MTS 318 Load Unit - Manual (Page 22)

318 Load Unit 22 Introduction
For the most accurate high frequency test results, use a load unit with a fatigue
rating that is larger than its actuator’s force rating.
For example, a Model 318.25 Load Unit with a 55 kip fatigue rating and a 22 kip
actuator will have smaller deflections than a Model 318.10 Load Unit with a 22
kip fatigue rating and a 22 kip actuator.
Spring rates are determined at each load unit’s full fatigue rating with its
crosshead raised 1270 mm (50 in.) above the baseplate.
The Stiffness Graph shows how stiffness is affected when the height of the
crosshead is changed.
A
B
D
C
D EFLECTIONS M ODEL 318.10
100 K N/22 KIP
M ODEL 318.25
250 K N/55 KIP
M ODEL 318.50
500 K N/110 KIP
A - B base 0.15 mm 0.006 in 0.18 mm 0.007 in 0.20 mm 0.008 in
B - C columns 0.10 mm 0.004 in 0.15 mm 0.006 in 0.18 mm 0.007 in
C - D crosshead 0.13 mm 0.005 in 0.25 mm 0.010 in 0.28 mm 0.011 in