analytically studied. Elastic analysis with a sustained load on internal pressure at 7 bars and deformation-controlled cyclic displacement of 20 mm amplitude is carried out. The results suggest that the outer surface of the pipe bend crown region becomes the potential location for the cyclic accumulation of strain. The ratcheting possibility is also verified using the conventional design standard procedure of RCC MRx and ASME. It is observed that ASME is more conservative than RCC MRx, and predicts lower displacement to initiate ratcheting. Elasto-perfectly plastic analysis carried out at 7 bar pressure and various displacements shows an elastic shakedown at lower displacements. Initiation of ratcheting at 7 bars is predicted at 35 mm and 18 mm displacements at room temperature and 600 ℃, respectively. It is observed that the ratcheting strains stabilize at higher cycles. The magnitude of the stabilized strain and number of cycles increases with an increase in the amplitude of cyclic loading for a prototype pipe bend.

Study of cyclic plastic zone ahead of the fatigue crack tip using Digital Image Correlation system

Structural components are susceptible to cyclic loadings during their operation. They are more prone to failure due to localized plastic deformation. The plastically deformed region ahead of the crack tip due to fatigue loading is the important factor responsible for fatigue crack propagation. The plastically deformed region is separated into monotonic and cyclic plastic zones. The cyclic plastic zone (CPZ) is approximately 1/3rd to 1/4th of the monotonic plastic zone (MPZ). The existing analytical expressions to calculate the size of the CPZ are based on elastic perfectly plastic analysis. In this paper, an experimental technique, namely 3D-Digital image correlation (DIC), is used to evaluate the size of the CPZ during the fatigue crack growth rate (FCGR) tests on CT specimens. The DIC system having two cameras is used to capture high-resolution images of crack region of CT specimen surface during the FCGR tests. The FCGR tests are carried out on nuclear piping material steel SA333Gr6 under constant load range and constant load ratio. The post-processing of DIC images revealed an asymmetric butterfly-type shape of the cyclic plastic zone. The DIC evaluated CPZ was compared with the CPZ obtained by a calibrated cyclic plasticity material model-based finite element (FE) analysis. It was observed that the average difference between DIC evaluated experimental CPZ and CPZ calculated by plane stress-based FE analysis is about 5%.

Elastic–Plastic Analysis of Rigid Passive Piles in Two-Layered Soils

The paper analyses the behavior of a rigid passive pile embedded in a soil profile consisting of a stable layer underlying an unstable layer subjected to a uniform soil displacement. Pile-soil interaction is considered by modeling the soil by a series of elastic–plastic springs along the pile shaft. The modulus of horizontal subgrade reaction is assumed to linearly increase with depth in the unstable layer and constant in the stable one. The ultimate soil resistance is assumed increasing with depth in both layers. The results of analysis are presented in dimensionless form in terms of shear force developed at the slip surface as a function of the pile embedment into the stable layer and the distribution of soil characteristics over depth. The method allows capturing pile response not only at the soil ultimate state but also at the intermediate states. Specifically, the governing equations for the elastic, elastic–plastic and plastic cases are discussed and, whenever possible, a set of closed-form expressions is provided to estimate the maximum bending moment along the shaft and the pile head deflection, so that for an assigned value of the required stabilizing force both ultimate and serviceability limit state of the pile can be checked. A numerical example is given to illustrate the application of the proposed procedure.

COMPARATIVE ASSESSMENT OF CLINICAL AND TECHNOLOGICAL PROPERTIES OF ASHLESS ACRYLIC PLASTICS

The aim of this study was to conduct a comparative evaluation of the clinical and technological properties of the proposed domestic ashless acrylic plastic.&#x0D; Materials and methods. In collaboration with colleagues from the accredited research laboratory of dental materials of the Stoma company in Kharkiv, Ukraine, we conducted a comprehensive comparative analysis of ashless cold-cured plastics. The study included the assessment of both clinical and technical characteristics, including structuring temperature, mixing time, curing time, consistency, and viscosity. o gather laboratory data, various dental materials were used: "Modeplast" (Stoma JSC, Ukraine), "Pi-Ku-Plast" (Bredent, Germany), "Cerin" (Spofa Dental, Czech Republic), and "Txowax" (Yeti Dental, Germany). We measured the properties on 125 samples (25 from each material) according to the method of use provided by the international standard ISO 10139-2018.&#x0D; Results. The study has revealed that the Modeplast material, manufactured by Stoma, exhibits a lower structuring temperature, specifically 2.3°C lower than Pi-Ku-Plast (Bredent), 1.2°C lower than Cerin (Spofa Dental), and 0.7°C lower than Txowax (Yeti Dental). Furthermore, the mixing time for Modeplast was notably shorter, being 7.5 seconds faster than Pi-Ku-Plast (Bredent), 1.5 seconds faster than Cerin (Spofa Dental), and 5.2 seconds faster than Txowax (Yeti Dental). In terms of hardening, Modeplast demonstrated the highest level of hardening compared to materials from other manufacturers. The consistency of Modeplast was stronger and harder, 1.5 mm harder than Pi-Ku-Plast (Bredent) demonstrated, 3.3 mm harder than Cerin (Spofa Dental) had and 1.7 mm harder than Txowax (Yeti Dental) showed. In terms of viscosity, Modeplast met the ISO-10139 standards, although it was 1.8 kJ/cm² lower in viscosity than Pi-Ku-Plast (Bredent) and 1.1 kJ/cm² lower in viscosity than Cerin (Spofa Dental). However, it was 0.2 kJ/cm² more viscous than Txowax (Yeti Dental).&#x0D; The kneading time for Modeplast was notably shorter, indicating higher efficiency in usage. Regarding the curing process, Modeplast exhibited superior performance, proving to be faster than other materials. The consistency of Modeplast was characterized by increased strength and hardness when compared to its counterparts. In the aspect of viscosity, Modeplast adhered to ISO-10139 standards and demonstrated satisfactory performance, albeit with some distinctions from other materials.&#x0D; Conclusion. Thus, our studies has demonstrated that Modeplast possesses superior technical characteristics, making it a compelling factor in the selection of dental materials for various components.

Global analysis of marine plastics and implications of control measure strategies

Plastic pollution is a global environmental crisis that threatens marine ecosystems and human health. This study provides a comprehensive analysis of the current state of plastic pollution in oceans worldwide. We examined data on global plastic production, annual estimates of plastic emissions to oceans from different countries, surface plastic mass by ocean basin, the share of global plastic waste emitted to the ocean, the share of ocean plastics that come from the largest emitting rivers, microplastics in the surface ocean, and plastic mass and particles across the world surface ocean. Our analysis revealed alarming trends, such as the significant increase in plastic production since the 1950s and the projected estimate of up to 12,000 million metric tons of plastic waste in the natural environment by 2050. Additionally, we found that more than 1000 rivers account for 80% of global annual emissions, with Asia contributing the highest estimate of plastic emissions, followed by Africa, South America, North America, Europe, and Oceania. Furthermore, our findings showed that the largest contributors to ocean plastic waste are macroplastics, mesoplastics, and microplastics, with small microplastics dominating the percentage of surface ocean plastic by particle count. The recycling and reuse of waste plastics implement the concept of sustainable development of recycling and offsets the carbon emissions in the environment, potentially obtaining more carbon credits. Our findings highlight the urgent need for coordinated global efforts to reduce plastic waste and prevent further harm to our oceans, incorporating recycling and reuse strategies as key components of comprehensive control measures.

Performance Research and Application Progress of Thermal Insulation Materials for Cold Storage

The thermal insulation performance of thermal insulation materials for cold storage has a great influence on the energy saving of cold storage, so many scholars have done a lot of research on it. This paper summarizes the production, application, and performance analysis of Polyurethane foam plastics (PU), Expanded polystyrene (EPS), Extruded polystyrene (XPS), and rock wool for cold storage, and summarizes the thermal insulation application of civil-type cold storage, steel structure cold storage, prefabricated cold storage and cold storage pipeline, as well as the cold storage anti-cold bridge measures.

Mid-infrared supermirrors with finesse exceeding 400 000

For trace gas sensing and precision spectroscopy, optical cavities incorporating low-loss mirrors are indispensable for path length and optical intensity enhancement. Optical interference coatings in the visible and near-infrared (NIR) spectral regions have achieved total optical losses below 2 parts per million (ppm), enabling a cavity finesse in excess of 1 million. However, such advancements have been lacking in the mid-infrared (MIR), despite substantial scientific interest. Here, we demonstrate a significant breakthrough in high-performance MIR mirrors, reporting substrate-transferred single-crystal interference coatings capable of cavity finesse values from 200 000 to 400 000 near 4.5 µm, with excess optical losses (scatter and absorption) below 5 ppm. In a first proof-of-concept demonstration, we achieve the lowest noise-equivalent absorption in a linear cavity ring-down spectrometer normalized by cavity length. This substantial improvement in performance will unlock a rich variety of MIR applications for atmospheric transport and environmental sciences, detection of fugitive emissions, process gas monitoring, breath-gas analysis, and verification of biogenic fuels and plastics.

Stress and Couple Stress Concentration and Plastic Rotation Analysis of Local Micro-structure of Flat Plate

In classical elasticity, the analytical solution of the stress concentration coefficient at the edge of a circular plate hole is 3, but the experimental result is less than 3, and the fatigue theory still has no theoretical answer to the mechanism of fatigue. For the problem that the stress concentration coefficient is less than 3, the stress and couple stress concentration at the hole edge of a circular plate hole is calculated using generalized elasticity. On this basis, the strain-elastic and rotation-plastic theory is put forward, and an example of a flat wedge structure is used to demonstrate the plastic curvature of the contact boundary of different materials to explain the mechanism of fatigue. Through calculation, it is found that there is a stress concentration at the edge of the hole and a couple of stress concentrations, and the stress concentration coefficient decreases with the decrease of the hole diameter. For flat wedge structures, the plastic curvature is mainly concentrated on the contact surface of different materials, and the plastic curvature will increase obviously when the boundary changes. This paper provides a new idea for the development of fatigue theory.

An efficient approach to tackle the challenges of LDFE modelling of plate anchor-chain system during installation process

This technical note presents an efficient approach to tackle the challenges in large deformation finite element (LDFE) modelling of plate anchor-chain system during installation process. This is realised by using a local coordinate system based on the displacement-control technique, where the chain loading direction is updated compatibly with the anchor behaviour at each calculation increment. The effectiveness of the approach is demonstrated through two analysis examples that model the anchor installation (keying) process. The results agree well with established analytical solution based on plasticity analysis, which was developed based on deeply embedded anchor. The LDFE results numerically testify that plate anchors with well-designed padeye position are able to dive into deeper seabed under chain loading, where this concept was only suggested in previous analytical and plasticity analysis.

Seasonal variation in C:N:P stoichiometry, nonstructural carbohydrates, and carbon isotopes of two coniferous pioneer tree species in subtropical China.

The characteristics of C:N:P stoichiometry, nonstructural carbohydrate (NSC) content, and C stable isotopes and their relationships affect plant responses to environmental changes and are critical to understanding the ecosystem carbon and water cycles. We investigated the water use strategies and physiological changes of two pioneer tree species (Pinus armandii and Pinus yunnanensis) in response to seasonal drought in subtropical China. The seasonal variation in needle δ13C values, C:N:P stoichiometry, and NSC contents of the two tree species were studied in 25-year-old plantation in central Yunnan Province. The needle δ13C values of both species were highest in summer. Soluble sugars, starch and NSC content of the two tree species decreased from spring to winter, while there was no significant difference in the seasonal variation of soluble sugars/starch in P. armandii needles, the maximum soluble sugars/starch in P. yunnanensis needles was in autumn. In addition, the C, N, and P contents of the needles and the C:N and C:P ratios of the two species showed different seasonal fluctuations, whereas the N:P ratio decreased with the season. The C:N:P stoichiometry and NSC content of the needles showed significant correlations, whereas the needle δ13C was weakly correlated with C:N:P stoichiometry and NSC content. Phenotypic plasticity analysis and principal component analysis revealed that the needle nutrient characteristics (NSC and P contents and N:P ratio) and needle δ13C values were critical indicators of physiological adaptation strategies of P. armandii and P. yunnanensis for coping with seasonal variation. These results increase our understanding of the water-use characteristics of the two pioneer tree species and the dynamic balance between the NSC, C, N, and P contents of the needles.

MMP3C: an in-silico framework to depict cancer metabolic plasticity using gene expression profiles.

Metabolic plasticity enables cancer cells to meet divergent demands for tumorigenesis, metastasis and drug resistance. Landscape analysis of tumor metabolic plasticity spanning different cancer types, in particular, metabolic crosstalk within cell subpopulations, remains scarce. Therefore, we proposed a new in-silico framework, termed as MMP3C (Modeling Metabolic Plasticity by Pathway Pairwise Comparison), to depict tumor metabolic plasticity based on transcriptome data. Next, we performed an extensive metabo-plastic analysis of over 6000 tumors comprising 13 cancer types. The metabolic plasticity within distinct cell subpopulations, particularly interplay with tumor microenvironment, were explored at single-cell resolution. Ultimately, the metabo-plastic events were screened out for multiple clinical applications via machine learning methods. The pilot research indicated that 6 out of 13 cancer types exhibited signs of the Warburg effect, implying its high reliability and robustness. Across 13 cancer types, high metabolic organized heterogeneity was found, and four metabo-plastic subtypes were determined, which link to distinct immune and metabolism patterns impacting prognosis. Moreover, MMP3C analysis of approximately 60000 single cells of eight breast cancer patients unveiled several metabo-plastic events correlated to tumorigenesis, metastasis and immunosuppression. Notably, the metabolic features screened out by MMP3C are potential biomarkers for diagnosis, tumor classification and prognosis. MMP3C is a practical cross-platform tool to capture tumor metabolic plasticity, and our study unveiled a core set of metabo-plastic pairs among diverse cancer types, which provides bases toward improving response and overcoming resistance in cancer therapy.

Viscos-elastic-plastic solution for deep buried tunnels considering tunnel face effect and sequential installation of double linings

Tunnels excavated in soft rock under high in situ stress are usually accompanied by large time-dependent deformation, slow convergence, and long periods of increased support load due to the strong rheological properties of the surrounding rock. This paper presents a time-dependent solution for deeply buried supported circular tunnels excavated in viscoelastic-plastic strain-softening rock masses, in which both the whole process of longitudinal excavation and the sequential installation of two elastic linings are considered. In the solution, the surrounding rock obeys a Burger-creep viscous elastic–plastic strain-softening model and two stages, referring to the “tunnel face influence stage” and the “creep stage”, are divided to derive the explicit expressions of the time-dependent tunnel convergences and support loads, in which the former stage accounts for the effect of stress release based on the elastic–plastic analysis, and the latter concentrates on the long-term response induced by the viscous behavior of the ground. To account for the different rock qualities, tunnel face advance rates, and lining tunnel support locations, the elastic–plastic strain-softening solution in the former stage is divided into three cases and the viscos-elastic–plastic solution in the creep stage includes two sub-solutions depending on the evolutions of stress paths being considered or not. For validation purposes, the provided analytical solutions are compared with the numerical results by finite-difference simulations and previous solutions. Following that, parametric studies are conducted to compare the stresses, deformations, and support loads under different stages and solutions. Finally, to further verify the applicability of the solutions in practical tunnels, the convergences, support loads and lining stresses of a typical tunnel cross-section in the Saint Martin La Porte access adit are successfully predicted. Overall, the proposed solutions in this study provide a profitable idea for deriving various viscoelastic-plastic or elasto-viscoplastic explicit solutions that can simultaneously account for both the rock rheology and tunnel face effect.