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Workshop practise of estimating bolt preload by torque measurement has long been known to be of limited validity. Many system variables such as surface roughness, lubrication, variability in bulk materials properties, and rate of torque application contribute to the difficulty.
The DN 66 Screw Tension/Friction Test Machine can be used as both a research tool and a quality assurance tool to achieve a better understanding of the behaviour of the fastener system. With the DN 66/2 Three Component Tension and Torque Sensor Head measurements of the total torque input and the thread friction torque are gathered simultaneously. From these measurements the under-head friction torque can be calculated, and a full torque versus angle signature analysis made.
The control unit includes an interface card and Windows based control and data acquisition software. Routine tests can be automated and a full angle signature analysis of the fastener system behaviour can be made from recorded data.
The DN 66 Screw Tension/Friction Test Machine consists of a DN 66 Base Unit and at least one tension or torque/tension sensor head. A drive motor with speed encoder and gearbox are mounted on a rigid platform on a floor standing frame. An angle encoder is fitted to the gearbox output shaft.
A support block, with linear adjustment to accommodate differing lengths of fastener, holds either a tension or torque/tension sensor head. Two designs of sensor head are available. These are the DN 66/1 Two Component Tension Sensor Head, which measures total input torque and tension in the fastener; and the DN 66/2 Three Component Tension and Torque Sensor Head, measuring total input torque, thread friction torque and tension in the fastener. Each is available in capacities to cover threads in the range M4 to M30. Heads are interchangeable. For measurement of the extension of the test bolt, the DN 66/3 Displacement Measurement Sensor is available as an optional item of equipment.
For each fastener size, a set of fixtures is used to mount the test specimen in the sensor head. Specimen fixtures can be supplied with the system for bolt sizes from M4 to M30, or drawings supplied for local manufacture.
The DN 66 Screw Tension/Friction Test Machine has a COMPEND 2000 based sequence control and data acquisition system and is supplied complete with an IPC 610 industrial PC system complete with all hardware and software installed and tested. The software employs Windows features for easy user access to all machine and test set-up parameters. On-screen help is provided.
Data may be stored to hard disc and the software includes an auto-scaling trend display for real time monitoring of test progress.
Tests are defined by a sequence of steps. Set points may be adjusted by step change, ramp or conditional upon test conditions. The test sequence is followed automatically unless interrupted by the operator or an alarm. Set points may also be adjusted manually during the operation of the test sequence.
| Torque Range: | 800 Nm |
| Tension Range: | 320 kN |
| Bolt Length: | 20 to 230 mm |
| Repeatability : | 0.5 % |
| Speed Range: | 0 to 20 rpm infinitely variable |
| Motor: | 4.6 kW brushless dc motor |
| Displacement Measurement: | |
| Type: | LVDT |
| Range: | 1.5 mm |
| Resolution: | 2 µm |
| Electricity: | 3 phase 5.0 kW |
| DN 66 | Screw Tension/Friction Test Machine |
| DN 66/1 | Two Component Tension Sensor Head |
| DN 66/2 | Three Component Tension and Torque Sensor Head |
| DN 66/3 | Displacement Measurement Sensor |
Copyright © 2002 Plint Tribology Ltd.