Fabrication stresses

Quality Assurance Plan obtained will be able to meet the desired standards for Material of construction, methods of fabrication, stress relieving, various tests of the equipments at every stage of manufacture as required for safe and satisfactory performance. 

The two basic materials used in press-frame structures are cast iron and steel fabrications. Stress-strain curves for cast iron or steel indicate that steel has a relative straight-line relationship to the yield point, whereas cast-iron yield is a fracture. However, reputable builders use design criteria in the 4000-5000-... 

The worst-case scenario related to a single tank can be mitigated by using a number of smaller tanks to store a given amount of liquid. This approach, however, increases the likelihood of a smaller leak by multiplying the number of accessories that accompany the tanks (GEST 72/10). On the other side of the question, the maximum size of a tank depends on capabilities in shop fabrication, stress relief, and transportation to the site. 

Mechanical control -reduce operating stresses -relieve fabrication stresses -avoid stress concentrators -introduce surface compressive stresses... 

Constant deflection tests usually have the attraction of employing simple, and therefore frequently cheap, specimens and straining frames and of simulating the fabrication stresses that are most frequently associated with stress-corrosion failure. Constant load tests may simulate more closely failure from applied or working stresses. Tests involving the application of a constant deflection rate have become fashionable in recent times but their relevance to service failures continues to be debated. 

Reduce residual stresses developed dining fabrication (stress relieving)... 

Fig. 4 (Left) Granulate stiffness 2tc / r.=tr(a)/lr(e.), plotted against tr(F). (Middle) Scaled granulate shear resistance 2nG/L=6t /(o)/dty(t), plotted against tr(F). (Right) Orientation of the fabric-, stress-, and strain-tensors (from top to bottom). Here 150 binning intervals are used.

One also observes that the isotropic parts of fabric, stress and strain are connected via the material s bulk modulus which is proportional to the coordination number density, i.e. the trace of the fabric tensor multiplied by the volume fraction. In a similar picture, the shear modulus shows non-linear behavior, a divergence at large contact densities, and strong scatter, all indicating additional effects not accounted for by an isotropic elastic theory. Furthermore, the stress-, strain- and fabric tensors are not co-linear, i.e. the material is anisotropic and thus cannot be described by a classical isotropic elasticity theory and only two material paramters. 

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