Body Over Wedge Hydraulic Grips

The hydraulic grips are double acting and are used for symmetrical gripping.

Positively driven jaws enable reproducible gripping of the specimen. The symmetrical design and high degree of stiffness of the main body of the grips make them ideal for tests in which strict requirements are placed on the alignment of the specimen to the test axis.

Hydraulic grips

Key Advantages and Features Hydraulic Grips

All of the components work together perfectly so you can rely on accurate, reproducible, repeatable and traceable testing results every time.  

Advantages and features

  • Hydraulic grips have an eccentric piston shape with a long piston stroke, achieving a deep clamping surface position and a large opening width.
  • The alignment of the jaws, specimen grips, and piston facilitates gripping of short specimens as well.
  • Defined force application ensures optimum gripping of sensitive materials.
  • Contact pressure can be reproduced exactly
  • Specimen grips can be installed in testing systems at three different angle settings (0°, 45°, and 90°).
  • T-slots in the lower part of the basic body serve as a mounting for the T-slot system, enabling the accommodation of smaller load cells, specimen grips, test tools, and fixtures (except hydraulic grips, type 8392, Fmax 10 kN).
  • Prismatic jaws (jaws with V-slots) can be rotated and have two-fold use: For round and flat specimens or for round specimens with various diameters (jaws with crosswise arranged V-slots)
  • The upper and lower grips can be opened and closed either individually or together via remote control or PC.
  • The ratio between gripping and tensile forces can be adjusted individually, ensuring that the specimen is held securely (at maximum tensile force approximately double gripping force is required).
  • Hydraulic grips are designed to offer optimal specimen feeding.
  • An adjustable, scaled stop ensures precise vertical specimen gripping for manual special feeding.
  • For easier specimen centering, a centering stop can be used.
  • For safety reasons, specimen tongs can be used to insert the specimen.

Operating principle 

The oil pressure is set at the hydraulic power pack according to the required closing pressure for the specimen grips. The control unit controls the closing and opening procedure separately for the top and bottom specimen grips.

Furthermore, the closing procedure is divided into a closing phase and gripping phase when a a universal hydraulic power pack is used. In the closing phase, the specimen is initially held on the upper end for safety reasons. During gripping, the full gripping force is applied. The force value is based on the expected tensile force.

Double-sided actuators

All hydraulic grips are equipped with double-sided actuators. This means the specimen grip opens hydraulically and not by means of spring return mechanism. The closing and opening pressure can be adjusted.

In contrast to single-acting actuators that open by means of a spring return mechanism, double-sided actuators ensure that the specimen grips always open safely . This also applies if the specimen is crooked or jammed. Additionally, the full opening stroke is not necessary because the opening procedure can be interrupted at any point using the Stop button. The opening stroke can be adjusted according to thickness. Especially with thin specimens, the test time is reduced and the risk of pinching parts of the body is minimized.

Single and double-sided closing specimen grips

Single-actuator hydraulic grips can be used for the symmetrical and asymmetrical gripping of specimens (for example, for shear tests). The thickness of the specimen is set by means of screw unit.

The single-actuator hydraulic grips are also available with a tandem cylinder to enable uniform force application to the specimen (especially suitable for tests on fabrics, textiles and geotextiles).

Double-actuator hydraulic grips always close symmetrically with respect to the tensile axis. This means the specimen is gripped in a precise axial position, thereby eliminating the need for thickness adjustment.

T-slotted system

The T-slotted system makes it possible to accommodate small load cells, specimen grips, test tools, and fixtures quickly, without having to dismantle the specimen grips.

T-slots are integrated in the gripping area of the specimen grip. These serve as mounts for the T-slotted mounting. The T-slotted mounting is clamped there. Other fixtures can now be mounted, saving time needed to mount other tools and fixtures.

197143
197204

Applications

  • Specimen material:
    Metals, composites
  • Specimen shape:
    Round and flat specimens
  • Type of loading:
    Tensile, compression, alternating load

Advantages and features

  • The constant gripping force allows for repeatable test results.
  • Reliable testing results are guaranteed with the optimal interaction between the hydraulic power pack, the electronics, and the testing software. The force-zero control prevents unwanted forces on the specimen during the gripping process.
  • The symmetrically closing jaws save time required for adjusting to varying specimen thicknesses and ensure that the specimen is held exactly in the test axis.
  • Excellent reproducible grip position and specimen alignment to the test axis Ideal for tests on specimens which are sensitive to transverse forces
  • No differential movement of jaws with increased test load (parallel-clamping)
  • Fast and easy insertion of specimen due to the ergonomic and open design.
  • Accurate test results along with a high cycle rate that is made possible by central insertion of the sample with the aid of an easily adjustable centering stop.

Function description

Positively driven jaws enable reproducible gripping of the specimen. The symmetrical design and high degree of stiffness of the main body of the grips make them ideal for tests in which strict requirements are placed on the alignment of the specimen to the test axis.

Technical overview of body over wedge hydraulic grips

Technical data, Fmax 100 kN

Item No.

072865[1]

072868[1]

072869[2] [1]

Type

8594

8594

8594

Test load Fmax

100

100

100

kN

Operating principle/identification

Wedge action

Wedge action

Wedge action

Operating pressure, max.

210

210

210

bar

Gripping force, max. at 210 bar

168

168

206

kN

Dimensions

Height (Opened)

266

345

514 (lower), 902 (upper)

mm

Outside diameter (at head)

200

200

200

mm

Gripping travel

Dependent upon the jaw

Dependent upon the jaw

Dependent upon the jaw

Opening width, max. with jaws

Flat jaws

39

39

39

mm

Prism jaws

24

24

24

mm

Gripping of the specimen

The specimen must be gripped with at least 2/3 of the jaw height

Weight per specimen grip, approx.

62.5

56.6

93 (lower), 113.6 (upper)

kg

Connection interface

Flange

Mounting stud

Flange

Connection

Ø TK 220

Ø 60

Ø TK 220

mm

Coolant connection

-

-

Hose connector 1/8

Condensed water connection

-

-

Hose connector 1/8

Ambient temperature

+4 ... +35

+4 ... +35

-70 ... +250

°C

Scope of delivery

2

2

2

pieces

  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09
  1. For specimen grip up to 250 °C a coolant connection and a condensed water connection are required.

Technical data, Fmax 250 kN

Item No.

072871[1]

072881[1]

071955[1]

Type

8594

8594

8594

Test load Fmax

250

250

250

kN

Operating principle/identification

Wedge action

Wedge action

Wedge action

Operating pressure, max.

210

210

210

bar

Gripping force, max. at 210 bar

478

478

478

kN

Dimensions

Height (Opened)

339.7

408.7

627 (lower), 931 (upper)

mm

Outside diameter (at head)

280

280

280

mm

Gripping travel

Dependent upon the jaw

Dependent upon the jaw

Dependent upon the jaw

Opening width, max. with jaws

Flat jaws

40

40

40

mm

Prism jaws

30

30

30

mm

Gripping of the specimen

The specimen must be gripped with at least 2/3 of the jaw height.

Weight per specimen grip, approx.

102

113

160 (lower), 179 (upper)

kg

Connection interface

Flange

Mounting stud

Flange

Connection

Ø TK 220

Ø 60

Ø TK 220

mm

Coolant connection

-

-

Hose connector 1/4

Condensed water connection

-

-

Hose connector 1/8

Ambient temperature

+4 ... +35

+4 ... +35

-70 ... +250

°C

Scope of delivery

2

2

2

pieces

  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09
Hydraulic wedge grips for servohydraulic testing machines

Body Over Wedge for servohydraulic testing machines

The "body over wedge" hydraulic grips for servo-hydraulic testing machines provide a high level of operating convenience.

When used with servo-hydraulic testing machines they are connected to the existing pressurized oil supply. A small power pack is required for use in static materials testing machines.

Advantages and features of hydraulic specimen grips for servohydraulics

  • Suitable for static tensile and compression tests and for fatigue tests under pulsating and alternating loads
  • Optionally available for superimposed torsion loading
  • Nominal forces 25, 100, 250 and 500kN
  • Interchangeable jaws for flat and round specimens of different dimensions
  • Radial jaw guides prevent unwanted axial stresses in the specimen
  • side-opening design for easy specimen change
  • adjustable gripping pressure for ‘soft’ specimens such as wood and plastics.

Technical data, Fmax 25 kN

Wedge grips

Item No.

1002919

1002920

Dynamic nominal force

±25

±25

kN

Torsional moment Mmax

±250

±250

Nm

Temperature range

+4 to +35

-70 to +250

°C

Design pressure

210

210

bar

Specimen diameter, max.

16

16

mm

Specimen thickness, max.

14

14

mm

Installation height

166

[1]

mm

Specimen grip diameter

110

110

mm

Weight per grip

8

10

kg

Connection size

Ø70; 6 x M8

Ø70; 6 x M8

  1. Upon request: the height depends on the temperature chamber used.
  • Specimen grips consist of 2 grip heads
  • Set of jaws and grip control unit additionally required

Technical data, Fmax 100 kN

Wedge grips

Item No.

088933

088935

Dynamic nominal force

±100

±100

kN

Torsional moment Mmax

-

-

Nm

Temperature range

+4 to +35

-70 to +250

°C

Design pressure

210

210

bar

Specimen diameter, max.

24

24

mm

Specimen thickness, max.

26.5

26.5

mm

Installation height

232

[1]

mm

Specimen grip diameter

200

200

mm

Weight per grip

31

67

kg

Connection size

Ø105, 6 x M10

Ø 105; 6 x M10

  1. Upon request: The height depends on the temperature chamber used.
  • Specimen grips consist of 2 grip heads
  • Set of jaws and grip control unit additionally required

Technical data, Fmax 250 kN

Wedge grips

Item No.

088934

088936

Dynamic nominal force

±250

±250

kN

Torsional moment Mmax

-

-

Nm

Temperature range

+4 to +35

-70 to +250

°C

Design pressure

210

210

bar

Specimen diameter, max.

30

30

mm

Specimen thickness, max.

30

30

mm

Installation height

325

[1]

mm

Specimen grip diameter

280

280

mm

Weight per grip

90

190

kg

Connection size

Ø165; 12 x M16

Ø165; 12 x M16

  1. Upon request: The height depends on the temperature chamber used.
  • Specimen grips consist of 2 grip heads
  • Set of jaws and grip control unit additionally required
Top