Crack Propagation and Detection in PZT-Multilayer Ceramics

2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000091-000098
Author(s):  
Tobias Kühnlein ◽  
Silvan Poller ◽  
Martin Rauscher ◽  
Alexander Klonczynski
Keyword(s):  
Impedance Spectroscopy ◽  
Crack Propagation ◽  
Fracture Strength ◽  
High Pressures ◽  
Mechanical Load ◽  
Matrix Cracking ◽  
Extreme Condition ◽  
Measurement Tool ◽  
Electrode Potentials ◽  
Resonance Frequencies

Piezo multilayer ceramics are increasingly used under extreme condition such as high pressures in engine injection systems. The mechanical stability and reliability of the ceramic multilayer is of major importance for proper operation. Critical functional defects are caused by material fracture and flaw extension in the device. The flaw propagation in PZT-multilayer ceramics under mechanical load was examined using impedance spectroscopy and three-point-bending studies. Initial flaws were generated by applying a sinus ac-field on the specimens. The cracks were successively promoted and after the release of the external mechanical load the impedance spectroscopy was conducted. As a measure for flaw extension, the shift in the resonance frequencies and the sub-resonance height of the impedance spectroscopy was used. A functional dependence of the resonance frequency and the phase shift on the crack length was found. The crack propagation was studied on flaws starting at the positive and negative electrode, respectively. The maximum fracture strength as well as the crack path depends on the electrode potentials. The variation in the fracture strength was caused by the different observed fracture mode: interface cracking, matrix-cracking and a combination of both. The morphology of the fracture faces was ascribed to an anisotropic behaviour, which is created by the sample processing, e.g. the poling process. A modified poling procedure with a lower poling temperature was analysed, which yielded a reduction of the anisotropy of the electrode strength. Impedance spectroscopy was found as a reliable measurement tool for automated flaw detection in PZT-multilayer ceramics.

Analyzing the influence of high electrode potentials on intrinsic properties of catalyst coated membranes using impedance spectroscopy

2016 ◽  
Vol 327 ◽  
pp. 526-534 ◽  
Author(s):  
Robert Alink ◽  
Martina Schüßler ◽  
Maximilian Pospischil ◽  
Denis Erath ◽  
Dietmar Gerteisen
Keyword(s):  
Impedance Spectroscopy ◽  
Intrinsic Properties ◽  
Electrode Potentials ◽  
Coated Membranes

scholarly journals Study on the High-Pressure Behavior of Goethite up to 32 GPa Using X-Ray Diffraction, Raman, and Electrical Impedance Spectroscopy

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 99 ◽  
Author(s):  
Ruilian Tang ◽  
Jiuhua Chen ◽  
Qiaoshi Zeng ◽  
Yan Li ◽  
Xue Liang ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Impedance Spectroscopy ◽  
Electrical Impedance ◽  
High Pressures ◽  
Structural Phase ◽  
Second Order ◽  
Electrical Impedance Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray

Goethite is a major iron-bearing sedimentary mineral on Earth. In this study, we conducted in situ high-pressure x-ray diffraction, Raman, and electrical impedance spectroscopy measurements of goethite using a diamond anvil cell (DAC) at room temperature and high pressures up to 32 GPa. We observed feature changes in both the Raman spectra and electrical resistance at about 5 and 11 GPa. However, the x-ray diffraction patterns show no structural phase transition in the entire pressure range of the study. The derived pressure-volume (P-V) data show a smooth compression curve with no clear evidence of any second-order phase transition. Fitting the volumetric data to the second-order Birch–Murnaghan equation of state yields V0 = 138.9 ± 0.5 Å3 and K0 = 126 ± 5 GPa.

Electrical conductivity of Alm82Py15Grs3 almandine-rich garnet determined by impedance spectroscopy at high temperatures and high pressures

2013 ◽  
Vol 608 ◽  
pp. 1086-1093 ◽  
Author(s):  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Jianjun Jiang ◽  
Keshi Hui ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Impedance Spectroscopy ◽  
High Temperatures ◽  
High Pressures

Acoustic emission detection and prediction of fatigue crack propagation in composite patch repairs using neural network

2016 ◽  
Vol 30 (1) ◽  
pp. 3-29 ◽  
Author(s):  
A Chukwujekwu Okafor ◽  
Navdeep Singh ◽  
Navrag Singh ◽  
Benjamin N Oguejiofor
Keyword(s):  
Acoustic Emission ◽  
Crack Propagation ◽  
Crack Length ◽  
Back Propagation ◽  
Fatigue Loading ◽  
Matrix Cracking ◽  
Composite Patch ◽  
Patch Repairs ◽  
Aluminum Panels ◽  
Emission Detection

This article presents the results of acoustic emission (AE) monitoring of crack propagation in 2024-T3 clad aluminum panels repaired with adhesively bonded octagonal and elliptical boron/epoxy composite patches using FM-73 adhesive under tension–tension fatigue loading. Two crack propagation gages and four broadband AE sensors were used to monitor crack initiation and propagation, respectively. The acquired AE signals were processed in time and frequency domain to identify sensor features correlated with fatigue cycle and crack propagation, which were used to train neural networks for predicting crack length. The results show that AE events are correlated with crack propagation, and crack propagation signals can be differentiated from signals due to matrix cracking, fiber breakage, and shear of the composite patch. Three back-propagation cascade feed-forward networks were trained to predict crack length using number of fatigue cycles, number of AE events, and number of fatigue cycles and number of AE events together as inputs, respectively. It was found that network with fatigue cycles as input gave good results, while the network with just AE events as input gave greater error. However, the network using both fatigue cycles and number of AE events as inputs to predict crack length gave much better results.

scholarly journals High-accuracy thrust measurements of the EMDrive and elimination of false-positive effects

2021 ◽  
Author(s):  
M. Tajmar ◽  
O. Neunzig ◽  
M. Weikert
Keyword(s):  
False Positive ◽  
Mechanical Load ◽  
Classical Mechanics ◽  
Double Pendulum ◽  
Positive Effects ◽  
Resonance Frequencies ◽  
Self Powered ◽  
Tapered Cavity ◽  
Propulsion Concept ◽  
Classical Radiation

AbstractThe EMDrive is a proposed propellantless propulsion concept claiming to be many orders of magnitude more efficient than classical radiation pressure forces. It is based on microwaves, which are injected into a closed tapered cavity, producing a unidirectional thrust with values of at least 1 mN/kW. This was met with high scepticism going against basic conservation laws and classical mechanics. However, several tests and theories appeared in the literature supporting this concept. Measuring a thruster with a significant thermal and mechanical load as well as high electric currents, such as those required to operate a microwave amplifier, can create numerous artefacts that produce false-positive thrust values. After many iterations, we developed an inverted counterbalanced double pendulum thrust balance, where the thruster can be mounted on a bearing below its suspension point to eliminate most thermal drift effects. In addition, the EMDrive was self-powered by a battery-pack to remove undesired interactions due to feedthroughs. We found no thrust values within a wide frequency band including several resonance frequencies and different modes. Our data limit any anomalous thrust to below the force equivalent from classical radiation for a given amount of power. This provides strong limits to all proposed theories and rules out previous test results by at least two orders of magnitude.

Structural characterization of semiconductor multi-layer pad

2021 ◽  
pp. 095440622110007
Author(s):  
Michele Calabretta ◽  
Alessandro Sitta ◽  
Salvatore Massimo Oliveri ◽  
Gaetano Sequenzia
Keyword(s):  
Crack Propagation ◽  
Mechanical Load ◽  
Semiconductor Industry ◽  
Current Trend ◽  
Wire Bonding ◽  
Film Deposition ◽  
Experimental Methodology ◽  
Flat Punch ◽  
The Impact

Structural mechanics and mechanical reliability issues are becoming more and more challenging in the semiconductor industry due to the continuous trend of the device dimensional shrinkage and simultaneous increased operative temperature and power density. As main consequence of the downsizing and more aggressive operative conditions, the mechanical robustness assessment is now having a central role in the device engineering and assessment phase. The risk of mechanical crack in the brittle oxide layers, which are embedded in pad stacks, increases during the device manufacturing processes such as the electrical wafer testing and during wire bonding. This risk increases with the presence of intrinsic mechanical stress in individual layers resulting from the metal grain growth mechanisms, the stack layers’ interfacial mismatches in coefficients of thermal expansion and the temperature stress induced by doping diffusion and film deposition. The current trend of innovation in the electronic industry is going over the semiconductor material itself and it is now impacting the improvement of the Back-End of Line. Key actors are becoming the interactions between the semiconductor die and the device packaging such as adhesion layers, barriers and metal stacks. In the present work, different pad structures have been structurally analyzed and benchmarked. The experimental characterization of the pad structures has been done through a flat punch nano-indentation to investigate on the mechanical strength and the crack propagation. The considered mechanical load reproduces the vertical impact force applied during wire bonding process to create the bond-pad electrical interconnection. The obtained testing results have been compared to finite element models to analyze the stress distribution through the different layers’ stacks. Scope of this work is to demonstrate the validity of the proposed integrated numerical/experimental methodology, showing the impact of the metal connections layouts by the analysis of the stress notch factors and crack propagation behaviour.

Impedance Spectroscopy at Super High Pressures

2001 ◽  
pp. 131-141 ◽  
Author(s):  
A. N. Babushkin ◽  
Y. A. Kandrina ◽  
O. L. Kobeleva ◽  
S. N. Schkerin ◽  
Y. Y. Volkova
Keyword(s):  
Impedance Spectroscopy ◽  
High Pressures

Self-Healing in Plants as a Model for Self-Repairing Elastomer Materials

2011 ◽  
Vol 2 (4) ◽  
pp. 149-156
Author(s):  
A Nellesen ◽  
M. von Tapavicza ◽  
J. Bertling ◽  
A.M. Schmidt ◽  
G. Bauer ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Mechanical Stress ◽  
Mechanical Load ◽  
Early Stage ◽  
Maximum Load ◽  
Self Healing ◽  
Plant Biomechanics ◽  
Micro Cracks ◽  
Average Maximum ◽  
Fatigue Fractures

Polymer based elements are frequently subject to high mechanical load. It is well known, that such components can spontaneously break although the mechanical stress has not reached the average maximum load. These fatigue fractures are caused by micro-cracks. A smart approach would be to implement a self-healing function that is able to heal a crack in an early stage and thus avoid crack propagation. Fraunhofer UMSICHT and the Plant Biomechanics Group Freiburg together with co-operation partners develop biomimetic self-healing elastomers having the capability to repair micro-cracks automatically without any intervention from outside.

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