Ceramic filters are used to avoid slag and impurities in foundry applications. When not properly applied, the presence of these filters may have a significant influence on mould filling. 3-D casting simulation has bee...Ceramic filters are used to avoid slag and impurities in foundry applications. When not properly applied, the presence of these filters may have a significant influence on mould filling. 3-D casting simulation has been applied to study the effects of the use of a ceramic filter on the metal flow in a gating system. Instead of using a pressure drop model to represent the behaviour of a fluid metal flow passing through a filter, a real exact filter geometry, which is created by a high resolution CT-scan and a non-destructive imaging technique, in the gating system is applied in the simulation. In this research, nodular cast iron is poured into a block casting. A depressurized gating system is used. After a choke, a filter with different orientations is placed in the system. Mould filling coupled with temperature is simulated. Geometries using different orientations of the filter, and without the filter have been researched. The simulated results show that the filter has no influence on the pouring time of the casting if the choke section is small enough compared to the effective section of the filter. Although the filter has no significant influence on the flow patterns in the block casting itself, the flow patterns in the filter zone are different. When the liquid metal passes a horizontal filter, it will be broken into many small streams and show a shower effect. After the part under the filter is full, the shower effect disappears. When the filter is located at the vertical position, due to the gravity, the shower effect is less. If no filter presents on the system, the liquid metal passes through the filter zone with a high speed and causes surface turbulence.展开更多
A program on the solidification process of horizontal centrifugal casting coupled with eutectic carbides segregation has been developed in this paper. Due to the geometrical features of work roll, a cylindrical coordi...A program on the solidification process of horizontal centrifugal casting coupled with eutectic carbides segregation has been developed in this paper. Due to the geometrical features of work roll, a cylindrical coordinate system was used. The temperature field of the outer layer at the end of filling process was imported as the initial temperature condition for the solidification process. The model of eutectic carbides segregation caused by different densities between eutectic MC and the molten steel was coupled in the program. The temperature field of the outer layer of work roll during horizontal centrifugal casting process was investigated. Results show that the outer layer has a ＂sandwich shape＂ solid fraction manner. Results also indicate that the segregation of eutectic MC is quite severe during centrifugal casting process. It forms four zones of different content of carbides in radial direction. The simulated results of MC carbides segregation phenomenon agree with the experimental observations.展开更多
Large bone defects are a challenge for orthopedic surgery.Natural(bone grafts)and synthetic biomaterials have been proposed but several problems arise such as biomechanical resistance or viral/bacterial safety.The use...Large bone defects are a challenge for orthopedic surgery.Natural(bone grafts)and synthetic biomaterials have been proposed but several problems arise such as biomechanical resistance or viral/bacterial safety.The use of metallic foams could be a solution to improve mechanical resistance and promote osseointegration of large porous metal devices.Titanium cylinders have been prepared by additive manufacturing(3D printing/rapid prototyping)with a geometric or trabecular microarchitecture.They were implanted in the femoral condyles of aged ewes;the animals were left in stabling for 90 and 270 days.A double calcein labeling was done before sacrifice;bones were analyzed by histomorphometry.Neither bone volume,bone/titanium interface nor mineralization rate were influenced by the cylinder’s microarchitecture;the morphometric parameters did not significantly increase over time.Bone anchoring occurred on the margins of the cylinders and some trabeculae extended in the core of the cylinders but the amount of bone inside the cylinders remained low.The rigid titanium cylinders preserved bone cells from strains in the core of the cylinders.Additive manufacturing is an interesting tool to prepare 3D metallic scaffolds,but microarchitecture does not seem as crucial as expected and anchoring seems limited to the first millimeters of the graft.展开更多
文摘Ceramic filters are used to avoid slag and impurities in foundry applications. When not properly applied, the presence of these filters may have a significant influence on mould filling. 3-D casting simulation has been applied to study the effects of the use of a ceramic filter on the metal flow in a gating system. Instead of using a pressure drop model to represent the behaviour of a fluid metal flow passing through a filter, a real exact filter geometry, which is created by a high resolution CT-scan and a non-destructive imaging technique, in the gating system is applied in the simulation. In this research, nodular cast iron is poured into a block casting. A depressurized gating system is used. After a choke, a filter with different orientations is placed in the system. Mould filling coupled with temperature is simulated. Geometries using different orientations of the filter, and without the filter have been researched. The simulated results show that the filter has no influence on the pouring time of the casting if the choke section is small enough compared to the effective section of the filter. Although the filter has no significant influence on the flow patterns in the block casting itself, the flow patterns in the filter zone are different. When the liquid metal passes a horizontal filter, it will be broken into many small streams and show a shower effect. After the part under the filter is full, the shower effect disappears. When the filter is located at the vertical position, due to the gravity, the shower effect is less. If no filter presents on the system, the liquid metal passes through the filter zone with a high speed and causes surface turbulence.
基金the financial support from CAS/SAFEA International Partnership Program for Creative Research Teams
文摘A program on the solidification process of horizontal centrifugal casting coupled with eutectic carbides segregation has been developed in this paper. Due to the geometrical features of work roll, a cylindrical coordinate system was used. The temperature field of the outer layer at the end of filling process was imported as the initial temperature condition for the solidification process. The model of eutectic carbides segregation caused by different densities between eutectic MC and the molten steel was coupled in the program. The temperature field of the outer layer of work roll during horizontal centrifugal casting process was investigated. Results show that the outer layer has a ＂sandwich shape＂ solid fraction manner. Results also indicate that the segregation of eutectic MC is quite severe during centrifugal casting process. It forms four zones of different content of carbides in radial direction. The simulated results of MC carbides segregation phenomenon agree with the experimental observations.
基金This work was supported partially by the Walloon Region(CWALity project NEXTBONE:Convention n_1610093).This work was made possible by grants from the CHU of Angers(University hospital),project MOCONA and the French Ministry of Research.
文摘Large bone defects are a challenge for orthopedic surgery.Natural(bone grafts)and synthetic biomaterials have been proposed but several problems arise such as biomechanical resistance or viral/bacterial safety.The use of metallic foams could be a solution to improve mechanical resistance and promote osseointegration of large porous metal devices.Titanium cylinders have been prepared by additive manufacturing(3D printing/rapid prototyping)with a geometric or trabecular microarchitecture.They were implanted in the femoral condyles of aged ewes;the animals were left in stabling for 90 and 270 days.A double calcein labeling was done before sacrifice;bones were analyzed by histomorphometry.Neither bone volume,bone/titanium interface nor mineralization rate were influenced by the cylinder’s microarchitecture;the morphometric parameters did not significantly increase over time.Bone anchoring occurred on the margins of the cylinders and some trabeculae extended in the core of the cylinders but the amount of bone inside the cylinders remained low.The rigid titanium cylinders preserved bone cells from strains in the core of the cylinders.Additive manufacturing is an interesting tool to prepare 3D metallic scaffolds,but microarchitecture does not seem as crucial as expected and anchoring seems limited to the first millimeters of the graft.
