What are the mechanical properties for materials

Material and component characterization

The prerequisite for finding solutions to improve the reliability and service life of materials and components is to record materials in their internal structure. The Fraunhofer IWM examines the reaction of materials and components to mechanical, thermo- and chemomechanical as well as tribological loads and clarifies deformation and failure mechanisms. It records and evaluates the material mechanisms and material parameters in relation to the microstructure and structure-changing processes on all size scales, and it structures material data in a sustainable manner. On this basis, the Fraunhofer IWM conducts material development as well as process and procedural developments.

A particular strength of the Fraunhofer IWM is to develop and apply complex testing, measuring and analysis methods that go beyond standardized procedures. The fundamentals for this are, on the one hand, mechanical testing techniques for a very broad spectrum of temperature, ambient and force ranges, loading speeds and size scales and, on the other hand, expertise in the selection of material and application-oriented methods of characterization and the evaluation of damage developments. The component test takes locally different material properties into account. In addition, fracture mechanical fault assessments and damage analyzes are carried out, multi-axis loading conditions are recorded and evaluated, and local parameters are determined using microscopic testing techniques and structural analysis.

In the range of services, the recording and evaluation of multi-axis loading conditions, the local determination of characteristic values ​​using microscopic testing techniques and structural analysis as well as the expertise in crack propagation, which is used, for example, for the development of innovative separation processes, are to be emphasized. The portfolio is supplemented by various high-resolution residual stress analysis techniques and thermophysical and thermomechanical characterization.


Cooperation with the Fraunhofer IWM

Measurement and analysis options

 

Fraunhofer IWM works with the most modern equipment available on the market and develops specific test equipment and test setups for individual customer inquiries.
The scientists determine a large number of material and component properties using a wide variety of measurement and analysis methods.

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Static, cyclical and dynamic sudden material and component characterization

 

  • Measurement of strain rate dependencies on high-speed tensile machines (100 kN to 20 m / s, 500 kN to 10 m / s), drop weight testers and impact test stands
  • Static strength, multiaxial parameters, fatigue strength, fracture toughness, crack propagation, torsional strength with servohydraulic, electrodynamic and electromechanical testing machines:
    • Tension, pressure, shear
    • Test forces from 10 mN to 8 MN
    • Test chambers from 100 to 2500 K.
    • 2D and 3D strain measurement via gray value correlation (ARAMIS)
    • Force-controlled and strain-controlled experimentation
    • One-step tests, variable amplitude tests
    • Various methods of crack length measurement, including ASTM 1820, ASTM 1921, ASTM 647
  • Fretting fatigue with a module for the combined application of controlled longitudinal and transverse forces
  • Evaluation of the component strength on a clamping field with servo-hydraulic (63 kN and 25 kN) cylinders and torsion cylinders up to 4 kNm
  • E-module, storage module and loss module via dynamic mechanical analysis (18 mN to 500 N)
  • Natural frequencies, modal analysis, vibration tests and shock tests with an air-conditioned shaker system:
    • Sinus force approx. 10 kN, noise force approx. 10 kN, frequency up to 4000 Hz
    • Max. Vibration speed (sine) 1.8 m / s (depending on test mass), vibration path approx. 51 mm
    • Max. Acceleration for sine / noise 100 g / 40 g (depending on test mass)
  • Strain field analysis through image correlation
  • Damage development through thermography and further data correlations and analyzes
  • Evaluation of the creep behavior on temperature-controlled and air-conditioned test benches

 

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Thermomechanical material and component characterization

 

Determination of fatigue life, yield point, tensile strength, modulus of elasticity and crack propagation with mechanical or servo-hydraulic testing machines:

  • From -180 ° C to> 1000 ° C
  • Isothermal or anisothermal (heating and cooling rates up to approx. 10 ° C / s)
  • Inductive heating or in an oven
  • Strain or tension controlled
  • Typically cylindrical samples 5-10 mm in diameter
  • Hot tensile tests to determine the yield point at e.g. 0.2% plastic elongation
  • Modulus of elasticity with the resonance method via adaptation to the stress-strain curve in the linear range
  • Fatigue crack growth typically corner crack specimen with a cross section of 8x8 mm in the measuring area

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Micromechanical material and component characterization

 

  • Determination of modulus of elasticity, fatigue strength and natural sample frequency with micro-tensile apparatus:
    • From room temperature to 200 ° C
    • Micro samples from our own production with customer material, sample thicknesses 10 to 400 µm, base material may be thicker
    • Test frequency 1200 Hz
  • Characterizations with a resonant micro-fatigue test bench:
    • Test frequency 1200 Hz through defined sample natural frequency / geometry, which can be adjusted
    • Measurement of the natural frequency of the specimen, which changes with the progress of fatigue, detection of the first damage well before crack initiation
  • Measurement of position, displacement and strain with cameras, microscopes and scanning electron microscopes:
    • Optical strain measurement with digital image correlation for samples with a characteristic surface (features in the form of gray value transitions)
  • Dynamic micro-testing over five orders of magnitude of the strain rate with local strain measurement through image correlation and high-speed video

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Thermophysical material properties

 

  • Determination of specific heat capacity and quantitative determination of exothermic and endothermic reactions with the dynamic differential calorimeter DSC:
    • From room temperature to 1600 ° C with heating rates between 0.01 and 50 K / min
    • Determination of transition temperatures
    • Quantitative determination of exothermic and endothermic reactions
    • Measurements in different gas atmospheres and in a vacuum
    • Typical sample size of solids 5 x 1.2 mm
  • Measurement of thermal changes in length and coefficients of linear expansion, phase changes and transformation temperatures as well as temperature-dependent change in density with a thermomechanical analyzer:
    • From room temperature to 1600 ° C with heating rates between 0.1 and 20 K / min
    • Measurements in different gas atmospheres and in a vacuum
    • Typical sample size: diameter 3-6 mm with a length of 10-25 mm, similar dimensions for metal sheets
  • Analysis of thermal diffusivity with laser flash apparatus LFA:
    • In the range 0.01-1000 mm2 / s and from room temperature to 2000 ° C with heating rates between 0.1-50 K / min
    • Measurements in different gas atmospheres and in a vacuum
    • Specimen dimensions for round specimens 6, 10 and 12.7 mm in diameter, square specimens max. 10 x 10 mm
    • Sample thickness depending on the expected thermal diffusivity