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State-based peridynamics (SPD) is effective for simulating fracture and damage in different materials. However, the solutions may suffer from numerical instabilities, particularly for strong nonlinearity cases or large displacement cases, leading to inaccurate predictions or oscillation in responses. This paper proposed a novel practical method to solve the instability problem of SPD based on stress equilibrium equation, referred to herein as the stress correction method (SCM). A correction force is applied on each SPD point surrounding the loading points. The correction force is defined as the difference between an internal force obtained by the stress equilibrium equation and that obtained by the force states of the SPD. Four examples are presented herein to verify the accuracy and stability of the proposed method in various conditions, e.g. static and dynamic analyses of elastic and plastic models subjected to force and displacement boundary conditions. [ABSTRACT FROM AUTHOR]

Energy method is an essential theoretical approach to analyze plastic forming, which is widely used in rolling process. An analysis model for vertical rolling process is established according to energy theory. By using global weighted method firstly, the 3D continuous velocity field, strain rate field and the corresponding power functional are proposed. The unknown variables are calculated numerically based on the principle of minimum energy. Then, deformation parameters and rolling force are determined. The analysis on specific examples shows that the theoretical prediction value of weighted model is in good agreement with experimental results. Moreover, the effects of several shape and rolling parameters on rolling force, rolling power and edge deformation are studied. Both the width reduction rate and initial slab thickness have significant influences on dog-bone size and rolling force. A wider slab slightly increases the nonuniformity of dog-bone deformation. And the increase of vertical roller radius can weaken the edge deformation. [ABSTRACT FROM AUTHOR]

Foundation piles can be used as a means for increasing the capacity of the foundations under static loads or, at the same time, can be regarded as an additional source of energy dissipation for the structure during strong motion. Under multi-axial loading, the ultimate capacity of a pile group is closely connected with the attainment of the flexural strength in the piles, which can in turn vary significantly according to the specific load path followed. Nonetheless, the design of piled foundations is still based on an independent evaluation of the vertical and horizontal capacities without accounting for the interaction between the several loads acting on the footing. To overcome this issue, in this paper a simplified numerical procedure for evaluating the capacity of piled foundations under multi-axial loading conditions is developed, which is based on the lower bound theorem of plastic limit analysis. On the basis of the numerical results, an analytical model of ultimate limit state surface is proposed, representing the force combinations that activate global plastic mechanisms of the soil–piles system. The identification of the ultimate surface necessitates a limited number of parameters having a clear physical meaning. The ultimate surface can lead to an optimised design of pile groups, allowing for a better control of the ultimate capacity as a function of the expected load patterns under static and dynamic conditions. In structural analysis, the ultimate surface can also be regarded as a bounding surface of a plasticity-based macroelement for piled foundations to account for the nonlinear features of the soil–pile system. [ABSTRACT FROM AUTHOR]

Three asymmetric cracks were postulated at the circumferential horizontal weld H7 of a boiling water reactor type 5 core shroud after 25 years of operation. They were arranged in an irregular distribution with different depths. Unstable crack propagation can be induced when an earthquake and a loss of coolant accident take place. In this paper, a ductile failure analysis has been reported. It has been done following an elastoplastic analysis and a plastic limit load analysis. The crack conditions after 30 and 60 years of operation were evaluated. The results show that the core shroud will keep its structural integrity during sixty years under normal conditions of operation. On the other hand, its operational life is reduced five years under failure conditions. In general terms, the methodology, which has been developed, can be applied for any number of circumferential cracks located in the same cross section. Fast and reliable outputs can be obtained. It can be applied in any moment of the life of the plant, to support the decision on "Use as is", "Mandatory Repair", or "Estimation of the remaining life." [ABSTRACT FROM AUTHOR]

The seismic events that occurred in the last decades have highlighted the importance of a correct design of the structures in seismic areas and the seismic inadequacy of a large part of the built heritage. Modern codes are still lacking in terms of prescriptions for the evaluation of the seismic performance of existing buildings. The present work proposes a simplified method for the evaluation of the demand in terms of plastic rotation for short links of steel Eccentrically Braced Frames (EBFs). A relationship for the evaluation of the demand, that exploits elastic analysis and rigid-plastic analysis extended to the second-order effects, is proposed. The calibration of this relationship was carried out on 420 EBFs equipped with short links designed according to three different approaches. The 420 frames have been also used to analyze the behavior in the plastic range of EBF type structures equipped with short links. The study also provides an extensive analysis on the influence of plastic redistribution capacity on the demand in terms of plastic rotations of links, corresponding to the achievement of the maximum bearing capacity. The obtained relation can be exploited as an assessment tool by comparing the demand with the link capacity. Moreover, from a performance-based design point of view, the same can be used for predicting the required ultimate plastic rotation as a function of the plastic redistribution capacity of the structure. [ABSTRACT FROM AUTHOR]

This paper presents research on the influence of material anisotropy caused by the technological process of its manufacturing on the plastic properties of the material. In the experimental study, samples cut from an AISI 304L rolled sheet in the rolling direction, transverse, and at a 45° angle to the rolling direction were predeformed by axial deformation at 18 and 30%. The principal specimens extracted from the pre-deformed plates, cut in the longitudinal, transverse, and 45° angle directions, were subjected to tensile loading until failure. The data thus obtained allowed for the analysis of the plastic flow mechanism using the author's calculation procedure. The CR coefficient analysis provided information on the state of plastic anisotropy caused by the pre-deformation. For the specimens predeformed in the rolling direction, plastic flow isotropy was observed at a strain of 35%. For the specimens predeformed in the transverse direction—the plastic anisotropy is completely removed at a strain of 33%. For the specimens predeformed at 45 degrees to the rolling direction, it was found that the strain completely removed the plastic anisotropy induced by rolling. The calculations provided information that due to an abrupt change in the strain path, a strong reconfiguration of the plastic flow mechanism occurs, causing the removal of anisotropy generated by rolling. [ABSTRACT FROM AUTHOR]

The global energy demand is expected to increase by 30% within the next two decades. Plastic thermochemical recycling is a potential alternative to meet this tremendous demand because of its availability and high heating value. Polypropylene (PP) and polyethylene (PE) are considered in this study because of their substantial worldwide availability in the category of plastic wastes. Two cases were modeled to produce hydrogen from the waste plastics using Aspen Plus®. Case 1 is the base design containing three main processes (plastic gasification, syngas conversion, and acid gas removal), where the results were validated with the literature. On the other hand, case 2 integrates the plastic gasification with steam methane reforming (SMR) to enhance the overall hydrogen production. The two cases were then analyzed in terms of syngas heating values, hydrogen production rates, energy efficiency, greenhouse gas emissions, and process economics. The results reveal that case 2 produces 5.6% more hydrogen than case 1. The overall process efficiency was enhanced by 4.13%. Case 2 reduces the CO2 specific emissions by 4.0% and lowers the hydrogen production cost by 29%. This substantial reduction in the H2 production cost confirms the dominance of the integrated model over the standalone plastic gasification model. [ABSTRACT FROM AUTHOR]

The European Union (EU) aspires to be an important global agenda-setter on how to treat and regulate the growing plastics problem. We present an analysis of the plastic policy narratives shaping European plastics governance, in particular through the European Commission's Plastics Strategy. Our aim is to first uncover the policy narratives at play, and then examine how actors make use of those narratives through strategic construction. Based on interviews with key stakeholders and document analysis, we identify four narratives: fossil feedstock dependency, resource inefficiency, pollution, and toxicity. We find that the resource inefficiency and pollution narratives figure most prominently in European plastics governance, and that the circular economy is being advanced as a policy solution that cuts across the different narratives. However, surface agreement on the need for 'circularity' hides deeper-lying ideological divisions over what exactly the circular economy means and the different directions this implies for plastics governance. [ABSTRACT FROM AUTHOR]

Plastics are often used in every industry today due to their light weight, durable and insulating materials. As a result of the widespread use of petroleum-based plastics, there is also an inevitable increase in the amount of waste. Therefore, it is important to determine the effects of plastics on the environment. In this study, the life cycle assessment of couplings, which are commonly used pipe fittings in irrigation and drinking water pipes, was investigated. The environmental effects of the production and disposal stages of the coupling were determined using the Eco-Indicator 99 method of SimaPro 8.0.2 software. At the end of the study, the highest environmental impact occurred during the production of the coupling (79.9%) and it was determined that the most important factor causing this was the use of polypropylene plastics (48.1%). [ABSTRACT FROM AUTHOR]

Asia currently faces a serious crisis involving plastic wastes. Efforts to curb plastic waste in the region are mostly hampered by inadequate recycling infrastructure, unsustainable disposal practice, low level of recycling awareness and persistent shipping of large amounts of waste from developed countries to the region. The ban on plastic waste import by China in 2017 worsened the situation by causing unsustainable shipping of waste from high plastic waste-generating countries such as Japan to alternate destinations in Southeast and East Asia. The Japanese government is frantically looking for options to manage plastic waste piling up on the domestic front. Malaysia became one of the leading alternative destinations for plastic waste after the ban by China. This work is aimed at conducting a comparative analysis of plastic recycling policies and legislations between Malaysia and Japan to yield synergistic solutions between the two countries to combat the current predicament. The comparison will signify two typical development patterns in developed countries and developing countries and will be able elucidate future directions for other countries with similar policy and legislative transitions in the region. A set of nine criteria was employed to critically evaluate the policies and legislations of both countries. Barriers faced by both countries in plastic recycling are outlined and recommendations are proposed to overcome those barriers on the domestic front. Two strategies proposed to be jointly developed by both countries are enhancement of extended producer responsibility (EPR) through a regional policy platform and collaboration in establishing joint Ecotowns. [ABSTRACT FROM AUTHOR]

One of the challenging tasks for governments is to curtail the production and consumption of single-use plastic bags. Despite multiple advantages of plastic and its ubiquity, the environmental damage of single-use plastic bags is irreversible. However, policy intervention by the governments is also a need of the time to reduce its production and consumption. This study provides a strategic analysis of government policy options regarding the ban on single-use plastic production in Pakistan. A game-theoretic model is developed to examine the behavior of plastic bag producers vis-à-vis the government's climate change policy. The study concludes that game theory is very effective in analyzing the efficient promulgation and productive implementation of environmental management policy regarding banning single-use plastic in Pakistan. [ABSTRACT FROM AUTHOR]

Plastic contamination in the environment is common but the characterisation of plastic ingested by fish in different environments is lacking. Hence, a meta-analysis was conducted to identify the prevalence of plastic ingested by fish globally. Based on a qualitative analysis of plastic size, it was determined that small microplastics (<1 mm) are predominantly ingested by fish globally. Furthermore, our meta-analysis revealed that plastic fibres (70.6%) and fragments (19.3%) were the most prevalent plastic components ingested by fish, while blue (24.2%) and black (18.0%) coloured plastic were the most abundant. Polyethylene (15.7%) and polyester (11.6%) were the most abundant polymers. Mixed-effect models were employed to identify the effects of the moderators (sampling environment, plastic size, digestive organs examined, and sampling continents) on the prevalence of plastic shape, colour, and polymer type. Among the moderators, only the sampling environment and continent contributed to a significant difference between subgroups in plastic shape and polymer type. [ABSTRACT FROM AUTHOR]

The evaluation of ship strength during the hull structure design stage is essential for structural safety. Additionally, plate is one of the basic structural members of the hull, it is important to analyze and predict the ultimate strength. The curved plate used for shipbuilding must be able to withstand repeated axial loads and complex loads, and stability needs to be confirmed through ultimate strength analysis. In general situations, the magnitude of the transverse compression is smaller than that of the longitudinal and combined loads, but transverse compression causes different physical behaviors from the longitudinal load state, which affects the ultimate strength, so study on the ultimate strength of the curved-plate under transverse compression is essential. Therefore, in this paper, a curved plate under transverse compressive load was selected as a subject, and the ultimate strength of the curved plate under the corresponding compression condition was predicted using a deep learning model. To obtain the training data for the deep-learning model, 4050 cases were selected and analyzed using the ANSYS. The accuracy of the model was verified by comparing the results predicted by the model and empirical equations with those of the FEM analysis. The study shows that it is possible to consider the ultimate strength more efficiently in the initial design stage of the ship. [ABSTRACT FROM AUTHOR]

The process of designing a longwall powered support is extremely complex and requires many operations related to the creation of a complete machine. The powered support section is one of the basic elements of the longwall system. It acts as protection for the working space and takes part in the process of excavating and transporting the spoil. The implementation of the support that meets the guidelines of the manufacturer and user requires an endurance analysis at the design stage conducted according to the regulations in force. The main objective of this research, pursued by the authors, was to perform the analysis of the ultimate strength of selected elements of the designed powered support section. The research was carried out with the use of special software that uses the finite element method. This article presents the analysis of the strength limits conducted with the help of the finite element method, determining the strength of selected elements of the longwall support section. The solutions proposed by the authors include changes in the structure and properties of the material in the design process. The aim of the proposed solution was to obtain a model with strength value that meets safety standards. The research results are a valuable source of knowledge for designers. Solutions of this type set examples for spatial models of the longwall support section being designed currently. The analysis presented in the article, together with the results of the research and the conclusions resulting from them, may improve the safety and effectiveness of powered supports. [ABSTRACT FROM AUTHOR]

This paper presents a review of selected tunnel stability models that have been developed and used in calculating the minimum tunnel face pressure as described by original authors. Furthermore, this paper provides a comparison of required tunnel face pressure obtained from analytical models, based either on limit equilibrium method or the limit analysis method (upper bound theorem) and numerical models using the finite element method. The numerical results are presented in charts for the comparative study to discuss the influence of cover depth to tunnel diameter ratio (C/D), internal friction of the soil (φ), and cohesion (c) on normalized support pressure ( p u / γ D ) for each model. To verify the accuracy of the selected models, a comparison of the results of seven tunnel stability models with the results of the physical models is carried out. In a ground composed of two layers, a comparison of the required tunnel face pressure is presented. The results show that the wedge–silo models provide higher support pressure than the conical block models. Moreover, the support pressure using the conical block models is only dependent on the friction angle and not on the C/D ratio. Finally, the results of wedge-silo models indicate more significant dependence of the required support pressure on the C/D ratio especially for the lower friction angle. [ABSTRACT FROM AUTHOR]

Describing the material flow stress and the associated uncertainty is essential for the plastic stochastic structural analysis. In this context, a data-driven approach-heteroscedastic sparse Gaussian process regression (HSGPR) with enhanced efficiency is introduced to model the material flow stress. Different from other machine learning approaches, e.g. artificial neural network (ANN), which only estimate the deterministic flow stress, the HSGPR model can capture the flow stress and its uncertainty simultaneously from the dataset. For validating the proposed model, the experimental data of the Al 6061 alloy is used here. Without setting a priori assumption on the mathematical expression, the proposed HSGPR-based flow stress model can produce a better prediction of the experimental stress data than the ANN model, the conventional GPR model, and Johnson Cook model at elevated temperatures. After the HSGPR-based flow stress model is implemented into finite element analysis, two numerical examples with synthetic material properties are performed to demonstrate the model's capability in stochastic plastic structural analysis. The results have shown that with sufficient data, the distribution of the structural load carrying capacity at elevated temperatures and the variation of load–displacement curves during the loading and unloading processes can be accurately predicted by the HSGPR-based flow stress model. [ABSTRACT FROM AUTHOR]

This paper is concerned with an incremental iterative force recovery method in the second-order plastic hinge analysis of steel frames mainly modelled by a single element per member. Second-order beam-column elements are preferred in the direct analysis of steel frames due to their high accuracy and efficiency. However, formulations of these elements are complicated, and therefore they may have a problem of getting element force recovery in inelastic analysis. To overcome this difficulty, a novel incremental iterative force recovery method for second-order beam-column elements is proposed to perform plastic hinge analysis. The proposed method is derived more strictly and has good performance. Also, the section assemblage approach and the refined plastic hinge method are adopted in this study to consider the gradual degradation of section stiffness in the plastic hinge analysis. To verify the accuracy, efficiency and robustness of the proposed method, several benchmark examples are analyzed by the proposed method and compared with solutions reported by early researchers. [ABSTRACT FROM AUTHOR]

The electrical curtain board (ECB) is constituted of parallel linear electrodes deposited on a dielectric layer plate and supplied by a poly-phase electrical voltage. This paper reports a study of the movement of Polyvinyl Chloride (PVC) µm-size particles on such an ECB. The experimental setup comprised three ECB plates of different inter-electrodes spacing, and a homemade electric supply. Obtained results show that it is possible to move the quasi-totality of the particles on the ECB if adequate values are given to the voltage, the frequency and the inter-electrodes spacing. [ABSTRACT FROM AUTHOR]

Correction of the stress–strain curve in the strained specimens after necking is one of the remarkable issues in mechanical engineering. The corrected curve strain–stress is needed to perform plastic or post-necking analysis in metals' large deformation issues. The stress becomes triaxle during the specimen's necking and includes tangential, radial, and circumferential stress components. The stress distribution is ununiformed in the necking area, and the actual stress is not obtained by dividing the force by the initial section surface. Instead, it is obtained by two different equations before and after necking. This research uses the surface strain method for a copper rod specimen on which several points are specified. The surface strain is obtained at any moment by measuring the distance between these points during the strain test using the image-processing technique. After computing the surface and radial strain, the correction factor is calculated using the relevant equations for determining the corrected actual stress values. The results are verified with the well-known results in the literature as presented by Davidenkov and Bridgham. Further, the finite element method is employed to perform numerical analysis. The commercial software ABAQUS is used to verify the results from image process analysis. The results show that determining the material model constants using the surface strain method does not require measurement of the necking radius at each moment during testing. Thus, this method outperforms the other ones in terms of simplicity, time, and accuracy. Additionally, the experimental and numerical are employed to present the corrected post-necking stress–strain curve. [ABSTRACT FROM AUTHOR]

The carbonation characteristics of marine biological attachment on concrete of offshore artificial islands were studied. The finite element analysis method is adopted to build a finite element analysis model for the carbonation characteristics of the marine organism attachment to the marine artificial island concrete under different temperature environments. By the analysis of the plastic displacement of the carbonation characteristics of the marine artificial island concrete caused by the lateral displacement before yielding and the marine organism attachment. The hysteretic curves of the carbonation characteristics of the marine organism adhesion to the concrete of the offshore artificial island at 0 degrees, 10 degrees, 20 degrees and 30 degrees and the degradation curves of the carbonation characteristics of the marine organism adhesion to the concrete of the offshore artificial island are compared respectively. The test results show that the marine organism adhesion at different temperatures shows different characteristics to the carbonation characteristics of the concrete of the offshore artificial island. The degradation curve of the carbonation characteristics of the marine artificial island concrete due to the attachment of marine organisms is stable, the curve will eventually stabilise at the corresponding degradation value in the descending process, indicating the stable point of performance. [ABSTRACT FROM AUTHOR]

The viability of converting wood chips and plastic to power via compact integrated catalytic fast/slow pyrolysis, combustor, and Stirling engine technologies was determined using modeling analysis. Aspen simulations followed by sizing analysis were performed to determine the size, weight, and net energy efficiency of upgrading wood chips and plastic to power using a compact energy system with a feedstock processing capacity of 1 kg h−1. The equipment and tooling to fabricate individual components of a compact energy system were identified. The total costs of fabricating all the individual components of compact energy systems were assessed. A discounted cash flow analysis with an internal rate of return of 20% was used to assess the minimum selling price of compact energy systems. The specific energy (Wh kg−1) of the compact catalytic fast pyrolysis system, compact slow pyrolysis system, and compact plastic conversion system were assessed at 20, 29, and 63, respectively. The assessed capital and annual costs of manufacturing 10 000 compact energy systems per year were $51 million and about $11 to $13 million, respectively. The calculated minimum selling price of a catalytic fast pyrolysis system, a compact slow pyrolysis system, and a compact plastic conversion system were $3055, $3021, and $2980, respectively. The sensitivity analysis results showed that the internal rate of return, capital investment, materials cost, annual operating costs, and capital cost have significant impacts on the minimum selling price of compact energy systems. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

A constitutive model of confined ultra-high-performance concrete (UHPC) was developed based on the theoretical and regression analyses. This constitutive model could be applied to finite element analysis (FEA) according to the comparison of plastic damage analysis and load–displacement curves. A total of 25 stirrup-confined UHPC columns were created through FEA modeling. The variables included stirrup spacing, stirrup configuration, steel fiber volume, and longitudinal reinforcement ratio. The load–displacement curves and the plastic damage region of the UHPC columns were illustrated and analyzed. Moreover, parametric analysis was conducted to evaluate the effects of the aforementioned parameters. The improvement in the bearing capacity and ductility of the UHPC columns resulting from the reduction in stirrup spacing and increase in steel fiber volume indicated that the columns were significantly influenced by the stirrup spacing, stirrup configuration, and steel fiber volume. [ABSTRACT FROM AUTHOR]

Despite the great benefits of plastics in different aspects of life and due to the increase in plastic production and use, plastic wastes are becoming a major environmental concern. It is well known that inappropriate use and disposal lead to the accumulation of plastic litter in different aquatic environments. Microbial biofilm is able to develop on the surface of plastics (plastisphere) in aquatic environments over time. The aim of this study was to describe the bacterial communities associated with plastics in freshwater. Thus, in our first test, a total of six self-designed plastic colonizers were submerged under the surface of the water in Vácszentlászló lake, located in central Hungary, for a period of 3 months. Two plastic colonizers were cultivated monthly. Associated microbial communities were then analyzed as follows: (a) bacterial communities were studied by amplicon sequencing and (b) culturable bacteria were isolated from plastic surfaces and identified by 16S rRNA gene sequencing. Coinciding with these analyses of plastic colonizing communities, surface water samples from the lake were also taken, and in a second test, other materials (eg. wood, glass) associated bacterial communities were also investigated with the same methods. Amplicon sequencing showed notable differences between the plastic and other materials colonizing, and lake waterborne microbial community composition. Using the LB agar, no novel species were found; however, several known pathogenic species were identified. The self-designed plastic colonizer was successfully used during the winter over a 3-month period, suggesting that it could be an appropriate method of choice to study microplastic-associated microbes for longer periods and in variable environmental conditions. [ABSTRACT FROM AUTHOR]

This work reports the potential impact of extremophiles in resolving one of the biggest contemporary ecological problem - accumulation of huge amounts of plastic pollutants. Lye (C1) and water mud (C2) from Atanasovsko ezero, Bulgarian salterns were enriched for 2 weeks in a mineral salt medium provided with four synthetic plastics, Polycaprolactone (PCL), Polyvinyl alcohol (PVA), Polystyrene (PS), and Polypropylene (PP). Esterase activity was established for C1 on PVA and for C2 - on PCL and PVA. Scanning electron microscopy analysis of the plastics showed most explicit alterations on PCL surface. While the presence of C1 in the culture medium caused damage of the plastic surface, C2 interacted with it directly by forming a biofilm in surface breaks. Metagenomic analysis of C2, control and C2 with PCL revealed lower phylogenetic diversity in the presence of PCL and sharp rise of Gammaproteobacteria 16S rRNA sequences. The flourishing of the family Halomonadaceae was accompanied by a strong domination of the genus Halomonas, suggesting its active participation in PCL degradation. Thermophilic microorganisms in samples from Kamchatka hot springs were enriched in a medium with high- and low-density polyethylene in anaerobic conditions, at 78oC. Degradation of polyethylene after incubation was monitored by SEM. Results of 16S rRNA genes profiling compared with control variants revealed a domination of bacteria of phylum Dictyoglomi and family Thermoanaerobacteraceae in anaerobic thermophilic Kamchatka enrichments in the presence of polyethylene. These results indicate the possibility of thermophilic anaerobes to degrade the two types of polyethylene. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1Polymers may be converted into gaseous hydrocarbons by catalytic pyrolysis processes. • The use of REM as catalysts increases the yield of gaseous pyrolysis products. • During pyrolysis using lutetium, the composition of the products changes dramatically. This paper describes non-catalytic and catalytic pyrolysis of plastic waste materials. Four types of waste plastics were used in study: high density polyethylene (PE), low density polypropylene (PP), polyethylene terephthalate (PET). Plastic waste was decomposed into three fractions under pyrolysis conditions: gas, liquid and solid residual. The use of vanadates MeVO 4 and vanadites MeVO 3 of REM (Me=La, Gd, Lu) as catalysts let to change the yield of the gas fraction and change the composition of the gaseous pyrolysis products. Catalytic decomposition increased the amount of the gaseous products by 15–20 %, reduced the condensate, and changed their composition with regard to the non-catalytic process at the same pyrolysis temperature. The total number of reaction products was determined in each fraction. The quantitative analysis of the composition of the gas fraction was performed by gas-liquid chromatography. The study of non-catalytic pyrolysis of plastics and thermogravimetric analysis let to determine the most favorable temperature conditions for the implementation of the catalytic pyrolysis. The catalytic pyrolysis of plastics was carried out in order to obtain the maximum yield of valuable gaseous products. The synthesized vanadites and vanadates of REM were used as catalysts. When using catalysts based on lanthanum and gadolinium compounds, a regular change in the amount of gaseous substances was observed without significant changes in their composition. The use of lutetium vanadate and lutetium vanadite demonstrated a phenomenal result that is associated with the cardinal change of structure of degradation products of PET. The syngas was obtained instead of acetaldehyde. This result is related to the structure of the used catalyst. [ABSTRACT FROM AUTHOR]

When the finite element-strength reduction method is used for two-dimensional slope stability analysis for elastic-perfectly plastic material, the failure criterion usually adopts the criterion of plastic zone penetration. That is, when the slope is in the limit equilibrium state, the plastic zone goes through the slope from the toe to the top. Meanwhile, the critical slip surface is composed of a series of points of maximum equivalent plastic strain along the depth direction. By deploying a set of parallel lines approximately perpendicular to the slope surface and picking out the points of these lines with the maximum equivalent strain points, we obtain a series of points taking on a wave shape, which constitutes a signal function. Subsequently, the wavelet packet analysis is used to smooth these points, i.e., locating the critical slip surface. The analysis of classic examples and comparison with Spencer's method show that the proposed method in this paper is reasonable and effective. [ABSTRACT FROM AUTHOR]

Due to the special mechanical properties of macker rock, problems may be caused easily if the pressure of the surrounding rock calculated from the standard empirical equation is used in the structural design of tunnel support, such as obviously insufficient bearing capacity of the support structure, large deformation, and collapse. Taking the Jiangluling Macker Tunnel in Gonghe-Yushu Highway as an example, the distribution pattern of plastic zone of the surrounding rock and the calculation method and reasonable values of pressure of the surrounding rock are studied in this paper, by means of theoretical analysis, numerical computation, and field measurement data. The results show that the elastic-plastic analysis method is suitable for the pressure of the surrounding rock of macker tunnel. The influence radius of the plastic zone of the surrounding rock can be 32 m, and the lateral pressure of the surrounding rock of the tunnel is equivalent to the vertical pressure. In the absence of test conditions and measured data, the pressure of the surrounding rock can be approximately 0.83 MPa for the purpose of design of tunnel support structure. This conclusion provides technical support for projects in similar conditions. [ABSTRACT FROM AUTHOR]

This research aimed to develop a new digital evaluation protocol to objectively quantify the volumetric changes of root coverage periodontal plastic surgery when combined with connective tissue graft. Consecutive patients with Cairo recession type 1 (RT1) or Cairo recession type 2 (RT2) were treated. Accurate study models obtained at baseline and follow-ups were optically scanned. Healing dynamics were measured by calculating volume differences between time points. Nineteen patients were treated between December 2014 and January 2019. At 3-month follow-up, root coverage was 95.6% (± 14.5%) with tunnel and connective tissue graft (TUN + CTG) technique, and 88.9% (± 20.5%) with the vestibular incision subperiosteal tunnel access and connective tissue graft (VISTA + CTG) technique. Recession decreased 1.33 (± 0.86) mm and 1.42 (± 0.92) mm, respectively (p = 0.337). At 6-month follow-up, root coverage was 96.5% (± 10.4%) with the TUN + CTG and 93.9% (± 10.3%) with the VISTA + CTG. Recession decreased 1.35 (± 0.85) mm and 1.45 (± 0.82) mm, respectively (p = 0.455). Complete root coverage was achieved in 86.7% (± 0.4%) with TUN + CTG and 70.6% (± 0.5%) with VISTA + CTG. No statistically significant differences were found between techniques. The digital protocol presented proved to be a non-invasive technique for accurate measurements of clinical outcomes. Both techniques reduce gingival recessions, with no statistically significant differences. [ABSTRACT FROM AUTHOR]

• A novel method for the gear mesh stiffness calculation of plastic gear pair is established. • The influences of meshing deformation on the mesh behavior of plastic gear pair are investigated. • An iterative algorithm is utilized for the accurate calculation of gear mesh stiffness. • The proposed method is verified by the finite element method. The accurate calculation of the mesh stiffness for a plastic gear pair is significant for analyzing its transmission performance. During the meshing process, factors such as gear tooth meshing deformation and thermal effect will cause variations of the meshing position and tooth load particularly for plastic gears. These increase the difficulty for the accurate calculation of the gear mesh stiffness for plastic gear pair. To address this issue, the instantaneous gear tooth meshing deformation is obtained based on the potential energy method. Then, the effects of the above factors on the contact condition of a meshing tooth pair are analyzed, based on which the actual mesh position is accurately obtained via an iterative algorithm. Under the commonly-used elastic contact assumption, the contact stiffness at the new meshing position is calculated based on the Hertzian contact theory, and the algorithm of the mesh stiffness calculation for a plastic gear pair is derived by analyzing the influence of the elastic approach of meshing tooth on load distribution mechanism of gear pair. Compared with previous analytical methods, the proposed algorithm for mesh stiffness calculation shows higher accuracy, and it can also properly analyze the effect of load and other parameters on the mesh behavior of plastic gear pair, which can provide a theoretical basis for the performance analysis of plastic gear transmission system. [ABSTRACT FROM AUTHOR]

The constitutive model is the crucial part for the finite element analyses. To study the elasto-plastic properties of unbound granular materials (UGMs) under repeated vehicular loads, an elasto-plastic constitutive model called revised spatially mobilized plane (SMP) was proposed and validated. In this study, the revised SMP model was used for the plastic strain analyses of a typical three-layer pavement structure. To make comparisons, the Mohr-Coulomb and Druck-Prager models were employed for the numerical computation. The results show that plastic tensile and compressive strains in the horizontal and vertical directions appear on the top surface of UGM using the revised SMP model, but no plastic strains are produced by the Mohr-Coulomb and Druck-Prager models. The distribution of plastic strains in the revised SMP model had a good relationship with the actual loading areas under the vehicular loading, which related to the rutting. With the Mohr-Coulomb and Druck-Prage models, a great plastic strain was produced during the first several loading cycles and hardly increased in the following loading cycles, while the plastic strain in the revised SMP model presented an obvious increasing tendency with increased loading cycles. The predicted permanent deformations of the revised SMP, Mohr-Coulomb and Druck-Prage models were 0.557 mm, 0.78 mm and 0.155 mm, respectively. Our work reveals that the Mohr-Coulomb model may over-predict and Druck-Prage model may under-predict the rutting of pavement in early loading stage and the results proved that the revised SMP model had advantages in the description of the plastic strain of UMG under repeated loads. [ABSTRACT FROM AUTHOR]

The locked section is a kind of geological structure that is commonly found in natural slopes. The instability criterion of the slope with a locked section structure is not yet studied. In accordance with the mechanical properties of this type of slope, the rock mass is divided into several rock blocks along its joint distribution, and the upper limit method of plastic limit analysis is introduced. By combining the principle of virtual work and the characteristics of the slope, a virtual speed is assigned to the slope and the locked section. In addition, the maximum elastic strain energy that can be accumulated in the locked section is calculated to derive its deformation rate and internal energy dissipation power. The virtual velocity, internal energy dissipation power, and gravity work power of the locked section and the rock slope are solved simultaneously in accordance with the Mohr–Coulomb correlation flow law. Finally, the formula for calculating the safety factor of this type of slope under shear failure mode is derived. A slope in Xikou, Sichuan, China, is taken as an example to verify the proposed model. [ABSTRACT FROM AUTHOR]

Global structural analyses in civil engineering are usually performed considering linear‐elastic material behavior. However, for steel structures, a certain degree of plasticization depending on the member classification may be considered. Corresponding plastic analyses taking material nonlinearities into account are effectively realized using numerical methods. Frequently applied finite elements of two and three‐dimensional models evaluate the plasticity at defined nodes using a yield surface, i.e. by a yield condition, hardening rule, and flow rule. Corresponding calculations are connected to a large numerical as well as time‐consuming effort and they do not rely on the theoretical background of beam theory, to which the regulations of standards mainly correspond. For that reason, methods using beam elements (one‐dimensional) combined with cross‐sectional analyses are commonly applied for steel members in terms of plastic zones theories. In these approaches, plasticization is in general assessed by means of axial stress only. In this paper, more precise numerical representation of the combined stress states, i.e. axial and shear stresses, is presented and results of the proposed approach are validated and discussed. [ABSTRACT FROM AUTHOR]

The mechanical analysis and deformation mechanism of cap formation in orbital drilling process plays a vital role in revealing the changing law of hole-making quality at the exit machining stage. The characteristics of cap formation, generated by a dedicated cutting tool, is proposed that aimed at orbital drilling process. Especially, the cap bottom is simplified as a simply supported circular plate under a partially uniform load based on the symmetrical feature of the geometrical morphology and force condition. Its corresponding unified plastic limit analysis is developed. Then the ultimate load, stress field, and plastic deformation at the bottom of the cap are derived from the unified yield criterion. Furthermore, in terms of the Tresca yield, Huber–von Mises, and twin-shear yield criteria, the solutions are obtained by numerical calculation method and compared them with each other. Finally, conclusions were made about the cap formation mechanism in the orbital drilling of holes from the unified plastic limit analysis perspective. [ABSTRACT FROM AUTHOR]