Background

While near surface residual stress (NSRS) from milling is a driver for distortion in aluminum parts there are few studies that directly compare available techniques for NSRS measurement.

Objective

We report application and assessment of four different techniques for evaluating residual stress versus depth in milled aluminum parts.

Methods

The four techniques are: hole-drilling, slotting, cos(α) x-ray diffraction (XRD), and sin²(ψ) XRD, all including incremental material removal to produce a stress versus depth profile. The milled aluminum parts are cut from stress-relieved plate, AA7050-T7451, with a range of table and tool speeds used to mill a large flat surface in several samples. NSRS measurements are made at specified locations on each sample.

Results

Resulting data show that NSRS from three techniques are in general agreement: hole-drilling, slotting, and sin²(ψ) XRD. At shallow depths (< 0.03 mm), sin²(ψ) XRD data have the best repeatability (< 15 MPa), but at larger depths (> 0.04 mm) hole-drilling and slotting have the best repeatability (< 10 MPa). NSRS data from cos(α) XRD differ from data provided by other techniques and the data are less repeatable. NSRS data for different milling parameters show that the depth of NSRS increases with feed per tooth and is unaffected by cutting speed.

Conclusion

Hole-drilling, slotting, and sin²(ψ) XRD provided comparable results when assessing milling-induced near surface residual stress in aluminum. Combining a simple distortion test, comprising removal of a 1 mm thick wafer at the milled surface, with a companion stress analysis showed that NSRS data from hole-drilling are most consistent with milling-induced distortion.

中文翻译：

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铣削铝中近表面残余应力测量的方法间比较和评估

背景

虽然铣削产生的近表面残余应力 (NSRS) 是铝零件变形的驱动因素，但很少有研究直接比较可用的 NSRS 测量技术。

客观的

我们报告了四种不同技术的应用和评估，用于评估铣削铝制零件的残余应力与深度。

方法

这四种技术是：钻孔、开槽、cos(α) X 射线衍射 (XRD) 和 sin ² (ψ) XRD，所有技术都包括增量材料去除以产生应力与深度曲线。铣削的铝制零件是从应力消除板 AA7050-T7451 上切割的，使用一系列工作台和刀具速度在多个样品中铣削大平面。NSRS 测量是在每个样本的指定位置进行的。

结果

结果数据表明，来自三种技术的 NSRS 大体一致：钻孔、开槽和 sin ² (ψ) XRD。在浅层深度 (< 0.03 mm) 处，sin ² (ψ) XRD 数据具有最佳重复性 (< 15 MPa)，但在较大深度 (> 0.04 mm) 处，钻孔和开槽具有最佳重复性 (< 10 MPa)。来自 cos(α) XRD 的 NSRS 数据与其他技术提供的数据不同，并且数据的可重复性较低。不同铣削参数的 NSRS 数据表明，NSRS 的深度随着每齿进给量而增加，并且不受切削速度的影响。

结论

在评估铝中铣削引起的近表面残余应力时，钻孔、开槽和 sin ² (ψ) XRD 提供了可比较的结果。将简单的变形测试（包括在铣削表面去除 1 毫米厚的晶片）与伴随应力分析相结合，表明来自钻孔的 NSRS 数据与铣削引起的变形最一致。