不同形状压头作用下的压痕蠕变数值研究

A numerical Study of Indentation Creep Using Indenters of Different Geometry

采用有限元方法分析了圆锥压头、球形压头和圆柱形平压头作用下铝合金(2A12)的压痕蠕变行为,给出了三种压头作用下的等效蠕变应变、压痕深度-时间曲线和硬度-时间曲线。对于给定尺寸的三种压头,在相同载荷作用下,圆锥压头作用下的最大等效蠕变应变最大,圆柱形平压头作用下的最大等效蠕变应变最小;不同形状压头的压痕深度-时间曲线相似,由"瞬态蠕变"和"稳态蠕变"两段组成;而硬度随时间和压痕深度均呈现递减的趋势,不存在稳态数值。结果表明,在研究高温压痕蠕变现象、确定材料蠕变参数方面,平压头具有相当的优势:压头下方的应力场相对稳定,可不考虑摩擦和堆积的影响,计算简便准确。

The main purpose of the present study is to analyses the indentation creep behavior of aluminum alloy （2Al2） by using three different indenters with Finite Element Method （FEM）. The geometries of indenters are cone, sphere and cylinder which are all self-similar. In FEM results, the equivalent creep strain （CEEQ）fields, indentation depth time curves and hardness time curves were given. For the given indenter sizes and under the same indentation loads, the maximum CEEQ existed under conical indenter and the minimum one appeared under cylindrical indenter. The curves of indentation depth and time are similar, they are all made up of instantaneous stages and steady state stages. The hardness is decreased with time and there are no steady state existed. Results show that for cylindrical indenters there are much advantages than other indenters when they are used to study the high temperature creep and determine the creep parameters. The reasons are that the stress fields ahead the cylindrical indenters are stable, the friction and the pile up can not to be considered and it is convenient and accurate to calculate the creep parameters.