Overview Structural Durability

Safety, reliability and profitability are core criteria for development and commercialization of products and their components. We offer support in issues regarding static and cyclic durability (lifetime) of materials, sub-assemblies and machine parts up to components and entire structures. Apart from measurements of representative service loads on com-ponents, also simulations of measured or given stress histories in a broad load range may be performed in the lab. Two universal floor slabs allow the realization of tailored test set-ups in order to experimentally determine the lifetime of test objects under realistic and customer specific loads.


As an independent, accredited laboratory for oscillating mechanical testing of materials, components and constructions according to ISO/IEC 17025 (STS 0053), a high quality lev-el of our services as well as extensive documentation are a matter of course.


Contact:    Dipl. Ing. ETH Roland Koller, Stv. Dipl. Ing. FH Alex Stutz

 

Our services - Consulting, planning and engineering
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For clarification of issues referring to static and/or fatigue strength of components we support you by inquiries and ap-plication of Swiss and/or European standards. We provide ad-vice regarding strain measurements, performing static and/or fatigue tests as well as design or manufacturing actions to avoid fatigue cracks and/or to increase the lifetime of components.
Measurement and evaluation of service loads
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The design of components and its mathematical or experi-mental strength analysis requires knowledge of affecting service loads. Considering operating time, service modes and conditions, we also support you in the definition of relevant strain components and the definition of measuring points as well as the evaluation of measuring signals. For data acquisition, there are battery-supplied, mobile devices available (up to 40 channels with sampling frequencies up to 2'400 Hz) for long and short-term measurements in the field as well as in the laboratory. We evaluate recorded load histories with re-spect to fatigue relevant, statistical properties and preprocess those for service load simulations on fatigue test facilities if required
Customer specific test setups
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For experimental strength verifications, we load your compo-nents or entire structures statically or oscillating. If required, we monitor loads, strain and deformation up to indication of unacceptable deformations or cracks or until complete failure respectively. At the same time, we realize tailored test setups adjusted to test components with regard to customer specific requirements. Two universal floor slabs (platen area: 4 x 8 m and 4.5 x 8 m respectively, heights: 10 m and 4 m respectively) and modular construction elements are available for such set-ups. Static and oscillating loads include tensile and compres-sion forces (up to 100 kN), flexural loads (3-point, 4-point bending) as well as torsional loads and its combinations.
Experimental investigation of fatigue properties on specimens
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For the mechanical characterization of metallic materials (steel, aluminum, magnesium, copper etc.), we give advice regarding sample geometry, type of loading and test strategies with re-gard to your requirements. We therefore define test series (stress or strain controlled) for the determination of SN-curves in the range of limited lifetime and/or stair case tests to de-termine the material fatigue strength with specified probability of survival. Tests on material samples may be carried out at temperatures between 50°C and 450°C.
Numerical strength verification
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Apart from FEM-stress analysis, a lifetime estimation carried out at an early stage also contributes to crucial cost savings of development and design of components and structures subjected to oscillating loads. We support you in modelling your components to investigate relevant stress components as well as in using the latest FKM-guideline for the numerical verification of the static or fatigue strength.
Research and development projects - Shortened experimental method for determination of fatigue properties
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Bainitic steels are used increasingly in the automotive industry. As for a reliable design of components, the strength capacity hasn't yet been fully exploited, improved steels, which show the so-called TRIP-effect (TRansformation Induced Plas-ticity), have been developed.


The investigation of mechanical fatigue properties in the course of material development processes by using standard fatigue tests is time consuming, costly and therefore, not economical. Based on modern models, a shortened, experimental method has been introduced and verified in the frame of a re-search and development project. This method enables the es-timation of a complete SN-curve (limited life time and fatigue strength) carrying out three to five fatigue tests.


Contact: Dipl. Ing. ETH R. Koller, Dipl. Ing. FH A. Stutz

Application of pre-stressed carbon fiber laminates for enhancing the lifetime of an artwork pendulum
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An artwork pendulum was manufactured from three steel box girders which were connected with hexagon head screws. After about two years of operation, some screw heads have broken. As a repair solution the two girder joints were welded and all screws replaced. At the same time computational analyses were carried out to proof the fatigue strength of the screw connections as well as of the new welding. The results showed that neither the screw connections nor the new welding exhibit the necessary fatigue strength. Consequently, an alternative reinforcement of the pendulum was necessary to keep the artwork in service. The application of pre-stressed carbon fiber laminates shift the mean stress of the welding into the com-pression range. This restrains the opening of welding defects and micro cracks, whereby a possible crack growth will be re-duced and the lifetime of the pendulum will increase. The strengthened pendulum has been working successfully for more than 13 years without any indication of fatigue cracks (see Paper "CFRP-Strengthening and Long-Term Performance of Fatigue Critical Welds of a Steel Box Girder", R. Koller et al., Polymers 2014).

 

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Infrastructure
  • Servo-hydraulic tension-compression fatigue test machines and test cylinders
    Nominal load range from 10 kN to 1'000 kN
    Frequency range from 0.1 to 50 Hz
  • Servo-hydraulic tension-compression-torsion fatigue test machine
    Nominal load up to 160 kN
    Nominal torsion up to 1'000 Nm
    Frequency range from 0.1 to 20 Hz
  • Electro-mechanical tension-compression fatigue test machines
    Nominal load range from 5 kN to 150 kN
    Frequency range from 50 to 200 Hz
  • Pulsators
    Nominal load range from 300 kN to 1'000 kN
    Frequency load from 1 to 10 Hz
  • Pneumatic tension-compression test cylinders
    Nominal load range from 0.4 kN to 12'000 kN
    Frequency range from 0.5 to 5 Hz
  • Two universal floor slabs for customer specific test setups
    Platen area l x w: 8 x 4 m, 8 x 4.5 m respectively
    Height: 10 m, 4 m respectively
    Max load per mounting point: 100 kN, 50 kN respectively
  • Data acquisition systems for laboratory or field operation
    Max. number of channels: 40
    Measuring signals: force, displacement, strain, acceleration, temperature
    Sampling frequency up to 2'400 Hz per channel
  • Temperature chambers
    Size of test room w x h x d: 110 x 135 x 290 mm, 440 x 550 x 460 mm respectively
    Temperature range from 50°C to 450°C, -100°C to 250°C respectively