Analysis of a Lifting Fixture to Hold a Steel Mandrel Horizontally from one End Support Page: 3 of 17
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Calculation of Allowable Material Stresses:
The maximum allowable stress on any material in the lifting system is 0.33 x Yield Stress according to
ASME B30.20 - Below-The-Hook lifting devices(2). The fixture brackets are constructed using a mild steel
which is assumed to have a yield strength of 30,000 psi. The welds in the mandrel are also assumed to
have a yield strength of 30,000 psi. The brackets are attached to the base plate using ANSI Grade 5 bolts
with a yield strength of 120.000 psi('. The base plate is constructed of Alumunum to reduce the overall
weight, however it has no significant stresses due to its large size. According to the above guidelines, the
maximum allowable stress for the steel and welds in the fixture is 10,000 psi and 40,000 psi for the
Stresses on the Mandrel Web Due to the Lifting Fixture:
The lifting fixture brackets are inserted into the top openig of the end support web, see Figures 1 and 2.
The mandrel then sucks horizontally out from the lifting fixture and puts a moment on the lifting fixture.
The moment creates a pullout force on the end support web where the lifting fixture brackets attach. The
pullout force on the support web is equal to the weight of the mandrel times half the length divided by the
mandrel diameter. The end support web is attached to the I.D. of the mandrel using /" fillet welds that are
2 inches long every 4 inches around the circumference. The shear stress on the weld is the pullout force
divided by the area of the weld. The pullout force calculated in Table 2 assumes that all of the load is
transmitted through only one of the skip welds. The shear stress in the weld is then calculated. For each
case listed, the stress in the weld is less than the maximum allowable stress of 10,000 psi
Table 2. Shear stresses in the mandrel web due to potential web pullout.
MANDREL MANDREL TOTAL PULLOUT STRESS IN
OUTER HALF MANDREL FORCE ON WELD
MANDREL # DIAMETER LENGTH WEIGHT WEB 2" X 1/4"
1 15.156 in 38 in 604 lbs 1514 lbs 3028 psi
2 19.018 38 790 1578 3156
3 22.864 55 1,442 3469 6938
4 26.738 55 1,757 3614 7228
5 30.602 55 2,088 3752 7504
6 34.464 55 2,440 3894 7788
7 38.326 55 2,813 4037 8074
8 40.292 55 3,010 4109 _ 8218
Stresses on the Lifting Fixture Bracket:
The lifting fixture brackets (dwg #'s 3823.113-MC-372383 and 3823.113-MC-37241 1) are used to support
the mandrel at the end support webs. The forces and stresses on the brackets are calculated:
Bracket for Mandrels # t and #2.
The maximum shear stress on the bracket due to gravity is the weight of the mandrel divided by the cross
sectional area of the bracket. The weight of mandrel #2 is 790 lbs and the cross sectional area of the
bracket is 2.26 inch- producing a stress in the bracket of 350 psi.
The maximum shear stress on the bracket due to the moment of the mandrel is the web pull out force
divided by the cross sectional area of the bracket. The pullout force for mandrel #2 is 1,578 lbs and the
cross sectional area of the bracket is 1.5 inch2 producing a stress in the bracket of 1,052 psi.
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Cease, H. Analysis of a Lifting Fixture to Hold a Steel Mandrel Horizontally from one End Support, report, April 7, 1999; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc843304/m1/3/: accessed November 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.