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Neural network prediction of mechanical properties of porous NiTi shape memory alloy
, Article Powder Metallurgy ; Volume 54, Issue 3 , Nov , 2011 , Pages 450-454 ; 00325899 (ISSN) ; Hafizpour, H. R ; Sadrnezhaad, S. K ; Akhondzadeh, A ; Abbasi Gharacheh, M ; Sharif University of Technology
2011
Abstract
A multilayer back propagation learning algorithm was used as an artificial neural network tool to predict the mechanical properties of porous NiTi shape memory alloys fabricated by press/sintering of the mixed powders. Effects of green porosity, sintering time and the ratio of the average Ti to Ni particle sizes on properties of the product were investigated. Hardness and tensile strength of the compacts were determined by hardness Rockwell B method and shear punch test. Three-fourths of 36 pairs of experimental data were used for training the network within the toolbox of the MATLAB software. Porosity, sintering time and particle size ratios were defined as the input variables of the model....
Pore control in SMA NiTi scaffolds via space holder usage
, Article Materials Science and Engineering C ; Volume 32, Issue 5 , 2012 , Pages 1266-1270 ; 09284931 (ISSN) ; Hosseini, S. R ; Sadrnezhaad, S. K ; Sharif University of Technology
2012
Abstract
Porous NiTi shape memory alloy (SMA) was fabricated by sintering of compressed constituent elements pre-mixed with NaCl or urea spacer holders. Effect of spacer to metal volume-ratio (r S) on shape, size, distribution and openness of the voids was probed by optical metallography, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) was used to determine the SMA transformation temperatures. Controllable void geometry helping osteoblast proliferation and bone cell growth was gained by addition of the spacers. At r S = 0.7, percentage of the open pores reached 52% while at r S = 1.43, interconnected pores with 200 to 500 μm diameter were...
Fabrication of porous NiTi alloy via powder metallurgy and its mechanical characterization by shear punch method
, Article Russian Journal of Non-Ferrous Metals ; Volume 53, Issue 2 , April , 2012 , Pages 169-175 ; 10678212 (ISSN) ; Hasannaeimi, V ; Saebnoori, E ; Shahrabi, T ; Sadrnezhaad, S. K ; Sharif University of Technology
Abstract
In this study, Porous NiTi shape memory alloy has been produced by mechanical alloying of the elemental Ni and Ti powders. The compacting process was done at two temperatures (warm and cold press) and then sintering at 980 and 1050°C was performed on the specimens. Microstructure and mechanical prop-erties of the samples were investigated by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction. Moreover, shear punch test (SPT) employed to investigate the effect of compaction pressure and sintering temperature on the mechanical properties of the fabricated samples. It was revealed that warm compaction/sintering resulted in 15% yield stress improvement and 20% ultimate...
Fabrication of porous NiTi-shape memory alloy objects by partially hydrided titanium powder for biomedical applications
, Article Materials and Design ; Volume 30, Issue 10 , 2009 , Pages 4483-4487 ; 02641275 (ISSN) ; Hosseini, S. A ; Sharif University of Technology
Abstract
Porous NiTi-shape memory alloy (SMA) is a promising biomaterial with desirable mechanical property and appropriate biocompatibility for human implant manufacturing. In this research, porous NiTi-SMAs have been successfully produced by using thermohydrogen process (THP). This process has capability of production of homogenous structures, appropriate pore-size distributions and short sintering times. The THP-SMA samples produced in this research have a low Young's modulus (19.8 GPa) and a high tensile strength of 255 MPa. These properties are close to those of the natural bone and can meet the mechanical property demands of the hard-tissue implants for heavy load-bearing applications. The...