冲击载荷下剪切断裂研究

利用Hopkinson压杆技术对单边平行双裂纹试样倒向加载，在较大的加载率范围，对Ti6Al4V钛合金和40CrNiMoA两种材料的动态剪切断裂行为进行了研究．实验结果表明：存在两类韧性剪切断裂模式，即常规的韧性剪切型断裂和绝热剪切断裂．常规剪切型断裂模式的断裂韧性KⅡd随加载率的提高而增大，而绝热剪切型的断裂韧性KⅡd则随加载率的提高而减小，并且，当加载率增大至某一临界值时，常规的韧性剪切断裂模式将转变为绝热剪切断裂破坏模式．

An Investigation on Shear Fracture under Impact Loading

In this paper, a single Hopkinson pressure bar technique was used for testing plate specimen with two parallel edge cracks. The dynamic mode- Ⅱ fracture toughness was studied at a relatively wide range of loading rate for titanium alloy Ti6Al4V and alloy steel 40CrNiMoA. The results show that two markedly different types of crack shear extension exist for in-plane-shear fracture, i.e., the usual ductile shear fracture and the adiabatic shearing fracture. The dynamic fracture toughness KⅡ d increases with increasing loading rate when the failure is controlled by the usual shear fracture, while the KⅡ d decreases with increasing loading rate when it is predominated by the adiabatic shearing fracture. A transition of two types occurs at a critical loading rate.