The Effect of Pedicle Screw Thread Shape on the Stress Concentration Under Lateral Bending

2019 ◽  
Author(s):  
Yucheng Yang ◽  
Qin Ma
Keyword(s):  
Stress Concentration ◽  
Maximum Stress ◽  
High Stress ◽  
Three Dimensional ◽  
Spinal Column ◽  
Pedicle Screws ◽  
Screw Thread ◽  
Lateral Bending ◽  
High Stress Concentration ◽  
Stress Patterns

Abstract Pedicle screws (PS) are frequently used in medical spinal column fixation. Despite 7 out of 100 pedicle screws fracture inside of the patients’ body and under the claim that lateral bending is the main failure mode, little research has addressed the stress characteristics and the fracture location of the PS under lateral bending. This study focuses on the effect of thread design on the magnitude and location of maximum stress concentration. Four types of thread shapes are considered including V-shape, square-shape, buttress, and reverse buttress. Three-dimensional (3D) finite element (FE) methods are used in this investigation. A load of 150 Newton is applied at the screw head to simulate lateral bending. The models are created in SolidWorks. The 3D FE analysis is performed using the standard coding of ANSYS Workbench 19.1. Based on this study, it is found that the high stress concentration is located at the cortical bone region rather than at the cancellous bone region. Although the general stress patterns are similar, the PS thread shape design and the thread fillet radius may significantly affect on the magnitude and location of maximum stress concentration.

scholarly journals The Effect of Implant Length and Diameter on Stress Distribution around Single Implant Placement in 3D Posterior Mandibular FE Model Directly Constructed Form In Vivo CT

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7344
Author(s):  
Akikazu Shinya ◽  
Yoshiki Ishida ◽  
Daisuke Miura ◽  
Akiyoshi Shinya
Keyword(s):  
High Stress ◽  
Three Dimensional ◽  
Clinical Situation ◽  
Mechanical Analysis ◽  
Fe Model ◽  
High Stress Concentration ◽  
Implant Placement ◽  
Implant Therapy ◽  
Mandibular First Molar

A three-dimensional (3D) finite element (FE) model of the mandibular bone was created from 3D X-ray CT scan images of a live human subject. Simulating the clinical situation of implant therapy at the mandibular first molar, virtual extraction of the tooth was performed at the 3D FE mandibular model, and 12 different implant diameters and lengths were virtually inserted in order to carry out a mechanical analysis. (1) High stress concentration was found at the surfaces of the buccal and lingual peri-implant bone adjacent to the sides of the neck in all the implants. (2) The greatest stress value was approximately 6.0 MPa with implant diameter of 3.8 mm, approx. 4.5 MPa with implant diameter of 4.3 mm, and approx. 3.2 MPa with implant diameter of 6.0 mm. (3) The stress on the peri-implant bone was found to decrease with increasing length and mainly in diameter of the implant.

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.

An Experimental and Numerical Analysis of Riveted Single Lap Joints

1994 ◽  
Vol 208 (2) ◽  
pp. 79-90 ◽  
Author(s):  
C-P Fung ◽  
J Smart
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Three Dimensional ◽  
Element Model ◽  
Lap Joints ◽  
Published Data ◽  
Single Lap Joints ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Stress Patterns

Countersunk and snap riveted single lap joints have been examined both experimentally and numerically. A total of 11 specimens were fatigued to failure with failures occurring in either the plate or the rive***r. The failures have been metallurgically examined to determine the cause of failure. The joints have also been analysed using the finite element method. Initially a single lap joint has been modelled as a ‘stepped plate’ and the results for the stress concentration factor found to be in reasonable agreement with published data. However, the stress concentration for this joint occurred at a point away from the point of failure of a riveted joint. A fuller three-dimensional finite element model has been constructed and the stress patterns around the rivet determined. These stress patterns are discussed in relation to the results from the metallurgical examination.

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.

Three-Dimensional Stress State Around Corrosive Cavities on Pressure Vessels

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Z. Abdulaliyev ◽  
S. Ataoglu ◽  
O. Bulut ◽  
E. S. Kayali
Keyword(s):  
Maximum Stress ◽  
High Stress ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Empirical Expression ◽  
Ellipsoidal Cavity ◽  
Industrial Sectors ◽  
Internal Surfaces ◽  
Different Types ◽  
Distribution Of Stress

Internal surfaces of pressure vessels used in many industrial sectors are subjected to corrosive effects leading to cavities. In this study, corrosive cavities on investigated pressure vessels are classified according to their shapes and dimensions. Distribution of stress was experimentally investigated around regions of different types of cavities using three-dimensional photoelastic models. An empirical expression is proposed to determine where maximum stress occurs in type of ellipsoidal cavity in the case of uniaxial loading. The obtained results show quite high stress levels around the cavity regions in pressure vessels, which increase the risk of crack formation.

Numerical Analysis of a Flexible Pipe With Damaged Tensile Armor Wires

2009 ◽  
Author(s):  
Jose´ Renato M. de Sousa ◽  
Aline Nacif Pinho ◽  
Gilberto Bruno Ellwanger ◽  
Edison C. P. Lima
Keyword(s):  
Mechanical Response ◽  
High Stress ◽  
Three Dimensional ◽  
Element Model ◽  
Axial Rotation ◽  
Flexible Pipe ◽  
High Stress Concentration ◽  
Flexible Pipes ◽  
Localized Defects ◽  
Nonlinear Finite Element Model

This paper focus on the structural analysis of a 2.5″ flexible pipe with one up to five broken wires in its outer tensile armor. The pipe is supposed to be under pure tension and the effect of the number of ruptured wires on its response is discussed. A three-dimensional nonlinear finite element model devoted to analyze the local mechanical response of flexible pipes is proposed and employed in all performed analyses. This model is capable of representing each wire of the tensile armors and, therefore, localized defects, including total rupture, may be adequately represented. The obtained results pointed to high stress concentration in the wires near the damaged ones as well as a significant increase in the axial rotation of the pipe. Moreover, the stresses in the inner carcass and the pressure armor are also affected by the rupture of wires in the outer tensile armor.

Three-Dimensional Elastic Stress Fields of Finite Thickness Plates with Elliptical Hole

2007 ◽  
Vol 353-358 ◽  
pp. 74-77
Author(s):  
Zheng Yang ◽  
Chong Du Cho ◽  
Ting Ya Su ◽  
Chang Boo Kim ◽  
Hyeon Gyu Beom
Keyword(s):  
Stress Concentration ◽  
Plane Strain ◽  
Plane Stress ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Maximum Stress ◽  
Elastic Stress ◽  
Finite Thickness ◽  
Plate Thickness ◽  
Three Dimensional

Based on detailed three-dimensional finite element analyses, elastic stress and strain field of ellipse major axis end in plates with different thickness and ellipse configurations subjected to uniaxial tension have been investigated. The plate thickness and ellipse configuration have obvious effects on the stress concentration factor, which is higher in finite thickness plates than in plane stress and plane strain cases. The out-of-plane stress constraint factor tends the maximum on the mid-plane and approaches to zero on the free plane. Stress concentration factors distribute ununiformly through the plate thickness, the value and location of maximum stress concentration factor depend on the plate thickness and the ellipse configurations. Both stress concentration factor in the middle plane and the maximum stress concentration factor are greater than that under plane stress or plane strain states, so it is unsafe to suppose a tensioned plate with finite thickness as one undergone plane stress or plane strain. For the sharper notch, the influence of three-dimensional stress state on the SCF must be considered.

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.

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