Non-invasive temperature measurement and control techniques under thermomechanical fatigue loading

Jones, Jonathan; Brookes, S.; Whittaker, Mark; Lancaster, Robert

doi:10.1179/1743284714y.0000000654

Cited by 5 publications

(12 citation statements)

References 28 publications

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“…This behaviour was noted in previous work [11], the small mass of the thermocouples gives rise to rapid temperature changes. Thermocouples appear to absorb heat energy during heating stages of the cycle and shed heat during the cooling stage.…”

Section: Discussionmentioning

confidence: 67%

“…A conventional air spray gun was used to apply the paint to a thickness of approximately 20-25 µm [11,13]. The paint was then air dried and cured in a furnace at 300 • C for 1 h.…”

Section: Methodsmentioning

confidence: 99%

“…An example of complications residing from polished metallic surfaces is given in (Figure 5d), where a lack of adhesion between the TP and polished metallic surface results in spallation of the paint after thermal exposure. To avoid further spallation complications, prior to coating with TP, the specimen surfaces were lightly grit blasted with 120/220 grit to slightly roughen the surface so to improve the bond between the specimen and the TP as described in previous work [11,13,30]. A conventional air spray gun was used to apply the paint to a thickness of approximately 20-25 µm [11,13].…”

Section: Methodsmentioning

confidence: 99%

“…To overcome the established impact of spot welding on the specimen gauge section upon crack initiation [10], spot welding TCs on the specimen shoulder for dynamic high temperature control has been recommended [2,3]. However, despite these recommendations, the accuracy and practicality of such a technique under rapid dynamic thermal cycles is questionable, particularly in specimens with a long parallel gauge section, where large distances exist between the material under investigation and the TC location on the test piece shoulder [11].…”

Section: Introductionmentioning

confidence: 99%

“…In order to achieve desirable temperature ramp rates to simulate engine flight cycles which may exceed ±10 • C/sec, radiant lamp furnaces (RLF) or induction coil systems (ICS) are typically employed [11,12]. A variety of temperature control options now exist for these heating systems with the predominant control methods being spot welded TCs, pyrometers and most recently a technique using an infra-red camera known as thermography [11,13]. However, the use of pyrometers or thermography for dynamic temperature control is not yet recommended by the relevant standards involved with cyclic high-temperature testing such as TMF [2,3].…”

Section: Introductionmentioning

confidence: 99%

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Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Jones

2018

Applied Sciences

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This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for non-metallic materials. Isothermal and dynamic waveforms are employed over a 200-800 • C temperature range to pre-oxidised and coated specimens to assess the capability of the technique. This application shows thermography to be accurate to within ±2 • C of thermocouples, a standardised measurement technique. This work demonstrates the superior visibility of test temperatures previously unobtainable by conventional thermocouples or even more modern pyrometers that thermography can deliver. As a result, the speed and accuracy of thermal profiling, thermal gradient measurements and cold/hot spot identification using the technique has increased significantly to the point where temperature can now be controlled by averaging over a specified area. The increased visibility of specimen temperatures has revealed additional unknown effects such as thermocouple shadowing, preferential crack tip heating within an induction coil, and, fundamental response time of individual measurement techniques which are investigated further.

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Section: Discussionmentioning

confidence: 67%

“…A conventional air spray gun was used to apply the paint to a thickness of approximately 20-25 µm [11,13]. The paint was then air dried and cured in a furnace at 300 • C for 1 h.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Jones

2018

Applied Sciences

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Development of test facilities for thermo-mechanical fatigue testing

Palmer

Jones

Dyer

et al. 2019

International Journal of Fatigue

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A non-invasive experimental approach for surface temperature measurements on semi-crystalline thermoplastics

Boztepe

Gilblas

Almeida

et al. 2017

AIP Conference Proceedings

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Most of the thermoforming processes of thermoplastic polymers and their composites are performed adopting a combined heating and forming stages at which a precursor is heated prior to the forming. This step is done in order to improve formability by softening the thermoplastic polymer. Due to low thermal conductivity and semi-transparency of polymers, infrared (IR) heating is widely used for thermoforming of such materials. Predictive radiation heat transfer models for temperature distributions are therefore critical for optimizations of thermoforming process. One of the key challenges is to build a predictive model including the physical background of radiation heat transfer phenomenon in semi-crystalline thermoplastics as their microcrystalline structure introduces an optically heterogeneous medium. In addition, the accuracy of a predictive model is required to be validated experimentally where IR thermography is one of the suitable methods for such a validation as it provides a non-invasive, full-field surface temperature measurement. Although IR cameras provide a non-invasive measurement, a key issue for obtaining a reliable measurement depends on the optical characteristics of a heated material and the operating spectral band of IR camera. It is desired that the surface of a material to be measured has a spectral band where the material behaves opaque and an employed IR camera operates in the corresponding band. In this study, the optical characteristics of the PO-based polymer are discussed and, an experimental approach is proposed in order to measure the surface temperature of the PO-based polymer via IR thermography. The preliminary analyses showed that IR thermographic measurements may not be simply performed on PO-based polymers and require a correction method as their semi-transparent medium introduce a challenge to obtain reliable surface temperature measurements.

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Non-invasive temperature measurement and control techniques under thermomechanical fatigue loading

Cited by 5 publications

References 28 publications

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Development of test facilities for thermo-mechanical fatigue testing

A non-invasive experimental approach for surface temperature measurements on semi-crystalline thermoplastics

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