Extensive Experimental Study on Diaphragm-Based Piezoelectric Microphone

1999 ◽  
Author(s):  
Meng-Nian Niu ◽  
Hong Zeng ◽  
Hai Yan ◽  
Eun Sok Kim
Keyword(s):  
Residual Stress ◽  
Experimental Study ◽  
Acoustic Pressure ◽  
Structural Integrity ◽  
Vertical Displacement ◽  
Active Area ◽  
Zno Film ◽  
Beam Laser ◽  
Acoustic Chamber ◽  
Focused Beam

Abstract This paper reports our extensive experimental study on diaphragm-based piezoelectric microphones fabricated on a silicon substrate. We have fabricated and carefully analyzed about 60 micromachined piezoelectric microphones (composed of piezoelectric ZnO film, insulating layers and electrodes) built on a low-stress silicon nitride diaphragm (with and without corrugation on the diaphragm and with five kinds of residual stress in the diaphragm). Microphone sensitivity is measured in an acoustic chamber with a B&K4135 microphone. Vertical displacement of a microphone diaphragm under an applied acoustic pressure is measured with a focused-beam laser Doppler displacement meter. Our results show that (1) corrugation releases both tensile stress and compressive stress effectively, and increases the center displacement greatly, (2) a good bending curvature in the active area is needed for a good microphone sensitivity, and (3) ZnO structural integrity is the major factor that affects the bending curvature in the active area.

Characterization of the Asphaltene Onset Region by Focused-Beam Laser Reflectance: A Tool for Additives Screening†

2009 ◽  
Vol 23 (3) ◽  
pp. 1155-1161 ◽  
Author(s):  
Javier Marugán ◽  
José A. Calles ◽  
Javier Dufour ◽  
Raúl Giménez-Aguirre ◽  
José Luis Peña ◽  
...  
Keyword(s):  
Beam Laser ◽  
Laser Reflectance ◽  
Focused Beam

Numerical Methods to Predict Distortion in Welded Components

2008 ◽  
Author(s):  
N. A. Leggatt ◽  
R. J. Dennis ◽  
P. J. Bouchard ◽  
M. C. Smith
Keyword(s):  
Residual Stress ◽  
Numerical Methods ◽  
Structural Integrity ◽  
Large Strain ◽  
Stress Fields ◽  
Specimen Thickness ◽  
Single Bead ◽  
Stress Profiles ◽  
Welding Processes ◽  
Integrity Assessments

Numerical methods have been established to simulate welding processes. Of particular interest is the ability to predict residual stress fields. These fields are often used in support of structural integrity assessments where they have the potential, when accurately characterised, to offer significantly less conservative predictions of residual profiles compared to those found in assessment codes such as API 579, BS7910 and R6. However, accurate predictions of residual stress profiles that compare favourably with measurements do not necessarily suggest an accurate prediction of component distortions. This paper presents a series of results that compare predicted distortions for a variety of specimen mock-ups with measurements. A range of specimen thicknesses will be studied including, a 4mm thick DH-36 ferritic plate containing a single bead, a 4mm thick DH-36 ferritic plate containing fillet welds, a 25mm thick 316L austenitic plate containing a groove weld and a 35mm thick esshete 1250 austenitic disc containing a concentric ring weld. For each component, distortion measurements have been compared with the predicted distortions with a number of key features being investigated. These include the influence of ‘small’ vs ‘large’ strain deformation theory, the ability to predict distortions using simplified analysis methods such as simultaneous bead deposition and the influence of specimen thickness on the requirement for particular analysis features. The work provides an extremely useful insight into how existing numerical methods used to predict residual stress fields can be utilised to predict the distortions that occur as a result of the welding fabrication process.

Experimental Study of Residual Stress Formation Mechanism of 7050 Aluminum Alloy Sheet by Laser Shock Processing

2016 ◽  
Vol 43 (7) ◽  
pp. 0702008
Author(s):  
曹宇鹏 Cao Yupeng ◽  
徐影 Xu Ying ◽  
冯爱新 Feng Aixin ◽  
花国然 Hua Guoran ◽  
周东呈 Zhou Dongcheng ◽  
...  
Keyword(s):  
Residual Stress ◽  
Experimental Study ◽  
Aluminum Alloy ◽  
Alloy Sheet ◽  
Laser Shock ◽  
Aluminum Alloy Sheet ◽  
Laser Shock Processing ◽  
7050 Aluminum Alloy ◽  
Stress Formation ◽  
Shock Processing

scholarly journals Experimental study on residual stress of milling medical magnesium alloy

2018 ◽  
Vol 397 ◽  
pp. 012046
Author(s):  
Yang Qiao ◽  
Peiquan Guo ◽  
Shouren Wang ◽  
Xuefeng Yang
Keyword(s):  
Residual Stress ◽  
Experimental Study ◽  
Magnesium Alloy

A Numerical Investigation into Residual Stress Characteristics in Laser Deposited Multiple Layer Waspaloy Parts

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
A. M. Kamara ◽  
S. Marimuthu ◽  
L. Li
Keyword(s):  
Residual Stress ◽  
Structural Integrity ◽  
Service Failures ◽  
Number Of Layers ◽  
Multiple Layer ◽  
Combined Use ◽  
Aerospace Sector ◽  
Finite Element Package ◽  
Stress Free State ◽  
Good Agreement

This paper reports an investigation into the residual stress generated with the laser direct metal deposition (LDMD) process and particularly that which arises from the deposition of a multiple-layer wall of Waspaloy on an Inconel 718 substrate. These Ni-based superalloys possess excellent strength and creep resistance at relatively high temperatures. These are attributes contributing to their extensive utilization in various applications in modern industry and particularly in the aerospace sector. Depending on its magnitude and nature (i.e., whether tensile or compressive), the residual stress generated in the combined use of these materials in an LDMD process affect interfacial bonding and structural integrity during the process, and it can also cause unpredicted in-service failures. Prediction of its distribution in the deposited structure is vital toward enhancing process optimization that could lead to its control. Using the ANSYS finite element package, this study investigated the residual stress characteristics in a 6 mm wide and 14 mm high Waspaloy wall that was built from the deposition of 20 layers each consisting of 6 parallel tracks. The predicted results were validated by published experimental data and showed very good agreement. The results indicated that irrespective of the position in the height of the wall, the stress along the length of the wall oscillates about a stress-free state. Along the height of the wall, the stress was found to vary with position. The wall is near stress-free close to the substrate, while, at positions close to the free surface, the stress was uniaxially tensile. The largely tensile stress in the beam scanning direction in the deposited wall increases with number of layers while the stress in the build-up direction in the wall is close to zero.

Structural Integrity of Penetration Nozzle of Reactor Pressure Vessel Head of PWR Plant

2008 ◽  
Author(s):  
Kiminobu Hojo ◽  
Naoki Ogawa ◽  
Yoichi Iwamoto ◽  
Kazutoshi Ohoto ◽  
Seiji Asada ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Field ◽  
Pressure Vessel ◽  
Structural Integrity ◽  
Complex Structure ◽  
Reactor Pressure Vessel ◽  
Reactor Pressure

A reactor pressure vessel (RPV) head of PWR has penetration holes for the CRDM nozzles, which are connected with the vessel head by J-shaped welds. It is well-known that there is high residual stress field in vicinity of the J-shaped weld and this has potentiality of PWSCC degradation. For assuring stress integrity of welding part of the penetration nozzle of the RPV, it is necessary to evaluate precise residual stress and stress intensity factor based on the stress field. To calculate stress intensity factor K, the most acceptable procedure is numerical analysis, but the penetration nozzle is very complex structure and such a direct procedure takes a lot of time. This paper describes applicability of simplified K calculation method from handbooks by comparing with K values from finite element analysis, especially mentioning crack modeling. According to the verified K values in this paper, fatigue crack extension analysis and brittle fracture evaluation by operation load were performed for initial crack due to PWSCC and finally structural integrity of the penetration nozzle of RPV head was confirmed.

Measurement and Modelling of Residual Stresses in Fracture Toughness Specimens Extracted From Large Components

2008 ◽  
Author(s):  
S. J. Lewis ◽  
S. Hossain ◽  
C. E. Truman ◽  
D. J. Smith ◽  
M. Hofmann
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Residual Stresses ◽  
Driving Force ◽  
Large Scale ◽  
Structural Integrity ◽  
Mechanical Load ◽  
Crack Driving Force ◽  
Neutron Diffraction Technique ◽  
Fracture Specimens

A number of previously published works have shown that the presence of residual stresses can significantly affect measurements of fracture toughness, unless they are properly accounted for when calculating parameters such as the crack driving force. This in turn requires accurate, quantitative residual stress data for the fracture specimens prior to loading to failure. It is known that material mechanical properties may change while components are in service, for example due to thermo-mechanical load cycles or neutron embrittlement. Fracture specimens are often extracted from large scale components in order to more accurately determine the current fracture resistance of components. In testing these fracture specimens it is generally assumed that any residual stresses present are reduced to a negligible level by the creation of free surfaces during extraction. If this is not the case, the value of toughness obtained from testing the extracted specimen is likely to be affected by the residual stress present and will not represent the true material property. In terms of structural integrity assessments, this can lead to ‘double accounting’ — including the residual stresses in both the material toughness and the crack driving force, which in turn can lead to unnecessary conservatism. This work describes the numerical modelling and measurement of stresses in fracture specimens extracted from two different welded parent components: one component considerably larger than the extracted specimens, where considerable relaxation would be expected as well as a smaller component where appreciable stresses were expected to remain. The results of finite element modelling, along with residual stress measurements obtained using the neutron diffraction technique, are presented and the likely implications of the results in terms of measured fracture toughness are examined.

An Efficient Modelling Approach for Predicting Residual Stress in Power-Beam Welds

2019 ◽  
Author(s):  
Graeme Horne ◽  
Danny Thomas ◽  
Andrew Collett ◽  
Andrew Clay ◽  
Martin Cott ◽  
...  
Keyword(s):  
Residual Stress ◽  
Structural Integrity ◽  
Welding Residual Stress ◽  
Contour Method ◽  
Element Analysis ◽  
Stress Measurements ◽  
316L Austenitic Stainless Steel ◽  
Important Input ◽  
Integrity Assessments ◽  
Modelling Approach

Abstract The prediction of welding residual stress in components is often an important input to structural integrity assessments. An efficient modelling approach was developed for predicting residual stress in power-beam welds, including validation against residual stress measurements. Specifically, sequentially coupled thermo-mechanical finite element analysis was conducted using a simplified heat source that was tuned to the observed fusion zone from a weld macrograph and thermocouple data for a series of electron beam welds in 316L austenitic stainless steel with a variety of geometries. The predicted residual stresses were compared with contour method and neutron diffraction residual stress measurements.

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