Investigations on Material Loads during Grinding by Speckle Photography

Abstract

The knowledge of the loads occurring during a manufacturing process (e.g., grinding) and of the modifications remaining in the material is used in the concept of process signatures to optimize the manufacturing process and compare it with others (e.g., laser processing). The prerequisite for creating a process signature is that the loads can be characterized during the running process. Due to the rough process conditions, until now there is no in-process technique to measure the loads in the form of displacements and strains in the machined boundary zone. For this reason, the suitability of speckle photography is demonstrated for in-process measurements of material loads in a grinding process without cooling lubricant and the measurement results are compared with finite element method (FEM) simulations. As working hypothesis for the simulation it is assumed, that dry grinding is a purely thermally driven process. Despite the approximation by a purely thermal model with a constant heat source, the measured displacements differ only by a maximum of approximately 20% from the simulations. In particular, the strain measurements in feed speed direction are in good agreement with the simulation and support the thesis, that the dry grinding conditions used here lead to a primarily thermally affecting process.

Limiting Uncertainty Relations in Laser-Based Measurements of Position and Velocity Due to Quantum Shot Noise

“…Note that only one strain component is considered here as an example, and a more rigorous derivation of the three dimensional strain field from the displacement field or the spatial gradients of the displacement field, respectively, can be studied in [82,83]. According to the definition in Equation 40, the CRB of the strain component s x reads…”

4.1.1 Messung mechanischer Beanspruchungen in laufenden Schleifprozessen

“…Die Dehnungsanalysen zeigen, dass der Energieeintrag sehr lokal erfolgt. Da die Ergebnisse nur um 20 % von Simulationen unter Annahme einer konstant bewegten Wärmequelle [10] differieren, sind die eingebrachten Verformungen und Dehnungen im trockenen Schleifprozess offensichtlich in erster Linie thermischer Natur. Labormessreihen durch einen begrenzten Kühlschmierstofffilm verdeutlichen den Einfluss der Schichtdicke des Fluids auf die Speckle-Fotografie-Messung.…”

“…Um dann die Quadratwurzel zu lösen, wird folgende spektrale Zerlegung verwendet: ximum der y-Dehnung liegt am Ende der Kontaktfläche und steigt bis auf Werte von 16 x 10 -3 mm/mm an. Auch die gemessenen Dehnungen stehen mit einer Abweichung von weniger als 20 % in guter Übereinstimmung zu den Simulationen der Literatur [10]. Die Speckle-Fotografie ist also hinreichend robust, um auch unter den anspruchsvollen Bedingungen des trockenen Flachschleifens mit starkem Funkenflug In-Prozess-Messungen zu ermöglichen.…”

“…Speck le-fotografisch gemessene Verschiebungsfelder, jeweils in x-und y-Richtung Die gemessenen Verschiebungen decken sich im Vergleich (bis auf 20 % Abweichung) mit einem simulierten Schleifprozess bei gleichem Energieeintrag[10]. In der Simulation wurde der trockene Schleifprozess allerdings dadurch angenähert, dass sich eine konstante Wärmequelle über das Werkstück bewegt.…”

Induction of Highly Dynamic Shock Waves in Machining Processes with Multiple Loads and Short Tool Impacts

“…The loads in terms of the strains can be quantified during the production process by means of speckle photography [3,4]. With this method, the surface to be measured is illuminated with a laser and the evaluation areas in the speckle images taken with the camera-before and during the occurrence of the deformation-are correlated with each other [5,6].…”