DESIGN OF A FATIGUE MACHINE FOR THIN MEMBRANES E. ALACA, M. T. A. - - PowerPoint PPT Presentation

DESIGN OF A FATIGUE MACHINE FOR THIN MEMBRANES

• E. ALACA,
• M. T. A. SAIF, H. SEHITOGLU

FRACTURE CONTROL PROGRAM

October 9, 2001

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

BIAXIAL TESTING

• NEW TESTING APPARATUS

– MONOTONIC and – FATIGUE TESTING OF THIN FILMS

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

input

• utput

thin film pressure transducer piezo actuator wafer fluid chamber amplifier monitor piston

Feedback control drives piezo. displacement data pressure data

laser sensor and camera

TESTING APPARATUS

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

A B C D E F G A:

Laser Sensor

B:

Specimen

C:

Piezo Actuator

D:

Fluid Chamber

E:

Multi-axis Stage

F:

Pressure Transducer

SPECIMEN FABRICATION

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

25 mm

specimen specimen holder

MONOTONIC RESPONSE

4.6 µm-thick polyimide film

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 σ/k 12 10 8 6 4 2 σ0/k 1.72439 (ν=0.3)

k=(E/4)(pa/Eh)

2/3

ν=0.3

ν=0.4 ν=0.2

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

FATIGUE RESPONSE

4.6 µm-thick polyimide film

0.20 0.15 0.10 0.05 0.00 pressure [MPa] 145 140 135 130 125 mid-point deflection [µm] Diameter = 2 mm maximum pressure minimum pressure cycle 301 cycle 701 15.7 µm

0.30 0.25 0.20 0.15 0.10 0.05 0.00 pressure [MPa] 180 120 60 time [s] 140 130 90 80 mid-point deflection [µm] pressure mid-point deflection

FRACTURE OF 150 nm-THICK Al FILM ON 4.6 µm-THICK POLYIMIDE SUBSTRATE

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

“Mud cracking” commonly

• bserved in ceramic coatings,

drying coffee-water mixtures, starch-water mixtures,volcanic rocks, desiccating mud and clays. Vibration isolation and remote focusing make in-situ microscopy possible.

DETERMINATION OF THE CRITICAL STRESS INTENSITY FACTOR FOR 150 nm -THICK Al

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign

G = 1 2 1− ν f

2

( )

hσ

2

Ef πg(α,β)

Beuth, Int. J. Solids Structures, 1992

Steady-state channeling of isolated, straight cracks takes place at p = 0.235 MPa. 1. 2.

KI

c = 1.670MPa m

CONCLUSION

• New apparatus to conduct fatigue testing on

thin films.

• Elastic properties are extracted from

monotonic tests.

• Critical stress intensity factors can be

determined for thin films using in-situ microscopy.

Department of Mechanical and Industrial Engineering University of Illinois at Urbana-Champaign