Laboratory for materials technology

Teaching

Destructive materials testing

Hardness testing

Hardness testing is a static procedure.

Hardness is understood as the resistance of a material to the penetration of a test specimen.

The hardness value can be used to draw conclusions about the strength of the material.

The following hardness testing methods are presented in the materials science laboratory:

  • Brinell (HB = Brinell hardness)
  • Vickes (HV = Vickers hardness)
  • Rockwell C (HRC = Rockwell Cone hardness)
  • Rockwell B (HRB = Rockwell Ball hardness)

Tensile test

The tensile test is used to determine the behaviour of the material under a shock-free, steadily increasing external tensile load that is evenly distributed over the entire cross-section.

The test is used to determine characteristic values for strength calculations of materials:

  • Yield strength ReH or Rp0.2
  • Elongation at break A
  • Tensile strength Rm
  • Uniform elongation Ag

Notched bar impact test (Charpy test)

The notched bar impact test is a method for determining the toughness of materials as a function of temperature.

A pendulum hammer falls down and smashes a V notch impact specimen. Work is "consumed" in this process. The consumed impact energy KV [J] related to the specimen cross-section is called the notched impact strength αk [J/cm2].

Metallography

Preparation of mostly metallic samples to analyse the microstructure with the aid of suitable light microscopes.

Non-destructive testing (NDT)

Penetrant testing

Dye penetrant testing is a simple method for detecting surface defects. For this purpose, a penetrant (red paint) is applied to the surface of the workpiece. The penetrant penetrates any surface defects due to capillary action. The component is cleaned after a specified penetration time so that the penetrant is not washed out of the defects. Subsequently, a developer is applied, e.g. with the help of a swirl chamber. The developer draws out the penetrant remaining in the surface defects. The developer forms a clearly visible white/red contrast with the penetrant in the area of surface defects.

Magnetic particle test

Magnetic particle test (also called fluxing) is a method for detecting cracks in or near the surface of ferromagnetic materials.

The field lines created by magnetisation run parallel to the surface. Cracks and near-surface defects that lie transverse to the field lines generate a magnetic stray field. This stray field marks the defect and is detected with the help of iron powder.

Eddy current testing

When an electric current flows through an electrical conductor (e.g. a wire coil), a magnetic field is generated around the wire.

In electrically conductive materials, alternating current generates an alternating magnetic field. If a fault is located in the area of the eddy currents, the eddy current paths lengthen, the paths become longer.

This causes a local weakening of the secondary alternating magnetic field.

This weakening is indicated by the measuring device.

Ultrasonic testing

Testing principle: Sound waves propagate in metals or other materials as mechanical vibrations in a straight line at high speed. They are reflected at boundary surfaces (defects) so that the sound that continues to travel is weakened. The signal is displayed on an oscillograph.

Pulse-echo method: The probe contains receiver and transmitter combined in one component.

Thermography

An infrared camera is used to visualise the distribution and intensity of the infrared radiation emitted by an object surface. A temperature gradient induces a heat flow in the component. Defects, such as delaminations in a fibre composite component, impede this heat flow. The thermographic camera detects the associated change in the distribution of the infrared radiation intensity emitted by the respective component surface.

Research

In addition to the laboratory courses in materials engineering within the framework of the courses of study in general mechanical engineering, process and environmental engineering, technical computer science in mechanical engineering, many student projects and theses are carried out in the field of destructive and non-destructive materials testing. The newly created foundry laboratory combines the manufacturing process (primary moulding) of a component with quality assurance (destructive and non-destructive material testing) in an advantageous way. Student project participants are given a practical insight into component manufacture and testing and are thus enabled to verify defects in the casting process using microstructure analyses, hardness testing and tensile testing as well as ultrasound and eddy current testing.

Interesting techniques

Airborne thermography

The project laboratory for materials in flight in materials engineering carries out airborne component screening using thermography on commercial aircraft to detect water inclusions in fibre composite honeycomb structures such as vertical stabilisers. A multicopter and, in cooperation with an external partner, a steerable aerostat (helium balloon) are used as a carrier platform for the thermographic camera.

Equipment

Destructive materials testing

  • Micro hardness tester Emco-Test Durascan Test loads 0.098-98 N, according to Vickers and Knoop
  • Rockwell B and C sclerometers
  • Brinell sclerometer
  • Vickers sclerometer
  • Materials testing machine Zwick/Roell (tension and compression) 250 kN
  • Materials testing machine Zwick/Roell (tension and compression) 10 kN
  • Materials testing machine Hegewald&Peschke (tension and compression) 5 kN
  • High frequency pulser Zwick/Roell
  • Pendulum impact tester Wolpert 300J (Charpy test)

Metallography

  • Radio spectrometer Belec
  • Hot embedding press Struers
  • Grinding and polishing machines Struers
  • Cutting machine Struers Labotom

Non-destructive materials testing

  • Optical 3D measuring system GOM Aramis
  • Test bench for penetrant testing
  • Magnetic particle test bench Tiede
  • Hand-held yoke magnet Uni-Flux
  • Eddy current tester Dr. Förster defectometer
  • Eddy current tester Olympus Nortec 500D
  • Ultrasonic detector General Electric Phasor XS
  • Thermographic camera Infratec Image IR 8300
  • Various sample components from aviation and automotive

Polymer technology/analytics

  • Climate chamber Binder -40 °C to 250 °C
  • Heating cabinet Memmert up to 300 °C
  • Heating cabinet Memmert up to 250 °C
  • Injection moulding machine Arburg Allrounder 250
  • Extruder Troester
  • Meltflow Index Cast
  • 3D printer Ultimaker 2+
  • XRD Bruker D2 Phaser (powder diffractometer)
  • STGA Netzsch Perseus F1 (simultaneous TG with IR residual gas analysis)
  • UV-VIS Perkin Elmer Lambda 650 S
  • FTIR Perkin Elmer Spectrum Two
  • Raman microscope Thermo Fisher DXR2
  • SEM Zeiss Leo 1455VP
  • DMA Mettler Toledo

Foundry laboratory

  • Muffle furnace Nabertherm up to 1200 °C
  • Various tools for sand mould casting including mould boxes, tampers, lancets, etc.

Project laboratory for materials in flight operations

  • Thermographic camera Workswell WIRIS UAV (airborne)
  • Thermographic camera VarioCam HD
  • Low velocity impact test bench for fibre composites up to 50J impact energy
  • Hexacopter 5 kg take-off mass
  • Various sample components from aviation and wind power

Impressions

The team

Doctoral student

Non-Public Person

Doctoral student

Research Assistant

Non-Public Person