Precision Core Temperature Measurement of Metals Using an Ultrasonic Phase-Shift Method

Olaide F Olabode,Andrew P Longstaff,Naeem S Mian,Simon Fletcher

doi:10.3390/jmmp3030080

Olaide F Olabode, Andrew P Longstaff + Show 2 more

Open Access

https://doi.org/10.3390/jmmp3030080

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Abstract

Temperature measurement is one of the most important aspects of manufacturing. There have been many temperature measuring techniques applied for obtaining workpiece temperature in different types of manufacturing processes. The main limitations of conventional sensors have been the inability to indicate the core temperature of workpieces and the low accuracy that may result due to the harsh nature of some manufacturing environments. The speed of sound is dependent on the temperature of the material through which it passes. This relationship can be used to obtain the temperature of the material provided that the speed of sound can be reliably obtained. This paper investigates the feasibility of creating a cost-effective solution suitable for precision applications that require the ability to resolve a better than 0.5 °C change in temperature with ±1 °C accuracy. To achieve these, simulations were performed in MATLAB using the k-wave toolbox to determine the most effective method. Based upon the simulation results, experiments were conducted using ultrasonic phase-shift method on a steel sample (type EN24T). The results show that the method gives reliable and repeatable readings. Based on the results from this paper, the same setup will be used in future work in the machining environment to determine the effect of the harsh environment on the phase-shift ultrasonic thermometry, in order to create a novel technique for in-process temperature measurement in subtractive manufacturing processes.

Highlights

Dimensional accuracy and the surface integrity of manufactured products are key specifications that determine conformance to the design intent
This paper investigates the possibility of creating a novel system for the precision core temperature measurement of metals which can be adapted for use in different manufacturing processes
The results demonstrate that phase-shift ultrasonic thermometry can be used for core temperature measurement with a resolution of 0.1 ◦C

Summary

Introduction

Dimensional accuracy and the surface integrity of manufactured products are key specifications that determine conformance to the design intent. This paper investigates the possibility of creating a novel system for the precision core temperature measurement of metals which can be adapted for use in different manufacturing processes. The main difficulties reported concerning the use of this method are the parasitic electromotive force (EMF) from secondary joints, the necessity for the accurate calibration of the tool and workpiece as a thermocouple pair, the need to isolate the thermocouple from the environment and the lack of clarity on what the EMF represents [5,6] This method does not indicate the core temperature of the workpiece. The initial work consists of simulations in the k-Wave MATLAB toolbox—an open source toolbox for time domain acoustic and ultrasound simulations [17] This was used to study the two main ultrasonic thermometry methods—the ultrasonic pulse-echo and phase-shift methods. Based on the simulation results, ultrasonic phase-shift experiments were conducted in a metrology laboratory and the results of these experiments will serve as input to a future experiment which involves the use of the developed techniques in subtractive manufacturing processes

Materials and Methods

Conclusions