Laboratory for Mechanical Testing and Rapid Diagnostics
The Laboratory for Mechanical Testing and Rapid Diagnostics carries out chemical, microstructural and fractographic analysis of metallic materials and alloys. It is equipped with an optical emission spectrometer Q4 TASMAN Q101750 – C130 (Bruker AXS) and equipment for energy-dispersive X-ray spectroscopy (EDS). The laboratory performs quantitative and qualitative analysis of the elemental composition, structure and morphology of materials, diagnostics of industrial equipment and expert assessments of in-service failures.
Description of Activities
Services Provided by the Laboratory
Tensile testing at room temperature
Standards: BDS EN ISO 6892-1:2020; BDS EN ISO 527-1, -2: 2012.
The stress–strain diagram in tension at room temperature is determined. The test procedure complies with a selected standard for testing at room temperature. The software calculates the required mechanical properties. The numerical data are processed statistically.
The specimens must conform in shape to the standard and to the available gripping fixtures (flat: up to 8 mm thick; cylindrical: up to 16 mm gripping diameter; cylindrical with coarse thread from M8 to M16). An extensometer with a gauge length of 25 mm or 50 mm is used.
Tensile testing at elevated temperature
Standard BDS EN ISO 6892-2:2018.
The stress–strain diagram in tension at elevated temperature is determined. The software calculates the required mechanical properties. The numerical data are processed statistically.
The specimens must conform in shape to the standard and to the available gripping fixtures. The temperature chamber (up to 250 oC) is compatible with the hydraulic grips and allows testing of flat specimens up to 8 mm thick or cylindrical specimens up to 16 mm gripping diameter. Strain is measured with an extensometer with a gauge length of 25 mm or 50 mm (up to 200 oC).
Testing at high temperatures is performed in a high-temperature furnace (up to 1000 oC),
in which case the specimens are cylindrical and are secured by a coarse thread from M8 to M16. The extensometer has a gauge length of 25 mm.
Compression testing
Standard ASTM E9-19.
The loading platens may be fixed, or one platen may have a spherical seat. Short specimens (13 mm in diameter and 25 mm in height) are usually tested. The software calculates the required mechanical properties. The numerical data are processed statistically.
Metallic materials. Bend test.
BDS EN ISO 7438: 2020.
The resistance of metal strip or wire to cracking when bent to a selected angle around a former of specified radius (inner bending radius) is determined.
3-point bending and 4-point bending tests
The flexural strength of a rectangular specimen under three-point or four-point bending is determined. Support span up to 150 mm.
Equipment
HOPKINSON BAR – KOLSKY
The system consists of 3 bars with a diameter of 20 mm, mounted on sliding bearings and movable longitudinally. The specimen is cylindrical and is fixed between the first and the second bar. Strain gauges are bonded at the middle of these bars. Equipment is available for recording the strain gauge signals at a frequency of 1 MHz. A striker of selected length is accelerated to a selected velocity by means of compressed air. Upon impact at the beginning of the first bar, a mechanical pulse travels through the bar system. When the pulse reaches the end of the first bar (incident bar), this end begins to move very rapidly and the specimen is crushed. In the process, part of the incoming pulse (incident pulse) is reflected (reflected pulse), while another part passes through the specimen and the second bar (transmitted pulse bar).
The recorded diagrams are used to calculate the stress–strain diagram of the specimen under high-speed crushing. The mechanical properties of the material under impact compression are derived from the diagrams obtained.
The facility can be used in 2 configurations:
- for medium- and high-strength metals;
- for porous metals and other low-strength materials.
SYSTEM FOR DETERMINING MECHANICAL PROPERTIES IN STATIC AND DYNAMIC TESTING ZWICK/ROELL, HA-250
The system is shared between the Institute of Mechanics – BAS and the Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Centre “Acad. Angel Balevski” – BAS (IMSETHAC-BAS).
The HA-250 servo-hydraulic testing system is equipped with a high-temperature furnace (up to 1000 oC) and a temperature chamber (up to 250 oC), as well as fixtures for various types of experiments.
Main features:
- The clamping fixtures are rated up to 100 kN
- For tensile testing, hydraulic grips with jaws for flat specimens (up to 8 mm thick) and for cylindrical specimens (up to 16 mm gripping diameter) are used. They can be used with the temperature chamber.
- Extensometers with a gauge length of 25 mm or 50 mm, for flat or cylindrical specimens
- Bend test fixtures compatible with the temperature chamber. Support span up to 150 mm.
- Fixtures for clamping threaded specimens (M8 to M16, coarse thread), compatible with the high-temperature furnace.
- Compression fixtures (fixed or with a spherical seat)
- Software with programs configured for testing to various standards
- Software designed for cyclic testing.
Contacts
Institute of Mechanics – BAS
Acad. Georgi Bonchev St., Block 4, 1113 Sofia.
Assoc. Prof. Dr Eng. Rumen Krastev
Email: r_krastev@imbm.bas.bg
Tel. +359 889 701 105
Access to the Laboratory and Requests for Services
The laboratory is part of the research infrastructure of the National Centre of Excellence “Mechatronics and Clean Technologies” and is located on the Geo Milev campus. Requests for access and for joint research are therefore processed centrally – see Contacts. In addition, a full overview of the Centre’s other laboratories is available on the Infrastructure and Laboratories page.
The laboratory’s equipment was established under project BG16RFPR002-1.014-0006, funded by the Research, Innovation and Digitalisation for Smart Transformation Programme 2021–2027, co-financed by the European Union through the European Regional Development Fund.