I. Ihara

Ultrasonic probes for high temperature immersion measurements

Ultrasonic probes for high temperature measurements in immersion are presented. These probes consist of piezoelectric transducers and buffer rods, and may be operated in the pulse echo mode. The probes can operate to temperatures as high as 215 °C without requiring a cooling system. For imaging purposes, one end of the clad buffer rod is machined into a semi-spherical concave shape, of which the purpose is to focus the ultrasound. The operating frequency is between 5 and 9 MHz. Ultrasonic images, produced using a mechanical raster scan with the probes fully immersed in silicone oil at elevated temperatures, are presented. The importance of the signal-to-noise ratio in the pulse-echo measurement is discussed.

Clad polymer buffer rods for polymer process monitoring.

Clad polymer buffer rods consisting of a polyetheretherketone (PEEK) core and a cladding made of a heat resistance epoxy aluminum composite are presented. The core has a uniform diameter or a taper shape. Ultrasonic measurement results indicate that the ultrasonic signal strength and signal to noise ratio of these clad rods are better than those of the non-clad PEEK rods for both longitudinal and shear waves because of the improved ultrasonic wave guidance in the core. Comparisons of these rods with those made of polymide and high-density polyethylene are given. Applications of these buffer rods for ultrasonic monitoring of polymer extrusion at temperatures up to 200 degrees C and pressures up to 180 psi are demonstrated. The monitoring results also reveal that within certain operating temperature and pressure range, clad polymer buffer rods show advantages over clad steel buffer rods.

Ultrasonic evaluation and application of oriented polymer rods

Ultrasonic evaluation and application of oriented high density polyethylene (HDPE) rods are presented. Solid state ram extrusion method is used to fabricate such rods. Ultrasonic measurement results indicate that the ultrasonic signal strength and signal to noise ratio of the oriented HDPE rods are better than those of the non-oriented ones for both longitudinal and shear waves. Viscosity measurements and monitoring of epoxy cure at ambient temperature using clad rods consisting of an oriented polymer core and an epoxy cladding are also demonstrated.

Materials evaluation using long clad buffer rods

Materials characterizations using long clad buffer rods with high spatial resolution and at high temperature are presented. The buffer rods consist of a fine grain steel core and thermal sprayed stainless steel cladding, and the lengths are up to 1 m. The signal to noise ratio (SNR) of the reflected signal at the end of buffer rods is better than 40 dB at 5 MHz. The thickness measurement for molten aluminum is demonstrated under industrial environment. In order to perform materials evaluation with a high spatial resolution, a spherical acoustic lens has been fabricated at the end of the rod and its focusing ability is investigated.

Ultrasonic in-line sensors for inclusion detection in liquid metals

A high temperature ultrasonic sensor for detecting inclusion particles in molten metals is presented. The sensor consists of a conventional piezoelectric transducer and a focused waveguide, and provides high spatial resolution measurements in molten metals in a pulse-echo mode at 10 MHz. A taper-shaped clad buffer rod is used as the waveguide. In order to design the waveguide, elastic wave propagation in the rod is evaluated by a numerical simulation using a finite difference method. Focusing ability of the acoustic lens fabricated at the end of the rod is also examined numerically. Using the developed sensor, backscattered echoes from alumina particles of 160 /spl mu/m suspended in molten aluminum at 1073 K have clearly been observed.

High temperature immersion type ultrasonic imaging probes

Ultrasonic probes for high temperature measurements in immersion are presented. These probes consist of piezoelectric transducers and buffer rods, are operated in the pulse-echo mode. The operating temperature is up to 215 °C and there is no need for a cooling system. For imaging purposes, one end of the clad buffer rod is attached with a piezoelectric transducer and the other end is machined into a semi-spherical concave shape that provides the focus. The operating frequency is 5 MHz. Ultrasonic images produced using mechanical raster scan and the measurements, when the probes are fully immersed in silicone oil at elevated temperatures, are presented. The importance of the signal-to-noise ratio in the pulse-echo measurement is discussed.

Recent progress in online ultrasonic process monitoring

On-line ultrasonic monitoring of polymer co-extrusion and gas-assisted injection molding are presented. During the co- extrusion of high density polyethylene and Santoprene ultrasonic sensors consisting of piezoelectric transducers and clad ultrasonic buffer rods are used to detect the interface between these two polymers and the stability of the extrusion. The same ultrasonic sensor also measures the surface temperature of the extruded polymer. The results indicate that temperature measurements using ultrasound have a faster response time than those obtained by conventional thermocouple. In gas-assisted injection molding the polymer and gas flow front positions are monitored simultaneously. This information may be used to control the plunger movement.

Ultrasonic in-situ monitoring of solidification and melting behaviors of an aluminum alloy

This paper presents a newly developed high temperature ultrasonic sensor (US) and its application to in-situ observation of Al alloy during solidification and melting in temperatures up to 800/spl deg/C. The US mainly consists of a conventional piezoelectric transducer and a Ti buffer rod as an acoustic waveguide. The length is 300 mm. This sensor, owing to the unique characteristics of Ti, is highly expected to provide not only high acoustic coupling to molten Al but also high corrosion resistance. It is demonstrated that the Ti buffer rod has superior sustainability and wettability to the molten Al alloy. Using the US, the changes of the longitudinal velocity of the Al alloy during solidification and melting have been monitored as a function of temperature. Furthermore, a clear reflected echo from the solid-liquid interface of the Al alloy has been observed. The movement of the reflected echo due to the growth of the solid-liquid interface has also been monitored during the cooling process. Thus, it is demonstrated that the developed US using a Ti rod is a promising tool for molten Al monitoring.

Ultrasonic temperature determination during industrial materials processing

Two technologies for measuring temperature with ultrasound during the processing of materials are presented. Both methods use clad buffer rods. These approaches present the great interest of being able of providing, in addition to the temperature measurement, the simultaneous monitoring of other parameters of the material being processed such as its elastic properties. The first method uses clad buffer rods with two steps machined at the probing end contacting the material being processed. The ultrasonic time delays in the two regions which are between the rod end and the first step, and between the first and the second step can be calibrated versus temperature variation. The measurement of these time delays during material processing, associated with a conduction heat transfer model provide an accurate temperature at the probing end. For molten zinc processing at temperature ranging between 350 and 700 °C, good agreement was obtained between the temperatures measured ultrasonically and those measured by ...

Ultrasonic In-Situ Monitoring of Aluminum Alloy During Solidification and Melting

In both research and production involving solidification of materials, it would be beneficial to have an in-situ, real-time characterization of the material properties during solidification process. In this work ultrasonic in-situ monitoring of aluminum alloy (Al-12.6%Si) during solidification and melting using a high temperature ultrasonic sensor is presented. The ultrasonic sensor used mainly consists of a conventional piezoelectric transducer, a titanium buffer rod as an acoustic waveguide and a cooling system. A steel reflector is assembled at the probing end of the sensor to make time-of-flight measurements. The sustainability of the sensor has been evaluated for long time immersion up to 16 hours in the molten aluminum alloy and the possible reaction at the outer wall of the titanium rod has been examined. It has been demonstrated that the titanium buffer rod has good wettability and sustainability to molten aluminum. Using the ultrasonic sensor, pulse echo measurements with the aluminum alloy have been performed in temperature range from 200 to 800 °C. The changes of the longitudinal velocity of the aluminum alloy during solidification and melting processes have been successfully monitored. In addition the change in the amplitude of reflected echoes during solidification is discussed.Copyright