Analyses of Bolted Joint for Bolt Preload and Shear Load

Analyses of Bolted Joint for Bolt Preload and Shear Load

Two surface interface conditions:

1) Bonded contact surfaces between shim plate and flanges

2) Frictionless contact surface between shim plate and flanges

Two load cases:

Case 1: Shear load of 15 kip

Case 2: Combination of 60 kip bolt preload and 15 kip shear load.

FEA Model

316 SS shim w/ ins.break

Flange stellalloy

A286 hex nut

INCO 718 washer

A286 spherical washer set

G-11CR washer

A286 stud

Fixed support

G-11CR bushing

Coupling Uz

Coupling Ux, Uy, and Uz

Coupling Ux, Uy, and Uz

Assumptions:• Except frictionless shim-flange contact surface, all compressive interfaces under preload are “glued” instead of bonded contacts in order to avoid the contact penetrations that affect the joint stiffness.

• For stability, the G-11 bushings were glued to the flange stellalloy but have frictionless contact with the A286 stud.

• The hex nuts are glued to the stud without any tolerance.

• The spherical washer sets were modeled by equivalent short cylinders.

• The thickness of shim was formed by 1/7 of G-11CR insulation and 6/7 of 316 SS. The equivalent smear material property was assumed.

• The lower flange stellalloy was fixed at the bottom surface. The upper flange stellalloy was coupled in the vertical direction on the top surface nodal points.

• Couples are applied at two side faces of the stellalloy to form a cyclically symmetric model.

• The 60 kip pretension was applied about the mid-height of the stud and the15 kip shear load was applied normal to the side face of upper flange,

• All analyses used the room temperature material propertied as shown on next slide.

Material Properties RT propertiesMaterial A286 Stellalloy G11CR Inco718 Titanium SS316LN Shim

Tensile strength (ksi) 130 82 190 145 900.2% Yield strength (ksi) 85 35 66 157 137 40

Elastic modulus (Msi) 29.1 21.6 2.7 29.6 15.8 28.2 24.56Thermal strain () 0 0 0 0 0 0

Poisson's ratio 0.31 0.294 0.308 0.333 0.294 0.252Elongation 20% 12% 56%

References 1, 2 4 5 5 6

Material Properties 80K propertiesMaterial A286 Stellalloy G11CR Inco718 Titanium SS316LN Shim

Tensile strength (ksi) 166 159 238 226 1830.2% Yield strength (ksi) 97 93 115 186 218 94

Elastic modulus (Msi) 31.1 23.3 3.5 30.8 17.1 30.1 26.30Thermal strain () -2639 -2834 -5500 -2150 -1600 -2760

Poisson's ratio 0.298 0.283 0.307 0.327 0.283 0.243Elongation 60%

References 1 4 7, 8 5 5 6G11CR through thickness properties, yield is in compressionEstimated

Material References1 MIL-HDBK-5H2 ASTM A 453 Grade 6603 NCSX-CSPEC-141-03-144 Minimum properties MCWF test data (F. Malinowski)5 Handbook for SC Machinery6 ITER handbook7 Kasen et al, "Mechanical, electrical, and thermal characterization of G-10CR and G-11CR…"8 Roach, F. "Mechanical properties of insulation for structural analysis", TPX memo 14-12210.3-WSTC/JFROACH

Material Properties

Shear Load - Deformed Shapes with Undeformed Edge ▪ Bonded contact has much smaller displacement than the frictionless contact case

Frictionless contact

Deformed shapeScale factor = 60

Undeformed shape

Bonded contact

Unit in inch

Combined Load - Deformed Shapes with Undeformed Edge

Frictionless contactBonded contact


Unit in inch

Mainly due to bolt shorten for preload

Shear Load - Deformed Shape with Undeformed Edge

Undeformed shape



UsumUy UsumUy

Unit in inch

Combined Load - Deformed Shapes with Undeformed Edge


UsumUy


UsumUy

Unit in inch

Shear Load - von Mises Stress in Flange Stellalloy


high local stress at edge is the combination of the bearing stress and shear stress primarily in the y direction

Unit in psi

Combined Load - von Mises Stress in Flange Stellalloy


high local stress located at the washer bearing surface primarily due to preload Unit in psi

Shear Load - Stress in Stud, Nut, and Washer


SeqvSz


SeqvSz

Unit in psi


Combined Load - Stress in Stud


SeqvSzSeqvSz

Unit in psi

Peak stresses occur at the faces of nuts due to the assumption that stud and nut are bonded

Shear Load - von Mises Stress in Bushing Note: Bushings were glued to the flanges. If they are not glued, the deformed shape will be changed.



Unit in psi


Combined Load - von Mises Stress in Bushing Note: Bushing was glued to flange

Deformed shapeScale factor = 60Unit in psi


Shear load - Contact Pressure on Bushing


Unit in psi


Combined load - Contact Pressure on Bushing


No contact pressure on bushing due to Poison’s effect of the preload on bolt and small shear displacement

Unit in psi

Discussions:1. The analyses intend to observe the structural behaviors of bolt joint subjected to

preload and shear force under the two extreme conditions of the friction between the shim plate and the flange stellalloy.

2. The bonded case has much smaller lateral displacement than the frictionless case.

3. With frictionless case, the lateral displacement is mostly contributed by the shear load. The lateral stiffness of the joint is dominated by the bending and shearing stiffness of the bolt as well as the contact pressure on the bushing.

4. In the bonded case, the majority of shear force transporting between flanges depend on the shear stiffness of shim plate while in frictionless case, they are transferred through bearing on the bushing and bolt hole. This shows the high friction coefficient and larger shim plate improve the joint rigidity.

5. Bonded case produced much smaller stress on all parts of the joint than the frictionless case, that means a much better joint design.

6. The bending stress on the bolt is about 2.0 ksi for 1.0 kip of shear force. Tight fit of the bolt will reduce the bending stress on the bolt.

7. Bearing stresses on the bushing are due to the bolt bending and the gap tolerance. The maximum bearing stress do not occurs at ends of bushings because the bolt bending was restrained by the nuts and washers.

Documents

Analyses of Bolted Joint for Bolt Preload and Shear Load