Double-sided closing hydraulic specimen grips

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.
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.

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Double-sided closing hydraulic grips

Advantages and features

  • Defined force application ensures optimum gripping of sensitive materials.
  • Unwanted forces acting on the specimen are compensated for during the gripping process by Zwick’s "Force Constant Hold" feature when the grips are used in conjunction with ZwickRoell hydraulic power-packs, the testControl electronics, and testXpert III testing software.
  • Small load cells, specimen grips, test tools and fixtures can be quickly accommodated via the optional mounting unit and without having to dismantle the specimen grips.
  • 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)
  • Excentric offset between piston and piston rod allows specimen grips with short clamping lengths to be tested as well.
  • The upper and lower grips can be opened and closed either individually or together via remote control or PC.
  • For safety reasons, specimen tongs can be used to insert the specimen.
  • 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.
  • Time is saved due to quick and easy adaptation of small specimen grips and test fixtures to large specimen grips via the T-slotted system. Precise alignment ensures reliable test results.
  • 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.
  • Short specimens can also be gripped due to the special design of the specimen grip.
  • 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

It is not necessary to set the thickness. This is a big advantage, above all, for soft specimens or if specimen thickness changes.

Two horizontal T-slot pairs are found in the specimen grip. The larger slot is for insertion of the T-slotted system to accommodate smaller load cells and specimen grips. The smaller slot is for inserting/guiding additional accessories.

You can insert the specimen vertically and in the center using the specimen gripper. The slot of the specimen grips is used as a guide. Using a specimen gripper helps minimize the risk of injury when inserting and removing specimens from the specimen grips. Such risks are the pinching of body parts between the jaws or the burning of body parts on hot specimens.

Technical data, Fmax 50 kN

Item No.

313646[1]

Type

8494

Test load Fmax

50

kN

Operating principle/identification

Double-sided closing

Gripping force, max. at 300 bar

100

kN

Operating pressure

12 ... 300

bar

Dimensions

Height

205

mm

Width

386

mm

Depth

132

mm

Gripping travel

35

mm

Opening width, max. with jaws

See table of jaws (specimen thickness)

Gripping of the specimen

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

Weight per specimen grip, approx.

37

kg

Connection

Ø 36/60[2]

mm

Ambient temperature

+10 ... +35

°C

Scope of delivery

2

pieces

  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09
  1. These specimen grips can be offered with a 36 mm or 60 mm connection (selection made using parts list alternatives).

Technical data, Fmax 100 kN

Item No.

313760[1]

Type

8592

Operating principle/identification

Double-actuator

Test load Fmax

100

kN

Gripping force, max. at 300 bar

250

kN

Gripping force, max. at 480 bar

-

Dimensions

Height

303

mm

Width

479

mm

Depth

170

mm

Width with screw unit, open completely

461

mm

Gripping travel

70

mm

Gripping of the specimen

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

Weight per specimen grip, approx.

70

kg

Connection

Ø 60

mm

Ambient temperature

+10 ... +35

°C

Scope of delivery

2

pieces

  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09

Technical data, Fmax 250 kN

Item No.

313782[1]

Type

8594

Operating principle/identification

Double actuator

Test load Fmax

250

kN

Gripping force, max. at 480 bar

410

kN

Gripping force, max. at 300 bar

-

Opening width, max. with jaws

59

mm

Dimensions

Height

303

mm

Width

479

mm

Depth

170

mm

Width with screw unit, open completely

-

mm

Gripping travel

35

mm

Gripping of the specimen

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

Connection

Ø 60

mm

Ambient temperature

+10 ... +35

°C

Weight per specimen grip, approx.

70

kg

Scope of delivery

2

pieces

  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09

Technical data, Fmax 330 kN

Type

330

kN

Item No.

1014893

Maximum tensile force (Fmax)

330

kN

Maximum gripping force

588

kN

Flat specimens

Clamping range

0 to 80

mm

Max. thickness

80

mm

Max. width

95

mm

Round specimens

Clamping range

5.5 to 80

mm

Max. system pressure

480

bar

Dimensions

Height (H)

280

mm

Width (W)

550

mm

Depth (D)

220

mm

Weight (each)

205

kg

Technical data, Fmax 400 kN

Type

400

kN

Item No.

1014894

Maximum tensile force (Fmax)

400

kN

Maximum gripping force

588

kN

Flat specimens

Clamping range

0 to 80

mm

Max. thickness

80

mm

Max. width

95

mm

Round specimens

Clamping range

5.5 to 80

mm

Max. system pressure

480

bar

Dimensions

Height (H)

280

mm

Width (W)

550

mm

Depth (D)

220

mm

Weight (each)

205

kg

Technical data, Fmax 600 kN

Type

600

kN

Item No.

084473

Maximum tensile force (Fmax)

600

kN

Maximum gripping force

965

kN

Flat specimens

Clamping range

0 to 100

mm

Max. thickness

100

mm

Max. width

128

mm

Round specimens

Clamping range

5.5 to 100

mm

Max. system pressure

480

bar

Dimensions

Height (H)

350

mm

Width (W)

630

mm

Depth (D)

250

mm

Weight (each)

320

kg

Technical data, Fmax 1200 kN

Type

1200

kN

Item No.

1015113

Maximum tensile force (Fmax)

1200

kN

Maximum gripping force

1600

kN

Flat specimens

Clamping range

0 to 100

mm

Max. thickness

100

mm

Max. width

162

mm

Round specimens

Clamping range

5.5 to 100

mm

Max. system pressure

480

bar

Dimensions

Height (H)

459

mm

Width (W)

790

mm

Depth (D)

320

mm

Weight (each)

700

kg

Technical data, Fmax 1600 kN

Type

1600

kN

Item No.

628448

Maximum tensile force (Fmax)

1600

kN

Maximum gripping force

2750

kN

Flat specimens

Clamping range

0 to 80

mm

Max. thickness

80

mm

Max. width

210

mm

Round specimens

Clamping range

5.5 to 80

mm

Max. system pressure

480

bar

Dimensions

Height (H)

603

mm

Width (W)

940

mm

Depth (D)

390

mm

Weight (each)

1305

kg

Technical data, Fmax 2000 kN

Type

2000

kN

Item No.

084466

Maximum tensile force (Fmax)

2000

kN

Maximum gripping force

2750

kN

Flat specimens

Clamping range

0 ... 100

mm

Max. thickness

100

mm

Max. width

205

mm

Round specimens

Clamping range

5.5 ... 100

mm

Max. system pressure

480

bar

Dimensions

Height (H)

603

mm

Width (W)

940

mm

Depth (D)

390

mm

Weight (each)

1325

kg

Technical data, Fmax 2500 kN

Type

2500

kN

Item No.

611432

Maximum tensile force (Fmax)

2500

kN

Maximum gripping force

3850

kN

Flat specimens

Clamping range

0 ... 100

mm

Max. thickness

100

mm

Max. width

210

mm

Round specimens

Clamping range

5.5 ... 100

mm

Max. system pressure

480

bar

Dimensions

Height (H)

650

mm

Width (W)

1090

mm

Depth (D)

430

mm

Weight (each)

1765

kg

Applications

  • Specimen material:
    Metals (also sintered metals, metal composites)
  • Specimen shape:
    Round and flat specimens (short clamping length)
  • 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.
  • Time is saved due to quick and easy adaptation of small specimen grips and test fixtures to large specimen grips via the T-slotted system. Precise alignment ensures reliable test results.
  • 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.
  • The patented clamping principle is also suitable for short clamping lengths.
  • Due to the vertically braced arrangement, the specimen grips are ideally suited for tests with alternating loads and strain rate control.
  • Optical and mechanical extensometers can be used even for extremely short clamping lengths.
  • Excellent reproducible grip position and specimen alignment to the test axis Ideal for tests on specimens which are sensitive to transverse forces (repeat accuracy of grip position of ±0.01 mm is possible)
  • 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

It is not necessary to set the thickness. This is a big advantage, above all, for soft specimens or if specimen thickness changes.

The jaws are supported and held parallel via a third actuator. This patented process ensures that even specimens with short clamping lengths can be held securely.

  • Two different centering stops for aligning flat specimens to the tensile axis are included in the scope of delivery:
  • Stop tup between the jaws for short clamping lengths
  • Wide centering stop above the jaws

Technical overview of hydraulic grips for short clamping-lengths

Technical data, Fmax 50 kN and 70 kN

Item No.

032562[1]

032563[1]

Type

8495

8495

Operating principle/identification

Double-sided closing

Double-sided closing

Test load Fmax

50

70

kN

Gripping force, max. at 300 bar

110

110

kN

Dimensions

Height

327

359

mm

Width

413

413

mm

Depth

258

258

mm

Opening width, max. with jaws

34

34

mm

Permissible surface pressure on jaw, max.

1000

1000

N/mm2

Grip-to-grip separation, approx.

6

6

mm

Weight per specimen grip, approx.

69

69

kg

Connection, stud

Ø 36

Ø 60

mm

Ambient temperature

+10 ... +35

+10 ... +35

°C

Scope of delivery

2

2

pieces

  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09

Technical data, Fmax 150 kN and 250 kN

Item No.

046496[1] [2]

046873[1] [2]

Type

8589

8589

Operating principle/identification

Short clamping

Short clamping

Test load Fmax

150

250

kN

Operating principle

Two-sided closing

Two-sided closing

Gripping force, max.

275

420

kN

Operating pressure, max.

300

400

bar

Grip-to-grip separation, min.

15

15

mm

Dimensions

Height

490

490

mm

Width

570

570

mm

Depth

445

445

mm

Opening width, max. with jaws

59

59

mm

Weight per specimen grip, approx.

215

215

kg

Connection

Ø 60

Ø 60

mm

Ambient temperature

+10 ... +35

+10 ... +35

°C

Scope of delivery

2

2

pieces

  1. Not possible in connection with Z100 THW, Z150 TL and Z250 RED
  1. Recommended and approved for strain rate control to the standards DIN EN ISO 6892-1:2009 and ASTM E8-09
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