Chip ignition in research on high-speed face milling AM50A magnesium alloy
The ignition of magnesium alloy chips is a problem during high speed dry machining in industry. It should be avoided in the practical production. Many factors including machining environment, material composition, tool geometry, cutting parameters etc. can influence the cutting processes. Among these factors, cutting parameters is one of most important elements to induce the ignition of magnesium alloys. AM50A is a commercial magnesium alloy which is widely used in industry. However, very few reports about the ignition conditions of AM50A magnesium alloy are available. In this paper, we investigated the ignition conditions of AM50A magnesium alloy at different cutting parameters. The relationship between ignition conditions and chip morphologies was further explored. The macro morphologies of the chips were observed by optical microscope and the micro structure were obtained by scanning electron microscope (SEM). It is found that the macro morphologies of chips can be characterized into powdered chip, tubular helical chip, acicular helical chip, and long belt chip, which correspond to the different ignition conditions. The powdered chips and acicular spiral chips are easily ignited. They have thinner lamellar thickness compared to the other two types of chips. These results may be used to analyze cutting process and prevent the chip ignition in dry machining magnesium alloy.
IMPACT OF DEPTH OF CUT ON CHIP FORMATION IN AZ91HP MAGNESIUM ALLOY MILLING WITH TOOLS OF VARYING CUTTING EDGE GEOMETRY
Safety of Mg milling processes can be expressed by means of the form and the number of fractions of chips formed during milling. This paper presents the state of the art of magnesium alloys milling technology in the aspect of chip fragmentation. Furthermore, the impact of the depth of cut ap and the rake angle γ on the number of chip fractions was analysed in the study. These were conducted on AZ91HP magnesium cast alloy and milling was performed with carbide tools of varying rake angle values (γ = 5o and γ = 30o). It was observed that less intense chip fragmentation occurs with decreasing depth of cut ap. The number of chip fractions was lower at the tool rake angle of γ = 30o. The test results were formulated as technological recommendations according to the number of generated chip fractions.
Semiautomated quantification of the fibrous tissue response to complex three-dimensional filamentous scaffolds using digital image analysis.
Fibrosis represents a relevant response to the implantation of biomaterials, which occurs not only at the tissue-material interface (fibrotic encapsulation) but also within the void fraction of complex three-dimensional (3D) biomaterial constructions (fibrotic ingrowth). Usual evaluation of the biocompatibility mostly depicts fibrosis at the interface of the biomaterial using semiquantitative scores. Here, the relations between encapsulation and infiltrating fibrotic growth are poorly represented. Virtual pathology and digital image analysis provide new strategies to assess fibrosis in a more differentiated way. In this study, we adopted a method previously used to quantify fibrosis in visceral organs to the quantification of fibrosis to 3D biomaterials. In a proof-of-concept study, we transferred the "Collagen Proportionate Area" (CPA) analysis from hepatology to the field of biomaterials. As one task of an experimental animal study, we used CPA analysis to quantify the fibrotic ingrowth into a filamentous scaffold after subcutaneous implantation. We were able to demonstrate that the application of the CPA analysis is well suited as an additional fibrosis evaluation strategy for new biomaterial constructions. The CPA method can contribute to a better understanding of the fibrotic interactions between 3D scaffolds and the host tissue responses.