应变速率对不同强度双相钢动态力学特性的影响

Effect of strain rate on dynamic mechanical characteristics of dual phase steel with different strengths

以具有相同厚度的高强双相钢HC420/780DPD+Z和HC550/DPD+Z为研究对象,通过试验获取了静态力学性能参数和不同应变速率下的动态力学特性曲线,提取了关键性能参数,获取了其与应变速率间的关系;对比了不同强度的两种材料在不同应变速率下的性能变化差异;获取了不同应变速率下的断口形貌并对比分析了不同强度材料的差异;基于帽形薄壁梁落锤压溃吸能试验,对比了两种材料在不同冲击能量下的承载和吸能特性差异。结果表明,随应变速率的增加,两种材料的屈服强度和抗拉强度具有一定程度的提升,敏感性增强;HC420/780DPD+Z的塑性呈现先增强后减弱的趋势,而HC550/980DPD+Z的塑性变化较小;HC420/780DPD+Z的断口形貌随着应变速率的升高呈现出明显的尺寸差异,HC550/980DPD+Z的断口形貌均表现为较明显的等轴韧窝,韧窝的深度增大,尺寸略有减小,均匀性变化不大。随着碰撞速率的增加,材料的载荷比和吸能比逐渐降低。在相同的冲击条件下,随着材料强度的增加,材料的吸能比有所下降,但是HC550/980DPD+Z的载荷比较大,承载力波动较其他材料小,因此具有更好的承载特性。

Taking high strength dual phase steels HC420/780 DPD+Z and HC550/DPD+Z with the same thickness as the research objects,the static mechanical property parameters and dynamic mechanical characteristic curves with different strain rates were obtained by tests.The key property parameters were extracted and the relationships between them and strain rate were obtained.The difference of property variation of the two kinds of materials with different strengths and different strain rates was compared.The fracture morphology with different strain rates was obtained and the differences between materials with different strengths were compared and analyzed.Based on the energy absorption drop hammer crush test of cap-shaped thin-walled beam,the difference of bearing capacity and energy absorption characteristics of the two materials with different impact energies was compared.The results show that with the increase of strain rate,the yield strength and tensile strength of the two materials are improved to a certain extent,and the sensitivity is enhanced;the plasticity of HC420/780 DPD+Z decreases after strengthening,while the plasticity of HC550/980 DPD+Z changes little.The fracture morphology of HC420/780 DPD+Z shows obvious size difference with the increase of strain rate.The fracture morphology of HC550/980 DPD+Z shows obvious equiaxed dimples,and the dimple depth increases,the dimple size decreases slightly,and the uniformity changes little.With the increase of collision rate,the load ratio and energy absorption ratio decrease gradually.Under the same impact conditions,with the increase of material strength,the energy absorption ratio of material decreases,but the load ratio of HC550/980 DPD+Z is larger,the bearing capacity fluctuation is smaller than that of other material,so it has better bearing characteristics.