Everything you always wanted to ask us
General questions about the procedure
The result is a flow curve. From this flow curve,
- RIp0,2 comparative yield strength to tensile test is determined
- RIp0,2 Comparative tensile strength to tensile test determined
- AI ductility of your material
Note: AI is consistent with elongation at break for some materials. Talk to us about this.
It is a software algorithm that uses the three-dimensional shape of a hardness impression to calculate material characteristics using FEM simulations.
The test impression is generated mechanically by a test specimen, the evaluation is done optically by an interferometer and the calculation is done digitally by an algorithm.
Both representations are possible in the user interface.
Currently, these statements can only be made qualitatively.
The transfer of results of a test point to the total sample is basically the responsibility of the examiner / user. With the large number of materials considered, this is fundamentally a valid consideration.
The following points should be noted:
- If the sample has a gradient in the material properties (eg due to surface hardening of steel), the overall behavior results from the entirety of the local material properties.
- Limitations exist with aluminum, where brittle fractures of the material occur. Actual compliance in terms of tensile strength can not be guaranteed in all cases. A transfer to a compressive strength, however, already. Here it depends on what actual load the component undergoes.
- Texture / anisotropy: Here an average of the direction-dependent properties is determined.
Questions about the benefits and advantages
- Fast and non-destructive quality assurance and product optimization.
- Optimization of processes and heat treatments.
- In-process measurement to reduce rejects and adhesion.
The method was specified within a DIN SPEC 4864 with the Federal Institute for Materials Testing (BAM Berlin), the Physico-Technical Federal Institute (PTB, Braunschweig), the Materials Testing Office NRW (MPA Dortmund), DIN and numerous industrial partners.
Compared to the tensile test:
- destructive arm
- Local test
- Component test, 100% test and in-process test with automated sample preparation possible
Compared to the hardness test
- No revaluation necessary
- ExpressiveRobuster (due to lower statistics and range of results)
The internal test can be compared to the tensile test
- Time in the operational processes
- Space and space requirements of conventional testing technology
- Test costs
Questions about the procedure
The method is divided into the following steps:
- 3D measurement of the test impression
- Solution by software algorithm with FEM simulation
Optimized by an optimization algorithm FEM simulations to the real test impression. The material characteristics and flow curves are taken from the best match simulation.
Is the force-indentation depth curve taken into account when determining the mechanical characteristics?
Yes! - Both the material throw and the depressed area are measured.
That depends on the load level and the material being tested. Typical penetration depths are between 10 and 300μm.
- In the standard case, which also corresponds to the procedure of DIN SPEC 4684 (published June 2019), we assume isotropic (direction-independent) material behavior and von-Mises plasticity.
- There are boundary conditions (sample thickness, sample storage) which are modified in special cases (for example, thin samples).
- However, in principle, the assumptions for the FEM simulation can be made free and adapted.
Measuring grids and cascades can be checked automatically
True tension-elongation Gradients can be transferred by CSV files in FEM simulations (output of x-y coordinates of the grid are possible)
Questions about possible materials, necessary geometries and the sample preparation
- In principle, all metallic materials can be tested with our impression method.
- For expected accuracies of individual materials and material groups, we refer to the "Materials" section.
- The ratio of penetration depth to sample thickness must be less than 0.1 for the standard boundary conditions.
- The component height should not exceed about 350 mm.
- Upper and lower surfaces must be plane-parallel.
- The inclination of both sides must not exceed 2% in order to guarantee optimum results.
- The maximum roughness depends on the penetration depth.
If evenness and roughness are insufficient due to process or specimen, the following variants of sample preparation are possible:
- fine milling
- wire EDM
- Wet Abrasive
Heating of the sample surface is to be excluded.
That depends on the size of the measuring points and thus on the load level and the strength of the material. Usually, 200-300μm minimum distance can be realized. If points can be measured in the offset, smaller measuring point distances are possible.
Our customers are active in the automotive, aerospace, heat treatment, mechanical engineering and other industries.
Yes! - Texture and anisotropy are to be considered and have influence on the results.
The distance to the edge must be 3x the indentation diameter. The distance between two impressions should be twice the indentation diameter.
Smaller distances are possible, but should be checked using the specific example.
The lower the test load, the more likely it is that local factors such as particle size play a role. The dispersion of the measured values typically increases. For forces above 300N, however, these are negligible with a few exceptions.
Questions about verification
We carry out comparative measurements on tensile specimens.
- The software is supplied with a material-optimized material model in this respect.
- Verification work on new materials is carried out continuously.
Please contact us about this topic.
The material maps serve to improve the comparability of the characteristic values Rp0,2 and Rm for the tensile test. Furthermore, this can often also produce a quantitative relationship to the elongation at break from the tensile test. To create the material cards we need results of tensile tests in the form of stress-strain curves. For an alloy of several strength levels, this material card can be created.
Questions about the company
Both as well: We develop, produce and distribute our testing machines ourselves and in cooperation. We carry out component tests, detailed analyzes, damage analyzes and wage measurements.
Talk to us about this.
Questions about the machine
The test room is dependent on the selected model and can be adjusted if required. So you can find the optimal size, regardless of whether you are testing flat samples or large castings.