Influence of Process Parameters on Surface Hardening in Hammer Peening and Deep Rolling
Influence of Process Parameters on Surface Hardening in Hammer Peening and Deep Rolling
复制标题
工艺参数对锤击和深滚压表面硬化的影响
DOI：
10.4028/www.scientific.net/kem.554-557.1819
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
P. Groche
中科院分区：
文献类型：
--
作者：
J. Scheil;C. Müller;M. Steitz;P. Groche
本文着重对机械表面处理深轧(DR)和机械锤击强化(MHP)的工艺参数对硬度提高的影响进行了统计评价。在MHP工艺中，球形硬质合金刀具被反复加速到材料表面。就像喷丸工艺一样，MHP是一种冲击处理，尽管在MHP中，冲击区域是可以控制的，从而获得所需的冲击密度。在DR中，球形刀具与工件之间的接触与MHP有很大不同，因为球形刀具在沿表面移动时处于滑动接触状态。尽管两种表面处理的材料载荷不同，但得到的表面结构是相同的。两者都会导致冷加工、光滑的表面，包括压缩残留物。从技术上讲，DR和MHP参数已经成为研究的一部分，但仍然缺乏对导致表面硬化的每个工艺参数的统计验证。本文试图弥合这一差距。分别对1.2379工具钢和EN-JS-2070型灰口铸铁等不同材料进行了DR和MHP试验。使用部分析因试验设计，建立了能够检验每个工艺参数的影响的实验矩阵。影响DR的主要因素有：轧制压力、锤痕间距、滚珠直径和行走速度。对于MHP，研究了以下工艺参数的影响：锤击方向与表面法线的夹角、锤击轨迹的线距、锤击球的直径、锤击能量、行进速度和锤击频率。在每一个样品上进行十个布氏硬度刻度，这给出了在至少95%的可信区间内计算每一个工艺参数的影响所需的统计覆盖率。对于所有提到的材料，都计算了每个单独的工艺参数对硬化的影响。结果表明，尤其是铸铁的加载是非常复杂的，因为过高的冲击能(MHP)或接触压力(DR)会导致材料过载，导致表面退化。通过有限元模拟，至少给出了描述刀具直径对表面硬度的不同影响的解释方法。这些有限元模拟包含一个先进的材料模型，其中实现了1.2379的包辛格效应。可以清楚地表明，在DR中，与较小的刀具直径相比，较大的刀具直径会在材料表面产生更多的冷加工，从而导致表面更加坚硬。与DR不同，MHP中的接触压力是由赫兹压力分布决定的。在这里，较小的刀具直径会产生较大的赫兹压力，从而产生较高的冷加工量。
This paper focusses on the statistical evaluation of process parameters in the mechanical surface treatments deep rolling (DR) and machine hammer peening (MHP) on the hardness increase. In MHP process a spherical hard metal tool is repeatedly accelerated onto the material surface. Just as the shot peening process MHP is an impact treatment although in MHP the impact area can be controlled, leading to the desired impact density. In DR the contact between spherical tool and work piece is quite different to MHP as the spherical is in sliding contact as it is moved along the surface. Although the material loading of both surface treatments vary, the resulting surface structure is the same. Both lead to a cold worked, smooth surface including compressive residual. Technically DR and MHP parameters have been part of researches but there still is a lack of statistical validation of every single process parameter leading to a hardened surface. This paper tries to close this gap. DR and MHP are conducted on different materials, containing tool steel 1.2379 and grey cast iron EN-JS-2070. Using a fractional factorial test design an experimental matrix was created able to examine the influence of every single process parameter. Which were for DR: rolling pressure, line spacing between hammer traces, diameter of roller ball and the travelling speed. For MHP the influence of the following process parameters was investigated: angle between hammering direction and surface normal, line spacing between hammering traces, diameter of hammering ball, hammering energy, travelling speed and hammering frequency. On every single sample ten Brinell hardness indents are made which give the statistical coverage needed to calculate the effect of every single process parameter within a confidence interval of at least 95 %. For all mentioned materials the effect of every single process parameter has been calculated with respect to hardening. It could be shown that especially the loading of the cast iron is quiet complex as a high amount of impact energy (MHP) or contact pressure (DR) can lead to overloading of the material leading to a degradation of the surface. At least an explanatory approach which describes the different influence of the tool diameter on the surface hardness is given using FEM simulations. These FEM simulations contain an advanced material model in which the Bauschinger-effect of 1.2379 is implemented. It can be clearly shown that a larger tool diameter in DR produces a higher amount of cold working in the material surface leading to harder surfaces compared to the smaller tool diameter. In contrast to DR the contact pressure in MHP is determined by the Hertzian pressure distribution. Here smaller tool diameters create larger Hertzian pressure and therefore a higher amount of cold working.