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Modified bone cement microstructure numeric simulation

Nowacki J., Sajek A.

Journal of Achievements in Materials and Manufacturing Engineering

2010

Vol. 43, nr 2

533--541

Purpose: The paper aimed at determining the strength of modified bone cement microstructure. Modification with aqueous hormone solution stimulates the growth of bone at a hip-joint endoprosthesis implantation site. Design/methodology/approach: In the first place, microstructure of modified cements was examined. This examination was a basis for statistical description of porosity obtained as a result of modification. Statistical data were used to create microstructure models in a programme being in agreement with FEM technique. Simulations were carried out on structures of 2 types of pores, i.e. those containing water and empty ones. Findings: Modification with aqueous solutions of modifying agents affects the structure and properties of bone cements. This is caused by formation of pores filled with aqueous solutions of modifying agents. This type of porosity decreases mechanical properties less than air-filled pores. Research limitations/implications: Numerical simulation of the stress and displacement pattern in juncture microstructure should be expanded with a simulation of bone-cement-implant system operation, which will allow estimation of an optimum value of modifying agent admixture, i.e. a value enabling the improvement of juncture biocompatibility not lowering at the same time its mechanical properties below a level set up in standard specifications. Practical implications: Microstructure simulations performed confirmed a manner of modified cement cracking observed on fractures. They showed formation of pore agglomerations where concentrating stresses may bring about the appearance of dangerous micro-fractures. Originality/value: Cement modification with aqueous solution and examination of the effect of admixture on microstructure mechanical properties.

Criteria of microstructural assessment of the conventional and new TBC layers

Moskal G.

Archives of Materials Science and Engineering

2009

Vol. 38, nr 1

19-25

Purpose: The purpose of this paper is to present principles and criteria of microstructural assessment of thermal barrier coatings (TBCs). The conventional layers are described in expert papers, whereas there is no literature on new type of thermal barrier coatings on the basis of RE2Zr2O7 compounds Design/methodology/approach: The study was carried out on the TBC layers, sprayed by using the conventional powders on the basis of yttria stabilized zirconium (YSZ) oxides and by using the powders of pyrochlore structure. Industrial powder type Gd2Zr2O7 was sprayed as a representative of a new group of materials to be sprayed with the APS method. Findings: The carried out analysis allowed to compare guidelines and criteria, which were used to assess the conventional TBC layer and their reference to barrier layers of a new type. The carried out study proved that heretofore used criteria of assessment for the TBC layers by using the conventional powders are sufficient to assess layers of a new type. Research limitations/implications: The carried out study suggests necessity to verify the received results in the case of the TBC layers, sprayed by using the powders of pyrochlore structures of other types. Practical implications: The received results show the possibility of using the heretofore criteria of microstructural assessment of the TBC layers as sufficient to get information on quality of the TBC layers of a new type. Originality/value: The information concerning basic principles in assessment of microstructural layers of a new type, which are sprayed with the APS method on high temperature creep resisting alloys, is an original value presented in this paper.