Grips and Fixtures for Hydraulic Universal Testing Machines

The nine fixtures test fasteners, steel welding mesh, rock, concrete beams and bending specimens of metal, ceramic and composite, at ratings from 600 kN up to 2000 kN (449,618 lbf). We supply all nine for hydraulic frames.

Four of them test fasteners: a nut proof load fixture and a bolt and nut tensile grip at both 600 kN and 2000 kN. A tensile shear fixture rated to 1000 kN tests steel welding mesh, and a 2000 kN rock shear fixture takes cylindrical and cubic rock specimens.

Three more work at 2000 kN: a bending fixture with interchangeable mandrels, a flexure fixture on roller supports for three- or four-point tests, and a four-point flexure fixture for concrete beams.

The fastener and mesh fixtures hang in the machine's hydraulic grips, while the others mount on a flange or fixing block above and a positioning pin below. All nine work at ambient temperature.

Both run the same proof load test on nuts up to property class 10, to GB/T 3098.2-2010 and ISO 898-2, and they differ in capacity and thread range.

In the test the nut is loaded on a hardened mandrel to the proof load its property class specifies, and it passes if it carries that load without stripping or breaking.

The NGA605A is rated to 600 kN and comes with M6, M12, M16 and M20 accessories, with M5 to M27 offered as options, fine pitch threads included. The 2000 kN fixture comes with M16, M20, M27 and M36 and takes options from M5 to M39, fine pitch included.

The larger fixture is heavier and taller, at 24 kg (53 lbs) per upper or lower grip and 375 mm high, against 12 kg (26 lbs) and 290 mm for the 600 kN version.

Both grips support three loading arrangements: bolt tension, stud tension and wedge load. The NGB605A is rated to 600 kN and its larger counterpart to 2000 kN.

Bolt tension pulls the bolt straight along its axis. Stud tension does the same on a headless threaded stud, held in threaded support blocks at both ends.

Wedge load puts an angled wedge under the bolt head, which adds bending at the junction of head and shank, so the test shows whether the head stays sound under full tensile load. The grips also run proof load tests on bolts and nuts.

The 600 kN grip comes with M6, M12, M16 and M20 accessories and takes M4 to M27 as options, fine pitch included. The 2000 kN grip takes optional accessories from M5 to M39 for larger fasteners.

The minimum length depends on the thread size and the grip, from 9 mm for an M4 bolt up to 139 mm for M39 on the 2000 kN grip. A bolt that is too short cannot be held and loaded at the same time, and the same minimums apply to wedge load, bolt tension and stud tension.

Up to M10 the two grips ask for the same lengths, and an M10 bolt needs 22 mm on either. From M12 upward the 2000 kN grip needs 10 mm more: 42 mm against 32 mm for M12, 110 mm against 100 mm for M20 and 117 mm against 107 mm for M27.

Only the 2000 kN grip takes threads beyond M27, and an M30 bolt needs at least 130 mm on it.

Our engineers will check your thread sizes and bolt lengths against both grips when you send them with a request for quotation.

The NGA106A shears the welded joints of steel welding mesh at up to 1000 kN (224,809 lbf), and a separate fixture shears rock specimens at up to 2000 kN.

The mesh fixture works to GB/T 1499.3. Pulling one bar of the mesh against the other shears the weld between them, and the force this takes shows how well the weld holds. It takes specimen diameters of Ø6, Ø8, Ø10, Ø12 and Ø16 mm, hangs from the upper hydraulic grip on a Ø32 mm connecting rod and needs at least 425 mm of test space.

The rock shear fixture works to GB/T 23561.11 on cylinders of Ø50 × 50 mm or cubes of 50 × 50 × 50 mm. It mounts on a flange above and a positioning pin below and needs at least 450 mm of test space. The same fixture is described with our splitting fixtures for rock and concrete.

The bending fixture bends metal, ceramic and composite specimens around a mandrel, and the flexure fixture tests the same materials on roller supports in three- or four-point bending, both at up to 2000 kN.

The bending fixture works to GB/T 232 and to the reinforcing bar standards GB 1499.1 and GB 1499.2, and comes with Ø32, Ø60, Ø88 and Ø160 mm mandrels. More than eighty optional mandrels run from Ø1 to Ø280 mm, because the bar standards set the mandrel diameter from the bar diameter and grade. Its lower grip weighs 86 kg (190 lbs), and the fixture needs 480 mm of test space. The full mandrel list is on our heavy-duty bending fixtures page.

The flexure fixture works to GB/T 2542, GB/T 4111 and JC/T 239, with rollers of Ø35 × 210 mm and Ø30 × 160 mm. Its lower grip is lighter at 23 kg (51 lbs), and the fixture needs only 280 mm of test space.

Two loading points put a constant bending moment on the whole section between them, so the beam fails at its weakest point in that zone. That is how the fixture measures the flexural strength of concrete beams to GB/T 50081 at up to 2000 kN, and it also takes composite and construction materials.

Both spans adjust, 60 to 480 mm below and 60 to 180 mm above, which suits the listed concrete beams: 150 × 150 × 600 mm, 150 × 150 × 550 mm and 100 × 100 × 400 mm.

A digital indicator and an elasticity modulus measurement device are offered as options, so the modulus of elasticity can be measured on the same setup as strength.

The upper grip weighs 12 kg (26 lbs), the lower 20 kg (44 lbs), and the fixture needs at least 450 mm of test space. It is shown alongside the roller flexure fixture on our flexure fixtures for large and brittle specimens page.