Sharp corner

The distribution of the electric current lines leads to rounding of edges, thus very sharp corners caimot be produced by ECM. Tolerances of ca 0.127 mm are typical, although accuracies to 0.013 mm have been claimed under special circumstances. Reports on micro-ECM reveal that accuracy of ECM can be improved by special shielding and masking in order to direct the current flow only to required areas (6). 

Abrasiveness. This property is closely related to hardness in homogenous materials, but can be affected by particle shape, eg, the presence of sharp corners. In many cases a small proportion, as low as 0.5%, of a hard impurity is enough to cause severe wear to many high speed machines. 

Use fully killed or fine grain steel, controlled rolling temperatures high Mn/C ratios eliminate sharp corners in design, remove defects from steel heat treat steel. For cryogenic operations use high nickel alloy steels or austenitic stainless steels, depending on temperature. 

For a building with sharp corners, Cp is almost independent of the wind speed (i.e., Reynolds number) because the flow separation points normally occur at the sharp edges. This may not be the case for round buildings, w here the position of the separation point can be affected by the wind speed. For the most common case of the building with a rectangular shape, Cp values are normally between 0.6 and 0.8 for the upwind wall, and for the leeward wall 0,6 < C, < —0.4. Figure 7.99 and Table 7.32 show an example of the distribution of surface pressure coefficient values on the typical industrial building envelope. 

The line which defines the crystal surface can have straight pieces ( facets ) as well as curved ones. The latter correspond to a rough surface, as explained in the next section. The point at which straight and curved pieces meet can be either a sharp corner or a smooth tangential connection like z [21], where x is the deviation from the contact point in the direction... 

Solids should be removed from process liquors and vessels should be designed so that deposition of solids does not occur, e.g. by avoiding sharp corners and stagnant areas by providing facilities for complete drainage of the process liquor. 

Likewise, dead sharp corners or notches subjected to tensile loads during impact may decrease the impact resistance of a product by acting as stress concentrators, whereas generous radii in these areas may distribute the tensile load and enhance the impact resistance. This point is particularly important for products comprised of materials whose intrinsic impact resistance is a strong function of a notch radius. Such notch sensitive materials are characterized by an impact resistance that decreases drastically with notch... 

Basically, in the vicinity of a sharp comer all fringes converge toward the apex. Having a high density of lines at this point indicates the presence of high stress level. At a rounded corner there will be considerably less concentration. Besides the molding problems, sharp corners often cause premature failure because of the stress concentration. To avoid these problems, inside comer radii should be equal to one-half the nominal wall... 

Sharp corner As reviewed, and never to many times, when a drawing does not show a radius, the tendency is for the toolmaker while manufacturing a mold to leave the intersecting machined or ground surfaces as they are generated by the machine tool. The result is a sharp comer on the molded product. Such sharp comers on the insides of products are the most frequent property detractors. 

Sharp corners become stress concentrators. The stress-concentration factor... 

The Izod impact test may indicate the need to avoid inside sharp corners on parts made of such materials. For example, nylon and acetal-type plastics, which in molded products are among the toughest materials, are notch-sensitive and register relatively low values on the notched Izod impact test. 

H2. It may be noted that the HI and H2 boundary conditions for the symmetrically heated passages with no sharp corners (e.g., circular, flat, and concentric annular channels) are identical they are simply designated as H. 

One of the cardinal rules in die design is to avoid all sharp corners. Why ... 

C. E. Inglis, Stresses in a PlateDue to the Presence of Cracks and Sharp Corners, Trans. 

Inglis, C. E. 1913. Stresses in a plate due to the presence of cracks and sharp corners. Trans. Instit. Naval Architects 55 219-241. 

Moffat, H. K., Viscous and Resistive Eddies Near a Sharp Corner, J. EluldMech. 18, 1 (1964)... 

Another common location for creep failures of encapsulated assemblies is at sharp corners or edges. Many encapsulants such as polyimides must be applied in thin coats, and coverage of points, edges, or corners is difficult or impossible. Sharp corners, characteristic of most thin-film devices provide ideal conditions for the initiation of creep failures due to the resulting irregularity of the encapsulant coverage. 

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