Topic
Material flow
About: Material flow is a research topic. Over the lifetime, 3050 publications have been published within this topic receiving 36844 citations. The topic is also known as: material stream.
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TL;DR: In this paper, a flow stress model for ultra-precision machining process is presented, which is based on the surface model analogy developed for metal forming coupled with the crystal plasticity effect.
Abstract: Inducing compressive stress on the machined surface is a desirable practice in ultra-precision metal cutting to improve the part quality. An important parameter to analyse the machining performance is the material flow stress, which plays a crucial role in the material deformation characteristics in machining. As the dimensions of the workpiece descend from macro to micro scale in metal forming, the flow stress reduces accordingly. Hence, based on the ‘surface model’ analogy developed for metal forming coupled with the crystal plasticity effect, an attempt has been made in this study to construct a flow stress model for ultra-precision machining process. While developing the model, for the first time, the size factor (η, d/ho) is introduced to incorporate the material ‘grain size effect’ in ultra-precision machining. The proposed model is validated with experimental results of Al6082 alloy of different grain sizes. Orthogonal turning experiments were conducted on an ultra-precision machine by utilizing the concept of ‘cutting edge radius effect’, which is identified as the relative tool sharpness (RTS) and quantified as the ratio of undeformed chip thickness (hc) to edge radius (rn). In this paper, the investigation on the material flow stress is carried out by considering the phenomenon of the shifting material flow separation (cutting) from primary deformation zone to material deformation (ploughing and rubbing) at tertiary deformation zone. The distribution of contact stresses along the tool rake and flank faces at the minimum value of RTS (hc/rn) of 0.01 substantiates the ploughing effect (compressive stresses are induced into the machined layer) rather than chip separation. Moreover, the distinct variation of the machined surface quality and μ-chip morphology at the extreme low and high RTS conditions distinguishes the material ploughing effect from the cutting effect. Additionally, for the same RTS value, it is found that different grain materials (Cu and Mg alloy) exhibited variations in flow stress, chip morphology and surface quality. Therefore, material grain size is an influential factor for analysing machining performance with material flow stress at ultra-precision level.
39 citations
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TL;DR: In this paper, a viscoplastic flow of granular solids within rigid walls is modeled using continuum mechanics, in which the discontinuity function is taken as in previous works by Gray and Stiles, while the flow rule is modeled by the von-Mises criterion.
39 citations
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TL;DR: In this paper, the authors developed indicators for evaluating the circularity of material flows at regional level, based on circulation of waste materials rather than material circulation for the whole value chain from manufacturing to reuse and recycling.
39 citations
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TL;DR: In this paper, the authors provide two rectilinear layout configurations, single-and double-spine, for overhead track design, given the locations of loadports and a pod from-to-flow matrix.
Abstract: Overhead automated material handling systems have become the only material handling solution in semiconductor fabs to achieve zero footprint material handling in the expensive cleanroom floor. This paper provides two rectilinear layout configurations, single-spine and double-spine, for overhead track design. Given the locations of loadports and a pod from-to flow matrix, we determine the rectilinear layout of material flow systems with the objective of minimizing the total loaded travel distances. The optimal single-spine problem can be transformed to a known single-facility layout problem and solved with a linear-time algorithm. The optimal double-spine layout is obtained from the optimal single X-spine and Y-spine and is formulated as an allocation problem. We demonstrate the system designs by a numerical example. The resulting spine layouts are then compared with the Minimum Rectilinear Steiner Tree (MRST) and Shortest Rectilinear Flow Network (SRFN) layouts. MRST layout provides the shortest track length while the SRFN layout guarantees the shortest flow distances. The result shows that spine layout is a potential track layout pattern with respect to simplicity, track lengths and flow distances for overhead flow systems.
39 citations
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TL;DR: In this article, the impact of sector aggregation bias in Environmentally Extended Input Output (EEIO) models, focusing on raw material flows, was investigated and the results showed that industries with high raw material use deserve special attention in EEIO models.
39 citations