Multiaxial Universal Testing Machine

Abstract

The invention concerns a multiaxial universal testing machine, which allows evaluating the mechanical behaviour and performance of materials with planar structures, such as fabrics, composites and laminates. The machine comprises 4 horizontal axes at 45°, with 8 gripping jaws displaceable along slide rails and moved by the action of 8 independent motors. The connection between a gripping jaw and its respective motor is assured by a linear actuator. The test specimen is fixed by the gripping jaws and can be subject to tensile, compression and fatigue testing, making possible the analysis of the materials behaviour under simultaneous multi-directional loads.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from a reading of the following detailed description in conjunction with the accompanying drawings wherein:

FIG. 1 is an upper view of the testing machine.

FIG. 2 is a side view of the testing machine.

FIG. 3 is an exploited view from an “arm” of the testing machine. This image only shows one “arm” because the others have the same structure.

DETAILED DESCRIPTION

The testing machine shown in the drawings was designed to carry out a very wide range of different kinds of testing operators, such as for example tensile, compression or fatigue, on materials with planar structures, such as fabrics, composites and laminates.

Referring now to FIG. 1 of the drawings, there is shown a global upper view of the testing machine, where is evident the octagonal shape of the central block 7, due to the 8 mid-axis of the system, decreasing the encumbrance and making easier the operator access. This central block is the main support of the machine and where the flanges 2 are attached. The flanges 2 were designed to decrease the amount of material used in its construction and to make easier the access to the central area to placement of the test specimen.

FIG. 2 is a side view of the testing machine, showing another view of the central block 7, which is supported by 4 anti-vibration mounts 10 to regulate the machine levelling and to stabilize the central block 7. To attach the mounts 10 to the central block 7 are used angle steel 9 with standard dimensions.

Referring to FIG. 3 it is possible to see an exploited view of one “arm” allowing a detailed observation of all components of the “arm”. Each flange 2 functions as the basis of each “arm”, supporting its components. An “arm” is composed firstly by a geared motor 1 to allow the necessary torque at low rotations. The connection between the geared motor 1 and the screw type linear drive 3 is done by spindles joint 8, selected considering the diameter and the maximum torque supported by the screw type linear drive. The screw type linear drive 3 is a mechanism to transform a rotational movement (from the motor) in a linear displacement (to the gripping jaw), so the displacement sense of the gripping jaw only depends of the sense rotation of the motor. The screw type linear drive 3 was chose to get an axial alignment with the applied force, eliminating flectional moments. Its connection to the flange 2 is done by 2 supports 12, with the height necessary to keep the spindles alignment. On the other end of the screw type linear drive 3 it was placed an articulation head 13 linked to a clevis 15 by a stud 14. This set is used to minimize the negatives consequences of possible horizontal misalignments. The clevis 15 is prepared to connect to the load cell 4, which is the responsible to convert the force value applied to test specimen in an electric value in order to be acquired and processed by the control system. To finish the “arm” constitution only remain to refer the gripping jaw 6, linked to the load cell 4 by an element 16 designed to fit correctly in the joined elements. The gripping jaw 6 is manually screwed and the mordant of the gripping jaw can be replaced by others with different shapes and different test specimen contact surfaces, specifically to the test specimen material. Independently the mordant, it must guarantee the friction with the test specimen, proportional to the screw force, impeding any slipping. The gripping jaw 6 seats on a piece 17 designed to attach correctly the gripping jaw 6 to a non lubricated slide carriage 11, which moves on a slide rail 5. This set, composed by the slide carriage 11 and the slide rail 5, forms the guidance of the gripping jaw 6, driving it according to the “arm” direction.

As referred, all “arms” are independent from each other, what means that only work the necessary “arms” to the desired kind of assay. The placement of the test specimen is done by holding its extremities in the gripping jaw mordents. Obviously the test specimen shape must be defined according to the kind of assay to perform.

All the assay configurations depend practically on the design of the control software, because the designed physical structure allows total freedom at this point.

Claims

1. A multiaxial universal testing machine capable to evaluate some behaviour parameters, like tensile, compression or fatigue, in different directions simultaneously of materials with planar structures having a central block 7, working as a supporting structure, where the platforms 2 are rigidly attached in a radial orientation, in which the arms are seated, designed to apply a required force and displacement to each gripping jaw, where the test specimen is attached.

2. A multiaxial universal testing machine according to claim 1 each arm is made up of an electric motor with speed reducer, coupled to a screw type linear drive, in series with a load cell and a gripping jaw.

3. A multiaxial universal testing machine according to claim 2 the rotational movement of the geared motor is converted into linear displacement and force by the screw type linear drive, monitoring and controlling this parameters with a rotary encoder in the motor (to the displacement) and a load cell, between the screw type linear drive and the gripping jaw (to the force), respectively.

4. A multiaxial universal testing machine according to claim 3, each gripping jaw seats on a slide carriage that can travel along a linear dry bearing, responsible for the correct alignment of the test specimen displacement.

5. A multiaxial universal testing machine according to claim 1, the multiaxial universal testing machine can be composed by 1, 2, 4, 6, 8, 10, 12, 14, 16, 18 or 20 axis, keeping all the capabilities needed to evaluate the mechanical behaviour and performance of materials with planar structures.

6. A multiaxial universal testing machine according to claim 5 and the kind of assay, the test specimen shape must be associated to the number of activated axis.

7. A method for applying a multiaxial load to a test specimen comprising the steps of: Enclosing the test specimen inside the central area circumscripted by all the gripping jaws and reserved to the placement of the test specimen;Attaching the test specimen to the gripping jaws involved in the assay to perform, according to the desired orientation;Applying force to the test specimen through the displacement of the gripping jaws and following the configuration parameters defined to the test performance, including the kind of assay and the active axis.