International Journal of Engineering Research in Africa Vol. 42

Abstract: A fatigue damage accumulation model for composite materials is proposed. There is unanimity on the complex nature of the mechanisms of damage inherent to these types of materials. This led to proposals for nonlinear models, but relatively expensive in experimental requirements and determination of parameters. Thus, the proposed model is simple and does not require parameters apart the ultimate strength and the fatigue curve. A program is developed to allow the follow-up of the damage evolution during the cycles of loading. The proposed model is applied to E-Glass/Epoxy [0°/90°] under two blocks loading. Prediction results are relatively good and fit well with the experimental results compared to similar models.

Abstract: This paper presents results from modeling of Compressor Turbine (CT) blades for short-haul aircraft fleet occasioned by thermo-mechanical stresses in order to comprehend the occurrence of premature failure. A 3D PT6A-114A engine high pressure (HP) CT blade geometrical model was developed in commercial CAD-SolidWorks, then imported to ANSYS 15.0 environment for finite element analysis (FEA). The CT blade was investigated for transient thermal stresses from heat generated by the combustors and static structural stresses from rotational velocities of the engine which account for 80% of inertial field during flight. The results revealed that the blades could have served for another 1.44% of the time they were in service.

Abstract: This paper presents the results of experimental research to investigate blade material surface deterioration of wind turbines located in arid areas caused by sand particles impacts and the resulting influence on their energetic performance. Tests are conducted in the erosion sandblaster then in the wind tunnel for uncoated Glass Fiber/Polyester blade at various angles and durations impact. The magnitudes of aerodynamics forces on a Naca 4412 profile are determined experimentally. All profiles (AR=0.571) are tested in a wind tunnel at air speed of 10 m/s at Reynolds number 6.5 x 10⁵. The results show the behavioral differences detected for the specimens with T =160 s, T = 240 s and T = 340 s (when Ra increases) by comparing them with the smooth specimen (T = 0 s, Ra= 0.94). Force coefficients (C_L and C_D) show significant changes which leads to a decrease of the lift-to-drag ratio and therefore there will be a notable performance loss. This will be an acceptable threshold for the case where t = 160s.

Abstract: Ground vibrations are commonly observed by using a standard seismic station equipped with speed seismometers or acceleration seismometers. The seismometers include three mechanical vibrating systems (sensors) and the primary output is the wave pattern of recording velocity or acceleration of the material point oscillation. An alternative new method how it is possible to realize seismic measurements is using of the fiber-optic interferometric sensors. These interferometers are well-known for their ability to make high-precision measurements of optical path difference or changes that may be induced by a refractive index change in the interferometer or a physical displacement. The paper presents a comparison of the results of the standard seismic measurement by using seismic station and of the fiber-optic interferometric sensor. As a source of dynamic load, truck transport was chosen. When trucks passing through unevenness on the road (due to the road damage, the transition area of the bridge etc.), it generates vibrations that are transmitted to the subsoil and can adversely affect the surrounding building objects. Data comparison of the subsoil dynamic response obtained during both approaches of measurements is present in the amplitude and primary in the frequency domain.

Abstract: The need for quality control of biodiesel is important to ensure the development of a clean, trouble free and safe alternative fuel technology to fossil diesel. In this work, the gas chromatography analysis of the biodiesel produced from used frying oil was carried out using PerkinElmer Clarus 500 Gas Chromatograph (GC), fitted with a capillary split injector and Fourier Infrared Detector (FID). Also, the Fourier Transform Infrared Spectroscopy was used to determine and monitor the concentration of biodiesel produced from used and unused palm olein oil. The Fourier Transform Infrared (FTIR) analysis was carried out using the FTIR Spectroscopy (FTIR 1-S Shimadzu, Japan, Model 4100) and Microlab software as well as Attenuated Total Reflectance (ATR) sample interface system. 0.5 ml of samples of the unused palm olein oil and biodiesel were taken in at the interface at a resolution of 4 cm^-1 within the region of 4000 cm^-1 to 400 cm^{-1 .} The GC-MS analysis did not indicate any soap-like material, indicating that the catalyst was able to handle transesterification reaction without transition to saponification reaction. The results of the interaction between the components of the fuel samples and the radiation as a function of wavelength indicates the functional groups and the type of vibration in the fuel samples. The results obtained indicate the presence of an intense band of C=O stretching of methyl ester and O-CH₃ group. It also show concentration of the five main fatty acids that are present in most biodiesel; palmitic, stearic, oleic, linoleic, and linolenic acids indicating the successful transesterification of palm olein oil to biodiesel.

Abstract: This study considered the production of composite ceiling boards from both agricultural and industrial wastes. Boards with different blending proportions by weight of cement, corncob and sawdust (Cem:Ccb:Swd) were produced and tested. Physical and mechanical tests such as Water Absorption (WA), Thickness Swelling (TS), Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) were carried out on the products. The findings revealed that the board with Cem:Ccb:Swd blending proportion 50:10:40 gave the highest values of MOE and MOR and also had the lowest values of WA and TS. The MOE and MOR values of 3.432 are both higher than the minimum values of 550 N/mm² and 3 N/mm² specified for MOE and MOR respectively by the American National Standard Institute, for general-use particle boards. The cement content is inversely proportional to the physical properties and directly proportional to the mechanical properties.

Abstract: This paper presents an experimental study to evaluate the influence of the water addition and pre-saturation of recycled aggregates (RA) on rheological and mechanicals properties of concrete. Quantities of water absorbed and their variations in times were measured according to the European standard (EN 1097-6). Two methods were tested: pre-saturate the aggregates and add them to other parameters making concrete or add water absorbed quantity to the mixing water. Replacement rate of natural aggregates (NA) 0%, 50% and 100% were studied. The results obtained showed that the gravels class 3/8 have a greater absorption capacity than the gravels class 8/16. Adding absorbed water during mixing have caused concretes segregations and an excess volume of water was observed at the surface of the concrete. The added water was not totally absorbed by aggregates. The pre-saturation of aggregates 24 hours before mixing and introducing them as a component in concrete was the best method. The initially saturated aggregates did not consume concretes mixture water. Workability by slump test and mechanical strengths developed with pre-saturated aggregates (100 % RA) and (50% RA - 50% NA) were measured on concretes, and then were compared to those of the reference concretes made with 100 % of natural aggregates.

Abstract: The new requirements for strength and durability have led to the development of Ultra High Performance concrete (UHPC) with outstanding mechanical properties and durability. However, the application of this type of concrete is exceptional, because of the high dosage of cement and the incorporation of expensive materials, such as silica fume (SF) whose dosage can reach 30% by weight of cement. This type of concrete is formulated on two bases: A fine granular skeleton (max diameter 630μm) and high cementitious materials content. The search for local materials to exploit them in the formulation of UHPC is the current trend. It is therefore necessary to control their effect on the behavior and evolution of cement hydration.The objective of this study is to highlight the influence of blast furnace (BFS) on hydration kinetics, linear endogenous shrinkage and chemical shrinkage at very early age (before 72h), drying shrinkage after hardening, as well as, the evolution of mechanical compressive strengths as a function of time. In addition, the exploitation of dune sand in the granular skeleton is an alternative to reduce the crushing energy and avoid microcracks possibly induced.The analysis of the results showed the interest of the use of the dune sand and the partial substitution of the cement by the BFS on the properties of the UHPCs in the fresh state and in the hardened state.In addition to the high performance achieved by UHPCs, their use, in Algeria, will meet both economic and ecological requirements given the abundance of very fine dune sand (southern Algeria) and complex blast furnace BFS of EL-Hadjar (Eastern Algeria).

Abstract: This work is carried out to investigate the performance of concrete reinforced with plastic fibers obtained locally (bottle waste as fiber). Bottle waste plastic was chosen because it is being thrown after single use and cause environmental problem. One way to recycle wasted bottles plastic is grinded into irregular fiber. Then, it was incorporate with the concrete and tests the performance of the concrete. The study was conducted using cylindrical and rectangular (cube) mold of concrete to investigate the performance of the concrete in term of mechanical properties. In this research, the mechanical properties that were measured are compressive strength, splitting tensile strength and flexural strength. The results revealed that the presence of plastic fiber in concrete will increase the concrete performance, as well as the concrete bond strength is improved and the cracks in the concrete decrease the use of fibers and reduce plastic waste.

Abstract: Earthquakes are part of the natural cataclysms that are responsible for the destruction of entire cities, causing the deaths of millions of people and often have disastrous economic consequences. Therefore, it is important to consider measures of the intensity of seismic movement in risk analysis (Potential Earthquake Harmfulness ‘PEH’). The purpose of this study is to model the mass of soil under a rockfill embankment in order to evaluate the soil settlement under the effect of an earthquake of Boumerdes (Algeria 2003) using “plaxis” finite element code. The PEH characterizes in our study the Aria intensity IA(t) and the cumulative absolute velocity CAV(t), on the one hand, and on the other hand, empirical correlations between the indicators of harmfulness (PEH) and the settlements under the base of the dike. The correlations thus obtained (Uy-PEH) are slightly influenced by the gravitational loads and a tighter dispersion of the point cloud is observed on the correlations (Uy-IA).