Modeling fiber reinforced polymer (FRP) coating in retrofitting concrete walls against explosive loads

One of the issues considered in the design and dynamic resistance of structures (as seismic or explosive) is the use of materials which cause reduction in the force applied on the structure. With regard to the fact that greater loading is on the wall of concrete structures, the use of materials that reduce explosive force on the structure wall are among explosive force reduction methods.One of the viscose and damping materials of polymers is FRP, and in this study the FLAC3D software is used to evaluate the effect of this material on reducing force implemented on the walls and hence reduction of wall movement due to explosion. The concrete wall along with the FRP layer is modeled under dynamic loading. The effect of damping coefficient, number of FRP layers and concrete wall thickness has been evaluated.     

Effect of Deformation-induced Residual Stress on Peel Strength of Polymer Laminated Sheet Metal

The adhesion between adhesively bonded polymer film and a metallic sheet substrate in a polymer laminated sheet metal (PLSM) subjected to large deformation, such as in a forming process, is influenced by two deformation-induced factors. These are (i) evolution of surface roughness of metallic substrate with applied strain and (ii) development of residual stress in the polymer adherend (polymer film with a thin uniform adhesive layer on one side) arising from significant differences in the deformation behavior of metal and polymeric components. A new experimental methodology was devised in this study to decouple the effects of substrate surface roughness and residual stress on interfacial peel strength (IPS) of uniaxially deformed PLSMs. This methodology was based on 180° peel testing of PLSM specimens prepared under two different lamination conditions, one involving systematic pre-straining in uniaxial tension of the metallic substrate prior to laminations and the other involving post-lamination pre-straining of the PLSM. The role of pre-strain and peel test speed, for the above laminations conditions, were critically analyzed for their effect on IPS of two differently tailored PLSM systems. The IPS results were attributed to the effect of deformation-induced residual stress and metallic surface roughness. The analysis suggests that IPS is strongly dependent upon the residual stress induced by uniaxial deformation but only marginally on substrate surface roughness depending upon the constituents (film and adhesive) of the adherend. The magnitude of pre-strain was inversely and non-linearly related to IPS for both deformed PLSMs. Peel test speed, on the other hand, showed a more complex behavior in terms of IPS for the two PLSM systems.     

Supramolecular Structure,Mode of Coordination,Thermal and Potentiometric Studies of Polymer Complexes: A Review

Chelating compounds derived from acryloyl monomers are being utilized as suitable ligands. They enable the formation of rigid coordination polymers. This review gives information about preparation and structurally characterization the polymer complexes by analyses, spectral techniques like IR, NMR, ESR thermal and potentiometric methods. The ESR spectral data of the Cu(II) complexes showed that the metal–ligand bonds have considerable covalent character. The thermal stability was investigated using thermogravimetric analysis. The thermal behavior of these chelates shows that the hydrated complexes lose water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The results showed that the polymer complexes are more stable than the homopolymer. Proton ligand dissociation and metal ligand stability constants of acryloyl monomers with some transition metal ions in monomeric and polymeric forms potentiometrically were determined.     

Comparison between Two Vertical Enclosures Filled With Porous Media under the Effect of Radiation and Magnetohydrodynamics

A numerical study has been carried out to investigate the temperature distribution and the natural convection heat transfer in axisymmetric two-dimensional vertical saturated porous cylinder with steady state laminar flow. A comparison between two situations is done under the effect of MHD （magnetohydrodynamics） and radiation. In the two situations, the vertical walls of the cylinder are cooled with constant wall temperature and a constant heat generation subjected along the centerline of the cylinder. The first case for cylinder with insulated upper surface and cooled bottom surface while the second case for cylinder with cooled upper surface and insulated bottom surface. The governing equations used are continuity, momentum and energy equations which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using the MATLAB-7 programming. The parameters affected the system are Rayleigh number ranging within （102≤ Ra ≤104）, radiation parameter （0≤ Rd ≤ 2） and magnetohydrodynamics MHD （Mn） （0 ≤ Mn≤ 2）.The results show that the temperature of Case 1 is more than that in Case 2 at constant Ra, Mn and Rd while the value of the stream in Case 2 is greater than that in Case 1. Nu increase with the increase of Rd and increasing Mn caused the temperature to increase and the streamline dropped while Nu decreased. A correlation has been set up to give the average Nusselt number variation with Ra, Rd and Mn for which the results are found to be in good agreement with previously published researches.     

Damage mechanisms of fatigue fracture in a metastable beta Ti-15-3 alloy

The mechanism of crack tip deformation in metastable beta Ti-15-3 alloy under fatigue loading has been examined. In spite of the small thickness of the test specimens (1 mm), the plastic zone revealed plane strain conditions which was transformed to a plane stress zone when its size became 0.25 of the crack length. Slip processes whose density increased with crack length were the dominant microscopic feature of crack tip plasticity. Microcracks emanating from the main crack appeared as a result of extensive slip damage. Transmission electron microscopy (TEM) and X-ray evidence indicate the absence of twinning or phase transformation and that dislocation processes constitute the microstructural origin of crack propagation resistance in the alloy. Energy calculations show that the specific energy of slip, 20 MJ m⁻³, exceeds that of microcracking by three orders of magnitude.     

Behaviour of poly(β-hydroxybutyric acid) in dilute solution

The refractive indices of poly(β-hydroxybutyric acid) (PHB) at four wavelengths have been determined via different procedures. Viscometric and light scattering measurements have been made on solutions of eight samples of PHB (M_w = 20·9 × 10³?929 × 10³ g mol^?1) in 2,2,2-trifluoroethanol. From the dependences of intrinsic viscosity and of radius of gyration on molar mass, the conformation of PHB in dilute solution is shown to be that of a random coil. The findings are discussed in relation to existing conflicting evidence on the conformation of this polymer.     

A decorrelating detector for use with antenna arrays

This paper addresses the problem of synchronous CDMA communications when, due to bandwidth limitations, signature waveforms have relatively large correlations. A receiver which uses the multiple received signals available from an antenna array is proposed and its performance analyzed. This receiver may be interpreted as a multichannel extension of the decorrelating detector and therefore shares its immunity to near-far effects. The receiver uses the discrimination afforded by the antenna array to effectively reduce the correlation between users' transmitted signals thereby avoiding the reduction in performance which occurs in the single channel decorrelator when signature correlations become significant.This work was supported by the National Science Foundation under Grant MIP-9202081. This paper was presented in part at the International Conference on Communications, ICC'94, New Orleans, Louisiana.     

Studies on expansive cement 1-volume changes

Kaolin was used as an aluminous raw material instead of bauxite for the manufacture of expansive cement clinker. The linear expansions and compressive strengths of the different expansive cement pastes were investigated. The expansibility of the paste was highest at a molar ratio CaSO₄ : CaO : C₄A₃$\text{S}$ of 8 : 6 : 1.