In-process calibration of smart structures produced by incremental forming

Abstract

Smart load-bearing structures are created by forming integration of functional materials into passive metallic components with target-oriented pre-stress conditions by rotary swaging. Their sensory capability cannot only be used during the utilization but also during the manufacturing phase. Previous works demonstrated how this capability paves the way for efficient monitoring and controlling of the used integration process. In search of an even higher overall efficiency of the manufacturing chain, the subsequent costly calibration step deserves closer attention. Therefore, a cost- and time-efficient approach for the process-integrated calibration of a sensor-integrated structure is proposed in this paper. During the in-process calibration, the acting process forces are measured both in the integrated sensor and in a special-built clamping fixture. The measured data can be transferred into calibration slopes of the sensory structures. A suitable signal processing based on the process characteristics is performed to compensate interference effects on the raw signals. As a result, an accuracy of the calibration better than 2% of the nominal value compared to an offline standardized calibration is achieved with the in-line calibration method. Consequently, efficiency in the manufacturing of sensory structures is further boosted by avoidance of setup or logistical operations.

Sensor Integrated Load-Bearing Structures: Measuring Axis Extension with DIC-Based Transducers

“…For example, piezoelectric transducers have been integrated into metallic structures by die casting [38,39] or through additive manufacturing [40,41]. In this field, joining by forming has proven to be a particularly suitable and economic technology [42][43][44]. Here, transducers are pretensioned and integrated into hollow structures through force-or force-and form-fit joining by means of forming techniques, like rotary swaging (see Figure 1).…”

Methods and Technologies for Mastering Uncertainty

“…In this section, we present an approach to increase the efficiency in the production of sensory structures. By means of a suitable setup and process-adapted signal processing, it is possible to replace standard time-consuming downstream calibration processes with process-integrated calibration [6]. Once the sensory functional element is firmly integrated into the structure and the forming dies leave the joining zone (see Sect.…”

“…For this purpose, a special sensory clamping was designed as a machine-side reference point. By measuring the forming forces in both modes, namely in the integrated sensor element and at the machine-side reference point, a calibration is realised as shown in [6]. For the sensory clamping, strain gauge sensors are applied to measure the axial force on the clamping surface.…”

“…After the cooling-down of the joining zone in the tube, the adjusted pretension almost reaches a constant value (see also Fig. 5.34) and the dynamics of the forming dies are reduced to avoid resonance effects of the clamping [6]. The calibration phase can begin accordingly.…”

“…Once forming starts, the sinusoidal zero-point drift becomes greater as a result of bending the tube by the oscillating dies, and it becomes less uniform as a result of the high forming moments causing the workpiece to slip, see also [6,180]. Since neither the amplitude nor the angular frequency of the sinusoidal zero-point drift can be modulated, as the deformation behaviour is not precisely predictable, it is necessary to elaborate suitable approaches for the signal processing prior to calibration [6]. Based on the main characteristics of the incremental forming processes, i.e.…”