International Journal of Engineering Research in Africa Vol. 17

Abstract: This article employs Relevance Vector Machine (RVM) for prediction of two fracture parameters {Critical Stress Intensity Factorand Critical Crack Tip Opening Displacement (CTOD_c)} of concrete. Input variables of the RVM model are water-cement ratio (), maximum size of aggregate () and characteristic strength (). The developed RVM gives equations for prediction of and CTOD_c. A comparative study has been presented between the developed RVM and the ANN models. A sensitivity analysis has been done to determine the effect of each input parameter on the predicted and CTOD_c. This article shows that the developed RVM can be used as an efficient tool for determination of and CTOD_c.

Abstract: In this present work a response surface optimization was done to study the effect of the variables curing days, Multi-Walled Carbon Nanotube (MWCNT) and plasticizer on the strength of concrete. The variables were varied in three levels and a total of 15 cylindrical specimens were fabricated based on the experimental design. For measuring the effect of the variables, split tensile strength test was carried out on the specimens. For proper mixing of the MWCNT, sonication is carried out with plasticizer and then this mixture is added with water and the specimens are fabricated. Only the terms with p < 0.05 are chosen as significant. The results shows that an increase in MWCNT %, increased the split tensile strength of the concrete.

Abstract: The use of waste materials is one of the options for sustainable construction. In this paper the coconut shell waste is considered as coarse aggregate (after the same has been crushed) for preparing light weight concrete. The natural material like bamboo which is having considerable tensile strength is considered for reinforcement along with coconut shell concrete. Since the bamboo may absorb moisture from the concrete, to find its effect, the bamboo is treated with water repellent substance like epoxy adhesive is considered. Four types of short columns are tested. Type A Conventional concrete with steel reinforcement, Type B Coconut Shell concrete with steel reinforcement, Type C Coconut Shell concrete with treated bamboo reinforcement, Type D Coconut Shell concrete with untreated bamboo reinforcement. The conclusions drawn from the study are the load carrying capacity of Type B column is 89% of Type A column. For Type D column the ultimate load is 90% of Type C column. For Type C column the ultimate load is 70% of Type A column. For Type D column the ultimate load is 63 % of Type A column. For Type A column the stiffness is higher than the stiffness of Type B, Type C and Type D column. The energy absorption capacity of Type A, Type B columns are higher than that Type C and Type D columns. The epoxy treatment of bamboo has improved the ultimate load capacity by 1.1 times of the Type D column.

Abstract: Experimental data obtained from full-scale experiments determines the stiffness of wedge connected of scaffold.A finite element model is developed using semi-rigid scaffold node mode.And a reasonable combination of longitudinal span,transverse span and step distance is obtained.The results accords with the relevant standard of vertical load.It provides a theoretical support for the application of wedge connected scaffold.Additionally,the study explores the safety height of the wedge connected scaffold with or without bridging.It provides a theoretical basis for technical regulations.

Abstract: With the development of world’s economy, energy shortage gradually appears. Resistance has a great influence on energy consumption. In other words, drag reduction means saving energy. Development of the drag reduction technology plays a very important role to improve the energy efficiency. Therefore, drag reduction technology of jet has become a hot research field. Drag reduction technology of jet is applied on the surface, so as to reduce surface friction resistance. Through analyzing the necessity of energy efficiency increase and jet drag reduction theory improvement, research progress of lateral jet flow technology and drag reduction technology of jet in the field of aircraft are reviewed. Besides, a main trend on the drag reduction technology of jet research is presented.

Abstract: Plates are one of the most important structural components used in many industries like aerospace, marine and various other engineering fields and thus motivate designers and engineers to study the vibrational characteristics of these structures. A lot of research work and studies have been done to study its vibration characteristics. This paper is a review of existing literature on vibration analysis of plates. Focus has been kept on prominent studies related to isotropic plates based on Mindlin plate theory; however few citations on orthotropic plates and higher order shear deformation theories have also been included. All citations are in English language. This review is aimed to provide contemporarily relevant survey of papers on vibrational characteristics of thick plates and identification of various methods and approaches that have been used to study the vibration characteristics. This paper will not only be useful for scientists, designers and researchers to locate important and relevant literature/research quickly but will also help them to identify and apply some of these methods and approaches to study the vibration characteristics of various other 2D and 3D structures.

Abstract: In orthopaedic surgery and particularly in the total hip arthroplasty, the stem fixation is performed in general using a surgical cement which consists essentially of polymer polymethyl-methacrylate (PMMA). During polymerisation of PMMA, residual stresses caused by volumetric and thermal shrinkage (exothermic reaction) are generated in the bulk cement. In this study, the three-dimensional finite element method is used to analyze the distribution stresses in the bone cement. Linear elastic analysis is adapted; von Mises, normal and shear stresses are the criterions that are of concern. The results showed that the inclusion of the residual stresses at the interface stem–cement increase the von Mises and the normal stresses in the different sides of the cement compared to the case without residual stresses.

Abstract: Dimensional metrology plays an important role in the modern manufacturing technology. Accurate machining technology remains the main focus of global industry, where needs to permanent study for the purpose of improving. Coordinate metrology is an important inspection tool of dimension and geometrical surface form for machined work-piece to provide functionality in quality process. Several factors affect the accuracy and quality of manufactured parts when machined using circular pocket cycles on CNC machining centers. Such accuracy depends to a great extent on work-piece material, the cutting conditions; namely spindle speed, feed rate, depth of cut and the structure of the fixed cycle. The accuracy of dimensional and geometrical form plays a vital function on the required tolerance and fit of manufactured parts to be assembled.This paper studies the influence of those parameters on the accuracy and quality of milled pocket diameter with its roundness. Several specimens made of aluminum, copper and steel metals were pocket milled on a CNC using different cutting conditions. CMM was used to assess the errors in diameter and roundness measurements of machined parts. In despite of scientific advances in machining technology, however there are still clear deviations in the measurement results according to choice of the cutting condition, especially when change the type of work-piece material. Monitoring suitable validiation method for a typical manufacturing machining is achieved accurately. Moreover, expanded uncertainty in measurement has been estimated using statistical repeatability analysis and most effective experimental parameters.

Abstract: The presence of Robots in all engineering industries and commercial applications is tremendously growing day by day. Considering this there is a need to implement the robotic principles, which cannot be applicable to the human beings directly. One of the essential areas that lead to complications is maintenance and inspection of large vertical structures with autonomous systems; still it is an unsolved problem for the people doing research on this area. It is a challenge for mobile robots to climb a vertical wall primarily due to requirements for reliable locomotion, high maneuverability, and robust and efficient attachment and detachment. A large number of different robots exist which are able to navigate on buildings, ship hulls or other human-made structures, but most of these systems are practically limited to special situations or applications. It may be due to the design or physical factor that has been considered during the design of robotic system. While considering these issues a lot of researches state various principles and design aspects for maintenance and inspection purposes. Based on these facts, this article discusses the different methods for climbing robots and points out specifically the recent adhesion method for concrete vertical wall climbing. It also discusses about the design characteristics, practical challenges against the execution on vertical structures and suitable valid fields.

Abstract: The continuous desire to drift from the conventional sources of energy to renewable energy resources is stymied by the intermittent nature of some of renewable sources such as solar and wind. However, analyses on some of the required conditions in which intermittent energy resources will be attractive and when it will be less attractive are presented in this paper.Pearson’s product moment of correlation coefficient (r) technique was used to calculate to calculate the correlation coefficient with respect to how three distinct hourly load profiles relate to the available solar radiation. The three calculated r values were analysed and applied as the operating strategies for modelling the power system in RETScreen softwareThe results from the three strategies employed show that the positive r value strategy was the most viable option and it can compete with the diesel only system.Therefore, for a distributed power generation system that utilizes an intermittent energy source, the relationship between the intermittent source and the load profile should be considered as an important indicator for determining the feasibility of the project.