An Experimental Study on Pre-tensioned Concrete Members

Abstract: Prestressed concrete elements are highly being used in the construction industry. For these kind of precast members, exposure to the loading starts at the fabrication processes. There might be high level of stress fields inside the element because of the prestressing. Exact values of these stresses are being assumed according to the linear homogenous design criteria. However, modeling a pre-tensioned prestressed concrete member via photoelastic experimental procedure could lead to make exact stress analysis in a pointwise manner. The analogy between the prestressing phenomena with photothermoelasticity led to make a pretensioned concrete model with using the “frozen-stress” method of photoelasticity. Two sorts of three-dimensional photoelastic models are prepared and analyzed with using the experimental techniques of three-dimensional photoelasticity and aimed to deal with the investigation of the pre-stress distribution after the fabrication process of the pre-tensioned reinforced concrete members. With considering the technical literature, insufficient information requires to make an investigation of the stress distribution at the vicinity of the free edges and bonding area of the reinforcing material of the pre-stressed structural members. Finally, obtained results show that some regions in a prestressed member have to endure high level of compressive and shear forces immediately after the release of prestress. This study mainly deals with the determination of the critical regions in a prestressed member and taking some precautions in order to keep the safe design margin

Stress analysis of ceramic insulation coating on Cu/MgB2 wires for W&R MgB2 coils

Saçlı, Ömer Asım (Arel Author)Ceramic insulation coatings were produced on Cu/MgB2 wires, which were fabricated by Hyper Tech Research Inc., using Continuous Tube Forming and Filling (CTFF) process, from the solution of Zr, and Y based organometalic compounds, solvent and chelating agent using reel-to-reel sol–gel technique for MgB2 coils. Y2O3–ZrO2/Cu/MgB2 wires were annealed at 700 ?C for 30 min with 5.8 ?C/min heating rate under 4% H2–Ar gas flow. Residual stresses were examined for Cu/MgB2 wire and YSZ coatings with varying thicknesses. It was observed that displacement values are independent from YSZ thicknesses and the maximum effective stress value is in the Cu region. The surface morphologies and microstructure of samples were characterized using SEM. SEM micrographs of the insulation coatings revealed cracks, pinholes and mosaic structure

Theoretical treatment of disc cutters subjected to general cutting forces

This paper constructs a theoretical framework to investigate the stress and deformation state within the body of a roller disc cutter from the cutter characteristics (radii of the shaft and disc and the length of the shaft), the characteristics of the cut (depth of cut), the mechanical properties of the constructive material (Poisson’s ratio and Young modulus) and the boundary conditions involved during the disc cutting process. To pursue the objectives, mathematical formulations and calculations required for the analysis of elastic variables induced in the disc and shaft parts of a roller disc cutter subjected to general cutting forces are investigated. Assuming elastic material behaviour, the disc cutter in contact with its shaft is considered as a partially loaded annulus, and the shaft inside the disc as a laterally loaded cylinder subjected to stresses corresponding to different cutting configurations. The Airy stress function, Michell’s method and Papkovich–Neuber solutions are employed in two- and three-dimensional elastic domains using a double Fourier series technique