Name: stress at holes and fillets
Uploaded: 2024-03-07T13:22:38.000Z
Duration: 1 min 24 s
Channel: JoVE

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&#39;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.

stress concentrations

Stress Concentrations

Stress concentration is when stress intensifies near discontinuities such as holes or abrupt cross-sectional changes in a structural member. This localized stress can often surpass the average stress within the member. The stress distribution in flat bars, either with a circular hole or varying widths connected by fillets, can be determined experimentally using a photoelastic method. The results are based on ratios of geometric parameters like the ratio of the hole&#39;s radius to the smaller width in the case of a circular hole and the ratios of the hole&#39;s radius to the smaller width and the larger width to the smaller width for fillets.
The structural design aims not to map the exact stress distribution but to ensure that the maximum stress in a given section does not exceed the allowable stress under specific loads with a stress concentration factor. This factor, defined as the ratio between the maximum and the average stresses in the critical section, helps determine the maximum stress near a discontinuity under a given axial load. However, it is important to note that this method is only valid if the maximum stress does not exceed the material&#39;s proportional limit because the stress-concentration factors are determined by assuming a linear relationship between stress and strain.

Stress concentration refers to the amplification of stress in a structural member near points of discontinuity, such as holes or abrupt changes in ...

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JoVE Core

Mechanical Engineering

Unit 1

Stress and Strain - Axial Loading

KEY TERMS AND CONCEPTS

stress at holes and fillets

Stress can become much higher near holes and abrupt changes in shape within a structural member. These discontinuities create localized stress that may exceed the average stress in the part.

For flat bars, the stress distribution can be measured experimentally with a photoelastic method. This approach is used for bars with a circular hole or with changing widths joined by fillets. The results depend on geometric ratios, such as the hole radius to the smaller width for a circular hole. For fillets, the key ratios include the hole radius to the smaller width and the larger width to the smaller width.

In design, the goal is not to map every detail of the stress field. Instead, engineers check that the maximum stress in a section stays below the allowable stress for the applied load. They use a stress concentration factor, which is the ratio of maximum stress to average stress in the critical section, to estimate the highest stress near a discontinuity under axial load. This method applies only when the maximum stress stays within the material’s proportional limit, since the stress concentration factors are based on a linear stress-strain relationship.

Stress at Holes and Fillets

normal strain under axial loading

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Axial stress and strain in a rod describe how a material changes length when a force is applied along its axis. The force may stretch the rod or compress it. In mechanics of materials, this deformation is called normal strain. Normal strain is found by dividing the change in length by the original length. This gives a unitless ratio that shows how much the material deforms under load. A load-deformation diagram can show elongation, but it cannot predict how another rod will deform. When a...

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Stress can become much higher near holes and abrupt changes in shape within a structural member. These discontinuities create localized stress that may exceed the average stress in the part. For flat bars, the stress distribution can be measured experimentally with a photoelastic method. This approach is used for bars with a circular hole or with changing widths joined by fillets. The results depend on geometric ratios, such as the hole radius to the smaller width for a circular hole. For...

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key terms and concepts

Learn how holes and fillets raise stress in flat bars, how photoelastic testing measures it, and how stress concentration factors guide safe design.

Stress at Holes and Fillets | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Stress at Holes and Fillets

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