PS fork equipped with 8 semiconductor (4 by arm) strain gauges

G1

G2

G3

G4

G5

G6

G7

G8

10

50

77

10

50

77

26 26

Gauges location

Gauges G4 and G8 are bonded in the fork shaftGauges G2, G3, G6 and G7 are bonded in the wings of the arms of the forkGauges G1 and G5 are bonded in the flexible flat parts of the fork

Gauges location

Gauges G4 and G8 are mainly sensitive to the twist of the shaft in X axisGauges G2, G3, G6 and G7 are mainly sensitive to the deflections in Z directionGauges G1 and G5 are mainly sensitive to the deflections in X direction

G1

G2

G3

G4

G5

G6

G7

G8

10

50

77

10

50

77

26 26

X

Y

Z

Gauges location

G4

G2

G3

G1

Gauges location in the right arm of the fork. Gauges located in the left arm are symmetric to these gages as follow:

G1 and G5G2 and G6G3 and G7G4 and G8

Gauges location

IN

OUT

OUTPOSITION

IN POSITION

The strain gauges G2, G3,G6 and G7 are located in thisside of the fork

IN movement produces compression (resistance decrease) in gauges G2, G3, G6 and G7.OUT movement produces extension (resistance increase) in gauges G2, G3, G6 and G7.

The following setup has been built in order to calibrate the strain gauges installed on the fork. The goal of the calibration processis to collect the suitable data about the behaviour of the system to reproduce the deformations on the fork during the scan by mean ofthe variation of resistance measured in the strain gauges.

2

3

5

4

A progressively increasedknown load is applied in this pointof the arm and the deflections in thefork are measured by means of4 dial indicators

Gauges calibration - Deflection measurements

Shows the setup for gauges calibration in the right are of the fork, an equivalentsetup has been used in the left arm of thefork.

2

3

4

5

Gauges calibration - Deflection measurements

A lever fixed to the fork axisprovides information about the twist ofthe fork shaft.

Gauges calibration - Deflection measurements

d1

d2

d9

50

d3

d6

d7

d8

d10

d4

d5

30

35

48

Gauges calibration - Deflection measurements

Gauges calibration - Deflection measurements

Typical gauge calibration plot

Gauges calibration - Deflection measurements

Typical gauge calibration plot

Tension variation the right arm gauges IN movement

Results

Tension variation the right arm gauges OUT movement

Results

Displacement in point d1 based in the variation of resistanceof G1, IN movement.

Displacement in point d2 based in the variation of resistanceof G3, IN movement.

Results

Displacement in point d1 based in the variation of resistanceof G1, OUT movement.

Displacement in point d2 based in the variation of resistanceof G3, OUT movement.

Results

Deflection measurements

Deflection measurements

Next

• Perform measurement in the 2nd arm• Perform measurement in both arms at the same time with and without wire• Find correlation between displacements in the arms and the pattern of movement• Perform measurements in vacuum on both arm and wire resistance• Perform measurements using a more rigid fork• Introduce measure data in an analytical model of the wire to find a correlation

between wire resistance• variation and wire elongation due to vibrations• Compare different motion patterns