Tensile stress, tanks

Tensile stresses are critical in tank design. The designer assumes the pressure in this application will not exceed 100 psi (700 Pa) and selects a safety factor of 5. The stress must be known so that the thickness can be determined. The stress or the strength of the final laminate is derived from the makeup and proportions of the resin, mat, and continuous fibers in the RP material. 

Representative panels must be made and tested, with the developed tensile stress values then used in the formula Thus, the calculated tank thickness and method of lay-up or constmction can be determined based on ... 

In Eq. (4.42) 1 is the height of the supporting columns of the tank, n the number of bolts and a the spacing plus the inset of the bolts on the support column base plate (m). The following tensile stress results in the bolts from the force K... 

In Eq. (4.43) K is the force according to Eq. (4.42) and A the cross sectional area of a single bolt. If a exceeds the permissible tensile stress for the bolt material it is assumed that the tank is overturned. 

What is the tensile stress in the bolts and does the tank overturn ... 

Initially (at tQ), the aluminum plate is cooled and contracts, compressing the warmer foam, as shown in Fig. 3b. As time progresses (tj, t2, and t3), the insulation cools and the foam tends to contract in accordance with the local temperature and its coefficient of thermal expansion. However, near the tank surface, the insulation is constrained from contracting by the much stiffer aluminum plate, which, because of a lower coefficient of expansion, experiences less contraction than the foam. Ultimately, at t3 (as shown in Fig. 3c), the combination of the thermal contraction mismatch between the insulation and the aluminum tank and temperature distribution through the insulation lead to an in-plane stress pattern with large tensile stresses in the insulation near the tank and smaller compressive stresses at the free surface. 

The magnitude of the tensile stresses is determined primarily by the thermal contraction mismatch between the aluminum and the foam however, the length, width, and thickness of the insulation influences the level of the compressive stresses. For 15.2 cm (6 in) thick insulation, as shown in Fig. 4, edge effects significantly reduce compressive stresses for smaller pieces of insulation. [The stresses in Figs. 4 and 5 are based on polymethacryli-mide insulation bonded on an aluminum tank at 20 K (-424°F) with a maximum insulation exterior temperature of 317 K (110°F)]. For example, a 0.3 m (1 ft) square insulation sample experiences a maximum compressive stress that is approximately 1/3 the stress in a 1.83 m (6 ft) square piece of insulation. The latter approaches the stress level for an infinite slab of insulation. 

In the case of unanchored tanks, uplifting may occur and, instantaneously, the welded connection between the tank bottom plate and the tank shell at the uplifting side of the tank is subjected to significant tensile stresses that may lead to weld failure. This may result in fracture at the base plate welded connection and immediate loss... 

No one steel exceeds the tensile modulus of mild steel. Therefore, in applications in which rigidity is a limiting factor for design (e.g., for storage tanks and distillation columns), high-strength steels have no advantage over mild steel. Stress concentrations in mild steel structures are relieved by plastic flow and are not as critical in other, less-ductile steels. 

Deposits from all-chloride solution Nickel deposits from a solution of nickel chloride and boric acid are harder, stronger and have a finer grain size than deposits from Watts solution. Lower tank voltage is required for a given current density and the deposit is more uniformly distributed over a cathode of complex shape than in Watts solution, but the deposits are dark coloured and have such high, tensile, internal stress that spontaneous cracking may occur in thick deposits. There is therefore little industrial use of all-chloride solutions. 

The tensile strength of specimens prepared from mycelial pellets of various fungi was measured by pendulum strength tester. The results are shown in Table 1. Both viscous stress and Reynolds stress need to be considered as shear stress to rupture mycelial pellets in a turbulent tank. The former is about 2 x 10 kg/cm, which is estimated using... 

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