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

Numerical solutions of mixed convection flow past a horizontal circular cylinder with viscous dissipation in viscoelastic nanofluid

The aim of the present study is to investigate numerically the impact of viscous dissipation on steady two-dimensional mixed convection flow past a horizontal circular cylinder in a viscoelastic nanofluid with convective boundary conditions. The Tiwari and Das model were selected in this study by choosing Carboxymethyl cellulose solution (CMC-water) as the base of fluid and copper (Cu) as the nanoparticle. The transformed boundary layer equations for momentum and energy subject to the appropriate boundary conditions were numerically solved by employing numerical scheme, namely Keller-box method. The accuracy of the present results was validated through comparison with previously published results and revealed an excellent agreement with those results. The results were analysed in detail and presented graphically for the velocity, temperature, skin friction coefficient as well as the heat transfer coefficient. The obtained results indicated that there was no significant effect for velocity and temperature profiles when values of Eckert number increased. However, it is significant for skin friction and heat transfer coefficient profiles. In the meantime, thermal conductivity of the fluid may increase by increasing the concentration of nanofluid

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

Addressing the Issues of Maintenance Management in SMEs: Towards Sustainable and Lean Maintenance Approach

This paper outlines on the preliminary outcomes of pilot project aimed at exploring the issue related to managing of maintenance activity in the Malaysian Small and Medium Enterprises (SMEs). SMEs have been accepted as vital components of domestic industry development in many countries. However, the literature portrays that many of Malaysian SMEs particularly the companies involved in manufacturing, fabrication and machining services are struggling to manage the maintenance of their manufacturing equipment. Dependable manufacturing equipment is important factor towards organizational profitability. Managing the maintenance activity of those manufacturing equipment nowadays, is becoming more challenging due to automation and computerization. Due to such issues, SMEs companies are under stiff pressure to minimize lost time for their survival. Thus, this study seeks to explore the related issues towards further improvements. Qualitative research methodology was adopted in the study. Data were collected at eight (8) SMEs located in three (3) different areas, namely southern, central and eastern region of peninsular Malaysia. Information was gathered from semi-structured interviews with SMEs management and observations focuses on different areas of maintenance management at the respective SMEs. The main concern is to validate the critical success factors (CSFs) in managing the maintenance activity at selected SMEs. This study discovered that nine (9) CSFs are having the most significant impact towards improving the maintenance management practice for SMEs. These include: understanding the MM philosophy; management commitment and leadership; maintenance strategy; maintenance planning; maintenance training; monitoring and assessment; appropriate number of maintenance staff; integration of tools, techniques and technology, and; record of maintenance data. All those CSFs construct are integrated in a simple yet self-explanatory MM Framework to convey the conceptual idea of MM implementation program to the management and technical people within SMEs. It is believed that the MM Framework developed would serve as an indicator of company’s MM focus level. Through the identification of the CSFs constructs, the SMEs can utilize the information to improve their approach in systematic MM program. The discovered CSFs are vital for all stakeholders that directly or indirectly involve in managing the maintenance activity in SMEs. Doi: 10.28991/esj-2021-01283 Full Text: PD

Effects of drilling parameters on delamination of kenaf-glass fibre reinforced unsaturated polyester composites

Drilling is a secondary material removal and usually carried out to facilitate fastening of parts together. Drilling of composite materials is not usually a problem-free process. Issues related to delamination composite laminates need to be addressed because it introduces the stress concentration point on the composite. This study focussed on the influence of process parameters such as spindle speed, feed rate, type of drill bits and geometry on the extend of delamination experienced by the composite during the drilling process of kenaf-glass fibre-reinforced unsaturated polyester composite, and the delamination measurements were taken under a microscope. Taguchi methods and analysis of variance were employed to find the optimal parameters. From the results, the most significant parameter was the feed rate. The minimum delamination was achieved when the feed rate was 0.05 mm/rev and spindle speed was 700r/min using both types of drill bits. The quality of the drill hole using the twist drill bit has been proven to be better than the brad drill bit

Crushing behaviour of plain weave composite hexagonal cellular structure

The tradition of fibre composite materials in energy absorbing tube applications has gained interest in structural collisions in the composite materials industry. Thus, the subject of this work is the experimental investigation to understand the effects of the failure initiator at the specimen’s edge, causing the increase in the specific absorbed energy (SEA), as well as the influence of the cellular structure composed of cells with small hexagonal angle exhibited high energy absorption capability. An extensive experimental investigation of an in plane crashing behavior of the composite hexagonal cellular structure between platen has been carried out. The cellular structure composed of hexagonal cells with angles varying between 45 and 60°. The materials used to accomplish the study are the plain weave E-glass fabric as a reinforcement and the epoxy resin system as a matrix. Furthermore, the specific energy absorption increases as the hexagonal angle increases

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

Bariery i wyzwania stojące przed wdrożeniem energii odnawialnej w Libii: przegląd

Given the importance of renewable energy as it provides alternative energy sources over the traditional fossil fuel that is environmentally friendly, clean and renewable, this research aims to explore scholarly articles and books that present and investigate the challenges and barriers facing the implementation of renewable energy sources in Libya where the social, cultural, financial and awareness aspects are an important consideration against renewable energy. This study contains a review of all relevant, peer-reviewed, and published articles from journals, websites, books, conference proceedings and bulletins. An extensive literature review was carried out with the aim of researching renewable energy in Libya. This was done to take a realistic perspective of the community and the knowledge services accessible. The review of literature has shown that further renewables energy research remains necessary as the current conditions of the energy sector in Libya need to be examined to understand the challenges and difficulties to introduce renewable energy within competent authorities and businesses are examined in accordance with their managers. This indicates the need to conduct various studies in Libya to explore the various challenges, mostly financial and technological, that face the purposeful implementation of renewable energy resources in Libya. Additionally, the level of awareness and culture perception of the use of renewable energy is an important aspect to be considered as reported as barriers affecting the implementation of renewable energy in various parts of the world.Biorąc pod uwagę znaczenie energii odnawialnej, zapewniającej alternatywną energię w stosunku do tradycyjnych paliw kopalnych, która jest przyjazna dla środowiska, czysta i odnawialna, niniejsze badanie ma na celu przegląd artykułów naukowych i książek, które przedstawiają i badają wyzwania i bariery stojące przed wdrożeniem odnawialnych źródeł energii w Libii, gdzie aspekty społeczne, kulturowe, finansowe i świadomościowe są ważnymi czynnikami, które nie sprzyjają energii odnawialnej. Niniejszy artykuł obejmuje przegląd wszystkich istotnych, recenzowanych i opublikowanych artykułów z czasopism, stron internetowych, książek, materiałów konferencyjnych i biuletynów. Obszerny przegląd literaturowy ma na celu zbadanie statusu energii odnawialnej w Libii. Takie spojrzenie pozwala uzyskać realistyczny pogląd na ocenę zagadnienia przez społeczeństwo oraz na dostępne w tym zakresie usługi. Wykazano, że niezbędne są dalsze badania w zakresie energii odnawialnej. Aby zrozumieć wyzwania i trudności we wdrażaniu odnawialnych źródeł energii, jakie stoją przed właściwymi organami, przedsiębiorstwami i ich kierownictwem, trzeba szerzej zapoznać się z warunkami funkcjonowania sektora energetycznego w Libii. Wskazuje to na potrzebę przeprowadzenia różnych analiz w celu zbadania wyzwań, głównie finansowych i technologicznych, utrudniających wdrażanie użytkowania energii odnawialnej w Libii. Ponadto, poziom świadomości i kulturowego postrzegania wykorzystania energii odnawialnej są ważnymi uwarunkowaniami, które należy uznać za bariery mające wpływ na wdrażanie energii odnawialnej w różnych częściach świata także w Libii