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.

Acoustic Vibration Induced Fatigue in Pipe Joints

2015 ◽  
Author(s):  
Ajay Prakash ◽  
Philip Diwakar ◽  
Dan Lin ◽  
Paul Deane ◽  
Yuqing Liu ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sound Pressure ◽  
High Stress ◽  
Acoustic Vibration ◽  
Acoustic Energy ◽  
Piping System ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Pipe Joints

High acoustic energy has the potential to cause severe acoustic induced vibration (AIV) that can lead to fatigue failure at high stress concentration locations (discontinuities) in a piping system. AIV at pipe junctions (Lateral, Tee, and Wye) and welded support attachments (trunnions and shoes) is evaluated using Finite Element Analysis. At different size pipe junctions, branch and header pipe shells may be subjected to different sound pressure. Also, inertia associated with different wall thickness(s) can lead to very different dynamic response of the two shell walls. The effect of these differences on AIV response is analyzed. Resulting response for different junction reinforcement designs is evaluated and compared to an unreinforced ‘stub-on’ configuration to assess the designs.

Acoustic Vibration Induced Fatigue in Welded Pipe Supports

2017 ◽  
Author(s):  
Yuqing Liu ◽  
Philip Diwakar ◽  
Dan Lin ◽  
Matt Jaouhari ◽  
Ajay Prakash
Keyword(s):  
Fatigue Life ◽  
Peak Stress ◽  
Acoustic Vibration ◽  
Acoustic Energy ◽  
Piping System ◽  
Acoustic Excitation ◽  
Element Analysis ◽  
Potential Failure ◽  
Welded Pipe ◽  
Failure Location

High acoustic energy has the potential to cause vibration induced fatigue in a piping system at integral attachments such as welded pipe supports. Although recognized as a potential failure location, there is no established design curve and fatigue life equation among industry guidelines. In this paper, acoustic induced vibration (AIV) at welded supports is evaluated using Finite Element Analysis. Peak stress and the associated minimum fatigue life is calculated for various types of welded supports under the same acoustic excitation. By comparing the stress level to that of a branch connection, for which design limit for AIV have been published, the design limit and fatigue life equation for welded pipe supports is developed. The use of partial reinforcement pad to mitigate AIV risk is also discussed.

Fatigue Failure Analysis Using the Theory of Critical Distance

2011 ◽  
Vol 462-463 ◽  
pp. 663-667 ◽  
Author(s):  
Ruslizam Daud ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Al Emran Ismail
Keyword(s):  
Stress Concentration ◽  
Fatigue Failure ◽  
Notch Root ◽  
High Stress ◽  
Critical Distance ◽  
Future Research ◽  
Element Analysis ◽  
Linear Elastic ◽  
The Finite Element Analysis ◽  
Elastic Fracture

This paper explores the initial potential of theory of critical distance (TCD) which offers essential fatigue failure prediction in engineering components. The intention is to find the most appropriate TCD approach for a case of multiple stress concentration features in future research. The TCD is based on critical distance from notch root and represents the extension of linear elastic fracture mechanics (LEFM) principles. The approach is allowing possibilities for fatigue limit prediction based on localized stress concentration, which are characterized by high stress gradients. Using the finite element analysis (FEA) results and some data from literature, TCD applications is illustrated by a case study on engineering components in different geometrical notch radius. Further applications of TCD to various kinds of engineering problems are discussed.

Fatigue Life Prediction of Notched Specimen Based on Stress Gradient

2020 ◽  
Author(s):  
Masahiro Takanashi
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Life Prediction ◽  
Notch Root ◽  
Stress Gradient ◽  
Peak Stress ◽  
Fatigue Life Prediction ◽  
Element Analysis ◽  
Notched Specimen ◽  
Gradient Approach

Abstract Many failure accidents have indicated fatigue as the primary cause for the failure of a machine or structure. In general, the origin of failure is a structural discontinuous part such as a welded joint or a notched member that causes stress concentration. While designing such a component, a finite element analysis (FEA) has to be conducted, and the peak stress has to be compared with a design fatigue curve obtained from small-sized specimens to evaluate whether the component satisfies the design life. However, it is known that a fatigue life prediction at a stress concentration part based on a peak stress always provides an excessively conservative estimation. This is due to the stress gradient of the component. This paper discusses the stress-gradient approach to eliminate the conservatism and rationalize a fatigue design. Using literature test data, the relationship between the stress gradient calculated using FEA, and the fatigue strength reduction ratio was determined. Later, a fatigue test was conducted on a notched specimen of low-alloy steel to verify the stress-gradient approach, and the fatigue life of the notched specimen was predicted considering the stress gradient at the notch root. The predicted fatigue life agreed well with the experimental results.

Analysis and validation of femur bone data using finite element method under static load condition

2019 ◽  
Vol 233 (16) ◽  
pp. 5547-5555 ◽  
Author(s):  
S Mathukumar ◽  
VA Nagarajan ◽  
A Radhakrishnan
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Static Load ◽  
High Stress ◽  
Load Condition ◽  
Computational Method ◽  
Medical Attention ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Femur Bone

Humans face bone fracture when they unfortunately met an accident, which requires timely medical attention for healing and repairing the fractured bone; otherwise that paralyzes their life. 3D modeling technique with computational method is very helpful at the side of doctors for healing and repairing the damaged bones. Fractional bone healing is one of the natural processes, which regain the mechanical reliability of the bone to a limited level of failures. The relationship between the biology and mechanics has introduced a new branch namely biomechanics. Various biomechanics models were used to identify the fracture for different patients and helps in the fracture treatment. The aim of this work is to find out the high stress concentration area of the femur bone, which has been extracted as image from computer tomography scanner. The retrieved noise-free femur bone image is tested by the static load condition with the help of the finite element analysis. The result obtained from the testing of different loads has been compared with the existing literature. It is found that the femur bone has tensile and compressive stress, and the neck area of the femur is at a very high stress concentration. The outcome of this work is much supportive to orthopedic surgeons in femur surgery and bone prosthesis by avoiding experiments on femur bone.

Residual Stress Estimation in Crossbores With Bauschinger Effect Inclusion Using FEM and Strain Energy Density

1999 ◽  
Vol 121 (4) ◽  
pp. 358-363 ◽  
Author(s):  
E. A. Badr ◽  
J. R. Sorem ◽  
S. M. Tipton
Keyword(s):  
Finite Element Analysis ◽  
Stress Concentration ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Analytical Approach ◽  
Bauschinger Effect ◽  
High Stress ◽  
Element Analysis ◽  
Elastic Plastic ◽  
High Stress Concentration

Crossbore intersections in liquid ends of positive displacement pumps (PDPs) have regions with high stress concentration. Due to the cyclic loading that occurs in most PDPs, these stress concentration points are susceptible to fatigue cracking. In order to prolong their life, the liquid ends are often overpressurized (autofrettaged), thus inducing beneficial compressive hoop stresses in these critical regions upon removal of the autofrettage pressure. This autofrettage process drives the region of high stress concentration beyond the elastic limit and well into the elastic-plastic region. Elastic-plastic stresses and strains due to loading and unloading were analyzed in crossbore geometries, with Bauschinger effect included, using 3-D finite element analysis of the liquid end. For comparison, an analytical approach was developed, based on the strain energy density criterion first proposed by Glinka. The approach was modified to include the Bauschinger effect for precise estimation of such stresses and strains. Good correlation was observed between elastic-plastic crossbore stresses and strains predicted by the analytical approach and the finite element analysis.

Localized Autofrettage as a Design Tool for the Fatigue Improvement of Cross-Bored Cylinders

1998 ◽  
Vol 120 (4) ◽  
pp. 393-397 ◽  
Author(s):  
A. E. Segall ◽  
C. Tricou ◽  
M. Evanko ◽  
J. C. Conway
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
High Stress ◽  
Circular Crack ◽  
Design Tool ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Significant Extension ◽  
The Cross ◽  
Machining Operations

An investigation was launched into the feasibility of improving the fatigue life of thick-walled cylinders with cross-bores by using a localized autofrettage technique. This technique utilized the high stress concentration at the cross-bore to induce localized residual stresses using relatively low internal pressures. An elastic-plastic finite-element analysis indicated that the resulting residual stresses in the vicinity of the cross-bore were predominately compressive and not sufficient in magnitude to induce reverse plasticity. When the resulting residual stresses were used with an elastic fracture-mechanics assessment of a quarter-circular crack at the intersection of the cylinder and cross-bore inner diameter, a significant extension of fatigue life was shown to be possible. In addition to prolonging the useful life of the cylinder, the localized residual stresses were shown to be possible at pressures below the yield threshold for the thick-walled cylinder. Thus, reverse plasticity, permanent deformations, and the need for post-autofrettage machining operations that could inadvertently lessen the beneficial results of a traditional autofrettage were avoided.

Acoustic Fatigue Evaluation of Branch Connections

2014 ◽  
Author(s):  
Dan Lin ◽  
Ajay Prakash ◽  
Philip Diwakar ◽  
Bertito David
Keyword(s):  
Maximum Stress ◽  
High Stress ◽  
Acoustic Energy ◽  
Mitigation Measures ◽  
Element Analysis ◽  
Acoustic Frequency ◽  
High Stress Concentration ◽  
Fatigue Evaluation ◽  
Acoustic Fatigue ◽  
Vibration Damage

High acoustic energy is known to cause vibrations in pipes, and in some severe cases acoustic induced vibration can lead to fatigue failure at branch connections with high stress concentration. Industry guidelines suggest using mitigation measures such as fabricated full wrap-around reinforcement pad (re-pad) or Sweepolet fittings at branch connections. Effectiveness of these mitigation measures is evaluated via a finite element analysis of four types of branch connections; (i) Sockolet, (ii) Sockolet with 2″ wide partial re-pad, (iii) Sockolet with full wrap-around re-pad, and (iv) Sweepolet. Four distinct acoustic frequency ranges (1/3 octave bands) with associated sound pressure levels are used as the excitation source. Maximum stress levels in the main header pipe at the branch tie-in are monitored to assess the potential for vibration damage. Of the four branch connections, Sockolet with full wrap-around re-pad is found to be least susceptible to damage, followed by the Sweepolet. Unreinforced Sockolet is most susceptible to damage, and the Sockolet with partial re-pad is only marginally better.

Comparison on Stress Concentration Factors of Y/T Tubular Joints Between Numerical and Parametric Formulation Results

2005 ◽  
Author(s):  
Stefano Baratella ◽  
Dario Boote ◽  
Fabio Petrillo ◽  
Fabrizio Stefani
Keyword(s):  
Stress Concentration ◽  
Numerical Models ◽  
High Stress ◽  
Bending Moment ◽  
Steel Structures ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Wide Range ◽  
Long Time ◽  
Stress Concentration Factors

The action of environmental loads such as wind and waves on offshore steel structures is locally emphasized by complex tubular connections, giving place to high stress concentration in correspondence of welds between pipe elements. This phenomenon, which heavily influences the fatigue life of the joint and, as a consequence, the operability of the whole platform, can be quantified by the Stress Concentration Factor. SCF can be determined either by experimental approach, numerical analysis and parametrical formulas developed mainly in the seventies-eighties by specialized authors like Kuang, Wordsworth, Smedley and Efthymiou. Even though these formulas, quoted as reference in the main world recognized rules, represented for a long time a useful tool for the designers of most projects, some discrepancies have been found to exist among them. A research has then been jointly promoted by University of Genoa and RINA Industry in order to compare the results of the parametric formulas with those coming from a finite element analysis performed on very refined numerical models made of brick elements. In this investigation attention has been focused on Y/T type joints; a wide range of configurations has been analysed by varying the most important parameters defining the geometry of the joint. Each configuration has been loaded by axial force and in/out of plane bending moment.

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