Aluminium notch

Table 1. Mechanical properties of selected pressure-infiltrated ceramic particle reinforced aluminium composites Young s modulus (E), yield and ultimate tensile strengths (aQ2, Outs), tensile elongation ( 0, and fracture toughness parameters. Toughness Kic was measured from J-R curves on pure A1 matrix composites and by chevron-notch fracture testing on Al-Cu...

If the available materials to construct the shaft are a ceramic with i2m = 400 MPa or the aluminium alloy AlSilMgMn with Rpo.2 = 202 MPa and Rm = 237 MPa, we can expect the ceramic to fail because the stress at the notch root is much larger than the tensile strength. For the aluminium alloy, the tensile strength is also exceeded, and we thus might expect its failure as well. However, the calculation is not valid in the case of a ductile material, for equation (4.1) is valid only for a linear-elastic material, whereas the alloy AlSi 1 MgMn yields at Rpo.2 = 202 MPa. This increases the strain at the notch root and reduces the stress concentration. The actual stress at the notch root cannot be calculated with the tools introduced so far. In the next section, we will discuss Neuber s rule that allows to estimate the stresses. 

Equipment and pipes within the coldbox are made of aluminium alloy or 18/10-CrNi-steel. These materials are suitable for the application at low temperatures and dispose high ductihty even at 100 K, i.e. no tendency to propagation of cracks, originating from notches, sharp edges or abrupt discontinuities of the wall thickness. 

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