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MIT. Feasibility of using Earth-Bounded NDT Techniques for the Space Environment. Explain the presentation is about NDT of welds done in space. V. Nikou, P.F. Mendez, K. Masubuchi & T.W. Eagar Massachusetts Institute of Technology, Cambridge, USA. MIT. Inspecting things in space is difficult.

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slide1

MIT

Feasibility of using Earth-Bounded NDT Techniques for the Space Environment

Explain the presentation is about NDT of welds done in space

V. Nikou, P.F. Mendez, K. Masubuchi & T.W. Eagar

Massachusetts Institute of Technology, Cambridge, USA

slide2

MIT

Inspecting things in space is difficult

February 1st, 2003

Space Shuttle Columbia

General NDT in space: NASA 1980?

NDT of welding in space: this work

The Need for Non Destructive Testing in Space

  • Welding in space is at an advanced stage:
    • Russians did it in space
    • Japanese and Americans did it on planes
    • NASA has a prototype design
  • Weld requirements: especially strict in space
  • Space structures: sufficient life to make economic sense
  • NDT in space only considered for monitoring
slide3

MIT

Summary

  • Space Environment
  • Review of available NDT methods
  • Evaluation of NDT methods
  • Recommendations

What is this?

slide4

MIT

The Space Environment

  • Zero Gravity:
    • Low Gravity condition (g/g0=10-5 to 10-7)
    • Physics change (density, convection, surface tension)
  • Space Vacuum:
    • Mean pressure @ 250-500Km in the order of 10-9 Atm
    • Thickness of residual atmosphere is very small
    • Local pressure gradients instantaneously equalized
  • Space Radiation:
    • Vacuum Ultraviolet radiation (VUV)
    • Wide temperature variations on structures (–1100C to 1500C)
  • Composition of space environment:
    • Atomic Oxygen (very corrosive)
    • Atomic Hydrogen
    • Space Debris
    • Meteoroids

What is this?

slide5

MIT

NDT Methods Reviewed

  • Visual (easy, less accurate)
  • Radiographic (very sensitive, portable, radiation hazard)
  • Ultrasonic (space-graded compounds needed as couplants)
  • Magnetic (surface defects, dry method OK)
  • Penetrant (can operate only up to 10-5 Atm)
  • Electrical-Eddy Current (surface and shallow crack detection)
  • Acoustic Emission (has to be detected in real time, better for monitoring)
slide6

MIT

NDT Methods Reviewed

Use a consistent order for sorting them.

  • Visual
  • Radiographic
  • Ultrasonic
  • Magnetic
  • Penetrant
  • Electrical (Eddy Current)
  • Acoustic Emission
  • Radiographic
  • Magnetic
  • Ultrasonic
  • Eddy Current
slide7

MIT

Flaw

detection

Weld

geometry

Materials

NDT

(Welding - Monitoring)

Safety

Versatility

NDT Techniques Performance Factors

  • Flaw Detection:
  • Minimum detectable flaw size
  • Maximum detectable flaw depth
  • Materials:
  • Al
  • Ti
  • Metal Matrix Composites (MMC)
  • Austenitic Stainless Steel
  • Martensitic Stainless Steel
  • Geometry of welds:
  • Brazing (B)
  • Electron Beam Welding (EBW)
  • Laser Beam Welding (LBW)
  • Arc Welding (AW)
  • Resistance Welding (RW)
slide8

MIT

NDT Methods Evaluation

Explain why in little bullets

  • Eddy Current: most suitable
    • Why?
  • Ultrasonic: maybe for MMC
    • Why?
  • Radiographic:
    • heavy
  • Magnetic: less suitable
    • Why?
slide9

Conclusions

  • No welding in space without NDT of welds
  • Review of NDT methods for welds made in space
  • Earth-bounded NDT processes could be used in space
  • Eddy-Current most all-around suitable technique
  • Ultrasonic suitable for MMC
  • Future work involves examining the defect generation of specific

welding methods