Quasi-static and impact tests were conducted on filament-wound carbon fiber composite pressure vessels to study factors that affect burst pressure. Observed damage included fiber microbuckling, matrix cracking, and delamination. Fiber microbuckling of the outer surface layer near the impact point was the main factor that reduced the burst pressure of the vessels. This type of damage was visually detectable on the surface. For similar levels of missile kinetic energy, the impact damage to filament-wound composite pressure vessels depends on size and shape of the colliding body in the contact area. Burst pressure for a damaged vessel decreases with the ratio of axial length of damaged fibers 1, to vessel wall thickness h, up to a ratio 1/h = 3; beyond this length of damaged section the burst pressure was independent of length of damage. Strain measurements near the region of loading showed that damage related to fiber microbuckling is sensitive to strain rate. At locations where impact damage was predominately due to fiber microbuckling, the failure strain was about six times the strain for microbuckling during quasi-static loading.
Axial rates of diffusion of the symmetrical state of stress caused by equal but opposed normal forces acting on opposite sides of an indefinitely long strip or plate, are examined in the context of orthotropic elastic materials. To obtain the stress components for this boundary value problem, the imposed surface tractions are represented by a Fourier integral. At distances larger than one quarter of the thickness, the normal stress on the middle surface is closely represented by the sum of eigenfunctions for this problem, up to, and including the first complex eigenfunction as well as its conjugate. Each eigenfunction is a product of exponentially decreasing and oscillatory terms. The exponential term is more significant for determining the rate of diffusion of stress in materials with a large ratio of axial to transverse Young’s moduli Ex/Ey ⩾ 3; this term shows a strong dependence on the ratio of transverse Young’s modulus to shear modulus Ey/G.
Reservoir modelling is repeatedly employed in petroleum reservoir studies to understand and analyse petroleum reservoirs, evaluate and/or quantify subsurface uncertainties and to generate production forecasts. For the reservoir to be described and understood with sufficient accuracy, the presence of an external energy in the reservoir must be identified and described. One of the key petroleum tools employed for this endeavouris the Material Balance. Itcan be used to understand the reservoir behaviour, including the size and response of any connecting aquifer that may be present.This study focuses on the application of a non-deterministic method -Particle Swarm Optimization Algorithm (PSO) in identification and estimation of the aquifer properties -aquifer-to-reservoir radius ratio and original oil in place in a petroleum reservoir. The method can be applied to both simple and complex reservoirs for quick analysis and interpretation of historical production data. While current methods use a deterministic approach to generate an 'optimum' solution, PSO generates an ensemble of solutions making it possible to estimate the uncertainty bandwidth and thus a confidence interval for certain parameters. This is done by applying the Havlena-Odeh material balance equation and by using production data available. We show that Particle Swarm Optimization algorithm is able to identify the aquifer-to-reservoir radius ratio and original oil in place uncertainty bandwidth. Furthermore, a P90 analysis of the results obtained compared fairly well to other methods and actual results.
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