Strength and Fractography of Piezoceramic Multilayer Stacks

2005 ◽  
Vol 290 ◽  
pp. 46-53 ◽  
Author(s):  
Peter Supancic ◽  
Z. Wang ◽  
Walter Harrer ◽  
K. Reichmann ◽  
Robert Danzer
Keyword(s):  
Low Voltage ◽  
Piezoelectric Actuators ◽  
Life Time ◽  
Axial Direction ◽  
Tensile Tests ◽  
Mechanical Stresses ◽  
Automotive Applications ◽  
Fracture Surfaces ◽  
Multilayer Stacks ◽  
Metallic Electrodes

Modern low-voltage piezoelectric actuators consist of a stack of piezoceramic layers (PZT) with metallic electrodes in between. Due to the use of these parts in automotive applications, a big but sensitive market is opened. During application mechanical stresses are an inherent loading of these electro-mechanical converter components. Therefore some strength of the actuators is necessary to guarantee a demanded life time. Bending and tensile tests were performed on commercial components to measure the strength in axial direction. Fracture surfaces were investigated with the methods of fractography to get information about the weakest links in the microstructure.

Lifetime Distribution Estimation of Boot Seals in Automotive Applications by Bayesian Method

2006 ◽  
Vol 129 (3) ◽  
pp. 275-282 ◽  
Author(s):  
Fabrice Guerin ◽  
Ridha Hambli
Keyword(s):  
Finite Element ◽  
Bayesian Method ◽  
Life Time ◽  
Automotive Applications ◽  
Fatigue Lifetime ◽  
Time Prediction ◽  
Steering Mechanism ◽  
Market Requirements ◽  
Distribution Parameters ◽  
Lifetime Testing

The constantly increasing market requirements of high quality vehicles ask for the automotive manufacturers to perform lifetime testing to verify the reliability levels of new products. A common problem is that only a small number of examples of a component of system can be tested. In the automotive applications, mechanical components subjected to cyclic loading have to be designed against fatigue. Boot seals are used to protect velocity joint and steering mechanisms in automobiles. These flexible components must accommodate the motions associated with angulation of the steering mechanism. Some regions of the boot seal are always in contact with an internal metal shaft, while other areas come into contact with the metal shaft during angulation. In addition, the boot seal may also come into contact with itself, both internally and externally. The contacting regions affect the performance and longevity of the boot seal. In this paper, the Bayesian estimation of lognormal distribution parameters (usually used to define the fatigue lifetime of rubber components) is studied to improve the accuracy of estimation in incorporating the available knowledge on the product. In particular, the finite element results and expert belief are considered as prior knowledge. For life time prediction by finite element method, a model based on Brown–Miller law was developed for the boot seal rubber-like material.

Deposition Effects on the Ultimate Strength of Tungsten Alloy

2014 ◽  
Vol 887-888 ◽  
pp. 857-860
Author(s):  
Ying Ge Xu ◽  
Ze Wei Wu
Keyword(s):  
Mechanical Properties ◽  
Ultimate Strength ◽  
Temperature Effects ◽  
Tensile Tests ◽  
Tungsten Alloy ◽  
Fracture Modes ◽  
Fracture Surfaces ◽  
Temperature Ranges

The temperature effects on the ultimate strength of 93WNiFe alloy have been investigated systematically through tensile tests, fracture surfaces and microstructure. The temperature ranges from 10 to 900 degrees. The results show that the ultimate strength decreases with the increase of temperature, and there is a platform in 300 to 600 degrees .The deposition has been observed in fracture surfaces from 500 to 600 degrees. The fracture modes influence the ultimate strength,deposition can improve mechanical properties of W-W and W-M interfaces, it is the cause of the ultimate strength platform.

A Case for High Temperature, High Voltage SiC Bipolar Devices

2007 ◽  
Vol 556-557 ◽  
pp. 687-692 ◽  
Author(s):  
Anant K. Agarwal
Keyword(s):  
High Temperature ◽  
High Voltage ◽  
Low Voltage ◽  
Schottky Diodes ◽  
Life Time ◽  
Extreme Environment ◽  
Junction Temperature ◽  
Current Gain ◽  
Pin Diodes ◽  
Bipolar Devices

The last three years have seen a rapid growth of 600 V and 1200 V SiC Schottky diodes primarily in the Power Factor Correction (PFC) circuits. The next logical step is introduction of a SiC MOSFET to not only further improve the power density and efficiency of the PFC circuits but also to enable the entry of all SiC power modules in Pulse Width Modulated (PWM) based power converters such as motor control in 600-1200 V range. The combination of SiC MOSFET and Schottky diodes will offer 60-80% lower losses in most low voltage applications at normal operating temperatures (< 200°C) where no significant improvements in packaging are required. This will cover most commercial applications with the exception of those having to function under extreme environment (>200°C) such as applications in automotive, aerospace and oil/gas exploration. For these high temperature applications, a case can be made for 600 - 2000 V Bipolar Junction Transistors (BJTs) and PiN diodes provided we do our homework on high temperature packaging. A number of interesting device related problems persist in bipolar devices such as forward voltage increase in PiN diodes and current gain degradation in BJTs. For very high voltage (>10 kV) applications such as those found in utilities (Transmission and Distribution), Large Drives and Traction, a case can be made for >10 kV PiN diodes, IGBTs, Thyristors and GTOs. While IGBTs will be restricted to <200°C junction temperature, the PiN diodes, Thyristors and GTOs may be operated at >250°C junction temperature provided that the high temperature, high voltage packaging issues are also addressed. Significant progress has been made in the development of the p-channel IGBTs and GTOs. The main issues seem to be the VF degradation due to stacking fault formation and improvement of minority carrier life-time.

scholarly journals Considerations on design, development and testing of Electrical Machines for automotive HVAC

2020 ◽  
Vol 322 ◽  
pp. 01042
Author(s):  
Radu Martis ◽  
Florin Pop-Piglesan ◽  
Sorin Cosman ◽  
Claudia Martis
Keyword(s):  
Electric Vehicles ◽  
Test Bench ◽  
Low Voltage ◽  
Hvac Systems ◽  
Electrical Machines ◽  
Automotive Applications ◽  
Design Development ◽  
Driving System ◽  
Wide Range ◽  
Driving Range

HVAC represents one of the highest energy consumer in a vehicle and for full electric vehicles, the design of HVAC and the dimensioning of its driving system is of utmost importance in order to avoid the limitation of driving range. Due to its advantages, especially when it comes to power density, PMSM is one of the most used electrical machines for a wide range of automotive applications, including HVAC systems. The paper presents the generation of the requirements, design, analysis and HiL testing of a PMSM for HVAC applications. The challenge is to develop a machine answering to the requirements for an electric vehicle HVAC at low- voltage. An experimental model of the machine was tested using a test- bench, based on HiL techniques.

Experimental Determination of Layer-Specific Hyperelastic Parameters of Human Descending Thoracic Aortas

2019 ◽  
Author(s):  
Isabella Bozzo ◽  
Marco Amabili ◽  
Prabakaran Balasubramanian ◽  
Ivan Breslavsky ◽  
Giovanni Ferrari
Keyword(s):  
Storage Modulus ◽  
Thoracic Aorta ◽  
Loss Tangent ◽  
Viscoelastic Model ◽  
Viscoelastic Behavior ◽  
Axial Direction ◽  
Maxwell Model ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Descending Thoracic Aorta

Abstract Heart disease is the second leading cause of death in Canada resulting in $20.9 billion annual healthcare expenditures [1,2]. Understanding the mechanics of the human descending thoracic aorta is fundamental for comprehending the development of pathologies and improving surgical prostheses. This study presents hyperelastic and viscoelastic material characterizations of the human descending thoracic aorta from twelve different donors, with a mean age of 49.4 years. The specimens were dissected into the three constituent layers: intima, media and adventitia. Evaluating the layer-specific opening angles led to the computation of the circumferential residual stresses. Uniaxial tensile tests of each layer, in both the circumferential and axial direction, were used to model the hyperelastic behavior according to the Gasser-Ogden-Holzapfel model (GOH). The storage modulus and loss tangent for the layers were obtained from uniaxial harmonic excitations at varied frequencies, to model the viscoelastic behavior with the generalized Maxwell model. The results showed a positive correlation between age and stiffness for all layers, both axially and circumferentially. Similar loss tangent values were found across the three layers. A large increase in the storage modulus from static to dynamic experiments further corroborates the importance of a viscoelastic model of the aorta, rather than solely hyperelastic.

Fracture Behaviors of the Rolled Isotactic Polypropylene

2014 ◽  
Vol 529 ◽  
pp. 237-241
Author(s):  
Juan Jia ◽  
Shuang Xin Liu ◽  
Dierk Rabbe
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Isotactic Polypropylene ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Total Elongation ◽  
Tensile Fracture ◽  
Tensile Sample ◽  
Fracture Surfaces ◽  
Fracture Behaviors

The mechanical properties of the rolled isotactic polypropylene and the morphology of fracture surfaces were measured and observed by tensile tests and the scanning electron microscopy. And then the tensile fracture behaviors along the rolling and transvers directions of the rolled samples were analyzed. After rolling, strong anisotropy mechanical properties occurred along the rolling and transverse directions: high tensile strength with low total elongation along the rolling direction and low tensile strength with high total elongation along the transverse direction. After tensile test, three characteristic structures were found on the fracture surfaces. The tensile fracture behavior of the rolled samples is: stress concentration happens on the edge of tensile sample and then fracture develops to the center part of the tensile sample. When the fracture is big enough, the tensile sample will be failed very quickly.

Role of Iron-Rich Phases and Porosity on the Ductility of Rheocast Al-Mg-Si-Alloys

2022 ◽  
Vol 327 ◽  
pp. 65-70
Author(s):  
Qing Zhang ◽  
Stefan Jonsson ◽  
Arne K. Dahle ◽  
Anders E.W. Jarfors
Keyword(s):  
Quantitative Analysis ◽  
Tensile Tests ◽  
Intermetallic Phases ◽  
The Other ◽  
Homogeneous Microstructure ◽  
Fracture Surfaces ◽  
Other Hand ◽  
Primary Particles ◽  
Semi Solid

Treatment of the slurry is important during RheoMetalTM casting. In this work, semi-solid slurries were prepared under different stirring intensities, using two types of stirrers: a naked rod (for regular stirring) and a rod with two blades (for intensified stir). Tensile tests were performed, investigating fracture surfaces, as well as metallographic samples. The results show that intensified stir produces castings with finer primary particles and a more homogeneous microstructure. On the other hand, more faceted Fe-rich phases are found along the α-Al grains boundary as well, due to the dissolution of Fe from the stirrers. Moreover, for intensified stir castings, the porosity found on the fracture surfaces are smaller, while more brittle eutectic phases and second (intermetallic) phases, especially Fe-rich phases, are observed. Consequently, the castings with intensified stir show worse ductility. Finally, a quantitative analysis was made regarding ductility, affected both by porosity and the presence of Fe-rich phases.

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