scholarly journals Calculated Shoulder to Gauge Ratio of Fatigue Specimens in PWR Environment

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 376
Author(s):  
Igor Simonovski ◽  
Alec Mclennan ◽  
Kevin Mottershead ◽  
Peter Gill ◽  
Norman Platts ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Water Environment ◽  
Hysteresis Loops ◽  
Constitutive Law ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Material Behaviour ◽  
Pressurized Water ◽  
Elastic Plastic ◽  
Gauge Section

A ratio of shoulder to gauge displacements (S2G) is calculated for three different fatigue specimens in a pressurized water environment. This ratio needs to be known beforehand to determine the applied shoulder displacements during the experiment that would result in the desired strain amplitude in the gauge section. Significant impact of both the applied constitutive law and specimen geometry on the S2G is observed. The calculation using the fully elastic constitutive law results in the highest S2G values and compares very well with the analytical values. However, this approach disregards the plastic deformation within the specimens that mostly develops in the gauge section. Using the constitutive laws derived from actual fatigue curves captures the material behaviour under cyclic loading better and results in lower S2G values compared to the ones obtained with the fully elastic constitutive law. Calculating S2G values using elastic–plastic constitutive law based on the monotonic uniaxial tensile test should be avoided as they are significantly lower compared to the ones computed with elastic–plastic laws derived from hysteresis loops at half-life.

Studies on Post-Yield Behavior of Cortical Bone

2012 ◽  
Vol 232 ◽  
pp. 157-161 ◽  
Author(s):  
N.K. Sharma ◽  
J. Nayak ◽  
D.K. Sehgal ◽  
R.K. Pandey
Keyword(s):  
Plastic Deformation ◽  
Cortical Bone ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Yield Behavior ◽  
Plastic Properties ◽  
Joint Replacements ◽  
Hierarchical Assembly ◽  
Plastic Modulus ◽  
Stiffness Loss

Complex hierarchical assembly and presence of large amount of organics and water content are responsible for enough amount of plasticity in bone material. Plastic properties are not only important to assess the various changes and fracture risk in bone but also for the development of better bone implants and joint replacements. The present study is focused on the post-yield behavior of cortical bone. The plastic properties of goat femoral and tibiae cortical bone were assessed and compared in terms of plastic modulus (H), tangent modulus (Et), plastic work (Wp) and plastic strain (εp) using uniaxial tensile test. Both femoral and tibiae cortical bone were found to be having similar post-yield behavior and significant stiffness loss was observed in both the bones during plastic deformation. The value of plastic modulus for femoral cortical bone was found to be 1.2 times higher as compared to the corresponding value for tibiae cortical bone. This shows higher hardening rate for femoral cortical bone. It was also observed that femoral bone requires higher energy during plastic deformation until fracture as compared to tibiae cortical bone.

Elasto-Plastic Analysis of a Miniature Circular Disk Bending Specimen

2006 ◽  
Author(s):  
Vishnu Verma ◽  
A. K. Ghosh ◽  
G. Behera ◽  
Kamal Sharma ◽  
R. K. Singh
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Yield Stress ◽  
Material Properties ◽  
Stable Solution ◽  
Bending Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Plastic Behavior ◽  
Element Analysis

Miniature disk bending test is used to evaluate the mechanical behavior of irradiated materials and its properties — mainly ductility loss due to irradiation in steel. In Miniature Disk Bending Machine the specimen is firmly held between the two horizontal jaws of punch, and an indentor with spherical ball travels vertically. Researchers have observed reasonable correlations between values of the yield stress, strain hardening and ultimate tensile strength estimated from this test and mechanical properties determined from the uniaxial tensile test. Some methods for the analysis of miniature disk bending, proposed by various authors have been discussed in the paper. It is difficult to distinguish between the regimes of elastic and plastic deformation since local plastic deformation occurs for very small values of load when the magnitude of spatially averaged stress will be well below the yield stress. Also, the analytical solution for large amplitude, plastic deformation becomes rather unwieldy. Hence a finite element analysis has been carried out. The finite element model, considers contact between the indentor and test specimen, friction between various pairs of surfaces and elastic plastic behavior. The load is increased in steps and converged solution has been obtained and analysis terminated at a load beyond which a stable solution cannot be obtained. A sensitivity study has been carried out by varying the various parameters defining the material properties by ±10% around the base values. This study has been carried out to generate a data base for the load-deflection characteristics of similar materials from which the material properties can be evaluated by an inverse calculation. It is seen that the deflection obtained by analytical elastic bending theory is significantly lower than that obtained by the elasto-plastic finite element solution at relatively small values of load. The FE solution and experimental results are in reasonably good agreement.

Influence of Stress Relaxation after Uniaxial Pre-Straining on Subsequent Plastic Yielding in the Uniaxial Tensile Test of Sheet Metal

2015 ◽  
Vol 639 ◽  
pp. 377-384 ◽  
Author(s):  
Sebastian Suttner ◽  
Marion Merklein
Keyword(s):  
Sheet Metal ◽  
Kinematic Hardening ◽  
Research Work ◽  
Load Condition ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Automotive Sector ◽  
Plastic Yielding ◽  
Material Behaviour ◽  
Strain Paths

Resource efficiency, design oriented accuracy and lightweight properties are demands on modern sheet metal forming parts in the automotive sector. The use of new materials leads to additional challenges on the numerical design of forming processes. During these forming processes the material undergoes different strain states that cause non-linear strain paths. Since the numerical prediction highly depends on the identified characteristic values of the material, an exact characterisation of the material behaviour is essential. Especially obtuse angles of the stress vector trigger a recovery of the material by returning stress. Besides, a relaxation of the material is investigated during holding a constant strain level. The effect of relaxation lead to an altered material behaviour that appears in a reduction of the beginning of plastic yielding. In addition, a kinematic hardening behaviour as under cyclic loading and load reversal, known as the Bauschinger effect, occurs after the relaxation of the stress and results in a reduced beginning of plastic yielding by loading in the same direction as the introduced pre-strain. Within this research work the effect of relaxation is investigated for two materials, AA5182 and DP600, with an initial sheet thickness of 1.0 mm. These materials are typically used for internal and accordingly functional parts in the automotive sector. The relaxation of the material is analysed with different holding times of a constant pre-strain at different levels of straining. The release of the material is studied by subsequent uniaxial tensile tests after pre-straining with the same load condition. Moreover, the influence of the named effects is shown by comparison of the translation of the yield loci.

Effect of Ductile Damage Evolution in Sheet Metal Forming: Experimental and Numerical Investigations

2010 ◽  
Vol 446 ◽  
pp. 157-169 ◽  
Author(s):  
Fethi Abbassi ◽  
Olivier Pantalé ◽  
Sébastien Mistou ◽  
Ali Zghal ◽  
Roger Rakotomalala
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Rolling Direction ◽  
Constitutive Law ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Plastic Behavior ◽  
Marquardt Algorithm

The numerical simulation based on the Finite Element Method (FEM) is widely used in academic institutes and in the industry. It is a useful tool to predict many phenomena present in the classical manufacturing forming processes such as necking, fracture, springback, buckling and wrinkling. But, the results of such numerical model depend strongly on the parameters of the constitutive behavior model. In the first part of this work, we focus on the traditional identification of the constitutive law using oriented tensile tests (0°, 45°, and 90° with respect to the rolling direction). A Digital Image Correlation (DIC) method is used in order to measure the displacements on the surface of the specimen and to analyze the necking evolution and the instability along the shear band. Therefore, bulge tests involving a number of die shapes (circular and elliptic) were developed. In a second step, a mixed numerical–experimental method is used for the identification of the plastic behavior of the stainless steel metal sheet. The initial parameters of the inverse identification were extracted from a uniaxial tensile test. The optimization procedure uses a combination of a Monte-Carlo and a Levenberg-Marquardt algorithm. In the second part of this work, according to some results obtained by SEM (Scaning Electron Microscopy) of the crack zones on the tensile specimens, a Gurson Tvergaard Needleman (GTN) ductile model of damage has been selected for the numerical simulations. This model was introduced in order to give informations concerning crack initiations during hydroforming. At the end of the paper, experimental and numerical comparisons of sheet metal forming applications are presented and validate the proposed approach.

OPTIMIZATION OF TAB GEOMETRY TO MINIMIZE LONGITUDINAL STRESS CONCENTRATION DURING TENSILE TESTING OF UNIDIRECTIONAL CFRP

2021 ◽  
Author(s):  
SHAILEE UPADHYAY ◽  
FRANCISCO MESQUITA ◽  
BABAK FAZLALI ◽  
LARISSA GORBATIKH ◽  
YENTL SWOLFS
Keyword(s):  
Tensile Strength ◽  
Tensile Testing ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Longitudinal Stress ◽  
Stress Concentrations ◽  
Premature Failure ◽  
Longitudinal Tensile Strength ◽  
Working Zone ◽  
Gauge Section

A uniaxial tensile test is a useful method for determination of material properties, especially longitudinal tensile strength. To accurately derive the longitudinal tensile strength, it is desired that the specimen fails in in the gauge section defined here as ‘working zone’. Unidirectional (UD) composites require use of end tabs during this tensile testing to avoid damage to the specimen due to grip serrations. The grip pressure, along with sudden geometry change at the edge of end tabs leads to longitudinal stress concentrations. The conventionally used rectangular and tapered end tabs suffer from these longitudinal stress concentrations under the edge of end tabs, causing premature failure of specimen outside of the working zone. In the present paper, a simulation study is performed for comparison of conventional end tabs with hybrid specimen geometry [1] and a novel arrow-shaped end tab geometry to determine the effect of end tab geometry on longitudinal stress concentrations. The study is focused on high modulus carbon fibre HS40/epoxy UD (0°) composite. The numerical model replicates the actual set-up for uniaxial tensile testing, including contact interactions between testing machine components. The simulation results are used to further optimise the geometry and provide recommendations to eliminate or minimise longitudinal stress concentrations.

Understanding Plastic Deformation Mechanism(s) in Recrystallized Zircaloy-4

2017 ◽  
Author(s):  
N. Kumar ◽  
A. Alomari ◽  
K. L. Murty
Keyword(s):  
Plastic Deformation ◽  
Stress Relaxation ◽  
Deformation Mechanism ◽  
Uniaxial Tensile ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Plastic Deformation Mechanism ◽  
Uniaxial Tensile Testing ◽  
Relaxation Experiments ◽  
Insight Into

It is essential to understand basic deformation mechanism(s) of conventional alloys in order to develop improved or novel alloys for their applications in much more challenging conditions. Zircaloy-4 is extensively used in pressurized water reactor for nuclear fuel cladding application. It operates at very high temperature in the presence of mechanical loads, corrosive atmosphere, and neutron irradiation environment. Present work explores the fundamental plastic deformation mechanism(s) of Zircaloy-4 in the temperature range 20 to 600 °C by subjecting tensile samples to uniaxial tensile loads under quasi-static deformation conditions. Based on the results of uniaxial tensile testing as a function of temperature, repeated stress-relaxation experiments were carried out to determine the activation volume of the alloy at 20 and 500 °C. The results from uniaxial tensile and stress-relaxation testing were used to gain insight into potential deformation mechanism(s) in Zircaloy-4.

scholarly journals Numerical simulation of the functionality of a stent structure for venous valve prostheses

2019 ◽  
Vol 5 (1) ◽  
pp. 477-479
Author(s):  
Julia Schubert ◽  
Kerstin Schümann ◽  
Sabine Kischkel ◽  
Wolfram Schmidt ◽  
Niels Grabow ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Minimally Invasive ◽  
Constitutive Law ◽  
Long Term Results ◽  
Uniaxial Tensile ◽  
Common Disease ◽  
Uniaxial Tensile Test ◽  
Venous Valve ◽  
Valve Prostheses ◽  
Venous Vessel

AbstractChronic venous insufficiency (CVI) is a common disease characterized by impaired venous drainage leading to congestion in the lower limbs. Currently, there are no artificial or biological venous valve prostheses commercially available. Previous minimally invasive design concepts failed to achieve sufficient long term results in animal or in vitro studies. The aim was to implement structural numerical simulation of clinically relevant loading cases for minimally invasive implantable venous valve prostheses. A bicuspid valve design was chosen as it showed superior results compared to tricuspid valves in previous studies. The selfexpanding support structure was developed by using diamond-shaped elements. Using finite-element analysis (FEA), various loading cases, including expansion and crimping of the stent structure and the release into a venous vessel, were simulated. A hyperelastic constitutive law for the vascular model was generated from uniaxial tensile test data of unfixated human vein walls. This study also compared numerical and experimental results regarding compliance and tensile tests to validate the vein material model. The calculated performance concerning expansion and crimping, as well as the release of the stent into a venous vessel, demonstrated the suitability of the stent design for minimally invasive application.

Anisotropic Damage Evolution for Perforated Sheet under Tensile Deformation

2016 ◽  
Vol 725 ◽  
pp. 489-494
Author(s):  
Shigeru Nagaki ◽  
Daigo Saboi ◽  
Kenta Muroi ◽  
Makoto Iizuka ◽  
Kenichi Oshita
Keyword(s):  
Plastic Deformation ◽  
Void Growth ◽  
Damage Evolution ◽  
Tensile Deformation ◽  
Yield Function ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Thermodynamic Consideration ◽  
Perforated Sheets ◽  
Growth Of Voids

It is important to formulate a constitutive equation which represents the growth of voids during plastic deformation in order to predict ductile fracture of metallic materials. For this purpose, we proposed an anisotropic Gurson’s yield function with the damage tensor, which represents the anisotropy due to the void distribution and the damage evolution was assumed isotropic for simplicity. Then we also proposed an anisotropic void growth law derived from the anisotropic Gurson’s yield function based on thermodynamic consideration. In this study we carried out the uniaxial tensile test of perforated sheets of stainless steel and aluminum alloy as the ideal two dimensional model of the damaged material and investigate the damage growth during plastic deformation. As a result, we obtained a good agreement between the experimental and the calculated void growth for both materials and it is also found that material parameters for damage evolutions are almost the same for both materials and are hardly affected by the work-hardening exponent.

Surface Roughening and Formability in Sheet Metal Forming of Polycrystalline Metal

2013 ◽  
Vol 535-536 ◽  
pp. 231-234 ◽  
Author(s):  
Takeji Abe
Keyword(s):  
Plastic Deformation ◽  
Sheet Metal ◽  
Uniaxial Tensile ◽  
Surface Irregularity ◽  
Surface Roughening ◽  
Uniaxial Tensile Test ◽  
Polycrystalline Metal ◽  
Biaxial Stretching ◽  
R Value ◽  
The Difference

The r–value is defined as the ratio of the width strain to the thickness strain under the uniaxial tensile test of the sheet metal. Based on r-value of grains, a model of plastic deformation of polycrystalline metal and surface roughening after plastic deformation was proposed in the previous paper. Meanwhile, Marciniak and Kuczynski proposed the so-called M-K model which give the analytical estimation of the formability of sheet metal under biaxial stretching considering a certain irregularity of the thickness of the sheet metal. Yamaguchi et al showed that the experimentally measured surface roughness may correspond to the surface irregularity suggested in the M-K model. In the present paper, the formability of sheet metal under biaxial stretching is analyzed based on the previous analysis of surface roughening caused by the difference of the r-value in the sheet metal.

Bifurcation in Elastic-Plastic Plates

1978 ◽  
Vol 5 (2) ◽  
pp. 79-88
Author(s):  
R.N. Dubey
Keyword(s):  
Plastic Deformation ◽  
Uniaxial Compression ◽  
Plastic Flow ◽  
Isotropic Material ◽  
Flow Rule ◽  
Material Behaviour ◽  
Incremental Theory ◽  
Elastic Plastic ◽  
Conventional Analysis ◽  
Plastic Flow Rule

It is shown that the isotropic material behaviour assumed in the classical incremental theory has two distinct implications, one for elastic deformation and another one for plastic deformation. This inconsistency has been removed by modifying the plastic-flow rule. The modified constitutive relation is used to calculate bifurcation stress in elastic-plastic plates under uniaxial compression. The bifurcation model used in the analysis is a generalized version of Shanley’s model – here restriction is placed on the amplitude of perturbation as opposed to restriction on the increase or rate of traction imposed in conventional analysis. The bifurcation stress thus obtained is significantly lower than the corresponding stress obtained from the classical incremental theory.

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