Registered Macrohardness with Temperature Control


Compared with conventional hardness testing methods, which allow solely the determination of a hardness value, the use of registering electronic measurement equipment (instrumentation) permit the recording of the total load–indentation depth–behaviour of the indentation process, whereby a significantly higher information content about the material behaviour is achieved (e.g. stress relaxation, creep, plastic and elastic parts of the total energy…).

Instrumented macrohardness testing with temperature control is an extension of the registered hardness testing, which is normally carried out at room temperature.

The hardness of polymer materials is greatly influenced by the temperature in analogy to other mechanical properties. With the new development of the temperature control for the macrohardness, the hardness as a function of the testing temperature as well as the creep and relaxation behaviour of polymers or polymer composites may be investigated with different indenter geometries.

Furthermore, the new macrohardness testing equipment with a temperature chamber may be used for the time lapse determination of the long-term creep behaviour. This is called Stepped Isothermal Method (SIM). It is based on the time-temperature superposition principle and shows a methodical extension of the Stepped Isothermal method under tensile load. Instead of detecting the strain as a function of time, as usual, the indentation depth is determined as a function of time in this case. Instead of determining elongation as a function of time, which is normally the case, here the indentation depth is determined as a function of time. The indentation-time diagrams obtained provide the basis of the master curve construction, e.g. in the form of time-dependent indentation creep.
The SIM method with macroindentation testing distinguishes itself through very lower sample consumption, is extremely time lapsed and comparatively easy to carry out. The SIM method with macroindentation testing as a surface-sensitive method characterises ageing phenomena more adequately than other testing methods for a mechanical long-term characterisation because the ageing begins on the surfaces of the specimens.

Schematic set-up of instrumented macrohardness testing with temperature chamber

Specimen Preparation

  • Specimen requirements: smooth, flat, plane-parallel, a minimum thickness corresponding to the respective method
  • Extraction from components

Testing Conditions

  • Registered macrohardness testing system Zwicki ZHU 2.5 with temperature control
  • Temperature range from -100 °C to +100 °C
    • Different indenter geometries such as Vickers or Knoop pyramid indenters or various spherical indenters (diameter 3.175 mm, 6.35 mm, 5 mm)
  • Feasibility of different standardised hardness testing methods by individually programmable cycles of loading and unloading relating to control type (load- and indentation depth-controlled), preload and testing load, loading time and loading rates, etc.

Standards

  • DIN EN ISO 14577:
    Metallic materials – Instrumented indentation test for hardness and materials parameters
    • Part 1: Test method
  • DIN EN ISO 2039:
    Plastics – Determination of hardness
    • Part 2: Rockwell hardness
  • ASTM D 785:
    Standard Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials

Contact

Dipl.-Wirtsch.-Ing. Stephan Arndt
Telefon: +49 (0)3461 30889-68
stephan.arndt@psm-merseburg.de

Dr. Ralf Lach
Telefon: +49 (0)3461 30889-67
ralf.lach@psm-merseburg.de

Quickinfo

Procedures

  • Registered macrohardness with temperature control
  • Instrumented hardness testing
  • Hardness testing on plastics
  • Knoop indenter
  • Vickers indenter
  • Spherical indenter

Results

  • Martens hardness HM
  • Elastic indentation modulus EIT
  • Plastic and elastic part of the total deformation work Wplast or Welast
  • Indentation harness HIT
  • Indentation creep CIT
  • Indentation relaxation RIT
  • Rockwell hardnesses HRM, HRE, HRK

Standards

  • DIN EN ISO 14577-1
  • DIN EN ISO 2039-2
  • ASTM D 785