Update of straw creep measurements Chiho Wang Seog
- Slides: 9
Update of straw creep measurements Chiho Wang, Seog Oh Duke University
“Fixed Tension” Creep Measurement • PPG straws: 155 cm long, 5 mm ID, 18 um wall (6μm Al coated Mylar outer layer + 6μm Al+Au coated Mylar inner layer + 6 um polyester/urethane adhesive). • Straw properties: § Spring constant k=1. 4 cm/kg § Mylar thermal expansion = 1. 7 E-05/°C (Dupont) § Mylar humidity expansion = 6. 0 E-6/%(RH) (Dupont) • Test condition: 550 gm weight + 18 psi ~ 800 gm tension. • Changed to: 550 gm weight + 0 psi after 120 days. 10/29/12 Chiho Wang, Seog Oh 2
Straw end position vs time Straw lengthening direction Straw end Position (cm) (ref: doc#2277 & 2084 for setup) 10/29/12 Chiho Wang, Seog Oh 3
“Fixed Length” Creep Measurement • Glue straws on a support frame (120 cm) with tensions: § 300 gm, 400 gm, 500 gm, 600 gm. • Measure straw tension by resonant frequency as a function of time. Support Frame Magnet Frequency Speaker Counter Straw Weight Precision Function 10/29/12 generator Chiho Wang, Seog Oh 4
Tension change vs time 0 20 40 60 80 100 120 140 160 180 200 0 str#1 300 g del_T str#2 400 g -50 str#3 500 g Str#4 600 g -100 -150 -200 -250 (without correction for. Chiho temperature & humidity variation) Wang, Seog Oh 10/29/12 5
Tension change vs time 0 20 40 60 80 100 120 140 160 180 200 0 -50 Straws 1 & 2 only AC malfunction Room overheated str#1 300 g str#2 400 g str#3 500 g -100 Str#4 600 g str#1 300 g str#2 400 g -150 str#3 500 g Str#4 600 g Linear(str#1 300 g) Linear(str#2 400 g) -200 Linear(str#3 500 g) Linear(Str#4 600 g) -250 -300 10/29/12 (corrected for temperature & humidity variation) Chiho Wang, Seog Oh 6
Tension change vs time 1, 000 0, 950 T/T 0 str#1 300 g 0, 900 str#2 400 g 0, 850 str#3 500 g 0, 800 Str#4 600 g 0, 750 Linear() 0, 700 Linear() Straws 1 & 2 only AC malfunction Room overheated 0, 650 0, 600 0 20 40 60 80 100 120 140 160 180 200 (without correction for. Chiho temperature & humidity variation) Wang, Seog Oh 10/29/12 7
Tension change vs time 10/29/12 (corrected for temperature & humidity variation) Chiho Wang, Seog Oh 8
Summary • Summary: § Creep trend is similar to previously reported. § It seems that after H and T correction, the data fluctuate more. o do not yet understand. 10/29/12 Chiho Wang, Seog Oh 9
