[TYPE THE COMPANY NAME]
Welding assignment
UNSW MECH3110
Raniya Parappil z3331030
02-Oct-12
Introduction
Sugar refining mill is installing vibrating screen units for grading of the sugar into commercial sizes.
The unit is supported by brackets that are welded to columns. The screen units are provided with
vibration isolation mountings and with
internal counterbalancing so that the load may
be considered static and uniformly distributed
between the four mounting. A reversing
horizontal force equivalent to 0.15g peak
acceleration occurs in the longitudinal
direction at the support brackets [see figure
on the left]. The loads exerted on the column
are calculated. The screen free body diagram
and the bracket A and B free body diagram are
drawn. A free body diagram for each bracket
in the x-y & x-z planes will be constructed to
determine the maximum bending moment and
other crucial loadings. The loadings exerted
onto the weld outline sections were calculated,
using iterations. Material for the beam must be chosen from a catalogue
[Figure left shows Side view of the screen unit
layout.]
Design calculations, sketches of brackets and layouts as required are to be presented for approval by the
client's engineer. The bracket A is mounted with an angle therefore it has torsion and bracket is
perpendicular to the screen, resulting in no torsion formed. Bracket B is perpendicular to the column
which will be cantilever beam with a bending moment due to the screen’s loading. The brackets are the
primary focus for this analysis as the welding calculations are performed after the static analysis from
the screen to the bracket.
SPECIFICATIONS



Number of screen units to be installed - 4
Mass of screen unit and fittings - 7000 kg.
Location of Centre of Gravity - centrally between mounting feet and at same height as mounting
surface

Size of Columns - 310 UC 118
[Figure above: Possible bracket detail.]
Welding:
[Shingley’s textbook, Mechanical Engineering Design]
The points that were analyzed on the beam were (the following points were considered to be the critical
points
Discussion
The factor of safety of the beam was considered to be 2. The loads on the screen supports were
calculated and the shear force and bending moment diagram were then drawn. After finding this the
maximum bending moment for bracket A and B in the planes were found. Free body diagrams were
designed for both x-y & x-z. The material of the beam was selected keeping in mind the ASI standards
and the section n the x and y plane were found from the One steel catalogue. A general outline on
how the shear stress and bending stress will act on the bracket A and B were drawn. A suitable
universal beam was selected from the ONE STEEL catalogue. The 530 UB 82 was chosen for being the
beam with the smallest flange width that could accommodate the flat plates. The beam had the lightest
weight, when compared to the other beams that fit into the design constriction. The bean had to chosen
such that, the flange width was between 200 to 307mm. The forces and moment at the weld were
calculated with addition to the moment of inertia, Ju, shear force per mm, bending force /mm and
torsion/ mm and the angle between the torsion forces were successfully calculated. For the purposes of
safe design, a worst case scenario was taken.
After choosing the type of load (parallel or transverse), the h (weld size was calculated using the
formula:ℎ=
ℎ=
3√2𝑓𝑝 𝑛
𝑆𝑢
3 × 1.21𝑓𝑡 𝑛
𝑆𝑢
Then the iteration was used to find the weld size for bracket A and B until the results converged.
iteration number
1
2
3
4
5
6
7
8
9
10
average weld
1
1.85
1.63
1.66
1.662
1.66
1.656
1.656
1.656
1.656
weld size A
2.578
1.87
1.91
1.932
1.9073
1.9171
1.9171
1.9171
1.9171
1.9171
weld size B
1.603
1.3865
1.4094
1.4075
1.4092
1.4123
1.4123
1.4123
1.4123
1.4123
Ultimate strenght MPA
250
300
350
400
450
500
weld size for A
4.970677828
4.142231523
3.550484163
3.106673642
2.761487682
2.485338914
weld size for B
3.0910176
2.575848
2.207869714
1.931886
1.717232
1.5455088
factor fo safety
1
2
3
4
5
6
7
8
9
10
11
12
weld size A
1.2890762
2.5781524
3.8672286
5.156304801
6.445381001
7.734457201
9.023533401
10.3126096
11.6016858
12.890762
14.1798382
15.4689144
weld size B
0.801612448
1.603224896
2.404837344
3.206449793
4.008062241
4.809674689
5.611287137
6.412899585
7.214512033
8.016124481
8.817736929
9.619349378
Conclusion:
The welding size of the beams was calculated successfully. The screen FBD diagram was drawn to obtain the
shear diagram and bending moment diagram. The calculations are done showing the FBDs in the required
planes. A free body diagram for each bracket in the x-y & x-z planes has been constructed. The
maximum moment for each bracket was calculated in order to get other values which was required for
finding the weld size. The factor of safety is assumed in the beginning to calculate the bending moment and
shear forces. The critical points of the beam labeled as A B C D E F are taken and analyzed. For each point the
shear force, bending force, torsion, and angle were found. A suitable material is then found taken to be structural
steel. The weld sizes for both brackets are found using iteration method in excel. Although the weld size may
seem small, costs will be lower and the weld size can be modified if necessary by the client’s needs,
by changing factor like factor of safety, ultimate tensile strength. the engineering drawing was hence
drawn for give the client a basic view of the weld and to put the design into a visual form.