| Summary: | 碩士 === 國立高雄應用科技大學 === 機械工程系 === 106 === This thesis investigates the mechanical properties and microstructure of different carbon steel with different heat treatment (A105、 A350 and A350-N). The original bars of the three mate-rials are forged and then cut to the required size. The static compression test are tested at 10 s-1, 10-2 s-1, 10-3 s-1 strain rate with Universal Material Testing Machine. And the dynamic impact test at strain rates of 2000s-1, 3300s-1, and 4300s-1 with Split Hopkinson Pressure Bar.
The experiments were carried out at room temperature and there did not fracture at the ex-perimental conditions. The results obtained from the experiment show that the sensitivity coeffi-cient and flow stress value of the three materials will vary with the strain rate. As the strain rate increases, the flow stress and the strain rate sensitivity coefficient increase. The comparison re-sults show that the A350-N has the better mechanical properties.
Observing the microstructure of all experimental materials by using an Optical Microscope. We can observe the deformation and destruction of grains after compression or impact. The de-formed appearance is mainly ductile deformation at low strain rate, and the appearance of grain damage can be observed at high strain rate. It can also be observed that as the strain rate in-creases, the grains also become larger.
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