Creep Testing Machine

Its main part is a simple lever (load beam) with a mechanical advantage of 8:1. The load beam gives a steady and uniform tensile load. A digital indicator measures the extension (creep) of the specimen under load. To ensure correct loading of the specimen, the load beam has a ball-bearing pivot.

To apply a load, students add weights to a weight hanger and measure time and the creep. For effect-of-temperature tests, the student freezes or heats a cool-pack and places it next to the specimen. They then fit the transparent enclosure to preserve the temperature around the specimen during the test.

Students may record and plot results by hand, using a timer (not supplied) and the readings from the digital indicator and thermometer. Alternatively, the student can use TecQuipment’s optional Versatile Data Acquisition System to capture the data, plot charts and export data.

A user guide is supplied with the Creep Machine. The guide includes full details of the equipment, detailed experiment procedures, theory and results.

Technical parameters:

Technical Specifications

Loading arm: 4:1 loading ratio

Polypropylene specimens (10 each)

Specimen: 22mm gauge length, 4.8(W) x 1.6(t) mm nominal

Load hanger: 1N

Dial gauge, 0.01mm resolution, 25mm travel

Thermometer

Transparent specimen cover

Hot and cold packs

Key Features：

Ideal for student use and classroom demonstrations

Demonstrates the three phases of creep

Demonstrates effect of temperature on creep

Compact and easily stored

Supplied with weights and test specimens

Inexpensive specimens readily available in lead and plastics

Completely self-contained, needs no other parts

Essential Services

None needed for ambient temperature tests. For ‘effect of temperature tests’, the cool pack must to be frozen in the ice making compartment of a refrigerator and heated in a pan of hot water.

Test methods：

The creep apparatus employs lever action to apply a dead-weight load to a specimen. The lever beam is notched to receive the knife-edge of the fulcrum. The fulcrum is at the top of a column rigidly attached to the base. The specimen is pinned to two "grips" for self-alignment. The lower grip is attached to the base with a screw stud to allow height adjustment during set up. The upper grip pivots on the lever. The distance between the pivot point and the upper grip attachment point is 25.4mm.

Weights are placed on a weight tray suspended from a pin at the opposite end of the lever. The distance from the pivot point to the tray pin is 254mm, thus there is a multiplier of 10 for the load applied to the specimen. A counter weight at the specimen end of the beam is moved to balance the lever system.

A linear variable displacement transformer (LVDT) is located 127mm from the pivot point. The extension of the specimen is one-fifth of the indicated LVDT displacement. The tip of the LVDT core extension rides on the upper surface of the beam. The LVDT is suspended from a rod attached to the base. A signal conditioning unit is connected to the LVDT by a cable. The displacement data from the LVDT are recorded by data acquisition software.

To set up and start a test, the weight tray is removed with the pin remaining in the beam. The specimen is attached to each grip by a pin. The nut on the lower grip is adjusted to make the beam level. The tip of the LVDT probe is aligned on a line marked 127mm from the pivot point. The counter weight is adjusted to balance the beam, then locked by a setscrew. The lower grip nut is adjusted to move the specimen upward until the LVDT display indicates approximately -12V.

The weight tray and first mass are placed on a scale to determine the mass. The tray and mass are attached to the beam and supported so that the specimen is not loaded. The data acquisition system is started and the tray is slowly lowered to apply the load. Subsequent masses are determined and added at periodic intervals. Data are plotted and recorded as displacement vs. time.