High Cycle Fatigue (HCF)

Periodic stress might cause premature failure of material. This can be an important criterion for the design of component parts. Therefore tests are performed in material testing for the determination of material characteristics. There is a distinction between two respectively three different kinds of fatigue. 

 

  • Low Cycle Fatigue (LCF) for fatigue caused by low loading 
  • High Cycle Fatigue (HCF) and
  • Very High Cycle Fatigue (VHCF) caused by vibration endurance performance

 

This article deals with tests concerning High Cycle Fatigue (HCF) and Very High Cycle Fatigue (VHCF), that is to say that the vibration endurance performance of material samples is evaluated. There is no standard definition for the distinction between HCF and VHCF. Tests with 104 up to 108 cycles and frequencies of 20 to 250 Hz often are referred to as HCF. Tests with more than 108 cycles usually are considered to be VHCF. But sometimes even tests with less than 108 cycles are already considered to be VHCF.  Every now and then there are also tests performed with 35000 Hz.  

 

Measuring during HCF Tests

The  H.-D. Rudolph GmbH deals with the evaluation of HCF and VHCF tests by means of electro-optical measurement. Since the frequencies – unlike with LCF tests - can be rather high, the focus is not only on choosing a measuring device offering very high resolution but also high measurement frequencies. Sometimes there is even the requirement to measure on very hot samples (up to 3000° C), which is hardly possible with mechanically touching methods. Another advantage of the electro-optical measuring principle is the absence of mechanically moving parts, which guarantees wearfree operation. 

If you want to evaluate HCF or VHCF tests, please feel free to contact us in order to find a solution for your individual requirements.

In order to give you a first overview, in the following please find a presentation of some standard solutions concerning (Very) High Cycle Fatigue Tests. Measuring systems can be offered with a bandwidth of up to 500 kHz and a resolution to up to 1:128000.

 

CMOS Line Scan Sensor ZS64A5K


The ZS64A5K is a CMOS line scan sensor with a very high resolution used for non-contact dimensional measurement. By means of a lens the object to be measured is imaged to the linear CMOS array in the sensor. The lens determines the measuring range. Standard lenses can cover measuring ranges from 1 mm to 5000 mm. 

 

ZS32

 Characteristics of the ZS64A5K:

  • High resolution of 1:64000
  • Measuring range 5 mm – 5000 mm
  • High sensitivity for shortest exposure times
  • Scan rate 4673/s
  • Narrow scanning width
  • Standard version: Detection of two edge positions, light/dark or dark/light
  • Measuring values: Edge A, Edge B, B-A or (A+B)/2
  • Optional version: Detection of max. eight edge positions
  • Analog, calibrated live measuring values

 

 

Digital Extensometer ZS128

Digital Extensometer ZS 32

With 4673 measurements per second and a resolution of 1:128000 the digital extensometer ZS128 electro-optically measures strain on material samples. The digital sensors guarantee high stability and maintenance-free operation. The immediate delivery of calibrated values takes place during dynamic as well as endurance tests. The extensometer is able to perform measurements of strain on material hot up to 3000° C.  

 

Characteristics of the ZS128:

  • Measuring ranges: 2 mm – 1000 mm
  • Working distances: 40 mm – 10 m
  • Resolution: 0.0016 %
  • Scan rate: 4673/s

 

 

200XR (Extensometer)

The electro-optical Extensometer 200XR contactlessly measures the motion of two black-and-white edges (targets) on a sample. The analog output signal is proportional to the strain. The integrated viewer and the two liquid crystal displays simplify the performance of the adjustments required for the setup of the instrument; the viewer also allows observing the black-and-white edges on the sample while measuring takes place.

 

Characteristics of the 200XR (Extensometer):

  • Measuring ranges: 1 mm – 500 mm
  • Range of frequency: 0 – 250 kHz (special version with 500 kHz)
  • Output voltage: +/- 10V
  • Delivery of individual measuring values
  • Output signals always calibrated and live
  • Gauge length adapters to be delivered on request

Hopkinson Bar

 

Line Scan Sensor ZS16AHS:

ZS32

The Line Scan Sensor ZS16 AHS is designed for non-contact measurement of edge positions by means of digital line scanning. The object to be measured is imaged with a lens to the linear array in the ZS16AHS. The measuring range depends on the lens used. Standard lenses can cover measuring ranges from 1mm to 2000 mm. 

 

Characteristics of the ZS16A and ZS16AHS:

  • High resolution: 1:16000 (interpolated)
  • Measuring ranges: 1 mm – 2000 mm
  • Working distances: 20 mm – 200 m
  • Calibrated live output signals for strain-controlled testing
  • Analog output of measuring values
  • Scan Rate: 4673/s 
  • High sensitivity for shortest exposure times
  • Narrow scanning width
  • Operating voltage: 18 – 36 V/DC