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In this study, carbon steel corrosion was evaluated in salt water solutions using the newly developed non-destructive electrical method which can be easily adopted in the field for real-time monitoring and the results were compared to some standard test methods such as weight loss, corrosion rate and potential difference. The average weight loss in 10% salt solution (accelerated corrosion and also representing the hydraulic fracking fluids) in one year was 1.05% and corrosion rate was 1.54 mm/year, using the ASTM G1 method. Vipulanandan correlation model was used to represent the weight loss versus time relationship. The potential difference between the corroding steel and standard calomel electrode in 1M salt solution reduced from -0.680 V to -0.791 V in two years, a 15% total change. The use of the new nondestructive electrical method was to detect and quantify the surface and bulk corrosion in the field. Tests were performed to first verify the best electrical property that will be highly sensitive and represent the steel corrosion. The findings from this study indicated changes in the newly developed electrical corrosion index for the surface (2D representation) and the resistivity (second order tensor, 3D representation) for the bulk material using the Vipulanandan Impedance Corrosion Model. Corrosion development in 30 inches long steel specimens were studied in the 3.5% salt solution (simulating sea water) for 500 days. The changes in the specimens were monitored at regular intervals using the new two probe method and measuring the impedance-frequency relationship using alternative current up to a frequency of 300 kHz. The surface corrosion was quantified using the new electrical corrosion index parameter, which changed from point to point on the surface of the corroding steel and the change was over 200%. The change in the bulk resistivity along the length of the steel specimen was over 40,000 times (4,000,000%) in 3.5% salt solution compared to the weight loss and reduction in the potential difference. Hence the electrical resistivity for the bulk material and the new corrosion index for the surface corrosion are highly sensing parameters for detecting and quantify the corrosion in the steel.

During the installation of oil and gas production wells, it is critical to have a successful cementing operation. The quality of the cementing job strongly depends on the cleaning efficiency of the spacer fluid in removing not only the drilling fluid with the cuttings but also the filter cakes during the drilling operation. Based on the depth applications, different types of spacer fluids are used in the oil gas industry. In this experimental study modifying the smart spacer fluid properties in-situ was investigated. Optimization of spacer formulation was carried by having material properties such as density, rheology and cleaning efficiency as the variables. In this study, using the maximum shear stress tolerance of the spacer fluid determined using the Vipulanandan rheological model was investigated to quantify the cleaning efficiency of the spacer fluid. In this study, the effects of pressure, temperature and magnetic field strength on the electrical resistivity and rheological properties of a sensing smart spacer fluid modified with iron oxide nanoparticles (nanoFe2O3) were investigated. The temperature was varied from 25°C to 75°C. The magnetic field strength was varied from 0 T to 0.6 T. The nanoFe2O3 contents (particle size of 30 nm and surface area of 38 m2/gm) in the spacer fluid were varied up to 1% by the weight of spacer fluid to enhance the sensing and rheological properties of the spacer fluid. The initial resistivity of the spacer fluid without any nanoFe2O3 at 25°C was 0.2 Ωm. Addition of 1% nanoFe2O3 increased the electrical resistivity by 3.5%. Adding nanoFe2O3 enhanced the piezoresistive behavior of the smart spacer fluid. The electrical resistivity changed by 0.7, 5 and 12% for the spacer fluids with 0,0.5% and 1% nanoFe2O3 respectively for a maximum pressure of 500 psi. Increase in the magnetic field strength improved the rheological properties while increasing the temperature decreased the rheological properties of the spacer. The rheological properties of the spacer fluids were characterized by high strain rate to determine the nonlinear behavior of the shear thinning spacer fluid. The spacer fluid rheology was modelled using Bingham-plastic model, Herchel Bulkley model and Vipulanandan model. The electrical resistivity was used as sensing parameter to monitor the percentage of oil cleaning efficiency of the spacer fluid. Based on the new Vipulanandan rheological model, the yield stress (τo) of the modified spacer fluid increased by 6% to 100% depending on the oil content, nanoFe2O3 content, temperature and magnetic field strength. The maximum shear stress tolerance (τmax) for the spacer fluid increased from 49.4 Pa to 65.5 Pa, 33% increase at the temperature of 25°C with 1% addition of nanoFe2O3. The cleaning efficiency of the spacer fluid in removing oil based drilling fluid contamination was 79.8% without the addition of nanoFe2O3. With the addition of nanoFe2O3 the cleaning efficiency increased from 79.8% to 99.4%, 20% increase in the efficiency. The maximum shear stress tolerance (τmax) correlated well with the cleaning efficiency. Also the change in the electrical resistivity of the spacer fluid after cleaning correlated well with the cleaning efficiency and hence can be used for in-situ monitoring of the cleaning operation.

Nano aluminum oxide (NanoAl2O3) up to 1% was added to the smart cement with a water-to-cement ratio of 0.38 to investigate the effects on the sensing properties and compressive strength. Series of physical, curing and compressive loading experiments evaluated the smart cement behavior with and without NanoAl2O3 up to 28 days of curing. The addition of 0.5% and 1% NanoAl2O3 increased the initial sensing property (electrical resistivity) of the smart cement by 10% and 30% respectively. In a one day of curing, the maximum change in the electrical resistivity (RI24hr) for the smart cement without NanoAl2O3 was 375%. The RI24hr for the smart cement with NanoAl2O3 increased with the amount of NanoAl2O3. Addition of 1% NanoAl2O3 increased the compressive strength of the smart cement by 14% and 42% after 1 day and 28 days of curing respectively. The nonlinear Vipulanandan p-q curing model was used to predict the changes in electrical resistivity with curing time. The piezoresistivity of smart cement with the addition of NanoAl2O3 was over 500 times (50,000%) higher than the regular cement depending on the curing time and NanoAl2O3 content. Also a gage factor correlation model was used to relate the strain to the resistivity changes under compressive loading. The Vipulanandan p-q stress-strain and the piezoresistivity models also predicted the experimental results very well. A linear correlation was obtained between the RI24hr and the compressive strength of the modified smart cement based on the curing time.

*Extensive use of laminated composites at cryogenic temperatures is envisaged in the next generation Reusable Launch Vehicles (RLVs). The RLVs will include light fuel tanks fabricated using graphite/epoxy composite laminates and will be required to contain liquid hydrogen (LH2) fuel. These tanks undergo extensive thermo-mechanical loading and develop damage in the form of matrix cracks and delaminations. A build up of matrix cracks in the plies of the laminated composite wall of a tank may lead to the formation of a network of interconnected cracks through the thickness of the tank-wall and provide a path for fuel to permeate to the outside. In this context, the detection of matrix cracks and their connectivity takes on an unprecedented significance. In this work, an ultrasonic technique for the detection of matrix cracks in each of the plies of damaged graphite/epoxy laminated composites is developed. Results are reported for an eight-ply quasi-isotropic graphite/epoxy laminate, having [90/45/0/-45]s lay-up. Matrix cracks in each of the plies of the laminated composite were detected even in the presence of a rather high density of cracks in all of the remaining plies. The ultrasonic data were corroborated by comparing them with the corresponding results obtained by using the more traditional methods of optical microscopy and X-radiography. Excellent quantitative correlation was observed between the results obtained with ultrasonics and the traditional methods.

This paper investigates the fracture toughness of the rigid, closed-cell, polyurethane foam used for insulation on the Space Shuttle External Tank. Plane strain fracture toughness data were obtained by loading double-edge-notched specimens in tension. To account for the anisotropic nature of the foam, two types of specimens were tested so as to represent fracture properties along two different directions. Additionally, for each type of specimen, two different notch sizes were tested.

Fracture toughness of the rigid, low-density, closed-cell, polyurethane, foam used for insulation on the Space Shuttle External Tank is investigated. Data were obtained by loading double-edge-notched specimens in tension. To account for the anisotropic nature of the foam, two types, of specimens were tested so as to represent fracture properties along two different material directions. Additionally, for each type of specimen, two different notch sizes were tested.Copyright © 2006 by ASME

Using an ultrasonic technique matrix cracks in each of the plies of a quasi‐isotropic composite laminate were detected even in the presence of a rather high density of cracks in all of the plies. The ultrasonic data were corroborated by comparing them with the corresponding results obtained by using the traditional methods of optical microscopy and X‐radiography, and an excellent quantitative correlation was observed between the two.