Effect of Including Periodic Boundary Condition on the Fatigue Behaviour of Cancellous Bone

Trabecular bone consists of complex webbing of plates and struts, in which the properties vary across anatomical sites. The substantial constraint is the reduction on discretization error will reduce time in computation. So it is significant to consider carefully the boundary condition effects when utilizing such a complex multiaxial loading mode. Additionally, multiaxial loading gives distinct effects towards boundary condition compare to uniaxial whereas percentage prediction of fatigue failure is lower and applying of periodic boundary reflect a more precise real loading condition. 3D models of trabecular samples were constructed for FE simulations. The response of the models towards simulated mechanical loading was investigated. Preparation of the models begins with 3D reconstruction of micro-CT stacked images, follows by segmentation, meshing and refurbishing process. The resistance of trabecular bone deformation to loading in both uniaxial and multiaxial modes improved the fatigue life and failure with application of periodic boundary conditions

Monotonic and cyclic behaviour of trabecular bone under uniaxial and multiaxial loading

Biomechanics of bone has drawn major concern in research due to social and economic demand. In real life, trabecular bone is subjected to multiaxial stresses during routine physiological loading. Fatigue failure of the bone accounts for various clinical implications, thus studies and research to better understand the fatigue failure of the bone are needed. The overall aim of this study is to investigate the effect of torsional loading towards trabecular behaviour under compression in both monotonic and fatigue loading. Samples from femoral bovine trabecular bone were subjected to a series of monotonic and cyclic tests. Hill’s criterion was selected to determine the five combined stress ratio of compressive to shear stress for fatigue test. For finite element simulation, effect of morphology and orientation were investigated to predict fatigue life and plastic strain. The ultimate stress of the trabecular bone in monotonic compression and torsion were 14.22 and 8.95 MPa, respectively. In monotonic multiaxial loading, the ultimate stress was reduced to 2.5 MPa in compression and 3.8 MPa in torsion. Under fatigue compression, an endurance limit was found approximately at 25 % of ultimate compressive stress. Under multiaxial fatigue, the ability of the sample to retain shear stiffness with increased number of cycles is strongly correlated to the stress ratio. Fatigue life reduction was significant when the maximum shear stress is at least 24 % of the maximum compression stress. From the computational analysis, it was demonstrated that lower bone volume fraction (BV/TV), trabecular thickness (Tb.Th), and connectivity density (Conn.D) resulted in lower number of cycles to failure, regardless to the loading conditions. However, the number of cycles to failure was found to be negatively correlated to the value of structural model index (SMI). Off-axis orientation effect on the fatigue life of the trabecular bone was demonstrated the worst in horizontal trabecular bone model. In conclusion, the effect of torsional loading onto the mechanical behaviour of bovine trabecular bone was demonstrated throughout this study. It is apparent that torsional forces are the major factor that needs to be considered since these can lead to fatigue fractures. This research is expected to improve the knowledge base for the development of trabecular bone analogous materials

The tendency of Nature towards Hexagon Shape Formation due to Minimizing Surface Energy

Nature, for instance, bubble and honeycomb, tend to form a hexagon shape naturally. The array of bubbles and honeycomb is formed by merging and sharing the common wall with the adjacent unit. Even though each of the unit shapes size may vary, the noticeable elements that built up the array are hexagons. There are many regular and irregular shapes available in nature, but the shape formation still leads to hexagon at the end of the shape evolving due to surface tension. Based on the phenomenon, this study was carried out to investigate the effect of surface tension, energy, and geometry features, which affect the tendency of hexagon formation.  The study was carried out by comparing hexagon with triangle, trapezium, and square. From the result, it is found that the reduction of surface energy ranged from 10-23 percent from the initial shape. As expected, the hexagon shape is packed with the lowest surface parameter and very stable in single unit or array form by showing the lowest energy reduction. The energy content is a reflection to structure equilibrium and its stability for nature tendency.   &nbsp

Structure, degradation, drug release and mechanical properties relationships of iron-based drug eluting scaffolds : the effects of PLGA

The effects of poly(lactic‑co‑glycolic acid) (PLGA) on structure, degradation, drug release and mechanical properties relationships of iron-based drug eluting scaffolds have been studied comprehensively. The porous structure of the iron has been incorporated with the curcumin-loaded PLGA (CP) particles through dipping method to produce CP-coated porous Fe (CP-Fe). The CP-Fe degradation has been escalated with the increase of PLGA composition due to the hydrolysis of PLGA. The degradation of iron substrate triggered the kinetics of curcumin release as there was a direct correlation between the curcumin release rate and the degradation rate of the CP-Fe scaffold. The stiffness of the CP particles and the interfacial interactions developed between the CP coating and iron surface have enhanced scaffolds' mechanical strengths. The curcumin released from the scaffold significantly arrested osteosarcoma cells growth. It is demonstrated that the PLGA played an important role to control the scaffold degradation and curcumin release as well as enhancing the mechanical properties of the drug device as an integrated system for favorable scaffold-based drug design

Structure, degradation, drug release and mechanical properties relationships of iron-based drug eluting scaffolds: the effects of PLGA

The effects of poly(lactic‑co‑glycolic acid) (PLGA) on structure, degradation, drug release andmechanical properties relationships of iron-based drug eluting scaffolds have been studied comprehensively. The porous structure of the iron has been incorporated with the curcumin-loaded PLGA (CP) particles through dippingmethod to produce CP-coated porous Fe (CP-Fe). The CP-Fe degradation has been escalated with the increase of PLGA composition due to the hydrolysis of PLGA. The degradation of iron substrate triggered the kinetics of curcumin release as therewas a direct correlation between the curcumin release rate and the degradation rate of the CP-Fe scaffold. The stiffness of the CP particles and the interfacial interactions developed between the CP coating and iron surface have enhanced scaffolds'mechanical strengths. The curcumin released fromthe scaffold significantly arrested osteosarcoma cells growth. It is demonstrated that the PLGA played an important role to control the scaffold degradation and curcumin release aswell as enhancing the mechanical properties of the drug device as an integrated system for favorable scaffold-based drug design

A study of micro-scale solder bump geometric shapes using minimizing energy approach for different solder materials

Demand for more interconnection joints between semiconductor devices can be realized with solder bump technology. Surface tension and density are usually material properties related factors that affect solder bump geometric shape. Therefore, to cope with this fast-changing microarchitecture design in semiconductor technology, a better understanding of the solder bump geometric shape is needed. This study used a static equilibrium force approach to integrate the surface tension and gravitational energy into the solder energy content. Surface Evolver software was used to perform calculations and deliver the final solder bump shape. Perfect agreement with less than 10 % comparison between previous studies and the current Surface Evolver results was found. According to statistical analysis using SPSS, the maximum width of solder shape is closely related to the surface tension. In contrast, the maximum standoff is highly correlated with the solder density. By changing the solder volume, the solder bump changes from standard flip-chip bump to Cu pillar bump with consistency in maximum width to maximum standoff height ratio of 1.5. This study shows that the bumping technology can produce various sizes of solder bumps to meet new electronic packaging requirements

A narrative review of morphology of cancellous bone at different human anatomy- methods and parameters

Morphology of cancellous bone has been studied for years, with researchers always seeking accurate methods to assess the parameters. They also study the importance of cancellous morphology in itself. Despite the amount of previous research, there are currently no reviews on the morphology at different anatomy. This paper evaluate the methods and parameters of cancellous bone morphology at different human anatomy. From 1997 to February 2014 we found the articles published on cancellous bone morphology vary in parameters at different anatomy of human bone. Further, researchers are also interested in finding the precision methods for identifying the parameters of cancellous bone. Both in vitro and in vivo were used in finding the accurate result of cancellous bone parameters whilst also searching the importance of the morphology parameters. The morphology studies are vital due to the direct relation with the mechanical properties of cancellous bone. Based on the morphology data, it is found that the morphology parameters are dissimilar at different human anatomy sites. A variety of methods were used by researchers in identifying the morphology parameters, with each method having its own advantages and disadvantages. This review paper summarises the pros and cons of all methods available, in order to help researchers select the best methods for their future studies

The tendency of Nature towards Hexagon Shape Formation due to Minimizing Surface Energy

Nature, for instance, bubble and honeycomb, tend to form a hexagon shape naturally. The array of bubbles and honeycomb is formed by merging and sharing the common wall with the adjacent unit. Even though each of the unit shapes size may vary, the noticeable elements that built up the array are hexagons. There are many regular and irregular shapes available in nature, but the shape formation still leads to hexagon at the end of the shape evolving due to surface tension. Based on the phenomenon, this study was carried out to investigate the effect of surface tension, energy, and geometry features, which affect the tendency of hexagon formation.  The study was carried out by comparing hexagon with triangle, trapezium, and square. From the result, it is found that the reduction of surface energy ranged from 10-23 percent from the initial shape. As expected, the hexagon shape is packed with the lowest surface parameter and very stable in single unit or array form by showing the lowest energy reduction. The energy content is a reflection to structure equilibrium and its stability for nature tendency.   &nbsp

Effect of Solder Ball Geometry on Solder Joint Reliability under Solder Reflow Cooling Process

Solder joint reliability has become an increasingly important factor in electronic industries to obtain sustainable and reliable electronic packages. The simulation study of 3D finite elements on BGA test assembly models with geometries of SMD-NSMD and NSMD-NSMD is conducted through ABAQUS software and is applied with Anand model equation. The applied loading onto the test assembly is set with reflow cooling temperature of 220 °C to 25 °C. The purpose of this research is to obtain the package warpage, stress, and inelastic equivalent strain throughout the package and solder joints and to develop a predictive finite element model for mechanics and deformation of solder joint in BGA package under reflow cooling. The results obtained showed that solder joints with NSMD-NSMD pad geometry has a greater inelastic equivalent strain and has a greater potential in failing than SMD-NSMD pad geometry. Therefore, it can be concluded that SMD-NSMD pad geometry is more preferable for obtaining a more reliable solder joint

Study the effect of fluid medium toward synthetic cancellous bone structure

During daily activities, trabecular bone need to bear certain amount of load which also leads to movement of the bone marrow within the structure. The flow of the bone marrow within the trabecular bone structure cause the shear stress which affect the nutrient transport, the properties of the bone and also the bone fatigue life. The aim of this paper is to simulate the trabecular structure using FSI approach in order to study the effect of the fluid flow to the structure. In this study, idealized model with 50% of porosity was used in the simulation and 1mm displacement applied on top of the model. Three different types of analysis were used in order to differentiate between CFD, CSM and FSI results. The results showed significant value between these analyses was concluded that FSI approaches is the best to mimic the real body condition