Dynamic Pipe Stresses During Water Hammer: A Finite Element Approach

2007 ◽  
Vol 129 (2) ◽  
pp. 226-233 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Finite Element ◽  
Pressure Wave ◽  
Maximum Stress ◽  
Pipe Wall ◽  
Applied Pressure ◽  
Three Dimensional ◽  
Water Hammer ◽  
Sudden Increase ◽  
Element Analysis ◽  
Dynamic Stresses

Water hammer is defined as a sudden increase in pipe pressure, which results in pressure waves that travel along the pipe at sonic velocities. In the wake of the pressure wave, dynamic stresses are created in the pipe wall, which contribute to pipe failures. A finite element analysis computer program was used to determine the three-dimensional dynamic stresses that result from pipe wall vibration at a distance from the end of a pipe, during a water-hammer event. The analysis was used to model a moving shock wave in a pipe, using a step pressure wave. Both aluminum and steel were modeled for an 8 NPS pipe, using ABAQUS®. For either material, the maximum stress was seen to be equal when damping was neglected. At the time the maximum stress occurred, the hoop stress was equivalent to twice the stress that would be expected if an equivalent static stress was applied to the inner wall of the pipe. Also, the radial stress doubled the magnitude of the applied pressure.

Dynamic Pipe Stresses During Water Hammer: I — A Finite Element Approach

2002 ◽  
Author(s):  
Robert A. Leishear ◽  
Edward F. Young ◽  
Curtis A. Rhodes ◽  
Elisabeth M. Alford
Keyword(s):  
Finite Element ◽  
Pressure Wave ◽  
Maximum Stress ◽  
Pipe Wall ◽  
Axial Stress ◽  
Applied Pressure ◽  
Water Hammer ◽  
Sudden Increase ◽  
Element Analysis ◽  
Dynamic Stresses

Water hammer is defined as a sudden increase in pipe pressure, which results in pressure waves that travel along the pipe at sonic velocities. In the wake of the pressure wave, dynamic stresses are created in the pipe wall, which contribute to pipe failures. A finite element analysis, computer program was used to determine the three dimensional dynamic stresses which result from pipe wall vibration at a distance from the end of a pipe, during a water hammer event. The analysis was used to model a moving shock wave in a pipe, using a step pressure wave. Both aluminum and steel were modeled for an 8 NPS pipe, using Abaqus®. For either material, the maximum stress was seen to be equal when damping was neglected. At the time the maximum stress occurred, the hoop stress was equivalent to twice the stress that would be expected if an equivalent static stress was applied to the inner wall of the pipe. At the same time, the radial stress was limited to the magnitude of the applied pressure, and the axial stress was equal to zero.

Dynamic Pipe Stresses During Water Hammer: III — Complex Stress Relationships

2002 ◽  
Author(s):  
Robert A. Leishear
Keyword(s):  
Pressure Wave ◽  
Dynamic Stress ◽  
Pipe Wall ◽  
Three Dimensional ◽  
Complex Stress ◽  
Water Hammer ◽  
Dynamic Stresses ◽  
Vibration Theory ◽  
Pressure Spike ◽  
Fluid Transients

Complex three-dimensional dynamic stresses occur in a pipe following a water hammer event. Equations from vibration theory were adapted for use to describe the dynamic stresses at any point along the pipe wall. Hoop, radial, and axial dynamic stress equations are presented to approximate the stresses at a point on the pipe wall. Dynamic stress equations for beams and other simple shapes are also considered. The dynamic pipe stresses are affected principally by the types of water hammer waves or fluid transients, by the wave impacts at elbows or tees, and by the reflections of the waves from these elbows or tees. The three fluid transients considered are a moving step pressure wave, a ramp pressure, and a moving pressure spike. Approximate techniques are presented for evaluating the effects on piping due to the impingement of these transients on an elbow. For an equivalent pressure in a long pipe, application of the step pressure created the largest stress increases of the three transients considered. The vibration equations also prompt a solution to reduce water hammer effects. To this end, slow closing valves are frequently employed. Vibration theory may be applied to quantify the stress reductions afforded by these valves. Pipe stress equations may be manipulated to reduce pipe stresses for a linearly increasing, or ramp, pressure wave traveling along the pipe.

scholarly journals Finite Element Analysis of Needle Insertion Angle in Insulin Therapy

2019 ◽  
Vol 16 (4) ◽  
pp. 7512-7523
Author(s):  
Syakirah Mohamed Amin ◽  
Muhammad Hanif Ramlee ◽  
Hadafi Fitri Mohd Latip ◽  
Gan Hong Seng ◽  
Mohammed Rafiq Abdul Kadir
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Insulin Therapy ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Needle Insertion ◽  
Stress And Strain ◽  
Medical Doctors ◽  
Element Analysis ◽  
Biomechanical Evaluation

Millions in the world suffering diabetes mellitus depends on insulin therapy to control their blood glucose level daily. However, the painful daily injections they need to take could lead to other complications if it is not done correctly. To date, it is suggested by many researchers and medical doctors that the needles should be inserted at any angles of 90º or 45º. Nevertheless, this recommendation has not been supported by clinical or biomechanical evaluation. Hence, this study evaluates the needle insertion for insulin therapy to find the favourable angles in order to reduce injury and pain onto the skin. Finite element analysis was done by  simulating the injection of three-dimensional (3D) needle model into a 3D skin model. The insertions were simulated at two different angles, which are 45ºand 90º with two different lengths of needles; 4 mm and 6 mm. This study concluded the favourable angle for 4 mm needle to be 90º while 6 mm needle was best to be inserted at 45º as these angles exerted the least maximum stress and strain onto the skin.

Finite Element Modeling of the Dynamic Response of a Steel Pipe During Water Hammer

2012 ◽  
Author(s):  
Juan C. Suárez ◽  
Paz Pinilla ◽  
Javier Alonso
Keyword(s):  
Finite Element ◽  
Wall Thickness ◽  
Pipe Wall ◽  
Element Model ◽  
Water Hammer ◽  
Steel Pipe ◽  
Dynamic Stresses ◽  
Rate Dependent ◽  
Simple Step ◽  
Von Mises

Water hammer imposes a steep rise in pipe pressure due to the rapid closure of a valve or a pump shutdown. Transversal strain waves propagate along the pipe wall at sonic velocities, and dynamic stresses are developed in the material, which can interact with discontinuities and contribute to an unexpected failure. Pressure increase has been modeled as a simple step front in a finite element model of a short section of a steel pipe. Boundary conditions have been considered to closely resemble the conditions of longer pipe behavior. The shock traveling along the length of the fluid-filled pipe causes a vibration response in the pipe wall. Dynamic strains and stresses follow the water hammer event with a certain delay, as is shown from the results of the FEA. Response of the material is strain rate dependent and dynamic peak stresses are substantially larger than the expected from the static pressure loads. Damping of the waves, neither by the material of the pipe nor by the interaction fluid-pipe, has not been considered in this simple model. Hoop, axial, radial, and Von Mises equivalent stresses have been evaluated both for the overshooting and the following phase of decompression of a pipe without discontinuities. However, dynamic stresses can be enhanced in the presence of discontinuities such as laminations, thickness losses in the pipe wall due to corrosion, changes in the wall thickness in neighboring pipe sections, dents, etc. These dynamic effects are able to explain how certain discontinuities that were reported as passing an Engineering Critical Assessment can eventually cause failure to the integrity of the structure. Deflections in the pipe wall can be altered by the welded transition from a pipe with a certain thickness to another with a smaller thickness, and wavelength changes of one order of magnitude can be expected. This can result in different approaches towards the risk assessment for discontinuities in the proximity of changes in wall thickness.

Three-Dimensional Finite Element Analysis of Implants with Different Crown-to-Root Ratio and Different High Thread

2014 ◽  
Vol 518 ◽  
pp. 190-195
Author(s):  
Ying Jie Duan ◽  
Ling Chen ◽  
Tao Xiong ◽  
Xing Hua Niu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Maximum Stress ◽  
Geometric Model ◽  
Three Dimensional ◽  
Element Analysis ◽  
Jaw Bone ◽  
Crown Root ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

To compare the strain and stress distribution on jaw bone around the implant with different crown-root and different teeth high in teeth repairing, three-dimensional geometric model of the implant was created and analyzed through UG and finite element analysis software. Model came to workbench software after it was drawn and assembly by 3D mapping software of UG. Given material properties of the model, meshing, boundary conditions and forces applied for analysis. It was Obtained that the size and distribution of stress and strain about jaw bone and implant under different conditions. The influence of jaw bone and implant in different conditions was discussed. The main results of the study are as follows: different implant and crown-root, maximum stress with the crown-root increases, but the maximum stress is placid. Factor in the high thread where the maximum stress with high thread show an inverted "U" shape, the maximum strain with high thread becomes flat.

Finite Element Analysis of 2450 Type Close-Top Mill Housing

2012 ◽  
Vol 601 ◽  
pp. 173-176
Author(s):  
Xi Wang ◽  
Chang Liang Xu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Maximum Stress ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Element Analysis ◽  
Stress Contour ◽  
Maximal Displacement

Aimed at the maximum stress and distortion, the three-dimensional model of 2450 type close-top mill housing was simulated by finite element analysis, with the help of FEM software (ANSYS). The positions of dangerous sections and the maximum stress was shown in stress contour. The displacement and maximal displacement of various points was obtained in the deformation contour. The results show that different structural parameters was used for the key parts, and the influence of parameters to stress and deformations can be obtained, which can provide reference for the design of the related mill housing.

Three-Dimensional Finite Element Analysis Used to Compare Six Different Methods of Syndesmosis Fixation with 3.5- or 4.5-mm Titanium Screws

2013 ◽  
Vol 103 (3) ◽  
pp. 174-180 ◽  
Author(s):  
Mehmet Serhan Er ◽  
Ozgur Verim ◽  
Levent Altinel ◽  
Suleyman Tasgetiren
Keyword(s):  
Finite Element ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Element Model ◽  
Element Analysis ◽  
Computed Tomographic ◽  
Cortical Screw ◽  
Titanium Screws ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Background: Use of thicker and longer (four cortices) screws or of multiple screws seems to be more stable and efficient for syndesmosis fixation. Methods: A three-dimensional finite element model of an ankle was constructed from serial axial sections from an existing two-dimensional computed tomographic image. Constructions of syndesmosis fixation with 3.5-mm single tricortical, 3.5-mm single quadricortical, 3.5-mm double tricortical, 3.5-mm double quadricortical, 4.5-mm single tricortical, and 4.5-mm single quadricortical screws were performed on this model. Physiologic loads approximating those during stance phase normal walking were applied to this ankle system. Stress values on the screws using the six fixation methods were compared. Results: The highest maximum stress was determined over 3.5-mm cortical screws applied as single quadricortical, and the lowest maximum stress was determined over the 4.5-mm cortical screw applied as single quadricortical. Stress on the 3.5-mm single screw with quadricortical application was found to be higher than that with tricortical application and also compared with the 4.5-mm quadricortical screw application. Differences between the 4.5-mm single tricortical and quadricortical screws and between the 3.5-mm single tricortical and 3.5-mm double tricortical screw applications were not significant. Conclusions: Quadricortical application of 3.5-mm single screws and tricortical application of 3.5-mm double cortical screws are not good choices for syndesmosis fixation. If the plan is tricortical application, a 3.5-mm single cortical screw is adequate. If quadricortical application of syndesmosis fixation is planned, a 4.5-mm cortical screw should be used. (J Am Podiatr Med Assoc 103(3): 174–180, 2013)

scholarly journals Three-Dimensional Finite Element Analysis of Anterior Two-Unit Cantilever Resin-Bonded Fixed Dental Prostheses

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Filip Keulemans ◽  
Akikazu Shinya ◽  
Lippo V. J. Lassila ◽  
Pekka K. Vallittu ◽  
Cornelis J. Kleverlaan ◽  
...  
Keyword(s):  
Finite Element ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Element Analysis ◽  
Framework Materials ◽  
Dental Prostheses ◽  
Reinforced Composite ◽  
Dimensional Finite Element ◽  
Fixed Dental Prostheses ◽  
Three Dimensional Finite Element

The aim of this study was to evaluate the influence of different framework materials on biomechanical behaviour of anterior two-unit cantilever resin-bonded fixed dental prostheses (RBFDPs). A three-dimensional finite element model of a two-unit cantilever RBFDP replacing a maxillary lateral incisor was created. Five framework materials were evaluated: direct fibre-reinforced composite (FRC-Z250), indirect fibre-reinforced composite (FRC-ES), gold alloy (M), glass ceramic (GC), and zirconia (ZI). Finite element analysis was performed and stress distribution was evaluated. A similar stress pattern, with stress concentrations in the connector area, was observed in RBFDPs for all materials. Maximal principal stress showed a decreasing order: ZI > M > GC > FRC-ES > FRC-Z250. The maximum displacement of RBFDPs was higher for FRC-Z250 and FRC-ES than for M, GC, and ZI. FE analysis depicted differences in location of the maximum stress at the luting cement interface between materials. For FRC-Z250 and FRC-ES, the maximum stress was located in the upper part of the proximal area of the retainer, whereas, for M, GC, and ZI, the maximum stress was located at the cervical outline of the retainer. The present study revealed differences in biomechanical behaviour between all RBFDPs. The general observation was that a RBFDP made of FRC provided a more favourable stress distribution.

Contact Simulation and Analysis on Planetary Gear of Megawatt Wind Turbines Yawing Reducer

2012 ◽  
Vol 455-456 ◽  
pp. 187-193 ◽  
Author(s):  
Jia Qiang E ◽  
Jiang Dong Dong ◽  
Guan Lin Liu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbines ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Planetary Gear ◽  
Tooth Surface ◽  
Operation Condition ◽  
Element Analysis ◽  
Operation Process

.According to the operation condition of megawatt wind turbines yawing reducer, an assembly model of megawatt wind turbines yawing reducer is established, and aiming at different load conditions, the tooth surface of three teeth planetary gear model is analysised with using finite element analysis software-ANSYS ,including three-dimensional nonlinear contact analysis and structural finite element analysis which simulates contact stress of engagement pairs during the operation process of planetary gear. The results indicated that when the torque is M1=100N·m, the maximum stress on the engagement pairs is 177.584MPa; when the torque is and M2=300N·m, the maximum stress on the engagement pairs is 329.607MPa, which were less than the yield limit of planetary gear materials, but it can meet the design and operation requirements of planetary gear of megawatt wind turbines yawing reducer.

scholarly journals Biomechanical Property of a Newly Designed Assembly Locking Compression Plate: Three-Dimensional Finite Element Analysis

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Jiang-Jun Zhou ◽  
Min Zhao ◽  
Da Liu ◽  
Hai-Ying Liu ◽  
Cheng-Fei Du
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Maximum Stress ◽  
Three Dimensional ◽  
Locking Compression Plate ◽  
Bone Block ◽  
Element Analysis ◽  
Compression Plate ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this study, we developed and validated a refined three-dimensional finite element model of middle femoral comminuted fracture to compare the biomechanical stability after two kinds of plate fixation: a newly designed assembly locking compression plate (NALCP) and a locking compression plate (LCP). CT data of a male volunteer was converted to middle femoral comminuted fracture finite element analysis model. The fracture was fixated by NALCP and LCP. Stress distributions were observed. Under slow walking load and torsion load, the stress distribution tendency of the two plates was roughly uniform. The anterolateral femur was the tension stress area, and the bone block shifted toward the anterolateral femur. Maximum stress was found on the lateral border of the number 5 countersink of the plate. Under a slow walking load, the NALCP maximum stress was 2.160e+03 MPa and the LCP was 8.561e+02 MPa. Under torsion load, the NALCP maximum stress was 2.260e+03 MPa and the LCP was 6.813e+02 MPa. Based on those results of finite element analysis, the NALCP can provide adequate mechanical stability for comminuted fractures, which would help fixate the bone block and promote bone healing.

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