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Rotational effects on components from bolting - A study in how different factors affect rotational displacement of components

Patrik Björnsson ; Elias Hortlund
Göteborg : Chalmers tekniska högskola, 2017. Diploma work - Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden, ISSN 1652-8557; 2017:25, 2017.
[Examensarbete på avancerad nivå]

The purpose of this project was to find and map correlations between different parameters and the resulting rotational displacement of a component being bolted. The background to this thesis emanates from a problem encountered at Volvo where components tend to rotate as they are bolted to the car body. One component in which this is visible is the car hood, where about 50% of the hoods on a specific car model have to be adjusted post-assembly. The project was therefore mostly conducted at Volvo Cars in Torslanda. During the work a number of experiments were carried out using both generic components as well as components specific to a Volvo vehicle. A finite element simulation model was developed, yet only using a static simulation. It can however be used as a starting point for the development of a dynamic model. One of the projects most important result is the effect of SEMS bolts, that is, a bolt with a pre-assembled washer. When using a washer, the rotation and the exerted torque of the component are both reduced, on an average, by a factor of 2.2 at a minimum. This factor was consistent across most component materials. However, the rotation was 18 times greater of components made from aluminium when no washer was used. Our studies show that the relation between the transferred torque between bolt and component and the final rotation of the component seem to be linear. Another result observed is the effect of oil applied between component, bolt, and the underlying surface. When oil is applied between bolt and component the transferred torque is reduced by a factor of two. On the other hand, when oil is applied between component and the underlying surface the rotation of the component is increased by a factor greater than five. The optimum angular velocity of bolting was found to be between 200-220 RPM. At lower angular velocities, the nut runner has a longer period of time to make the component rotate before it is locked into place by the axial tension. At higher speeds, it becomes difficult to get accurate readings because the nut runner jumps out of place. During the studies, a wide distribution of the results was observed. Additional iterations would most certainly have produced more reliable results and, thus, a better understanding, but time, material availability, as well as access to the tools were limited.



Publikationen registrerades 2017-07-03. Den ändrades senast 2017-07-03

CPL ID: 250369

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