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

Tausendfreund, Andreas; Stöbener, Dirk; Fischer, Andreas

doi:10.3390/app9112293

“…In terms of its maximum achievable resolution, the method is limited only by Heisenberg's uncertainty principle [10]. The in-process capability and suitability of the speckle photography method for two-dimensional deformation measurement in the image plane with resolutions of less than 20 nm [11] has already been demonstrated in several manufacturing applications [12,13,14,15]. However, since mechanical machining causes at least a biaxial stress state and, thus, a triaxial strain state in the workpiece via the machining forces, a reconstruction of three-dimensional deformation fields is required for a complete metrological description of the loads.…”

Section: Introductionmentioning

confidence: 99%

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

Tausendfreund¹,

Stöbener²,

Fischer³

2021

Preprint

Self Cite

View full text Add to dashboard Cite

In the concept of the process signature, the relationship between a material load and the modification remaining in the workpiece is used to better understand and optimize manufacturing processes. The basic prerequisite for this is to be able to measure the loads occurring during the machining process in the form of mechanical deformations. Speckle photography is suitable for this in-process measurement task and is already used in a variety of ways for in-plane deformation measurements. The shortcoming of this fast and robust measurement technique based on image correlation techniques is that out-of-plane deformations in the direction of the measurement system cannot be detected and increases the measurement error of in-plane deformations. In this paper, we investigate a method that infers local out-of-plane motions of the workpiece surface from the decorrelation of speckle patterns and is thus able to reconstruct three-dimensional deformation fields. The implementation of the evaluation method enables a fast reconstruction of 3D deformation fields, so that the in-process capability remains given. First measurements in a deep rolling process show that dynamic deformations underneath the die can be captured and demonstrate the suitability of the speckle method for manufacturing process analysis.

show abstract

“…In terms of its maximum achievable resolution, the method is limited only by Heisenberg's uncertainty principle [10]. The inprocess capability and suitability of the speckle photography method for two-dimensional deformation measurement in the image plane with resolutions of less than 20 nm [11] has already been demonstrated in several manufacturing applications [12][13][14][15]. However, since mechanical machining causes at least a biaxial stress state and, thus, a triaxial strain state in the workpiece via the machining forces, a reconstruction of three-dimensional deformation fields is required for a complete metrological description of the loads.…”

Section: Introductionmentioning

confidence: 99%

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

Tausendfreund

¹

,

Stöbener

²

,

Fischer

³

2021

Self Cite

View full text Add to dashboard Cite

In the concept of the process signature, the relationship between a material load and the modification remaining in the workpiece is used to better understand and optimize manufacturing processes. The basic prerequisite for this is to be able to measure the loads occurring during the machining process in the form of mechanical deformations. Speckle photography is suitable for this in-process measurement task and is already used in a variety of ways for in-plane deformation measurements. The shortcoming of this fast and robust measurement technique based on image correlation techniques is that out-of-plane deformations in the direction of the measurement system cannot be detected and increases the measurement error of in-plane deformations. In this paper, we investigate a method that infers local out-of-plane motions of the workpiece surface from the decorrelation of speckle patterns and is thus able to reconstruct three-dimensional deformation fields. The implementation of the evaluation method enables a fast reconstruction of 3D deformation fields, so that the in-process capability remains given. First measurements in a deep rolling process show that dynamic deformations underneath the die can be captured and demonstrate the suitability of the speckle method for manufacturing process analysis.

show abstract

“…Moreover, the spatial resolution for deformation detection and strain calculation is limited by the surface feature dimensionality. Laser speckle photography [12] transgresses these limitations and is already used for tensile tests [13] as well as an in-process measuring method for the induced deformation during machining [14,15]. Speckle photography is physically limited only by Heisenberg's uncertainty principle and the respective measurement uncertainty limit can be derived with the Cramér-Rao bound [16,17].…”

Section: Introductionmentioning

confidence: 99%

Uncertainty and Resolution of Speckle Photography on Micro Samples

Alexe

¹

,

Tausendfreund

²

,

Stöbener

³

et al. 2020

Self Cite

View full text Add to dashboard Cite

The efficient development of new materials with defined properties requires fast methods of testing low volumes of material, such as a high-throughput investigation of spherical metallic micro samples with varying compositions and structuring treatments. A classical material testing method for macro samples, the tensile test cannot be employed for analyzing the mechanical properties of spherical samples with diameters below 1 mm since there are currently no methods for holding and stretching them. A combination between the incremental electrohydraulic extrusion as stress actuation unit and the speckle photography as strain measuring method is presented for obtaining the required mechanical characteristics. Positive longitudinal strain is generated at stepwise extrusion through < 1 mm wide forming channels using a liquid punch and the deformation is observed in situ after each forming step at the interface between the micro sample and a transparent window integrated into the forming die. The occurring local strain fields with a lateral extension down to 100 µm and high gradients require displacement measurements with high lateral resolution over a large range of local dislocations between 0.1 and > 10 µm. It is unknown, whether the speckle strain measuring method is able to provide the necessary low uncertainty for the required resolution in the whole measuring range. Therefore, theoretical and experimental investigations of the deformation measurability using the speckle correlation method are presented, showing that local displacements up to 10 µm can be measured with a spatial resolution between 3 and 10 µm depending on the displacement size. The dominant effect influencing the measurement uncertainty for displacements at this high spatial resolution is the speckle noise, resulting into measurement uncertainties of less than 100 nm. Hence, speckle photography is shown to be applicable for tensile test on micro samples.

show abstract

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

Cited by 6 publications

References 14 publications

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

In-Process Measurement of Three-Dimensional Deformations Based on Speckle Photography

Uncertainty and Resolution of Speckle Photography on Micro Samples

Contact Info

Product

Resources

About