Automatic system compliance estimation and correction for mechanical testing systems

An error compensation system and method may include applying a mechanical load to a reference sample to obtain a load measurement signal from the load sensor and a displacement measurement signal from the displacement sensor, calculating a transfer function to create a load filter and a displacement filter to be applied to the load measurement signal and the displacement measurement signal, respectively, applying the load filter to the load measurement signal to calculate a load compensation value, and applying the displacement filter to the displacement measurement signal to calculate a displacement compensation value, and determining the compensated value by comparing the load compensation value with the displacement compensation value, wherein the compensated value is determined prior to testing a specimen so that the compensated value is used to automatically correct a measured deflection of the specimen to arrive at an actual specimen deflection.

TECHNICAL FIELD

The present invention relates to a mechanical testing system and methods for error compensation, and more specifically to embodiments of an error compensation system for correcting errors attributable to parameters of a mechanical testing device.

BACKGROUND

Mechanical testing systems are used for calculating, testing, and measuring material properties and parameters of various specimens. As part of the tests, the mechanical testing system may apply various loads, including an axial load, a torsion load, a tensile load, a compression load, etc., to the specimen. However, the components of the mechanical testing device are also subjected to those applied loads, leading to sources of error when measuring the effects of the specimen.

SUMMARY

An aspect relates generally to a method for determining a compensated value attributable to a deflection of a mechanical testing system, the mechanical testing system including at least one fixture, a frame, a load sensor, and a displacement sensor, the method comprising: applying a mechanical load to a reference sample mechanically coupled to the at least one fixture to obtain a load measurement signal from the load sensor and a displacement measurement signal from the displacement sensor, calculating a transfer function converting the load measurement signal and the displacement measurement signal to a frequency domain to create a load filter and a displacement filter to be applied to the load measurement signal and the displacement measurement signal, respectively, applying the load filter to the load measurement signal to calculate a load compensation value, and applying the displacement filter to the displacement measurement signal to calculate a displacement compensation value, and determining the compensated value by comparing the load compensation value with the displacement compensation value, wherein the compensated value is determined prior to testing a specimen so that the compensated value is used to automatically correct a measured deflection of the specimen to arrive at an actual specimen deflection.

Further aspects relate to a method, a mechanical testing system, and a computer program product for determining a compensated value attributable to a deflection of the mechanical testing system, the method comprising: receiving, by the processor, a load measurement signal from the load sensor, and a displacement measurement signal from the displacement sensor, in response to an actuator of the mechanical testing system applying a mechanical load to a reference sample mechanically coupled to at least one fixture of the mechanical testing system, creating, by the processor, a load filter and a displacement filter to be applied to the load measurement signal and the displacement measurement signal, respectively, using a transfer function, calculating, by the processor, a load compensation value by applying the load filter to the load measurement signal, and a displacement compensation value by applying the displacement filter to the displacement measurement signal, and comparing, by the processor, the load compensation value with the displacement compensation value to determine the compensated value prior to testing a specimen so that the compensated value is used to automatically correct a measured deflection of the specimen to arrive at an actual specimen deflection.

DETAILED DESCRIPTION

When measuring one or more mechanical properties of a material, frequently a significant parameter of interest is a stiffness (e.g. storage modulus) of a specimen under test, as well as a portion of energy lost during a cycle (i.e. loss modulus), which can be used to calculate a ratio (tan(δ)) between the loss modulus and the storage modulus. Based on a specimen geometry, the storage modulus can be determined by measuring the specimen's stiffness. When measuring stiffness, it is typical that two measurements are made simultaneously, using a loading system: a load applied to the sample, and a deflection of the sample in response to that load. The ratio tan(δ) can be computed from a phase difference between the load measurement signal and the displacement measurement signal. One of the primary sources of error is due to stiffness or a compliance (i.e. 1/stiffness) of the mechanical testing device. As a given load is applied, both the specimen and the mechanical testing device experience that load, and undergo some deformation. As a result, the resulting displacement measurement includes both the specimen deformation and the testing system deformations. From the point of view of attempting to measure a stiffness of the specimen, the system deformations are a source of error.

Every component of a loading path within the test system contributes to the overall compliance of the testing system. Some of the typical components are a loading frame, or primary structure, of the system, a load measurement device, which is typically measures load as being proportional to its compliance, and fixtures that hold or support the specimen during a testing operation. Of these, the compliance or deformation of the testing system and the load measurement device (e.g. sensor) may not vary from one test to another. However, a given test system may be used to test many different types and geometries of specimens, and in various orientations. Accordingly, it is valuable to give a user a tool to quickly and accurately assess the overall compliance of the testing system before running a test on a desired material/specimen. An error correction or compensation for the compliance, deflection, and/or displacement of the testing system may be used by the test system computer to correct for these errors automatically, providing the user with more accurate data on the specimen.

Referring to the drawings,FIG. 1depicts a block diagram of error compensation system100, in accordance with embodiments of the present invention. Embodiments of the error compensation system100may be a system for correcting errors attributable to parameters of a mechanical testing device50. Embodiments of the error compensation system100may be useful for ensuring accurate measurements of physical properties of specimens by eliminating errors due to measurements attributable to the mechanical testing device50(i.e. components thereof). For example, a mechanical testing device50may be factory calibrated before arriving at a user location, but due to additional assembly and set-up at the end user location, the mechanical testing device50may need to be recalibrated to account for system compliance. In addition, various fixtures may be used for different types of testing, wherein each fixture may experience an applied load differently.

Embodiments of the error compensation system100may be an error compensation system, an error calculation and correction system, an error estimation and correction system, an automatic error correction system, a compliance detection and correction system, a stiffness testing system, a displacement testing system, a mechanical testing system for testing materials, and the like. Embodiments of the error compensation system100may include a computing system120and a mechanical testing device50. Embodiments of the computing system120may be a computer system, a computer, personal computer, a desktop computer, a cellular phone, a user mobile device, a user computing device, a tablet computer, a dedicated mobile device, a laptop computer, a dedicated processor or microcontroller hardware, other internet accessible device or hardware and the like capable of being coupled to a mechanical testing device50. Embodiments of the computing system120may include hardware functionality such as a speaker for emitting a sound, a display for displaying various plots, graphs, etc., with the ability to flash the display or portions of the content being displayed, a light emitting element for emitting a light, a receiver for receiving communications, a transmitter for transmitting signals, and other similar features and hardware of a computer associated with mechanical testing systems.

Embodiments of the error compensation system100may include a mechanical testing device50, coupled to the computing system120.FIG. 2depicts a perspective view of a mechanical testing device50, in accordance with embodiments of the present invention. Embodiments of mechanical testing device50may be a mechanical testing system a testing device, a sample tester, a properties analyzer for various specimens, a test instrument, a mechanical testing instrument, a device for testing samples, or any device for testing, measuring, and/or calculating a physical property, parameter, or characteristic of a physical specimen or section of material. In an exemplary embodiment, the mechanical testing device50may be used for calculating a stiffness of a particular sample. Moreover, embodiments of the mechanical testing device50may include a frame5, which may be a general support structure of the mechanical testing device50. The frame5may include an upper housing2and a lower housing3. An actuator may be positioned within the upper housing3apply mechanical load on a reference sample15(or specimen during a test operation of a material). Embodiments of the actuator may be an electromagnetic motor, pneumatic actuator, hydraulic actuator, a screw driven linear actuator, and the like. Loading modes may be axial or torsional. A first sensor10(as depicted schematically inFIG. 1) may also be positioned within the upper housing2. For instance, the first sensor10may be a displacement sensor that measures a displacement of the actuator during application of a load over a given period of time. Embodiments of the first sensor10may be communicatively coupled to the computing system120, as described in greater detail infra.

Further, embodiments of the mechanical testing device50may include a first fixture16and a second fixture14positioned between the upper housing2and the lower housing2. Embodiments of the first fixture16and the second fixture14may be a fixture, a holder, a grip, a sample or specimen retention element, a sample/specimen holder, and the like, for securing the ends of reference sample15disposed between the fixtures16,14. A distance between the fixtures16,14may be adjusted to secure the reference sample15between the fixtures16,15, by manipulating one or more clamps23to raise or lower a stage21of the mechanical testing device50. Embodiments of the mechanical testing device50may also include a second sensor20. Embodiments of the second sensor20may be a load sensor for measuring a force of an applied load by the actuator over a given period of time. Embodiments of the second sensor10may be communicatively coupled to the computing system120, as described in greater detail infra. In an exemplary embodiment, the second sensor20may be positioned below the second fixture, as shown inFIG. 2. However, embodiments of the second sensor20may be positioned above the first fixture16.

Referring back toFIG. 1, embodiments of the mechanical testing device50may be communicatively coupled to the computing system120. For instance, the mechanical testing device50may be coupled to a processor141of the computing system120. Sensors10,20of the mechanical testing device50may be communicatively coupled to the computing system120via an I/O interface150. The sensors10,20may be connected via an I/O interface150to computer system120. The number of sensors10,20connecting to computer system120via data bus lines155a,155b(referred to collectively as “data bus lines155) may vary from embodiment to embodiment, depending on the parameters of a specimen or testing system being tested. As shown inFIG. 1, a sensors10,20(e.g. a displacement sensor10and load sensor20) may transmit data or signals (e.g. “feedback data”) received from the sensors10,20by connecting to computing system120via the data bus lines155to an I/O interface150. An I/O interface150may refer to any communication process performed between the computer system120and the environment outside of the computer system120, for example, the sensors10,20and mechanical testing device50via data bus line155c. Input to the computing system120may refer to the signals or instructions sent to the computing system120, for example the data signals collected by the sensors10,20, while output may refer to the signals sent out from the computer system120to the mechanical testing device50, such as a signal to actuate the actuator/motor of the mechanical testing device50.

Furthermore, embodiments of the computing system120may be equipped with a memory device142which may store various data/information/code, and a processor141for implementing the tasks associated with the error compensation system100. In some embodiments, an error compensation application130may be loaded in the memory device142of the computing system120. The computing system120may further include an operating system, which can be a computer program for controlling an operation of the computing system120, wherein applications loaded onto the computing system120may run on top of the operating system to provide various functions. Furthermore, embodiments of computing system120may include the error compensation application130. Embodiments of the error compensation application130may be an interface, an application, a program, a module, or a combination of modules. In an exemplary embodiment, the error compensation application130may be a software application running on one or more back end servers, servicing a user personal computer over a network (not shown), and/or may be a software application running on the user personal computing device. In an exemplary embodiment, the error compensation application130may be used in conjunction with testing for stiffness of a particular material sample.

The error compensation application130of the computing system120may include a load module131, a filter module132, a calculating module133, and a comparing module134. A “module” may refer to a hardware-based module, software-based module or a module may be a combination of hardware and software. Embodiments of hardware-based modules may include self-contained components such as chipsets, specialized circuitry and one or more memory devices, while a software-based module may be part of a program code or linked to the program code containing specific programmed instructions, which may be loaded in the memory device of the computing system120. A module (whether hardware, software, or a combination thereof) may be designed to implement or execute one or more particular functions or routines.

Embodiments of the load module131may include one or more components of hardware and/or software program code for applying a load to the reference sample15for applying a mechanical load to a reference sample15mechanically coupled to the at least one fixture14,16to obtain a load measurement signal from the load sensor20and a displacement measurement signal from the displacement sensor10. For instance, embodiments of the load module131may receive a load measurement signal from a load sensor, such as sensor20, of the mechanical testing device, and a displacement measurement signal from a displacement sensor, such as sensor10, of the mechanical testing device50, in response to an actuator of the mechanical testing device50applying a mechanical load to a reference sample15mechanically coupled to at least one fixture14,16of the mechanical testing device50. Embodiments of the mechanical load may be a static load, a quasi-static load, a dynamic load with a single frequency, a dynamic load with multiple discrete frequencies, and a dynamic load with pseudo-random broadband noise.

In an exemplary embodiment for determining a compensated value attributable to a deflection of a mechanical testing system, prior to testing for stiffness of an actual specimen, embodiments of the load module131may send instructions to the actuator to apply a quasi-static load (e.g. force (N)) over a given period of time. For example, the load module131of the computing system120may via processor141generate a digital waveform which is ultimately converted to a current applied to the electromagnetic motor (e.g. actuator) of the mechanical testing device50apply a mechanical load to the reference sample15. In one embodiment, the applied load may be a plurality of sinusoidal excitations applied in succession or simultaneously, however, a single waveform may be generated for applying the load to the sample15. As a result of the generated waveform from the load module131, the actuator of the mechanical testing device50may exert a force (e.g. up to 50 N) over a period of time (e.g. 2-3 seconds). A load measurement signal may then be received from the load sensor20and a displacement measurement signal may then be received from the displacement sensor10.

FIG. 3Adepicts a graph of a load measurement signal220received from a load sensor20, in accordance with embodiments of the present invention. The load measurement signal220may be a time sample, showing that a force is applied starting at 0 N and increasing to approximately 45 N, holding at 45 N for about a half-second, and then decreasing the force back to 0 N.FIG. 3Bdepicts a graph of a displacement measurement signal210received from a displacement sensor10, in accordance with embodiments of the present invention. The displacement signal210may be a time sample, showing that a displacement of the mechanical testing device50starts at 0 mm and increases to about 0.012 mm as the load is increased, over time, and eventually back to 0 mm. The load measurement signal220and the displacement measurement signal210depicted inFIGS. 3A and 3Bare representative of a single, exemplary test for compliance or stiffness of the mechanical testing device50.

Furthermore, the resultant load measurement signal220and the displacement measurement signal210received by the load module131of the computing system120in response to the applied load exerted onto the reference sample15may represent load and displacement data of the mechanical testing device50(i.e. components thereof). In other words, the load measurement signal220and displacement measurement signal may be assumed to only represent load and displacement data resulting from a deflection of the testing device50, and not the reference sample15, because the reference sample15is significantly stiffer or more rigid than the testing system50. For instance, the reference sample15may be magnitudes more rigid than the components of the testing device50, such that either the reference sample undergoes no deflection or displacement at the loads being exerted by the actuator, or that any deflection or displacement of the reference sample15is negligible compared to the displacement or deflection of the testing device50. As an example, an overall stiffness of the testing device50may be 4000 N/m while the reference sample15may have a stiffness of 80000 N/m. In further embodiments, the sample15may have a known stiffness. Knowing the stiffness and the applied load, an expected deflection can be computed and compared to the actual measured deflection. The expectation being that the system deflection would be the difference between the expected deflection and the measured deflections.

Referring back toFIGS. 1 and 3A-3B, the computing system120may utilize the load measurement signal220and the displacement measurement signal210to calculate a stiffness of the testing device50.FIG. 4depicts a graph of measured system displacement (mm) and applied load (N), in accordance with embodiments of the present invention. Computing system120may analyze the data received by the load module131from the sensors10,20(e.g. load measurement signal and displacement signal) and using a data analysis technique, such as a least squares fit to calculate a slope230representing a stiffness or a compliance (1/stiffness) of the testing device50. In some embodiments of the error compensation system100, the computing system120may check to ensure a linearity of a slope230of the compliance/stiffness as part of a diagnostic check. If the slope is not linear, or a separation between a forward run231and a return run232exceeds a predetermined tolerance, the computing system120may send an error notification that the testing device50needs further calibration or will not produce accurate results.

Referring back toFIG. 1, embodiments of the computing system120may further include a filter module132. Embodiments of the filter module132may include one or more components of hardware and/or software program code for creating a load filter (e.g. filter240shown inFIG. 7) and a displacement filter (e.g. filter230shown inFIG. 7) to be applied to the load measurement signal220and the displacement measurement signal210, respectively, using a transfer function. For instance, embodiments of the filter module132of the computing system120may compute, calculate, derive, perform, etc. a transfer function converting the load measurement signal220and the displacement measurement signal210to a frequency domain to create a load filter240and a displacement filter230to be applied to the load measurement signal220and the displacement measurement signal210, respectively.FIG. 5depicts a graph representing the load filter240as a Bode diagram, in accordance with embodiments of the present invention. The Bode diagram inFIG. 5Adepicts a constant magnitude (dB) a constant phase (deg.), which means that the load filter240may be a gain only correction to be applied to the load measurement signal220. In an exemplary embodiment, the load filter240applied to the load measurement signal220may have a gain equal to the slope of the displacement v. applied load depicted inFIG. 4. In other words, the load filter240may be the compliance of the system (mm/N), which may be applied to the load measurement signal220(e.g. load (N)×compliance (mm/N)) to arrive at a load compensation value260shown inFIG. 7. In further embodiments, a filter with inverse characteristics relative to some measured error as a function of frequency may be created and applied to the load measurement signal220.FIG. 5Bdepicts a graph representing a higher order load filter as a Bode diagram, in accordance with embodiments of the present invention.FIG. 6depicts a graph representing the displacement filter230as a Bode diagram, in accordance with embodiments of the present invention. The Bode diagram inFIG. 6Adepicts a constant magnitude (dB), but a phase (deg.) value that changes as the frequency (Hz) increases, which means that the displacement filter230may be a displacement phase delay to synchronize the displacement measurement signal210and the load measurement signal220, which may be applied to the displacement measurement signal210. In further embodiments, a filter with inverse characteristics relative to some measured error as a function of frequency may be created and applied to the displacement measurement signal210.FIG. 6Bdepicts a graph representing a higher order displacement filter as a Bode diagram, in accordance with embodiments of the present invention. The two filters depicted inFIGS. 5B and 6Bcan be designed such that a standard filter (e.g. one of the filters shown inFIGS. 5A and 6A) can be implemented on one channel, and the alternate filter (e.g. one of the filters shown inFIGS. 5B and 6B) on the other channel, but not both alternates together. For example, the load filter240shown inFIG. 5Amay be used with the displacement filter230, or vice versa. However, alternate designs for the filters shown inFIGS. 5B and 6Bcould be produced where higher order filters are used for both the displacement filter230and the load filter240.

Embodiments of the filter module132may create a filter configured to compensate for variations in the system response as a function of frequency. For example, a system resonance causing errors in the measurement of sample stiffness as well as a variation in a phasing of the load measurement signal and the displacement measurement signal could be detected in a testing frequency range and the filters may be designed to compensate for that resonance. The information required to design these filters could be gathered by running a plurality of frequencies, such as a dynamic load with multiple discrete frequencies, or a dynamic load with pseudo-random broadband noise. In addition, any other irregularities in the load or displacement measurement signals as a function of frequency may be compensated for. In one embodiment, a phase delay in the load and/or displacement measurement signal path may be assessed and compensated such that the load measurement signal and the displacement measurement signal match in phase or have some desired phase ratio or phase relationship.

Referring again toFIG. 1, embodiments of the computing system120may also include a calculating module133. Embodiments of the calculating module133may include one or more components of hardware and/or software program code for calculating a load compensation value260by applying the load filter240to the load measurement signal220, and a displacement compensation value250by applying the displacement filter230to the displacement measurement signal210. For instance, embodiments of the calculating module133may apply the load filter240to the load measurement signal220to calculate a load compensation value260, and the displacement filter230to the displacement measurement signal210to calculate a displacement compensation value250.FIG. 7depicts a block diagram for error compensation to determine a compensated value275attributable to the mechanical testing device50, in accordance with embodiments of the present invention. Embodiments of the calculating module133may apply the load filter240to the load measurement signal220to calculate the load compensation value260. In particular, the calculating module133may multiply the load measurement signal220in N with the slope230value defining the compliance of the mechanical testing device50in mm/N, which is the gain of the load filter240. The resulting value in mm may be the load compensation value260, to be used by the comparing module134of the computing system120to determine an overall compensated value275(e.g. deflection (mm)) of the mechanical testing system50.

Moreover, the calculating module133may apply the displacement filter230to the displacement measurement signal210to calculate the load compensation value250. In particular, the calculating module133may synchronize the displacement measurement signal and the load measurement signal (i.e. slow down the displacement measurement signal210) by using the displacement filter230with a phase delay, because the displacement sensor10outputs over time are faster than the outputs over time from the load sensor20. The resulting value in mm may be the displacement compensation value260, to be used by the comparing module134of the computing system120to determine an overall compensated value275(e.g. deflection (mm)) of the mechanical testing system50. In an exemplary embodiment, either load filter240or displacement filter230may have a gain and/or a phase value which are a function of frequency, such that the filters230,240can correct for irregularities in the system.

Referring back toFIG. 1, and continued reference toFIG. 7, embodiments of the computing system120may include a comparing module134. Embodiments of the comparing module134may include one or more components of hardware and/or software program code for comparing the load compensation value260with the displacement compensation value250to determine the compensated value275prior to testing a specimen (not shown) so that the compensated value275is used to automatically correct a measured deflection of the specimen to arrive at an actual specimen deflection. For instance, embodiments of the comparing module134may determine the compensated value275by comparing the load compensation value260with the displacement compensation value250. Embodiments of the comparing module134of the computing system120may assign a negative value (e.g. −mm) to the load compensation value260, and may assign a positive value (e.g. +mm) to the displacement compensation value250. In an exemplary embodiment, the comparing module134may compare the compensated values250,260by subtracting the displacement compensation value250in mm from the load compensation value260in mm to arrive at a final compensated value275. Embodiments of the compensated value275may represent a total system (not reference sample15) deflection in mm, that may be used for automatic correction to eliminate errors attributable to the system, in future test operations of a target specimen.

Specifically, the compensated value275may be determined prior to testing a specimen so that the compensated value275is used to automatically correct a measured deflection of the specimen to arrive at an actual specimen deflection.FIG. 8graphically illustrates the compensated value275that can be applied to correct a measured deflection of a specimen, in accordance with embodiments of the present invention. For example,FIG. 8depicts a waveform of displacement over time, depicting a measured deflection and an actual specimen deflection, in a test operation using a real specimen and not reference sample15. As can be seen, the measured deflection is greater than the actual deflection of the specimen because deflection of the test system50adds to the overall measured deflection. However, by automatically applying the compensated value275to correct, modify, adjust, etc. the measured deflection, a testing system computing system, such as computing system120, may determine an actual deflection of only the specimen, which leads to more accurate results from the test. Embodiments of the computing system120may automatically correct the measured deflection of the specimen, in response to performing methods described above. Likewise,FIG. 9graphically illustrates the compensated value275that can be applied to correct a measured stiffness of a specimen, in accordance with embodiments of the present invention. As can be seen, the measured stiffness is less than the actual stiffness of the specimen because deflection of the test system50adds to the overall measured stiffness. However, by automatically applying the compensated value275to correct, modify, adjust, etc. the measured stiffness, a testing system computing system, such as computing system120, may determine an actual stiffness of only the specimen, which leads to more accurate results from the test. Embodiments of the computing system120may automatically correct the measured stiffness of the specimen, in response to performing methods described above.

Various tasks and specific functions of the modules of the computing system120may be performed by additional modules, or may be combined into other module(s) to reduce the number of modules. Further, embodiments of the computer or computer system120may comprise specialized, non-generic hardware and circuitry (i.e., specialized discrete non-generic analog, digital, and logic-based circuitry) (independently or in combination) particularized for executing only methods of the present invention. The specialized discrete non-generic analog, digital, and logic-based circuitry may include proprietary specially designed components (e.g., a specialized integrated circuit, such as for example an Application Specific Integrated Circuit (ASIC), designed for only implementing methods of the present invention). Moreover, embodiments of the error compensation system100may improve mechanical testing technology by eliminating error attributed to the testing device, which can vary from test-to-test. For example, a user may replace fixtures depending on the material to be tested. The new fixtures may not have been calibrated with the system and thus may contribute to an overall displacement and/or deflection, which can skew the results of the test. Thus, the error compensation system100may be individualized to mechanical testing device and to each fixture used in mechanical testing procedures, by allowing a user to perform a relatively quick error estimation and correction operation, to determine an error attributable to the system, in particular a new fixture, prior to using the mechanical test device to test an actual specimen. Furthermore, the error compensation system100may improve the computing system120based on a set of rules that are applied to determine an error value regardless of the changes to the testing system. As shown inFIGS. 3A-9, rules are used to calculate and interpret various data received from physical sensor and hardware devices, testing a physical, real-world sample.

Referring now toFIG. 10, which depicts a flow chart of a method400for determining a compensated value attributable to a deflection of a mechanical testing system, in accordance with embodiments of the present invention. One embodiment of a method400or algorithm that may be implemented for determining a compensated value attributable to a deflection of a mechanical testing system with the error compensation system100described inFIGS. 1-9using one or more computer systems as defined generically inFIG. 12below, and more specifically by the specific embodiments ofFIG. 1.

Embodiments of the method400for determining a compensated value attributable to a deflection of a mechanical testing system, in accordance with embodiments of the present invention, may begin at step401wherein a load is applied to a reference sample15. For instance, an actuator of a mechanical testing device50may apply a mechanical load, such as a compression force, to the reference sample15. Step402obtains a load measurement signal220using a load sensor20of the mechanical testing device50, and a displacement measurement signal210using a displacement sensor10. The data/signal may be transmitted to the computing system120from the sensors10,20. Step403calculates a transfer function to create digital filters to be applied to the load measurement signal220and the displacement measurement signal210. Step404applies the filters to the load measurement signal220and the displacement signal210. Based on the application of the filters, step405calculates a load compensation value260and a displacement compensation value250. Step406determines a compensated value275using the load compensation value260and the displacement compensation value250. The compensated value275may be determined prior to an end user using a mechanical testing system to perform tests on a specimen, so that the computing system120associated therewith can perform the automatic error corrections to a measured parameter to arrive at an actual parameter.

Embodiments of the error compensation system100may also determine dynamic properties of a testing system, such as mechanical testing device50, either alone or in combination with determining static or quasi-static properties of the mechanical device50, prior to a user running a test on an actual specimen. For example, mechanical losses (e.g., damping or inertial effects, backlash) can be assessed and corrected for following similar methods described above. Embodiments of the error compensation system100may analyze the applied loading/response data, as well as how the test system experiences the dynamic load(s) to be able to assess the quality of the supplied data and provide error reporting functionalities.

In a further embodiment, for a compression test where the fixture which applies load to the reference sample15may not start in contact, there may be initial ringing detected in the signal which could affect the measurement/analysis results. In this case, the computing system120may be designed to ignore data until the ringing effects are damped to a lower level, and the fixture can be assessed only when the fixture is in good contact with the reference sample15.

Additionally, after the analysis is complete, some measure of the quality of the may be made. For example, where a simple linear fit is used, two parameters are monitored: the R2value of the fit itself, and the variation in total between the linear fit and a higher order fit. An assumption may be made that if the higher order fit is significantly more accurate (i.e. has lower error), then the linear fit may not sufficiently model the behavior. While it would be possible to use the higher order fit, at this time, it is assumed that a linear relationship between load and displacement is expected. If a significantly non-linear relationship exists, then the operator should verify the system and fixtures. In this case, the computing system120may indicate an issue to the user.

Accordingly, values specific to a user's exact test set-up can be calculated or ascertained quickly, usually within less than a couple of minutes, including the physical set up of the fixtures and reference sample. In addition, embodiments of the error correction system100gives the user a tool to quickly assess the quality of the user's test set-up and warn or potential issues (e.g., loose fasters or fixtures could easily be detected) before running lengthy tests.

FIG. 11depicts a block diagram of a computer system for the error compensation system100ofFIGS. 1-9, capable of implementing methods for determining a compensated value attributable to a deflection of a mechanical testing system ofFIG. 10, in accordance with embodiments of the present invention. The computer system500may generally comprise a processor591, an input device592coupled to the processor591, an output device593coupled to the processor591, and memory devices594and595each coupled to the processor591. The input device592, output device593and memory devices594,595may each be coupled to the processor591via a bus. Processor591may perform computations and control the functions of computer system500, including executing instructions included in the computer code597for the tools and programs capable of implementing a method for determining a compensated value attributable to a deflection of a mechanical testing system in the manner prescribed by the embodiments ofFIG. 10using the error compensation system100ofFIGS. 1-9, wherein the instructions of the computer code597may be executed by processor591via memory device595. The computer code597may include software or program instructions that may implement one or more algorithms for implementing the method for determining a compensated value attributable to a deflection of a mechanical testing system, as described in detail above. The processor591executes the computer code597. Processor591may include a single processing unit, or may be distributed across one or more processing units in one or more locations (e.g., on a client and server).

The memory device594may include input data596. The input data596includes any inputs required by the computer code597. The output device593displays output from the computer code597. Either or both memory devices594and595may be used as a computer usable storage medium (or program storage device) having a computer-readable program embodied therein and/or having other data stored therein, wherein the computer-readable program comprises the computer code597. Generally, a computer program product (or, alternatively, an article of manufacture) of the computer system500may comprise said computer usable storage medium (or said program storage device).

Memory devices594,595include any known computer-readable storage medium, including those described in detail below. In one embodiment, cache memory elements of memory devices594,595may provide temporary storage of at least some program code (e.g., computer code597) in order to reduce the number of times code must be retrieved from bulk storage while instructions of the computer code597are executed. Moreover, similar to processor591, memory devices594,595may reside at a single physical location, including one or more types of data storage, or be distributed across a plurality of physical systems in various forms. Further, memory devices594,595can include data distributed across, for example, a local area network (LAN) or a wide area network (WAN). Further, memory devices594,595may include an operating system (not shown) and may include other systems not shown inFIG. 11.

In some embodiments, the computer system500may further be coupled to an Input/output (I/O) interface and a computer data storage unit. An I/O interface may include any system for exchanging information to or from an input device592or output device593. The input device592may be, inter alia, a keyboard, a mouse, etc. The output device593may be, inter alia, a printer, a plotter, a display device (such as a computer screen), a magnetic tape, a removable hard disk, a floppy disk, etc. The memory devices594and595may be, inter alia, a hard disk, a floppy disk, a magnetic tape, an optical storage such as a compact disc (CD) or a digital video disc (DVD), a dynamic random access memory (DRAM), a read-only memory (ROM), etc. The bus may provide a communication link between each of the components in computer500, and may include any type of transmission link, including electrical, optical, wireless, etc.

An I/O interface may allow computer system500to store information (e.g., data or program instructions such as program code597) on and retrieve the information from computer data storage unit (not shown). Computer data storage unit includes a known computer-readable storage medium, which is described below. In one embodiment, computer data storage unit may be a non-volatile data storage device, such as a magnetic disk drive (i.e., hard disk drive) or an optical disc drive (e.g., a CD-ROM drive which receives a CD-ROM disk). In other embodiments, the data storage unit may include a knowledge base or data repository125as shown inFIG. 1.

As will be appreciated by one skilled in the art, in a first embodiment, the present invention may be a method; in a second embodiment, the present invention may be a system; and in a third embodiment, the present invention may be a computer program product. Any of the components of the embodiments of the present invention can be deployed, managed, serviced, etc. by a service provider that offers to deploy or integrate computing infrastructure with respect to error compensation systems and methods. Thus, an embodiment of the present invention discloses a process for supporting computer infrastructure, where the process includes providing at least one support service for at least one of integrating, hosting, maintaining and deploying computer-readable code (e.g., program code597) in a computer system (e.g., computer system500) including one or more processor(s)591, wherein the processor(s) carry out instructions contained in the computer code597causing the computer system to determine a compensated value attributable to a deflection of a mechanical testing system. Another embodiment discloses a process for supporting computer infrastructure, where the process includes integrating computer-readable program code into a computer system500including a processor.

The step of integrating includes storing the program code in a computer-readable storage device of the computer system500through use of the processor. The program code, upon being executed by the processor, implements a method for determining a compensated value attributable to a deflection of a mechanical testing system. Thus, the present invention discloses a process for supporting, deploying and/or integrating computer infrastructure, integrating, hosting, maintaining, and deploying computer-readable code into the computer system500, wherein the code in combination with the computer system500is capable of performing a method for determining a compensated value attributable to a deflection of a mechanical testing system.

A computer program product of the present invention comprises one or more computer-readable hardware storage devices having computer-readable program code stored therein, said program code containing instructions executable by one or more processors of a computer system to implement the methods of the present invention.