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As the normality concept for frictional dilatant material has a serious drawback, the key feature in this numerical study is that the material here is characterized by elastic-viscoplastic constitutive relation with plastic non-normality effect for two different hardness functions. The paper aims to discuss this issue.

Quasi-static, mode I plane strain crack tip fields have been investigated for a plastically compressible isotropic hardening–softening–hardening material under small-scale yielding conditions. Finite deformation, finite element calculations are carried out in front of the crack with a blunt notch. For comparison purpose a few results of a hardening material are also provided.

The present numerical calculations show that crack tip deformation and the field quantities near the tip significantly depend on the combination of plastic compressibility and slope of the hardness function. Furthermore, the consideration of plastic non-normality flow rule makes the crack tip deformation as well as the field quantities significantly different as compared to those results when the constitutive equation exhibits plastic normality.

To the best of the authors’ knowledge, analyses, related to the constitutive relation exhibiting plastic non-normality in the context of plastic compressibility and softening (or softening hardening) on the near tip fields, are not explored in the literature.

This research studies a plastic recycling system from a reverse logistics angle and investigates the potential benefits of a multimodality strategy to the network design of plastic recycling. This research aims to quantify the impact of multimodality on the network, to provide decision support for the design of more sustainable plastic recycling networks in the future.

A MILP model is developed to assess different plastic waste collection, treatment and transportation scenarios. Comprehensive costs of the network are considered, including emission costs. A baseline scenario represents the optimized current situation while other scenarios allow multimodality options (barge and train) to be applied.

Results show that transportation cost contributes to about 7 percent of the total cost and multimodality can bring a reduction of almost 20 percent in transportation costs (CO₂‐eq emissions included). In our illustrative case with two plastic separation methods, the post‐separation channel benefits more from a multimodality strategy than the source‐separation channel. This relates to the locations and availability of intermediate facilities and the quantity of waste transported on each route.

This study applies a reverse logistics network model to design a plastic recycling network with special structures and incorporates a multimodality strategy to improve sustainability. Emission costs (carbon emission equivalents times carbon tax) are added to the total cost of the network to be optimized.

An important characteristic of many soil models is a volume change during plastic flow. In computations, this plastic volume change is expressed via a kinematic constraint on the possible deformations. Due to this constraint the plane‐strain three‐noded triangular element exhibits locking when plastic deformations occur, under dilatant, contractant and isochoric conditions. It is demonstrated that using the method of enhanced assumed strains by Simol this locking cannot be remedied. For six‐noded wedges and four‐noded and five‐noded pyramids the same conclusion is obtained.

In the framework of the finite element method, the problem of elasto‐plastic consolidation gives rise to a system of non‐linear, coupled residual equations which satisfy the conditions of balance of momentum and balance of mass. In determining the roots of these equations it is necessary that the coupled equations be linearized. To this end, the concept of ‘consistent linearization’ proposed by Simo and Taylor for a single‐phase system is applied to the two‐phase soil‐water system. The roots of the coupled residual equations are solved iteratively by employing Newton's method. It is shown that in non‐linear consolidation analyses, the use of a tangent coefficient matrix derived consistently from the integrated constitutive equation defining the characteristics of the solid skeletal phase results in an iterative solution scheme which preserves the asymptotic rate of quadratic convergence of Newton's method. Numerical examples involving combined radial and vertical flows through an elasto‐plastic soil medium are presented to demonstrate the computational superiority of the above technique over the method based on standard ‘elasto‐plastic continuum formulations’ adopted in most finite element codes.

The use of pneumatic conveying of solid bulk over long distance has become a popular technique due to low operational cost, low maintenance requirement, layout flexibility and ease of automation. The purpose of this paper is to identifity the flow regime in a pneumatic conveyor system by electrodynamic sensor placed around the pipe using fuzzy logic tools.

Electrical charge tomography is used to detect the existence of inherent charge on the moving particles through the pipe. Linear back projection algorithm and filtered back projection algorithm are employed to produce tomography image. Baffles of different shapes are inserted to create various flow regimes, such as full flow, three quarter flow, half flow and quarter flow. Fuzzy logic tools are used to identify different flow regimes and produce filtered back concentration profiles for each flow regime.

The results show significant improvement in the pipe flow image resolution and measurement.

This paper presents a flow identifier method using electrical charge tomography and fuzzy logic to monitor solid particles flow in pipeline.

The purpose of this paper is to establish a new dynamic coupled discrete-element contact model used for investigating fresh concrete with different grades and different motion states, and demonstrate its correctness and reliability according to the rheological property results of flow fresh concrete in different working states through simulating the slump process and mixing process.

To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength. The fluid-like fresh concrete is modelled as a two-phase fluid consisting of mortar and aggregate. Depending on the contact forms of the aggregate and mortar, the model is of one of the five types, namely, Hertz–Mindlin, pendular LB contact, funicular mucous contact, capillary LB contact or slurry lift/drag contact.

To verify the accuracy of this contact model, concrete slump and cross-vane rheometer tests are simulated using the traditional LB model and dynamic coupled contact model, for five concrete strengths. Finally, by comparing the simulation results from the two different contact models with experimental data, it is found that those from the proposed contact model are closer to the experimental data.

This contact model could be used to address issues such as (a) the mixing, transportation and pumping of fresh concrete, (b) deeper research and discussion on the influence of fresh concrete on the dynamic performance of agitated-transport vehicles, (c) the behaviour of fresh concrete in mixing tanks and (d) the abrasion of concrete pumping pipes.

To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength.

In 2017, global plastic production reached 348 million tonnes. Despite growing concerns about the environmental challenges associated with both plastic production and plastic waste, recent estimates suggest that plastic production and subsequent waste is expected to double by the year 2035 (European Commission, 2018). To help reduce the amount of plastic waste that litters the oceans and damages the environment, the European Union has recently commissioned a study about the feasibility of levying a tax on plastic products (New Economic Foundation for the Rethink Plastic Alliance, 2018). However, very few academic articles currently exist that critically examine the arguments for or against a plastic tax and thereby enlighten government and regulators on the subject. This chapter investigates whether plastic taxes can be used as an economic disincentive for plastic products and explores its advantages and disadvantages within a circular economy. It explores whether a plastic tax is the right economic instrument to limit the use of plastics, generate design and technical innovations for bio-based materials and degradable/recyclable plastics, create other economic incentives to optimize the value of plastic and its waste collection, and increase public awareness and responsibility. We find that a plastic tax may be a suitable solution as it is likely to influence the design, production, consumption, and waste sectors if designed properly. Yet, the tax should be carefully implemented and combined with other instruments to obtain the desired outcomes and reduce the occurrence of unfavorable side effects.

This paper aims to investigate how the user-controlled parameters of the fused filament fabrication three-dimensional printing process define temperature conditions on the boundary between layers of the part being fabricated and how these conditions influence the structure and strength of the polylactic acid part.

Fracture load in a three-point bending test and calculated related stress were used as a measure. The samples were printed with the long side along the z-axis, thus, in the bend tests, the maximum stress occurred orthogonally to the layers. Temperature distribution on the sample surface during printing was monitored with a thermal imager. Sample mesostructure was analyzed using scanning electron microscopy. The influence of the extrusion temperature, the intensity of part cooling, the printing speed and the time between printing individual layers were considered.

It is shown that the optimization of the process parameters responsible for temperature conditions makes it possible to approximate the strength of the interlayer cohesion to the bulk material strength.

The novelty of the study consists in the generalization of the outcomes. All the parameters varied can be expressed through two factors, namely, the temperature of the previous layer and the extrusion efficiency, determining the ratio of the amount of extruded plastic to the calculated. A regression model was proposed that describes the effect of the two factors on the printed part strength. Along with interlayer bonding strength, these two factors determine the formation of the part mesostructure (the geometry of the boundaries between individual threads).

This paper presents the results of the simulation of the forging of a connecting rod. The calculation has been carried out by the code FORGE3 developed at the CEMEF laboratory. FORGE3 is a three‐dimensional finite element computer program that can simulate hot forging of industrial parts. The flow problem is solved using a thermomechanical analysis. The mechanical resolution and the thermal one are coupled by the way of the consistency K which is thermodependent, the plastic deformation in the volume of the material and the friction heat flux on the surface. The material behaviour is assumed to be incompressible and viscoplastic (Norton—Hoff law) with the associated friction law. The thermal resolution includes the case of non‐linear physical properties and boundary conditions. An explicit Euler scheme is used for the mechanical resolution and two‐step schemes for the thermal one. For the computation of other parameters, it is necessary to have a good approximation for the strain rate tensor. The Orkisz method has been used to determine the deviatoric stress tensor and p is calculated by an original smoothing method. The results show that it is possible to get good information on the flow and on the physical properties during forging of automotive parts. Comparisons have been made with experimental measurements with a reasonably good agreement.

This paper aims to summarize the influence law of hybrid deposited and micro-rolling (HDMR) technology on the shaping strain and residual stress. And the rolling parameters combination was further optimized to guide the actual production.

This paper proposed a three-dimensional coupled thermo-mechanical model of the HDMR process. The validated model is used to investigate the influences of rolling parameters on stress and plastic strain (the distance between the energy source and roller [D_e–r], the rolling compression [c_r] and the friction coefficient [f_r]). The orthogonal optimization of three factors and three levels was carried out. The influence of rolling parameters on the plastic strain and residual stress is analyzed.

The simulation results show that HDMR technology can effectively increase the shaping strain of the weld bead and reduce the residual tensile stress on the weld bead surface. Furthermore, the influence of rolling parameters on stress and strain is obtained by orthogonal analysis, and the corresponding optimal combination is proposed. Also, the rolling temperature significantly affects the residual stress, and the rolling reduction has a substantial effect on the plastic deformation.

Owing to the choice of research methods, this paper failed to study microstructure evolution.

This paper provides a reference principle for the optimal selection of rolling parameters in HDMR.