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Abstract:
This work presents the results of fatigue tests of MAR 247 alloy flat specimens with aluminides layers of 20 or 40 µm thickness obtained in CVD process. Fatigue test was conducted at amplitude equal to half of maximum load and ranging between 300 and 650 MPa (stress asymmetry ratio R = 0, frequency f = 20 Hz). Additionally, 4 of the tests, characterized by the highest amplitude, were accompanied with non-contact strain field measurements by means of electronic speckle pattern interferometry and digital image correlation. Results of these measurements allowed to localize the areas of deformation concentration identified as the damage points of the surface layer or advanced crack presence in core material. Identification and observation of the development of deformation in localization areas allowed to assess fatigue-related phenomena in both layer and substrate materials.

Keywords:
aluminide layer, fatigue testing, full-field optical strain measurements, super nickel alloy

Abstract:
In the hereby presented work the authors describe a technique of high-compression-resistant biodegradable bone scaffold preparation. The methodology is based on the agglomeration of chitosan (CH) and chitosan/β-tricalcium phosphate (CH/TCP) microspheres and represents a novel approach to 3D matrices design for bone tissue engineering application. The materials were prepared from high deacetylation degree chitosan. The authors describe the method for scaffold fabrication, essential properties of the materials manufactured and the influence of various TCP concentrations on material morphology, mechanical properties (for dry and hydrated materials) and preliminary study on the interaction between CH or CH/TCP scaffolds and within cultured MG-63 osteoblast-like cells. The properties of the obtained materials were significantly affected by the calcium phosphate content, which had a particular influence on the granule microstructure, size distribution and inner biomaterial pore size. The water uptake ability was found to be lower for the materials enriched with the inorganic phase and tended to decrease with the increasing calcium phosphate concentration. The evaluation of mechanical properties has revealed that scaffolds produced with the usage of granule-based technology display a potential to be used as a load-bearing material since the Young’s modulus values were limited to the range of 200–500 MPa for dry materials and 15–20 MPa for the hydrated state of the scaffolds. The cell number, identified in three time points (48 h, 7 and 14 days) by Pico Green assay, was lower for the materials enriched with inorganic phase (75 % of control), however cell distribution, when compared to CH only biomaterial, was acknowledged as steadier on the surface of the material containing the highest calcium phosphate concentration.