Axially Compressed Cylindrical Shell Containing Axisymmetric Random Imperfections:

ABSTRACT This paper presents the comparison of reliability technique that employ Fourier series representations of random asymmetric imperfections in axially compressed cylindrical shell with evaluations prescribed by ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 and 2. The ultimate goal of the reliability type technique is to predict the buckling load associated with the axially compressed cylindrical shell. Initial geometric imperfections have significant effect on the load carrying capacity of asymmetrical cylindrical shells. Fourier decomposition is used to interpret imperfections as structural features can be easily related to the different components of imperfections. The initial functional description of the imperfections consists of an axisymmetric portion and a deviant portion appearing as a double Fourier series. The representation of initial geometrical imperfections in the cylindrical shell requires the determination of appropriate Fourier coefficients. The mean vector and the variance-covariance matrix of Fourier coefficients are calculated from the simulated shell profiles. Multi-mode analysis are expanded to evaluate a large number of potential buckling modes for both predefined geometries and associated asymmetric imperfections as a function of position within a given cylindrical shell. Large number of shells thus created can be used to calculate buckling stress for each shell. The probability of the ultimate buckling stress exceeding a predefined threshold stress can also be calculated. Keywords: Buckling; Asymmetric Imperfections; Fourier Series; Cylindrical Shell. NOMENCLATURE λ = Non-dimensional buckling load μ = Poisson"s ratio ξ i = Magnitude of imperfection as a fractional value of shell thickness θ = Non-dimensional number associated with the circumferential coordinates ξ = Non-dimensional number associated with the axial coordinates σ A (ξ) = Elements of Variance-covariance matrix C w0 (ξ 1 ,θ 1 ,ξ 2 ,θ 2 ) = Auto-covariance function k = Number of half waves in axial direction l = Number of full waves in circumferential direction P cl = Classical buckling load of a perfect shell P cr = Critical buckling load of a shell with imperfections Proceedings of IMECE2008 2008 ASME International Mechanical Engineering Congress and Exposition October 31-November 6, 2008, Boston, Massachusetts, USA Copyright©2008 by ASME 2 R = Radius of the shell E = Young"s Modulus L = Length of the shell t = Wall thickness of the shell D 0 = Outside diameter of the shell W n (ξ,θ) = Initial imperfection function IMECE2008-6879

BUCKLING LOAD PREDICTIONS IN PRESSURE VESSELS UTILIZING MONTE CARLO METHOD

In practice, large diameter, thin wall shells of revolution are never fabricated with constant diameters and thicknesses over the entire length of the assembly. These initial geometric imperfections have significant effect on the load carrying capacity of cylindrical shells. The cylindrical shell in the study is flue gas desulphurization (FGD) "vessel" which is a large hybrid tank-vessel-stack assembly in a major Canadian refinery. The function of the FGD vessel is to contain and support a proprietary process that utilizes an ammonium sulphate scrubbing system to produce environmentally friendly air emissions. FGD vessel stack has internal diameter of 6.1m, height of 45.34m and wall thickness of 9.525mm. Initial imperfections in FGD vessel is in the form of wall thickness variations. FGD wall thickness at 144 points along the circumference and elevation are measured. Monte Carlo method is employed to generate the measured data again. Test of significance is carried out to see the accuracy of the data generated. This Monte Carlo algorithm can be used to create data for any type of shell without spending time in actual measurements. Next, load carrying capacity of shell is determined considering imperfections to be axisymmetric and then asymmetric. Fourier decomposition is used to interpret imperfections as structural features can be easily related to the different components of imperfections. Further, double Fourier series is used to represent asymmetric initial geometric imperfections. The ultimate objective of these representations is to achieve a quantitative assessment of the critical buckling load considering the small axisymmetric and asymmetric deviations from the nominal cylindrical shell wall thickness. Analysis of cylindrical shells when used as pressure vessels and are under external pressure is also carried out. Comparison of reliability techniques that employ Fourier series representations of random axisymmetric and asymmetric imperfections in axially compressed cylindrical shells and shells under external pressure with evaluations prescribed by ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 and 2 is also carried out

Numerical investigation of friction crush welding aluminium and copper sheet metals with flanged edges

Aluminum alloys are the most attractive solutions for many industries including aerospace, marine, and other transportation sectors where lightweight construction is required. Friction Crush Welding (FCW) is a new material joining process that simultaneously creates a mechanical lock and a metallurgical seal at the interface between similar and dissimilar materials. In this research work presents the development of numerical modelling to predict the temperature distribution and mechanical performance of aluminum and copper similar joints in the FCW of sheet metal section. An explicit nonlinear transient finite element thermomechanical model is develop using ABAQUS based on the coupled Euler-Lagrange method to simulate FCW of AW5754 and Cu-DHP alloys. The Johnson-Cook materials law is adopted in the FEM. Numerical investigations of the FCW process was performed to reduce experimental testing times, which can be long and expensive. Temperature distribution and von misses stress flow patterns are observed at the top surface of the weld. Numerical simulation data correlate with experimental data in the literature

On rheological, mechanical, thermal, wear and morphological properties of melamine formaldehyde reinforced recycled ABS for sustainable manufacturing

This study outline the procedure of filament fabrication for fused deposition modelling (FDM), based upon rheological, mechanical, thermal, wear and morphological characterization as a case study of acrylonitrile butadiene styrene (ABS) - melamine formaldehyde (MF) composite. It has been ascertained that with increase in proportion of MF in ABS, viscosity is improved and melt flow index (MFI) is reduced significantly. As regards to the wear behavior is concerned it has been observed that ABS-MF (12.5 wt.%) composite has shown minimum weight loss and porosity. For the mechanical properties of the composite, experimental results show increased brittleness of the samples with addition of MF reinforcement. The thermal stability analysis was performed using differential scanning calorimetry (DSC) for virgin ABS and samples having 12.5% MF in ABS and results show the increased heat capacity of the material with increase in MF percentage. Further for sustainability analysis (based upon thermal stability), matrix of ABS-MF12.5% was subjected to three repeated thermal (heating-cooling) cycles and it has been ascertained that no significant loss was noticed in heat capacity of recycled composite matrix. The results are also supported by Fourier transform infrared spectroscopy (FTIR) analysis. Overall the results of the rheological, mechanical, wear, morphological and thermal properties suggested that 12.5% proportion of MF can be reinforced into selected grade of ABS thermoplastic for 3D printing as a sustainable solution

International Conference on Research and Innovations in Mechanical Engineering

This book comprises the proceedings of International Conference on Research and Innovations in Mechanical Engineering (ICRIME 2013) organized by Guru Nanak Dev Engineering College, Ludhiana with support from AICTE, TEQIP, DST and PTU, Jalandhar. This international conference served as a premier forum for communication of new advances and research results in the fields of mechanical engineering. The proceedings reflect the conference’s emphasis on strong methodological approaches and focus on applications within the domain of mechanical engineering. The contents of this volume aim to highlight new theoretical and experimental findings in the fields of mechanical engineering and closely related fields, including interdisciplinary fields such as robotics and mechatronics

Proceedings of the International Conference on Research and Innovations in Mechanical EngineeringICRIME-2013 /

XV, 682 p. 358 illus.online resource

PVP2009-77854 FOURIER SERIES ANALYSIS OF A CYLINDRICAL PRESSURE VESSEL SUBJECTED TO EXTERNAL PRESSURE

ABSTRACT This paper presents the comparison of a reliability technique that employs a Fourier series representation of random asymmetric imperfections in a cylindrical pressure vessel subjected to external pressure. Comparison with evaluations prescribed by the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2 Rules for the same shell geometries are also conducted. The ultimate goal of the reliability type technique is to predict the critical buckling load associated with the chosen cylindrical pressure vessel. Initial geometric imperfections are shown to have a significant effect on the load carrying capacity of the example cylindrical pressure vessel. Fourier decomposition is employed to interpret imperfections as structural features that can be easily related to various other types of defined imperfections. The initial functional description of the imperfections consists of an axisymmetric portion and a deviant portion, which are availed in the form of a double Fourier series. Fifty simulated shells generated by the Monte Carlo technique are employed in the final prediction of the critical buckling load. The representation of initial geometrical imperfections in the cylindrical pressure vessel requires the determination of appropriate Fourier coefficients. Multi-mode analyses are expanded to evaluate a large number of potential buckling modes for both predefined geometries and associated asymmetric imperfections as a function of position within a given cylindrical shell. The probability of the ultimate buckling stress that may exceed a predefined threshold stress is also calculated. The method and results described herein are in stark contrast to the "knockdown factor" approach as applied to compressive stress evaluations currently utilized in industry. Recommendations for further study of imperfect cylindrical pressure vessels are also outlined in an effort to improve on the current design rules regarding column buckling of large diameter pressure vessels designed in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, Division 2 and ASME STS-1