The gripping force applied to a test specimen by a grip is determined by hydraulic pressure supplied to the grip. The ideal gripping force is large enough to securely grip the specimen but low enough to minimize damage or deformation of the specimen and to prevent specimen slippage during the test.

In the formulas below
A = Area of the grip piston (cm2 or in2)
L = Maximum axial load applied to the specimen (kN or lbf)
P = Grip supply pressure (MPa or psi)
T = Torque (N-m or lb-in)
D = Diameter of test specimen (mm or in)

Fatigue and monotonic testing
To determine the hydraulic pressure required you need to know the maximum axial load to be applied to the specimen for the test. Calculate the minimum hydraulic pressure required:

For monotonic testing
P = 1.04 x L / A

For fatigue testing
P = 12 x L / A

Axial-Torsional testing
To determine the minimum hydraulic pressure required to grip round specimens for axial/torsional testing you need to know the maximum torque to be applied to the specimen for the test. Calculate the minimum hydraulic pressure required:
P = 7.7 x T / A x D

304 Series Load Frame

Designed specifically to provide tension-compression techniques as well as fatigue testing or high rate uses. The 304 Series Load Frames offer a 4-column symmetrical construction with a fixed-platen and moveable crosshead. Typical applications include

  • Cyclic material testing
  • Application of precision force
  • Fatigue testing

These freestanding, fatigue rated load frames come standard with 6 inch (150 mm) stroke lengths and force ratings from 110 Kip (489 kN) through 550 Kip (2,447 kN) with larger units designed and built to meet specific applications. Units feature durable metal base cabinetry and require no tie downs. Advanced design, quality components, and variety of options makes the 304 Series Load Frame your best choice for your testing applications.

  302 Load Frame

Features

  • Smooth, chrome plated columns — 304 utilizes two smooth, chrome plated columns to provide long life and easy crosshead position changes.

  • Infinitely adjustable crosshead — The crosshead is vertically adjustable with infinite resolution. Position of the crosshead is maintained free of backlash by friction clamp locks.

  • Hydraulic crosshead controls — Hydraulic crosshead positioning is standard on all models. A panel controls crosshead movement, using simple controls you unlock, raise or lower and lock the crosshead. The design ensures a sudden loss of hydraulic power will not result in any unwanted crosshead motion.

  • Extremely accurate alignment — The actuator rod and load cell are concentric within .0015 inch @ 15 inches and .002in/ft thereafter.

  • Internal Displacement transducer— The actuator has a co-axially mounted LVDT in the piston rod.  The design protects the LVDT and insures accurate displacement signals for the control system.

  • Extremely rigid construction — No intermediate threaded joints or compression joints are utilized and the load is transmitted directly into the crosshead during testing.

Options

  • Hydraulic crosshead locks — Hydraulically operated crosshead locks are available on all models.

  • Vibration isolation mounts— Vibration or dynamic testing can produce unwanted noise and vibration that can be transmitted to the laboratory floor. Isolation pads under the load unit help reduce noise and dampen vibrations.

  • Safety enclosure — A safety enclosure can be fitted around the test area to protect the operator during destruction testing.

  • Crosshead mount actuator — A crosshead mount actuator is available as an option on all models.

  • Actuator options  — Different actuator displacements and valves are available, as well as custom force ratings. Service Manifolds, servo-valves and hydraulic power supplies are sized and selected based on application.

  • Accessories — Choose from a wide variety of grips, fixtures, extensometers, larger power supplies and various load cell force ratings.