Tensile testing rig

Abstract

A tensile testing rig comprising a support (4) for holding a test element (8, 24) consisting of a test material (7), wherein the test material (7) is a laminated material and is formed from at least a first layer (26) and a second layer (27), and with a drive unit (5) for generating a tensile force, wherein the drive unit (5) can be connected to the test element (8, 24) by means of a connecting element (14), wherein, in order to generate a highly dynamic tensile test, the drive unit (5) is designed in the form of a hydraulic unit, comprising a hydraulic device (16), characterized in that the drive unit (5) has a hydraulically actuated piston (11) movably received in a cylinder (10), which is connected to the connecting element (14), wherein a motion compensation element (25) is arranged between the piston (11) and the connecting element (14).wherein the connecting element (14) is secured to the tensile testing rig (1) by means of a locking element (15).

Description

[0001] Tear test rigs are used for tear testing, particularly on components that are bonded together by adhesive bonding or another joining method. Tear testing can also be performed on components bonded together using heat or pressure, where the application of heat or pressure creates a quasi-bonded bond between the connected components (e.g., chemical-physical adhesion during a polyurethane foaming process). The aforementioned bonded joints are also referred to as lamination.

[0002] Laminating involves bonding multiple components together in layers of the same or different materials, for example, to protect one of the materials. Laminating can also serve a decorative purpose, or it can be used to create favorable material properties for the interconnected components through addition.

[0003] US Patent No. 2,473,517 A discloses a tear test stand which, for measuring the adhesive strength of an adhesive, uses an electric motor at a constant speed to vertically tear a test strip, which is attached to a flat plate by means of the adhesive, from the horizontally positioned plate. The motor and the plate are arranged in a horizontal plane, with a cable extending from the motor and guided vertically over two pulleys onto the test strip. The end of the cable facing away from the motor is connected to the test strip by means of a spring balance.

[0004] No. 3,019,644 A discloses a tear test stand designed to test the bonding strength between two layers, at least one of the layers being relatively flexible, and in particular an electronically conductive layer of copper being arranged on an insulating layer. The tear test stand features synchronous movement of the insulating layer and the copper track applied to the insulating layer, with the insulating layer being pulled horizontally and the copper track vertically, each via a cable. The two cables are attached at their ends facing away from the layers to cable wheels for winding up, with the two cable wheels being arranged for rotation on a common shaft. The cable moving the insulating layer is additionally brought into a horizontal position via a deflection pulley.The shaft is set in rotation via a chain drive with the help of an electric motor which has a gearbox.

[0005] US Pat. No. 3,580,065 A discloses a tear test stand that differs significantly from the two aforementioned tear test stands in that a test strip, held vertically, is released by a vertical downward movement of a plate connected to it. The downward movement is achieved by means of a pneumatic cylinder. The tear test stand is designed for testing printed circuit boards.

[0006] US Pat. No. 6,185,999 B1 discloses a tensile test stand designed specifically for testing the peel strength between a circuit board and a cable arranged thereon. A carrier plate that holds the cable and is integrally connected to it is movable horizontally along two axes, with the two axes being orthogonal to each other. The cable is pulled upwards in a vertical direction from the carrier plate. A drive for the tensile test stand is implemented in the form of a computer-controlled actuator.

[0007] The published patent application JP 2006 - 194 599 A discloses a tear test rig which is designed for the tear testing of layers, whereby the layers cannot necessarily be separated at an angle of 180°.

[0008] Due to their drive, the known tear test stands mentioned above are not suitable for carrying out highly dynamic tear tests, which are characterized by tear-off speeds of more than 5 m / s.

[0009] The use of a hydraulic device in a tear test rig is generally known from Japanese Patent Application JP 2004 - 333 221 A. Test rigs for dynamic material testing are also known from US 2004 / 0 107 776 A1 and US 7 681 459 B1. However, none of these allow for a tear test of a test element consisting of two layers that runs vertically to the drive device.

[0010] The object of the present invention is to provide a tear test bench for simulating the behavior of a component made of a laminated material that is subjected to sudden, in particular explosive, stress.

[0011] The object is achieved according to the invention by a tear test stand having the features of patent claim 1. Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the respective subclaims.

[0012] A tear test stand according to the invention comprises a support for holding a test element consisting of a test material, wherein the test material is a laminated material and is formed from at least a first layer and a second layer. Furthermore, the tear test stand comprises a drive unit for generating a tear force, wherein the drive unit can be connected to the test element by means of a connecting element. To achieve a highly dynamic tear test, the drive unit is designed in the form of a hydraulic unit comprising a hydraulic device.According to the invention, the drive unit has a hydraulically actuated piston which is movably received in a cylinder and is connected to the connecting element, with a movement compensation element arranged between the piston and the connecting element, the connecting element being secured to the tear test stand by means of a securing element. The advantage is the realization of a suddenly high tear force with the help of the drive unit designed as a hydraulic unit, whereby an unhindered uniaxial movement in the direction of a third axis Z of the piston can be realized. Since the tear test stand according to the invention is designed to bring about a high tear speed, there is the possibility that the connecting element swings out unsecured in the test stand at the end of the test depending on the tear-off direction. The securing element is provided to prevent or reduce uncontrolled oscillation.

[0013] Drive units powered by an electric motor have the disadvantage that at least one coupling element and / or a gear element and / or deflection element must be provided so that a tearing force can act on the test element connected to the drive unit, which, however, induces friction losses. Pneumatically designed drive units involve compression of the gaseous medium, which means that the tearing force cannot be generated suddenly. "Sudden" in this context means explosive, thus immediate and with great force. A tearing speed of at least 5 m / s is required for this explosiveness to be realized.This tear speed, which can be increased to up to 20 m / s with the tear test bench according to the invention due to its drive unit designed as a hydraulic unit, allows in particular a simulation of an airbag explosion in an accident, so that the behavior of a vehicle component provided with the laminated material and accommodating the airbag, which can also be referred to as an air cushion, in particular an instrument panel, which is also referred to as a dashboard, can be tested in accordance with real behavior.

[0014] To initiate the tear force, the piston can be actuated using a control valve. This represents a simple and cost-effective design of the tear test stand according to the invention, with the control valve preferably being opened or closed electronically.

[0015] In a further embodiment of the tear test stand according to the invention, a camera is assigned to the tear test stand for visual recording of the tear test. This means that after the tear test has been performed, the behavior of the laminated material can be analyzed in detail. The camera system has a frame rate of at least 2,000 frames per second.

[0016] Preferably, the test element has at least one marking symbol, wherein the marking symbol exhibits changes in shape during the tear test, and thus the behavior of the test material can be analyzed in an improved manner.

[0017] A particularly cost-effective tear test bench can be realized if the drive unit has a closed hydraulic circuit, since a hydraulic fluid present in the circuit can be used repeatedly.

[0018] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. Identical or functionally equivalent elements are assigned identical reference numerals. They show: Fig. 1 shows a side view of a tear test stand according to the invention, and Fig. 2 in a detailed view of the tear test bench with a test object on a support of the tear test bench according to. Fig. 1.

[0019] A according to Fig. 1, the tear test stand 1 according to the invention has a support device 3, preferably made of profile bars 2, which, in addition to the fixed mounting of a support 4 receiving a test object 24, is designed to receive a drive unit 5, which is configured in the form of a hydraulic unit. Comprising the support device 3, a test stand housing 6 is designed, particularly for safety reasons, with a door (not shown in detail), in particular an electronically controllable door. The tear test stand 1 is designed to measure the tear-off behavior of a laminated test material 7, wherein the laminated test material 7 is designed to correspond to a decorative material of a body component receiving a so-called airbag, wherein in the present exemplary embodiment, the body component is a dashboard, which can also be referred to as an instrument panel.

[0020] The airbag is designed to prevent or mitigate the impact of a vehicle occupant on the body component containing the airbag—in this exemplary embodiment, the dashboard. In the event of a motor vehicle accident, the airbag deploys explosively as a function of the acceleration acting on the vehicle. In other words, the airbag opens within a short period of time, and the body component provided with the decorative material is suddenly subjected to a force generated by a so-called airbag deployment. The tear test bench 1 according to the invention is designed to simulate a realistic, highly dynamic tear-off event induced by an airbag deployment.

[0021] For improved explanation, a Cartesian coordinate system formed from the coordinate axes X, Y and Z is introduced, which are referred to below as axes, wherein the first axis X and the second axis Y indicate a length extension and a width extension, respectively, and the third axis Z indicates a height extension of the tear test stand 1.

[0022] In the present exemplary embodiment, the test material 7 is constructed from a first layer 26 and a second layer 27 bonded to the first layer 26. The first layer 26 is in the form of a skin, leather, or plastic, extending over the dashboard, and the second layer 27, which lies along the third axis Z beneath the first layer 27 and thus faces the support 4, is in the form of a foam, which is usually elastic and yields under load.

[0023] A test element 8 formed from the test material 7 is in the form of a rectangular strip. In the present exemplary embodiment, the test object 24 has three test elements 8 arranged next to one another in the direction of the first axis X, with the first layer 26 of the test element 8 being separated from the first layer 26 of the remaining test object 24 over its entire circumference by means of a cut. In other words, this means that three rectangular sectional images are formed in the first layer 26 of the test object 24.

[0024] At this point, it should be mentioned that a different number of test elements 8 could also be formed in the test object 24. Or, a single test element 8 could be arranged on the carrier 4 for testing, in which case the test object 24 would simultaneously be the test element 8.

[0025] The test object 24 is accommodated predominantly in the horizontal direction, extending in the direction of the X and Y coordinates, between the profile bars 2 of the support device 3.

[0026] Viewed from the support 4, the drive unit 5 is supported above the support 4 on a cross member 9 extending predominantly in the direction of the first axis X, wherein the cross member 9 is arranged between the profile bars 2 extending predominantly in the direction of the third axis Z. The drive unit 5 has a hydraulically movable piston 11 received in a cylinder 10, wherein the piston 11 is designed to be able to perform a movement in the direction of the third axis Z. In other words, this means that the piston 11 is acted upon by a hydraulic fluid, wherein it moves up or down in the direction of a longitudinal axis of the cylinder 10, encompassed by the latter. The longitudinal axis of the cylinder 10 is designed to extend along the third axis Z.

[0027] At an end of a piston rod 12 of the piston 11, which is fixedly connected to the piston 11 and is designed to face the carrier 4, a force measuring element 13, which in the present embodiment is designed in the form of a piezoelectric element, is arranged for measuring a tearing force.

[0028] The piston rod 12 is firmly connected to a first end region 28 of the first layer 26 of the test element 8 by means of a connecting element 14, wherein the connecting element 14 is designed in the form of a clamp. This means that the first end region 28 has been detached from the second layer 27 of the test element 8 over an extension of the first end region 28 for fixation in the clamp 14. The first end region 28 of the first layer 26 corresponds to an end region of the test element 8, from which the first layer 26 is torn off from the second layer 27. The force required to separate the two layers 26, 27 corresponds to the tear force.

[0029] The first end region 28 is received between two clamping elements 35 of the clamp 14, wherein the two clamping elements 35 are pressed together by means of two fastening elements 36 for securely receiving the first end region 28.

[0030] A second end region 29 of the first layer 26 is formed facing away from the first end region 28 in the direction of the second axis Y. During the test of the tear-off behavior, starting from the first end region 28, the first layer 26 of the test element 8 is pulled upwards in the direction of the third axis Z with the aid of the piston 11, thus pulling it away from the second layer 27, whereby a region of the test element 8 formed between the first end region 28 and the second end region 29 is completely or partially separated from the second layer 27. The test is terminated at the latest when the second end region 29 of the first layer 26 is also completely or partially detached from the second layer 27.

[0031] Between the clamp 14 and the piston rod 12, a movement compensation element 25 is arranged, which in the present embodiment is designed in the form of a relatively flexible wire rope 25 so that an unhindered uniaxial movement in the direction of the third axis Z of the piston 11 can be realized.

[0032] To prevent the first layer 26 of the test element 8, which is connected to the clamp 14, from dangling in an unsecured and / or undirected manner after the test strip 8 has been torn off or torn, the clamp 14 is connected to at least one securing element 15 in the form of a catch strap. Preferably, three catch straps 15 are provided.

[0033] At this point it should be mentioned that depending on a bonding force developed between the first layer 26 and the second layer 27, at the end of the tear-off the first layer 26 can of course partially adhere to the second layer 27 and vice versa.

[0034] To ensure that a force corresponding to an explosion of the air cushion can be exerted on the test element 8, the drive unit 5 comprises a hydraulic device 16, wherein the cylinder 10 is connected to the hydraulic device 16 and can be acted upon by the hydraulic device 16. Furthermore, the drive unit 5 has a closed hydraulic circuit 17.

[0035] The hydraulic device 16 comprises a delivery unit 30, which feeds the required hydraulic fluid from a relief accumulator 19 of the circuit 17 into a high-pressure accumulator 20, which is formed upstream of the cylinder 10, via a flow-through first line 18 of the circuit 17, via a flow-through second line 21. A flow-through third line 22 of the circuit 17 is formed between the cylinder 10 and the high-pressure accumulator 20, wherein the third line 22 has a control valve 23, with the aid of which the third line 22 can be blocked or released for the hydraulic fluid.

[0036] The third line 22 is connected to the cylinder 10 in a flow-through manner, which has a receiving opening 37 in an end region 31 of the cylinder 10 facing the carrier 4, establishing the flow-through connection. Thus, the hydraulic fluid can push the piston 11 along the third axis Z in the direction facing away from the carrier 4, thus upwards. The hydraulic fluid displaced in the cylinder 10 due to the movement of the piston 11 flows into the relief accumulator 19 via a flow-through fourth line 38, which is designed to connect the cylinder 10 to the relief accumulator 19 in a flow-through manner. The tear test stand 1 according to the invention is designed to realize tear-off speeds of up to 20 m / s, which accordingly enables a simulation of the real load of an explosion of the air cushion.

[0037] For improved evaluation of the tear-off behavior, a camera 32, in the form of a so-called high-speed camera, is assigned to the tear test stand 1, which is aligned in the direction of arrow 33 for recording. With the help of the camera 32, the tear test process is thus visually recorded for later evaluation. For this purpose, the test element 8 preferably has a plurality of symmetrically arranged marking symbols 34, wherein in the present embodiment, the marking symbol 34 is designed in the form of a dot, as in Fig.2. These marking symbols 34 change their shape due to tearing over the test period and, in particular, exhibit constrictions and / or expansions, which can be captured using snapshots from the camera 32 and preferably evaluated after the test has ended. It should be noted at this point that in the present exemplary embodiment, the test element 8 has an extension in the direction of the first axis X with a value of 5 cm and an extension in the direction of the second axis Y with a value of 30 cm.

[0038] The test can be started electronically, for example, using a control signal from a computer by opening the control valve 23. List of reference symbols 1 tear test bench 2 profile bars 3 Carrier device 4 carriers 5 Drive unit 6 test bench housings 7 Test material 8 test element 9 cross members 10 cylinders 11 pistons 12 Piston rod 13 Force measuring element 14 Connecting element 15 Securing element 16 Hydraulic system 17 Circulation 18 First line 19 relief storage 20 high-pressure accumulators 21 Second line 22 Third Line 23 Control valve 24 test objects 25 Movement compensation element 26 First Layer 27 Second shift 28 First end area 29 Second end area 30 conveyor unit 31 End area cylinder 32 Camera 33 Arrow 34 Marking symbol 35 clamping element 36 Fastening element 37 Receiving opening 38 Fourth line X First axis Y Second Axis Z Third Axis

Claims

[1] Tear test stand, comprising a carrier (4) for holding a test element (8, 24) consisting of a test material (7), wherein the test material (7) is a laminated material and is formed from at least a first layer (26) and a second layer (27), and with a drive unit (5) for inducing a tear force, wherein the drive unit (5) is connectable to the test element (8, 24) by means of a connecting element (14), wherein in order to induce a highly dynamic tear test, the drive unit (5) is designed in the form of a hydraulic unit comprising a hydraulic device (16), characterized bythat the drive unit (5) has a hydraulically actuated piston (11) which is movably received in a cylinder (10) and is connected to the connecting element (14), wherein a movement compensation element (25) is arranged between the piston (11) and the connecting element (14), wherein the connecting element (14) is secured to the tear test stand (1) by means of a securing element (15). [2] Tear test stand according to claim 1, characterized by that the piston (11) can be actuated by means of a control valve (23). [3] Tear test stand according to claim 1 or 2, characterized by that a camera (32) for visual recording of the tear test is assigned to the tear test stand (1). [4] Tear test stand according to one of the preceding claims, characterized by that the test element (8, 24) has at least one marking symbol (34). [5] Tear test stand according to one of the preceding claims, characterized bythat the drive unit (5) has a closed hydraulic circuit (17).

Images