MATERIAL TESTING application examples
The force and strain ist measured during the defined specimen loading (tension, compression, torsion, bending). From these measures the force-strain-curve and stress-strain-curve are determined and material parameters like Young's Modulus, poisson number, elongation at strain and more complex values are calculated Different measurement systems are used :
The RTSS-Videoextensometer is suited for standardized and automatic test procedures and works as a real time strain sensor..
The Q400-Digital Image Correlation System measures spatially resolved strain values and the analysis is typicylly done in post processing because a large number of informations can be provided.
The importance of material testing
Material testing determines the physical and chemical properties of materials. Material testing can be used to determine the suitability of a material for its intended purpose. Material testing is essential for quality control in many industries, e.g. B. in the automotive, aerospace and construction industries.
Known material tests and material key figures
There are many different types of material testing, such as: Tensile tests, compression tests, hardness tests, fracture toughness tests and fatigue strength tests. Tensile testing is a type of mechanical testing that measures a material's ability to withstand tensile forces. Compression testing measures the ability of a material to withstand compressive forces. Hardness testing is a type of mechanical testing that measures a material's resistance to indentation. Fracture toughness testing is a type of mechanical testing that measures a material's ability to fracture under stress. Fatigue strength testing is a type of mechanical testing that measures the ability of a material to resist fatigue under repeated loading.
Particularly important material parameters: yield strength, modulus of elasticity, Poisson's ratio
Material testing can also be used to determine material parameters such as elastic modulus, Poisson's ratio and yield strength. The modulus of elasticity is a measure of the stiffness of a material. Poisson's ratio is a measure of the compressibility of a material. The yield strength is a measure of a material's resistance to plastic deformation.
Use cases of material testing
Material testing is essential for quality control in many industries, e.g. in the automotive industry, aerospace and construction. Material testing is used to ensure that materials meet the specifications required for their intended use. Materials testing is also used to investigate the cause of material failure. Accurate and reliable measurements are very important in both cases, as life-changing decisions sometimes depend on them.
Full field strain measurement with maximal spatial resolutionThe Istra4D measurement software used in the Q400 DIC system uses a special algorithm to achieve maximum possible spatial resolution. This example shows that the spatial resolution of the strain field is significantly improved by an appropriate image evaluation algorithm. In combination with a high camera resolution, the Q400 system is unsurpassed in terms of spatial resolution. |
RTSS videoextensometer for the determination of Young's Modulus at Tensile testsThe strain sensor RTSS videoextensometer measures with high precision the longitudinal strain during tensile test and transfers the result to the tensile test machine. The image shows the measured stress-strain curve with the calculated Young's modulus. This application example shows how an RTSS camera system can be used as a non-contact strain sensor to determine E-modules on plastics and metals. |
What is the modulus of elasticity or modulus of elasticity?
Young's modulus (also known as Young's modulus) is a measure of a material's ability to deform elastically. In other words: It measures the resistance of a material to mechanical expansion or compression. The higher the elastic modulus, the greater the resistance of the material to deformation.
The elastic modulus can be measured using various methods, including tensile, compressive and shear tests. It is usually expressed in gigapascals (GPa), megapascals (MPa) or newtons per square millimeter (N/mm²). Structural steel or S235JR, for example, has an elastic modulus of 210,000 N/mm².
Tensile test to determine the modulus of elasticity
Tensile testing is the most common method for measuring elasticity.
This type of test involves subjecting a sample of the material to a tensile force. The elongation (tensile stress) that causes this load is measured. The compression test is similar to the tensile test, except that the sample is not subjected to tension but rather to compression (crushing).
Shear testing is another common method for measuring elasticity. In this type of test, a sample of material is subjected to shear forces (forces that act parallel to each other but in opposite directions). The force required to cause deformation is then measured.
Make predictions about material behavior using the modulus of elasticity
Young's modulus can be used to predict the behavior of a material under various loads.
For example, if you know the modulus of elasticity of a material, you can predict how much it will deform (stretch or compress) under a certain load.
Contactless measurement of Longitudinal & Transversal strain at a tensile testThe RTSS Videoextensometer can measure the longitudinal and transversal strain with one camera. The longitudinal strain is measured through the line marker and the specimen width is measured throught the specimen border. It is possible to measure the transversal strain as an average value between the longitudinal marker (--> Posson number) or as a minumum width (necking --> R/N value). The video shows a tensile test with the RTSS system measuring longitudinal and transversal strain. This application example shows the contactless strain masurement at a tensile test by using a RTSS camera system with real-time image analysis. |
Non-contact measurement of very large strains during tensile tests on rubberThe RTSS Videoextensometer strain sensor can measure strains up to 1000% of strain. Due to the high resolution camera a high measurement accuracy is achieved over the whole range. The Video shows the measurement of a rubber specimen with max. 500% strain. The application example shows how real-time measurement of strains of up to 1000% is possible with our robust image analysis methods. |
Measuring the strain distribution during a tensile test on a CFRP sampleThe strain distribution on a CFRP specimen with hole is measured optically with a Q400 DIC ystem. The right image shows the strain after the initial failure state of the specimen. This application example shows the use of the Q400 digital image correlation system at CFRP composite materials. The measured strain field shows invisible microcracks before the component fails. |
Strain measurement on a 3 point bending testTwo polymer plates are glued together and loaded in a 3 point bending test. The surface strain is measured with the Q400 DIC system The images show the horizontal surface strain and the strain along the vertical line 1. The left image gives compression strain (blue) and tension strain (red) as a gradient over the whole specimen. After the failure of the glue the strain distribution is separated for each plate. This application example clearly shows how the strain is distributed on the component surface during a 3-point bending test. |
Non-contact strain measurement using DIC on a micro tensile sampleThe strain distribution on a micro tensile sample is measured using the Q400 DIC system. The initial sample length is 4mm. The measurement is carried out with macro lenses. The displacement resolution of a DIC system depends linearly on the image field and the camera resolution. Example: With 12MPixel cameras, displacements from 100nm (or 10nm) can be resolved at an image field of 40x30mm (or 4x3mm). DIC measurements with image fields smaller than 1mm² can be achieved with the Q400-µDIC system (stereo microscope). This application example shows the ability of the Q400 system to measure the 3D deformation of very small components even with standard makro optics. |
Measurement of the shear strain at a shear testThe Q400 DIC system measures the shear strain and other strain components fullfield. The video shows a shear test with the measured shear strain as color overlay. This application example shows the localization of the strain in the middle of the shear sample. Shear tests are used to assess the shear strength of the material. |
Measurement of crack growth using DIC on a CT sampleQ400 DIC system measures the crack propagation at a CT specimen under tensile load. The video shows the measured major strain together with the recorded force.The diagram gives the crack length versus force. The yellow vectors mark the rapid crack propagation with force reduction. This application example shows the possibility of detecting cracks, locating crack tips and measuring crack opening and crack growth using the Q400 DIC. |