Tensile grips are used to clamp specimens in test applications where the test equipment and controller are set up to apply force in the tensile direction. Tensile specimens vary and so do tensile grips; these grips come in different designs and sizes, and can be ordered in different force capacities. This post discusses compact tension grips when the test space or the tensile specimen is too small for the larger tensile grip designs.
Tensile Test Setup
Common tension testing setups include a universal testing machine equipped with the following components:
A load cell that is able to record data is used with the tensile testing system and connected to the data acquisition indicator or controller. The capacity of the load cell should not exceed the maximum force of the machine frame or the expected maximum forces in testing.
The selection of the controller depends on the test application and the expected test results. Common measurements from tensile tests include ultimate tensile strength, strain, yield strength, Young’s modulus, and more.
Depending on the controller, software may be optional. ADMET offers controllers with keypads and displays that allow use without the need for software. Nevertheless, many users find material testing software useful as it allows exporting data and results to spreadsheet programs, viewing graphs, live data, and more.
Tensile grips are used to clamp tensile specimens. Materials tested in tension vary; from plastics to biomaterials, metals, textiles, films, ceramics, electronics, and more. Once the test specimen is cut and prepared, it is inserted into the grips and positioned symmetrically and in alignment with the direction of testing. Tensile grips should be able to hold the specimen without slippage as it elongates and reaches its maximum force or failure point.
If strain measurements are needed and measurements from the extensometer are preferred over crosshead displacement data, an axial extensometer will be added to the tensile test setup. Axial extensometers are selected based on specimen gauge length and the travel range.
If the test application requires specific environmental conditions, the testing frame may be equipped with an environmental chamber. ADMET environmental chambers come with slide rack rails that allow the chamber to be pulled out of the machine when not in use. The high and low temperature settings, dimensions of the chamber, and the fixturing inside the chamber all need to be discussed with your ADMET Account Director.
There are many types of grips and fixtures available for tension testing. Different materials require different fixturing to properly hold them. For instance, a sample made of metal requires different grips than a stretchy piece of rubber due to how the materials behave as tensile forces are applied. Selecting the correct grips for your application is crucial in achieving accurate results.
Compact Tensile Grips
Compact tensile grips are required for small specimen testing or in test spaces where the vertical or horizontal space is limited.
Compact Manual Vise Grips
GV-100NT grips are low-weight (60 grams per grip) 100N capacity manual vise grips. They are ideal for use in small test spaces as they only measure 47mm (1.85in) in length and 25mm (0.98in) in width. The manual vise grips come with different jaw surface options (steel, rubber-coated, serrated, diamond-coated) and with different clamping surfaces based on the dimensions and the material of your samples.
Inserting small specimens in the tensile grip jaws can be challenging. For such scenarios, ADMET offers the GV-1AT and the GV-5AT (1kN and 5kN capacity, respectively) manual vise grips with extra space to hold the specimen edges while inserting it in between the jaws.
Pinching or pincer grips are small tensile grips that mimic the ergonomics of the human hand holding an object between the thumb and the index finger. ADMET pinching grips come with threaded or eye end adapters and can also be chain mounted for flexible positioning. These grips are commonly used with the tensile testing of electronics, biomaterials, and more.
Thread head grips are used with screws, threaded studs, and bolts. A thread head grip is built with an insert holder and a threaded insert. The thread size is based on the thread size of the specimen. This narrow design allows thread head grips to fit into small test spaces even if their rated force capacity is high. Thread head grips are used to test specimens per ASTM E8, ASTM F519, and more.
Standard fatigue grips are large grips that are not compatible with small specimens. ADMET small specimen fatigue grips are designed with an alignment fixture and removable alignment fingers to ensure the specimen is vertically aligned with the plane of the grip faces. These grips are also commonly used in environmental chambers at high/low temperatures.
eXpert 8600 Axial-Torsion Testing System with Small-Specimen Fatigue Grips in Environmental Chamber
Other types of compact tensile grips include clevis grips, thread grips, compact pneumatic vise grips, and others. In order to determine the best suited grips for your tests, please let our Sales Engineers know the maximum force capacities needed to test your samples, the sample material, dimensions, shapes, and elongation properties. We will then discuss the options with you, and, if needed, can test your samples here to choose the right grips for your testing.