Testing device for mechanically testing a bar-like test object

Abstract

The invention relates to a testing device for mechanically testing a bar-like test object (1), in particular a rotor blade, comprising a clamping device (2) anchored in a clamping field (3) for clamping the bar-like test object at a clamping point (1') of the bar-like test object, one or more coupling elements (4A, 4F), in particular a load frame, connected to the bar-like test object, one or more active load-introducing means (5A, 5B) each connected to a coupling element, and one or more passive load-introducing means each connected to a coupling element, of which passive load-introducing means at least one has a spring apparatus which is connected to the clamping field and is configured to exert a force on the test object in a spring loading direction, characterised in that the spring apparatus has at least one spring module (14) with at least one releasable holder apparatus (15A, 15B, 15B', 15B'', 15C, 15F, 15L) for releasably holding a selectable number of one or more spring elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J), in particular of the same type, which are mechanically connected to one another in parallel. By using a spring module, the testing device can be flexibly adapted to the specific testing situation.

Description

[0001] Test device for the mechanical testing of a beam-shaped test specimen

[0002] The invention relates to a testing device for testing beam-shaped test specimens, for example, rotor blades. Beam-shaped components, such as towers or rotor blades of wind turbines, are subjected to heavy loads and significant wear during operation. Rotor blades, which are often over 30 m long and sometimes much longer, should therefore be tested under extreme conditions and across a multitude of alternating loads for safety reasons.

[0003] Fatigue tests are essential for determining the performance of rotor blades, or more generally, beam-shaped test specimens subjected to high loads during operation. These tests aim to simulate as realistic a load as possible for a test specimen, such as a rotor blade, using test rigs / devices. This involves loads that typically occur during operation of a rotor blade in a wind turbine. Due to the aforementioned dimensions of rotor blades, testing is associated with considerable technical, time, and financial resources.

[0004] One way to simulate realistic load conditions in testing procedures for wind turbines is to test subcomponents, such as towers, rotor blades, or sections of such components. Several of these subcomponents are measured separately in test rigs. This allows conclusions to be drawn about the performance of the entire wind turbine. Dynamic structural testing in the resonance range of elongated and slender test specimens, such as entire rotor blades or rotor blade segments of wind turbines, presents a challenge with increasing lengths. The longer a test specimen is, the lower its natural frequency, and the longer the test duration for a given number of alternating loads.With the testing duration, which can range from days to weeks for a single stress test, not only do costs increase, but the waiting time until the approval of new models also becomes longer.

[0005] The challenge of long testing times due to low natural frequencies of a component can be countered, for example, by attaching elastic elements to suitable locations on the test specimen, thereby increasing the system natural frequency for uniaxial or biaxial excitation in bending load directions of the system consisting of the test specimen and the elastic element.

[0006] Such a solution typically incurs high costs, as an individual elastic element with a specific stiffness and deflection must be designed and manufactured for each test campaign, for example for a rotor blade type.

[0007] As technology advances, rotor blade types are becoming increasingly longer, requiring elastic elements with greater stiffness and increasing deflection for load testing. One problem is that the deflection of an increasingly longer test specimen, for example at the tip, becomes so large that conventional devices using an elastic element result in large displacements / deflections, such as those of a spring, and thus large spring lengths (approx. 20 m) and large oscillating masses, such as a lever arm structure, which counteract the spring effect. To enable such large deflections while maintaining high stiffness, the elastic elements become very large, heavy, and expensive.

[0008] German patent application DE102018218515A1 discloses a test device for rotor blades of wind turbines, in which both active load introduction means for periodic deformation of a blade and passive load introduction means in the form of springs for shaping system natural frequencies and bending load distributions are provided.

[0009] The present invention is based on the objective of creating a testing device for the mechanical testing of beam-shaped test specimens that enables the most flexible use possible with short testing times and low effort.

[0010] The problem is solved by a testing device with the features of the invention according to claim 1. The dependent claims present possible implementations of such a testing device.

[0011] Accordingly, the invention relates to a test device for the mechanical testing of a beam-shaped test specimen, in particular a rotor blade, comprising a clamping device anchored in a clamping field for clamping the beam-shaped test specimen at a clamping point of the beam-shaped test specimen, one or more coupling elements connected to the beam-shaped test specimen, in particular load frames, one or more active load application means each connected to a coupling element, and one or more passive load application means each connected to a coupling element, at least one of which has a spring device connected to the clamping field, which is configured to exert a force on the test specimen in a spring loading direction, wherein the spring device has at least one spring module with at least one releasable mounting device for releasably holding a selectable number of one or more mechanically parallel connected,especially similar spring elements.

[0012] It may also be provided, for example, that one or more clamping devices are connected on the one hand to the clamping field and on the other hand to one or more spring elements, and that in particular at least one clamping device is connected on the one hand to one or more spring elements and on the other hand to the test specimen.

[0013] To perform a test, the beam-shaped specimen is clamped at the clamping point and mechanically deflected at one or more points in one or more directions, for example, periodically over time, by means of active load application devices. These active load application devices can include hydraulic or pneumatic pistons or electric linear or rotary drives that generate a deflection which is transmitted directly or via gears, such as lever drives, to the specimen. This allows for extensive control of the deflection path, deflection rate, force, and frequency. In addition, at least one passive load application device with a spring element is provided, which can act on the specimen at a suitable point to achieve a desired distribution of the bending load and to adjust the system's natural frequency as desired.The coupling elements for connecting the load application means to the test specimen can be implemented as load frames, but also in any other conceivable way, for example in the form of pads or other fastening devices that can be attached to the test specimen by adhesive or other means and to which rods, levers, or ropes can be connected by means of eyelets or other fastening devices. Because the spring assembly is designed as a spring module with one or more spring elements and a flexibly designed mounting device, the number of spring elements connected in parallel and their individual design can be flexibly selected, so that the overall properties of the spring module can be flexibly designed and easily modified even during the test.For example, individual spring elements can have the same or different stiffnesses, allowing the overall stiffness of the spring assembly to be adjusted. This eliminates the need to build a separate and customized spring assembly for each test specimen, and elements of the spring assembly can be reused by assembling and using the spring elements held or attached in the mounting device(s) as needed. Furthermore, the spring assembly can be adapted during testing to the specific test conditions and the characteristics of the test specimen. Currently, spring elements are often provided based on theoretical model calculations, which then do not correspond to the actual test specimen with sufficient accuracy. In such cases, the spring module can be reassembled, or a spring element can be removed or added.A spring module can, in principle, combine various spring types, although in many cases combining similar spring elements is advantageous. For example, several disc or coil springs can be connected in parallel within a spring module, as can several leaf springs. The example of leaf springs will be discussed in more detail below.

[0014] In a specific embodiment of the test device, it may be provided, for example, that at least one spring module comprises spring elements in the form of one or more beam elements arranged parallel to one another, in particular in the form of leaf springs, wherein the beam elements may be arranged side by side, in particular in a direction transverse or perpendicular to the direction of spring loading. The direction of spring loading is the direction in which the spring elements are deflected under the influence of force. In the case of leaf springs, the direction of spring loading is usually perpendicular to the longitudinal axis of the leaf springs and perpendicular to the widest side surface.

[0015] Such flexible beam elements, which can be, for example, leaf springs, but also flexible tubes or sandwich bodies or hollow bodies composed of several different materials, can be easily combined by arranging them side by side, or in some cases alternatively or additionally, one above the other. With suitable design, they allow for large spring deflections and offer considerable design flexibility with regard to the achievable stiffness. Fittings, such as clamping devices, can be provided at the fixing points to transmit the force; these will be explained in more detail below.

[0016] Furthermore, it may be provided that at least one spring module is connected to the clamping field at at least one of its ends by means of a joint or a hinge joint.

[0017] To exert a spring force on the test specimen, a spring assembly is typically connected to the clamping frame, which also houses the clamping device for the specimen. The clamping frame includes foundations and rigidly connected fixtures for supporting elements of the test fixture and for transmitting the force. A spring module can be rigidly connected to the clamping frame. However, to accommodate potential deformations of the spring module under load and to achieve the simplest possible spring characteristics, certain degrees of freedom can often be allowed at the spring module's mounting points. A hinged connection between the spring module and the clamping frame can serve this purpose.

[0018] Another possible implementation involves connecting at least one spring module at one end to a joint or hinge joint connected to the clamping frame by means of a shackle. Such a connection of a spring module to a joint allows not only for bending the spring module, but also for shortening or lengthening the spring, or more precisely, for changing the distance between the two ends of the spring module. The shackle can be designed as a rod that is pivotably attached to both the joint connected to the clamping frame and the spring module by means of eyelets.

[0019] Furthermore, it may be provided that at least one spring module has one or more retaining devices in the form of releasable clamping devices, in which one or more beam elements or leaf springs can be clamped. A clamping device allows identical beam-shaped spring elements, arranged side by side or one above the other, to be easily clamped together. The clamping device then serves to mechanically connect a point of the spring module to another element of the test device, for example, a rod, a lever, or a rope, or to the clamping frame. Tensile or compressive forces can thus be introduced into or out of a spring module via the clamping device and transferred to the test specimen.

[0020] The mounting devices can also be designed as a crossbeam running perpendicular to the longitudinal axis of the spring elements and featuring screw elements, such as threaded holes, to which fixing elements of the individual spring elements, such as screws, can be screwed. The spring elements can, for example, have through holes through which screws are inserted and tightened in threaded holes of the mounting device. Similarly, a mounting device can have through holes for fastening screws of the individual spring elements.

[0021] It may also be provided that at least one clamping device is movable along a spring module and is designed to clamp the beam elements or leaf springs of the spring module selectively at one of several positions.

[0022] Because one or more clamping devices are movable along a spring module, the spring forces and spring travel can be adjusted quickly and easily. For this purpose, the clamping devices can first be released, then moved, and finally clamped again at a different point on the spring module. During the load test itself, the clamping devices are not movable.

[0023] If crossbeams with screw elements or through holes are provided as mounting devices, a plurality of such elements can be provided along the individual spring elements for selection.

[0024] Another possible implementation involves connecting at least one clamping device to the clamping field by means of a joint or a hinge joint and / or connecting at least one clamping device to a joint or hinge joint connected to the clamping field by means of a shackle.

[0025] It may also be provided that at least one clamping device is connected to the test specimen by means of a transmission element, in particular by means of a lever.

[0026] Various flexibly interchangeable intermediate and additional elements, for example in the form of flexibly stackable sheet metal packages, can be provided to adapt the desired length and lever ratios as well as the storage location of the lever and also to align and position the elements of the test device in a suitable way in all spatial directions relative to the test specimen.

[0027] Another possible implementation involves connecting at least one spring module to the clamping array at only one or at least two points along the longitudinal direction of the beam elements or leaf springs. Alternatively, a clamping device connected to the test specimen, in the form of a clamping device, may be positioned between two clamping devices connected to the clamping array, viewed in the longitudinal direction of the beam elements of a spring module. Another possibility is that a spring module is clamped to the clamping array on only one side, with a clamping device connected to the test specimen clamping the spring module at one point along the longitudinal direction of the beam elements of the spring module.

[0028] If the spring module is connected to the clamping field at only one point, then, in the case of a module with beam-shaped spring elements, it is rigidly and angularly stiffly connected to the clamping field at one clamping point. In this case, a point of the spring module spaced away from the clamping point is connected to the test specimen, for example, by means of a clamping device.

[0029] This variant allows for long spring travels with relatively low spring forces. If the spring module is connected to the clamping field at least at two points along the longitudinal direction of the beam elements or leaf springs, it can be connected to the test specimen at a third point between these two points, for example, by means of a clamping device and a lever. In this case, the achievable spring travel is less than with only a single-sided attachment of the spring module, but the achievable spring forces are greater. Another possible implementation involves connecting the spring module to the rotor blade or to a lever assembly connected to the rotor blade at only one or at least two points along the longitudinal direction of the beam elements or leaf springs.

[0030] By coupling the spring module to the test specimen in this way, for example by means of a crossbeam, a 4-point bending load on the spring module is achieved. This type of coupling allows the generation of very large spring forces.

[0031] Another possible implementation involves arranging several beam elements parallel to each other in a spring module, and ensuring that at several points or at all points along the longitudinal direction of the beam elements, several or all beam elements have the same thickness in the direction of the mechanical load for which the spring module is intended, such that they can be clamped together by a clamping device.

[0032] The beam elements can have different widths, for example, while having the same thickness, in order to achieve the desired stiffness.

[0033] Therefore, it can also be provided that several beam elements of different stiffness, in particular several leaf spring elements of different widths, are arranged parallel to each other in a spring module.

[0034] In general, it can be provided that one or more clamping devices are provided on a spring module, each having two clamping beams that can be connected or are connected by connecting elements, between which the flexible beam elements, in particular in the form of leaf springs, can be clamped.

[0035] The clamping beams can be straight or curved, and the connecting elements can be screws or threaded studs in conjunction with threads in the clamping device or with nuts. The clamping beams can also have an elastic compensating layer on their side facing the spring elements, which compensates for any slight differences in the thickness of different spring elements during clamping and also prevents loosening of the clamp during the test procedure.

[0036] The individual spring elements can have a constant or varying cross-section or cross-sectional shape along the length of the spring module. This also influences the stiffness of the individual spring elements and thus the stiffness of the spring module.

[0037] In a clamping device, several spring elements can be arranged parallel to each other with a free distance between them. This achieves greater stiffness of the spring module in a direction perpendicular to the intended load direction compared to an arrangement with spring elements directly next to each other without any gap. The individual spring elements can be designed as solid bodies or as hollow bodies. When designed as hollow bodies, the moving mass is significantly reduced, and the cross-sectional design allows for stiffness comparable to that of solid bodies. Instead of hollow bodies, lightweight but stable cores with a casing made of a tensile-strength and flexurally rigid material, such as fiber-reinforced plastics, can also be used.

[0038] By appropriately designing the clamping devices, several spring elements can be arranged one above the other in the direction of the load, either in addition to or instead of the parallel arrangement of spring elements in a module. For this purpose, more than two clamping beams can also be provided in a single clamping device.

[0039] The invention is shown below with reference to exemplary embodiments in figures of a drawing and then described.

[0040] This shows:

[0041] Figure 1: Schematic overview of a test device for rotor blades of wind turbines,

[0042] Figures 2, 3: Parts of a test device, wherein a spring module is arranged in different positions relative to the rotor blade to be tested,

[0043] Figure 4: a test device in a perspective view,

[0044] Figure 5: the device from Figure 4 in a schematic side view,

[0045] Figures 6, 7: Views of a spring module with coupling elements in

[0046] Viewed in the longitudinal direction of the spring elements,

[0047] Figures 8, 9: Side views of a spring module and a lever mechanism with different lever ratio configurations.

[0048] Figures 10, 11, 12: different realizations of a 2-point coupling of a spring module to a lever,

[0049] Figure 13: a side view of a spring module with a lever mechanism, wherein the lever is coupled to a free end of the spring module,

[0050] Figure 14: a lever of a lever mechanism, the mass of which is reduced by a telescopic design,

[0051] Figure 15: the arrangement from Figure 14 in a front view,

[0052] Figures 16, 17: Longitudinal sections of spring elements,

[0053] Figure 18: a side view of a spring element,

[0054] Figure 19: another longitudinal section of a spring element,

[0055] Figures 20, 21: Top views of various spring elements,

[0056] Figure 22: a perspective view of a spring element,

[0057] Figures 23 to 25: Cross-sections of various spring modules, Figures 26 to 31: Cross-sectional views of various spring elements, as well as

[0058] Figures 32, 33: various other embodiments of

[0059] Clamping devices.

[0060] To make the test device easily customizable and adaptable, spring elements of uniform length, such as leaf springs, but of varying, graduated widths, can be connected side-by-side in a spring module, depending on the required stiffness. Adjacent spring elements can have the same thickness, at least in sections along their length, to allow for easy clamping together using clamping beams. Figure 1 schematically shows a side view of a spring module 14 with leaf springs. The maximum deflection is limited by the permissible elongation of the spring elements. For this purpose, the beam-shaped spring elements are fixed at their ends, as well as in the middle or at another point between the ends, using clamping devices, also simply called clamps.The clamps at both ends are connected to the clamping frame by means of joints or hinges. One end is mounted to the clamping frame with an additional hinge and a shackle 13 in the form of a rod pivotally connected at both ends, thus allowing movement / extension of the spring module in the longitudinal direction of the leaf spring while simultaneously allowing vertical deflection of the spring elements. The length of the shackle is adjusted so that the line of action 8B' of the load vector at the central clamp / clamping device is almost parallel to a target line of action 8A' of the force acting on the rotor blade in a longitudinal plane of the rotor blade / test specimen 1. To transmit the spring force to the test specimen 1, the force at the central clamp is transferred via a rod 8B, mounted via hinges, to a lever arm 9A, which in turn is connected to the test specimen 1 by means of a rod 8A, for example, with ball joints.The desired (maximum permissible) deflection in the center of the spring assembly / spring module 14 can be adjusted via the lever arm ratio, depending on the desired deflection of the test specimen during testing and / or the spring stiffness. The lever arm is connected to the test specimen 1 via a coupling element in the form of a frame / load frame 4F, which surrounds and clamps the test specimen and is at least partially adapted to its shape. This load frame can advantageously be tilted in a transverse plane so that the line of action of the force acting on the rotor blade is parallel to a target line of action in the transverse plane / in the vertical plane containing the longitudinal axis of the test specimen. To achieve the most comprehensive possible mass reduction in the moving parts of the test device, the spring elements, or at least some of the spring elements, can be designed based on lightweight construction principles.This includes the use of low-density materials with a high modulus of elasticity in the longitudinal direction of the spring elements, such as fiber-reinforced composites. Additionally, a sandwich composite construction can be used for the spring elements, in which a low-density core material is covered on two opposite sides or on all sides with outer layers of a material with a high modulus of elasticity, which may also have a higher density. In this case, the core must possess sufficient shear stiffness. The individual spring elements each have a cross-section that allows for common clamping. For this purpose, their height at the clamping points or in the longitudinal sections intended for clamping is nearly identical. Besides rectangular cross-sections, other cross-sectional shapes are conceivable, as long as clamping in a common clamp / clamping device is possible.Possible cross-sections for spring elements include various trapezoids tilted or inverted about their flat axis, extruded I-profiles, as well as wound box or circular cross-sections. It is advantageous for these different spring elements to have a uniform permissible elongation when combined in a spring module. The cross-section can be constant or vary along the length. Increasing the cross-section of a spring element, particularly increasing its vertical extension, in the middle of the spring module results in high stiffness where deflection is typically greatest. Increasing the cross-section towards the center of a spring element by increasing its width is also conceivable. In a sandwich construction, the core or the face sheets can vary in height along the length of the spring element.

[0061] The lever arm of a lever 9A coupled to a spring module 14 can be designed as a double-T beam to achieve high stiffness with the lowest possible weight. Other cross-sectional shapes of the spring elements, such as a trapezoidal shape or a tubular cross-section, are also possible to efficiently absorb shear forces and bending moments.

[0062] To make rods (connecting rods) lighter, materials such as CFRP (carbon fiber reinforced plastic) or aluminum can be used. High stiffness is essential in these cases. When using CFRP tubes or profiles, clamps are required for support. Coupling to the test specimen / load application to the test specimen is then possible, for example, via clamps or an adhesive bond.

[0063] The support points or coupling points of the spring module 14 or the spring elements can be made movable by using a clamping device to provide a further possibility for adjusting the deflection and stiffness of the spring module. Likewise, the bearing point of the lever arm 9A on the support block can be made adjustable, for example by providing insertable lamination stacks. Fig. 1 shows a side view of a test setup (here shown using the example of a biaxial test setup; uniaxial test setups in the pivot and impact directions with other excitations, for example by means of mass oscillators, are also possible).This illustration demonstrates that the test specimen 1, fixed at a clamping point 1' in a clamping device 2 of the clamping field 3, is to be excited in the system at nearly its natural frequency by active load application devices with actuators 5B and 5A, respectively, in the pivoting and impact directions. Actuator 5A is connected to the clamping field 3 via a joint 11N. At its other end, a joint UM connects actuator 5A to a load frame 4A. The load application device with actuator 5B is also connected to the clamping field 3 via a joint 11L. At its other end, a joint 11K connects actuator 5B to a lever arm 9C, which is connected at a right angle to an angle beam 16. This angle beam is supported by hinge IOC. The load from the actuator 5B is transferred via beams 9C and 16 at a right angle to the load introduction of the actuator 5B to the test specimen 1 via a rod 8C.For this purpose, rod 8C is connected to the load frame 4A via a joint 11J, which introduces the loads into the test specimen 1.

[0064] The test specimen 1, or in this case the rotor blade, is equipped with a further load frame 4F, which can move almost vertically upwards and downwards relative to an initial position 4F' of the longitudinal axis of the test specimen 1 by deformation of the rotor blade. This load frame 4F is connected to the rod 8A via a joint HP and thus transmits the forces from the test specimen 1 to the rod 8A. The line of action of the force on the rod in its rest position is designated 8A' and is advantageously aligned normal to the longitudinal axis of the test specimen in its initial (unloaded) position 4F' to avoid parasitic forces. The rod 8A is connected to the lever arm 9A via a further joint 11Q. The lever arm 9A is mounted at one end via a hinge 10D to allow tilting of the lever arm. A plate assembly 20C allows adjustment of the mounting height.This allows the joints / hinges 10D, 11A, 11Q to be advantageously positioned in a common effective lever arm line 9A', which can be aligned orthogonally to the position of one or both of the lines of action 8A' or 8B' to avoid parasitic forces.

[0065] At a point between its ends, for example in its middle, the lever 9A is connected via a joint 11A to another rod 8B, which is connected via a joint 11B to an elastic element 14, shown here as a spring module 14 with leaf springs, and thus transmits forces between the lever arm and the spring module.

[0066] The spring module 14 is supported at both ends by hinge joints 10A and 10B, which are connected to the clamping frame 3. The spring moves almost symmetrically about its axis 14' in its rest position, which is almost parallel to the lever arm axis 9A'. At one end of the spring, a shackle 13 is additionally inserted between the hinge joint 10E, which is fixedly connected to the clamping frame, and the hinge joint 10B, which is fixedly connected to the spring module. This allows the spring to be mounted as a floating bearing, thus permitting horizontal displacement of the joint 10B when the spring deflects. The rest position of the spring can also be asymmetrical to apply a preload.

[0067] The aim of arranging the individual components, in particular the directions of movement of the rods for connecting the components, is to design them in such a way that the greatest possible force acts normal to the longitudinal axis of the test specimen / rotor blade and parasitic forces (losses) are minimized.

[0068] Several variations of the arrangement shown are possible.

[0069] In addition to the variant shown in Fig. 1, Fig. 2 shows a variant of the setup in which the lever 9A and the spring module 14, with their respective longitudinal axes 9A", 14", are aligned transversely to the plane of the drawing and to a vertically oriented plane containing the longitudinal axis of the test specimen. This variant of the alignment represents a further possibility in which the joints 11A, 11Q, and the hinge joint 10D can be arranged on a common straight line 9A" using the plate assemblies 20C. The advantage of this arrangement is that the rod 8A is tilted only in the plane of the drawing by movement of the rotor blade 1 in the y-direction / vertical direction, which allows the joint 11Q to also be designed as a hinge joint. Furthermore, this alignment along the rotor blade 1 is more space-saving, allowing more load elements of the test fixture to be placed closer together.

[0070] Figure 3 shows a variant of the test device setup in which the longitudinal axis of the lever arm 9A is oriented transversely to the longitudinal axis 14" of the spring module 14. The longitudinal axis 14" of the spring module 14 is oriented perpendicular to the longitudinal axis of the rotor blade 1. The axis of rotation 10D' of the hinge joint 10D at one end of the lever arm 9A is therefore also oriented parallel to the longitudinal axis 14" of the spring module 14 and thus perpendicular to the line of action of the force transmitted from the spring module 14 to the lever 9A.

[0071] Another variant, not shown, provides for the alignment of the lever 9A transversely to the longitudinal axis of the rotor blade 1 and the alignment of the longitudinal axis of the spring module 14 transversely to the longitudinal axis of the lever 9A, which may be advantageous under certain conditions in terms of the space utilization of the test setup or in terms of the utilization of the joint angles.

[0072] Besides variants where the joints / hinge joints 10D, 11A, and 11Q form a line, other variants are conceivable that generate the lowest possible parasitic forces. In these variants, the connecting line between the joints / hinge joints 10D and 11A (effective lever arm of the spring) can be aligned orthogonally to the line of action 8B," and this line, in turn, can be aligned orthogonally to the longitudinal axis 14' or 14" of the spring module. Simultaneously, the connecting line between 10D and 11Q (effective lever arm of the rotor blade) is aligned orthogonally to the line of action 8A," and this line, in turn, can be aligned orthogonally to the position 4F' of the longitudinal axis of the rotor blade 1 in its rest position.

[0073] Mathematically speaking: The position 4F' of the longitudinal axis and the position of the longitudinal axis of the spring module 14' (or 14") should be parallel to a plane defined by the hinge axis in 10D and the respective effective lever arm (10D-11Q for 4F' or 10D-11A for 14' or 14"). The respective rod 8A or 8B is positioned with its longitudinal axis perpendicular to the respective plane.

[0074] In principle, all possible angular alignment combinations between test body / rotor blade 1, lever 9A and spring module 14 are feasible within the framework of the test device according to the invention.

[0075] Fig. 4 shows a detailed perspective view of a spring module 14 integrated into the test device. It illustrates one possible embodiment of the clamping devices / clamps 15A, 15B, 15C of the individual spring elements forming a spring assembly 21. In the example shown, the clamps are arranged at the ends and in the middle of the spring elements 14A, 14B, 14C, 14D, each of which is designed as a leaf spring with a rectangular cross-section. Further possible cross-sectional designs of the spring elements are shown in Figures 23 to 31 and explained below. Figure 4 illustrates by way of example that spring element 14B is wider and therefore stiffer than the other spring elements. By combining spring elements of different widths and stiffnesses, a desired overall stiffness of the spring module 14 can be achieved. The longitudinal axis of the spring module is denoted by 14'.

[0076] The lever arm 9A is shown in Figure 4 as an example construction consisting of two double-T-shaped metal profiles 22A, 22C, which are provided with stiffening plates 17A, 17B. This results in high stiffness with high material utilization. The lever arm 9A is supported at the edge of the lower stiffening plate 17B by hinges 10D and plate assemblies 20C on the support frame 23, which is formed by the beams 18A, 18B, 18C, 18A', 18B'. The beams 18A, 18B, 18A', 18B' are connected to the clamping span 3 by plate assemblies 20A, 20B. An inclination of the support frame 23 about the longitudinal axis 14' of the spring module 14 can be achieved via angle plates 19A, 19B and the corresponding thickness of the (number of plates) plate packages 20A, 20B, which can be used to reduce forces in undesired directions.

[0077] Fig. 5 shows a side view of the structure shown in Fig. 4. This illustrates the possible adjustment of the height of the supports 18A, 18B as well as the inclination of the support frame by means of sheet metal stacks / plate stacks 20A, 20B and angle plates 19A 19B; so that the joints / hinge joints 11Q, 11A, 10D lie almost on an axis 9A' (optimal position of the axis 9A' cf. Fig. 1).

[0078] Fig. 6 shows a front view of a structure according to Fig. 3. Fig. 6 illustrates that the support frame 23 can be inclined by means of angle plates 19A, 19A' to follow the inclination of the rotor blade about its longitudinal axis (pitch angle) and thus adapt the line of action of the force from the spring assembly 8B" parallel to the direction of movement of the blade 8A" (shown in Fig. 3). The spring module 14 remains in a straight, non-inclined position. This reduces undesired lateral forces on the rotor blade. 11B denotes a spherical bearing that compensates for the inclination of the support frame 23 relative to the spring module 14 and compensates for an angular deviation of up to 4 degrees with a fixed connection. Fig. 7 shows a variant with tilted support frame 23 over the angle plates 19C, 19C' and inclination of the spring module 14, such that the inclination of the spring module 14 corresponds to the inclination of the support frame 23.This advantageously reduces lateral forces on the hinges 10A, 10A'.

[0079] Fig. 8 shows an embodiment with an extended lever arm 9A'. A sheet metal stack 20C" is provided between the lever 9A' and the joint 11A. This variant has the advantage that the space between the spring and the lever below the rod 8A remains free and can be used for other elements of the test device not shown.

[0080] Fig. 9 shows clamping devices / clamps 15A, 15B, and 15C. Each clamp can be moved and fixed longitudinally along the spring module 14 relative to the arrangement shown in Fig. 5 to achieve the desired stiffness and leverage ratios. The respective joints / hinge joints 10A, 10B, and 11B are moved along with it. Clamp 15B can be moved asymmetrically between clamps 15A and 15C. Joint 11A is moved further in the direction of joint 11Q. This embodiment thus demonstrates further adjustment possibilities for the test device. In this variant, joints / hinge joints 11A, 11Q, and 10D can be positioned almost in a straight line.

[0081] Figures 10-12 show variants of load introduction into the spring module 14 by means of a four-point bending, whereby the transverse forces in the area of ​​the support are eliminated and a pure bending of the spring elements is produced. The hinge joints 11B' and 11B" attached to the clamps 15B' and 15B" serve this purpose.

[0082] In the variants shown in Figures 10 and 11, the load is introduced into the spring module via a fixed bearing and a floating bearing. Here, 15B' is designed as the fixed bearing and 15B" as the floating bearing. Figure 10 shows a variant in which the load is applied via a crossbeam 27. This crossbeam 27 is connected to the lever 9A via a further hinge 11B, the rod 8B, and the joint 11A. In Figure 11, the load is introduced via a stiffening plate 29 with a recess, and both the crossbeam 27 and the hinge 11B and rod 8B are omitted, making the construction lighter and more robust than the variant shown in Figure 10.

[0083] Fig. 12 shows an embodiment in which a fork 28 is attached to the hinge joint 11A, to which two rods 8B' and 8B" are pivotally connected. These are in turn connected to the hinge joints 11B' and 11B" and thus transmit the load to the spring module 14 via the clamps.

[0084] Fig. 13 shows a variant of the spring module with one-sided clamping in the bearings 10A, 10B, and 10E. In this example, this is achieved by using two adjacent supports to realize the clamping. One-sided support allows for greater freedom in positioning the spring module 14 and the lever arm 9A, enabling more efficient use of the available space. A disadvantage of this embodiment is the increased lateral forces on the bearing points.

[0085] Fig. 14 shows a variant of a lever 9A composed of tubular profiles 24B, 24C, 24D, 24E. Tubular profiles with different cross-sections or increasing diameters are connected to one another or slid into one another and positioned so that the diameter, and thus the stiffness, is greater where the bending moment is greater. The lever is preferably supported by clamps or vises 25A, 25B to which the hinges 11Q, 11A, 10D are connected. This composite lever 9A connects the spring module (not shown) via the rod 8B and the hinge joint 11A to the hinge joint 11Q and the rod 8A for load transmission into the test specimen. The hinge 10D serves to support the lever 9A. In this embodiment, the mass of the lever 9A can advantageously be reduced where a large acceleration is acting (in the region of the hinge joint 11Q).

[0086] Fig. 15 shows a variant of a lever arm 9A made of tubular profiles, as depicted in Fig. 14, in a frontal view. Fig. 16 shows a side view of a spring element 14A in sandwich construction with scarfed skins / cover layers 31 and a core 32 with a core thickness that is constant along its length, to increase the profile height at the center of the spring element with respect to its longitudinal direction. The increase in profile is achieved via a scarf angle 30 in a plane in the direction of the thickness. This results in the stiffness of the spring element 14A being greatest where the deflection is greatest.

[0087] Fig. 17 shows a side view of a spring element 14A in sandwich construction with a scarfed (angle 30°) core 32 to increase the profile height in the center of the spring module. In this case, skins / cover layers 31 of constant thickness, for example from a pultrusion process, can be used, which simplifies manufacturing.

[0088] Fig. 18 shows a variant of the spring element 14A with connected or nested tube elements 24J, 24K, 24L, 24M with an increasing diameter towards the spring center. The tube elements can be manufactured, for example, in a winding process. This design enables a very lightweight construction with simultaneously high stiffness.

[0089] Fig. 19 shows a variant of the structure shown in Fig. 15, in which the skins / cover layers 31 at the ends and in the middle of the spring element 14A are provided with flattened areas or areas of constant thickness 33, 33', 33" to allow the clamps to be mounted there. Further areas of constant thickness can also be provided along the spring element to allow clamps to be mounted at various locations.

[0090] Figures 20 and 21 each show a top view of a spring element 14A with a width that varies along its length, in order to achieve maximum stiffness in the area of ​​greatest deflection in the central region of the spring element. The change in width occurs at a scarf angle 34 in a plane in the longitudinal direction. Besides a variant with straight edges (Fig. 19), a variant with a curved width profile 35 is also conceivable to achieve a more uniform stiffness distribution. Fig. 22 shows a perspective view of a profile of variable thickness and width along its length, using the example of a box section 36, which is narrower and taller in the middle of its length than at the ends. This makes it possible to increase the stiffness towards the center of the spring element, where the deflection is greatest.

[0091] Fig. 23 shows a spring module with four spring elements 14A, 14B, 14C, 14D, each with a rectangular cross-section, in a sandwich construction with a core 32, for example, made of foam or lightweight wood (balsa), and with outer layers 31 made of a fiber-reinforced plastic. The individual spring elements are arranged in the spring module 14 with lateral spacing between them, as seen in cross-section. The width of the individual spring elements can vary so that their properties can be selected to match the desired properties of the spring assembly. These are connected by a clamp 15A with clamping bars 15D, 15E, which are connected to each other at several points, for example at their ends, by means of connecting elements 100A, 100B. The connecting elements can, for example, comprise threaded rods or screws and nuts, so that the spring elements can be reliably held between the clamping bars by means of a force-fit connection.

[0092] Fig. 24 shows a spring module with four spring elements 14A, 14B, 14C, 14D, each with a trapezoidal cross-section, in a sandwich construction with a core. The trapezoidal shape allows for better interlocking of the individual spring elements.

[0093] Fig. 25 shows a spring module made of spring elements 14A, 14B, 14C, 14D in the form of tubular profiles, which are produced, for example, in a winding process and are clamped to form a spring module between the clamping beams 15D, 15E.

[0094] Figures 26-31 show variants for individual spring elements 14A in cross-section.

[0095] Fig. 26 shows a single spring element 14A in sandwich construction with integrated webs 37, 37', 37" at the edge and in the middle, viewed in cross-section, to increase shear stiffness; compared to the embodiment shown in Fig. 23, in which the spring elements themselves do not have webs 37, a more shear-flexible and therefore lighter core 32 can be used, for example. The outer layer is designated 31.

[0096] Fig. 27 shows a sandwich element manufactured using a winding method, with a wound core 32, which enables efficient and automated manufacturing.

[0097] Fig. 28 shows a variant of a spring element 14A in the form of a tube with individual, for example cylindrical, recesses 38 in the tube wall (modeled as a bionic profile on the shape of a plant stem) in order to generate very high stiffness at low weight.

[0098] Fig 29: shows a spring element 14A in the form of a double-T profile, for example from a pultrusion process, which can originate from an automated and therefore cost-effective production.

[0099] Figures 30 / 31 show pultruded cross-sections of a figure-eight profile. These can be notched, rolled, or drawn from a strand. Figure 30 shows a variant with a solid cross-section 40, and Figure 31 shows a variant with a hollow cross-section 40'. These profiles exhibit advantageous resistance to shear buckling.

[0100] Figure 32 shows a spring module 14 in which a number of 5 spring elements 14F, 14G, 14H, 14i, 14J are arranged both side by side and one above the other in cross-section. Such a combination allows, for example, a desired ratio of the stiffnesses of the spring module in the various directions 101, 102 perpendicular to its longitudinal direction to be set in the case of biaxial loading. Three clamping bars 15G, 15H, 15i, aligned parallel to each other, are provided for clamping the spring elements 14F, 14G, 14H, 14i, 14J. The spring elements 14F and 14G are clamped between the clamping bars 15G, 15H, while the spring elements 14H, 14i, and 14J are clamped between the clamping bars 15H and 15i.The clamping beams each have adhesive or compensating layers 103, 104 on their sides facing the spring elements. These layers are made of a material that is softer than the material of the clamping beams and can compensate for different heights of the spring elements. The compensating layers 103, 104 can, for example, be made of a hard rubber or a plastic. Instead of three clamping beams, more than three, for example four or five clamping beams, with spring elements arranged between them, can also be used.

[0101] Figure 33 shows a spring module 14 with a clamping device comprising slightly curved clamping beams 15J, 15K, between which spring elements 4i, 14J are clamped. The curvature of the clamping beams is somewhat exaggerated for clarity. Even a slight curvature of the clamping beams significantly stiffens the spring module when using identical spring modules. Furthermore, such an arrangement allows the ratio of the stiffnesses of the spring module in the various directions 101, 102 perpendicular to its longitudinal axis to be adjusted. The distance between the clamping beams 15J, 15K can be constant along the clamping beams, allowing the use of spring elements with a rectangular cross-section.

[0102] Reference sign

[0103] 1 test specimen

[0104] 1' Clamping point of the test specimen

[0105] 2 Clamping device

[0106] 3 span

[0107] 4 load frames

[0108] 4' axis through test specimen

[0109] 5 Actuator

[0110] 6 7

[0111] 8 bars

[0112] 8' Line of action through rod in a plane almost parallel to the test specimen 8” Line of action through rod in a plane almost perpendicular to the test specimen

[0113] 9 Lever arm 9' Axis through lever arm in a plane almost parallel to the test specimen

[0114] 9” axis through lever arm in a plane almost perpendicular to the test specimen

[0115] 10 hinge

[0116] 11 Joint (cardan or ball joint)

[0117] 12 -

[0118] 13 shackles

[0119] 14 Elastic element / spring

[0120] 14' axis through elastic element in a plane almost parallel to the test specimen 14” axis through elastic element in a plane almost perpendicular to the test specimen 15 clamp

[0121] 16 angle beams

[0122] 17 Stiffening plate

[0123] 18 carriers

[0124] 19 Angle plate

[0125] 20-plate pack

[0126] 21 Package of elastic elements / spring package

[0127] 22 Meta II profile

[0128] 23 support frames

[0129] 24 pipe profile

[0130] 25 clamping devices

[0131] 26 Complete package consisting of 15A, 15B, 15C, 21, 13A, 13B, 13C

[0132] 27 Traverse

[0133] 28 Fork

[0134] 29 Stiffening plate

[0135] 30 scarf angles in one plane in the thickness direction

[0136] 31 Skin

[0137] 32 cores

[0138] 33 Area of ​​constant thickness

[0139] 34 Shaping angles in a plane in longitudinal direction

[0140] 35 Curved latitude profile

[0141] 36 Profile of variable thickness and width along its length

[0142] 37 Pushbridge

[0143] 38 recess

[0144] 39 Double-T profile

[0145] 40 figure-eight profile (either notched, rolled or drawn from a strand, either solid or hollow)

Claims

Patent claims 1. Test device for the mechanical testing of a beam-shaped test specimen (1), in particular a rotor blade, comprising a clamping device (2) anchored in a clamping field (3) for clamping the beam-shaped test specimen at a clamping point (1') of the beam-shaped test specimen, one or more coupling elements (4A, 4F) connected to the beam-shaped test specimen, in particular load frames, one or more active load application means (5A, 5B) each connected to a coupling element, and one or more passive load application means each connected to a coupling element, at least one of which has a spring device connected to the clamping field, which is configured to exert a force on the test specimen in a spring loading direction, characterized in that the spring device has at least one spring module (14) with at least one detachable retaining device (15A, 15B, 15B', 15B", 15C, 15F,15 L) for the detachable mounting of a selectable number of one or more mechanically parallel connected, in particular identical, spring elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J).

2. Test device according to claim 1, characterized in that at least one spring module (14) has spring elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J) in the form of one or more beam elements arranged parallel to each other, in particular in the form of leaf springs, wherein the beam elements are arranged next to each other in a direction transverse or perpendicular to the direction of spring loading.

3. Test device according to one of claims 1 or 2, characterized in that at least one spring module (14) is provided at at least one of its ends is connected to the clamping field (3) by means of a joint (10A, 10E) or a hinge joint.

4. Test device according to one of claims 1 to 3, characterized in that at least one spring module (14) is connected at one of its ends by means of a shackle (13) to a joint (10E) or hinge joint which is connected to the clamping field (3).

5. Test device according to one of claims 1 to 4, characterized in that at least one spring module (14) has one or more retaining devices in the form of releasable clamping devices (15A, 15B, 15B', 15B", 15C, 15F, 15L) in which one or more beam elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J) or leaf springs can be clamped.

6. Test device according to claim 5 characterized in that at least one clamping device (15A, 15B, 15B', 15B", 15C, 15F, 15L) is displaceable along a spring module (14) and is configured to clamp the beam elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J) or leaf springs of the spring module selectively at one of several positions.

7. Test device according to claim 5 or 6, characterized in that at least one clamping device (15A, 15B, 15B', 15B", 15C, 15F, 15L) is connected to the clamping field (3) by means of a joint (10A, 10E) or a hinge joint and / or that at least one clamping device is connected to a joint (1OE) or hinge joint which is connected to the clamping field by means of a shackle (13).

8. Test device according to claim 5, 6 or 7, characterized in that at least one clamping device is connected to the test specimen (1) by means of a transmission element, in particular by means of a lever (9A).

9. Test device according to one of claims 2 to 8, characterized in that at least one spring module (14) is located at only one or at least two points along the longitudinal direction of the beam elements (14A, 14B, 14C, 14D, TI 14E, 14F, 14G, 14H, 14i, 14J) or leaf springs connected to the clamping field (3).

10. Test device according to one of claims 2 to 9, characterized in that a holding device connected to the test specimen (1) in the form of a clamping device (15A, 15B, 15B', 15B", 15C, 15F, 15L) is located between two clamping devices connected to the clamping field (3) in the longitudinal direction of the beam elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J) of a spring module (14) or that a spring module is only fixedly clamped on one side to the clamping field and a clamping device connected to the test specimen clamps the spring module at one point along the longitudinal direction of the beam elements of the spring module.

11. Test device according to one of claims 2 to 10, characterized in that the spring module (14) is connected to the test specimen (1), in particular a rotor blade or a lever arrangement (9A) connected to the rotor blade, at only one or at least two points along the longitudinal direction of the beam elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J) or leaf springs.

12. Test device according to one of claims 2 to 11, characterized in that several beam elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J) are arranged parallel to each other in a spring module (14) and that at several points or at all points along the longitudinal direction of the beam elements several or all beam elements have the same thickness in the direction of the mechanical load for which the spring module is intended, such that they can be clamped together by a clamping device (15A, 15B, 15B', 15B", 15C, 15F, 15L).

13. Test device according to one of claims 2 to 12, characterized in that several beam elements of different stiffness (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J), in particular several leaf spring elements of different widths, are arranged parallel to each other in a spring module.

14. Test device according to one of claims 2 to 13, characterized in that one or more clamping devices (15A, 15B, 15B', 15B", 15C, 15F, 15L) are provided on a spring module (14), each having two clamping beams (15D, 15E, 15G, 15H, 15i, 15J, 15K) that can be connected or are connected by connecting elements (100A, 100B), between which the flexible beam elements (14A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14i, 14J), in particular in the form of leaf springs, can be clamped.

Images