Thomas Herzog

This work addresses the critical concern of ensuring the quality of FFP2 medical masks weld seam, focusing on air-coupled ultrasonic testing (ACUT) as a non-contact inspection method. Through C-scan procedures and through-transmission techniques at varying frequencies, the research explores the acoustic properties of medical mask materials and welding seams. Attenuation and signal phase shift measurements reveal insights into ultrasound wave interactions with different components, aligning with slow longitudinal waves. Comparative analyses of welding seam inspection setups identify the normal through-transmission setup as practical. The innovative 2nd derivative technique of received signal amplitudes, proves effective in defect detection, presenting potential advancements in non-destructive testing for medical masks, ensuring swift and contamination-free inspection while preserving mask integrity.

Diese Untersuchungen befassen sich mit dem kritischen Anliegen, die Qualität medizinischer FFP-Masken sicherzustellen. Der Schwerpunkt liegt auf der Nutzung der luftgekoppelten Ultraschallprüfung (ACUT) als berührungslose Prüfmethode, da die konventio....

This work addresses the critical concern of ensuring the quality of FFP2 medical masks weld seam, focusing on Air-coupled ultrasonic testing (ACUT) as a non-contact inspection method. Through C-scan procedures and Through-transmission techniques at vary....

The welding manufacturing process is increasingly being used as an alternative joining method to sewing for functional textiles including for medical and protective wear, high-performance reinforcement textiles for fiber-reinforced plastics, film materials, and smart textiles. Ultrasonic (US) welding technology is a universally applicable cost-effective joining method for thermoplastic membranes. A key issue with the quality of the welded seam is that many of the faults are not visible on the membrane surface. The traditional quality control of the seam cannot be performed because it is done by destructive testing methods. Therefore 100% assurance of compliance of product safety produced at a production scale is not possible. The objective of the study is to develop a nondestructive (NDT) inline testing method for the quality control of welded seams during the continuous ultrasonic welding process. Currently, the quality control of Ultrasonic (US) welded seams is performed based on sample destructive standard tests, where the quality control of complete welded seams is not ensured. The air-coupled US sensors are used to detect imperfections in the welded seam. A variety of membrane materials with base fabric made of polyester and coated with PVC coating were tested during this research. A superimposed type of seam was produced longitudinally by PVC-coated textiles with smooth surfaced anvil wheels and was welded using a welding width of 10 mm. These coated materials were provided by industrial partners and are used in diverse technical textile applications. A process-integrated NDT test method was developed. The imperfections in welded seams were identified during a continuous US welding procedure with the help of air-coupled ultrasonic sensors by developing an inline test method. A prototype to realize inline monitoring during continuous ultrasonic welding was developed and tested. Faults of different widths were artificially produced during welding. The inline monitoring of welded seams with faults was successfully performed and analyzed. The developed process can further pave the way for the development of inline monitoring of welding seams with US sensors for textile membranes joined with a continuous US welding technology.

State‐of‐the‐art methods to monitor the degree of wetting of lithium‐ion batteries during production, which are applicable at an industrial scale, are not capable of determining the spatial electrolyte distribution in the porous network of electrodes and separator. Ultrasound can bridge this gap as it has previously been proven to be a suitable method to monitor or evaluate the infiltration of porous structures, for example, epoxy resin in carbon fiber composite. Herein, the acoustic properties of different battery cell materials are evaluated over a wide frequency range in both the dry and wet states, for the first time. Furthermore, a collection of input parameters, from the experimental setup and the evaluation routine to the acoustic parameters of the battery materials themselves, are provided. These parameters are needed for the adaptation of ultrasonic nondestructive testing to the monitoring of the wetting process of a lithium‐ion battery. Most importantly, this work demonstrates that a large change in the sound velocity (up to 100%) is observed when the porous structure of a lithium‐ion battery is filled with electrolyte and thus can serve as an appropriate evaluation figure of merit.

Ultrasonic transducers for NDE applications are commonly based on Lead Zirconate Titanate or PZT, an inorganic compound and ceramic perovskite material. Usually these conventional transducers are fabricated in piezo-composite technology in order to adapt the acoustic impedance of the active element to the specific material under test. For applications with low signal amplitudes, high electronic noise and small transducer elements, the performance of ultrasonic probes can be significantly enhanced by using Lead Magnesium Niobate-Lead Titanate (PMN-PT) instead of PZT. This single-crystal material offers significantly better piezo parameters and leads to a higher sensitivity and larger bandwidth. Similar to PZT it can also be fabricated in 1-3 piezo-composite technology. In a cooperation between Fraunhofer IKTS and Ibule Photonics, PMN-PT ultrasonic transducers are developed and optimized. As a result various single element and phased array transducers with improved performances are available. In the present paper several PMN-PT probes are presented and compared with identically constructed PZT transducers. Moreover, a short outlook to the next generation PIN-PMT-PT (lead indium niobate-lead magnesium niobate-lead titanate) NDE probes is given.

This paper describes the manufacturing and evaluation of a PMN-PT 1-3 composite based phased array ultrasonic probe for nondestructive evaluation (NDE). The electromechanical parameters of PMN-PT based 1-3 composites were measured and the composites were directly used in the acoustic stack manufacturing process (matching layer, etc.) similar to conventional PZT based probes. The performance of the phased array probes was measured by a PCUS® pro phased array electronic front end from Fraunhofer and compared with a PZT composite based phased array probe. The behavior of the single elements as well as the usability for a standard phased array sector scan was evaluated. The PMN-PT phased array probe shows a significant improvement of the sensitivity and a higher bandwidth.

The paper will report on the deposition and characterization of piezoelectric AlN and Al _X Sc _1-X N films. Potential applications of the films are in ultrasonic microscopy, energy harvesting and SAW/ BAW filters. Special focus will be on the characterization of the influences of sputter parameters on the structure and the piezoelectric properties of Al _X Sc _1-X N.

This paper reports on the deposition and characterization of piezoelectric AlN and Al_XSc_1-XN layers. Characterization methods include XRD, SEM, active thermo probe, pulse echo, and piezometer measurements. A special focus is on the characterization of AlN regarding the mechanical stress in the films. The stress in the films changed between -2.2 GPa (compressive) and 0.2 GPa (tensile) and showed a significant dependence on film thickness. The cause of this behavior is presumed to be the different mean grain sizes at different film thicknesses, with bigger mean grain sizes at higher thicknesses. Other influences on film stress such as the sputter pressure or the pulse mode are presented. The deposition of gradient layers using those influences allowed the adjustment of film stress while retaining the piezoelectric properties.

This paper will report on the deposition and characterization of piezoelectric AlN and Al _x Sc _1-x N layers. A special focus is on the characterization regarding the mechanical stress in the films. Potential applications of the films are in ultrasonic microscopy, energy harvesting and SAW/BAW filters. To demonstrate the potential in ultrasonic applications, the pulse echo method was used.