Thermographic Temperature Measurement Research Articles

An algorithm study on the identification of a pipeline's irregular inner boundary based on thermographic temperature measurement

A transient two-dimensional heat transfer model is built and solved using the finite element method for the study of the temperature distribution rules of a pipeline with an irregular inner boundary when heated by the hot circulating fluid, and, at the same time, based on a conjugate gradient method, an algorithm is presented for the identification of the irregular inner boundary by thermographic temperature measurements of the outer pipeline surface. Numerical experiments are conducted in order to verify the effectiveness of the algorithm and also to investigate the influence of the test piece property, temperature measurement error, etc on the identification results. It is concluded that the algorithm can efficiently solve this boundary identification problem, the effect of the initial boundary guess is negligible, and the algorithm based on curves of the maximum temperature difference (MTD) can significantly reduce the effect of the measurement error.

Thermographic Temperature Measurement Compared with Pinprick and Cold Sensation in Predicting the Effectiveness of Regional Blocks

We designed this study to evaluate the usefulness of thermographic temperature measurement with an infrared camera, compared with patient response to cold and pinprick, as a means of assessing the success or failure of axillary blockades. Axillary blocks were performed on 25 patients undergoing surgery on the hand or forearm using a nerve stimulator technique with mepivacaine 1.5%. Pinprick and cold sensation were assessed on the operative site at 5-min intervals for 30 min. A thermographic image of the operative limb was recorded at similar time intervals. Thermographic images of the unblocked limb were taken before block placement and at 30 min. Temperature values at the operative site and unblocked limb were calculated from the thermographic images. Results revealed that thermography had higher combined values for sensitivity, specificity, and positive and negative predictive values than both cold and pinprick at all time intervals, with statistically significant differences at 15 min (thermography versus cold, P = 0.006; thermography versus pinprick, P = 0.026) and 30 min (thermography versus cold, P = 0.038; thermography versus pinprick, P = 0.040). For thermography as a method of block assessment, an optimal time of 15 min after mepivacaine local anesthetic injection gives the highest combined values for predicting a successful block (P = 0.004). We conclude that thermography provides an early and objective assessment of the success and failure of axillary regional blockades.

Development of a New Crack Identification Technique Based on Near-Tip Singular Electrothermal Field Measured by Lock-in Infrared Thermography.

A new thermographic NDT technique was proposed, in which singular electrothermal field near crack tips under the application of periodically modulated electric current was measured using an infrared thermography combined with lock-in data processing technique. Experimental investigations were made on the resolution and the applicability in the identification of through-thickness artificial cracks and fatigue cracks embedded in steel and aluminum alloy plate samples. Modulated electric current was applied to the cracked sample by an induction coli. Lock-in thermal images synchronized to the reference current modulation signal were taken by the lock-in thermography. Significant singular electrothermal field was observed at the crack tip in the lock-in thermal image. The fatigue cracks as well as artificial cracks were found to be sensitively identified by the proposed technique in good resolution compared with the singular method using a conventional thermographic temperature measurement.

Infrared thermographic temperature measurement during laser heat treatment

A commercial infrared thermography system has been used to monitor workpiece surface temperatures during laser heat treatment. A simple optical filtering technique was used to increase the upper temperature limit of the thermography system. Experimental results are presented which demonstrate an accuracy of ±10%. The filtering technique is applicable to most commercial infrared thermographic systems.