Selection of material and process.

07010042 R.Jyoti Swaroop07010044 Prudhvi Teja07010045 Pramod J

pR

tt

= pR/t

2a

Design requirementsFunction: contain pressure, pObjective: maximum safetyConstraints: (a) Must yield before break

(b) Must leak before break (c) t small: Reduces mass and cost (d) Shape : Cylindrical (e) Inner Radius and Height of cylinder is

constantFree Variables : Material

M1 = KIc/ys

ys

pRt

M2 = (KIc)2/ys

M3 = ys

Yield-before-break

Condition for Thickness

Leak-before-break

Thin wall, strong

the stress required to active crack propagation

c

Ic

aY

K

Leak-before-fail criterion (leaks can be detected over lifetime)

KIc

Y t

Pressure vessel for HOT ISOSTATIC PRESSING

Material and shape constraintsPressure - 100 MPaYield strength > 100 MPaInner Radius = 0.5 mHeight of Cylinder = 1 m

The leak-before-break criteria Minimum Thickness and strong

M2 = (KIc)2/ysM3 = ys

Yield-before-break (Less preference)M1 = KIc/ys

From charts Steels would be best option and ys = 500 MPa

Calculation of parametersTaking safe factor = 2

Surface area, A = 2πRoh = 3.8 m2

Volume = π (Ro2-Ri

2)h = 0.8 m3

Slender thickness = t/√A = 0.1Weight = ρV = 6400 kg

Ro = Ri + t = 0.7m

Design Constraints for manufacturing processConstraint Value

Material Steel

Sectional thickness, t 200 mm

Density, ρ 8000 kg/m3

Melting Temperature, Tm 1600 K

Surface area, A 3.8 m2

Volume 0.8 m3

Weight 6400 kg

Slender thickness (=t/√A) 0.108

Mean precision ± 1.0 mm

Batch Size, N 10

Shortlisted process

What about the mass constraint???

Processes and commentsProcess Comments

Machining Machine from solid (rolled or forged) billet.Much material discarded, but a reliable product. Hence, not economical.

Hot working Steel forged to thick-walled tube, and finished by machining end faces, ports, etc. Preferred route for economy of material use.

Casting Cast cylindrical tube, finished by machining end-faces and ports. Casting – defects a major problem.

Fabrication Weld previously-shaped plates. Not suitable for HIP. (Useful for larger vessels like nuclear pressure vessels).