Laboratory Investigation on the Effect of Microsilica Additive on the Mechanical Behavior of Deep Soil Mixing Columns in Saline Dry Sand

Since loose and salty subgrades consider as problematic barriers while constructing new transportation infrastructures such as railway tracks and roads are required, the current study aims to find a solution to stabilize these kinds of subgrades using the deep soil mixing (DSM) technique and micro silica additive. In the present study a series of experimental DSM columns were executed in a salty sand-filled chamber utilizing a laboratory scale DSM apparatuses. In the first step, by adding three salt percentages of 5, 10 and 20 into the original sand, four different sandy subgrades with a relative density of 70% were prepared. Considering three percentages of 10, 15 and 20 for micro silica additive, the water-to-cement ratio of 1, salt percentages of 0, 5, 10 and 20 totally 150 sand-cement columns were constructed in the lab environment. In continuation, unconfined compression strength (UCS) and elasticity modulus of all capped DSM columns have been determined and interpreted using scanning electron microscope (SEM) images at three ages of 7,14 and 28 days. The results indicated that increasing the salinity of subgrade soil from 0 to 20% resulted in a falling UCS and Young module by 28 and 21% for 28-days specimens. Furthermore, as a solution, adding micro silica in cement-water grout up to 15% resulted in enhancing mechanical characteristics of the DSM columns. So that adding 15% microsilica caused a 21 and 42% increase in UCS and elasticity modulus of 28-days samples respectively, executed in subgrade with 20% salt.

Effect of size and shape of copper alloys particles on the mechanical and tribological behavior of friction materials

Friction materials are composed of numerous ingredients which differ from nature and particles size. Each ingredient has its own impact on the mechanical and tribological behavior of the material. Brass ingredients have a great impact on the thermal gradient dissipation in the sliding contact between disc and brake pad material. In this research, the influence of different sizes and forms of brass ingredient was studied on the friction material behavior. The physical (density), mechanical (yield strength, young module) and thermal (thermal conductivity and specific heat) properties of the considered composites were characterized. Results proves that only physical and mechanical properties are sensitive to the changes in size and form of brass particles. The tribological behavior of the brake friction materials was also assessed using a pin-on-disc tribometer. The results show that bigger brass particles and their elongated shape allows it to be well embedded on the pad surface during braking application, and thus decreased wear rate . In contrast, the smaller particle decrease the friction stability and it rounded shape increase wear of the material since it tearing from the surface by abrasive wear.

Structural, Morphological and Magnetic Properties of Fe60−xCox(Al2O3)40 Nanocomposite Coating Deposited by Thermal Spraying

FeCo/Al2O3 nanoparticles thermal sprayed on a steel plate with different Co concentration from 0 to 20% by means of a thermal spraying process, Fe60−xCox(Al2O3)40 powder alloy was synthesized using planetary ball mill for different Co concentration at 20 h of milling. The aims of this work are to study the effect of Co concentration and milling time on the magnetic, structural behavior and mechanical properties of the FeCo/Al2O3 coating. Appearance of FeCo magnetic Solid solution phase after 20 h of milling, the crystallite sizes reduced from 18nm to 7nm and lattice strains increased from 0.36 to 0.56%, this variation are caused by the diffusion of Co atoms in iron lattice. For the coating, various phase of magnetic domains observed on surface by Atomic Force Microscopy (AFM), apparition the new phases, Al2FeO4 at 0%, CoAl2O4 at 5%, CoFe2O4 at 10% and CoFe at 20%. Saturation magnetization is max at 20 wt% of Ni and coercivity is min at 10 wt% of Co. Microhardeness and Young module were characterized by Nanoidentation techniques that shows an improvement in mechanical properties

Sustainable blends of LDPE/NR and sugarcane bagasse ashes with PE-g-MA thermomechanical relationships

ABSTRACT The polymer blends obtained with residues that before were called wastes has been growing as a viable solution, allowing improvements in the mechanical properties and as sustainable alternative. This work reports the effects of blends of low-density polyethylene (LDPE) and natural rubber (NR), with sugar cane bagasse ash (SCBA) as filler, with and without polyethylene-graft-maleic anhydride (PE-g-MA) how coupling agent. The dynamic mechanical behavior and a stress-strain analysis were studied. The materials were further evaluated by differential scanning calorimetry and morphological observations. The results showed that incorporation of the PE-g-MA reduced the strain and improved the stress and the Young module of the mixtures. Moreover, the presence of SCBA increased the hardness while maintaining the tensile strength and the elongation behavior of the polymer. The results demonstrate the potential use of SCBA in the elastomer and thermoplastic mixture, free of vulcanization agents.

MODELING THE VARIABILITY OF THE VIRTUAL YOUNG MODULE DURING THE CONSOLIDATION OF FINE-GRAINED MATERIALS

Pressure agglomeration is one of the basic methods of merging powdery and fine-grained materials. The process takes place under pressure reaching even several hundred MPa. You can divide it into two phases. In the first stage in which there is a change in the packing of the material particles, comparatively high degrees of compaction are obtained under the application of small values of external forces. In the second phase, however, the particles merge together and the formation of a quasi-continuous body. This results in much lower degrees of compaction under the influence of high values of external forces. In both phases there is continuous change of parameters describing bulk material, among others: Young's modulus, coefficient of external and internal friction, and lateral thrust coefficient. The paper deals with the problem of developing a Young's modulus variability model for fine-grained materials during their pressure.

Experimental studies on changes in mechanical properties of polymer composites under impact of thermal load determined based on compression testing

The objective of the study was to carry out an analysis of changes in mechanical properties of polymer composites in conditions of thermal load. Such an analysis may allow an initial verification of possibilities of deploying new composites in production of fire helmet shells. The reference material chosen for testing was the Ultramid composite, which is currently used for the production of fire helmet shells. In addition three different materials were selected that contained reinforcement by glass fibres bearing the trade name of Tarnamid, which are not used in manufacturing of shells. Testing was conducted in conditions of quasi-static load, during which compressive tests were performed. Mechanical loads were applied at different levels of thermal exposure, which was to simulate presence in fire conditions. Results of tests indicated that the Tarnamid composites are characterised by better compressive strength and rigidity determined on the basis of the Young module value than Ultramid PA66 GF25 used in the production of head protective shells. It has also been proven that thermal loads contribute to significant degradation in strength and rigidity of tested materials, which affects adversely protective properties of the helmet.

Study of clay soils swelling by the new method based on Laser Interferometry and the classical Odometer test

Geotechnical engineering participates in the act of construction, which means that it must meet a double concern for securityand economy. Therefore, an essential part of the engineer's responsibility rests on the recognition of soils in order to determine their nature and properties (taking into account the flow of water). In the present work, we measure the swelling and the permeability by detection of the swelling, by our new optical method based on the interferometry-laser, invented by Hassan Asselman, within the team of Optics and photonics of sciences faculty, Tetouan-Morocco. This new prototype allows us to directly measure the following parameters: the permeability k (m / s), the Young module Eand the swelling index Cs. For the latter parameter, the evolution of the strain as a function of the stresses ρ (Pa) is measured for a given degree of saturation (Until saturation). Moreover, we will use the classical odometer test, which reproduces the conditions of deformation of the soils. Using the results of the latter by the graphic methods of Taylor and Gasagrande, it is possible to determine the value of the coefficient of consolidation of the soil Cv. According to the Darcy theoretical modelfor a saturated medium, Cv depends on the permeability, the compressibility coefficient mv (or the inverse of the model of Young odometric) and the voluminal weight of the water γw. These tests will be carried out at the GEORET Geotechnical Laboratory in Tetouan. To perform this work, we chose a sample of claydistrubed, already characterized by X-ray diffraction (whose clay fraction is illite). It is extracted from the so-called "Teffalin" quarry of the Tetouan region, used in the manufacture of pottery. Finally we give a comparison between our new patented method and the classic Odometric test

YOUNG MODULE MULTIPLICITIES, DECOMPOSITION NUMBERS AND THE INDECOMPOSABLE YOUNG PERMUTATION MODULES

We study the multiplicities of Young modules as direct summands of permutation modules on cosets of Young subgroups. Such multiplicities have become known as the p-Kostka numbers. We classify the indecomposable Young permutation modules, and, applying the Brauer construction for p-permutation modules, we give some new reductions for p-Kostka numbers. In particular, we prove that p-Kostka numbers are preserved under multiplying partitions by p, and strengthen a known reduction corresponding to adding multiples of a p-power to the first row of a partition.

Anisotropic Silicone Rubber Based Magnetorheological Elastomer with Oil Silicone and Iron Microparticles

Results on anisotropic magnetorheological elastomers magnetoelasticity are presented and discussed. In the dipole approximation, and considering the MRE as a continuous linear body, the effects of magnetic field on its main elastic properties (linear deformations and Young module) are investigated. Experimental evidences that the compression of the cylindrical bar is influenced by the intensity of the longitudinal magnetic field and the Young module of the MRE sample increases with the intensity H of the longitudinal magnetic field are obtained and the results discussed.