# Stress Concentration

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## stress concentration

[′stres ‚kän·sən‚trā·shən]
(mechanics)
A condition in which a stress distribution has high localized stresses; usually induced by an abrupt change in the shape of a member; in the vicinity of notches, holes, changes in diameter of a shaft, and so forth, maximum stress is several times greater than where there is no geometrical discontinuity.

## Stress Concentration

(in elasticity theory), the concentration of large stresses on small areas adjacent to points of abrupt changes in the shape of the surface or cross section of a deformed body. The factors leading to stress concentration (”stress concentrators”) may be openings, cavities, cracks, grooves, incisions, corners, protrusions, sharp edges, or engraving, as well as various surface irregularities, such as notches, scratches, markings, and irregularities of welded seams.

The distribution of stresses σ (see Figure 1) is characterized by a sharp change in the stressed state, accompanied by rapid attenuation of stresses with increasing distance from the stressed zone. The higher the maximum stress at the site of concentration relative to the nominal stress (the average normal tensile stress at the narrowest cross section of the specimen), the more pronounced the attenuation of stress with increasing distance from the most highly stressed zone.

Figure 1. Stress concentration under tension of force P on a band of width b with a circular opening of diameter d

A measure of stress concentration is the stress concentration factor, ασ = σmaxn and ατ= τmaxn, where σn and τn are the nominal normal and tangential stresses, respectively. The values of ασ and αT are not related to the properties of the material but rather depend on the type of stress concentrator, on its sharpness, absolute size, and size relative to the specimen, and on the type of deformation and stressed state. In addition to the geometric stress concentration factors (those given above), there is also a technical stress concentration factor, which takes into account the structure and plastic properties of the material.

The nature of stress distribution and the values of stress at concentration sites are determined by using the theory of elasticity and plasticity only for a few types of concentrators, because of the great difficulty of solving such problems. In most cases, stress concentration is studied using the methods of photoelas-ticity or lacquer coatings or by tensometry. Stress-relief notches, reinforcement of the edges of openings and recesses, and stiffen-ers in plates are used to reduce or eliminate stress concentration. Strengthening of the material in the stress concentration zone is achieved by various types of treatment.

## stress concentration

Localized stress (usually as a result of localized loading or changes in geometry) which is significantly higher than the average stress.
References in periodicals archive ?
Flexible substrates are much more fragile than rigid substrates, leaving copper traces more prone to damage at stress concentration points.
Similarly, the parameter [alpha] describes stress concentration: the lower the value the lower the stress concentration (33).
Potential for load-induced cervical stress concentration as a function of periodontal support.
Our objectives were to evaluate the stress concentrations of the metal lead on the morphologic and physiologic characteristic of canola varieties.
For notched specimens with sharp comers, a stress concentration will likely occur, which could underestimate the ultimate tensile strength (UTS) properties of the flake(s).
The folds in the rubber material caused by the swelling and expansion of the rubber hose inside the constrained area produced areas of high stress concentration where cracks formed.
Stress Concentration Factors for Pin Lever of Runner Blade Mechanism from Kaplan Turbines.
As the results shown, the ellipse model has the higher deformation and lower stress than sphere model and lower stress concentration phenomenon that can decrease the triturate.
The high sensitivity of the single crystals to stress concentration is attributed to the absence of the grain boundaries which is to some extent the obstacle in the path of propagation of the main fatigue crack.
The solid finite element model was constructed in order to obtain stress and strain distribution for the coupler and to define the zones of maximum stress concentration which always occurs in the areas of dimension change where maximum damage due to cyclical loading during the operation of the coupler is accumulated.
It now becomes possible to include both the estimated mass of the vehicle and the stress concentration factor (see Technical Appendix) in considerations of the vehicular erosion process.
Glass fibre wrapped specimens typically failed by a fracture of GFRP composite at or near the corner of the specimens due to the stress concentration in those regions.

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