Вариационный подход к определению динамической прочности материала

The problem of the determination of material strength properties through the Kolsky experimental technique is considered. Small size specimens of M1 copper alloy are tested on a split Hopkinson pressure bars equipment. The experimental data of tensile tests observed under both dynamic and quasi-static conditions are analysed within the framework of the incubation time criterion and the Sign-Perturbed Sums method. It is shown that the influence of a test performance error is considered in the data treatment procedure based on the developed method.

Size Effect in the Split Hopkinson Pressure Bar Experiment

For many structures, their service environment is very strict, and the requirements for the impact resistance of materials are very high. Therefore, the dynamic testing method has important scientific significance and application value for practical engineering. Split Hopkinson pressure bar (SHPB) is one of the most common experimental methods for obtaining dynamic mechanical properties of materials. However, there is no uniform standard for the size of the bars and specimens used in the test. Theoretically, the size has little influence on the experimental results, but it has not been proved by experiments. This paper mainly studies the influence of device/specimen sizes of split Hopkinson pressure bar through experiments, it is demonstrated that the sizes of bars and specimen have little effect on experimental results.

Experimental Work for Bar Straightness Effect Evaluation of Split Hopkinson Pressure Bar

Bar straightness is one of several factors that can affect the quality of the strain wave signal in a Split Hopkinson Pressure Bar (SHPB). Recently, it was found that the bar components of the SHPB at the Lightweight Structures Laboratory displayed a deviation in straightness because of manufacturing limitations. An evaluation was needed to determine whether the strain wave signals produced from this SHPB are acceptable or not. A numerical model was developed to investigate this effect. In this paper, experimental work was performed to evaluate the quality of the signal in the SHPB and to validate the numerical model. Good agreement between the experimental results and the numerical results was obtained for the strain rates and stress-strain relationship for mild steel ST37 and aluminum 6061 specimen materials. The recommended bar straightness tolerance is proposed as 0.36 mm per 100 mm.

On the Development of a Release Mechanism for a Split Hopkinson Tension and Compression Bar

Split Hopkinson bars are used for the dynamic mechanical characterisation of materials under high strain rates. Many of these test benches are designed in such a way that they can either be used for compressive or tensile loading. The goal of the present work is to develop a release mechanism for an elastically pre-stressed Split Hopkinson bar that can be universally used for tensile or compressive loading. The paper describes the design and dimensioning of the release mechanism, including the brittle failing wear parts from ultra-high strength steel. Additionally, a numerical study on the effect of the time-to-full-release on the pulse-shape and pulse-rising time was conducted. The results of the analytical dimensioning approaches for the release mechanism, including the wear parts, were validated against experimental tests. It can be demonstrated that the designed release concept leads to sufficiently short and reproducible pulse rising times of roughly 0.11 ms to 0.21 ms, depending on the pre-loading level for both the tension and compression wave. According to literature, the usual pulse rising times can range from 0.01 ms to 0.35 ms, which leads to the conclusion that a good average pulse rising time was achieved with the present release system.