Structural notches

Variations of parameter a are rather modest if we deal with structural notches having a theoretical stress concentration factor k, between 2 and 5. Siebel and Stieler choose a = 2 and considered the ratio kjkf as being a function of x... 

Notched monotonic tensile specimens can be a useful approach to begin to understand the effect of structural notches on the behavior of UHMWPE total joint replacement components. Therefore, we developed a testing methodology to characterize the stress strain and fracture behavior of a notched tensile specimen. Additionally, the stress-strain behavior of notched tensile specimens can be used to challenge the Hybrid Constitutive Model for UHMWPE (see Chapter 35) with a multiaxial stress state. Accurate prediction of the behavior of a notched specimen by a simulation utihzing the Hybrid Model would be one vahdation of its accuracy in describing the mechanical behavior of UHMWPEs. 

Signals from the notch tip can only be identified for the herringbone grain structure and not for the perpendicular one. 

Notch tip With perpendicular grain orientation no notch tips are detected. The snapshots (see Fig. 7 second and third snapshot from top on the right) show that in the direction to the receiver there is a gap in the reflected / diffracted quasi shear wavefront. In contrast, the notch tips can be detected within the herringbone structure. 

While ideally structures should be designed and fabricated so that environment-sensitive cracking is avoided, in practice it is sometimes necessary to live with the problem. This implies an ability to detect and measure the size of cracks before they reach the critical size that may result in catastrophic failure. Such inspection has important implications for plant design, which should be such as to allow inspection at relevant locations. The latter are regions of high residual stress (welded, bolted or riveted joints) and regions of geometrical discontinuity (notches, crevices, etc.) where stress or environment concentration may occur. 

In all blast-resistant structures (steel, concrete, or masonry) special attention should be given to the integrity of connections between structural elements up to the point of maximum response. For example, it is important to prevent premature brittle failure of welded connections to avoid stress concentrations or notches at joints in steel structures and to provide ductile reinforcement detailing in concrete/masonry structure connections. For all materials, it is recommended that connections be designed to be stronger than the connected structural members such that the more ductile member will govern the design over the more brittle connection. 

In the case of chain and sheet silicates having typically anisodesmic structures, interpretational difficulties arise. Isodesmic structures are distinguished by the absence of very compact, clearly discernable components, whereas anisodesmic structures contain components with internal bonds stronger than those between the components. Consequently, the hardness of compounds of this type depends chiefly on the resistance of the weakest bonds, the variability of the energetic conditions of interlaminar bonds (van der Waals ) and the variety of surface forms of the chains and strata in mineral structures, e.g., smooth, undular, notched, and so on. 

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