Calculating Failure Pressure Under Different Failure Modes in the Roof-to-Shell of a Vaulted Tank

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yuqi Ding ◽  
Jubao Liu ◽  
Zengtao Chen ◽  
Feng Qiu ◽  
Qifa Lu
Keyword(s):  
Finite Element ◽  
Theoretical Calculation ◽  
Relative Error ◽  
Failure Criterion ◽  
Failure Modes ◽  
Maximum Relative Error ◽  
Failure Pressure ◽  
Compression Ring ◽  
Strength Failure ◽  
Ring Section

In this study, two failure modes, yield buckling of the compression ring section and strength failure in the roof-to-shell of the tank, have been proposed for a vertical vaulted tank. The failure criteria of the two failure modes in the roof-to-shell of vault tanks are established via finite element analysis of three tanks of 640 m3, 3200 m3, and 6800 m3 in volume. The finite element models are built with axisymmetric elements and spatial multi-elements. Based on the strength failure criterion, the failure pressure formula in the vaulted tank roof-to-shell is derived. The maximum relative error between the theoretical calculation and numerical simulation is 9.7%. Finally, we verify the strength failure criterion through a tank failure test; the maximum relative error between the test and theoretical calculation is 9.6%. The failure pressure of both failure modes has been compared and analyzed. The failure pressure of the yield buckling in the compression ring section is about 1.65 times that of the strength failure in the roof-to-shell of the tank.

Structural Integrity Assessment of Steam Generator Tube by the Use of Heterogeneous Finite Element Method

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Xinjian Duan ◽  
Michael J. Kozluk ◽  
Sandra Pagan ◽  
Brian Mills
Keyword(s):  
Finite Element ◽  
Steam Generator ◽  
Failure Modes ◽  
Structural Integrity ◽  
Fretting Wear ◽  
Defect Depth ◽  
Steam Generator Tube ◽  
Integrity Assessment ◽  
Failure Pressure ◽  
Steam Generator Tubes

Aging steam generator tubes have been experiencing a variety of degradations such as pitting, fretting wear, erosion-corrosion, thinning, cracking, and denting. To assist with steam generator life cycle management, some defect-specific flaw models have been developed from burst pressure testing results. In this work, an alternative approach; heterogeneous finite element model (HFEM), is explored. The HFEM is first validated by comparing the predicted failure modes and failure pressure with experimental measurements of several tubes. Several issues related to the finite element analyses such as temporal convergence, mesh size effect, and the determination of critical failure parameters are detailed. The HFEM is then applied to predict the failure pressure for use in a fitness-for-service condition monitoring assessment of one removed steam generator tube. HFEM not only calculates the correct failure pressure for a variety of defects, but also predicts the correct change of failure mode. The Taguchi experimental design method is also applied to prioritize the flaw dimensions that affect the integrity of degraded steam generator tubes such as the defect length, depth, and width. It has been shown that the defect depth is the dominant parameter controlling the failure pressure. The failure pressure varies almost linearly with defect depth when the defect length is greater than two times the tube diameter. An axial slot specific flaw model is finally developed.

scholarly journals Failure analysis of a frangible composite cover: A transient-dynamics study

2016 ◽  
Vol 51 (18) ◽  
pp. 2607-2617
Author(s):  
Deng’an Cai ◽  
Guangming Zhou ◽  
Yuan Qian ◽  
Vadim V Silberschmidt
Keyword(s):  
Finite Element ◽  
Failure Analysis ◽  
Failure Criterion ◽  
Element Model ◽  
Transient Dynamics ◽  
Dynamics Model ◽  
Test Device ◽  
Weak Zone ◽  
Failure Pressure ◽  
Model Failure

A transient-dynamics model based on the approximate Riemann algorithm is proposed for the failure analysis of a frangible composite canister cover. The frangible cover, manufactured with a traditional manual lay-up method, is designed to conduct a simulated missile launch test using a specially developed test device. Deformation of the cover’s centre is determined using a transient-dynamics finite element model; failure pressure for the frangible cover is obtained based on a failure criterion and compared with simulated experimental results. Weak-zone position of the frangible cover has a significant effect on failure pressure compared to that of deformation of the cover’s centre. With the same structure of the weak-zone, an increase in its height can first raise and then reduce the level of failure pressure of the frangible cover. Close agreements between the experimental and numerical results are observed.

New Procedures for the Residual Strength Assessment of Corroded Pipe Subjected to Combined Loads

1996 ◽  
Author(s):  
Marina Q. Smith ◽  
Stephen C. Grigory
Keyword(s):  
Finite Element ◽  
Failure Criterion ◽  
Failure Modes ◽  
Model Development ◽  
Metal Loss ◽  
General Corrosion ◽  
Moment Capacity ◽  
Strength Assessment ◽  
Global Buckling ◽  
Buckling Failure

Motivated by the inability to accurately address non-pressure related stresses within the framework of current assessment guidelines, a three phase study aimed at the progressive development of a reliable and readily-useable procedure suitable for the analysis of internally pressurized degraded pipes which sustain large settlement and/or axial loads was performed. To ensure accuracy of the resulting procedure, full-scale experiments and finite element numerical simulations of artificially corroded 48-inch (122-cm) diameter X65 pipes subjected to combined loadings were designed to produce upper and lower bound rupture and global buckling failure envelopes for a given set of representative corrosion dimensions. The evaluation model accommodates combined stresses arising from internal pressure, axial bending, and axially compressive loadings to predict operational margins of safety for a pipe containing discrete or multiple metal loss regions guided by failure criteria which considers two critical failure modes: 1) a von Mises type failure criterion for rupture moment capacity determination, and 2) a global buckling failure criterion for identification of the critical moment capacity approximating collapse of the pipe mid-section due to a reduction in bending stiffness attributed in part to ovalization of the cross-section. The new methodology has been incorporated in the personal computer based program SAFE (Shell Analysis Failure Envelope), developed by Southwest Research Institute (SwRI) for the Alyeska Pipeline Service Company. The user-friendly program allows for definition of combined applied stresses and geometry of the degraded region through implementation of field-obtainable pre-or post-excavation measurements, and employs unique features which provide for the examination of pipe sections exhibiting distinct areas of general corrosion, or “patches,” separated both longitudinally and circumferentially, in a single analysis run. This paper outlines the model development and validation with supporting experiments and numerical analyses, and extension of the new procedure through sophisticated numerical techniques embodied in SAFE to actual corrosion profiles and service loadings. Detailed information included in the review are the finite element and SAFE program failure predictions for pipes analyzed with a given set of corrosion dimensions and load magnitudes, and a thorough discussion of the practical application of the SAFE program.

A New Method for Analyzing X-Cor Sandwich’s Shear Strength

2012 ◽  
Vol 510 ◽  
pp. 356-361
Author(s):  
Xu Dan Dang ◽  
Shao Jie Shi ◽  
Yi Guo ◽  
Jun Xiao
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Failure Criterion ◽  
Failure Modes ◽  
Failure Process ◽  
Stiffness Degradation ◽  
Strength Analysis ◽  
Finite Element Software ◽  
Pull Out ◽  
Comparison Results

The finite element software was used to get the X-cor sandwich’s shear strength. During the shear strength analysis, the failure criterion and materials stiffness degradation rules fitting for the analysis of X-cor sandwich’s failure mechanism were proposed and the X-cor sandwich’s failure process and modes were also clarified. According to the failure criterion we used the elements with stiffness degradation and their distributions in the finite element model to simulate the types and propagation path of the failure and the failure mechanisms of X-cor sandwich under shear were explained. The finite element analysis indicates during the shear firstly the resin regions fail and then the multiple failure modes of Z-pin pull-out from the face-sheet, Z-pin shear off and Z-pin buckling all exist. The propagation paths of the failure elements are dispersive. By contrasting the finite element results and test results the values are consistent well and the error range is -10.4%~7.4%. The comparison results show that the failure criterion and stiffness degradation rules are reasonable and this method can be used to predict the X-cor sandwich’s shear strength.

scholarly journals An Extended Spring-mass Model of Single-lap Multi-bolt Composite Joints Considering Assembly Gap and Gap Shimming

2021 ◽  
Author(s):  
yuxing yang ◽  
Yongjie Bao ◽  
Jinlong Wang ◽  
Fengming Du
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Relative Error ◽  
Joint Stiffness ◽  
Shear Stiffness ◽  
Shear Loading ◽  
Maximum Relative Error ◽  
Composite Joints ◽  
Composite Joint ◽  
Proposed Model

Abstract To investigate the effect of assembly gap and shim on single-lap multi-bolt composite joint stiffness, an analytical model based on the spring-mass method was proposed, which converted the multi-bolt joints into individual single-bolt joint based on premise that there are no overlap regions of the highly stressed portions for adjacent holes. The proposed model considers the conical and spherical stress envelope and gradual elimination phenomenon of the bolt-hole clearances for multi-bolt joints. Meantime, an effective-to-equivalent gap area method was proposed to calculate the joint stiffness for situations with arbitrary assembly gap shape. Both experiment and finite element method for three-bolt joints were used to validate the proposed model with different situations of assembly gap and/or shim. The relative error of the shear stiffness between the analytical model and experiment is 0.31%, while that of the bolt stiffness is 19.8%. After that, four interested situations with different assembly gap and/or shims were discussed, and the maximum relative error of the shear stiffness between the analytical model and the finite element model is17.0%, while that of the bolt stiffness is 15.8%. Taking into account the complexity of composite material and that of assembly gap and gap shimming, the proposed analytical model is effective to predict the stiffness of the single-lap multi-bolt composite joints subjected to single-shear loading.

A Calculation Method of Ultimate Torsional Strength for Subsea Collet Connector Based on Finite Element Method

2016 ◽  
Author(s):  
Kang Zhang ◽  
Menglan Duan ◽  
Xiaolan Luo ◽  
Yi Hong
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Failure Criterion ◽  
Calculation Method ◽  
Ultimate Bearing Capacity ◽  
Design Parameters ◽  
Damage Resistance ◽  
Torsional Strength ◽  
Strength Failure ◽  
Sealing Failure

Subsea connector is an important connection facility in subsea production system. Once destroyed, it will cause sealing failure which could lead to leakage accident, so the connectors must have high degree of damage-resistance capacity. Ultimate bearing capacity is composed of a set of important parameters measuring subsea connectors’ damage-resistance capacity, such as ultimate bending strength, ultimate torsional strength, etc. However, these data are usually obtained by carrying out destructive tests, which will bring heavy cost to subsea connector products in order to obtain the required technical data. Considering reducing the cost of destructive testing, a theoretical calculation method is needed to be developed. In addition, during the stage of product design, it is also necessary to estimate ultimate bearing capacity to verify whether the structural design parameters meet the anticipated requirements. In this paper, only the ultimate torsional strength of subsea connectors was studied, and based on finite element analysis, a calculation method of ultimate torque was put forward, which consists of using finite element software to build the 3D subsea connector model, loading different pure torsional moment, analyzing the calculation results and establishing torsional failure criteria to determine ultimate torsional strength. The results show that sealing failure will be ahead of structural strength failure under the pure torsional loads, and traditional strength failure criterion is not suitable for determining ultimate torsional strength of subsea connectors; the numerical solution of ultimate torque is 60KN·m based on the sealing failure criterion in this paper. In the end, a simplified mechanical model of subsea connector was established, the limit state equation of sealing failure was built in the action of pure torsional load, and the analytical solution of ultimate torque was calculated. The calculation method of ultimate torsional strength established in this paper was verified through comparative analysis.

Study on the Tensile Strength in X-Cor Sandwich by Using Finite Element Method

2012 ◽  
Vol 601 ◽  
pp. 265-269
Author(s):  
Xu Dan Dang ◽  
Shao Jie Shi ◽  
Jun Xiao
Keyword(s):  
Finite Element ◽  
Tensile Strength ◽  
Failure Criterion ◽  
Failure Modes ◽  
Stiffness Degradation ◽  
Propagation Path ◽  
Strength Analysis ◽  
Element Analysis ◽  
Pull Out ◽  
Comparison Results

In the tensile strength analysis, the failure criterion and materials stiffness degradation rule were proposed and the X-cor sandwich’s failure modes were also clarified. According to the failure criterion we used the elements with stiffness degradation and their distributions in the finite element model to simulate the types and propagation path of the failure and the failure mechanisms of X-cor sandwich were explained. The finite element analysis indicates during the tension firstly the interfaces between resin regions and Z-pin tips fail and the failure mode is Z-pin pull-out from the face-sheets. The finite element simulated results are in good agreement with the experimental results, the error range is -11.6%~9.7%. The comparison results show the failure criterion and stiffness degradation rule are reasonable and this method can be used to predict the X-cor sandwich’s tensile strength.

Load Testing to Collapse Limit State of Barr Creek Bridge

2000 ◽  
Vol 1696 (1) ◽  
pp. 92-102 ◽  
Author(s):  
Nicholas Haritos ◽  
Anil Hira ◽  
Priyan Mendis ◽  
Rob Heywood ◽  
Armando Giufre
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Flexural Rigidity ◽  
Load Capacity ◽  
Limit State ◽  
Dynamic Test ◽  
Service Condition ◽  
Flat Slab ◽  
Testing Program ◽  
Static Testing

VicRoads, the road authority for the state of Victoria, Australia, has been undertaking extensive research into the load capacity and performance of cast-in-place reinforced concrete flat slab bridges. One of the key objectives of this research is the development of analytical tools that can be used to better determine the performance of these bridges under loadings to the elastic limit and subsequently to failure. The 59-year-old Barr Creek Bridge, a flat slab bridge of four short continuous spans over column piers, was made available to VicRoads in aid of this research. The static testing program executed on this bridge was therefore aimed at providing a comprehensive set of measurements of its response to serviceability level loadings and beyond. This test program was preceded by the performance of a dynamic test (a simplified experimental modal analysis using vehicular excitation) to establish basic structural properties of the bridge (effective flexural rigidity, EI) and the influence of the abutment supports from identification of its dynamic modal characteristics. The dynamic test results enabled a reliably tuned finite element model of the bridge in its in-service condition to be produced for use in conjunction with the static testing program. The results of the static testing program compared well with finite element modeling predictions in both the elastic range (serviceability loadings) and the nonlinear range (load levels taken to incipient collapse). Observed collapse failure modes and corresponding collapse load levels were also found to be predicted well using yield line theory.

Error-aware Design Procedure to Implement Energy-efficient Approximate Squaring Hardware

2020 ◽  
Vol 10 (4) ◽  
pp. 471-477
Author(s):  
Merin Loukrakpam ◽  
Ch. Lison Singh ◽  
Madhuchhanda Choudhury
Keyword(s):  
Energy Saving ◽  
Relative Error ◽  
Energy Efficient ◽  
Piecewise Linear ◽  
Arithmetic Operation ◽  
Design Procedure ◽  
Digital Signal ◽  
Maximum Relative Error ◽  
Square Function ◽  
Efficient Design

Background:: In recent years, there has been a high demand for executing digital signal processing and machine learning applications on energy-constrained devices. Squaring is a vital arithmetic operation used in such applications. Hence, improving the energy efficiency of squaring is crucial. Objective:: In this paper, a novel approximation method based on piecewise linear segmentation of the square function is proposed. Methods: Two-segment, four-segment and eight-segment accurate and energy-efficient 32-bit approximate designs for squaring were implemented using this method. The proposed 2-segment approximate squaring hardware showed 12.5% maximum relative error and delivered up to 55.6% energy saving when compared with state-of-the-art approximate multipliers used for squaring. Results: The proposed 4-segment hardware achieved a maximum relative error of 3.13% with up to 46.5% energy saving. Conclusion:: The proposed 8-segment design emerged as the most accurate squaring hardware with a maximum relative error of 0.78%. The comparison also revealed that the 8-segment design is the most efficient design in terms of error-area-delay-power product.

scholarly journals Flexural bearing capacity and failure mechanism of CFRP-aluminum laminate beam with double-channel cross-section

2021 ◽  
Vol 28 (1) ◽  
pp. 139-152
Author(s):  
Teng Huang ◽  
Dongdong Zhang ◽  
Yaxin Huang ◽  
Chengfei Fan ◽  
Yuan Lin ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Bearing Capacity ◽  
Failure Mechanism ◽  
Cross Section ◽  
Failure Criterion ◽  
Failure Modes ◽  
Channel Cross Section ◽  
Fiber Layer ◽  
Flexural Bearing Capacity ◽  
Double Channel

Abstract In this study, the flexural bearing capacity and failure mechanism of carbon fiber-reinforced aluminum laminate (CARALL) beams with a double-channel cross-section and a 3/2 laminated configuration were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°]3 and [45°/0°/−45°]3) were fabricated using the pressure molding thermal curing forming process. The double-channel CARALL beams were subjected to static three-point bending tests to determine their failure behaviors in terms of ultimate bearing capacity and failure modes. Owing to the shortcomings of the two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for the ABAQUS/Explicit solver and an analysis algorithm were established to obtain a progressive damage prediction of the CFRP layer using the three-dimensional Hashin failure criterion. Various failure behaviors and mechanisms of the CARALL beams were numerically analyzed. The results indicated that the numerical simulation was consistent with the experimental results for the ultimate bearing capacity and final failure modes, and the failure process of the double-channel CARALL beams could be revealed. The ultimate failure modes of both types of double-channel CARALL beams were local buckling deformation at the intersection of the upper flange and web near the concentrated loading position, which was mainly caused by the delamination failure among different unidirectional plates, tension and compression failure of the matrix, and shear failure of the fiber layers. The ability of each fiber layer to resist damage decreased in the order of 90° fiber layer > 0° fiber layer > 45° fiber layer. Thus, it is suggested that 90°, 0°, and 45° fiber layers should be stacked for double-channel CARALL beams.

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