Measuring and testing – Vibration – By mechanical waves
Patent
1994-02-23
1996-07-09
Williams, Hezron E.
Measuring and testing
Vibration
By mechanical waves
73602, G01N 2908, G01N 2918
Patent
active
055334113
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method and an apparatus for ultrasonic measurement. More particularly, this invention relates to a method by which the values of physical characteristics such as tensile strength, percent elongation, and the percent spheroidicity of graphite, as well as the values of state analysis, can be measured or calculated on castings such as gray cast iron, CV cast iron, and spheroidal graphite cast iron by ultrasonic waves in a nondestructive manner. The invention also relates to an apparatus for implementing the method for ultrasonic measurement.
BACKGROUND ART
Both the manufacturer and the user of a machine part generally have serious concerns as to whether that part is truly made of a material to specifications. This is because the use of an incorrect or defective material has high potential to lead directly to a disastrous accident due to failure of the part.
Therefore, the manufacturer makes it a rule to conduct materials tests on each of the parts produced, and guarantees the authenticity of an individual part by issuing a materials test performance list which certifies that it has been produced from the material to specifications. In the case of cast iron products, the materials tests to be conducted include a tensile test and a hardness test. As for spheroidal graphite iron products, an additional test is conducted to determine the percent spheroidicity of graphite.
While this is generally the basic way adopted to certify the authenticity of materials, materials tests require about three or four days including the processing of test pieces and other steps, so the manufacturer has desired the development of a method that enables various materials characteristics to be estimated in a simpler and quicker way.
On the side of the user, a need exists for verifying on the actual sample that the part of interest is truly made of the material to specifications. However, to prepare a test piece for materials testing, the actual sample must be broken, and it has been desired to develop a method by which tensile strength and other properties can satisfactorily be estimated in a nondestructive manner.
As for the test to estimate the percent spheroidicity of graphite in spheroidal cast irons to be evaluated by various materials tests, an apparatus for ultrasonic measurement was developed in the early eighties that was capable of indirect determination of the percent spheroidicity of graphite using the fact that the velocity of sound (the term "sound velocity" as used herein means the speed of propagation of ultrasonic waves) varied with the shape of graphite particles.
A block diagram of an apparatus that measures the sound velocity on a cast specimen by ultrasonic wave and which computes automatically the percent spheroidicity of graphite in the specimen is shown in FIG. 16.
In the drawing, numeral 1 designates an ultrasonic probe, 2 is an ultrasonic flaw detector, 3 is a D/A converter circuit, 4 is a bus line, 5 is a ROM, 6 is a RAM, 7 is a keyboard (KBD), 8 is a CRT, and 9 is a microprocessor (MPU). Details of interface circuits and the like that are connected between these components are omitted from FIG. 16.
Further referring to FIG. 16, numeral 51 designates a program for measuring the sound velocity, 52 is a program for computing the percent spheroidicity, 53p is a V-S conversion formula, and 54p is a main program; these programs are stored in ROM 5 and executed by MPU 9 to perform the functions they are assigned respectively.
Sound velocity measuring program 51 is activated by main program 54p when it is instructed to start measurement via keyboard 7, and the ultrasonic flaw detector 2 is controlled via bus line 4 to measure the sound velocity on the specimen 1a. Stated more specifically, the ultrasonic wave sent from the ultrasonic probe 1 is partly reflected by the surface of the specimen 1a, whereas the remainder propagates through the interior of the specimen 1a and is also reflected by its bottom. These reflected waves are detected with the ultrasonic probe 1 a
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patent: 3774444 (1973-11-01), Kent
patent: 3844163 (1974-10-01), Di Leo
patent: 3848460 (1974-11-01), Bantz et al.
patent: 4114455 (1978-09-01), Walker
patent: 4386527 (1983-06-01), Maucher
Finley Rose M.
Hitachi Construction Machinery Co. Ltd.
Williams Hezron E.
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