Hopkinson Bar Lab

A major research focus of the chair is the development of testing methods for high strain rate experiments and the application of these methods to metals, polymers, and structured materials such as foams or metamaterials. To this end, we operate a number of in-house built split-Hopkinson bars, which allow for tension and compression tests at strain rates up to 5000 /s. The lab is well equipped with high-speed cameras in both the visual and and infrared wavelength regime to provide in-situ analysis of strain and temperature evolution.

SHTB 1
Figure 1: Dynamic fracture of basalt-fibre reinforced epoxy composite at a strain rate of 300 /s.

Split-Hopkinson Tension Bar (SHTB)

SHTB Sketch
SHTB 2
Figure 2: Our main workhorse is a split Hopkinson tension bar with 16 mm diameter aluminium or steel bars.

Symmetric Direct-Impact Bar with instrumented striker

Symmpact
Symmpact
Figure 3: This is a direct-impact bar setup with 40 mm diameter polycarbonate bars. It is particularily well suited for compression tests on foams.

Large Direct-Impact Tension Bar

DITB Sketch
DITB
Figure 4: This is an inverted direct-impact bar setup composed of a short and heavy striker and an output bar of 39 m length. It allows for intermediate strain rate tests at rates of ~100 /s and testing durations up to 13 ms.

associated publications:

  • G.C. Ganzenmüller, E. Blaum, D. Mohrmann, T. Langhof, D. Plappert, N. Ledford, H. Paul, S. Hiermaier, A Simplified Design for a Split-Hopkinson Tension Bar with Long Pulse Duration, Procedia Engineering, vol 197, 2017, pages 109-118, https://doi.org/10.1016/j.proeng.2017.08.087.
  • G.C. Ganzenmüller, T. Langhof, S. Hiermaier, A Constant Acoustic Impedance Mount for Sheet-Type Specimens in the Tensile Split-Hopkinson Bar, EPJ Web Conf., vol 183, p. 02064, 2018, https://doi.org/10.1051/epjconf/201818302064
  • G.C. Ganzenmüller, D. Plappert, A. Trippel, S. Hiermaier, A Split-Hopkinson Tension Bar study on the dynamic strength of basalt-fibre composites, Composites Part B: Engineering, vol. 171, pp. 310-319, 2019, https://doi.org/10.1016/j.compositesb.2019.04.031
  • P. Jakkula, G. Ganzenmüller, and S. Hiermaier, “A direct impact tension bar setup for testing low-impedance materials at intermediate rates of strain,” Materials Letters, vol. 352, p. 135082, 2023. doi:10.1016/j.matlet.2023.135082
  • P. Jakkula, A. Cohen, B. Lukic, D. levi-hevroni, A. Rack, G. Ganzenmüller, and S. Hiermaier, “Split Hopkinson tension bar and universal testing machine for high-speed X-ray imaging of materials under tension,” Instruments, vol. 6, no. 3, p. 38, 2022. doi:10.3390/instruments6030038
  • P. Jakkula, G. C. Ganzenmüller, S. Beisel, P. Rüthnick, and S. Hiermaier, “The Symmpact: A direct-impact Hopkinson bar setup suitable for investigating dynamic equilibrium in low-impedance materials,” Experimental Mechanics, vol. 62, no. 2, pp. 213–222, 2021. doi:10.1007/s11340-021-00785-8
  • P. Jakkula, G. Ganzenmüller, F. Gutmann, A. Pfaff, J. Mermagen and S. Hiermaier, “Strain rate sensitivity of the additive manufacturing material Scalmalloy®,” Journal of Dynamic Behaviour of Materials, vol. 7, no. 4, pp. 518–525, 2021. doi:10.1007/s40870-021-00298-4
  • P. Jakkula and G. Ganzenmüller, “Defect analysis of 3D printed Al-Mg-Sc alloy using ultra-high-speed X-ray phase contrast imaging,” in DYMAT 2022 - Dynamic Behaviour of Additively Manufactured Structures and Materials, 2022, pp. 87–92. doi:10.6094/UNIFR/228460
  • P. Jakkula, G. Ganzenmüller, F. Gutmann, and S. Hiermaier, “Strain rate sensitivity of the aluminium-magnesium-scandium alloy - Scalmalloy®,” EPJ Web of Conferences, vol. 250, p. 05014, 2021. doi:10.1051/epjconf/202125005014
  • P. Jakkula, G. Ganzenmüller, S. Beisel, and S. Hiermaier, “Investigating slow shock in low-impedance materials using a direct impact Hopkinson bar setup,” EPJ Web of Conferences, vol. 250, p. 06009, 2021. doi:10.1051/epjconf/202125006009
  • G. Ganzenmüller, P. Jakkula, and S. Hiermaier, “Strain measurement by contour analysis,” Material Science - ArXiv, Nov. 2022. doi:10.48550/arXiv.2211.14030
  • G. Ganzenmüller, A Roth, P. Jakkula, F. Gutmann, A. Pfaff, D. Eakins, D. Chapman, B. Lukic, A. Rack and S. Hiermaier, “Vanishing auxetic behaviour for metal lattice structures at impact rates of strain,” in DYMAT 2022 - Dynamic Behaviour of Additively Manufactured Structures and Materials, 2022, pp. 97–102. doi:10.6094/UNIFR/228460
  • A. Roth, G. Ganzenmüller, F. Gutmann, P. Jakkula, F. Hild, A. Pfaff, K. Yin, C. Eberl and S. Hiermaier, “2D numerical simulation of Auxetic metamaterials based on force and deformation consistency,” Materials, vol. 15, no. 13, p. 4490, 2022. doi:10.3390/ma15134490