Laser extensometer

A drift compensated and intensity averaged extensometer for measuring the diameter or other properties of a substantially cylindrical sample based upon the shadow of the sample is described. A beam of laser light is shaped to provide a beam with a uniform intensity along an axis normal to the sample. After passing the sample, the portion of the beam not striking said sample is divided by a beam splitter into a reference signal and a measurement signal. Both of these beams are then chopped by a light chopper to fall upon two photodiode detectors. The resulting ac currents are rectified and then divided into one another, with the final output being proportional to the size of the sample shadow

Conductive elastomeric extensometer

Bridge circuit, in which conductive elastomeric material is the variable leg, precisely measures surface area changes in the human body. Circuits are used singularly, or in quantity by adding elements and amplifier circuits. Elastomeric strips can be located in a form-fitting garment

Tensile testing apparatus

An improved mechanical extensometer is described for use with a constant load creep test machine. The dead weight of the extensometer is counterbalanced by two pairs of weights connected through a pulley system and to rod extension and leading into the furnace where the test sample is undergoing elevated temperature (above 500 F.) tensile testing. Novel gripper surfaces, conical tip and flat surface are provided in each sampling engaging platens to reduce the grip pressure normally required for attachment of the extensometer to the specimen and reduce initial specimen bending normally associated with foil-gage metal testing

Amplifying ribbon extensometer

Device provides accurate measurement of strain on flexible membranes and fabrics. It is compact and lightweight, has strain-amplification capability up to five, and has an accuracy better than one percent

Amplifying ribbon extensometer

A self-contained, nonelectrical strain gage capable of amplifying strain inputs and preserving the maximum strain measurement for later observance is presented

Experimental determination of transient strain in a thermally-cycled simulated turbine blade utilizing a non-contact technique

A type of noncontacting electro-optical extensometer was used to measure the displacement between parallel targets mounted on the leading edge of a simulated turbine blade throughout a complete heating and cooling cycle. The blade was cyclically heated and cooled by moving it into and out of a Mach 1 hot gas stream. The principle of operation and measurement procedure of the electro-optics extensometer are described

Development and use of an extensometer for determining the mechanical compliance of crack toughness test specimens

Extensometer for determining mechanical compliance of crack toughness test specimen

Extensometer automatically measures elongation in elastomers

Extensometer, with a calibrated shaft, measures the elongation of elastomers and automatically records this distance on a chart. It is adaptable to almost any tensile testing machine and is fabricated at a relatively low cost

The mechanical properties of anisotropic polymers: Progress report no. 6

Part 1 General Developments The basic development work on the tensile creep apparatus was completed by March, 1968. A description of the latest 'heavy-duty' creep rig and two types of contraction extensometer, together with the relevant creep trials, was given in Progress Report No. 5. Since then two further 'heavy-duty' creep rigs have been assembled and tested and are now ready for use with rigid plastics. In addition, further trials of the double transducer contraction extensometer described in Report No. 5 have been carried out. These trials are described in part 2 of this report The trials were considered reasonably satisfactory and each of the three heavy-duty creep rigs has now been fitted with a device of this type in addition to the normal tensile extensometer. The polythene creep rig described in Progress Report No. 3 has been working satisfactorily for over a year and no further modifications have been made in the period under review. At the conclusion of the above-mentioned trials it was considered that the creep apparatus was unlikely to require any further major changes. A detailed report of all the apparatus has therefore been prepared with the intention of submitting it for publication to the Journal of Scientific Instruments. It is at present being examined at the Ministry of Technology. (CoA Memo. No. 158)