Near process flow measurements of the cooling lubricant supply in grinding processes

两相流的光流测量尤其具有挑战性，因为光的折射通常是未知的，波动的折射率场会导致未知的测量偏差。这尤其适用于磨削过程中的冷却润滑剂（CL）供应。由于流场测量对于冷却机制的基本理解和磨削过程的设计是必不可少的，因此该项目的目的是首次验证颗粒图像测速（PIV）用于冷却剂流场的研究，并使用它来澄清冷却剂流动行为与冷却性能之间的相关性。对于磨削过程中的近程PIV测量，基于光纤实验方法进行了深入的测量不确定度分析，以量化折射率变化的影响。用空间分辨率和时间分辨率测量了折射率场的变化对确定粒子位置和光片偏转的影响。通过时间平均和基于模型的校正，减小了流速场的测量误差。此外，还研究了平均折射率场能否在冷却剂平均射流几何形状的基础上建立模型，并利用几何光学方法估计粒子位置的系统偏差。需要在砂轮附近进行流量测量，以确定与冷却有关的CL流动特性。为此，采用了边界层优化的PIV评价方法，并分析了光片直接反射对砂轮表面的扰动影响，包括由此产生的间接流照明。在选定的工作点上，用PIV测量了刀工不接触的CL电源的流场，并分别用磨削模拟试验台测量了相应的冷却性能。目的是研究冷却性能与所研究的独立于工件的CL流之间的联系，而斜坡磨削试验用于检查结果是否可以直接转移到金属部件的加工过程中。为了加强对复杂CL流动现象的研究，分析了立体和时间分辨PIV测量的测量不确定度，并采用感觉砂轮和三分量测力仪研究了CL流动对磨削过程中热机械负荷集体的影响。

Optical flow measurement in two-phase flows is particularly challenging because refraction of light due to the usually unknown, fluctuating refractive index field can lead to unknown measurement deviations. This applies in particular to the cooling lubricant (CL) supply during grinding. Since flow field measurements are indispensable for a fundamental understanding of the cooling mechanism and thus for a design of the grinding process, the aim of the project is to validate particle image velocimetry (PIV) for the first time for the investigation of coolant flow fields and to use it to clarify the correlation between the coolant flow behavior and the cooling performance. For near-process PIV measurements during grinding, an in-depth measurement uncertainty analysis is carried out based on a fiber-optical, experimental approach in order to quantify the influence of refractive index variations. The effect of the refractive index field variations on the determination of the particle position as well as the deflection of the light sheet is measured with spatial and time resolution. The resulting measurement error of the flow velocity fields is reduced by means of temporal averaging and model-based correction. In addition, it is to be examined whether an average refractive index field can be modeled on the basis of the mean coolant jet geometry, which can be used by means of geometric optics to estimate systematic deviations of the particle position. Flow measurements near the grinding wheel are required to identify CL flow characteristics relevant for cooling. For this purpose, a boundary layer-optimized PIV evaluation is used and the disturbing influence of direct reflections of the light sheet on the grinding wheel surface is characterized, including the resulting indirect flow illumination. For selected operating points the resulting flow fields of the CL supply is measured by PIV without tool-workpiece contact and separately the corresponding cooling performance is measured by means of a grinding-analogy test rig. The aim is to investigate the connection between the cooling performance and the investigated CL flow that is independent from the workpiece, whereas ramp grinding tests are used to check whether the results can be directly transferred to the machining process of metallic components. For the enhanced study of complex CL flow phenomena, the measurement uncertainty of stereoscopic and time-resolved PIV measurements is analyzed, and a sensory grinding wheel and a 3-component dynamometer are implemented to investigate the effect of the CL flow on to the thermomechanical load collective during grinding.