IMPROVEMENT OF TECHNICAL EDUCATION IN PUBLIC TECHNICAL SECONDARY SCHOOLS (ECOLE TECHNIQUE OFFICIEL - ETOS) IN RWANDA

This paper presents a brief review of the state of technical education in Rwanda based on a study conducted in 2007, with pertinent recommendations. The background of technical education in the country is appreciated first, and then followed up with a situational analysis. Thereafter, a 5-year implementation project plan proposal, to address the identified shortcomings, needs, and expectations of government is advanced. The need to raise access to post tronc commun (post O-Level) technical training is addressed within this proposal with a specific interest to increase the capacity and range of programmes running in the existing ETOs, and the introduction of new ETOs where deemed necessary. The establishment and sustenance of a good quality technical education system is also given consideration in this proposal for effective and efficient rehabilitation of existing physical facilities and the purchase of new and appropriate training equipment. Simultaneously, considerations for increasing the number of technical teachers in the system to a determined optimum level while setting minimum acceptable qualifications for technical teachers are advanced. Implementation of this proposal is expected to contribute greatly to the continuous development of a labour pool with skills that are relevant to and adequate for the needs of the economy

PROPOSED INTERVENTIONS FOR THE TECHNICAL INDUSTRIAL AND VOCATIONAL ENTERPRISE TRAINING (TIVET) SECTOR IN KENYA

This paper presents a brief overview of TIVET in Kenya (history and present), the laws governing TIVET, and its structure and challenges today. A robust review of various relevant concepts that are in use in TVET is presented and solutions to identified shortcomings of the Kenyan TIVET system proposed. The Develop a Curriculum, (DACUM) and the Systematic Curriculum and Instructional Development (SCID) methods of developing demand led and competency based occupational profiles and arising curricula are recommended for adoption in the country’s TIVET system. It is further recommended that On-Job-Training is introduced in addition to the creation of strong linkages with industry in order to increase relevance to and absorption of TIVET graduates in industry. The paper touches on the issues of specification and sourcing of equipment and identifies possible source markets. More study is recommended in order to obtain a complete and comprehensive assessment of TIVET in the country

Mixing And Reuse Of Polymer Laser Sintering Powders To Ensure Homogeneity - A Review

ArticleSelective laser sintering is one of the most common additive manufacturing technologies for polymeric materials. However, the technique is limited due to the high cost of the few available feedstock materials. Besides, laser sintering is a high-temperature process, which subjects polymeric materials to thermal stresses, resulting in the degeneration of powder. Besides, only a small portion of the powder fed into the built chamber is used in the printing of components. Hence, the need to recycle the used polymeric powder. This is achieved by mixing used and virgin powder in the ratios stipulated by the manufacturers of the powders. This review investigates the types of powder, types of mixing mechanism, parameters that affect efficient mixing, the homogeneity of mixed powder, mechanisms of segregation, and selection of the most appropriate mixers in the context of selective laser sintering of polymeric materials

The Tensile and Flexural Properties of Treated and Untreated Sisal Fibre-Epoxy Resin Composites

Published ArticleThe influence of chemical treatment of sisal fibres through the subsequent processes of mercerisation (alkali treatment), then silane treatment and eventually acid hydrolysis on the fibres were investigated. The effect of the treated fibres on the tensile and flexural properties of their composites with epoxy resin were also studied. Scanning electron microscopy examination of the treated and untreated fibres showed that the subsequent processes of chemical treatment enhanced the removal of surface impurities and therefore increased the roughness of the fibre surfaces. It was concluded that this would avail an increased surface area on the fibre for interlocking with matrices and would therefore enhance adhesion of the two. Consistent to this conclusion, subsequent testing of treated fibre reinforced composites gave rise to higher values of tensile and flexural strength and toughness than the untreated fibre reinforced composites

Crystallographic Texture Analysis of As-Built and Heat-Treated Ti6Al4V (ELI) Produced by Direct Metal Laser Sintering

ArticleThis paper reports on an investigation of crystallographic texture of as-built and heat-treated Ti6Al4V (ELI) produced by direct metal laser sintering (DMLS). The texture analyses were conducted using electron backscatter di raction (EBSD). The -phase texture from the obtained EBSD data was ascertained based on a reconstruction method using the Automatic Reconstruction of Parent Grain for EBSD data (ARPGE) program. A significant improvement of the maximum intensity of the texture from the pole figure was also noted upon heat treatment. The as-built samples and samples heat-treated just below the ! transformation temperature showed a stronger fibrous texture of the reconstructed -grains with the h100i directions almost parallel to the build direction. The alignment of the fibrous texture in the build direction disappeared after heat treatment above the ! -grain transformation temperature

Powder Characterization for a New Selective Laser Sintering Polypropylene Material (Laser PP CP 60) after Single Print Cycle Degradation

ArticleExperiments were conducted to characterise a new polymeric powder (Laser PP CP 60) from Diamond Plastics GmbH used in selective laser sintering (SLS) additive manufacturing (AM). Three different batches of the powder were tested in the study; virgin powder, used powder, and a mixture (50% virgin: 50% used) powder. The three batches of powder were subjected to scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and melt flow index (MFI) testing. Scanning electron microscopy was used to determine the morphology of particles. The distribution of powder particle sizes was established by analysing the acquired SEM images using ImageJ software. Differential scanning calorimetry was used to determine the peak melting point, degree of crystallisation, and the sintering window of the powder. Thermogravimetric analysis was utilised to determine temperatures of degradation of the powder considered in the study. Lastly, MFI testing was used to determine the variation of flowability of the powder. It was found that the three batches of powder considered showed poor, but allowable morphology and particle size distribution. The sintering window of the virgin Laser PP CP 60 polypropylene powder increased after a single cycle of printing by 28%, from 21.04℃ (virgin powder) to 26.95℃ (used powder). The sintering window was lower than that for polyamide polymer, which might have contributed to the high shrinkage rates observed during processing of the material, as a narrow sintering window results in difficulties of regulating the cooling rate of the printed parts. The three batches of powder showed high degradation temperatures, which makes the material suitable for SLS processing. Finally, the three batches of powder showed low values of MFI, which indicates that the molten material has a high viscosity. This explains the difficulties experienced in processing the material

Effect of Stress-Relieving Heat Treatment on the High Strain Rate Dynamic Compressive Properties of Additively Manufactured Ti6Al4V (ELI)

ArticleA study was undertaken on the compressive high strain rate properties and deformation behaviour of Direct Metal Laser-Sintered (DMLS) Ti6Al4V (ELI) parts in two separate forms: as-built (AB) and stress relieved (SR). The high strain rate compression tests were carried out using a Split Hopkinson Pressure Bar test system at ambient temperature. The average plastic strain rates attained by the system were 400 s1 and 700 s1. Comparative analyses of the performance (flow stresses and fracture strains) of AB and SR specimens were carried out based on the results obtained at these two plastic strain rates. Microstructural analyses were performed to study the failure mechanisms of the deformed specimens and fracture surfaces. Vickers microhardness test values were obtained before and after high strain rate compression testing. The results obtained in both cases showed the strain rate sensitivity of the stress-relieved samples to be higher in comparison to those of as-built ones, at the same value of true strain

Effects of Stress-Relieving Heat Treatment on Impact Toughness of Direct Metal Laser Sintering (DMLS)-Produced Ti6Al4V (ELI) Parts

Published ArticleThe impact toughness of as-built (AB) and stressed-relieved (SR) direct metal laser sintering-produced Ti6Al4V (ELI) was investigated using the standard Charpy impact test over the temperature range of 130 C to 250 C. Stressrelieving heat treatment was conducted at 650 C for a soaking period of 3 h in argon gas atmosphere. The results showed improvements in the impact toughness after stress-relieving heat treatment. Stress relieving also shifted the established ductile-to-brittle transition temperature to lower temperatures. Comparative analysis of the impact toughness values for AB and SR specimens at ambient temperature showed them to be 48% and 22% lower than recommended values for use in aircraft structures, respectively

A Review Of The State Of Research And Utilization Of Biomaterials In The Manufacture Of Composite Materials Todate

ArticleOver the last four decades composite materials, plastics and ceramics have been the dominant emerging materials. The volume and number of applications of composite materials has grown steadily, penetrating and gaining acceptance in new markets. Modern composite materials constitute a significant proportion of the engineered materials market, ranging from everyday products to sophisticated niche applications. While composites have already proven their worth as weight saving materials, the current challenge is to make them cost effective. This paper presents review on the worldwide state of research of biomaterials and their utilization in the manufacture of composite materials

Dimensioning of dog bone specimens and numerical analysis of the effects of different fillet radii, clamp area and pinhole loading on the stresses in such specimens

The effects of different fillet radii, clamp area dimensions, and pinhole loading through a hole located in the clamp area of a dog bone specimen were investigated using the Finite Element Analysis (FEA) software Abaqus. Changes in the fillet radius were shown to have little effect on the distribution and magnitude of the von Mises stresses. Different dimensions of the clamp section gave different von Mises stress distributions within the clamp section, with the maximum values remaining within the gauge section, thus implying that limitations of available cutters and material could be accommodated by varying the dimensions of test specimens. Introduction of pinhole loading in order to minimise torsion, led to a shift of the maximum von Mises stress from the gauge section to the edge of the pinhole, an indication that the benefits of minimising torsion required to be weighed carefully. The observed shift was only significant however, for failure load levels and for cyclic loading. A set percentage change rather than the absolute convergence of the von Mises stresses was shown to be a more economical way of arriving at an optimal mesh density, a characteristic that was seen to vary from one location to another. African Journal of Science and Technology Vol. 5(2) 2004: 60-7