Impact compression and tensile testing by means of a Charpy pendulum

Abstract

Mathematical modelling and virtual testing of components and structures represent a useful and economical tool for design and safety assessment. The so called basic mechanical properties which can be found in material standards are not relevant in cases where the real service conditions differ from those applied during testing. Thus e.g. mechanical behaviour at higher strain rates can be interesting for the car components when the simulation of crash situations is used during structure development. The dynamic compression tests are usually performed by means of drop towers, dynamic tensile tests by means of high speed hydraulic testing machines or the Hopkinson bar method. At the Mechanical Testing Laboratory of the SKODA Research Inst. in Pilsen, Czech Republic, an instrumentation of a Charpy pendulum testing machine was realised in order for it to be possible to perform dynamic compression and tensile tests. A new striking tup and load measurement system were designed and calibrated. At the same time, new software was developed which makes it possible to evaluate the test force-deformation record. The correctness of the instrumentation and software was verified by comparison of measured and evaluated values of energies and deformations. A very good agreement was obtained. An international round-robin within the framework of the ESIS TC5-Subcommittee on “Mechanical testing at intermediate strain rates” is realised at present. 1 Impact tensile testing For the purposes of instrumented tensile testing, the Charpy pendulum was modified so that the force during the test could be measured. For this purpose a special load cell element was designed on the basis of tensometric measurement, © 2008 WIT Press WIT Transactions on the Built Environment, Vol 98, www.witpress.com, ISSN 1743-3509 (on-line) Structures Under Shock and Impact X 55 doi:10.2495/SU080061 see Fig.1, [1]. This solution made it possible to use the load measuring element repeatedly. The other structural modification shown in Fig.2 should ensure the correct position of the striker with respect to specimen position. The load cell calibration was performed statically at an MTS test machine. The correctness of the instrumentation was checked by means of comparison of tensile tests at static and impact loading for a common structural steel. The static tests were performed at ZWICK testing machine. Both static and impact tensile tests were carried out at room temperature. Figure 1: Load measuring element and test bar. Figure 2: Load cell, test specimen and pendulum modification. © 2008 WIT Press WIT Transactions on the Built Environment, Vol 98, www.witpress.com, ISSN 1743-3509 (on-line) 56 Structures Under Shock and Impact X