The assessment of flaws in a high stress concentration region

1994 ◽  
Vol 57 (2) ◽  
pp. 201-206 ◽  
Author(s):  
Hong Qin ◽  
Ying Tan ◽  
Liankui Sun
Keyword(s):  
Stress Concentration ◽  
High Stress ◽  
Concentration Region ◽  
High Stress Concentration ◽  
Stress Concentration Region

An Experimental Study of Dropped Ply Region in Composite

2006 ◽  
Vol 326-328 ◽  
pp. 1769-1772
Author(s):  
Chun Wang Zhao ◽  
Yong Ming Xing
Keyword(s):  
Experimental Study ◽  
Stress Concentration ◽  
Failure Mechanisms ◽  
Experimental Results ◽  
Epoxy Composites ◽  
Moire Interferometry ◽  
Concentration Region ◽  
Micro Cracks ◽  
Stress Concentration Region ◽  
Mechanical Study

A micro mechanical study of Carbon/Epoxy composites with internally dropped plies has been made using micro-moiré interferometry. The experimental results show that there is a stress concentration region before the dropped ply. Micro cracks were initiated and propagated in this region. Two failure mechanisms in the dropped ply region were observed.

Advancements in Micro-Structure with Multiple Stress Concentration Region for Bionic Vector Hydrophone

2015 ◽  
Vol 645-646 ◽  
pp. 555-560
Author(s):  
Guo Jun Zhang ◽  
Peng Zhao ◽  
Wen Dong Zhang
Keyword(s):  
Stress Concentration ◽  
Constant Force ◽  
Ansys Software ◽  
Micro Structure ◽  
Concentration Region ◽  
Multiple Stress ◽  
Upper Limit ◽  
Stress Concentration Region ◽  
Vector Hydrophone ◽  
Different Shapes

The method of Multiple Stress Concentration Regions (MSCRs) on the surface of MEMS Silicon micro-structure is introduced in order to enhance the sensibility of the hair vector hydrophone without reducing the working bandwidth. The MSCRs with the thickness and width smaller than the rest of the cantilever can produce localized stress concentration when constant force is applied on the structure. ANSYS software has been used as a tool to analyze the effect of different shapes and dimensions on the performance of the micro-structure. The optimum MSCR has been obtained. Results show that compared with the ordinary structure, the sensitivity of the micro-structure with MSCR can be increased by 1.5 times, and the upper limit of bandwidth can be improved from 337Hz to 500Hz. This paper provides a new method to resolve contradiction between the sensitivity and working bandwidth.

Fracture Assessments of High Pressure Vessel Components Having Longitudinal Holes

2017 ◽  
Author(s):  
Yu Xu ◽  
Kuao-John Young
Keyword(s):  
High Pressure ◽  
Stress Concentration ◽  
Fracture Mechanics ◽  
Pressure Vessel ◽  
High Stress ◽  
Pressure Vessels ◽  
Crack Face ◽  
High Pressure Vessel ◽  
High Stress Concentration ◽  
Critical Locations

Small size longitudinal holes are common in components of high pressure vessels. In fracture mechanics evaluation, longitudinal holes have not drawn as much attention as cross-bores. However, longitudinal holes become critical at certain locations for such assessments because of high stress concentration and short distance to vessel component wall. The high stress concentration can be attributed to three parts: global hoop stress that is magnified by the existence of the hole, local stresses due to pressure in the hole, and crack face pressure. In high pressure vessel design, axisymmetric models are used extensively in stress analyses, and their results are subsequently employed to identify critical locations for fracture mechanics evaluation. However, axisymmetric models ignore longitudinal holes and therefore cannot be used to identify the critical location inside the holes. This paper is intended to highlight the importance of including longitudinal holes in fracture mechanics evaluation, and to present a quick and effective way of evaluating high stress concentration at a longitudinal hole using the combined analytical solutions and axisymmetric stress analysis results, identifying critical locations and conducting fracture mechanics evaluation.

Reduction of Stress Concentration Due to Interference Fits in an Infinite Plate With Two Holes

1978 ◽  
Vol 100 (4) ◽  
pp. 369-373
Author(s):  
T. Iwaki ◽  
K. Miyao
Keyword(s):  
Exact Solution ◽  
Stress Concentration ◽  
Elastic Properties ◽  
High Stress ◽  
Infinite Plate ◽  
Concentration Effects ◽  
Numerical Examples ◽  
High Stress Concentration ◽  
External Forces

This paper contains an exact solution for stresses which are produced in an infinite plate with two holes of different sizes by interference fits. It is assumed that the plate and the interference-fitted ring have the same elastic properties and are perfectly bonded to each other. Numerical examples of the solution are worked out and the interference fits are found useful for reducing the high-stress concentration effects which are induced in an infinite plate with two holes by external forces.

scholarly journals Study on the Mechanism and Control of Rock Burst of Coal Pillar under Complex Conditions

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Xingping Lai ◽  
Huicong Xu ◽  
Jingdao Fan ◽  
Zeyang Wang ◽  
Zhenguo Yan ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Rock Burst ◽  
Coal Mine ◽  
High Stress ◽  
Coal Pillar ◽  
Vertical Stress ◽  
Body Area ◽  
High Stress Concentration ◽  
Solid Coal ◽  
Working Face

In order to explore the mechanism of coal pillar rock burst in the overlying coal body area, taking W1123 working face of Kuangou Coal Mine as the engineering background, the full mining stage of W1123 is simulated by FLAC3D. It is found that the high stress concentration area has appeared on both sides of the coal pillar when W1123 does not start mining. With the advance of the working face, the high stress concentration area forms X-shaped overlap. There is an obvious difference in the stress state between the coal pillar under the solid coal and the coal pillar under the gob in W1123. The concrete manifestation is that the vertical stress of the coal pillar below the solid coal is greater than the vertical stress of the coal pillar below the gob. The position of the obvious increase of the stress of the coal pillar in the lower part of the solid coal is ahead of the advancing position of the working face, and the position of the obvious increase of the stress of the lower coal pillar in the gob lags behind the advancing position of the working face. At the same time, in order to accurately reflect the true stress environment of coal pillars, the author conducted a physical similarity simulation experiment in the laboratory to study the local mining process of the W1123 working face, and it is found that under the condition of extremely thick and hard roof, the roof will be formed in the gob, the mechanical model of roof hinged structurer is constructed and analyzed, and the results show that the horizontal thrust of roof structure increases with the increase of rotation angle. With the development of mining activities, the self-stable state of the high stress balance in the coal pillar is easily broken by the impact energy formed by the sudden collapse of the key strata. Therefore, the rock burst of coal pillar in the overlying coal body area is the result of both static load and dynamic load. In view of the actual situation of the Kuangou Coal Mine, the treatment measures of rock burst are put forward from the point of view of the coal body and rock mass.

Underfill Design for Low-k Dielectrics and Lead Free Applications

2010 ◽  
Vol 2010 (DPC) ◽  
pp. 001465-001485
Author(s):  
Brian Schmaltz ◽  
Yukinari Abe ◽  
Kazuyuki Kohara
Keyword(s):  
Stress Concentration ◽  
Dielectric Layer ◽  
Failure Modes ◽  
High Stress ◽  
High Strength ◽  
Lead Free ◽  
Typical Result ◽  
High Stress Concentration ◽  
Technology Nodes ◽  
Low K

As technology nodes progress to 32/28nm and beyond underfill materials are presented with the significantly challenging task of maintaining bump protection while ensuring ultra low-K dielectric (ULK/ELK) integrity. This challenge is further complicated by the trend toward RoHS compliancy(lead-free) and a ever increasing die size. Through extensive research and testing, several specifically formulated underfill materials were determined acceptable solutions for these complex issues. As technology nodes progress to smaller process generations a high stress concentration is seen at the dielectric layer during thermal cycling. This stress is a typical result of a high glass transition temperature (Tg) / high strength material that often leads to a cracking failure mode of the thin dielectric layer. Too low of a Tg presents a high stress concentration on the bumps which once again constitutes failure, this time however the crack is typically seen at the bump location. This high stress concentration seen at the bumps is more significant when lead free bumps are considered due to their inherent fragile nature. Underfill materials must now be specifically formulated and optimized to solve these failure modes for a large variable of package types. This paper will discuss solutions to typical failure modes currently seen with reliability testing of present and future technologies.

Development of Design Curve for Sweepolet Subjected to Acoustic Induced Vibration

2016 ◽  
Author(s):  
Yuqing Liu ◽  
Philip Diwakar ◽  
Dan Lin ◽  
Ismat Eljaouhari ◽  
Ajay Prakash
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Fatigue Failure ◽  
High Stress ◽  
Peak Stress ◽  
Acoustic Energy ◽  
Piping System ◽  
Element Analysis ◽  
Design Curve ◽  
High Stress Concentration

High acoustic energy has the potential to cause severe Acoustic Induced Vibration (AIV) that leads to fatigue failure at high stress concentration regions such as fittings in a piping system. Sweepolet fittings have been extensively used as mitigation to counteract the risk of fatigue failure caused by AIV. The advantages of a sweepolet are its integrally reinforced contoured body and low stress concentration. However, there are inconsistencies in published standards and regarding the design limits for sweepolet subjected to AIV. In this paper, Finite Element Analysis is conducted to simulate high frequency pipe shell wall vibration caused by acoustic energy inside the pipe. Peak stress and the associated minimum fatigue life are calculated for sweepolet and sockolet under the same acoustic excitation. By comparing the stress level to that of a sockolet whose design limit to AIV had been published, the design curve and fatigue life equation for sweepolet are developed.

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