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

两相流中的光流测量尤其具有挑战性，因为由于通常未知的、波动的折射率场导致的光的折射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。由于流场测量对于基本了解冷却机制和设计磨削工艺是必不可少的，因此该项目的目的是首次验证粒子图像测速仪(PIV)用于研究冷却剂流场，并用它来阐明冷却剂流动行为和冷却性能之间的关系。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。用空间和时间分辨率测量了折射率场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修正，减小了由此产生的速度场测量误差。此外，还将研究平均折射率场是否可以根据平均冷却剂喷注几何形状来模拟，这可以用几何光学的方法来估计粒子位置的系统偏差。需要对砂轮附近的流量进行测量，以确定与冷却相关的CL流量特性。为此，使用了边界层优化的PIV评估，并表征了光片对砂轮表面的直接反射的干扰影响，包括由此产生的间接流动照明。对于选定的工作点，在没有刀具-工件接触的情况下，通过PIV测量CL供应的结果流场，并通过磨削模拟试验台分别测量相应的冷却性能。其目的是研究冷却性能与所研究的独立于工件的CL流动之间的关系，而斜面磨削试验则用于检查结果是否可以直接传递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，分析了立体式和时间分辨PIV测量的测量不确定度，并利用传感砂轮和三分量测功机研究了CL流动对磨削过程中热机械载荷集合的影响。

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.