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Chapter 2 Design of Hot Rolling Wear Test Rig 60

2.5.5 Acoustic emission sensors

An acoustic emission (AE) sensor is mounted on the roller support frame to get the acoustic emission signal caused by the wear of the roller. Vaseline has not been used but can be applied between the sensitive tip of the sensor and the measurement surface, which guarantees better transfer of acoustic emission signal. T h e contact force is applied by a soft spring on the back of the sensor. T h e sensor should be located near the roller to measure the wear characteristics of the roller. But because of the high temperature of the roller, the sensor has to be located a little bit far from the roller.

T h e sensor is a high temperature sensor, which can operate up to 500°C.

2.6 Cooling design

High temperature is obtained on the top of the heating disk and the surface of the roller to simulate contact between the roller and hot steel product. S o m e insulating measures are taken to prevent heat in the heating zone from dissipating to the spindle and circumferential directions, as discussed in 2.2.4. But the temperature surrounding the roller support bearings, capacitance sensor and optoelectrical sensor for roller speed is still very high. High temperature will influence the working condition of bearings, the accuracy of sensors, and even d a m a g e the bearings and sensors.

Cooling is considered in structure design. To protect bearings, five dissipate flanges are designed at the front part of the roller support shaft, and the bearings are mounted

far from the roller, as s h o w n in Figure 2.8 and Figure 2.9. T h e probe of the

Chapter 2 Design of H o t Rolling W e a r Test Rig 61 capacitance sensor is extended to decrease the temperature of the original tip of the sensor. T h e optoelectrical sensor for roller rotary speed is mounted at the opposite end of the roller support shaft to prolong its life at lower temperatures.

Air forced cooling is also used to cool the bearings and sensors. There are five cooling nozzles to cool the bearings and sensors. Air cooling system block diagram is shown

on Figure 2.14.

Manifold Compressed

air supply

-rxh

Cutoff value

t <^*—c

I I

Pressure Moisture Flow

regulator eliminator regulator Plug

to bearing support block to dissipating flange of roller support shaft to protective pipe of capacitance sensor to opto—electrical sensor for roller speed

to roller support shaft

Pressure: 0 . 5 M P a - 1 M P a R o w rate: 2.2m 3/ h (36l/min)

Figure 2.14 Air cooling system block d i a g r a m

A compressed air nozzle blows the flanges of the roller support shaft in the opposite rotary direction. A small air nozzle blows the optoelectrical sensor for the roller speed

measurement to decrease the temperature.

The shaft of bearings is a hollow shaft. A s shown in Figure 2.8, compressed air can go through the hollow shaft from the end of the linking bolt, then blows out from 24 small cooling holes in the front end near the roller and front bearing. There are 16 holes in the axial direction in the support block of bearings. Compressed air goes into

Chapter 2 Design of H o t Rolling W e a r Test Rig 6 2 one hole from the rear of the block to the front of the block. Then through a circle slot,

it blows into another 15 holes at the rear of the block.

The original probe, guarded tip and newly designed tip of capacitance sensor are covered by a cooling pipe with a compressed air inlet on it. Compressed air blows from the top of the original tip to the end of the n e w tips, then to the side direction from an outlet to the flanges of the roller support shaft. Therefore, the cooling air affects less on the temperature of the roller, but decreases the temperature of flanges.

There are also 4 holes on the extension pipe of the sensor, and there is large space between the pipe and the extension rod, as s h o w n in Figure 2.13. Therefore, it will only transfer small quantity heat to the original probe.

The air pressure is 0.5 MPa-1 MPa and the maximum designed cooling air velocity is lOm/s. T h e diameter of nozzles is about 4 m m , so the total flow rate is 2.2 m3/hr.

Chapter 3

General Design of

Measurement and

Control System

Chapter 3 General Design of M e a s u r e m e n t and Control System 6 4

3.1 Measurement and control system based on computer

The application of the microcomputer allows evolution and development of the measurement and control system. Powerful software functions in this kind of system m a y include data acquisition, simulating instruction panel, instrumentation and device control, database management, and graphic display and output. This kind of

"intelligent" measurement and control system can offer increased reliability and flexibility, through non-end-loop monitoring, built-in diagnosis, regular internal calibration and prompting of inexperience of operators where necessary.

Researchers have shown that the design of the human-computer and machine-computer interfaces can m a k e a substantial difference in performance, accuracy, speed, learning time and user satisfaction for a computerised system. So, interface design plays an important role in the system. Actually, interface design is the main task for a measurement and control system based on a computer, because sensors, instruments and control devices are usually available directly from the manufacturers.

Interface design for machine measurement and control is a combined knowledge of mechanical engineering, microelectronics, computer engineering and electrical engineering.

For the design of an experimental system, a commercial computer system is usually adopted. Commercial computer, commercial data logging and control board and some accessory function boards, even commercial software platform are implemented. The development period is short and interface hardware work is relatively simple for this

Chapter 3 General Design of M e a s u r e m e n t and Control System 65