Field of technology

The invention relates to an ultrasonic quality control of pieces. The pieces to be checked by ultrasonic probe or probes can be metal pieces, like metal cast pieces. Ultrasonic examination is comparative method and detects indications of imperfections and reflections of normal geometrical shapes inside the material or on surface of the examined object. Therefore the reflections of ultrasonic signal caused by interfaces with different acoustic impedance are referred as indications. Indications can be acceptable or rejectable. Indications caused by object geometry like front wall and back wall echo are referred as geometrical indications which are acceptable.

Prior art

Ultrasonic is a known way to inspect a piece, like a metal cast or forged piece, whether it comprises any faults. An ultrasonic probe is moved around the piece either manually or with an automated device in order to utilize high frequency sound waves penetrating through the piece. The sound waves propagate in the piece and part of the waves reflects from the surfaces of the piece and from the faults of the piece. The reflected waves can be detected and therefore used to detect the faults. The place, size and shape of the imperfection can be deduced from the reflected waves. It is also known to utilize more than one ultrasonic probe for the inspection.

The reflected waves are presented on a display of a device/system that is used for the inspection. An inspector checks the indications caused by imperfections on the display. In order to do that the inspector must have great professional skills and experience to make a proper analyze. If the indications are minor, the inspector can classify the piece to be accepted. If the piece comprises unacceptable imperfections or too many imperfections, the inspector should classify the piece as rejected as per criteria set forth. The ultrasonic scanning is suitable for using with many metals. However, some metallic materials may have limitations to be checked by the ultrasonic scanning, like large grain size austenitic steels.

So eventually, the skills of the inspector influence how good the inspection results are going to be. This can be problematic especially in cases where an inspector does not have so much experience yet and due to physical and psychological disturbances in normal performance or behavior.

Short description

The object of the invention is to alleviate or even eliminate the problematic factors said above. The object is achieved in a way described in the independent claims. Dependent claims illustrate different embodiments of the invention.

An ultrasonic quality control method of controlling a quality of a piece according to the invention comprises steps of scanning the piece utilizing at least one ultrasonic probe 101 ; forming at least one image from said scanning 102; scanning a reference piece utilizing at least one ultrasonic probe 103 and; forming at least one reference image from said scanning of the reference piece 104, Further the method has steps of forming at least one negative image of said at least one reference image 105; creating at least one indication image by utilizing said at least one image and the negative image 106; and filtering at least one indication image by utilizing several image filters, each image filter filtering all data of the indication image except an image filter specific indication level data 107. Further yet the method has steps of providing several indication levels data from the image filter specific indication level data 108; and classifying the piece to be accepted or rejected utilizing said several indication level data 109.

By utilizing the invention, the classification of the piece to be checked can be arranged to be made automatically. Further the classification is much faster than using known ways of the classification. List of figures

In the following, the invention is described in more detail by reference to the enclosed drawings, where

Figure 1 illustrates an example of a reference piece similar to be scanned with ultrasonic,

Figure 2 illustrates an example of a reference image from the reference piece,

Figure 3 illustrates an example of a negative image from the reference image,

Figure 4 illustrates an example of a piece to be scanned by ultrasonic,

Figure 5 illustrates an example of an image from the piece,

Figure 6 illustrates an example of an indication image,

Figure 7 illustrates an example of filtering the indication image containing indications and application of several indication levels data,

Figure 8 illustrates an example of a table showing a classification of indications of the example piece, and

Figure 9 illustrates an example of a piece having two areas wherein different classification criteria are used,

Figure 10 illustrates an example of a flow chart illustrating an inventive method, and

Figure 1 1 illustrates an example of a device according to the invention

Description of the invention

As already said above, a piece to be checked by an ultrasonic probe or several ultrasonic probes is known as such. Figure 4 shows an example of a piece 9 to be checked. It is noted that the piece of figure 4 is a schematic piece in order to make this presentation more clear than using a more complex piece. In any case the invention can be used with any piece that can be checked by ultrasonic scanning. The piece 9 of figure 4 has a front surface 94, a rear surface 95, a rectangular hole 96, an oval hole 97 and a projection 98 having an L -shape. The piece has some internal faults 10 like holes and cracks. After the scanning of the piece 9, an image 9R is formed that shows reflections of the ultrasonic scanning and can be presented as showed in figure 5. Figure 5 shows reflections from the front surface 94R, reflections from the rear surface 95R, reflections from the oval hole 97R, reflections from the rectangular hole 96R, reflections from the projection 98R and reflections from the faults 10R.

In this scanning example illustrated in figures 4 and 5 the ultrasonic probe is situated / or moved above the front surface 94. As can be seen, the reflection image of figure 5 may not be so clear in order to understand what it means. So, as said above, the experience and skills of the inspector must be at good level in order to find correct information from figure 5. Even if the inspector is experienced, the inspection of the reflection images can last a relatively long period and human factors may affect into interpretation result.

Figure 1 shows a reference piece 1 of the piece showed in figure 4. The reference piece 1 has also a front surface 4, a rear surface 5, a rectangular hole 6, an oval hole 7 and a projection 8 having an L -shape. But the reference piece has no faults or the faults of the reference piece are only minor faults, which can be accepted. In other words the reference piece is the similar piece than the piece to be checked without faults or with only minor faults. The reference piece 1 is also scanned like the piece to be checked. So the scanning device for the reference piece is the same or similar with the ultrasonic device used for the piece to be checked. As a result the reference image 2 of the ultrasonic reflections shows reflections from the front surface 4R, reflections from the rear surface 5R, reflections from the oval hole 7R, reflections from the rectangular hole 6R, and reflections from the projection 8R.

A negative image is formed from the reference image 2. Figure 3 shows the negative image 3. At this phase it should be noted that the reflections showed in Figure 2, 3 and 5 are presented as simple grey scale format in order to illustrate real reflection images in a simple way. As can be seen the grey scale levels of the negative image 3 are opposite with respect to the grey scale levels of figure 2. So, the negative image 3 shows also reflections from the front surface 4N, reflections from the rear surface 5N, reflections from the oval hole 7N, reflections from the rectangular hole 6N, and reflections from the projection 8N, but as negative with respect to the reference image 2.

The negative image 3 can be used with the reflection image 9R of the piece to be checked in order to create an indication image, which is showed in figure 6. The negative image and the reflection image from the piece to be checked are put one on the other. The order of the overlapping image can be either. As a result the indication image 9F is created. The overlapping negative image and the reflection image remove geometric reflections of the piece, i.e. the reflections from the front surface 94, reflections from the rear surface 95, reflections from the rectangular hole 96, reflections from the oval hole 97 and the reflections from the projection 98. The reflections from the faults 10R remain in the indication image 9F.

So, at this phase an image or data containing only indication information of the piece 9 is provided. In order to determine more accurately what kind of faults are in question, several filters can be used. Figure 7 illustrates the use of the filters F1 , F2, F3, F4 and F5. Each filter filters all data of the indications image 9F except an image filter specific indications level data. For example the filter can pass flat bottom holes whose size is 5 mm in diameter or larger. The other filter may pass flat bottom holes whose size is 4 mm in diameter or minor than 5 mm. Yet the other filter may pass flat bottom holes whose size is 3 mm in diameter or minor than 4 mm. Further other criteria can be used with the size of the flat bottom hole or instead of it. The filtering of indication image is based on the echo response strength/power/energy (echo height in apparatus screen and/or in collected data). Where small amount of power/energy reflection passes through a lower filter like F1 whereas higher power/energy passes through to higher filters like F4 or F5. So, criteria for component acceptability is based on the information provided by each filter. Further each filter may have its specific way to handle the reflections passing through the filter. For example, the filter may combine the reflections passing through as one if they are close to each other. So the higher filters like F4 and F5 may combine reflection data from a larger area than the lower filters like F1. This kind of handling can clarify the handling of the indications after the filters.

Therefore, acceptability of a piece can be/is based on the amount of indications, indication dimensions (size), amount of indications as combined area size of indications or to detections of indications close to each other with acceptable combination rule, which indications have passed through at least one filter, and being also visible after the filter/s if showed on a display. T combination rule can be defined so that if one indication after the filter is detected as indication or area, there is not allowed to be another indication/indication area near within certain dimension, for example . 20 mm. The image data can be in an image format or in another data format. In this context, an image should be understand as data, which can be represented as an image, but it can be represented also in any other suitable format. The same applies to the filters.

The example of figure 7 shows also several indication levels data illustrated as images 9F1 , 9F2, 9F3, 9F4, and 9F5. Each indication level data shows the indications that passed the specific filter. For example filter F1 has been arranged to pass flat bottom holes having size 1 mm in diameter or minor than 2 mm. Further the number of the holes should be for example16 at maximum and covering only certain area of the classification image in total like 45 mm ² and two indications separation shall be for example more than 10 mm of each other. The passed holes are represented as indications 10R1. Filter F2 may has been arranged to pass flat bottom holes having size 2 mm in diameter or minor than 3 mm. Further the number of the holes should be for example eight at maximum with similar or changed rules for area size and separation distance as defined for filter 10F. The passed holes are represented as indications10R2. Filter F3 may has been arranged to pass flat bottom holes having size 3 mm in diameter or minor than 4 mm. Further the number of the holes should be for example four at maximum with similar or changed rules for area size and separation distance as defined for filter 10F. The passed holes are represented as indications 10R3. Filter F4 may has been arranged to pass flat bottom holes having 4 mm in diameter or minor than 5 mm. Further the number of the holes should be for example two at maximum with similar or changed rules for area size and separation distance as defined for filter 10F. The passed holes are represented as indications 10R4. Filter F5 may has been arranged to pass flat bottom holes having 5 mm in diameter or greater where indications passing this filter level are defined to be not acceptable whatever in size, amount and area covered. The passed holes are represented as indications 10R5. This type of filters can have different rules for indication reflectivity size and there can be several non-acceptable filter levels depending of the inspected area criticality.

As can be seen, the indication data showed as images gives a clear view for a human inspector, but it is actually not yet a goal of this invention. At this level several indications levels are achieved which can also be studied, for example in image formats. As said each indication level indicates the severity of the indications like the sizes of the holes and cracks and a number of the indications areas covered by indications and proximity of indications. So the indications level data is information of a certain type of indications and possibly a number of those indications and other parameters describing the indications. The type of the indications can depend of the length, deep, shape, and /or size etc... A certain type of the indications has a certain impact to the quality of the piece.

In addition the invention also classifies the checked piece to be accepted or rejected utilizing said indication levels data. Referring to the example of figure 7 the piece can be accepted if it comprises only indications 10R1 passed filter F1. The piece may also be accepted if it comprises larger indications 10R2 that passed filter F2.

The piece 9 can also be classified as a border piece between the accepted pieces and rejected pieces. It may be possible that the border piece could be used in some lower lever implementation requiring not so high quality. In this example, the piece could be classified as the border piece if it comprises indications 10R3 that passed filter F3, and it does not comprise larger or more severe indications in amount, area and/or proximity of indications. The piece 9 can be rejected, if it comprises an indication or indications 10R5 passing filter 5. The piece can also be rejected, if it comprises minor indications than those passed the filter 5, like the indications 10R4 that passed filter 4.

Figure 8 and figure 9 show a possible example how the classification can also be arranged. Figure 9 shows the checked piece 9 having two areas A1 and A2. A dashed line in figure 9 describes the border between the areas. In this example area A1 is a low stressed area and area A2 is a high stressed area. The quality requirements are higher in the high stressed area, so fewer indications can be tolerated in area A2 than in area A1. Table 80 in figure 8 shows the acceptance criteria for area A2 and area A1. The area A1 of the piece can be accepted if it comprises only indications passed filter F1. The piece may also be accepted if it comprises larger indications that passed filter F2 in area A1. The area A1 of the piece 9 is classified as the border piece if it comprises indications that passed filter F3, and it does not comprise larger or more severe indications. The area A1 of the piece 9 is rejected if it comprises an indication or indications passing filter 5. The area A1 of the piece can also be rejected if it comprises minor indications than those passed the filter 5, like the indications that passed filter 4.

The high stressed area A2 of the piece 9 is rejected if it comprises an indication or indications passing filter 3. The piece can also be rejected if it comprises minor indications than those passed the filter 3, like the indications that passed filter 2. The area A2 of the piece 9 is classified as the border piece if it comprises indications that passed filter F1 , and it does not comprise larger or more severe indications.

As whole the piece 9 is rejected if it comprises any area that is rejected. In other words the piece is accepted if it does not comprise any rejected areas or possibly any border case areas. It can also be noted that the piece may have more than one area that is determined to be a high stressed area, and/or more than one area that is determined to be a low stressed area. In addition to the high stressed and low stressed areas the piece may also (or alternatively) have an area/s of other types, like a normal stressed area. As can be seen the piece can be divided into several areas of different stress requirements. This division information may follow with the scanned images to the indication images and finally up to the classification of the piece.

Figure 10 shows an example of a flow chart that illustrates the method according to the invention. An ultrasonic quality control method of controlling a quality of a piece 9 comprises steps of scanning the piece utilizing at least one ultrasonic probe101 , and forming at least one image from said scanning 102. As already said the scanning probe/s and scanning device and inspection data presentation format can be used. In addition, the method has steps for scanning a reference piece utilizing at least one ultrasonic probe 103, and forming at least one reference image from said scanning of the reference piece 104. The scanning of the reference piece 9 and the forming of the reference image are made similarly as the steps of scanning the piece 101 , and forming the image 102. Further the method has a step of forming at least one negative image of said at least one reference image 105. This step can be made as already discussed above.

The steps 103, 104 and 105 can be done after the steps 101 and 102 or before the steps 101 and 102 as illustrated by a dashed line 1 10 in figure 10. In some solutions it may be possible to run the steps 101 and 102 simultaneously or partly simultaneously with the steps 103, 104 and 105 if two similar ultrasonic probe/s and devices can be used.

Further, the method has a step of creating at least one indication image by utilizing said at least one image and the negative image 106. As described above, the negative image and the image of the piece to be checked are put one on the other in order to have the image having only indication information.

The method also has a step of filtering at least one indication image by utilizing several image filters, each image filter filtering all data of the indication image except an image filter specific indication level data 107. So in this way the method also has a step of providing several indication levels data from the image filter specific indication level data 108. Finally the method has a step of classifying the piece to be accepted or rejected utilizing said several or one indication levels data 109. The classification step can utilize, for example, a table wherein the indications levels data are arranged to correspond classification levels. The classification levels are an accepted level and a rejected level at minimum, but more classification levels can also be formed if needed. So, the classifying step 109 can further be arranged to classify the piece utilizing several levels of acceptance and several levels of rejections, and/or the classifying step 109 can further be arranged to classify the piece to be alternatively a border piece between said classifications of acceptance and rejection.

Further the classifying step 109 may comprise a substep of utilizing said several indication levels data filtered from the indication image in an indication image area specific way so that the indication image has at least two areas and the classification utilizes the several indication level data in an area specific way. See figure 9.

In order to make the classification of the piece to be more visible for humans the method may further comprise steps of indicating said classifications in classification specific colours in an image format/s corresponding the indication image/s, and displaying the image format/s. For example, the indication level images 9F1 , 9F2, 9F3, 9F4 and 9F5 in figure 7 can be represented in different colours or combination of colours. Image 9F1 can be light blue, image 9F2 blue, image 9F3 green, image 9F4 yellow, and image 9F5 red. So, each colour may represent a certain indications level data (for example indications of certain sizes/reflectivity). In addition each colour may also indicate a certain classification level. For example in case of figure 8 the rejection level may be red for both the low stressed area and the low stressed area. For the smaller indications rejection level the colour can be yellow and for the border piece level green at the both area categories. In addition the accepted level and the larger indications accepted level can be showed as blue and light blue in the low stressed area of the piece.

As said the image is data that can be showed, for example in a display. It should be understood that image data can also handled in another format, which makes it possible to process the image data in a processor, computers and other suitable devices. Said filters can also be filters that filter data from the original data and pass only a certain type of data, like data relating to a certain type of indications.

Figure 1 1 illustrates an example of a ultrasonic checking device according to the invention in a schematic way.

The ultrasonic checking device according to the invention can comprise at least one probe 1 1 1 , and a robot device 112 to move the probe/s. The probe/s is connected to at least one ultrasonic source device 1 13. The ultrasonic source device can be situated in any suitable location of the checking device. There is also a processor device 1 14, like a computer having certain software or a circuit board/s 115, to provide checking data from the received ultrasonic information from the probe/s. The checking data can be represented as an image/s. The checking device comprises also software or a circuit board/s 116 to perform the steps 103 - 109 of the method described above and in claim 1 , which software or the circuit board can also be arranged to perform the steps/tasks mentioned in claim 2 - 5. Said circuit board/s can, for example, be an integrated circuit (IC). It is also possible that said software or a circuit boards 115, 116 can be integrated as one entity.

Further the ultrasonic checking device may comprise a pool whereto the piece/s to be checked are situated, and the pool is filled with liguid. In addition, the checking device may also comprise other element/s like a rack for the piece, a rail for the rack, a computer vision device for identifying the piece, a reader device to read a serial number of the piece, a washer to wash the piece before putting it into the pool, a drier to dry the piece after the pool, and a market to mark the piece as checked.

The ultrasonic quality control according to the invention can be used in many different embodiments. The invention is not dependent on the ultrasonic scanning technique what is used. There exist several different scanning techniques, for example A-scanning, B-scanning, C-scanning, phased array linear scanning and phased array sectorial scanning, wherein the invention can be used. One image, one reference image, one negative image and one indication image may be enough in order to classify the piece, but it is also possible to take a number of images if needed. It should be understood that the corresponding images, i.e the image, reference image, negative image and the indication image area actually the same view from the piece, but containing different information. So, for example when forming a number of negative images from a number of reference images, each negative image to be formed is specific for the reference image that has a certain view from the piece. Negative image can be composed of several reference piece scanning images meaning that each scanning negative information is combined to one negative image. In this case the image whereto the negative image is used, can is similarly composed of several scanning images.

The inventive method can be run in a suitable device used for the ultrasonic scanning. The device may have a programmable unit or units, which can be programmed to perform the steps of the inventive method. Another possible solution is that the device has a printed circuits board or boards that are dedicated to perform the inventive method.

It is evident from the above that the invention is not limited to the embodiments described in this text but can be implemented in many other different embodiments within the scope of the independent claim.