Combined ultrasonic flaw detector

Abstract

The utility model discloses a combined ultrasonic flaw detector which comprises a combined mounting seat, a digital ultrasonic flaw detector, a plurality of digital ultrasonic probes, a phased array ultrasonic module and a plurality of phased array ultrasonic probes, the combined mounting seat comprises a first base and a second base, and the first base and the second base are detachably connected; a flaw detector mounting groove and a first probe positioning groove are formed in the first base, the digital ultrasonic flaw detector is locked in the flaw detector mounting groove, and each digital ultrasonic probe is placed in the first probe positioning groove; the second base is provided with an ultrasonic module mounting groove and a second probe positioning groove, the phased array ultrasonic module is locked in the ultrasonic module mounting groove, and each phased array ultrasonic probe is placed in the second probe positioning groove. The combined ultrasonic flaw detector can detect different positions of a wheel set according to requirements, has a comprehensive wheel set flaw detection function, and can effectively improve the wheel set flaw detection efficiency.

Description

Technical Field

[0001] The utility model relates to ultrasonic testing equipment, in particular to a combined ultrasonic flaw detector. Background Art

[0002] With the rapid development of my country's railways, more and more harmonious high-power locomotives are put into use. Heavy-duty freight high-power locomotives have the characteristics of heavy traction tonnage, and high-speed passenger locomotives have the characteristics of high operating speed. Under high-speed and high-load operation, wheelsets (including wheels and axles) are prone to fatigue defects of various orientations. Therefore, periodic flaw detection inspections of locomotive wheels and axles are necessary to ensure the safety of locomotive operation.

[0003] Currently, most locomotive depots still use conventional digital ultrasonic flaw detectors to perform conventional ultrasonic flaw detection on locomotive wheels and axles. These systems have developed a comprehensive wheel and axle flaw detection system encompassing incoming inspection, in-depot primary repair inspection, and in-depot advanced repair inspection. However, due to the large number and variety of locomotive models deployed by each locomotive depot, the workload is heavy. Conventional digital ultrasonic flaw detectors fail to modularize the ultrasonic flaw detection process for axles and wheels of all locomotive models. On-site flaw detection requires repeated setup and calibration, invoking the corresponding inspection process, and then performing flaw detection. This leads to a high level of repetitive work and low flaw detection efficiency.

[0004] At the same time, the conventional A-type scanning method cannot achieve graphical detection results and has poor intuitiveness. The judgment of defects depends entirely on the parameters of the A-scan waveform, the relative position of the probe, and the quality and experience of the flaw detector. It is easy to cause missed judgments and misjudgments, and the efficiency of manual flaw detection is low.

[0005] Phased array ultrasonic testing technology uses electronic methods to control the focusing, deflection and scanning of the sound beam. It can perform quick scanning without moving the probe or with minimal movement, thereby improving the detection speed. At the same time, it has good sound beam accessibility and can detect workpieces with complex geometric shapes. By optimizing the control of the focal size, focal depth and sound beam direction, the detection performance such as resolution, signal-to-noise ratio and sensitivity can be improved.

[0006] Currently, both are standalone devices. Phased array ultrasonic testing equipment, in addition to the phased array ultrasonic module, also comes with several auxiliary devices, such as automated travel and probe coupling. These devices are generally larger, and the two are typically used independently. If phased array ultrasonic testing can be combined with conventional ultrasonic testing, enabling the same testing equipment to select the appropriate testing method for different testing environments, the efficiency of wheelset flaw detection can be significantly improved. Utility Model Content

[0007] The technical problem to be solved by the utility model is to provide a combined ultrasonic flaw detector, which can detect different positions of the wheelset according to needs, has a comprehensive wheelset defect detection function, and can effectively improve the wheelset flaw detection efficiency.

[0008] In order to solve the above technical problems, the technical solutions adopted are as follows:

[0009] A combined ultrasonic flaw detector includes a digital ultrasonic flaw detector and multiple digital ultrasonic probes, wherein a signal output end of at least one digital ultrasonic probe is electrically connected to a corresponding signal input end of the digital ultrasonic flaw detector. The digital ultrasonic flaw detector is provided with an image display screen. The combined ultrasonic flaw detector is characterized in that it also includes a combined mounting base, a phased array ultrasonic module, and multiple phased array ultrasonic probes. The combined mounting base includes a first base, a second base, and a locking mechanism, the first base and the second base being detachably connected, and the locking mechanism being disposed between the first base and the second base. The first base is provided with a flaw detector mounting slot and a first probe positioning slot, the digital ultrasonic flaw detector is locked in the flaw detector mounting slot, and each of the digital ultrasonic probes is placed in the first probe positioning slot. The second base is provided with an ultrasonic module mounting slot and a second probe positioning slot, the phased array ultrasonic module is locked in the ultrasonic module mounting slot, and each of the phased array ultrasonic probes is placed in the second probe positioning slot. The signal output end of at least one phased array ultrasonic probe is electrically connected to a corresponding signal input end of the phased array ultrasonic module, and the signal output end of the phased array ultrasonic module is communicatively connected to the corresponding signal input end of the digital ultrasonic flaw detector.

[0010] The digital ultrasonic flaw detector is locked in the flaw detector installation slot, and the phased array ultrasonic module is locked in the ultrasonic module installation slot. Screw holes can be opened at corresponding positions on the base, and then the digital ultrasonic flaw detector and the phased array ultrasonic module are tightened by bolts.

[0011] When the combined ultrasonic flaw detector is not in use, the digital ultrasonic flaw detector, digital ultrasonic probe, phased array ultrasonic module and phased array ultrasonic probe can be placed in the corresponding mounting slots in the first base and the second base respectively. When the first base and the second base are detached, the digital ultrasonic flaw detector can be carried alone, and when they are connected, they can be carried together. In addition, multiple digital ultrasonic probes and phased array ultrasonic probes are stored in an orderly manner and can be replaced at any time as needed, making them convenient for storage or carrying. During testing, for routine testing that only requires the use of digital ultrasonic probes, the first base and the second base can be disassembled, and different digital ultrasonic probes can be used for testing according to the different positions of the axle or wheel; for testing that requires the use of phased array ultrasonics, the digital ultrasonic flaw detector and the phased array ultrasonic module need to be used together, and the data from the phased array ultrasonic probe is transmitted to the digital ultrasonic flaw detector, which then displays the image. This combined ultrasonic flaw detector combines conventional testing and phased array testing, so that different ultrasonic probes can be called and switched at any time according to the testing needs to perform different flaw detection tests, making the testing process modular. Therefore, it has a more comprehensive wheelset defect detection function, which can effectively improve the efficiency of wheelset flaw detection and eliminate the need for frequent replacement of testing equipment. At the same time, it is more convenient to carry and more convenient to test.

[0012] Conventional equipment can be used for the digital ultrasonic flaw detector and phased array ultrasonic module. The digital ultrasonic flaw detector is equipped with processes and process parameters for inspecting different locations on axles and wheels (e.g., conventional axle flaw detection, conventional wheel flaw detection, axle phased array flaw detection, and wheel phased array flaw detection, etc.), and these process parameters can also be directly and quickly stored, retrieved, and modified. The digital ultrasonic flaw detector collects, processes, and displays data detected by the digital ultrasonic probe. In addition to being equipped with different flaw detection processes and process parameters, the phased array ultrasonic module can also collect, process, and construct images of data detected by the phased array ultrasonic probe. The digital ultrasonic flaw detector displays the phased array image and, by directly matching the phased array image with the outline diagram of the axle or wheel, quickly determines the location of the defect.

[0013] The above-mentioned digital ultrasonic probes generally include small-angle probes, conventional straight probes, shear wave oblique probes, dual-crystal straight probes, conventional oblique probes for large-angle wheel detection, etc.; the above-mentioned phased array ultrasonic probes generally include axle end face position phased array probes, axle body surface position phased array probes, wheel rim detection phased array probes, wheel tread fan scan phased array probes, wheel tread line scan phased array probes, wheel large-angle phased array probes, etc.

[0014] In a preferred embodiment, a notch is formed in the side wall of the flaw detector mounting slot. The notch is formed in the side wall of the flaw detector mounting slot to avoid the adjustment knob of the digital ultrasonic flaw detector, facilitating operation and enabling the digital ultrasonic flaw detector to be directly installed on the bottom of the flaw detector mounting slot, thereby improving stability.

[0015] In a preferred embodiment, the first base is provided with a plug-in block, and the second base is provided with a corresponding plug-in slot, and the first base and the second base are plugged into each other. The plug-in block or the plug-in slot can be a single large-sized one or multiple small-sized ones; the plug-in method can achieve rapid assembly and separation.

[0016] In a further preferred embodiment, the locking mechanism is a Velcro, a lock, or an elastic clip disposed between the first base and the second base. The digital ultrasonic flaw detector, the digital ultrasonic probe, the phased array ultrasonic module, and the phased array ultrasonic probe are all very small and lightweight, and the first base and the second base can be combined by simply locking.

[0017] In a further preferred embodiment, the first and second bases are both made of plastic, and the locking mechanism is an elastic clip. The elastic clip includes a protrusion on the outer wall of the plug-in block and a protrusion groove on the side wall of the plug-in slot. The first and second bases are plugged into the plug-in slot via the plug-in block, and the protrusion is located in the protrusion groove. After the first and second bases are plugged into each other, since the first and second bases are both made of plastic, the protrusion can be snapped into the protrusion groove with slight deformation, thereby making the connection between the first and second bases more secure and convenient for one-handed carrying.

[0018] In a preferred embodiment, the inner sidewall of the first probe positioning slot is provided with a plurality of first partitions, each of which divides the first probe positioning slot into a plurality of side-by-side first positioning grids. The inner sidewall of the second probe positioning slot is provided with a plurality of second partitions, each of which divides the second probe positioning slot into a plurality of side-by-side second positioning grids. Each first positioning grid is used to accommodate a different digital ultrasound probe, and each second positioning grid is used to accommodate a different phased array ultrasound probe.

[0019] In a further preferred embodiment, each of the first and second positioning grids is provided with an elastic clamping member, each comprising two elastic sheets. The lower ends of the elastic sheets are fixedly mounted on the bottom wall of the corresponding first or second positioning grid, and the upper ends of the elastic sheets gradually expand toward each side into a trumpet shape. The digital ultrasound probe is positioned in the first positioning grid via the corresponding elastic sheet, and the phased array ultrasound probe is positioned in the second positioning grid via the corresponding elastic sheet. When the ultrasound probe is placed in the positioning grid, the elastic sheets can clamp the ultrasound probe, making it more secure and less likely to come loose.

[0020] In a preferred embodiment, the digital ultrasonic flaw detector is provided with a power socket, and the phased array ultrasonic module is provided with a power inlet. The power socket and the power inlet are electrically connected via a power cable. The digital ultrasonic flaw detector directly powers the phased array ultrasonic module via the power cable, thereby reducing the hardware space required for the phased array ultrasonic module.

[0021] The aforementioned phased array ultrasonic module and digital ultrasonic flaw detector are generally equipped with a communication interface. The communication connection between the phased array ultrasonic module and the digital ultrasonic flaw detector can be achieved by a network cable, where the communication interface on the digital ultrasonic flaw detector is connected to the communication interface on the phased array ultrasonic module via the network cable. Alternatively, a wireless connection can be achieved, where a wireless Wi-Fi network card is plugged into the communication interface of the digital ultrasonic flaw detector, and a wireless receiving module is plugged into the communication interface of the phased array ultrasonic module, where the digital ultrasonic flaw detector and the phased array ultrasonic module communicate via wireless Wi-Fi. (Providing a wireless Wi-Fi network card also enables rapid network data transmission. After the flaw detection is completed, the digital ultrasonic flaw detector can transmit the flaw detection records and reports via the network to a management system such as a computer.) The aforementioned connection method is conventional technology and is sufficient as long as it can transmit the data from the phased array ultrasonic module to the digital ultrasonic flaw detector.

[0022] The beneficial effect of the utility model is that the combined ultrasonic flaw detector can detect different positions of the wheelset according to needs, has a comprehensive wheelset defect detection function, and can effectively improve the efficiency of wheelset flaw detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the combined ultrasonic flaw detector in the embodiment of the present utility model when performing detection;

[0024] Figure 2 A top view of a combined mounting base, a digital ultrasonic flaw detector, and a phased array ultrasonic module in an embodiment of the present invention;

[0025] Figure 3 for Figure 2 A longitudinal sectional view of the first base along direction A;

[0026] Figure 4 It is a transverse cross-sectional view of the combined mounting seat in the embodiment of the present utility model. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0028] Example 1, as Figure 1-4The combined ultrasonic flaw detector shown includes a combined mounting base 1, a digital ultrasonic flaw detector 2, multiple digital ultrasonic probes 3, a phased array ultrasonic module 4, and multiple phased array ultrasonic probes 5. The combined mounting base 1 includes a first base 101, a second base 102, and a locking mechanism. The first base 101 and the second base 102 are detachably connected, and the locking mechanism is arranged between the first base 101 and the second base 102; the first base 101 is provided with a flaw detector mounting groove 1011 and a first probe positioning groove 1012, the digital ultrasonic flaw detector 2 is locked in the flaw detector mounting groove 1011, and each digital ultrasonic probe 3 is placed in the first probe positioning groove 1012 ; The second base 102 is provided with an ultrasonic module mounting slot 1021 and a second probe positioning slot 1022, the phased array ultrasonic module 4 is locked in the ultrasonic module mounting slot 1021, and each phased array ultrasonic probe 5 is placed in the second probe positioning slot 1022; the signal output end of each digital ultrasonic probe 3 is electrically connected to the corresponding signal input end of the digital ultrasonic flaw detector 2, and the digital ultrasonic flaw detector 2 is provided with an image display screen 201. The signal output end of each phased array ultrasonic probe 5 is electrically connected to the corresponding signal input end of the phased array ultrasonic module 4, and the signal output end of the phased array ultrasonic module 4 is communicatively connected to the corresponding signal input end of the digital ultrasonic flaw detector 2.

[0029] The digital ultrasonic flaw detector 2 is locked in the flaw detector mounting slot 1011, and the phased array ultrasonic module 4 is locked in the ultrasonic module mounting slot 1021. Screw holes can be opened at corresponding positions on the corresponding bases, and then the digital ultrasonic flaw detector 2 and the phased array ultrasonic module 4 are tightened by bolts.

[0030] When the combined ultrasonic flaw detector is not in use, the digital ultrasonic flaw detector 2, digital ultrasonic probe 3, phased array ultrasonic module 4, and phased array ultrasonic probe 5 can be placed in the corresponding mounting slots in the first base 101 and the second base 102, respectively. When the first base 101 and the second base 102 are separated, the digital ultrasonic flaw detector 2 can be carried alone, and when they are connected, they can be carried together. In addition, multiple digital ultrasonic probes 3 and phased array ultrasonic probes 5 are stored in an orderly manner and can be replaced at any time as needed, making them convenient for storage or carrying. During testing, for routine testing that only requires the use of the digital ultrasonic probe 3, the first base 101 and the second base 102 can be disassembled, and the first base 101 can be removed. Different digital ultrasonic probes 3 can be used for testing according to the different positions of the axle or wheel. For testing that requires phased array ultrasonic testing, the digital ultrasonic flaw detector 2 and the phased array ultrasonic module 4 need to be used together, and the detection using the phased array ultrasonic probe 5 is performed. The data is transmitted to the digital ultrasonic flaw detector 2, and the digital ultrasonic flaw detector 2 displays the image. This combined ultrasonic flaw detector combines conventional testing and phased array testing, so that different ultrasonic probes can be called and switched at any time according to the testing needs to perform different flaw detection tests, making the testing process modular. Therefore, it has a more comprehensive wheelset defect detection function, which can effectively improve the efficiency of wheelset flaw detection and eliminate the need for frequent replacement of testing equipment. At the same time, it is more convenient to carry and more convenient to test.

[0031] The digital ultrasonic flaw detector 2 is equipped with processes and process parameters for inspecting different locations on axles and wheels (e.g., conventional axle flaw detection, conventional wheel flaw detection, axle phased array flaw detection, and wheel phased array flaw detection processes and process parameters, and these process parameters can also be directly and quickly stored, retrieved, and modified). The data detected by the digital ultrasonic probe 3 is collected, processed, and displayed by the digital ultrasonic flaw detector 2. In addition to being equipped with different flaw detection processes and process parameters, the phased array ultrasonic module 4 can also collect, process, and construct images of the data detected by the phased array ultrasonic probe 5. The digital ultrasonic flaw detector 2 then displays the phased array image. By directly matching the phased array image with the outline diagram of the axle or wheel, the location of the defect can be quickly determined.

[0032] The above-mentioned digital ultrasonic probe 3 generally includes a small-angle probe, a conventional straight probe, a shear wave oblique probe, a dual-crystal straight probe, a conventional oblique probe for large-angle wheel detection, etc.; the above-mentioned phased array ultrasonic probe 5 generally includes an axle end face position phased array probe, an axle body surface position phased array probe, a wheel rim detection phased array probe, a wheel tread fan scan phased array probe, a wheel tread line scan phased array probe, a wheel large-angle phased array probe, etc.

[0033] A notch 10111 is provided on the side wall of the flaw detector installation slot 1011. The notch 10111 is provided on the side wall of the flaw detector installation slot 1011 to avoid the adjustment knob of the digital ultrasonic flaw detector 2, making it easier to operate and allowing the digital ultrasonic flaw detector 2 to be directly installed on the bottom of the flaw detector installation slot 1011, thereby improving stability.

[0034] The first base 101 is provided with a plug-in block 1013, and the second base 102 is provided with a corresponding plug-in slot 1023. The first base 101 and the second base 102 are plugged into each other. The plug-in block 1013 or the plug-in slot 1023 can be a single large-sized one or multiple small-sized ones; the plug-in method can achieve rapid assembly and separation.

[0035] Both the first and second bases 101, 102 are made of plastic. The locking mechanism is an elastic clip disposed between the first and second bases 101, 102. The elastic clip includes a protrusion 10131 on the outer wall of the plug-in block 1013 and a protrusion groove 10231 on the side wall of the plug-in slot 1023. The first and second bases 101, 102 are plugged into each other via the plug-in block 1013 and the plug-in slot 1023, with the protrusion 10131 located in the protrusion groove 10231. The digital ultrasonic flaw detector 2, digital ultrasonic probe 3, phased array ultrasonic module 4, and phased array ultrasonic probe 5 are all very small and lightweight, and a simple locking mechanism can be used to connect the first and second bases 101, 102. After the first base 101 and the second base 102 are plugged in, since the first base 101 and the second base 102 are both made of plastic, the protrusions can be stuck into the protrusion grooves through slight deformation, thereby making the connection between the first base 101 and the second base 102 more secure and convenient for one-handed carrying.

[0036] The inner sidewall of the first probe positioning slot 1012 is provided with a plurality of first partitions 10121, each of which divides the first probe positioning slot 1012 into a plurality of side-by-side first positioning grids 10122. The inner sidewall of the second probe positioning slot 1022 is provided with a plurality of second partitions 10221, each of which divides the second probe positioning slot 1022 into a plurality of side-by-side second positioning grids 10222. Each first positioning grid 10122 is used to accommodate a different digital ultrasound probe 3, and each second positioning grid 10222 is used to accommodate a different phased array ultrasound probe 5.

[0037] Each first and second positioning grid 10122 and 10222 is provided with an elastic clamping member 6. The elastic clamping member 6 comprises two elastic sheets 601. The lower ends of the elastic sheets 601 are fixedly mounted on the bottom wall of the corresponding first or second positioning grid 10122, 10222. The upper ends of the elastic sheets 601 gradually expand outwards into a trumpet-like shape. The digital ultrasound probe 3 is placed in the first positioning grid 10122 via the corresponding elastic sheet 601, and the phased array ultrasound probe 5 is placed in the second positioning grid 10222 via the corresponding elastic sheet 601. When the ultrasound probe is placed in the positioning grid, the elastic sheets 601 can clamp the ultrasound probe, making it more secure and less likely to come loose.

[0038] The digital ultrasonic flaw detector 2 is provided with a power socket, and the phased array ultrasonic module 4 is provided with a power plug. The power socket and the power plug are electrically connected via a power cable 7. The digital ultrasonic flaw detector 2 directly powers the phased array ultrasonic module 4 via the power cable, reducing the hardware space of the phased array ultrasonic module 4.

[0039] The digital ultrasonic flaw detector 2 and the phased array ultrasonic module 4 themselves are generally provided with a communication interface. The communication connection between the phased array ultrasonic module 4 and the digital ultrasonic flaw detector 2 adopts a wireless connection, that is, a wireless WIFI network card is plugged into the communication interface of the digital ultrasonic flaw detector 2, and a wireless receiving module is plugged into the communication interface of the phased array ultrasonic module 4. The digital ultrasonic flaw detector 2 and the phased array ultrasonic module 4 are connected to each other via wireless WIFI (the provision of a wireless WIFI network card can also realize rapid network transmission of data. After the flaw detection is completed, the digital ultrasonic flaw detector 2 can transmit the flaw detection records and reports to a management system such as a computer through the network).

[0040] Example 2. The difference between this example and Example 1 is that the phased array ultrasonic module and the digital ultrasonic flaw detector are connected by a network cable, that is, the communication interface on the digital ultrasonic flaw detector is connected to the communication interface on the phased array ultrasonic module via a network cable.

Claims

1. A combined ultrasonic flaw detector comprising a digital ultrasonic flaw detector and multiple digital ultrasonic probes, wherein a signal output terminal of at least one digital ultrasonic probe is electrically connected to a corresponding signal input terminal of the digital ultrasonic flaw detector, and the digital ultrasonic flaw detector is provided with an image display screen, characterized in that: It also includes a combined mounting base, a phased array ultrasonic module and multiple phased array ultrasonic probes. The combined mounting base includes a first base, a second base and a locking mechanism. The first base and the second base are detachably connected, and the locking mechanism is arranged between the first base and the second base; the first base is provided with a flaw detector mounting slot and a first probe positioning slot, the digital ultrasonic flaw detector is locked in the flaw detector mounting slot, and each of the digital ultrasonic probes is placed in the first probe positioning slot; the second base is provided with an ultrasonic module mounting slot and a second probe positioning slot, the phased array ultrasonic module is locked in the ultrasonic module mounting slot, and each of the phased array ultrasonic probes is placed in the second probe positioning slot; the signal output end of at least one phased array ultrasonic probe is electrically connected to the signal input end corresponding to the phased array ultrasonic module, and the signal output end of the phased array ultrasonic module is communicatively connected to the signal input end corresponding to the digital ultrasonic flaw detector.

2. A combined ultrasonic flaw detector according to claim 1, characterized in that: A notch is provided on the side wall of the flaw detector installation slot.

3. The combined ultrasonic flaw detector according to claim 1, characterized in that: The first base is provided with a plug-in block, and the second base is provided with a corresponding plug-in slot, and the first base and the second base are plugged into and matched with each other.

4. A combined ultrasonic flaw detector according to claim 3, characterized in that: The locking mechanism is a Velcro, a lock or an elastic clip arranged between the first base and the second base.

5. A combined ultrasonic flaw detector according to claim 4, characterized in that: The first base and the second base are both made of plastic, and the locking mechanism is an elastic clip. The elastic clip includes a protrusion arranged on the outer side wall of the plug-in block and a protrusion groove arranged on the side wall of the plug-in slot. The first base and the second base are plugged into the plug-in slot through the plug-in block, and the protrusion is in the protrusion groove.

6. The combined ultrasonic flaw detector according to claim 1, characterized in that: The inner side wall of the first probe positioning groove is provided with multiple first partitions, and each first partition divides the first probe positioning groove into multiple side-by-side first positioning grids; the inner side wall of the second probe positioning groove is provided with multiple second partitions, and each second partition divides the second probe positioning groove into multiple side-by-side second positioning grids.

7. A combined ultrasonic flaw detector according to claim 6, characterized in that: Each of the first positioning grid and the second positioning grid is respectively provided with an elastic clamping member, and the elastic clamping member includes two elastic sheets. The lower end of the elastic sheet is fixedly mounted on the bottom wall of the corresponding first positioning grid or the second positioning grid, and the upper end of the elastic sheet gradually opens to both sides into a trumpet shape. The digital ultrasonic probe is placed in the first positioning grid through the corresponding elastic sheet, and the phased array ultrasonic probe is placed in the second positioning grid through the corresponding elastic sheet.

8. The combined ultrasonic flaw detector according to claim 1, characterized in that: The digital ultrasonic flaw detector is provided with a power supply socket, and the phased array ultrasonic module is provided with a power supply insertion port. The power supply socket and the power supply insertion port are electrically connected through a power supply cable.

Images