Patent Application
20100242607
The subject matter disclosed herein relates generally to non-destructive ultrasonic testing methods and, more particularly, to an ultrasonic inspection method for determining locations of incipient damage such as mechanical failure.
One of the important applications of non-linear ultrasound (NLU) is in inspection of operating parts for any signs of damage. High frequency ultrasonic signals at a fundamental frequency are transmitted toward an area of interest. Any damage or irregularity in the path of the transmitted ultrasonic signals will generate harmonic components of the fundamental frequency. The fundamental frequency component and harmonic components are received and analyzed to assess the condition of the part for signs of incipient damage. Based on the inspection data, the part can be repaired or withdrawn from service.
A part can be inspected at different stages of its operating life. At each stage, the part is inspected to determine signs of incipient damage. Suitable inference such as identifying location of damage would be made based on the inspection conducted at a particular stage. But a part undergoes alternating softening and hardening and the incremental increase between inspections can be very small. Therefore, relying on results from a single inspection will not be conclusive and can be misleading. Also, failures happen when damage localizes and accumulates in one location. A single inspection would not be able to identify this accumulated damage condition.
It would therefore be desirable to provide an inspection methodology to effectively determine a location of incipient damage by capturing damage accumulation.
In accordance with one embodiment disclosed herein, a method for determining a location of incipient damage of an object comprises insonifying the object at a plurality of locations using ultrasonic signals during an inspection, acquiring signals indicative of a possible damage condition from the plurality of locations of the insonified object in said inspection, determining a value for each of the locations to indicate accumulated damage by mathematically combining the acquired signals from said inspection and at least a portion of prior inspections, and comparing the values of the plurality of locations to determine a location indicating possible incipient damage.
In accordance with another embodiment disclosed herein, a method for determining a location of incipient damage of an object comprises insonifying the object at a plurality of locations using ultrasonic signals during an inspection, acquiring signals indicative of a possible damage condition from the plurality of locations of the insonified object in said inspection, averaging the acquired signals from said inspection and at least a portion of prior inspections corresponding to their respective locations to have a cumulative average for each of the locations, and comparing the cumulative averages of the plurality of locations to determine a location indicating possible incipient damage.
In accordance with another embodiment disclosed herein, a non-linear ultrasound inspection method for determining a location of incipient damage of an object comprises insonifying the object at a plurality of locations using ultrasonic signals at a fundamental frequency during an inspection, acquiring signals indicative of a possible damage condition from the plurality of locations of the insonified object in said inspection, averaging the acquired signals from said inspection and at least a portion of prior inspections corresponding to their respective locations to have a cumulative average for each of the locations, and comparing the cumulative averages of the plurality of locations to determine a location indicating possible incipient damage. The acquired signals comprise the fundamental frequency and a harmonic component of the fundamental frequency.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Embodiments disclosed herein include an inspection method for determining locations of incipient damage or mechanical failure. Briefly stated, the inspection method first includes insonifying the object at a plurality of locations using ultrasonic signals during an inspection. Signals indicative of a possible damage condition are then acquired from the plurality of locations of the insonified object in said inspection. A value to indicate accumulated damage is determined for each of the locations using the acquired signals from said inspection and prior inspections. The values of the plurality of locations are then compared to determine a location indicating possible incipient damage. As used herein, singular forms such as “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
The values of all the locations are compared at block 18 to determine a location indicating possible incipient damage. In one embodiment, the value includes a cumulative average. The acquired signals for each of the locations are averaged over an inspection I0 and all prior inspections I−1 to I−m to have a cumulative average for each of the locations on the object. The acquired signals indicate extent of a damage condition. Therefore, accumulated damage at a particular location can be indicated by cumulative average. A higher value of cumulative average indicates a possible incipient damage. The detailed process of determining a location of incipient damage will be explained in reference to
The transmit/receive unit 54 insonifies the object by transmitting ultrasonic signals at fundamental frequency f0 56. The object 52 is insonified at a plurality of locations. In response to the incident signals at fundamental frequency 56, signals at fundamental frequency 58 and harmonic components 60 of the fundamental frequency are generated. The transmit/receive unit acquires signals at fundamental frequency 58 and at least one harmonic component 60 of the fundamental frequency. In one embodiment, signals are acquired as a ratio of amplitudes of the fundamental frequency component f0 58 and the second harmonic component 2f0 60. In another embodiment, the acquired signal comprises ratio of the amplitude “A(2f0)” of the second harmonic component 60 to the square of the amplitude “A(f0)” fundamental frequency component f0 58.
Locations 62 on the object can be selected in several ways depending on the size, shape, and design of the object. For example, for the object 52 shown in
An inspection can include multiple inspection trials. A single inspection trial includes the process of insonifying the object 52 at plurality of locations 62 (for example, 1 to 16) and acquiring signals corresponding to the plurality of locations 62. Inspection trials can be performed on all sides the object 52. Inspection trials can also be performed along several lines 64 on the same side of the object for the plurality of locations 62. The acquired signals from all the inspection trials of an inspection are corresponded to the locations 62 and are averaged to have an average for each of the locations 62.
The averages of acquired signals for each of the locations 62 obtained during an inspection are stored in a processing unit 66. At an inspection, the processing unit 66 calculates a cumulative average of the acquired signals for each of the locations 62. The cumulative average is calculated by averaging the acquired signals from a current inspection and prior inspections corresponding to their respective locations 62.
Since the amplitude of the harmonic components can be related to damage condition, the magnitude of the acquired signals, and hence the magnitude of cumulated average, is indicative of a damage condition and suitable inference about incipient damage can be drawn. Damage conditions can refer to micro-structural features, such as dislocations, that distort the input ultrasonic waves and give rise to harmonics. Examples of damage conditions include fatigue, creep, or creep-fatigue. Therefore, the processing unit 66 compares cumulative averages of the locations 62 and determines a location with relatively higher cumulated average that is indicative of possible incipient damage.
Inspection I0 is assumed as a current inspection and prior inspections are represented as I−1, I−2, . . . , I−m. As another example, at an inspection I−m, all the signals acquired corresponding to location ‘n’ are averaged to have an average that is represented as A−m,n, with ‘m’ in subscript representing the inspection and ‘n’ in subscript representing the location number.
At the inspection I0, cumulative averages for each of the locations are calculated by averaging the acquired signals from the inspection I0 and the prior inspections I−1 to I−m corresponding to their respective locations. For example, cumulative average “C1” for location ‘1’ is calculated by the averaging A0,1, A−1,1, A−2,1, . . . , A−m,1. The cumulative averages “C1, C2, . . . , Cn” are then compared to determine a location with maximum cumulative average. As stated previously, the magnitude of the acquired signals, and hence the magnitude of cumulated average, is indicative of the extent of damage. Therefore, the location with maximum cumulative average indicates possible incipient damage compared to other locations.
As the number of inspections increase, the accumulated damage is more conclusively represented by the cumulative average. For example, cumulative average at location ‘36’ gradually increases and is higher compared to other locations from inspection ‘4’. This kind of trend represents accumulated damage at location ‘36’ and therefore indicates possible incipient damage at location ‘36’ compared to other locations.
Relying on data from a single inspection, without using cumulative average, will not capture this trend of accumulated damage. A higher value of an acquired signal from a single inspection may not be conclusively taken as a sign of accumulated damage.
The inspection method described above thus provides a way to conclusively determine a location of incipient damage of an object by capturing accumulated damage over several inspections. The method suppresses spikes or any unusual data from a single inspection that may lead to inappropriate conclusions. Once a location of possible incipient damage is determined, the object can be salvaged before further damage such as crack initiation, leading to significant cost savings. The object can be repaired using various processes, such as, but not limited to, brazing and laser powder deposition. Therefore, the service life of an object can be extended.
It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
