Modeling and numerical analysis of roller burnishing of AISI 4140 steel

ABSTRACT Metallic components for engineering applications are often employed under the action of thermal and mechanical loads, which tend to reduce their lifespan. Mechanical surface treatments appear as an alternative capable of extending the service life of these materials. These processes act by plastically deforming the surface, increasing its surface hardness and inducing compressive residual stresses. The combination of these factors leads to an increase of the part lifespan because it diminishes the nucleation and propagation of cracks, which are responsible for material failure by fracture. Although surface treatment processes such as shot peening and laser shock peening are widely used to induce compressive stresses, roller burnishing not only induces compressive stress and increases surface hardness, but also promotes the reduction of surface roughness. In this work, two-dimensional numerical simulation using the Finite Element Method (FEM) method for roller burnishing the hardened ABNT 4140 (40 HRC) steel was performed, considering the tool a rigid element, while the part was assumed as elasto-plastic. Burnishing force and feed rate were selected as input parameters which influence on roughness and residual stress induction was investigated. Moreover, unlike other two-dimensional numerical models, the initial roughness of the part was introduced in order to assess its influence on the process. In addition to that, the numerical simulation occurs in the interval from one peak to the other, defined by the feed mark of the previous turning operation (0.2 mm). The HertzWin software was used to define the feed rate for each condition, which was based on the half contact width (b) obtained for each force separately. The numerical results suggest the reduction of roughness and the increase of compressive residual when the rolling force is increased and the feed rate is reduced.

摘要
工程应用中的金属构件常处于热-机械联合载荷作用下，此类载荷往往会缩短其服役寿命。机械表面处理技术作为延长这类材料服役寿命的有效手段，可通过对工件表面实施塑性变形，提升其表面硬度并引入残余压应力。上述两类效应的协同作用可抑制引发材料断裂失效的裂纹形核与扩展过程，进而延长构件的服役寿命。尽管喷丸强化（shot peening）与激光冲击强化（laser shock peening）等表面处理工艺已被广泛用于引入残余压应力，但滚压加工（roller burnishing）不仅可引入残余压应力、提升表面硬度，还能有效降低表面粗糙度。
本研究针对硬度为40 HRC的ABNT 4140钢开展滚压加工的二维有限元法（Finite Element Method, FEM）数值模拟：将刀具视为刚性体，工件则采用弹塑性本构模型。本研究选取滚压力与进给量作为输入参数，探究其对表面粗糙度与残余压应力引入效果的影响规律。此外，与现有多数二维数值模型不同，本模型引入了工件初始表面粗糙度，以评估其对滚压加工过程的影响。同时，本次数值模拟的计算区间限定于前车削工序留下的进给痕（0.2 mm）范围内，即相邻两个峰谷之间的区域。本次研究采用HertzWin软件，基于不同滚压力下单独计算得到的半接触宽度（b），为各工况确定对应的进给量。数值模拟结果表明：提升滚压力、降低进给量，可实现表面粗糙度的降低与残余压应力幅值的提升。