Modeling and Analysis of a Screw Fitting Assembly Process Involving a Cast Magnesium Component

Kent Salomonsson,Nils-Eric Andersson,Ales Svoboda,Anders E W Jarfors

doi:10.3389/fmats.2020.534385

Kent Salomonsson, Nils-Eric Andersson + Show 2 more

Open Access

https://doi.org/10.3389/fmats.2020.534385

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Abstract

A finite element analysis of a complex assembly was made. The material description used was a physically based material model with dislocation density as an internal state variable. This analysis showed the importance of the materials’ behavior in the process as there is discrepancy between the bolt head contact pressure and the internals state of the materials where the assembly process allows for recovery. The end state is governed by both the tightening process and the thermal history and strongly influenced by the thermal expansion of the AZ91D alloy.

Highlights

Modern products are commonly complex assemblies of parts made from different materials made by different processes to provide the desired function
The assembly process can involve several steps involving tightening and test running of the equipment and retightening to avoid issues that the screw is getting loose after delivery to the customer
It can be noticed that the contact pressure is highest near the threading and lesser at the outer edge of the bolt head. This is a clear indication that there is an elastic interaction and that the distance from the threading increases the area of the bolt, and as such, this should be proportional to the inverse of the square of the distance from the threading

Summary

INTRODUCTION

Modern products are commonly complex assemblies of parts made from different materials made by different processes to provide the desired function. Apart from these mechanical boundary conditions and loads, a temperature load was applied. Deformation of metals is commonly described by empirical equations, relating flow stress to plastic strain, strain rate, and temperature. Dini et al (2017) presented a dislocation density based constitutive model, including the effects of microstructure scale and temperature to predict flow stress of as-cast AZ91D alloy. This model is the basis for the current work.

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT