Document Type

Thesis - Open Access

Award Date

2021

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Todd Letcher

Keywords

Aluminum, Clampload, Creep, Embedment, Joints, Preload

Abstract

Embedment in bolted joints is defined as the local deformation of surfaces into one another due to uneven contact. Embedment that occurs after the tightening of a bolted joint can cause loss of preload in the joint potentially leading to failure. VDI 2230, a German standard for bolted joint design, is currently the main source for engineers regarding embedment. It related expected embedment to the surface roughness in steel bolted joints. This research expands on the VDI standard by performing tests on a commonly used aluminum alloy and a steel alloy. Both cold rolled 1045 steel and 6061- T6511 aluminum bolted joints preload losses were monitored using M10 class 8.8 and 12.9 stain gauge bolts with joint interfaces having varying surface roughness. The joints were loaded to 75% of their proof load, and shear loaded externally in a sine wave using a universal testing machine. The slip coefficient was also found for each surface roughness. Results showed that as surface roughness increases embedment, and the slip coefficient increases. As the external shear load increased the amount of initial embedment increased. At the same external shear load and roughness T6511 aluminum displayed on average 50% more embedment than 1045 cold rolled steel. The results showed that aluminum will embed more than steel at the same preload and shear load, embedment values are affected by external shear force, material surface roughness, and surface slip coefficient. Embedment was also tested with joints having various clamp lengths and it was determined for the clamp lengths used in this experiment that embedment is not a function of clamp length.

Number of Pages

61

Publisher

South Dakota State University

Rights

Copyright © 2021 the Author

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