Additive manufacturing of porous Ti-based alloys for biomedical applications – a review

Published ArticleTitanium (together with its alloys) has become 'king' among biometals and has demonstrated to function perfectly in the human body. Despite its well-known celebrated biocompatibility properties, it has a major drawback due to its relatively high Elastic modulus as compared to bony tissue. Using additive manufacturing (AM) methods to manufacture porous Ti-based implants by a process called porosification would greatly reduce the Elastic modulus to a value suitable for biomedical applications. Varying the processing parameters of AM methods could lead to production of graded pore implants. Scanning speed was identified as the major influencing parameter which could be varied to produce pore-graded implants. Even though the fundamental principles of manufacturing porous Ti-implants are very well grounded in literature, the optimum pore size and corresponding mechanical properties for bone ingrowth are yet to be determined

Assessment of Stress Raiser Factor Using Finite Element Solvers

Published ArticleThe stress raisers factor around circular holes in a plate exposed to uniform tensile load at the edges has been studied using Finite Element Analysis solvers. The effect of mesh quality on stress raisers factor, the maximum Von Mises stresses, the computing time, and the percentage error has been examined. 4 Node Quadrilateral Element and 8 Node Quadrilateral Element were utilized respectively as first-order component (4NQE) and higher-order component (8NQE) to assess the maximum Von Mises stress and the numerical stress raiser factor (Kn) at various mesh sizes. The maximum Von Mises stress and the stress raiser factor were determined using the following finite element solvers: ABAQUS, ANSYS, CATIA, STRAND 7, ALGOR, COSMOS/M, and FEMAP. The estimations of the numerical stress raiser factor (Kn) were compared with the theoretical stress raiser factor (Kt). There were discrepancies observed between the maximum Von Mises stresses of the FEA solvers

Does the Interpersonal Dimension of Goleman’s Emotional Intelligence Model Predict Effective Leadership?

ArticleThe purpose of the study is to examine the relationship between social awareness and relationship management as the interpersonal dimension of Goleman’s emotional intelligence and their ability to predict effective leadership in the Ghanaian banking industry. Using a descriptive cross-sectional survey design, a sample size of 307 employees was determined for the study from six commercial banks selected from Ghana’s Club 100 rankings. A multi-stage sampling technique was used in the selection of the banks, their branches and employees who participated in the study. Standardized questionnaires served as the instruments for data collection. Hierarchical multiple regression analysis was used to analyze the data. A significant positive relationship exists between social awareness and leadership effectiveness as well as relationship management and leadership effectiveness. The results also showed that demographic variables (gender, age, educational level, tenure) significantly moderated the relationship between social awareness and leadership effectiveness as well as relationship management and leadership effectiveness

Numerical modelling of DMLS Ti6Al4V(ELI) polygon structures

Numerical modelling is particularly advantageous for analysing structures with complex behaviour. It is used to predict the mechanical properties of structures. Analytical modelling, on the contrary, has limited capacity for predicting the behaviour, particularly of structures, because it is based on mathematical equations that do not always exactly represent the geometry of the model. In such cases, numerical modelling is used for predicting structural bending, axial deformation, and buckling behaviour. This study documents numerical modelling of different types of polygon structures. To reduce computation costs, planar and extruded Ti6Al4V(ELI) hexagonal shell structures were used to predict stresses in the out-of-plane and in-plane directions. This was followed by numerical modelling of different types of planar polygon structures to predict their load-bearing capacity and stiffness. Thereafter, the hexagonal polygon was subjected to out-of-plane and in-plane uniaxial compression loads. This was done to compare the bending and buckling behaviour of finite element (FE) models to analytical models. The numerical and analytical results were then compared to determine how the ratio (t/L) of the wall thickness (t) and length of the polygon members (L) influenced the effective stiffness of the hexagonal polygon. The triangular polygon was seen to have the greatest load-bearing capacity and stiffness of all polygons that were modelled. The hexagonal model was observed to generate deformations due to compression, similar to those reported in literature. The critical buckling loads for the analytical honeycomb (HC) models were found to be below the yield stress for (1-, 1.125-, and 1.25-mm wall thicknesses) and above the yield stress for all FE HC models, respectively. The effective stiffness of the HC models were observed to increase with the increasing (t/L) ratio, for both the numerical and analytical models

Optimal Process Parameters for In Situ Alloyed Ti15Mo Structures by Laser Powder Bed Fusion

Powder Bed Fusion (PBF) is a manufacturing method with the advantage that it can produce objects of complex geometry. Additionally, it opens great opportunities to synthesize new materials from elemental powder using an in situ alloying approach. Potential of the in situ PBF alloying approach is nevertheless not well understood due to lack of experimental knowledge and information on the influence of process parameters on the microstructure, homogeneity and properties of the final materials. This investigation is focused on Ti15Mo alloy that was chosen as a promising β-type alloy for biomedical applications due to low Young’s modulus, close to the mechanical properties of bones. Geometrical characteristics of single tracks were investigated at a wide range of laser powers and scanning speeds. Threshold of enthalpy ratio to transition from conduction to keyhole mode was found. To study the distributions of molybdenum in Ti matrix, X-ray nanoCT scans and SEM EDS were performed. Effects of hatch distance and scanning strategy on the layer surface morphology were investigated. Microstructure and mechanical properties of as-built specimens were analyzed. Illustrated effects of each process parameter on the synthesized material is paramount to successful manufacturing of advanced implants with mechanical properties close to bones.Mechanical Engineerin