Marjan Bahraminasab

Al 2 O 3 -Ti functionally graded material prepared by spark plasma sintering for orthopaedic applications

Orthopaedic prostheses still suffer from limited lifetime which imposes revision surgery with the associated risks involved. This, to some extent, is related to the vulnerability of the biomaterials used for their fabrication that are commonly single-constituent and uniform. Therefore, hybrid biomaterials such as composites and functionally graded materials (FGMs) are being developed to overcome the shortcomings of available biomaterials. The present paper focuses on the study of the structural, physical and mechanical properties of a FGM made of alumina-titanium fabricated by spark plasma sintering (SPS). The corresponding composites of the individual FGM layer were also fabricated. After sintering, the structural, mechanical and physical tests were carried out. The microstructural analysis using X-ray diffraction revealed the presence of Ti3Al and TiAl in the composites, particularly with the increase of titanium content. Scanning electron micrographs revealed good adhesion and bonding between the two phases and between the FGM layers. The hardness and bending strength of the composites and FGM samples were tested and it was found that the increase in amount of Ti volume fraction decreases these properties monotonically. Furthermore, the sintering behaviour and fracture mechanisms of the FGM sample were studied and discussed.

Multicriteria Decision Analysis in Improving Quality of Design in Femoral Component of Knee Prostheses: Influence of Interface Geometry and Material

Knee prostheses as medical products require careful application of quality and design tool to ensure the best performance. Therefore, quality function deployment (QFD) was proposed as a quality tool to systematically integrate consumer’s expectation to perceived needs by medical and design team and to explicitly address the translation of customer needs into engineering characteristics. In this study, full factorial design of experiment (DOE) method was accompanied by finite element analysis (FEA) to evaluate the effect of inner contours of femoral component on mechanical stability of the implant and biomechanical stresses within the implant components and adjacent bone areas with preservation of the outer contours for standard Co-Cr alloy and a promising functionally graded material (FGM). The ANOVA revealed that the inner shape of femoral component influenced the performance measures in which the angle between the distal and anterior cuts and the angle between the distal and posterior cuts were greatly influential. In the final ranking of alternatives, using multicriteria decision analysis (MCDA), the designs with FGM was ranked first over the Co-Cr femoral component, but the original design with Co-Cr material was not the best choice femoral component, among the top ranked design with the same material.

Preliminary evaluations on development of new materials for hip joint femoral head

Development and selection of a proper biomaterial with diverse properties (i.e. physical, mechanical, wear, corrosion, and many others) for hip femoral head is one of the most exigent tasks. Improper material often causes component failure during functioning. Therefore, in this study, a series of implant materials containing tungsten of different weight percentages were fabricated by high temperature vacuum casting induction furnace and the physical, mechanical, wear, and corrosion properties were examined. The proportions were varied from 0 wt% to 4 wt% in a cobalt–chromium alloy (Co–30Cr–4Mo–1Ni). The mechanical properties were tested by the micro-hardness tester and the compression testing machine, while the wear performance was analyzed through a pin-on-disc tribometer under different operating conditions at room temperature. Corrosion resistance was analyzed under NaCl solution by the electrochemical test method. Due to the conflict between the properties obtained, the Vise Kriterijumska Optimizacija Kompromisno Resenjemeaning (VIKOR) method integrated with analytic hierarchy process (AHP) was applied to choose the best material among the set of alternatives, where AHP was used to determine criteria weights, and VIKOR approach was used to rank the alternatives. From the results obtained, it was found that Co–30Cr–4Mo–1Ni implant material containing 2 wt% tungsten provides the best combination of the properties for a given application (i.e. hip femoral head).

State of the art review on design and manufacture of hybrid biomedical materials: Hip and knee prostheses:

The trend in biomaterials development has now headed for tailoring the properties and making hybrid materials to achieve the optimal performance metrics in a product. Modern manufacturing processes along with advanced computational techniques enable systematical fabrication of new biomaterials by design strategy. Functionally graded materials as a recent group of hybrid materials have found numerous applications in biomedical area, particularly for making orthopedic prostheses. This article, therefore, seeks to address the following research questions: (RQ1) What is the desired structure of orthopedic hybrid materials? (RQ2) What is the contribution of the literature in the development of hybrid materials in the field of orthopedic research? (RQ3) Which type of manufacturing approaches is prevalently used to build these materials for knee and hip implants? (RQ4) Is there any inadequacy in the methods applied?

Using Design of Experiments Methods for Assessing Peak Contact Pressure to Material Properties of Soft Tissue in Human Knee

Contact pressure in the knee joint is a key element in the mechanisms of knee pain and osteoarthritis. Assessing the contact pressure in tibiofemoral joint is a challenging mechanical problem due to uncertainty in material properties. In this study, a sensitivity analysis of tibiofemoral peak contact pressure to the material properties of the soft tissue was carried out through fractional factorial and Box-Behnken designs. The cartilage was modeled as linear elastic material, and in addition to its elastic modulus, interaction effects of soft tissue material properties were added compared to previous research. The results indicated that elastic modulus of the cartilage is the most effective factor. Interaction effects of axial/radial modulus with elastic modulus of cartilage, circumferential and axial/radial moduli of meniscus were other influential factors. Furthermore this study showed how design of experiment methods can help designers to reduce the number of finite element analyses and to better interpret the results.

The Importance of Decision Support in Materials Selection

The selection of materials at all stages of the product design process requires effective decision-making. The nature of the problem is both complex and varying from having to consider a large number of available materials and vague information in the early design stages to a small number of acceptable materials and detailed information in the later design stages. The inclusion of hybrid materials and newly developed materials although offering the potential of enhanced performance can further exacerbate the problem. To fully satisfy the design requirements, decision-making support is essential to correctly select the most appropriate design, materials, and manufacturing processes in the design and development of new engineering products.

Screening of Materials

The screening methods available for materials selection range from simple manual procedures to sophisticated computer-based packages, as either stand-alone, or linked to materials’ properties databases, or integrated with other design support tools. Of all the current methods available, the most popular way of screening materials is via the use of materials selection charts (the so-called “Ashby” method). The charts allow a direct comparison to be easily made between different material properties, or a limited combination of material properties, via the use of performance indices. Multi-criteria decision-making techniques can also be applied when a large number of materials’ selection criteria need to be considered simultaneously.

Multi-attribute decision-making for ranking of candidate materials

Multi-Attribute Decision-Making methods have become accepted for determining the choice of materials when the “lowest price” approach does not realize the optimum result. These methods are especially useful for high technology markets, where product differentiation and competitive advantage are often achievable with just small gains in material performance. The strategy of applying objective and subjective weightings for all types of criteria is described in materials selection as well as a method to incorporate them. The whole process for optimal decision-making in materials selection includes selecting the proper ranking method, as well as the aggregation method for situations when there are a lot of similar alternatives. As a result, a systematic approach to optimal materials selection is explained that will be beneficial to materials engineers and designers.

Biocomposites for Hard Tissue Replacement and Repair

Biomaterials with single composition suffer from shortcomings limiting their lifetime and sometimes restricting their applications. Therefore, biocomposites have been started to develop by combining two or more biomaterials with different characteristics to provide superior properties compared to each biomaterial alone. These materials can be flexibly tailored to provide material properties fitted with a given application. In their way to be designed, the principles exist in human body tissues that can be used as a guide. This helps in providing biomimetic materials. Over the recent past decades, research on composite materials for biomedical applications has been progressively increased. A large number of composites, therefore, have been developed and tested for hard tissue replacements and repair. This includes total joint replacements, devices used for fractured bone treatment, dental restorative materials, dental implants, and bone scaffolds. This chapter provides information on permanent and temporary implants and the essential material requirements for their applications. Furthermore, it specifically explains different types of composite biomaterials used in hard tissue replacements and repair. However, this chapter does not include ancillary implants or fasteners used to treat fractured bone.

Biocompatibility evaluation and corrosion resistance of tungsten added Co-30Cr-4Mo-1Ni alloy

Biomaterials are continuously being developed to overcome the drawbacks of existing materials and provide improved function in artificial organs. Currently Co-Cr based alloys are used in many medical applications such as hip and knee implants which still require modification to better perform. In this article, therefore, the influence of tungsten allying element on electrochemical corrosion resistance and biocompatibility behaviour of a recently developed Co-30Cr-4Mo-1Ni alloy composition were investigated. The tungsten modified alloys were prepared by using a high temperature vertical vacuum casting technique at five different weight percentages (0-4wt.% tungsten). The electrochemical corrosion behaviour of all the samples under NaCl solution was studied by using potentiodynamic scan method. The corrosion characteristics were investigated in terms of corrosion potential (Ecorr) and corrosion current density (Icorr). From the results of the analysis, it was observed that out of all samples, an alloy with 2wt.% of tungsten in composition (i.e. Co-30Cr-4Mo-1Ni-2W) exhibited better corrosion resistance. Furthermore, histopathological evaluations in subcutaneous tissue were performed in rats according to the standard ISO 10993 to examine the biocompatibility of the prepared samples. The results showed no evidence of inflammatory cell migration, no epidermal necrosis, no vacuolar degeneration of basal cell, no adnexal atrophy and vesicle formation of any samples. The obtained findings indicate that Co-30Cr-4Mo-1Ni-2W can be used in biomedical applications including femoral component of hip and knee implants.