Joining by forming of piezoceramic macro-fiber arrays within micro-structured surfaces of aluminum sheets

Abstract

Functional integration of smart materials in sheet metal enables lightweight composite parts which are enhanced by new functionalities. Locally integrated piezoceramic/ metal composites consist of a prefabricated array of ten parallel piezoceramic macro-fibers with dimensions of 0.277 mm by 0.232 mm by 10 mm which are joined in micro-formed cavities within the surface of an aluminum sheet metal. By the use of joining by forming, the interference- fit, preload and form-fit of macro-fiber arrays are achieved in a single process step. The paper describes investigations of the joining by forming process in formal planned experiments using the design of experiments method. The influence of the dimensions and preparation of the joining partners, the maximum forming force and the velocity of the forming stamp are varied. The interference- fit and preload depend on the maximum forming force. In contrast, the quality of the form-fit is primarily related to the geometric dimensions and the forming force. Fiber fractures and incipient cracks are the major failure mechanisms during joining by forming of the macro-fibers. The number of cracks is significantly reduced by the use of lower die velocities, lower maximum joining forces and the introduction of additional geometric elements in the microstructure of the metal surface. Concluding, constraints with regard to the design of parts and the process are derived from the experiments

Sensor-integrated structures in mechanical engineering: challenges and opportunities for mechanical joining processes

“…For embedding micro-piezo modules into micro-structured cavities within the surface of an aluminum sheet, Schubert et al investigated the use of pressing to join the micropiezo modules to the aluminum sheet via force fit [24] and via form-and force-fit [25]. See Fig.…”

“…5, as the aluminum webs are compressed by the pressing force, the gaps between the host structure and the piezo elements are filled. After the pressing force is removed, spring back of the elastic deformation of the structure occurs, and a certain amount of force-fit joint remains to preload the piezoelectric elements [25]. To ensure the setting of sufficient preload and to detect faulty joining, an approach for in-process monitoring of the preload based on the intensity of the resonance peak without overload is presented by Müller et al [26].…”

“…To Fig. 5 Joining by forming piezo ceramic fibres in metal according to [25]: (left) assembly and joining by forming, (right) joined part Fig. 6 Sensory structures produced by rotary swaging.…”

In-process calibration of smart structures produced by incremental forming

“…Schubert et al introduce the integration of micro-piezo modules in micro-structured cavities within the surface of an aluminum sheet, prior to generating a force fit [12] and a form and force fit joint [13] by pressing.…”

Monitoring concept for structural integration of PZT-fiber arrays in metal sheets: a numerical and experimental study

“…The particular attention of the research is given to the process step joining by forming of the PZT fibers in the aluminum sheets. The focus in this step is on the monitoring of the fibers during the joining operation rather than the mechanical integration technology of the piezoceramic fibers itself, which was investigated earlier and described in [5]. The change of the electromechanical condition during the joining operation shall be used to develop a monitoring method.…”