Suresh Periyannan

Simultaneous moduli measurement of elastic materials at elevated temperatures using an ultrasonic waveguide method

A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here. This technique can be used for simultaneously measuring Youngs modulus (E) and shear modulus (G) of different materials over a wide range of temperatures (35u2009°C-1200u2009°C). The specimens used in the experiments have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator/detector (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The orientation of the transducer can be used for simultaneously generating/receiving the L(0,1) and/or T(0,1) using a single transducer in a waveguide on one end. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference, as a function of uniform temperature distribution region (horizontal portion) of bend waveguides was measured and used to determine the material properties. Several materials were tested and the comparison between values reported in the literature and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time and effort over conventional means of measurement of temperature dependence of elastic moduli.

Temperature dependent E and G measurement of materials using ultrasonic guided waves

A novel technique for measuring the moduli of elastic isotropic material as a function of temperature, using ultrasonic guided wave modes is presented here. These techniques can be used for measure the Youngs modulus (E) and Shear Modulus (G) of material. Here, the L (0, 1) wave mode is used for measuring E and T(0,1) mode for G. The scope of measurement is made from room temperature to maximum utility temperature of material. In this work, the material is required in the form of a waveguide with an ultrasonic guided wave generator at one end and an embodiment (such as a notch or a bend) at the other end for obtaining reflected signals. The transducer is kept at room temperature while the end (along with the embodiment) is kept inside a heating device such as a temperature controlled furnace. The time of flight difference (δTOF), as a function of temperature, between the guided wave reflections from the embodiment and the end of the waveguide, is used to measure the material properties. The technique is ...

Re-configurable multi-level temperature sensing by ultrasonic “spring-like” helical waveguide

This paper introduces a novel technique for multi-level temperature measurement using a single reconfigurable ultrasonic wire waveguide that is configured in the form of a helical spring. In this embodiment, the multiple sensing levels located along the length of the helical waveguide wire can be repositioned by stretching or collapsing the spring to provide measurements at different desired spacing in a given area/volume. This method can measure over a wide range of temperatures. The transduction is performed using Piezo-electric crystals that are attached to one end of the waveguide which act as transmitter as well as receiver. The wire will have multiple reflector embodiments (notches was used here) that allow reflections of input L(0,1) mode guided ultrasonic wave, in pulse echo mode, back to the crystal. Using the time of fight measurement at multiple predefined reflector locations, the local average temperatures are measured and compared with co-located thermocouples. The finite element modeling sim...

Torsional mode ultrasonic helical waveguide sensor for re-configurable temperature measurement

This paper introduces an ultrasonic torsional mode based technique, configured in the form of a helical “spring-like” waveguide, for multi-level temperature measurement. The multiple sensing levels can be repositioned by stretching or collapsing the spring to provide simultaneous measurements at different desired spacing in a given area/volume. The transduction is performed using piezo-electric crystals that generate and receive T(0,1) mode in a pulse echo mode. The gage lengths and positions of measurements are based on machining multiple reflector notches in the waveguide at required positions. The time of fight (TOF) measurements between the reflected signals from the notches provide local temperatures that compare well with co-located thermocouples.

Ultrasonic bent waveguides approach for distributed temperature measurement.

HighlightsNovel multiple bent waveguide method proposed to measure temperature in a chamber.Multiple configurations of bent wires are used with single transducer and electronics.Multiple bent wire waveguide system is calibrated at uniform temperature region.System is validated against thermocouple readings at multiple levels inside the furnace.3D FEM simulation is used to determine the effect of bend radiuses in this method. &NA; This paper describes novel techniques for simultaneous measurement of temperatures at multiple locations using two configurations (a) a single transducer attached to multiple waveguides of different lengths (each with a single bend) and (b) single waveguide with multiple bends connected to single transducer. These techniques improve upon the earlier reported studies using straight waveguides, where the non‐consideration of the effect of temperature gradients was found to be a major limitation. The range of temperature measurement is from room temperature to maximum utility temperature of the waveguide material. The time of flight difference of reflected ultrasonic longitudinal guided wave modes (L(0, 1)) from the bend, which is the reference signal, and another signal from the end of the waveguide, is utilized to measure the local temperature of the surrounding media. Finite element simulations were employed to obtain the appropriate dimensions and other design features of the multiple bent waveguide. This work is of interest to several industrial applications involving melters and furnaces.

Multiple temperature sensors embedded in an ultrasonic “spiral-like” waveguide

This paper studies the propagation of ultrasound in spiral waveguides, towards distributed temperature measurements on a plane. Finite Element (FE) approach was used for understanding the velocity behaviour and consequently designing the spiral waveguide. Temperature measurements were experimentally carried out on planar surface inside a hot chamber. Transduction was performed using a piezo-electric crystal that is attached to one end of the waveguide. Lower order axisymmetric guided ultrasonic modes L(0,1) and T(0,1) were employed. Notches were introduced along the waveguide to obtain ultrasonic wave reflections. Time of fight (TOF) differences between the pre-defined reflectors (notches) located on the waveguides were used to infer local temperatures. The ultrasonic temperature measurements were compared with commercially available thermocouples.

Distributed temperature sensing using a SPIRAL configuration ultrasonic waveguide

Distributed temperature sensing has important applications in the long term monitoring of critical enclosures such as containment vessels, flue gas stacks, furnaces, underground storage tanks and buildings for fire risk. This paper presents novel techniques for such measurements, using wire in a spiral configuration and having special embodiments such a notch for obtaining wave reflections from desired locations. Transduction is performed using commercially available Piezo-electric crystal that is bonded to one end of the waveguide. Lower order axisymmetric guided ultrasonic modes were employed. Time of fight (TOF) differences between predefined reflectors located on the waveguides are used to infer temperature profile in a chamber with different temperatures. The L(0,1) wave mode (pulse echo approach) was generated/received in a spiral waveguide at different temperatures for this work. The ultrasonic measurements were compared with commercially available thermocouples.