Showing papers on "Material flow published in 2023"

Assessing the Sorting Efficiency of Plastic Packaging Waste in an Italian Material Recovery Facility: Current and Upgraded Configuration

Abstract: The first step in reintroducing plastic waste into the recycling cycle is to use material recovery facilities (MRFs). However, while the composition and types of plastic waste are changing over time, the layout of MRFs does not always adapt to this change. In this paper, an existing MRF in Southern Italy was chosen as a reference to evaluate its current performance and to estimate possible improvements in sorting through a specific upgrade. First, an analysis of the amount, composition, and sources (in terms of type of waste and distance from the MRF) of the input waste was conducted. The composition of the input waste was then compared with the amount of selected output waste streams in order to calculate the current sorting efficiency of each stream and compare it with the values obtained from the upgrade. Lastly, the current performance of the plant was compared with a previous assessment of the same MRF in order to highlight possible variation. Results showed how the incoming waste was mainly composed of packaging plastic waste, and that some plastic waste not yet selected by the plant ended up in specific output streams. Therefore, the current performance of the MRF resulted high for PET and PE bottles (80.2% and 92.8%, respectively), in contrast to mixed or flexible packaging, where the efficiency achieved lower values (55–50%). These values were caused by a weakness in the 2D flow sorting line, which the upgrade mostly addressed. The upgraded configuration increased the production of recyclable waste from 34.32% to 50.39%, especially due to the recovery of small flexible packaging films in PE and biopolymers.

A review of methods to trace material flows into final products in dynamic material flow analysis: From industry shipments in physical units to monetary input–output tables, Part 1

Abstract: Dynamic material flow analysis (dMFA) is widely used to model stock‐flow dynamics. To appropriately represent material lifetimes, recycling potentials, and service provision, dMFA requires data about the allocation of economy‐wide material consumption to different end‐use products or sectors, that is, the different product stocks, in which material consumption accumulates. Previous estimates of this allocation only cover few years, countries, and product groups. Recently, several new methods for estimating end‐use product allocation in dMFA were proposed, which so far lack systematic comparison. We review and systematize five methods for tracing material consumption into end‐use products in inflow‐driven dMFA and discuss their strengths and limitations. Widely used data on industry shipments in physical units have low spatio‐temporal coverage, which limits their applicability across countries and years. Monetary input–output tables (MIOTs) are widely available and their economy‐wide coverage makes them a valuable source to approximate material end‐uses. We find four distinct MIOT‐based methods: consumption‐based, waste input–output MFA (WIO‐MFA), Ghosh absorbing Markov chain, and partial Ghosh. We show that when applied to a given MIOT, the methods’ underlying input–output models yield the same results, with the exception of the partial Ghosh method, which involves simplifications. For practical applications, the MIOT system boundary must be aligned to those of dMFA, which involves the removal of service flows, sector (dis)aggregation, and re‐defining specific intermediate outputs as final demand. Theoretically, WIO‐MFA, applied to a modified MIOT, produces the most accurate results as it excludes massless and waste transactions. In part 2 of this work, we compare methods empirically and suggest improvements for aligning MIOT‐dMFA system boundaries.

In-depth understanding of rotating toolhead-induced heat generation and material flow behavior in friction-rolling additive manufacturing

Abstract: Friction-rolling additive manufacturing (FRAM) is an innovative solid-state additive manufacturing method for “non-weldable” alloys. The basic physics of this method relies on a rotating toolhead to generate severe plastic deformation and thereby deposit the material. However, the specific processes of heat generation and material flow behaviors induced by the rotating toolhead are not fully understood. In this study, a novel three-dimensional thermomechanically coupled Eulerian–Lagrangian model with a particle tracing technique was developed to analyze the transient temperature evolution and material flow behaviors during FRAM. The numerical simulation was validated based on experimental temperature measurements and the geometry of the deposit. The heat-generation process and gradual stabilization of the temperature field during the three stages of FRAM––namely, toolhead insertion, material feeding, and toolhead advancement––were successfully characterized. The results show that the toolhead simultaneously generates heat in the material strip and substrate, and more heat is generated in the shoulder and the transition zone where the toolhead shape changes from concave to convex. The presence of a single shoulder leads to an asymmetrical temperature distribution along the axial direction (Y direction) of the toolhead. The material near the toolhead flows tangentially around the toolhead, and the flow of the strip is better than that of the substrate. The particle tracing results show that the strip and substrate surfaces are well-mixed in the Z direction under the rotating action of the toolhead. The findings from this study can be applied in further fundamental investigations of the FRAM process and toolhead morphology design.

A review of methods to trace material flows into final products in dynamic material flow analysis: Comparative application of six methods to the United States and EXIOBASE3 regions, Part 2

Abstract: Modeling pathways toward sustainable production and consumption requires improved spatio‐temporal and material coverage of end‐use product stocks. Momentarily, studies on inflow‐driven, dynamic material flow analysis (dMFA) extrapolate scarce information on material end‐use shares (i.e., ratios that split economy‐wide material consumption to different end‐use products) for single countries and years across longer time periods and global regions. Therefore, in part 1 of this work, we reviewed five methods to derive material end‐use shares which use industry shipment data in physical units and monetary input–output tables (MIOTs). Herein, we comparatively apply these methods to the United States, drawing on detailed national data, as well as the multi‐regional input–output model EXIOBASE3. To better match MIOT and dMFA system definitions, we propose the end‐use transfer method, which re‐routes specific intermediate outputs to final demand in MIOTs. In closing, we conclude on 12 points for improved end‐use shares. We find mixed results regarding the fit between end‐use shares derived from industry shipments and MIOTs: for detailed national data, we find good fit for some materials (e.g., aluminum), while others deviate strongly (e.g., steel). In many cases, the temporal trend of MIOT‐derived end‐use shares roughly agrees with industry shipments. For EXIOBASE3, we find good fit for some countries and materials, but substantial mismatches for others. Despite mixed results, combining MIOT‐based end‐use shares with industry shipments and auxiliary country‐level data could enable improved temporal, geographical, and end‐use resolution. However, the scarcity, documentation, and quality of input data are key limitations for more accurate and detailed end‐use shares. This article met the requirements for a gold‐gold data openness badge described at http://jie.click/badges.

A Novel Lap-Butt Joint Design for FSW of Aluminum to Steel in Tee-Configuration: Joining Mechanism, Intermetallic Formation, and Fracture Behavior

Abstract: The development of new joint configurations suitable for dissimilar materials enables a wider range of applications and allows for an accelerated replacement of traditional structural construction materials by lightweight materials. The T-configuration is a joint configuration that has not been sufficiently studied for use with dissimilar materials, especially when created using the friction stir welding (FSW) process. In this study, a combined lap/butt design was introduced and implemented, seeking to create a T-joint between aluminum and steel. Characterization of the joints showed that FSW could be successfully used to join aluminum and steel in a T-configuration. The formation of intermetallic bonds and kissing bonds was carefully analyzed, and their contribution to the fracture behavior during loading in the skin and stringer directions was studied. Finite element simulation was used to determine the stress state at the interface during loading. The characterization results showed that the intermetallic, as an indicator of metallurgical bonding, is formed when special features are observed in the pattern of material flow. The fractography images showed that the stress state has a major impact on the fracture. The results of the present study can be effectively used to design and fabricate dissimilar joints, taking into account the loading condition.

Mechanical property improvement of a AA6082 alloy by the TV-CAP process as a novel SPD method

Abstract: Abstract Twisted variable channel angular pressing (TV-CAP) is a novel method. While it combines the advantages of equal channel angular pressing (ECAP), twist extrusion and direct extrusions, also it eliminates the disadvantages of these methods. Finite element analysis was also carried out in order to examine the design parameters, material flow and examine the effective strain values. Hardness and tensile tests were performed to examine the effect of TV-CAP on the mechanical properties of AA6082. In addition, optic microscope, SEM and TEM images were taken respectively and XRD, EDS and EBSD analyses were accomplished in order to investigate the microstructural analysis. As a result of this study, it has been observed that the material has hardened approximately 3 times compared to the annealed material and became 1.5 times stronger in terms of ultimate tensile strength. It was also concluded that, this new method is more efficient than twist extrusion and multi-pass equal channel angular pressing processes.

Revealing the mechanism of tool tilting on suppressing the formation of void defects in friction stir welding

Abstract: Experiments have proven tool tilting in friction stir welding (FSW) can effectively suppress the formation of void defects. However, the mechanism of tool tilting on suppressing the formation of void defects has not been revealed. In this study, a CFD model considering the influence of tool tilting is established. A non-uniform distribution of normal pressure at the tool-workpiece contact interfaces is proposed to relate to the tool tilt angle. The discrete particle tracing method is used to characterize the formation of void defects in FSW. The heat generation, temperature distribution and plastic flow behaviors between the case without (i.e. 0° tool tilt angle) and with (i.e. 2.5° tool tilt angle) tool tilting are quantitatively compared and analyzed. The results show the tool tilting in FSW leads to higher heat flux and temperature near the pin side in the middle and low parts of the workpiece. Moreover, the frictional shear stress at the pin side/workpiece contact interface significantly increases when the tool is tilting, leading to a higher driving force for the plastic material to flow. As a result, the material flows farther to the advancing side of the workpiece after bypassing the tool when the tool is tilting at 2.5°, which helps to heal the voids on the advancing side of the FSW joints. The higher temperature with higher frictional shear stress enhances the plastic material flow in the middle and low part of the joints when the tool is tilting, which is attributed to suppressing the void defects. The model is validated by experimental results.

On Friction, Heat Input, and Material Flow Initiation during Friction Stir Welding: Tool and Process Optimization

Abstract: The Friction Stir Welding (FSW) process depends entirely upon mechanical contact between the tool and the workpiece. As a result of this, all process phenomena and process outcomes such as weld geometry and mechanical properties are governed by FSW’s frictional system. The following work characterizes this system with a focus on process initialization, heat input and material flow. For this purpose, an experimental program for the isolated investigation of the frictional system was carried out. Short-term effects such as contact initiation, run-in behavior and frictional transitions are considered as well as the influences of process parameters and geometry. The system and its behavior are analyzed quantitatively and qualitatively by experiments altering the normal pressure, relative velocity, and tool geometry. The experiments demonstrate a self-similar behavior of the process, including an important wear transition which initiates the material flow, and a subsequent equilibrium of forces, heat balance, and temperatures. The interaction between the tool and the welded material is described, as is the link between the frictional interface and material flow initialization. Based on these findings, recommendations are provided for process optimization and tool design.

Friction Stir Welding/Processing of Various Metals with Working Tools of Different Materials and Its Peculiarities for Titanium Alloys: A Review

Abstract: A review of the state of research in the field of friction stir welding and processing has been carried out. The features of plastic flow in friction stir welding and their connection with the processes of adhesion friction are shown. The main direction of research is related to the features of friction stir welding of titanium alloys. Special attention is paid to the selection of working tool materials from various alloys for friction stir welding and the processing of titanium alloys. The main advantages and disadvantages of applying different types of tools for friction stir welding of titanium alloys are shown. Different mechanisms of tool wear in friction stir welding associated with the interaction of processed material and tools are demonstrated. Information on the influence of tool and material interaction at welding on the mechanical properties and operational characteristics of obtained joints is given.

Effects of welding physical fields on the microstructure evolution during dynamic-stationary shoulder friction stir welding

Abstract: Studying the physical fields in the friction stir welding (FSW) can reveal how they impact the microstructure of the joint, allowing one to develop more reliable joints. In this study, the Al–Cu dynamic-stationary shoulder friction stir welding (DSSFSW) was simulated using a three dimensional (3D) coupled Eulerian-Lagrangian finite element model to elucidate weld physical characteristics. The results revealed that the materials were mainly deposited in the areas between the weld centerline and the RS in DSSFSW. Compared with the bottom of the joint, the material flow velocity and range at the top region were higher, which leads to greater strain. The high strain prevented the growth of IMCs at the interface, therefore, the tensile strengths of the top and middle regions of the joint were significantly higher than those of the bottom. The above results verified the accuracy of the simulation.

On the utilization of radial extrusion to characterize fracture forming limits. Part I – methodology and tooling

Abstract: Abstract. This paper and its second part introduce a new formability test based on double-action radial extrusion to characterize material formability in the bulk-to-sheet material flow transitions that are commonly found in metal forming. This first part draws from the presentation of a multidirectional tool, which was designed to convert the vertical press stroke into horizontal movement of the extrusion punches towards each other, to aspects of experimental strain determination, fractography and finite element analysis. The methodology and tooling that are introduced here pave the way for subsequent testing and modelling of the different modes of fracture in three-dimensional to plane-stress evolutions, typical of bulk-to-sheet material flow transitions, by means of the new proposed test.

Investigation of the effect of welding and rotational speed on strain and temperature during friction stir welding of AA5083 and AA7075 using the CEL approach

Abstract: In this study, the friction stir welding between AA5083 and AA7075 is modeled using numerical methods, and the role of parameters affecting the process, such as welding speed and rotation speed on material flow, temperature, and strain, is studied. The temperature, strain, and material mixing were analyzed while welding AA7075 to AA5083 alloys using a Coupled Eulerian-Lagrangian (CEL) approach. It was discovered that the CEL approach had accurately anticipated the mixing of materials in the stir zone (SZ) by comparing the SZ of the samples fabricated experimentally and modeled by simulation. Results show that the temperature and strain increase dramatically as the rotation speed increases from 500 to 900 rev min−1. The material flow obtained from the simulation shows that with increasing rotational speed or decreasing welding speed, AA7075 is more stretched towards AA5083 in the sheet’s higher surfaces, indicating an increase in material flow intensity. Better material mixing and increased material flow allowed for the achievement of the maximum tensile strength at the welding and rotation speeds of 36 mm min−1 and 900 rev min−1.

Material flow and mechanical properties of friction stir welded AA 5052-H32 and AA6061-T6 alloys with Sc interlayer

Abstract: Abstract Friction stir welding (FSW) is superior to fusion welding for joining incompatible alloys. In FSW Al/Mg alloys, developing IMCs like Al3Mg2 and Al12Mg17 is almost predictable and undesirable. Continuous IMCs produce a simple fracture propagation path, increasing brittleness and reducing weld strength. AA5052-H32 and AA6061-T6 were joined with a scandium (Sc) strip in the current study to improve material flow and reduce brittleness. Interlayer added on these alloys are the military-grade aluminium alloys used in the production of ship hull constructions and armoured helicopters. During FSW, a threaded cylinder tool with a rotating speed (TRS) of 1600–2000 rpm, welding speed (WS) of 60–80 mm/min and tool pin depth (TPD) of 0.1–0.4 mm were used to create the weld joints. To improve the strength of the above material combination during FSW, a 2 mm thickness Sc interlayer was added. The mechanical and metallurgical characteristics of the weld joints were studied. The maximum ultimate tensile strength value obtained from the cylinder-threaded tool pin profile with 0.1 mm TPD presented 237.63 MPa. Experimental interpretations were employed using response surface methodology-box Behnken design (RSM- BBD). FSW variables’ influence was investigated using the analysis of variance (ANOVA) technique.

Mechanical joining of high-strength multi-material systems − trends and innovations

Abstract: In conjunction with mechanical joining processes. Mechanical joining processes play a key role for the realization of multi-material lightweight structures, which are essential with regard to environmental protection. However, joining of dissimilar high-strength materials is challenging due to the varying properties of the joining partners and due to their high flow stresses and often limited ductility. Thus, the evolution of established processes as well as the development of innovative and highly productive joining technologies are necessary. Requirements for a highly volatile production environment are versatility, flexibility, resilience and robustness. Within this contribution, current trends and innovations related to selected mechanical joining processes for enabling the material mix are outlined in order to point out opportunities to address these requirements in the future. In this context, joining using cold formed pin structures is presented as a promising approach for connecting dissimilar materials like metals to fibre-reinforced plastics. Furthermore, it is shown how the shear-clinching technology can be combined with a process-adapted application of locally limited heat treatment in order to promote the joinability and control the material flow during joining. A novel approach for reducing process forces and expanding process windows is the use of ultrasonic assistance for mechanical joining operations, which is demonstrated by the example of a nut staking process with superimposed high frequency oscillation. As concerns the widely used self-piercing riveting technique, current research activities relate not only to the further development of the joining process itself, for example by combining self-piercing riveting and tumbling, but also to the use of new rivet materials like high strain hardening stainless steels. In addition, the evolution towards mechanical joining 4.0 against the background of data-based process control in conjunction with of mechanical joining processes is also subject of the considerations.

Experimental based determination and analysis of mechanical properties of AA 3003 alloy welded with friction stir lap welding process

Abstract: In recent years, friction stir welding (FSW) methods have been used to obtain good joints with mechanical and physical process properties. The development of FSW lap joint assembly will expand its use in a high number of industrial applications that can benefit from this technology. In this paper a study based on experimental methods were performed on FSW lap joints. The investigation includes the interface morphology and mechanical properties of the joint assembly. Experimental measurements were carried out on micro-hardness; tensile shear test, resulting material flow as well as the effect of flow variation on the obtained mechanical properties of FSW butt lap joints of aluminium alloy AA3003. The study also presents the effects of different welding parameters on the lap joints assembly structure. It was found that the hardness in the welded region is significantly lower with respect to the base material. The fracture analysis shows the characteristics of ductile-brittle mixed fracture.

The Use of Material Flow Cost Accounting in Supporting the Cost of a Sustainable Product to Achieving Green Productivity1

Abstract: The current study sought to measure the cost of the sustainable product and demonstrate its role in increasing green productivity through the application of the material flow cost accounting technique, which works on the optimal utilization of materials and energy and the reduction of environmental impacts. The research aims to clarify the knowledge foundations for material flow cost accounting and how to measure the cost of a sustainable product, in addition to studying the material flow cost accounting technique that helps reduce the cost of products and increase green productivity. The study concluded that material flow cost accounting contributes to measuring the cost of a sustainable product, which helps the economic unit to reduce costs and determine the environmental costs represented by waste and emissions generated from the production process.

Development of Fused Deposition Modeling of Multiple Materials (FD3M) Through Dynamic Coaxial Extrusion

Abstract: Multimaterial additive manufacturing is expanding the design space realizable with 3D printing, yet is largely constrained to sequential deposition of each individual material. The ability to coextrude two materials and change the ratio of materials while printing would enable custom-tailored polymer composites. Here, the evolution of a dynamic material coextrusion process for additive manufacturing capable of printing any ratio between and including two neat input materials is described across 3 hot-end generations and 14 implemented design iterations. The designs evolved with increased understanding of manufacturing constraints associated with the additive manufacturing of metal components with internal flow bore diameters on the order of 2 mm and typical bore length around 50 mm. The second generation overcame this issue by partitioning the design into two pieces to locate the flow channel geometry at the interface between the components so that the details could be easily printed on the components' external surfaces. The third concept generation then focused on minimizing flow channel volume to reduce the average length when transitioning between materials by 92%. The third-generation design was also used to investigate the improvements in dimensional stability during annealing of acrylonitrile butadiene styrene (ABS) made possible by coextruding ABS with a polycarbonate (PC) core. The standard deviation of part shrinkage after annealing was 7.08% for the neat ABS but reduced to 0.24% for the coextruded ABS/PC components.

An Experimental and Numerical Study on Aluminum Alloy Tailor Heat Treated Blanks

Abstract: Information is presented on the conceptualization, experimental study, and numerical process simulation of tailor heat treated aluminum alloy blanks. This concept is intended to improve the forming behavior of aluminum parts in challenging conditions. The implementation requires precise control of laser heat treatment parameters within a suitable industrial framework. The study details material properties, heat treatment parameters, and experimental results for the strength and elongation properties of an AA6063-T6 aluminum alloy. Constitutive modeling is applied using the Hocket–Sherby equation, which allowed us to establish a correlation between laser heat treatment maximum temperature and the corresponding material softening degree. Based on the generated flow stress–strain curves, a numerical simulation of a representative case study was performed with Abaqus finite element software highlighting potential improvements of tailor heat treated blanks (THTB). The influence and effectiveness of heat-affected zone (HAZ) dimensions and material softening were analyzed.

Control strategy for angular gradations by means of the flow forming process

Abstract: Abstract. Climate change, rare resources and industrial transformation processes lead to a rising demand of multi-complex lightweight forming parts, especially in aerospace and automotive sectors. In these industries, flow forming is often used to produce cylindrical forming parts by reducing the wall thickness of tubular semifinished parts, e.g. for the production of hydraulic cylinders or gear shafts. The complexity and functionality of flow forming workpieces could be significantly increased by locally graded microstructure and geometry structures. This enables customized complex hardness distributions at wear surfaces or magnetic QR codes for a unique, tamper-proof product identification. The production of those complex, 2D (axial and angular) graded forming parts currently depicts a great challenge for the process and requires new solutions and strategies. Hence, this paper proposes a novel control strategy that includes online measurements from an absolute encoder to determine the angular workpiece position. Workpieces of AISI 304L stainless steel with 2D-graded structures are successfully manufactured using this new strategy and analyzed regarding the possible accuracy and resolution of the gradation. At this point, a dependency of the gradations on the sensor and actuator dynamics, accuracy and geometry could be noted. It is further evaluated how the control strategy could be extended by an observer-based closed-loop property control approach to enhance the accuracy of the suggested strategy.

Improving material flow in a modified production system

Abstract: Material flow management aims to ensure the consistency of supply and reliability of the production processes being carried out. The aim of the article is to present a model of material flow organisation in a changing production system operating under small batch production conditions. Carrying out simulations for various production scenarios will be the basis for developing an effective method of material flow management in small batch production of cutting tools.