Device for testing samples under cryogenic conditions

Abstract

The device for testing samples under cryogenic conditions comprises a first and second fasteners (1, 2) for holding a sample (3) at two opposite ends, and a container (4) positioned around the sample (3), the container (4) being connected to a tank (5) of cryogenic fluid. It allows to provide a device for testing samples under cryogenic conditions that is as simple as possible and that minimizes the assembly time required in performing the tests and increases flexibility in implementing new sample geometries by reducing the space restriction involved in using a traditional cryostat.

Description

[0001] CRYOGENIC SAMPLE TESTING DEVICE

[0002] DESCRIPTION

[0003] Object of the invention

[0004] The present invention relates to a device for testing samples under cryogenic conditions, in particular, for performing a test where a uniaxial tensile or compressive force is applied to a test sample.

[0005] Background of the invention

[0006] In the field of materials research and development, the evaluation of mechanical properties at cryogenic temperatures is of utmost importance.

[0007] One of the fundamental tests is uniaxial load testing on samples defined according to international testing standards (ISO, EN, ASTM, etc.). These tests allow the identification of the material's own mechanical parameters at the temperature at which the experimental test is performed. Performing such tests presents several significant technical challenges.

[0008] First, cryogenic temperatures present challenges in terms of test device design. Materials can, for example, become more brittle or increase their load resistance, and mechanical properties can vary considerably compared to room temperature conditions. This requires the creation of a controlled environment that maintains the sample temperature at a constant, homogeneous, precise, and stable temperature throughout the test.

[0009] To introduce this uniaxial load to the sample, a robust clamping system is required to secure the sample to the equipment applying the stress, typically a hydraulic or electromechanical actuator mounted on a Universal Testing Machine. To increase flexibility and reduce setup time, these clamping elements are often hydraulic or mechanical clamps. These clamps allow mechanical stresses to be introduced by applying pressure to the side walls at the ends of the sample and transferring the load through friction. In some cases, to avoid damaging these areas of the sample, heels are installed to increase the sample's cross-section and protect its surface from damage by the clamp's pressure.

[0010] Another option is to fix the sample to the loading actuator using a bolted joint glued to a fixture that is attached to the universal testing machine.

[0011] Sometimes, the sample is installed in a fixture that restricts some of its degrees of freedom and guides the applied force to ensure that it is loaded appropriately to identify the desired mechanical parameter.

[0012] To contain the cryogenic liquid, it is customary to use a cryostat or container with thermal insulation around its perimeter, which reduces thermal losses and prevents leaks of the cryogenic liquid.

[0013] To ensure sample conditioning at the target temperature, it is common to immerse both the sample and the test equipment in a cryogenic liquid, such as liquid nitrogen, while insulating the universal testing machine outside. This cryogenic bath must cool both the sample and the fixture and guide equipment, which are generally massive and require time to reach a homogeneous and constant temperature.

[0014] The use of a cryostat creates operational problems by restricting the space available for the test. A larger cryostat reduces the space constraints but increases thermal losses. The greater the load the test equipment can withstand, the more material it requires, and therefore, the heavier it is, increasing the time required to reach a stable and homogeneous temperature.

[0015] Description of the invention Therefore, an objective of the present invention is to provide a device for testing samples under cryogenic conditions that is as simple as possible and that minimizes the assembly time required to carry out the tests and increases the flexibility in the implementation of new sample geometries by reducing the space restriction that the use of a traditional cryostat implies.

[0016] With the device for testing samples under cryogenic conditions of the invention, the aforementioned drawbacks are resolved, presenting other advantages that will be described below.

[0017] The device for testing samples under cryogenic conditions according to the present invention is described in claim 1, and the dependent claims include additional features that are optional.

[0018] In particular, the device for testing samples under cryogenic conditions comprises first and second holders for holding a sample at two opposite ends and a container located around the sample, the container being connected to a tank of cryogenic fluid.

[0019] Thanks to this feature, only the sample is subjected to cryogenic conditions, without the need for a cryogenic fluid tank in which the entire test device is placed.

[0020] This allows for easy and flexible setup, rapid sample installation, and rapid cooling by cooling only the central part of the sample and not the rest of the test equipment.

[0021] Because there are no space restrictions, the test can be performed with the same experimental tools and equipment used at standard temperatures, with reduced setup time, and allowing rapid change of test samples without the need to remove the test equipment from the cryostat.

[0022] Furthermore, preferably between at least one holder and the sample, at least one thermal insulation plate is placed, which partially prevents heat transfer between the sample and the holder. This insulation plate or plates can be located inside or outside the container.

[0023] Advantageously, the container comprises an opening for the entry of the cryogenic fluid from the tank and the expulsion of the gas generated in the evaporation of the cryogenic fluid.

[0024] Furthermore, advantageously at least one of the first or second fasteners may be located at least partially outside the container, preferably the first and second fasteners are located at least partially outside the container.

[0025] In this way, conventional restraints can be used, not necessarily adapted for use in cryogenic conditions.

[0026] Preferably, the container is formed from a flexible sheet that can be deformed.

[0027] According to a preferred embodiment, the container is connected to the cryogenic fluid tank by a filling conduit.

[0028] Furthermore, the first and second fasteners are preferably clamps.

[0029] Brief description of the drawings

[0030] For a better understanding of what has been explained, some drawings are attached which, schematically and only as a non-limiting example, represent a practical case of implementation.

[0031] Figure 1 is a schematic front elevation view of the device for testing samples under cryogenic conditions according to the present invention.

[0032] Description of a preferred embodiment Figure 1 shows the device for testing samples under cryogenic conditions, in particular, for carrying out a tensile strength test on sheet-shaped samples, comprising two holders, identified as the first and second holders (1, 2), arranged at opposite ends of a sample (3).

[0033] These fasteners (1, 2), which are preferably clamps, are designed to firmly hold the sample (3) by friction and provide stable support during the test.

[0034] Between at least one support (1, 2) and the sample (3) thermal insulation plates (8) are installed that partially prevent thermal transfer between the sample (3) and the support (1, 2).

[0035] Furthermore, the test device according to the present invention also comprises a flexible and deformable container (4), or bag, surrounding the sample (3), which is connected to a tank (5) of cryogenic fluid.

[0036] The presence of the vessel (4) ensures that the cryogenic fluid surrounds the sample and that there are no leaks of cryogenic fluid. It should be noted that the insulation plates (8) can be located inside or outside the vessel (4).

[0037] One of the characteristics of this container (4) is that it can be deformed according to the pressure of the clamp (1, 2) ensuring that it is well fixed to the sample (3), without tearing or perforating to maintain the tightness of the container (4).

[0038] Furthermore, the vessel (4) is equipped with an opening (6) to allow the entry of cryogenic fluid from the tank (5), for example, via a filling conduit (7). This configuration facilitates the continuous flow of the cryogenic fluid and ensures a uniform distribution around the sample.

[0039] This opening (6) also allows the expulsion of the gas generated during evaporation of the cryogenic fluid. The opening (6) is located at one end of the container (4), at the upper end according to the embodiment shown in Figure 1, to allow the removal of the cryogenic fluid after carrying out the test.

[0040] Advantageously, at least one of the fasteners (1, 2), preferably both fasteners (1, 2) is located, at least partially, outside the container (4), allowing the use of conventional fasteners without having to be particularly suitable for use in cryogenic conditions.

[0041] The container (4) can be made from a variety of materials, but is preferably made from a flexible sheet that deforms under the pressure of the fastener (1, 2), but is not perforated to maintain the tightness of the cryogenic fluid, which allows it to deform according to the pressure applied by the fasteners (1, 2).

[0042] The operation of the test device according to the present invention is very simple, since the container (4) must simply be placed around the sample (3) to be tested.

[0043] The sample (3) is then held in place by the clamps (1, 2), and the cryogenic fluid is fed into the container (4) from the tank (5) through the filling duct (7) and the opening (6) of the container (4).

[0044] When the central part of the sample (3) is at the desired temperature, the desired uniaxial mechanical test can be performed, for example, a tensile strength test of the sample (3).

[0045] Although reference has been made to a specific embodiment of the invention, it is evident to a person skilled in the art that the device for testing samples under cryogenic conditions described is susceptible to numerous variations and modifications, and that all the details mentioned can be replaced by other technically equivalent ones, without departing from the scope of protection defined by the appended claims.

Claims

CLAIMS 1. A device for testing samples under cryogenic conditions, comprising first and second holders (1, 2) for holding a sample (3) at two opposite ends; characterized in that it also comprises a container (4) located around the sample (3), the container (4) being connected to a tank (5) of cryogenic fluid.

2. Device for testing samples under cryogenic conditions according to claim 1, wherein at least one insulation plate (8) is placed between at least one holder (1, 2) and the sample (3).

3. Device for testing samples under cryogenic conditions according to claim 1 or 2, wherein the container (4) comprises an opening (6) for the entry of the cryogenic fluid from the tank (5).

4. Device for testing samples under cryogenic conditions according to any one of the preceding claims, wherein at least one of the first or second holders (1, 2) is located, at least partially, outside the container (4).

5. Device for testing samples under cryogenic conditions according to any one of the preceding claims, wherein the first and second holders (1, 2) are located, at least partially, outside the container (4).

6. Device for testing samples under cryogenic conditions according to any one of the preceding claims, wherein the container (4) is formed from a flexible sheet.

7. Device for testing samples under cryogenic conditions according to any one of the preceding claims, wherein the container (4) is connected to the cryogenic fluid tank (5) by means of a filling conduit (7).

8. Device for testing samples under cryogenic conditions according to any one of the preceding claims, wherein the first and second fasteners (1, 2) are clamps.

Images