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Wedge Grips

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Material
  • Metals
  • Plastics
  • Wood
Test load
  • 2.5 kN - 250 kN
Specimen shape
  • Round specimens
  • Flat specimens
Type of test
  • Tensile

Ideal for quality assurance

The wedge grip is a symmetrically closing specimen grip. A lever is used to open and close the grips, as well as apply gripping force before the test.

A distinction is made between two operating principles:

  • Body over wedge (also BoW)
  • Lever

Advantages & features

Advantages & features

Body over wedge operating principle
Advantages of body over wedge principle
Lever operating principle
Advantages of lever principle

Body over wedge operating principle

Wedge grips operating on this principle apply a greater preloading force when the specimen is inserted. The preload applied to the specimen is transmitted to the jaws via the body of the grips using a lead screw. In this case also the main gripping force is not attained until during tensile loading (via the wedge effect). Grips of this type have two additional advantages: Specimens inclined to slippage are gripped more firmly right from the beginning and the gripping length remains constant, even if thickness varies from specimen to specimen. In addition, strain-rate control to ISO 6892-1 (2009) Method A (closed loop) and ASTM E 8 (2009) Method B can be applied with greater precision.

Advantages of body over wedge principle

  • The modular design of the grips allows them to be configured for manual or pneumatic actuation according to requirements.
  • With specimen grips from the body over wedge portfolio, the position of the jaws remains constant in the test direction as the specimen is gripped. This means that the grip-to-grip separation does not depend on the specimen thickness.
  • The manual version offers a cost-efficient, simple, and robust solution. Actuation via the radially mounted lever enables high preload forces.
  • With the pneumatic version the emphasis is on fast, reproducible and, most importantly, parallel gripping. Full gripping force is available right from the start, so that the static jaws transfer the test speed directly to the specimen. When working with a temperature chamber, simple extensions are used. The pneumatic actuator is positioned outside the chamber.

Lever operating principle

Wedge grips operating on this principle are self gripping. During insertion a preload is applied to the specimen via operation of the lever and a spring. However, it is only during tensile loading that the main gripping force is attained via the wedge effect. The gripping pressure maintains a constant relationship to the tensile force through displacement of the wedges. The advantage of grips of this type is that the test can be performed very quickly and does not require the operator to exert too much force.

Advantages of lever principle

  • The closing force is proportional to the tensile force (self-gripping).
  • Wedge grips always close symmetrically with respect to the tensile axis.
  • Long clamping length and good jaw guiding properties allow contact pressure on the specimen to be kept to a minimum.
  • High temperature resistance and low overall height makes specimen grips ideal for use in temperature chambers.
  • The wedge grip design ensures fast and energy-saving operation using a lever.
  • The lever can be locked when the wedge grips are open.

Technical overview

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Related products and accessories

Downloads

Name Type Size Download
  • Product brochure: Specimen Grips and Test Tools PDF 4 MB
  • Product information: Wedge grips, Fmax 2,5 kN / 5 kN PDF 161 KB
  • Product information: Wedge grips, Fmax 10 kN / 20 kN PDF 713 KB
  • Product information: Wedge grips, Fmax 10 kN / 50 kN PDF 230 KB
  • Product information: Wedge grips body over wedge, Fmax 10 kN PDF 690 KB
  • Product information: Wedge grips, Fmax 30 kN / 50 kN PDF 295 KB
  • Product information: Wedge grips body over wedge, Fmax 50 kN PDF 427 KB
  • Product information: Wedge grips, Fmax 100 kN PDF 349 KB
  • Product information: Wedge grips body over wedge, Fmax 100 kN PDF 451 KB
  • Product information: Wedge grips, Fmax 150 kN PDF 259 KB
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