Advanced Engineering Forum Vol. 32

Abstract: The geometric nonlinearity resulting from large deformation of compliant members has continued to be an interesting research topic in nonlinear mechanics. In this study, two standard variational iteration algorithms, VIM-I and VIM-III are employed to investigate the large deformation of the continuum compliant beam under point load. The VIM is an efficient technique that bypasses the linearization process and proffers solutions to nonlinear problems. The horizontal and vertical displacements of the continuum compliant cantilever beam free end are expressed in explicit analytical forms. Numerical experiment and simulations were carried out to validate the efficacy and applicability of the semi-analytical method. The VIM-I was split into two; VIM-I(A) and VIM-I(B), with the difference being the initial approximations. The results from the VIM-I(A), VIM-I(B) and VIM-III algorithms were compared with the experimental and exact solution. The outcomes reveal that both algorithms correlated well with the analytical solution and experimental result.

Abstract: Gas turbines are very important because they can be used in several areas, such as aeronautics and electric power generation systems. The operation of a gas turbine can be done by less pollutant fuels when compared to traditional kerosene, for example, resulting in less degradation to environment. Gas turbines may fail from a variety of sources, with the possibility of serious damage results. In this work, the structural integrity of the hot disc of an aeronautical gas turbine is addressed. Several numerical analyses have been performed by the finite element method: Temperature Distributions, Thermal Stresses and Dilatations, Structural Stresses and Deformations, Modal Behaviors and Fatigue Analysis. Creep of blades has also been considered. These are the most important failure modes that can happen to the studied hot disc under operating service. All these analysis have been performed considering the boundary conditions at the design point with maximum rotational speed. The mesh of the problem has been strictly evaluated by adaptive refinement of nodes and elements combined with a convergence analysis of results. Then, the material and basic properties of the hot disc have been defined to assure a normal operation free from failures. Therefore, the mechanical drawings of the studied hot turbine disc have been released for manufacturing and the construction of the first prototype of the aeronautical gas turbine is in testing phase showing that the results presented in this work are consistent.

Abstract: The structure of the skull reveals that the cranial is made up of a number of bones. These bones, except the temporomandibular joint, are joined by sutures. The adjacent bones are strongly united by a matrix of connective tissues consisting of bundles of strong collagenous fibres connecting periosteum to the bones. The little movement at the sutures contributes to the elasticity and compliance of the cranial. This composition serves as a shock absorber and distributes impact force evenly around the skull. Frequent head impacts by footballers cause concussion which leads to brain and neurological disorders such as; Traumatic Brain Injury (TBI), dementia, depression, and a loss of attention span. These disorders are primarily caused by shock waves following impact, which moves from the front to the back of the brain. As such, the effort is geared at reducing head injuries from concussion by optimising helmet design through shock absorption increase and stress amplification reduction during impact. In this paper, the suture structure is mimicked in the design of a football helmet. A fibre-reinforced composite liner is introduced in the shell of the helmet. The liner runs from the front to the back of the helmet and bisects the shell into two equal parts. Hyperelastic material model is employed in the modelling of the composite liner while the polycarbonate helmet shell is modelled as a nonlinear elastoplastic material. A finite element model based on realistic geometric features of a football helmet was carried out, and an explicit finite element code LS-DYNA® is employed to simulate dynamic responses at different impact velocities of the helmet. The simulation was repeated for various compositions of the composite liner. Impact loads are applied on one side of the helmet shell while the responses are taken on the other side of the shell body of the helmet. To establish the validity of the model, the liner, and the shell materials are made to be the same. The results revealed that the responses of the helmet during impact are the same when the two components are of the same material compared with when there is no liner on the helmet shell. It was also shown that the dynamic response curve of the helmet emanating from different impacting conditions is judged by the maximum principal stress, Von Mises stress, and acceleration monitored within the impact period. The helmet composition with a sinusoidal liner form on the shell absorbed more impact load than other liner configurations.

Abstract: The growing demand for energy efficiency gains in vehicles has led to several advances in more technological and efficient driving units, projects using lighter and more resistant materials and, in particular, a deeper study of aerodynamic studies in order to understand the fluid flow around the object of study. This work presents an aerodynamic study for a vehicle of high-energy efficiency, through computational fluid dynamics simulation in Ansys Fluent software. The main objective is to obtain the traction and drag force vectors acting on the vehicle at different speeds and to better understand the airflow before, during and after contact with the vehicle. With the possession of results, it was facilitated the implementation of improvements that enabled the vehicle to operate even more efficiently.

Abstract: Concrete is today the most widely used building material in the world; it has experienced a real boom in its association with steel in reinforced concrete. The mechanical and chemical complementarity between these two materials has made it possible to build economically and reliably the structures required for all human activities, hence sustainability becomes both a requirement and a major concern of manufacturers. It is therefore essential that the functions of the reinforced concrete are not reduced and that its properties are not altered. However, it is a reactive and a porous material able to the physical and chemical degradations in contact with its environment, due to a chemical reaction between these two media.In this work, we are interested in characterizing and monitoring the ions chloride penetration in reinforced concrete. For this purpose, specimens of the reinforced slab type are made with a composition standardized according to the DREUX-Gorisse method, and we have followed the concrete’ mechanical characteristics evolution in parallel with the immersion / drying cycles’ slab in the sea water. This development was followed with an ultrasound device for a period of about thirty two (32) months. After this period, the reinforcements’ electrochemical behavior by cyclic voltammetry, in these slabs was studied in order to determine the corrosion rate.The results indicated that there is a relationship between the concrete’ strength and the state of its reinforcements with the surrounding environment. On the other hand, the coating thickness is a fundamental parameter of the reinforced concrete durability which makes it possible to lengthen the corrosion initiation.

Abstract: Sawmill activities are characterized with different degrees of injuries and accidents due to indecorous handling of sawmill machineries, lack of necessary accident prevention facilities, skill, poor safety culture and practices. However, to guarantee safety in this kind of environment, it is highly imperative that the industry adopt and implement a range of effective occupational health and safety management measures in an efficient way that will lead to more favorable and safe environment for all stakeholders. The safety of stakeholders and facilities however necessitated this work. Two major sawmills were considered in two main towns or cities in each of the six southwestern states of Nigeria, namely: Ekiti, Lagos, Ogun, Ondo, Osun and Oyo States, which formed part of the major wood producing rain forest areas in Nigeria. Some of the accidents causing activities identified were: human, deficiency in maintenance, environmental and Lack of Personal Protective Equipment (PPE) among others. Sawmill safety activities were classified as training, (PPE), safety awareness creation, accident investigation, motivation/incentives, machine/tools procurement and security/safety enforcement. Sixteen safety strategies were developed using combinatorial method with training, PPE and motivation/incentives as compulsory activities. System dynamics software (Vensim 7.2) was then used to delineate the causal and flow diagrams. A system dynamic model was developed as valuable leading tool for effective safety planning and management in sawmill industry.

Abstract: Mobile subscribers’ satisfaction constitute a critical success factor among competitors in the telecommunication industry. The dynamics of this phenomenon in the University of Port Harcourt has given rise to an ambivalence of subscribers’ milieu of choices; with them acquiring multiple simcards on one hand, and choosing a single simcard on the other. Either way, their quest for satisfaction appear to be a wild-goose chase. Consequently, this paper examined the determinants of mobile subscribers’ satisfaction vis-à-vis the University of Port Harcourt. Based on a common parlance definition of these determinants, derived through descriptive research, six variables were identified and tested as dependent variables of mobile subscribers’ satisfaction. For the purpose of this study, a sample size of two-hundred (200) respondents was selected from Choba and Abuja campuses of the University of Port Harcourt through random sampling technique, and data were obtained using a Structured Likert Scale questionnaire where respondents tick (√) either in negation or affirmation of the item. The results revealed four of the variables as having a positive correlation with mobile subscribers’ satisfaction while two recorded a negative correlation. An outcome which gives credence to ‘prompt and affordable connectivity’; ‘24 hours affordable internet connectivity’; worldwide connectivity spectrum’ and ‘proliferation of freebies outlets’ as determinants of ‘mobile subscribers satisfaction’. At the same time, the study makes a mute point of the often touted allusions of an existing nexus between mobile subscribers satisfaction and a telecommunication service provider’s ‘toasted brand name-cum-indigenous outfit patronization syndrome’ .In the main, the work constitutes an added voice to the call for a pro-active regulatory body that would irrespective of the service provider a subscriber patronizes be able to ensure that mobile subscribers are always provided with an equally affordable, hitch-free connectivity that smacks of uniformity of service.