UWE Bristol Engineering showcase 2015
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Richard Halladay <br />
Mechanical <strong>Engineering</strong> BEng (Hons) <br />
Project Supervisor <br />
Mrs. Rachel Szadziewska <br />
The Study and Calcula0on of the Pre-‐ Load and <br />
Pre-‐Load Effects Developed In A Bolted Connec0on <br />
What Is Pre-‐load & Why Do It? <br />
Bolts are preloaded in tension to a predetermined level which applies a considerable force between the ma;ng surfaces, known as the <br />
faying surfaces. The slip resistance depends on the coefficient of fric;on between the surfaces and the preload. Thus the prepara;on <br />
and protec;on of the faying surfaces and the installa;on of the assembly are both important in this type of connec;on. In general, non-preloaded<br />
bolts are acceptable for the majority of standard connec;ons as the small amount of slip associated with the clearance hole <br />
in which the bolt is located has no impact on the structure. <br />
Force Development in a Threaded body. <br />
As the applied pre-‐load increases, the center of the body beings to react to <br />
this force. The thread however remains rela;vely unloaded, as can be seen <br />
below. <br />
Preload Tes0ng <br />
The main test of the project was the <br />
pre-‐load test. Below can be see the rig <br />
GA & FEA screen shot. The use of FEA <br />
throughout the project was paramount <br />
in ensuring the rigs were strong enough <br />
for the applica;on. <br />
Project summary <br />
The Primary objec;ve of this inves;ga;on is <br />
to tailor already exis;ng bolt pre-‐load <br />
equa;ons to more specific bolt types. When <br />
calcula;ng the pre-‐load in a bolt, most <br />
common equa;ons are designed to allow for <br />
all types of bolt and finishes. Because the bolt <br />
types and condi;ons are known, any chosen <br />
equa;on can be adjusted to suit specific bolt <br />
types, resul;ng in more accurate equa;ons <br />
for theses bolts <br />
Project Objec0ves <br />
Tensile Tes0ng. <br />
A major part of the project was the tensile tes;ng of the bolts to determine <br />
the bolt yield. This brought up the issue of stress concentra;ons due to the <br />
threads. Below are some images taken from the tests & the test results. <br />
Results. <br />
On the following two graphs can <br />
be seen the torque Vs force <br />
results, taken directly from the <br />
Preload test & then the correc;on <br />
factor graph produced at the end <br />
of the project. <br />
Using various different theore;cal & prac;cal <br />
tests, generate a graph of correc;on factors <br />
based on the fric;on value of the bolt. <br />
Project Conclusion <br />
The final chart of correc;on values produced <br />
from the tes;ng clearly demonstrates the use <br />
of such data, as well as how simply it can be <br />
presented for use in the field. Where the <br />
chart can be improved is through the input of <br />
more data. Not only would this increase the <br />
accuracy of the current points, but would also <br />
broaden the field of informa;on available.
Change language