Yongfeng Yang,Lin Zhang,Jing Liu,Mingxia Wu,Jian Liu,Yi Yang
To explore an eco-friendly approach to improve the milling performance of TC4 (Ti-6Al-4 V) alloy, pulsed magnetic field treatment and magnetofluid are simultaneously applied to the NbN-coated cemented carbide (WC–12Co) milling tools. To evaluate the coupling effect of pulsed magnetic field treatment with magnetofluid, milling experiments of TC4 were conducted under cutting fluid and magnetofluid lubrication , respectively. The milling force, tool wear, and workpiece surface quality of magnetic field treated tools were compared with those of untreated tools. When the cutting fluid was lubricated, the magnetic field treatment reduced the feed force by 8.8 %. In contrast, the magnetic field treatment reduced the feed force by 20.7 % when the magnetofluid was lubricated, which reduced tool wear and also weakened coating flaking. The coupling of the magnetic field treatment and the magnetofluid significantly improved the milling performance of the tool, reducing surface roughness by 40.9 % compared to the untreated tool with cutting fluid lubrication. The enhanced milling performance mainly results from the coupling effect of magnetic field treatment and magnetofluid, which has a strong magnetic response to the treated tool and the magnetofluid was attracted to the magnetized tool, enhancing the lubrication of the contact area. In addition, the enhanced mechanical properties (8.2 % increase in hardness, 13.1 % decrease in elastic modulus , and 4.5 % increase in thermal conductivity) resulting from the pulsed magnetic field treatment reduces the milling temperature (11.7 °C) also contribute to the enhanced milling performance.
Mesenchymal stem cells (MSCs) have potential uses for cartilage repair due to the potential of chondrogenic differentiation. However, developing effective approaches to regulate chondrogenesis in vivo remains a big challenging. To address the limitations, we propose the application
of magnetic fields, which features excellent performance for tissue penetration, good biocompatibility even at high magnetic strength, and wireless remote control. To test this concept, a pulsed magnetic field (PMF) was used to enhance the chondrogenesis of SPIO-labeled MSCs in a rat model
of cartilage defects. The SPIO labeling not only efficiently strengthens the responsiveness of MSCs to the externally applied PMF but also enables in vivo non-invasive monitoring of MSCs with magnetic resonance imaging (MRI). Importantly, biochemical and gene expression analysis reveal
the upregulation of certain cartilage biomarkers (i.e., SOX9 and COL2A1), showing that the PMF improves the chondrogenesis of MSCs via activation of the TGF-β/SMAD signaling pathways. These results indicate a promising scheme for stem cell-based cartilage repair.
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