ESDU 85021
Analysis of pretensioned bolted joints subject to tensile (separating) forces.
Abstract:
By using an idealised joint model, the concept of a load/deflection diagram is developed to show the influence of pretensioning through to joint separation. That analysis is then built on to show how the load paths may be determined in a practical joint, including the effects of prying apart when the load is off-set from the fastener axis, dimensional tolerances on squareness and flatness of the components, fastener yielding, level of pretension, and changes in materials properties with temperature. Guidance is included on estimating the stiffness contribution made by each component of the joint and, in particular, to assist in rapid calculation of the feet, graphs are provided. Factors governing the selection of fastener size, avoidance of separation, and fatigue loading of the fastener are explained. Sketches illustrate the influence of bolt size and material, hinge point position, washer and plate and foot thicknesses, load, and other parameters on pretension values for bolt yielding and joint separation. Two extensive practical worked examples illustrate the use of the methods. A program based on the methods presented, ESDUpac A8521, accompanies the Data Item. The program treats any combination of material properties, washers of different design on either end of the bolt, plates between the feet or layered over the feet and under the bolt head or nut, and non-standard features such as Belleville washers represented by their stiffness.Indexed under:
Details:
| Data Item ESDU 85021 | |
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This Data Item is complemented by the following software:
| Name | Details | ||||
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ESDUpac A8521 |
This program is only available to subscribers. |
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This Data Item contains 13 interactive graph(s) as listed below.
| Graph | Title |
|---|---|
| Figure 1 | Variation in effective area of plates for axisymmetrically loaded joints |
| Figure 2a - Part 1 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.3 |
| Figure 2a - Part 2 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.3 |
| Figure 2b - Part 1 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.4 |
| Figure 2b - Part 2 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.4 |
| Figure 2c - Part 1 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.5 |
| Figure 2c - Part 2 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.5 |
| Figure 2d - Part 1 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.6 |
| Figure 2d - Part 2 | Variation of second moment of area for joints with thick feet with their geometry. d/g = 0.6 |
| Figure 3a | Variation of separation load for joints with thick feet with geometry. γf = 0.6 |
| Figure 3b | Variation of separation load for joints with thick feet with geometry. γf = 0.7 |
| Figure 3c | Variation of separation load for joints with thick feet with geometry. γf = 0.8 |
| Figure 3d | Variation of separation load for joints with thick feet with geometry. γf = 0.9 |