乙烯基酯树脂浇铸体的高应变率压缩响应行为

利用电子万能试验机和分离式Hopkinson 压杆研究了乙烯基酯树脂浇铸体在准静态和高应变率下的压缩特性, 考察了试样压缩失稳和破坏的形貌。结果表明: 在准静态加载下(应变率为3.3 ×10 -4 / s～6.6 ×10-3 / s) ,材料呈韧性破坏, 失稳应力、失稳应变能密度均随应变率的提高而提高, 失稳应变随应变率的提高而降低; 在高应变率下(应变率为950/ s～5800/ s) , 材料呈脆性破坏, 失稳应力、失稳应变能密度均随应变率的提高呈增加趋势, 而失稳应变也随应变率的提高而提高, 这与准静态不同, 表明在高应变率下, 材料发生了“强迫高弹形变”。观察试样失稳和破坏后的形貌可以发现, 试样的破坏在失稳前正应力起主导作用, 失稳后切应力起主导作用, 使试样产生裂纹进而造成宏观破坏; 乙烯基酯树脂内部损伤的演化, 也依赖于应变和应变率。

Effect of strain rate on the compression behavior of vinyl ester resin casting

Quasi-static and high st rain rate compressive experiment s on the vinyl ester resin casting were carriedout by using a material universal testing machine and Hopkinson bar , and the behaviors of compressive instabilityand f racture of the resin casting at different st rain rates were investigated. The result s indicate that the response behavior of the resin casting is cont rolled by different mechanisms at different st rain rates and some mechanical properties of vinyl ester casting are rate-dependent : the castings are dest royed in a toughness mode at st rain rate 3. 3 ×10-4 / s～6. 6 ×10 -3 / s , while the castings are dest royed in a brittleness mode at st rain rate 950/ s～5800/ s. Theyield st ress , yield st rain energy density are all increased with the increasing of st rain rates under quasi-static loadingas well as under high st rain rates loading. What is interesting is that the yield st rain is decreased with the st rain rateincreasing under quasi-static loadings while it is increased under high st rain rate loadings. It is considered that in thecasting there occurred forced high elastic deformation at high st rain rates. The damage of the specimens is mainlycont rolled by axial st ress before unstable deformation , while mainly cont rolled by shear stress after unstable deformation , and then all f racture finally. The development of the cracks inside the castings is also rate-dependent .