Improved positioning table for shock excitation measurements.

Abstract

The present invention relates to an Impact Excitation (IE) measurement system for measuring a vibration response of a solid piece to an impulse impact, comprising: an impactor for impacting the solid piece; a sensor for obtaining a vibration response of the solid piece to the impact; a support system for supporting the solid piece during the impact and obtaining the vibration response; a positioning table comprising a piece holder configured to receive the solid piece at a predetermined holder position relative to the piece holder; and an actuator operatively connected to the piece holder configured to transport the piece holder with the solid piece at the predetermined holder position to the support system, to place the solid piece at the predetermined support position on the support system, and to displace the piece holder such that the solid piece is supported only by the support system during the impact and obtaining the vibration response.

Description

[Technical field]

[0001] The present invention relates to the field of non-destructive impact excitation measurement of solid pieces, in which information about the solid pieces is obtained by subjecting the solid pieces to an impulse impact and recording and analyzing the vibration response of the solid pieces. The present invention is particularly useful for non-destructively and quantitatively assessing the quality of 3D printed solid pieces.

[0002] background Additive Manufacturing (AM), also known as three-dimensional or 3D printing, is a process that has gained a lot of momentum in recent years. It allows for the construction of three-dimensional objects from CAD or digital 3D models. It allows materials to be deposited, joined, or solidified under controlled conditions to create three-dimensional objects, where materials such as liquid molecules or powder particles are fused together, typically layer by layer. The precision, repeatability, and material range of 3D printing have increased to the point where some 3D printing processes are considered viable as industrial manufacturing techniques. One of the key advantages of 3D printing is its ability to produce highly complex shapes or geometries that would otherwise be impossible to build by hand, including hollow parts or parts with internal truss structures for weight reduction.

[0003] It is often necessary to ensure that 3D printed pieces meet required quality standards and be able to detect and characterize anomalies, therefore it is important to have metrology tools for mechanical characterization as well as proper anomaly detection, quality control, and monitoring.

[0004] Knowing when deviations of various types and quantities from expected values ​​appear increases the likelihood of early detection of critical defects in additively manufactured parts and provides potential opportunities for in-process intervention, thus reducing the time and cost of repair or rework. Because AM processes involve incremental deposition of material, they provide a unique opportunity to monitor the quality of the material as it is deposited. To meet this need, there are various sensing methods and signals that can be measured. Among the available measurement modalities, acoustic-based methods have the advantage of potentially providing real-time, continuous, in-service monitoring of the manufacturing process at a relatively low cost.

[0005] Taheri, Hossein's PhD thesis "Nondestructive evaluation and in-situ monitoring for metal additive manufacturing" (2018), Iowa State University Research Paper No. 16675, discloses a method to monitor AM processes in situ. Proof of concept is demonstrated for acoustic measurements used to monitor both mechanical and material conditions. Analysis is performed on temporal and spectral features extracted from the acoustic signals. These features are generally related to defect formation and acoustic noise that may be generated and characterize the process. A novel application of signal processing tools is used to identify temporal and spectral features of the acoustic signals. The method involves obtaining acoustic measurements during the AM process and attempting to extract information from them. This is expected to involve complex analysis, which may be highly dependent on the exact manufacturing method and materials used.

[0006] US Patent Application Publication No. 2019 / 234908 discloses an object analysis including measuring a frequency-dependent natural vibration behavior of an object by dynamically mechanically exciting the object in a specified frequency range (f) by applying a test signal to generate object vibrations, and detecting object vibrations generated in the object due to the excitation. The method further includes simulating the frequency-dependent natural vibration behavior of the object by generating a virtual digital representation of the object, and performing a finite element analysis based on the virtual representation, where performing the finite element analysis includes dynamically exciting the virtual representation in a simulated manner to a virtual frequency range to generate virtual object vibrations, calculating the virtual object vibrations generated in the object by exciting in the simulated manner, and deriving an object state based on a comparison between the measured natural vibration behavior and the simulated frequency-dependent natural vibration behavior.

[0007] EP 3309544 A1 discloses a method for in-process monitoring of a 3D printing apparatus or quality control of a 3D printed structure. The method includes a generating step of generating acoustic waves in the 3D printed structure. A receiving step receives the acoustic waves using a microphone array. An analyzing step analyzes a frequency spectrum of the acoustic waves. A determining step determines whether the frequency spectrum is indicative of a defect in the 3D printed structure.

[0008] US Patent Application Publication No. 2020 / 057030 discloses a system and method for non-destructive testing of additively manufactured parts. An input mechanism excites an additively manufactured build structure, including a part on a build platform, with an excitation force (e.g., vibration) to induce a dynamic response in the part. An output mechanism (e.g., a non-contact transducer) senses the induced dynamic response in the part. A processor determines and examines a relationship between the response and the excitation to identify indicators of defects in the part and communicates an alert if an indicator is identified. The processor can compare the phase, magnitude, coherence, or time delay of the relationship to a reference relationship, and / or compare modal frequencies or modal damping to a reference to identify deviations greater than a pre-established threshold.

[0009] EP 3658868 A1 discloses an apparatus for analysing the mechanical vibratory response of a solid material sample, comprising an array of impactors arranged to impact respective distinct points on the surface of said solid material sample, a sensor arranged to capture said mechanical vibratory response as a time-varying signal following the impact of at least one impactor, and processing means arranged to analyse said time-varying signal to determine frequencies and damping constants of sine waves constituting said time-varying signal. The invention also relates to a corresponding method of characterising a solid material sample.

[0010] WO2020254698 discloses a method for acoustically measuring material properties of a test specimen at high temperatures, comprising: a. heating the test specimen within a test temperature range; b. performing background measurements within the test temperature range by capturing a vibration signal from the test specimen within a calibration period to obtain a noise signal; c. applying a vibration excitation to the test specimen; c2. performing acoustic measurements on the test specimen within the test temperature range and within a test period by capturing a vibration signal of the test specimen within a test period to obtain a vibration response signal to the vibration excitation; and d. analyzing the vibration response signal to obtain material properties of the test specimen by taking into account the noise signal. The present invention also relates to a system for acoustically measuring material properties of a test specimen at high temperatures.

[0011] Both of the latter prior art documents in the name of the applicant relate to methods and apparatus for performing Impact Excitation (IE) measurements. The IE technique basically consists of impacting the workpiece and acquiring and analyzing a vibration response signal, also referred to as an acoustic response signal. The response signal can be captured via several methods, including using a microphone, a piezoelectric displacement sensor and / or a laser interferometer.

[0012] IE measurements can be used to non-destructively test workpieces to quantitatively assess the quality of the workpiece. This can be used for workpieces of all types of materials, such as metals, alloys, polymers, ceramics, or any combination thereof. IE measurements, and in particular the present invention, are believed to be particularly useful for characterizing 3D printed workpieces, also called additively manufactured workpieces. In such workpieces, the additive manufacturing (AM) process can result in heterogeneity with respect to the quality of the workpiece, i.e., some areas of the workpiece can be of lower quality than other areas.

[0013] The quality of workpieces, especially 3D printed workpieces, can be characterized by measuring the porosity of the workpiece. Typically, a higher porosity indicates more defects and may indicate a lower quality workpiece. Porosity can be measured using tomography, for example X-ray micro-computed tomography (CT). X-ray micro-CT has the advantage of reproducing a complete 3D model of the scanned object, allowing non-destructive testing of internal features or defects. However, X-ray micro-CT is an expensive and time-consuming measurement method. Furthermore, the inventors have found that X-ray micro-CT cannot resolve all kinds of quality-reducing structural features. For example, micro-CT does not have good sensitivity for detecting micro-cracks. The present invention therefore aims to provide a method by which a quality assessment of an AM workpiece can be obtained with respect to both porosity and micro-cracks in a single measurement, or at least in a single measurement setup.

[0014] The inventors have found that microcracks result in internal friction, which leads to increased damping of vibrations, particularly vibrations at or near the natural frequencies of the solid piece. As a result, a quantitative assessment of the presence of microcracks in a solid piece can be made by calculating one or more damping parameters for one or several natural frequencies. One possible way to calculate the damping parameters is to quantify the shape of the natural frequency peaks in the frequency spectrum of the vibration response.

[0015] However, when attempting to obtain damping parameters using impact excitation techniques, the inventors have found that the prior art techniques lack accuracy in measuring these damping parameters of multiple different solid pieces. More specifically, there may be room for improvement in comparing the results of damping parameters obtained for different solid pieces. The inventors have also found that the reproducibility of the extracted damping parameters is not always high.

[0016] The present invention aims to overcome the above and other problems. The present invention provides an improved method and system for performing IE measurements on solid pieces, preferably 3D printed solid pieces. The improved method and system make it possible to obtain very accurate results for the properties of the solid pieces that can be extracted from the vibration response, in particular the natural frequency and damping parameters. The properties obtained are better comparable across multiple different solid pieces.

[0017] Summary of the Invention The present invention relates to an impact excitation (IE) measurement system and method for measuring the vibration response of a solid piece to an impulse impact in an accurate and reproducible manner. The invention is set out in the claims, in particular in the independent claims. Preferred embodiments of the invention are set out in the dependent claims herein.

[0018] Accordingly, the present invention provides an Impact Excitation (IE) measurement system for measuring the vibration response of a solid piece to an impulse impact, comprising: an impactor for impacting solid pieces, preferably a mechanical impactor; a sensor for obtaining the vibration response of a solid piece to an impact; a support system for supporting the solid piece during impact to obtain a vibration response; The present invention relates to an impact excitation (IE) measurement system comprising:

[0019] The system further comprises a positioning table for accurately positioning the solid piece on the support system. The inventors have found that in order to obtain accurate results for the natural frequencies, and in particular the damping parameters of the natural frequencies, it is important that the solid piece is placed in an accurate position relative to the support system. This is important to enable comparison of results between:

[0020] - Measurements performed on several different solid pieces made using the same 3D printing process, which makes it possible to evaluate the accuracy, stability and repeatability of the 3D printing process, as well as the quality consistency of the printing machine and process when comparing the same part printed in the same build; - Different measurements on the same solid piece, for example at different times, which makes it possible to assess changes in the solid piece that may occur over time, for example due to wear and tear or due to further processing steps of the piece (for example heating procedures).

[0021] Accurate positioning of the solid piece is particularly useful when obtaining damping characteristics such as damping parameters, the measurement of which is particularly sensitive to external friction. In the present invention, by placing the solid piece in an optimal support position, the external friction can be minimized. Moreover, by repeatedly placing the solid piece in the same support position, any remaining external friction is essentially equal throughout the measurement. To that end, the positioning table is a piece holder configured to receive a solid piece at a predetermined holder position relative to the piece holder; an actuator operably connected to the piece holder, transferring the piece holder with the solid piece in said predetermined holder position onto a support system; placing the solid piece in a predetermined support position on the support system; Displacing the piece holder so that the solid piece is supported only by the support system while applying the impact to obtain the vibration response. an actuator configured to Equipped with.

[0022] The invention also relates to such a positioning table. The present invention also provides an impact excitation (IE) measurement method for measuring a vibration response of a solid piece to an impulse impact, comprising: a) placing a solid piece in a piece holder at a predetermined holder position relative to the piece holder; b) transferring the piece holder with the solid piece in the predetermined holder position to a support system; c) placing the solid piece at a predetermined support position on the support system; d) displacing the piece holder so that the solid piece is supported only by the support system; e) subjecting a solid piece supported only by the support system to an impact, preferably a mechanical impact; f) obtaining the vibration response of a solid piece to an impact; The present invention relates to an impact excitation (IE) measurement method, including:

[0023] Preferably, the IE measurement method comprises: g) further comprising analyzing the vibration response by extracting a set of natural frequencies and / or a set of damping parameters.

[0024] Additional embodiments of the present invention are further disclosed in the specification and claims.

[0025] Drawing Overview [Brief description of the drawings]

[0026] [Figure 1A] FIG. 2 shows a positioning table according to the present invention; [Figure 1B] FIG. 2 shows a positioning table according to the present invention; [Figure 2A] FIG. 13 is a side view showing the movement of the rotatable piece holder and the transfer of the solid piece to the support system. [Figure 2B] FIG. 13 is a side view showing the movement of the rotatable piece holder and the transfer of the solid piece to the support system. [Figure 2C] FIG. 13 is a side view showing the movement of the rotatable piece holder and the transfer of the solid piece to the support system. [Figure 3A] FIG. 2 is a top view of an exemplary support system in accordance with the present invention. [Figure 3B]1 is a perspective view of an exemplary support system according to the present invention. [Figure 4A] FIG. 2 is a diagram showing a measurement method according to the present invention. [Figure 4B] FIG. 2 is a diagram showing a measurement method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Detailed Description of the Invention The invention will now be further explained with reference to the drawings which serve to illustrate the invention, in which exemplary embodiments of the invention are shown.

[0028] 1A and 1B show a positioning table according to the invention. The table (10) comprises a piece holder with an essentially flat surface (11) and a set of positioning flanges (12, 13) that define a predetermined holder position for a solid piece (14). The piece holder is arranged to be rotatable about a pivot axis (15). The actuator is not shown in the figures, but can be a motor, such as a motor, preferably an electric motor, preferably a rotary motor, such as an electric rotary motor. The actuator is operatively connected to the piece holder and is configured to rotate the piece holder about the pivot axis, consistent with the invention. The piece holder also preferably includes a central hole (16) in the essentially flat surface, which allows the piece holder to be at least partially rotated on the support system, so that the solid piece (14) in the holder position can be gently positioned on the support system.

[0029] This is better illustrated by Figures 2A, 2B and 2C, which show the movement of the rotatable piece holder (10) and the transfer of the solid piece to the support system (20). This allows the solid piece (14) to be positioned on the piece holder at a predefined holder position (Figure 2B) at the start of the measurement. The flanges (12, 13) hold the solid piece in this holder position during the transfer. The piece holder is then rotated (counterclockwise in Figures 2A-2B). This causes the central hole of the piece holder to rotate over the top part (21) of the support system (20), so that the solid piece (14) is positioned on the support system, in particular on its top part (21) (see Figure 2C). Preferably, the top part comprises a flatbed support with an elasticity much greater than that of the solid piece in order to minimize external friction during the measurement.

[0030] The support system comprises a flat bed for supporting the solid specimen in the test chamber, said bed having an elasticity substantially greater than that of the specimen, said bed preferably further comprising a penetration to allow an impactor to impact the specimen from below or a sensor to obtain a vibration response from nearby. The term "elasticity" of a component refers to the manner in which the component stretches elastically under stress, whereby a first component is said to be more elastic than a second component if the first component has a greater relative strain under the same stress than the second component. Elasticity can thereby be expressed as the ratio (ε / σ) of the relative strain parameter (ε) divided by the stress parameter of elastic deformation (σ), preferably this ratio being Young's modulus (E). Preferably, the elasticity of the bed is at least 5 times, more preferably at least 10 times, even more preferably at least 50 times, still more preferably at least 100 times, even more preferably at least 200 times, even more preferably at least 500 times, even more preferably at least 1000 times, of the material of the specimen. The system and method of the present invention relates to a method for measuring the acoustic response to an impact and characterizing a test specimen by analyzing the acoustic response in terms of resonant frequency, shift of the resonant frequency, damping constant of the response at a particular frequency, etc. In the present invention, the presence of a flat bed having an elasticity greater than that of the test specimen is particularly useful for obtaining good measurements of the damping parameters of the test specimen. That is, the relatively high elasticity of the bed compared to that of the test specimen ensures that the test specimen can essentially vibrate freely, i.e., the vibration is essentially unaffected by the presence of the bed. In fact, the elasticity of the bed ensures that the bed can follow the vibratory motion of the test specimen.

[0031] The piece holder preferably includes or is made of a plastic material. Plastic allows for easy creation of a piece holder with a shape and / or flange that corresponds to the shape and size of the solid piece or pieces to be tested. Since these solid pieces tend not to vary in size or weight, a lightweight piece holder is possible, and therefore the piece holder preferably includes or is made of a plastic material such as polyethylene, polypropylene, or another polymeric material.

[0032] An exemplary support system according to the invention is shown in top view in Fig. 3A and in perspective view in Fig. 3B. The support system (20) thereby comprises a solid frame (23) and a top portion (21) with a set of flatbed supports (21A, 21B), preferably made from a resilient material such as foam. A sensor (22) is integrated into the solid frame of the support structure between the flatbed supports. In the shown view, the predetermined support location is above the flatbed supports (21A, 21B) and centered above the sensor (22).

[0033] In an embodiment, the sensor may comprise a contact sensor, such as a piezoelectric sensor, a non-contact sensor, such as a microphone or a laser vibrometer, or an accelerometer. When measuring damping parameters, a non-contact sensor is preferred. In a preferred embodiment, the acoustic sensor comprises a laser interferometer. Laser interferometers are particularly useful for measurements in a vacuum and allow for non-contact measurements. Alternatively or additionally, the acoustic sensor may comprise, for example, a laser interferometer. -SR. Huang, RMLerner, KJ Parker "Time domain Doppler estimators of the amplitude of vibrating targets", J. Acous. Soc. Am., 91(2), 965-974 (1992), -J. Tapson "High precision, short range ultrasonic sensing by means of resonance mode-locking", Ultrasonics, 33, 6, 441-444 (1995), and -R. Kazys, R. Sliteris, L. Mazeika "Ultrasonic technique for Vibration Measurements", Proceedings of the 15th World Conference on Non-Destructive Testing, 15-21 October 2000 in Rome, https: / / www.ndt.net / article / wcndt00 / papers / idn246 / idn246.htm The device may comprise an ultrasonic measurement sensor and / or a time-of-flight sensor and / or a Doppler type sensor, as described in.

[0034] The measurement method is shown in Figures 4A and 4B for a support structure as in Figures 3A and 3B and a positioning table as in Figures 1A-2C. The positioning table is then in the position shown in Figure 2C, whereby the central hole (16) of the positioning table is rotated over the upper part (21) of the support system such that the solid piece (14) is supported only by the upper part (21A, 21B). With the solid piece supported only by the upper part, the mechanical impactor (30) rotates in a first movement (31) over the solid piece (14) as shown in Figure 4A. The mechanical impactor (30) comprises a resilient arm (34) and a hammer tip (35) at the distal end of the arm. The mechanical impactor is preferably actuated by an impactor actuator (33), which preferably comprises an electric motor, preferably a programmable electric motor. Once the impactor is positioned above the solid piece, then in a second motion (32), an impulse impact is given to the solid piece by the up and down movement (32) of the arm (34) and the hammer tip (35), as shown in Figure 4B. Only the hammer tip impacts the solid piece. The vibration response is obtained by the sensor (22) and can be further analyzed by the processing means.

[0035] In one embodiment of the invention, the support system is fixedly installed, which includes: a) placing a solid piece in a piece holder at a predetermined holder position relative to the piece holder; b) transferring the piece holder with the solid piece in the predetermined holder position to a support system; c) placing the solid piece in a predetermined support position on the support system; d) displacing the piece holder so that the solid piece is supported only by the support system; e) subjecting a solid piece supported only by the support system to an impact, preferably a mechanical impact; f) It means that during the process of obtaining the vibration response of a solid piece to an impact, it does not move.

[0036] The fixed position of the support system increases the reproducibility of the measurements. In a preferred embodiment of the present invention, the positioning table (10) is provided with a temperature sensor for measuring the temperature of the test piece. Preferably, the temperature sensor is provided in the piece holder of the positioning table. This allows the temperature of the test piece to be measured by direct contact. Preferably, the temperature sensor includes a thermocouple.

[0037] Furthermore, this allows the measurement to be repeated at different temperatures, thereby obtaining the temperature dependence of the natural frequency and / or damping parameters. Such temperature dependence can reveal further information about the quality of the solid piece.

[0038] The support system thus comprises a bed of thermally stable elastic material, preferably in the form of a flat mat. The support bed preferably comprises an open structure. Preferably, the bed is composed of a non-woven material. In a preferred embodiment, the bed comprises or is made of a ceramic or glass-like material, such as mullite (SiO2), alumina (Al2O3) or a combination thereof, e.g. polycrystalline mullite and alumina wool, preferably in a non-woven structure. The bed may also comprise or be made of a polymeric material.

[0039] The term "thermally stable material" refers to a material that has a very small thermal expansion over a large temperature interval. Preferably, the material has a thermal expansion coefficient of at most 25.0×10 -6 K -1 , more preferably up to 15.0×10 -6 K -1 , and even more preferably up to 10.0×10 -6 K -1 , and even more preferably up to 8.0×10 -6 K -1 , and even more preferably up to 6.0×10 -6 K -1 , and even more preferably up to 5.0×10 -6 K -1 , and even more preferably up to 4.0×10 -6 K -1, most preferably up to 3.0×10 -6 K -1 Preferably, the material has such a low thermal expansion over the entire range of the temperature interval over which the measurements are carried out.

[0040] In one embodiment, the bed comprises a flat mat shape. Preferably, the bed comprises a height of 1 mm to 50 mm, more preferably 2 mm to 45 mm, even more preferably 3 mm to 40 mm, even more preferably 4 mm to 35 mm, even more preferably 5 mm to 30 mm, such as 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, or any value therebetween. The bed heights given herein are measured at 20°C.

[0041] It should be noted that by providing the positioning table, in particular the piece holder, with a temperature sensor, it is possible to measure the temperature of the test piece from the moment it is positioned on the positioning table at least until the moment the test piece is supported only by the support system, i.e. from step a) to step d) of the method according to the invention, and thus to measure the temperature at any moment or at any interval during steps a) to d). If the test piece is removed from its support position by the positioning table, it is also possible to measure the temperature after step f).

[0042] Thus, in a preferred embodiment of the present invention, the IE measurement method comprises measuring the temperature of the test specimen. The temperature of the test specimen can be measured at any time or at any interval during steps a) to d), preferably during and / or after step a), before, during and / or after any of steps b) and / or c), and / or before and / or during step d). Preferably, the temperature of the test specimen is monitored during the interval during which any or any combination of steps a), b), c) and / or d) are performed, preferably during which all steps a) to d) are performed.

[0043] The analysis preferably comprises: - obtaining a vibration response of a solid piece to an impact, preferably in the frequency domain; - extracting a set of natural frequencies, and optionally damping, from the vibration response, each of said natural frequencies corresponding to a vibration mode of said solid piece; for at least one vibration mode, obtaining a natural frequency shift by comparing one of a set of extracted natural frequencies corresponding to said vibration mode with a reference natural frequency value of said vibration mode, and preferably obtaining a porosity value of the solid piece from said natural frequency shift, thereby detecting a deviating AM process behavior; Includes.

[0044] Preferably, this also extracts a set of dampings from the vibration response, each of said dampings corresponding to a natural frequency of said set of natural frequencies. These dampings can be extracted for at least one natural frequency, preferably for each natural frequency. At least one damping parameter is thereby calculated for at least one natural frequency from the dampings corresponding to said natural frequencies, thereby obtaining a microcrack volume value of the solid piece that allows to detect deviant AM process behavior that is not detected by natural frequency shifts alone. Hereby, damping relates to how a particular natural frequency echoes after an impact is applied to the solid piece, in particular the time after the impact that said natural frequency can still be seen in the vibration response. Damping can be extracted from the time domain response of the vibration response and / or from the frequency domain response of the vibration response, preferably from the frequency domain response. A damping parameter, also referred to as damping coefficient, can be calculated from the damping. Typically, damping can be quantified by looking at the natural frequency peaks of the frequency spectrum of the vibration response. Preferably, the damping parameter relates to the width of the natural frequency peak in the vibration response, for example the width of the natural frequency peak at half maximum. Alternatively or additionally, the damping parameter may be related to the shape of the natural frequency peak in the vibration response, for example a skew damping parameter and / or a kurtosis parameter.

[0045] The inventors have found that the natural frequency shift thus obtained is directly related to the porosity of the solid piece, which in turn is related to the amount of voids, including medium and large radii. Furthermore, the inventors have found that the damping parameter of the natural frequency is closely related to the amount of microcracks in the solid piece, which in turn is related to the durability, i.e. the long-term strength, of the solid piece. It should be noted that the microcracks are essentially linear in structure and therefore do not contribute significantly to the porosity of the solid piece. However, the invention makes it possible to obtain information on both porosity and microcracks in a single measurement and / or a single measurement setup, and thus also to obtain a quantitative assessment of the quality of the solid piece based on the natural frequency shift and the damping parameter. This quantitative assessment also applies to the AM method used to create the solid piece. The quantitative assessment may preferably be performed by a scoring algorithm, which calculates a score depending on the value of one or more natural frequency shifts and one or more damping parameters, and optionally depending on a set of thresholds, preferably selected to ensure a minimum quality of the solid piece.

[0046] The analysis is preferably performed by a processing means, the processing means comprising: Calculating vibration response in the frequency domain; extracting a set of natural frequencies, and optionally damping, from a vibration response, each of said natural frequencies corresponding to a vibration mode of said solid piece; obtaining, for at least one vibration mode, a natural frequency shift by comparing one of a set of extracted natural frequencies corresponding to said vibration mode with a reference natural frequency value of said vibration mode, and preferably obtaining a porosity value of the solid piece from said natural frequency shift, thereby detecting a deviating AM process behavior; The present invention is configured to:

[0047] Preferably, the processing means is also calibrated to derive a set of dampings from the vibration response, each of said dampings corresponding to a natural frequency of said set of natural frequencies. These dampings may be extracted for at least one, preferably each, natural frequency. Thereby, the processing means is configured to calculate, for at least one natural frequency, at least one damping parameter from the dampings corresponding to said natural frequency, thereby obtaining a microcrack volume value for the solid piece.

Claims

1. 1. An Impact Excitation (IE) measurement system for measuring the vibration response of a solid piece to an impulse impact, comprising: - an impactor for impacting the solid piece; a sensor for obtaining the vibration response of said solid piece to said impact; a support system for supporting said solid piece during said impact to obtain said vibration response; a positioning table, a piece holder configured to receive the solid piece at a predetermined holder position relative to the piece holder; an actuator operatively connected to the piece holder, transferring the piece holder with the solid piece in the predetermined holder position to the support system; placing said solid piece in a predetermined support position on said support system; displacing the piece holder so that the solid piece is supported only by the support system during the application of the impact to obtain the vibration response; an actuator configured to A positioning table comprising: Equipped with The impact excitation (IE) measurement system includes an upper portion having a flat bed support with a resilience greater than the resilience of the solid piece.

2. The IE measurement system according to claim 1 , further comprising processing means configured for analysing the vibration response by extracting a set of natural frequencies and / or a set of damping parameters.

3. 3. The IE measurement system of claim 2, comprising processing means configured to analyze the vibration response by extracting a set of natural frequencies and a set of damping parameters.

4. The IE measurement system of any preceding claim, wherein the actuator is configured to move the piece holder so that the solid piece is positioned at the predetermined holder position after the vibration response is obtained, and to displace the piece holder so that the solid piece is removed from the support system.

5. IE measurement system according to any of the preceding claims, wherein the impactor is a mechanical impactor.

6. IE measurement system according to any of the preceding claims, wherein the piece holder comprises an essentially flat surface (11) and a set of positioning flanges (12, 13) defining the predetermined holder position of a solid piece (14).

7. IE measurement system according to any of the preceding claims, wherein the piece holder is rotatably arranged about a pivot axis (15), and the actuator is operatively connected to the piece holder and configured to rotate the piece holder about the pivot axis to the positioning table such that the solid piece is positioned at the predetermined support position on the support system.

8. 7. The IE measurement system of claim 6, wherein the piece holder comprises a central hole (16) in the essentially flat surface, the central hole enabling the piece holder to be at least partially rotated on the support system.

9. IE measurement system according to any of the preceding claims, wherein the actuator comprises a motor, such as an electric motor, preferably a rotary motor, such as an electric rotary motor.

10. IE measurement system according to any of the preceding claims, wherein the positioning table is provided with a temperature sensor for measuring a temperature of the test piece.

11. A positioning table for an Impact Excitation (IE) measurement system according to any of the preceding claims, comprising: a piece holder configured to receive a solid piece at a predetermined holder position relative to said piece holder; an actuator operatively connected to the piece holder, transferring the piece holder with the solid piece in the predetermined holder position to the support system; placing said solid piece at a predetermined support position on a support system of said IE measurement system; displacing the piece holder so that the solid piece is supported only by the support system during impact to obtain a vibration response; an actuator configured to A positioning table comprising: Equipped with The support system includes a positioning table having an upper portion with a flat bed support having a resilience greater than the resilience of the solid piece.

12. 1. An impact excitation (IE) measurement method for measuring a vibration response of a solid piece to an impulse impact, comprising: a) placing the solid piece in a piece holder at a predetermined holder position relative to the piece holder; b) transferring the piece holder with the solid piece in the predetermined holder position to the support system; c) placing said solid piece in a predetermined support position on a support system; d) displacing the piece holder such that the solid piece is supported only by the support system; e) applying an impact, preferably a mechanical impact, to said solid piece supported only by said support system; f) obtaining a vibration response of said solid piece to said impact; Including, The impact excitation (IE) measurement method, wherein the support system comprises an upper portion comprising a flat bed support having a resilience greater than the resilience of the solid piece.

13. The IE measurement method according to claim 12, comprising: g) analysing the vibration response by extracting a set of natural frequencies and / or a set of damping parameters.

14. The IE measurement method of claim 13, comprising: g) analyzing the vibration response by extracting a set of natural frequencies and a set of damping parameters.

15. The IE measurement method according to any one of claims 12 to 14, wherein the solid piece is a 3D printed solid piece.

16. The IE measurement method according to any one of claims 12 to 15, further comprising measuring the temperature of the test piece.

17. The IE measurement system according to any one of claims 1 to 10, configured to carry out the IE measurement method according to any one of claims 12 to 16.

18. A kit comprising a solid piece and an IE measurement system according to any one of claims 1 to 10, wherein the support system comprises a top portion comprising a flat bed support having an elasticity greater than the elasticity of the solid piece.

19. 20. The kit of claim 18, wherein the solid piece is a 3D printed solid piece.

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