Improved fibre tensile tester

status quo

• Abbe errors

• non-linear force sensor

• non-symmetric design

• poot component quality

• not student proof

• parasitic motions

• not vacuum ready

• force sensor elongation not measured

• unstable sample length adjustment

quantative error analysis

• error motions moving stage: parasitic motion and misalignment (y and Rz)

• deformations due to force applications: significatn difference between present and measured deformation in x direction

• deformation of force sensor: significant misalignment and parasitic motions

introduces measurement uncertainty and sample disturbace

force sensor

• stiffness based sensor, measruing the displacement

• linear and vacuum ready, works only in the x directions

• constrained in 5 DOF

strain application

• parallel leaf spring motion stages, movieng over center position

loadcell design

• parallel leaf spring design

• position and stiffness based force measurements

• protective end stops

• FEM design

strain application system

Preloaded coil sping drives the leaf spring to apply strain. Since the spindle works only in on directions, the spring takes care of the other one

Gearbox details

• reduces speed

• use of a standard, compact motor

• decouples the motor from the spindle

Capacitive probe mounting

• non-contact

• high resolution

• vacuum ready

• can be integrated into a small assembly

safety and practicality measurements

• cable routing

• levelling feet

• mounting surfaces

• travel locks

verification

• stage alignment: both sides agains a common reference (5 DOF)

• centered delta between stages