Transcript an update on the shear loads

NCSX Modular Coil
Joint Load/Stress Calculation
By
Leonard Myatt
Myatt Consulting, Inc.
The Big Picture
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
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Estimates of Bolt Loads with Bonded Flange
Interfaces need to be checked.
MC Global model already quite big.
Need to develop a simple bolt model with
properties (shear & tensile stiffness) similar
to the reference joint designs.
Apply approximation to MC Global model to
determine bolt load distribution.
29 January 2007
MC Joint Analysis
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Process Overview

Import Joint Models from ORNL into ANSYS:
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Apply symmetry, add 30 mil Stycast gap, add
general contact at flange-shim interface
Loading:
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“Joint1” (Double nut on Stud)
“Joint2” (Bolt & tapped flange hole)
Impose lateral deformation (parallel to flange face)
Impose axial deformation (parallel to bolt axis)
Response:
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Lateral force and joint stiffness v. imposed deflection.
Axial joint stiffness (single-value per joint configuration).
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Process Overview, cont’d
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FYI: Report stresses for 25 k-lb lateral load.
Develop simplistic equivalent bolt model for
Global MC simulations.
Incorporate simplistic bolted connection
model into Global MC simulation.
Analysis Units:
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Bolted Joints use English units.
Global MC uses SI units.
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Reference Design
(Courtesy D. Williamson)
Joint2
Joint1
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Expected 30 mil Annular Gap at
Flange Through-Hole Not Shown
MC Joint Analysis
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Set Preload to ~73 k-lbf
Fastener Torque
bolt tensile yield strength
yield criteria
nominal diameter
thread pitch
bolt tensile area
nut factor
applied torque
preload uncertainty factor
min bolt preload
max bolt preload
Fty
D
p
At
K
T
u
Po
Po
85000
0.7
1.375
0.167
1.155
0.2
18897
0.25
51537
85894
psi
in
in
in2
in-lb
lb
lb
NASA Technical Memorandum 106943 used to define Preload Spec
http://gltrs.grc.nasa.gov/reports/1995/TM-106943.pdf
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ANSYS Model, Joint1
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ANSYS Model, Joint2
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Joint1 Bolt Preload
Nominal Preload ~50 ksi
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MC Joint Analysis
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Joint2 Bolt Preload
Nominal Preload ~50 ksi
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Joint1 Force, Deflection & Stiffness
Preload + Transverse Motion
33000
1650
30000
1500
27000
1350
24000
1200
21000
1050
18000
900
15000
750
Force
12000
600
Stiffness
9000
450
6000
300
3000
150
Instantaneous Stiffness, k-lb/in
Transverse Load, lbf
Joint1 Transverse Load, Stiffness v. Motion
Zero Friction at Shim Interface
0
0
0
5
10
15
20
25
30
Transverse Motion, in/1000
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MC Joint Analysis
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Joint2 Force, Deflection & Stiffness
Preload + Transverse Motion
70000
3500
60000
3000
50000
2500
40000
2000
Force
30000
1500
Stiffness
20000
1000
10000
Inst. Stiffness, k-lb/in
Transverse Load, lbf
Joint2 Transverse Load, Stiffness v. Motion
Zero Friction at Shim Interface
500
0
0
0
5
10
15
20
25
30
Transverse Motion, in/1000
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MC Joint Analysis
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Joint1 Contact Stress (S3)
G11 & Stycast Insulating Parts
Stress & Force Vectors, 25000 lb Shear Load
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MC Joint Analysis
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Joint1 Bolt Tension Stress (S1)
Stress from 25000 lb Shear Load
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MC Joint Analysis
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Joint2 Contact Stress (S3)
G11 & Stycast Insulating Parts
Stress & Force Vectors, 25000 lb Shear Load
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MC Joint Analysis
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Joint2 Bolt Tension Stress (S1)
Stress from 25000 lb Shear Load
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Tensile Stiffness of Joints 1&2
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Apply axial loading where bolt hardware
interfaces with flange face.
Calculate tensile stiffness of each joint.
Stiffness values to be used as basis for
developing simplistic joint model for more
precise Global simulation of MC structure.
29 January 2007
MC Joint Analysis
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Joint1 Tensile Stiffness
~5.4 M-lb/in
Check: k(bolt)=AE/L~(1.48in2)(27.6Msi)/6”~7 M-lb/in
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MC Joint Analysis
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Joint2 Tensile Stiffness
~8.8 M-lb/in
Check: k(bolt)=AE/L~(1.48in2)(27.6Msi)/3.5”~12 M-lb/in
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MC Joint Analysis
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Simple Model of Bolted Joint1 for
Equivalent Stiffness Approx.
Stiffness Match Achieved with 2.9” diameter Bolt
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MC Joint Analysis
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Simple Model of Bolted Joint2a
for Equivalent Stiffness Approx.
Stiffness Match Achieved with 2.75” diameter Bolt
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MC Joint Analysis
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A-B Joint Bolt Definition
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Bolt layout drawing
shows 26 bolts at
this A-B flange.
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A-B Bolt Types
(M. Cole FP-STUDS.PPT)
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Bolts 1-9 Defined by Project
(M. Cole FP-STUDS.PPT)
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MC Joint Analysis
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Bolts 10-15 Defined by Project
(M. Cole FP-STUDS.PPT)
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MC Joint Analysis
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Bolts 16-18 Defined by Project
(M. Cole FP-STUDS.PPT)
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MC Joint Analysis
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Bolts 19-26 Defined by Project
(M. Cole FP-STUDS.PPT)
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Application of Equivalent Stiffness Bolted
Joints to Global Model at A-B Flange

Solid PIPE16
elements, with
dimensions to
match calc’d
Joint stiffness,
are added to
each A-B Bolted
connection.
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Top 15 A-B Bolts
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Bottom 11 A-B Bolts
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Analysis Notes
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A significant effort was made to simulate both zero
and finite friction at the A-B flange.
Bolt Preload Load-Step converged OK.
But excessive computer run-time (4+ days for 4%
of EM load) has lead to an alternative approach:
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The AB interface is modeled as sliding and always in
contact (KEYOPT(12)=4) with m=0.2 friction.
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Analysis Notes, cont’d
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The model converges nicely, even with friction.
This approach (sliding without separation) does
not report accurate tensile loads on the bolts.
We may ultimately need to find a way to run the
model with friction and open/closed contact
behavior (keyopt(12)=0) to confirm preload levels
and bolt stresses. (This requires more thought.)
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Global Model Results
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Various Contour Plots of A-B Flange Results:
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Bolt Preload [k-lb or kip]
Bolt Shear Force Range [k-lb or kip] produced
by EM Load cycle. Non-zero value indicates that
the joint is not completely isolated with preload
& modest friction.
Slippage produced by EM Load cycle (~1/2 mm
scuffing at inboard leg)
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Preload [kip] in A-B Flange Bolts
(67 min.<78 Average<81 max.)
Falls within design goal of 52-86 kip
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Shear Force Range in A-B Flange Bolts
from EM Loads (m=0.2, 78 kip Preload)
Max Shear Loads: 1.5 & 2.5 kip, Bolts 25 & 26)
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MC Joint Analysis
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Contact Slippage [m] at A-B Flange From
EM Loading (m=0.2, 78 kip Preload)
In Region of Bolts Only
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Entire A-B Flange Interface
MC Joint Analysis
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Response of AB Flange to EM
Loading (double-click to play AVI)
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MC Joint Analysis
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Observations: A-B Flange
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An analysis with A-B bolt preload at the 78 kip
reference design value and m=0.2 shows:
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Slippage of ~3 mils at AB Bolt #26 produces a 2500 lb
shear load from EM forces. Stresses of 4.5 ksi in the
Stycast and 12 ksi (range) in the #26 bolt can be inferred
from earlier contour plots with 25 kip unit loads. These
seem OK.
A Hybrid joint design (Friction + Collar) seems to be
necessary (consistent with Reiersen recommendation).
Scuffing at the inboard leg of order ½ mm from EM
loads. High-cycle operation may dictate the use of more
robust shear transfer mechanism (keys).
29 January 2007
MC Joint Analysis
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Observations: A-B
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The shortfall in A-B joint bolt #26 frictional
capacity is ~2.5 kip based on an 80 kip
preload and a friction coefficient of 0.2.
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The theoretical friction capacity is 16 kips
The 2.5 kip shortfall can be made up by:
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Increasing m to 0.23, or
Increasing the preload to 93 kip, or
Increasing m to 0.25 and the preload to 74 kip
29 January 2007
MC Joint Analysis
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Analysis of B-C Bolted Flange
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A similar analysis of the B-C flange is
performed.
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Global Model Results, B-C
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Various Contour Plots of B-C Flange Results:
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Bolt Preload [k-lb or kip]
Bolt Shear Force Range [k-lb or kip] produced
by EM Load cycle. Non-zero value indicates that
the joint is not completely isolated with preload
& modest friction.
Slippage produced by EM Load cycle (~0.8 mm
scuffing at inboard leg)
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MC Joint Analysis
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Preload [kip] in B-C Flange Bolts
(61 min.<78 Average<85 max.)
Falls within design goal of 52-86 kip
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Shear Force Range in B-C Flange Bolts
from EM Loads (m=0.2, 78 kip Preload)
Max Shear Loads: 3.1, 8.7 & 6.9 kip, on Bolts 27, 28 & 29)
29 January 2007
MC Joint Analysis
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Contact Slippage [m] at B-C Flange From
EM Loading (m=0.2, 78 kip Preload)
In Region of Bolts Only
29 January 2007
Entire B-C Flange Interface
MC Joint Analysis
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Observations: B-C
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The shortfall in A-B joint bolt #28 frictional
capacity is ~8.7 kip based on an 61 kip
preload and a friction coefficient of 0.2.
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The theoretical friction capacity is 12 kips
The 8.7 kip shortfall can be made up by:
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Increasing m to 0.34, or
Increasing the preload to 105 kip, or
Increasing m to 0.25 and the preload to 84 kip
29 January 2007
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Future Work
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A more thorough analysis of the interface still
requires a traditional contact analysis where
flange separation can occur.
Analyses by others indicate that A-A may be
a more heavily-loaded connection, and
therefore should be evaluated ASAP
[although this is more complex to implement
and still being pondered].
29 January 2007
MC Joint Analysis
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