18.19 : ריכוזי מאמץ

Stress concentration refers to the amplification of stress in a structural member near points of discontinuity, such as holes or abrupt changes in cross-section. This localized stress often exceeds the average stress within the member.

Consider a flat bar of varying widths connected by fillets. The stress distribution in such a member is independent of the member's size and the material used. It is dependent only on the ratios of geometric parameters.

In structural design, engineers must ensure the maximum stress in a section does not exceed the allowable stress under specific loads, rather than calculating the exact stress distribution.

The ratio of maximum stress and average stress in the critical section of the discontinuity is the stress-concentration factor.

Stress-concentration factors, computed from geometric ratios, help to determine maximum stress near discontinuities under given axial loads.

The process involves multiplying the average stress in the critical section by the appropriate stress concentration factor. However, this is only valid if the maximum stress does not exceed the proportional limit of the material.