The Mechanical Testing infrastructure consists of the following apparatus for the measurement of the mechanical properties of materials.
Depth sensing indenter
Fig. 1: Depth sensing indenter
- Nano-module for nano-indentation (forces up to 600 mN)
- Micro-module for micro-indentation (forces up to 200 N)
- Motorized lateral (XY) 50mm×100mm movement with lateral accuracy <2 µm
- Motorized 25 mm Z motion
- Video zoom microscope, magnification up to ×100
It is used for the measurement of the mechanical properties of materials such as hardness, stress strain curves (Fig. 2) Young’s modulus, yield strength, creep, fatigue and fracture toughness. During indentation an indenter tip is driven into the sample by applying an increasing load up to a targeted value. The measured load is then gradually decreased until partial, or complete, relaxation of the sample has occurred. The load and displacement are recorded continuously throughout this process to produce a load-displacement curve (Fig. 3). The creep is measured by maintaining the applied force at a constant maximum value and measuring the change in depth of the indenter as a function of time. Multiple loading/unloading cycles can be used to study fatigue material properties.
Fig. 2: Stress-strain curves on tungsten W(100) single crystal before and after neutron irradiation employing a spherical indenter. These curves can be used for the determination of the yield strength and fracture toughness of the materials.
Fig. 3: Load-depth and creep curves from Vickers micro-indentation experiments on tungsten W(100) single crystal before and after neutron irradiation. The images of the residual imprints on the surface of the specimens after indentation experiments are presented.
Universal Testing Machine
- High accuracy load cells of 10 kN and 50 kN maximum force in tension and compression
- Laser for displacement measurements up to 5 mm with readability 0.0001mm and accuracy 0.2% of reading
for the measurement of
- Stress-strain curves in tension or compression
- Pull-off tests
- Joints strengths
Impulse Excitation Apparatus
Fig. 1: Impulse excitation apparatus for the the measurement of the elastic properties
The Impulse Excitation Technique is a non-destructive dynamic method for determining the elastic properties (Young’s and shear moduli and Poisson ratio) of materials that are elastic, homogeneous and isotropic. The measurement principle is based on automatic tapping of the sample with a small projectile and recording the induced vibration signal with a microphone. The acquired vibration signal in the time domain is converted to the frequency domain by a fast Fourier transformation. Dedicated software determines the resonant frequency with high accuracy to calculate the elastic properties based on the classical beam theory.
Fig. 2: Amplitude versus time after excitation of tungsten single crystal
Fig. 3: Power versus frequency-Fourier transformation of the spectrum of Fig. 2