Development of Tensile Split Hopkinson Pressure Bar Technique for Studying the Dynamic Behaviour of Metals

• Published in: Mechanics of solids 2023-12, Vol.58 (9), p.3315-3332
• Main Authors: Khan, Mohammad Mohsin, Kumar, Ajay, Iqbal, Mohd Ashraf
• Format: Article
• Language: English
• Subjects: Alignment; Amplitudes; Classical Mechanics; Design standards; Impact velocity; Incident waves; Physics; Physics and Astronomy; Split Hopkinson pressure bars; Strain gauges
• ISSN: 0025-6544; 1934-7936
• DOI: 10.3103/S0025654423601568

The tensile split-Hopkinson pressure bar (SHPB) system is significantly used for dynamic material characterization of metals in the range of strain rates 10 2 –10 4 s –1 . There is no standard design methodology or readily available technique for the development of this apparatus. In the present study, a detailed design and development of tensile SHPB apparatus for dynamic material characterization of metals in tension has been presented. The output incident and transmitted wave signals obtained were found to be consistent with the striker bar impact velocity that was varied in the range 4–14 m/s and the wave speed in the steel 4340 bar observed as 5144 m/s. The elastic compressive wave generated in incident bar, which was effectively transmitted to the transmission bar through the shoulder. This process showcased the high accuracy and precision of the bar alignment system, along with the parallel alignment of the bar end faces. To avoid the disturbance caused by the shoulder in the output bar, the length of the output bar and input bar were set to 2000 and 1500 mm, respectively. Furthermore, positioning SG-2 along the output bar and SG-3 along the input bar was found the most optimal position to avoid disturbances in the output signals. The average experimental incident wave strain peak amplitude (Average of strain at SG-1 and SG-2) recorded at 4.1, 5.95, 8.3, 10.3, and 12.5 m/s striker impact velocity was –405, –588, –815, –1014, and –1243 micro-strain, respectively. It was observed –1.69, –1.76, –1.03, –1.36, and –2.37% error in the incident wave strain amplitude at the respective impact velocities. Similarly for the proper alignment of Striker, incident, shoulder, and transmission bar, the average values of the recorded strain gauges have 1.80, 1.93, 1.43, 1.26 and 1.70% higher strain amplitude as compared to analytical values corresponding to their striker impact velocities. Based on experimental results, it has been observed there were less than 2.5% error was observed in the average peak strain in comparison to the analytical results. Hence, it has been concluded that the system is accurately aligned such that in the absence of a specimen the striker, incident, shoulder, and transmission bars function as a single bar. It may be concluded that the developed SHPB-T setup has been well calibrated and could be suitably used to perform the further experiments on metals.