Measuring and testing – Vibration – Resonance – frequency – or amplitude study
Patent
1987-08-14
1989-05-16
Levy, Stewart J.
Measuring and testing
Vibration
Resonance, frequency, or amplitude study
G01N 2900
Patent
active
048298239
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus for detecting faults in workpieces, particularly in foundry, metallurgical workpieces etc so that, after manufacture, the workpieces having faults which are too great can be sorted out. The apparatus detects the material faults which have an influence on the elasticity of the material such as the nodularity rate variations of the spheroidal graphite melts or the thermal treatments, the overall defects of geometry due for example to the opening, to the wear or to the offcentering of the molds, localized defects such as cracks, shrinkage holes . . .
Several techniques already exist for providing such detection. There exist for example systems for testing work pieces by resonance which use a hammer which strikes the work piece, the sound picked up by a micrphone or by induction in a solenoid is then filtered so as to select one of the resonance frequencies from the set of frequencies characteristic of the work piece, this frequency is then compared with a given threshold.
Since the resonance frequencies depend on variables such as the characteristics of the material (coefficient of elasticity and density), shapes or dimensions of the work piece and pin point defects, a method such as the one which has just been described which only uses a single one of the resonance freqeuencies does not allow the different variables to be determined, since a single equation is obtained with several unknowns.
Furthermore, the method which consists in energizing the work piece by shocks so as to analyse the spectrum thereof has the drawback of being difficult to use in the work shop for the signal to be analysed is greatly disturbed by the ambient speech and noises, and it is difficult to mesaure the resonance frequencies with a low overvoltage, for this technique would require analysis of the signal by Fourier transform for example which would be long and expensive in order to obtain the required precision.
Considering the interest shown by constructors in having a reliable, rapid and automatable testing tool, the purpose of the invention is to provide apparatus overcoming the different above mentioned drawbacks, by successively exciting the different resonances characteristic of the work piece so as to measure the frequency thereof and possibly the over voltage and by processing the data collected which leads to obtaining the different characteristics of the work piece,
The invention relates more precisely to an apparatus for detecting defects in work pieces, particularly in foundry or metallurgical work pieces, including a plurality of pairs for exciting and picking up the vibrations emitted by a work piece, whose sound resonance frequencies it is desired to measure so as to evaluate the quality thereof.
The invention will be better understood from the following explanations and the accompanying Figs. in which:
FIG. 1 illustrates schematically an apparatus in accordance with the invention, and
FIG. 2 is a diagram illustrating a measurement generation and processing circuit in accordance with the invention. For greater clarity, the same elements bear the same references throughout the Figs.
As shown in FIG. 1, vibration exciting and sensing pairs are disposed close to the work piece 1 to be tested, for example (EA1, M1 and EA2, M2).
The exciters EA1, EA2 and sensors M1, M2 are connected to a measurement generation and processing circuit 2. In this example, only two exciting and sensing pairs are shown which allow, for example, the vertical vibration modes to be measured for EA2 and the horizontal modes for EA1, but it is possible to extend the method by adding other pairs so as to obtain rotational resonsance modes for example.
Work piece 1 is laid on a support (not shown), and preferably made from a resilient material which does not damp the vibrations, so that the position of the support with respect to the vibration nodes becomes less critical.
In the example described, exciter EA1 and/or EA2 is an electromagnet whose coil 3 has a current flowing therethrough, the vibration se
REFERENCES:
patent: 4122723 (1978-10-01), Levizzari et al.
patent: 4297884 (1981-11-01), Leveque et al.
Arana Louis M.
Levy Stewart J.
Plottel Roland
LandOfFree
Apparatus for detecting defects, particularly in castings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for detecting defects, particularly in castings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for detecting defects, particularly in castings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2313632