Elastic Follow-Up Factor for Cruciform Plate Under Bi-Axial Loading

2011 ◽  
Author(s):  
Kuk-Hee Lee ◽  
Yun-Jae Kim ◽  
Robert A. Ainsworth ◽  
David Dean ◽  
Tae-Eun Jin
Keyword(s):  
Finite Element ◽  
Power Law ◽  
Analytical Solutions ◽  
Axial Stress ◽  
Axial Loading ◽  
Finite Element Analyses ◽  
Structural Discontinuity ◽  
Stress States ◽  
Power Law Creep

This paper derives analytical solutions of the elastic follow-up factor for power-law creeping cruciform plates under bi-axial displacements to investigate the effect of multi-axial stress states on elastic follow-up behaviors. Validity of the proposed solutions is checked against the results from finite element analyses using power-law creep material. Based on proposed solutions, effects of the biaxiality, geometry, Poisson’s ratio and creep exponent on elastic follow-up factors are discussed. Present results show that the elastic follow-up factor for structure with structural discontinuity can be significantly affected by the multi-axial stress states.

Effects of sections added to multi-cell square tubes on crash performance

2020 ◽  
Vol 62 (5) ◽  
pp. 471-480 ◽  
Author(s):  
Emre İsa Albak
Keyword(s):  
Finite Element ◽  
Genetic Algorithms ◽  
Radial Basis Functions ◽  
Axial Loading ◽  
Basis Functions ◽  
Finite Element Analyses ◽  
Energy Absorber ◽  
Radial Basis ◽  
Crash Performance

Abstract In this study, the effects of sections added to multi-cell square tubes on crash performance are examined. Square, hexagonal and circular sections are added to multi-cell square tubes and their results are examined. Finite element analyses under axial loading are performed to examine the crash performance of the multi-cell tubes. Analyses show that by adding a section to the multi-cell square tubes. the crash behavior of the tubes is improved. According to the results, S5H multi-cell square tube reveals the best crash performance. The optimization of S5H is carried out by using genetic algorithms and radial basis functions. The S5H tube presents a good crashworthiness performance and could be used as an energy absorber.

Developing a Durability by Design Process

2009 ◽  
Author(s):  
John Draper
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Analytical Solutions ◽  
Endurance Limit ◽  
Complex Loading ◽  
Fatigue Analysis ◽  
Biaxial Stress ◽  
Finite Element Models ◽  
Critical Plane ◽  
Stress States

Modern fatigue analysis is providing analytical solutions to problems that could previously be addressed only by methods that were highly empirical and often inaccurate. We can now focus on five crucial steps to successful fatigue analysis. Working from elastic finite element models, the five steps are: 1) the calculation of elastic-plastic stresses and strains for complex loading and biaxial stress states; 2) modification of the endurance limit to allow for the interaction between small and larger cycles; 3) the calculation of the life to crack initiation; 4) critical plane searching to determine the orientation of a potential crack; 5) and an assessment of whether the crack will propagate to failure. The paper describes these steps and the underlying theories, and gives industrial examples of their application to real components.

Computational and Experimental Characterization of Indentation Creep

2003 ◽  
Vol 795 ◽  
Author(s):  
Ming Dao ◽  
Hidenari Takagi ◽  
Masami Fujiwara ◽  
Masahisa Otsuka
Keyword(s):  
Finite Element ◽  
Power Law ◽  
Constant Load ◽  
Dislocation Creep ◽  
Solid Solution Alloy ◽  
Indentation Creep ◽  
Creep Tests ◽  
Uniaxial Creep ◽  
Self Similar ◽  
Power Law Creep

ABSTRACT:Detailed finite-element computations and carefully designed indentation creep experiments were carried out in order to establish a robust and systematic method to accurately extract creep properties during indentation creep tests. Finite-element simulations confirmed that, for a power law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent, n, the activation energy for creep, Qc and so on can be evaluated robustly. Samples made from an Al-5.3mol%Mg solid solution alloy were tested at temperatures ranging from 573 K to 773 K. The results are in good agreement with those obtained from conventional uniaxial creep tests in the dislocation creep regime.

Finite Element Simulation for Creep Response of Strengthened Wood/PVC Composite

2013 ◽  
Vol 747 ◽  
pp. 261-264 ◽  
Author(s):  
T. Pulngern ◽  
K. Preecha ◽  
Narongrit Sombatsompop ◽  
V. Rosarpitak
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Power Law ◽  
High Carbon Steel ◽  
Creep Model ◽  
Element Analysis ◽  
Creep Response ◽  
Element Simulation ◽  
Before And After ◽  
Power Law Creep

This paper investigates the finite element simulation to predict the creep response of Wood/PVC (WPVC) composite members before and after strengthening by using high carbon steel (HCS) flat bar strip adhered to the tension side. The creep parameters based on power law models of WPVC composites and the HCS flat bars were determined experimentally. Then, the nonlinear finite element analysis (FEA) software of ABAQUS was applied to predict the creep behaviors of composite members using the obtained experimentally creep parameters of individual component of WPVC composites and HCS flat bars. Good correlation between finite element simulation and experimental results are obtained for all cases. ABAQUS software with power law creep model show good potential for prediction the creep response of WPVC composites before and after strengthening.

Bounded Elastic Moduli Multiplier Technique for Limit Loads: Part 1 - Theory

2022 ◽  
Author(s):  
Sathya Prasad Mangalaramanan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Lower Bound ◽  
Power Law ◽  
Elastic Moduli ◽  
Stress Distributions ◽  
Finite Element Analyses ◽  
Element Analysis ◽  
Limit Loads ◽  
Reduced Modulus

Abstract Statically admissible stress distributions are necessary to evaluate lower bound limit loads. Over the last three decades, several methods have been postulated to obtain these distributions using iterative elastic finite element analyses. Some of the pioneering techniques are the reduced modulus, r-node, elastic compensation, and linear matching methods, to mention a few. A new method, called the Bounded Elastic Moduli Multiplier Technique (BEMMT), is proposed and the theoretical underpinnings thereof are explained in this paper. BEMMT demonstrates greater robustness, more generality, and better stress distributions, consistently leading to lower-bound limit loads that are closer to elastoplastic finite element analysis estimates. BEMMT also questions the validity of the prevailing power law based stationary stress distributions. An accompanying research offers several case studies to validate this claim.

Shakedown of Thick Cylinders With Radial Openings Under Thermomechanical Loadings

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
X. T. Zheng ◽  
F. Z. Xuan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Axial Stress ◽  
Assessment Methods ◽  
Element Analysis ◽  
Stress States

Shakedown and ratcheting behaviors of thick-walled cylindrical vessels with radial openings subjected to cyclic thermomechanical loadings are investigated by the inelastic finite element analysis. Different shakedown and ratcheting responses are described in the modified Bree diagram considering the influences of various opening radius ratios ri/Ri, thickness ratios Ro/Ri as well as different axial stress states. Then, two simplified shakedown assessment methods of perforated cylinders are discussed. The results indicate that elastic/plasticity shakedown boundary reduces significantly owing to the presence of a radial opening while varies slightly with the opening radius, which can be defined as 1.2 approximately in the modified Bree diagram for conservative elastic/plasticity shakedown evaluation. Moreover, shakedown/ratcheting boundary decreases significantly with increasing the opening radius or decreasing the axial stress. Finally, comparing with the calculated results, the two simplified methods are verified to be accurate and intuitive to estimate the shakedown behaviors of perforated cylinders under various thickness and opening radius conditions.

The Effect of Material Models on Elastic Follow-Up

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
James T. Boyle
Keyword(s):  
Power Law ◽  
Maximum Stress ◽  
Primary Creep ◽  
Stress Range ◽  
Element Analysis ◽  
Material Models ◽  
Design Rules ◽  
Strain Trajectory ◽  
Power Law Creep

The phenomenon of elastic follow-up in high temperature piping has a long history and rules to limit its significance in design are well established. However, most design rules, and numerous associated supporting studies, have been limited to a simple power-law of creep, with variations to account for time- or strain-hardening in primary creep. A common feature of the most studies of elastic follow-up in structures subject to power-law creep is that a plot of (maximum) stress against strain—a so-called isochronous stress– strain trajectory—is almost insensitive to the creep law (in particular, the stress exponent in the power-law) and is almost linear (until perhaps the later stages of stress relaxation). A limitation of the power-law is that it assumes to be valid across all stress ranges, from low through moderate to high, yet it is well known that this is not generally the case. This paper aims to investigate the effect of stress-range dependent material models on the nature of elastic follow-up: both a simple two-bar structure (common in studies of elastic follow-up) and a detailed finite element analysis of a piping elbow are examined. It is found that stress-range dependent material models can have a significant effect on the accepted characteristics of elastic follow-up.

Effects of Weld Geometry on Stress Intensity Factor Solutions for Laser Welds in Lap-Shear Specimens

2011 ◽  
Author(s):  
Kulthida Sripichai ◽  
Kamran Asim ◽  
Jwo Pan
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Analytical Solutions ◽  
Finite Element Analyses ◽  
Weld Geometry ◽  
Lap Shear ◽  
Laser Welds ◽  
Beam Bending

In this paper, the effects of weld geometry on the stress intensity factor solutions for laser welds in lap-shear specimens are investigated. Analytical stress intensity factor solutions for laser welded lap-shear specimens based on the beam bending theory are derived and compared with the analytical solutions for two semi-infinite solids with connection. Finite element analyses of laser welded lap-shear specimens with different weld widths were also conducted to obtain the stress intensity factor solutions. Approximate closed-form stress intensity factor solutions based on the results of the finite element analyses in combination with the analytical solutions based on the beam bending theory and Westergaard stress function for a full range of the normalized weld widths are developed for use with the stress intensity factor solutions for kinked cracks to correlate and estimate fatigue lives of laser welded lap-shear specimens. The effects of the weld protrusion on the stress intensity factor solutions for the pre-existing cracks in lap-shear specimens are also investigated. The presence of the weld protrusion decreases the stress intensity factor solutions for the pre-existing crack near the weld protrusion for the load carrying sheets and the lower stress intensity factor solutions can be used to explain more favorable conditions for kinked fatigue crack propagation from the other pre-existing crack tip and to estimate fatigue lives of laser welded lap-shear specimens under high cycle loading conditions as observed in experiments.

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