Over the past 10 years, a novel cellular solid, Trabecular Metaf^ (TM), has been developed for use in the orthopedics industry as an ingrowth .scaffold. Manufactured using chemical vapor deposition (CVD) on top of a graphite foam substrate, this material has a regular matrix of interconnecting pores, high strength, and high porosity. Manufacturing difficulties encourage the application of stamping and forming technologies to increase CVD reactor throughput and reduce materials wastes. In this study, the formability of TM was evaluated using a novel camera-based system for measuring suiface strains, .since the conventional approach of printing or etching gridded patterns was not feasible. A forming limit diagram was then obtained using speciaity fabricated 1.65 mm thick sheets. No lubricant was used due to the cleanliness requirements for orthopedic implants.
Articles you may be interested inLaser peen forming induced two way bending of thin sheet metals and its mechanisms Abstract.This study examines the formability of a porous tantalum foam, known as trabecular metal (TM). Used as a bone ingrowth surface on orthopedic implants, TM is desirable due to its combination of high strength, low relative density, and excellent osteoconductive properties. This research aims to develop bend and stretch forming as a cost-effective alternative to net machining and EDM for manufacturing thin parts made of TM. Experimentally, bending about a single axis using a wiping die was studied by observing cracking and measuring springback. It was found that die radius and clearance strongly affect the springback properties of TM, while punch speed, embossings, die radius and clearance all influence cracking. Depending on the various combinations of die radius and clearance, springback factor ranged from .70-.91. To examine the affect of the foam microstructure, bending also was examined numerically using a horizontal hexagonal mesh. As the hexagonal cells were elongated along the sheet length, elastic springback decreased. This can be explained by the earlier onset of plastic hinging occurring at the vertices of the cells. While the numerical results matched the experimental results for the case of zero clearance, differences at higher clearances arose due to an imprecise characterization of the post-yield properties of tantalum. By changing the material properties of the struts, the models can be modified for use with other open-cell metallic foams.
This study examines the elastic recovery (springback) of a porous tantalum foam after sheet forming operations. The foam and sheet-like form is applicable to bone ingrowth surfaces on oithopedic implants and is desirable due to its combination of high strength, low relative density, and excellent osteoconductive properties. Forming of the foam improves nestability during manufacture and is essential to have the material achieve the desired shape. Experimentally, bending about a single axis using a wiping die is studied by obsening cracking and measuring springback. Die radius and clearance strongly affect the springback properties, while punch speed, embossing, die radius, and clearance all influence cracking. To study the effect of the foam microstructure, bending also is e.xamined numerically. A horizontal hexagonal mesh comprised of beam elements is employed, which allows for the densification that occurs during forming. The flow strength of individual tantalum struts is directly measured in an atomic force microscope. The numerical results show that as the hexagonal cells are elongated along the sheet length, elastic springback decreases. By changing the material properties of the struts, the models can be modified for use with other open-cell metallic foams,
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