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Fatigue testing under elevated temperatures

Fatigue lives change significantly with higher temperatures. HBK has a range of appliances to test temperatures from –50°C to +1000°C. And we provide all the properties for isothermal and Chaboche analysis to deliver accurate fatigue life estimates.  

Fatigue of joints and fixtures

Whether you are welding or fastening materials together, HBK offers a range of models to estimate the fatigue life of complex joints. We test, measure, and derive all the parameters you need to obtain accurate fatigue life estimates.

Novel and advanced materials

Working alongside academic institutions and commercial enterprises, HBK helps to provide mathematical models, experimental design, and characterization analysis for fatigue. Our experience includes different forms of advanced engineering composites. 

Bespoke testing

Not all tests are covered by standards. HBK is renowned for developing bespoke tests for all sorts of applications, for example, extracting tiny specimens from cast components or performing tests on torsional fatigue of shafts at elevated temperatures. 

Fracture mechanics

Fatigue failure is a two-stage process combining crack initiation and growth to failure. HBK offers a range of crack growth models as well as turnkey testing and characterization services that enable you to accurately estimate crack growth.

What is Material Fatigue?

Material fatigue is the process where a material experiences progressive damage under repeated cyclic loading, even if the stress levels are below its static strength. Here’s a concise overview:

 

  • Initiation: Microscopic cracks form at stress concentrations like surface defects or grain boundaries.
  • Crack Propagation: These cracks grow incrementally with each loading cycle.
  • Critical Crack Size: The crack reaches a size where the material can no longer support the load, leading to sudden failure.
  • Influencing Factors: Factors such as material microstructure, surface finish, environmental conditions, and loading nature affect fatigue life.
  • Fatigue Testing: Tests are conducted to predict fatigue life by subjecting specimens to controlled cyclic loading.

What Causes Fatigue in Materials?

Material fatigue is caused by several factors, primarily related to cyclic loading. Here are the main causes of fatigue failure of materials:
 

  • Cyclic Stress: Repeated loading and unloading cycles, even at stress levels below the material’s static strength, can initiate and propagate cracks over time.
  • Stress Concentrations: Areas with geometric discontinuities like holes, notches, or sharp corners where stress is concentrated.
  • Surface Quality: Rough surfaces or surface defects can act as initiation points for cracks.
  • Environmental Conditions: Factors such as temperature variations, corrosion, and oxidation can accelerate fatigue damage.
  • Material Properties: The microstructure, grain size, and presence of internal defects within the material influence its fatigue resistance.
  • Residual Stresses: Stresses remaining in the material after manufacturing processes like welding or machining can contribute to fatigue.

HBK Advanced Materials Characterization & Test facility (AMCT)

Whether it's higher performance, lower weight, or an optimized manufacturing process, increasing product efficiency or durability starts with the selection of the appropriate materials.

From design data for FEA fatigue analysis to consistent material quality assurance, the HBK Advanced Materials Characterization & Test facility (AMCT) offers a large variety of services to assess these parameters and increase confidence in your design.

The choice of material plays a vital role across many industries, as manufacturers seek to reduce weight and cost of vehicles, machines, constructions and devices or consumer good in general.

As part of the structural integrity domain, the mechanical characteristics of new material components, such as metal, alloy, concrete, polymers, ceramic, moulded structural plastics or advanced composites, are essential to achieving optimal safety, durability, flexibility, strength-to-weight ratio, performance, reliability and cost-effectiveness.

Scientists and engineers in product design, simulation and testing rely on material properties such as stress, strain, tensile modulus, and Poisson’s ratio. Accurate material property data prevents failures in the field and anticipates issues before they arise.

Thus, material properties testing is a critical step in understanding how your material will perform under a wide variety of stresses. It is commonly performed by testing machines, that meet the many ISO and ASTM standards. However, adding additional sensors is highly recommended as it helps to get an even better and more precise understanding of structural characteristics.

What is Material Properties or Coupon Testing?

Material testing breaks down into the task of finding the properties or characteristics in the fields of mechanical, thermal, electrical, corrosion, radiation, and biological deterioration.

The mechanical testing methods can be divided into destructive and non-destructive material testing:

  • Destructive Testing: Random samples are loaded so heavily that they are destroyed. This serves to determine the maximum load and the behaviour under the influence of this load.
  • Non-destructive Testing: Workpieces of the material are tested without destroying them.

A further classification of the test procedures is based on the type of load:

  • Static Testing: Loads (tensile, compressive, or bending loads) act very slowly or constantly on a material sample.
  • Dynamic Testing: The sample is subjected to an abrupt load or a load acting periodically over a longer period.
  • Cyclic Testing: The sample is subjected to recurring, swelling or alternating load cycles in, for example, sinusoidal form.
  • Impact Testing: The sample is subjected to an impact like as in a Charpy test.

In a tensile test, the test coupon is pulled to its breaking point. Based on the material characteristics you get a true understanding of the material´s behaviour, how much energy it may absorb allowing you to predict the performance of the product in its real-life application. Some tests may also need to be performed in environmental chambers.

solutions, applications, durability fatigue, material fatigue characterisation

Integrating a HBK Measurement Chain into Material Testing Systems 

In material testing, highly accurate sensor data helps to get a better and more precise picture of material properties and gives you the extra plus of getting deeper test data. Integrating QuantumX allows overlaying additional sensor data sources and delivers precise and reliable results.

The integration of an HBK measurement chain into material testing systems such as MTS, Instron or ZwickRoell is easy. You can directly integrate the unit:

  • In real-time via EtherCAT, PROFINET or voltage inputs
  • Via PC software integration, measuring with catman Easy in parallel fusing data file
  • Directly into the test machine software via simple API commands

Parallel installation enables you to also get sensor data while the material testing machine is running. Measurements on various places on the coupon and on any material are possible. You receive precise data about the material´s behaviour according to loads, strain, temperature and whatever you want to measure.

Want to see an example? Zwick Roell integrated QuantumX and catman into their testing system. Read more

 

HBK also offers material testing as a service , delivering fully characterized and interpreted material parameters ready for use in mechanical FEA or CAE-based fatigue analysis using  nCodeDesignLife .

Material Testing Machine Calibration

When a material testing machine is calibrated, reference points of the measurement device are compared to a reference sensor calibrated to a known traceable standard laboratory. Many material test machine manufacturers around the world calibrate their sensors and machines in production and in service with the HBK reference measurement chain.

 

DMP41 and MGCplus have a strong place in laboratories worldwide including the PTB, NIST and other metrological institutes. The QuantumX MX238B is the perfect portable tool for calibration services at customer sites. All HBK devices can be traced back to DAkkS by our accredited lab in Darmstadt, Germany,  guaranteeing that your calibration services are performed precisely and efficiently, with traceable results. Whether they are static or dynamic materials testing machines, HBK provides the perfect measurement solution.

 

Through mutual recognition of national accreditation bodies, we ensure worldwide validity of your calibration certificate and measurement results. The calibration procedures are determined by internationally recognized standards.

 

Calibrating the instrument itself can also be done. This ultimately certifies the overall accuracy and determines traceability of the measurements. Internationally recognized standards have been developed for calibration of crosshead speed and displacement (ASTM E2658 and E2309), strain and load rate (ASTM E2309), and measurement of tension, compression (ASTM E4), torque (ASTM E2624), and dynamic force (ASTM E467).

 

All in all, HBK offers the right tool set enabling a variety of calibration and maintenance services in a highly efficient and traceable way.

Explore Material Fatigue Characterisation by Application

Whether it's higher performance, lower weight, or an optimized manufacturing process, increasing product efficiency or durability starts with the selection of the appropriate materials. Be it a newly developed alloy or a composite, only a deep insight into its key material parameters will allow you to feed simulation or build prototypes. From design data for FEA fatigue analysis to consistent material quality assurance, the HBK Advanced Materials Characterization & Test facility (AMCT) offers a large variety of services to assess these parameters and increase confidence in your design. 

Integration of HBK measurement equipment into Zwick Roell testing system

In material testing, accurate sensor data enhances understanding of material properties. Integrating QuantumX allows you to overlay additional sensor data sources, resulting in precise, reliable results.

The HBK measurement chain can be integrated into systems like MTS, Instron, or ZwickRoell:

  • In real-time via EtherCAT, PROFINET or voltage inputs
  • Via PC software integration, for example, catman Easy
  • Directly into the test machine software via simple API commands

Parallel installation provides sensor data during testing, offering insights into the material’s behaviour under various conditions.

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