Plastic Load Research Articles

Reliability based geometrically nonlinear bi-directional evolutionary structural optimization of elasto-plastic material

The aim of this paper is to integrate the reliability-based analysis into topology optimization problems. Consequently, reliability-based topology optimization (RBTO) of geometrically nonlinear elasto-plastic models is presented. For purpose of performing (RBTO), the volume fraction is considered reliable since that the application of (RBTO) gives different topology in comparison to the deterministic topology optimization. The effects of changing the prescribed total structural volume constraint for deterministic designs and changing the reliability index for probabilistic designs are considered. Reliability index works as a constraint which is related to reliability condition added into the volume fraction and it is calculated using the Monte-Carlo simulation approach in the case of probabilistic design. In addition, bi-directional evolutionary structural optimization (BESO) method is utilized to study the effect of geometrically nonlinear elasto-plastic design. The plastic behavior can be controlled by defining a limit on the plastic limit load multipliers. The suggested work's efficiency is demonstrated via a 2D benchmark problem. In case of elastic material, a 2D model of U-shape plate is used for probabilistic design of linear and geometrically nonlinear topology optimizations. Furthermore, a 2D elasto-plastic model is considered for reliability-based design to demonstrate that the suggested approach can determine the best topological solution.

Increase in Elastic Stress Limits by Plastic Conditioning: Influence of Strain Hardening on Interference Fits

This paper presents a novel method for the design of purely elastic interference fits by exploiting the plastic properties of a material. In this process, the elastic potential of the material is expanded by the targeted application of residual stresses and material strengthening, in such a way that additional operational loads due to rotating bending moments, torsion, temperature changes, and centrifugal forces are absorbed by the hub in a purely elastic manner, and plastic deformations are avoided. In the ideal case, the performance shown by the connection can be almost doubled compared to conventional elastically joined interference fits. Compared with conventional elastically–plastically joined interference fits, a specifically defined additional safety against plastic deformation can be guaranteed. In addition to the prerequisites of plasticity theory, the fundamental aspects of the process are presented and investigated on the basis of two-dimensional numerical calculation models. Both ideal plastic and hardening material models were used. The results of this work showed that previous stress limits can be significantly increased up to full plastic loading and that the utilization of plastic material properties is also made possible by plastic conditioning for applications that were previously designed to be purely elastic.

Prevalence of Covid-19 personal protective equipment in aquatic systems and impact on associated fauna.

The use and undesignated disposal of COVID-19 related personal protective equipments (PPEs) has resulted in a spike in the global mismanagement of plastic waste. Moreover, the SARS-CoV-2 pandemic has not only affected the socio-economic state of the world but is contributing significantly to the already existing aquatic pollution dilemma. Consequently, PPE litter is an emerging pollutant in aquatic ecosystems that warrants significant attention. This review endeavoured to present a synopsis of the global mismanagement of PPE waste and highlight the devastating ramifications of the ensuing environment. The paper reveals that PPE litter is indeed negatively impacting environmental systems on varying levels around the globe. Furthermore, peak plastic loads are transported by Asian rivers and are deposited into the Pacific and Indian Oceans. Beaches and seabed are the major sinks of COVID-19 PPE litter making benthic organisms to be the most vulnerable. More studies need to be undertaken to monitor aquatic resources to get a detailed overview of COVID-19 PPE litter in the environment.

Study on axial compression bearing capacity of novel concrete-filled square steel tube columns

The way that strengthening the bond effect between the concrete and the inner steel by welding technology can effectively improve the axial bearing performance of the concrete-filled square steel tube (CFSST) column. However, this method requires high welding quality. In order to simplify the construction and reduce the difficulty of construction, two kinds of novel section forms of CFSST column without welding have been proposed. One is CFSST column reinforced with rhombic stirrups (specimens in SSSC group), the other is double-skin CFSST column (rhombic inside & square outside) (specimens in SSC group). A total of 21 specimens were fabricated for axial compression test, including 10 specimens in SSSC group, 7 specimens in SSC group, 1 CFSST column reinforced with inclined I-steel, 1 CFSST column reinforced with I-steel, 1 CFSST column reinforced with circle steel tube, and 1 CFSST column. The axial load-displacement curves of the specimens were obtained, and the failure modes and the influence parameters of specimens with different sections were analyzed and compared. The results show that the failure modes can be divided into local buckling failure and instability failure during plastic loading according to the aspect ratio. The specimens in SSC group have the highest average peak load, and the best residual bearing capacity, and the most eximious plastic strengthening characteristics in the later stage than other specimens. The decreasing rate of unit peak load of SSSC group was the slowest when the steel content was increased, which improves the bearing capacity overall. Increasing the core concrete area (inner steel tube side length) can enhance the bearing capacity of the specimens with longitudinally continuous build-in steel (reinforced with steel tube). While, it is not economical to improve the peak load of the specimens with large section (side length >200 mm) by increasing the thickness of the outer steel tube when the build-in steel is longitudinally discontinuous (reinforced with rhombic stirrups). Based on the result analyses, the calculation formulas considering the stability of axial compressive bearing capacity of specimens in SSSC and SSC group have been derived by superposition method. And the calculated results are in good agreement with the test results.

Split stress rate plasticity formulation

A novel general constitutive formulation framework of rate independent plasticity is presented where the stress rate tensor is split in two components, and plastic loading is affected separately by each one of these two components in relation to a common loading direction normal to a single smooth yield surface in stress space. This split-stress rate separate effect provides greater flexibility for simulating the material response under combined stress rate components loading. The difficulty arises when loading and unloading events may occur interchangeably between the two stress rate components and special attention is required to avoid irrational results and guarantee continuity of response upon rotation of the total stress rate direction at a loading stress point. The formulation can acquire two different analytical schemes, one more complicated but incrementally linear, while the other is simpler but incrementally nonlinear. The key constitutive ingredient of split stress rate definition is a multifaceted choice, and three options are presented. One option which is of particular interest to granular mechanics, splits the stress rate into a component that changes the stress principal values at fixed principal axes, while the other component does exactly the opposite, i.e., rotates the stress principal axes at fixed principal values. For this option various constitutive ingredients and new concepts are introduced and extensively elaborated, with emphasis on dilatancy, understanding that these elaborations are of an exploratory nature intending to prompt further research along the proposed guidelines.

Riverine litter in a small urban river in Marseille, France: Plastic load and management challenges

Small urban rivers are thought to be major sources of riverine litter, especially macroplastics, into the ocean. In well-developed countries, waste management infrastructures and recovery systems are sometimes implemented to prevent their emission into the sea meeting environmental and economic goals. The Huveaune River in Marseille, South of France, is a typical case study showing a non-negligible and uncontrolled leakage of riverine litter remains, despite all recovery systems implemented. Giant bar screens are settled over the river to collect riverine litter from the whole water column before water is released into the Sea. In this paper, screened material was characterized during a dry, wet and heavy rainfall period and annual macroplastic mass flows were estimated. The plastic fraction represented 83% by count of the 3147 items sorted and counted. Mass flow of plastic debris ranged between 1.1 and 5.8 mt/yr (equivalent to 2.1–11.4 g/cap/yr), in which 0.4–2.1 mt/yr (equivalent to 0.8–4.1 g/cap/yr) are bypassed to the sea during heavy rainfall periods. Giant bar screens across the Huveaune River prevent 65% of the mass flow to reach the sea annually, but 35% remain uncontrolled. When compared to the Seine River and other European Rivers, macroplastic leakage into the ocean per capita may range between 1 and 10 g/cap/yr. This suggests that end-of-pipe solutions are not enough and further supports urgent regulations of the plastic production on local to global scales to tackle the plastic pollution at its source.

Hazardous contaminants in plastics contained in compost and agricultural soil

Macro-, meso- and microplastic (MAP, MEP, MP) occurrence in compost is an environmental issue whose extent and effects are not yet understood. Here, we studied the occurrence of MAPs, MEPs and MPs in compost samples, and the transfer of hazardous contaminants from plastics to compost and soil. MAPs/MEPs and MPs concentrations in compost were 6.5 g/kg and 6.6 ± 1.5 pieces/kg; from common recommendations for compost application, we estimated ∼4–23 × 107 pieces MPs and 4–29 × 104 g MAPs/MEPs ha−1 per year ending into agricultural soils fertilized with such compost. Regarding contaminants, bis(ethylhexyl) phthalate, acetyl tributyl citrate, dodecane and nonanal were extracted in higher concentrations from plastics and plastic-contaminated compost than from compost where MAPs/MEPs had been removed prior to extraction and analysis. However, some contaminants were present even after MAPs/MEPs removal, ascribable to short- and long-term release by MAPs/MEPs, and to the presence of MPs. DEHP concentration was higher in soils where compost was applied than in fields where it was not used. These results, along with estimations of plastic load to soil from the use of compost, show that compost application is a source of plastic pollution into agricultural fields, and that plastic might transfer hazardous contaminants to soil.

Birds of a feather eat plastic together: high levels of plastic ingestion in Great Shearwater adults and juveniles across their annual migratory cycle.

Limited work to date has examined plastic ingestion in highly migratory seabirds like Great Shearwaters (Ardenna gravis) across the their entire migratory range, although this species is prone to ingest plastic as a wide-ranging procellariiform. We examined 217 Great Shearwaters obtained from 2008-2019 at multiple locations spanning their yearly migration cycle across the Northwest and South Atlantic to assess accumulation of ingested plastic as well as trends over time and between locations. A total of 2,328 plastic fragments were documented in the ventriculus portion of the gastrointestinal tract, with an average of 9 plastic fragments per bird. The mass, count, and frequency of plastic occurrence (FO) varied by location, with higher plastic burdens but lower FO in South Atlantic individuals from the breeding colonies. No fragments of the same size or morphology were found in the primary forage fish prey, the sand lance, (Ammodytes spp., n = 202) that supports Great Shearwaters in Massachusetts Bay, USA, suggesting the birds directly ingest the bulk of their plastic loads rather than accumulating via trophic transfer. Fourier-transform infrared spectroscopy indicated that low- and high-density polyethylene were the most common polymers ingested, within all years and locations. Individuals from the South Atlantic contained a higher proportion of larger plastic items and fragments compared to juveniles and non-breeding adults from the NW Atlantic, possibly due to increased use of remote, pelagic areas subject to reduced inputs of smaller, more diverse, and potentially less buoyant plastics found adjacent to coastal margins. Different signatures of polymer type, size, and category between similar life stages at different locations suggests rapid turnover of ingested plastics commensurate with migratory stage and location, though more empirical evidence is needed to ground-truth this hypothesis. This work is the first to comprehensively measure the accumulation of ingested plastics by Great Shearwaters over the last decade and across multiple locations spanning their yearly trans-equatorial migration cycle, and underscores their utility as sentinels of plastic pollution in Atlantic ecosystems.

C Reep Aging Behavior of Al-Cu-Mg-Si Alloy With Elastic and Plastic Loads

C Reep Aging Behavior of Al-Cu-Mg-Si Alloy With Elastic and Plastic Loads

An Integrative Assessment of the Plastic Debris Load in the Mediterranean Sea

An Integrative Assessment of the Plastic Debris Load in the Mediterranean Sea

Index models for ecological and health risks assessment of environmental micro-and nano-sized plastics

<abstract> <p>The definition of environmental indexes is one of the most widely used methods and methodologies for the study of exposure to polluting agents, and it is a highly helpful instrument for describing the quality of the environment in a simple and straightforward manner. In this study, index models were presented and described that can be used in evaluating the contamination, pollution and health risks of environmental micro (MPs) and nanoplastics (NPs) to ecosystems and humans. Index models such as plastic contamination factors (pCf) and pollution load index (pPLI), plastic- bioconcentration or accumulation factors (pBCf or pBAf), plastic-biota-sediment accumulation factor (pBSAf), biota accumulation load index (BALI), polymer risks indices (pRi), polymer ecological risks index (pERI) while plastic estimated daily intake (pEDI) and plastic carcinogenic risks (pCR) were described for oral, dermal and inhalation pathways. All index modeled were further described based on polymer types of MPs/NPs. The final value is represented by a quantity that measures a weighted combination of sub-indices and defined by an appropriate mathematical function. The central concept is to present an indicator that can describe, in a clear and concise manner, the level of MPs/NPs in the environment, thereby indicating where it would be necessary to intervene and where it would not in order to improve overall environmental conditions.</p> </abstract>

Nonlinear elastic plastic load deflection curves in NiTi shape memory alloy helical coils

Reversible deflection of coil spring due to shape memory effect was examined. Coil springs were prepared by winding the wire of Nickel -50.at.% Titanium alloy followed by the annealing at 800 C for 1h to set the coil shape. The Mf and Af temperatures were 30 C and 87 C and the spring was deformed in the fully martensite state at room temperature. A tough pitched spring with the coil diameter of 6.6 mm and the element diameter of 0.6 mm showed shape memory effect after extension larger than 1,000 %. The load-deflection curves measured showed nonlinear relationship with rapid increase of load at a certain extension. It was found that the shape memory strain of coil spring is not limited by that of element wire but by the geometry of coil spring against the extension. Noted that and the deflection was accompanied with the rotation around the coil axis. Elastic plastic deflection analysis was performed, and the prediction of the theory was compared with the experimental curves.

Method of theoretically calculating spherical stress wave field in linear-hardening materials under impact load

Based on the linear hardening plastic constitutive model, the theoretical solution of the elastic-plastic spherical stress wave field under impact load is established. Firstly, the influence of the impact load unloading rate on the propagation of the spherical stress wave is analyzed, and three different types of propagation images are obtained. On this basis, the method of theoretically calculating the spherical wave equation in elastic stage, plastic loading stage and unloading stage is established separately, and the calculation scheme of particle displacement, particle velocity, stress and strain is given. Compared with the existing theoretical methods, this method takes into account the different propagation patterns of the stress waves under different unloading rates, and shows how to calculate the stress wave parameters in unloading stage, which is more applicable. This method is used to calculate the elastic-plastic spherical stress wave field under constant shock load and exponential attenuation shock load. The calculated results are in good agreement with those from the existing theoretical method and numerical simulation results in the elastic stage and also in the plastic loading stage. In the unloading stage, the existing theoretical method is no longer applicable, while the results obtained in this paper are in good agreement with the numerical simulation results, which verifies the correctness of the theoretical method.

Plastic Loading Induced High Strength-Ductility for Creep Aged Al-Cu-Li Alloys

Plastic Loading Induced High Strength-Ductility for Creep Aged Al-Cu-Li Alloys

Micromechanical elastoplastic limit analysis of in-plane bending of Functionally Graded Pipe elbows

Pipe elbows, also known as pipe bends, are important components of a piping system. These curved elements are very flexible when compared to their straight counterparts, and are often responsible for reducing the reaction forces and moments within the piping system. However, due to large deformations, the elbows are more likely to exceed their stress limits. The effect of in-plane bending on plastic limit loads of Functionally Graded (FG) pipe bends is presented using three-dimensional non-linear finite element analysis and a micromechanical constitutive model. The effective properties of the material are estimated by the Mori–Tanaka homogenization scheme and the TTO plasticity model. The analysis was carried out for different loading cases, geometries and volume fraction distribution. The results showed that an FG elbow has a very distinct behavior comparatively to a similar homogeneous elbow made out of metal, specially in terms of limit moments and stress distribution. Finally, an analytical model to estimate the limit moment of FG elbows is presented.

H2-enriched gaseous fuel production via co-gasification of an algae-plastic waste mixture using Aspen PLUS

Thermo-chemical conversion of biomass is a promising technological alternative for producing renewable fuel and reducing waste disposal. This simulation study includes the first attempt to perform co-gasification of algae-plastic waste for H2-enriched gaseous fuel production. An Aspen Plus-based simulation model was developed to evaluate the influence of gasifier temperature and equivalence ratio on the syngas composition, heating value, and carbon conversion efficiency. Simulation results indicated that the rise in gasifier temperature favoured the H2 and CO formation, and further, plastic loading enhanced H2 production to a greater extent. It was observed that the product (H2 and CO) yield decreased significantly with the rise of the equivalence ratio. At the same time, CO2 formation increased due to more carbon conversion after enhancing O2 content in the gasifier. It was also noticed that the synergy of biomass and plastic waste significantly enhanced H2 content and improved heating value, leading to a produced energy-efficient gaseous product. It is inferred that H2-enriched feedstock acts as an H2 donor to the H2 deficient biomass. Based on the findings, consistency in the simulation results was observed compared with the previous literature. Hence, a mixture of biomass and plastic waste favours obtaining an energy-efficient renewable fuel that could be utilized for different applications.

Optimization of compounding formulation for the development of high-preformance coating material using waste tire powder for gasket application

Nitrile butadiene rubber latex (NBRL) based gasket materials were extensively used in the past due to their excellent oil resistance, good abrasion resistance, and shock absorption as well as good high-temperature stability. Recently, carbon black has been introduced to further improve the oil absorption properties and thermal performance of the gasket materials which increased the total costing and makes the processing difficult due to the agglomeration of carbon black in NBRL. Thus, in this research, waste tire powder (WTP) was introduced to develop high-performance coating materials as an alternative to carbon black in NBRL gasket material. Optimization of new compounding formulation has been carried out by manipulating the WTP loading and hybrid WTP-carbon black filler loading. The filler loading was selected based on the desired surface texture and coating thickness. The experience was also carried out by varying the WTP, Sulphur, and plasticizer loading. The desired surface texture and thickness of coating materials were developed at WTP loading of 80phr and 90phr. Whereas, the optimum Sulphur loading was achieved at 1phr - 2phr, and plasticizer loading of 10phr and 15phr. From the experiments carried out, the optimum loading of WTP was 90phr which gives a fully contained gasket composite. Furthermore, DOP optimum loading is 15phr which gives a smooth surface appearance. Lastly, Sulphur with 1phr gives a more even surface texture as compared to 2phr loading.

A finite element-based analysis approach for computing the remaining strength of the pressure equipment with a local thin area defect

Upon facing a pressure equipment with a structure defect and the subsequent question as to if the equipment is qualified for continuous operation, the answer often resorts to enough strength. However, strength of a pressure equipment is never defined clearly. In API 579, in order for a pressure equipment with a local thin area (LTA) defect to be accepted for continuing use in operation, the remaining strength factor (RSF) of the equipment must exceed 0.9. RSF is defined as the ratio of the plastic collapse load (PCL) of equipment with defect to that of the equipment without any damage. Hence, accurate evaluation of the plastic collapse load is of utter importance to judge fitness of the equipment. In this research, a finite element (FEM) based methodology has been devised to obtain an accurate estimation of the plastic collapse load.What needs to be established first is a finite element model for the whole, undamaged vessel as the main model and the other is the surrounding region encompassing the LTA defect as the sub-model. Pressure loadings are incrementally and continuously applied to the main model through load steps until the model can no longer sustain, and the plastic collapse load is the maximum load that a structure can safely carry. The cut boundary data from the main model is then passed on to the sub-model, and calculation is resumed with the same load steps until the PCL of the LTA is obtained. Then RSF is determined as the PCL of the vessel with an LTA to that of the original, damage free vessel.API 579 and ASME FFS propose the use of RSF as an indicator for assessing fitness of an equipment. Concept-wise, the term RSF is not sophisticated and sometimes is treated as rough guidance for assessing the remaining strength of a structure. However, the same concept must be treated differently as it is applied to determine whether the defect is allowed and the remaining life is needed, which ought to be a finite element-based approach. In this research, it is achieved through:1. Representing the defect in the form of a submodel consisting of SOLIDS element in order to process the area of varied thicknesses, and.2. Computing the plastic collapse load for both the undamaged finite element model of SHELL elements and the submodel of SOLIDS elements simultaneously.

Distributed fiber optic strain sensing of bending deformation of a well mockup in the laboratory

Well integrity is critical to the safety and success of subsurface energy exploration and management, as leakage of fluids from subsurface reservoirs is often induced by compromised wells. This study investigates bending deformation of a mockup of an oil/gas well that is subjected to loads expected in deviated wells under reservoir compaction and assesses the feasibility of utilizing distributed fiber optic strain sensing to monitor the deformation. A well mockup, which consists of outer and inner steel pipes with a cemented annulus, is tested under three-point bending loading and its strain and curvature development is monitored by Brillouin optical time domain reflectometry/analysis (BOTDR/A) as well as optical frequency domain reflectometry (OFDR). The primary objective of this research is to assess the strain sensing performance of newly fabricated fiber optic cables and to identify key cable characteristics which could improve the quality of distributed strain measurements with BOTDR/A. Results show that the tight-buffered cable is best suited for strain sensing as its maximum errors in the strain measurement were −36% and −24% against conventional sensors at the maximum elastic and plastic bending loads, respectively, whereas those of the non-tight-buffered cable were −45% and −71%, respectively. Similar trends were obtained in the bending curvature measurement. The detailed design of the tight-buffered cable is presented to elucidate key characteristics of such a cable, which will facilitate accurate distributed strain sensing in oil and gas wells.

Extended sequential limit analysis: Addressing large deflections and shape changes in strain hardening circular membranes with a moving coordinate system

The sequential limit analysis (SLA) approach can trace load–deflection response and the corresponding plastic limit load of the structures accurately and efficiently. However, this method is limited to the structures without large shape changes in the plane stress directions. In this study, an extended SLA established on moving coordinates is proposed to investigate its further extension for strain-hardening circular membranes with large deflections and shape change behaviors. This new method features dividing entire analysis into sequential optimization problems based on moving coordinate systems to deal with the shape change in plane stress direction for the strain-hardening circular membranes subjected to large deflections. The corresponding adaptive geometry update strategy is also presented. Moreover, the elastic–plastic incremental simulations are conducted for the purpose to validate the correctness and feasibility of the simplifications during model construction and the analysis accuracy of this newly proposed method. From the contrastive results between the extended SLA and ABAQUS simulation, the accuracy of this new approach is confirmed. Furthermore, from the parametric analysis results, the fact can be concluded that the accuracy of SLA for load estimation will be improved with the increase of material Young’s modulus, and reduces with the increase of the initial yield strength and the hardening exponent and hardening coefficient. The accuracy of this method is more sensitive towards hardening exponent and initial yield strength while it is less sensitive towards hardening coefficient. In addition, this extended SLA method with the assumptions of zero bending moment can tolerate a high range variation of thickness–radius ratio, particularly in materials with higher Young’s modulus. These characteristics enables this method be adopted in wild practical application fields as a feasible tool to design the membrane structures initially and determine the structure safety factors preliminarily.