scholarly journals Influence of graphite morphology on static and cyclic strength of ferritic nodular cast iron

2018 ◽  
Vol 165 ◽  
pp. 14014 ◽  
Author(s):  
Christian Gebhardt ◽  
Geng Chen ◽  
Alexander Bezold ◽  
Christoph Broeckmann
Keyword(s):  
Cast Iron ◽  
Nodular Cast Iron ◽  
Tensile Tests ◽  
Cyclic Strength ◽  
Fatigue Tests ◽  
Point Of View ◽  
Experimental Point ◽  
Suitable Material ◽  
Material Parameters ◽  
Perfectly Plastic

High silicon alloyed nodular cast iron consists of a purely ferritic matrix and graphite nodules, mainly. Varying wall thicknesses and manufacturing conditions result in different graphite morphologies throughout a structural component. From an experimental point of view, axial fatigue and tensile tests were carried out on specimens with differently degraded graphite. From a numerical point of view, the microstructure has been modelled using a finite element (FE) approach with representative volume elements (RVE). The RVE models were built according to micrographs of fatigue specimens. The generated RVEs determine effective material properties through elasto-plastic homogenization and were subsequently analysed using a shakedown approach. In shakedown theory, the material re-enters the elastic regime after a few cycles of initial plastic deformation. This work uses the shakedown theorem to derive a lower bound estimation of the endurance limit from a non-incremental simulation. Here, the material has to be modelled elastic-perfectly plastic. The major challenge in modelling nodular cast iron is to determine suitable material parameters for the graphite and ferrite phase, revealed by parameter studies on the static and cyclic model. By using reasonable material parameters, fundamental effects, observed in the fatigue tests, were reproduced on the model level.

Determination of In-plane Shear Strength of Unidirectional Composite Materials Using the Off-axis Three-point Flexure and Off-axis Tensile Tests

2010 ◽  
Vol 44 (21) ◽  
pp. 2487-2507 ◽  
Author(s):  
G. Vargas ◽  
F. Mujika
Keyword(s):  
Shear Strength ◽  
Composite Materials ◽  
Tensile Tests ◽  
Unidirectional Composite ◽  
Point Of View ◽  
Experimental Point ◽  
Plane Shear ◽  
Lift Off ◽  
Flexure Test

The aim of this work is to compare from an experimental point of view the determination of in-plane shear strength of unidirectional composite materials by means of two off-axis tests: three-point flexure and tensile. In the case of the off-axis three-point flexure test, the condition of small displacements and the condition of lift-off between the specimen and the fixture supports have been taken into account. Some considerations regarding stress and displacement fields are presented. The in-plane shear characterization has been performed on a carbon fiber reinforced unidirectional laminate with several fiber orientation angles: 10°, 20°, 30°, and 45°. Test conditions for both off-axis experimental methods, in order to ensure their applicability, are presented. Off-axis flexure test is considered more suitable than off-axis tensile test for the determination of in-plane shear strength.

scholarly journals Fatigue Properties of Nodular Cast Iron at Low Frequency Cyclic Loading

2017 ◽  
Vol 62 (4) ◽  
pp. 2205-2210 ◽  
Author(s):  
A. Vaško
Keyword(s):  
Cast Iron ◽  
Cyclic Loading ◽  
High Frequency ◽  
Stress Ratio ◽  
Low Frequency ◽  
Nodular Cast Iron ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Charge Composition ◽  
Cast Irons

Abstract Three melts of ferrite-pearlitic nodular cast iron with different charge composition were used for fatigue tests. Wöhler fatigue curves and fatigue strength were obtained, and microstructure and fracture surfaces were investigated. The aim of the paper is to determine the influence of charge composition on microstructure, mechanical and fatigue properties of synthetic nodular cast irons and their micromechanisms of failure. Fatigue tests were realised at low frequency sinusoidal cyclic push-pull loading (stress ratio R = −1) at ambient temperature (T = 20 ±5°C). They were carried out with using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100 at frequency f ≈ 120 Hz. The results of fatigue tests at low frequency cyclic loading are compared with fatigue properties at high frequency cyclic loading.

Influence of Stress Mode on Failure Micromechanisms of Nodular Cast Iron

2014 ◽  
Vol 693 ◽  
pp. 382-387 ◽  
Author(s):  
Alan Vaško ◽  
Milan Vaško
Keyword(s):  
Cast Iron ◽  
Nodular Cast Iron ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Bending Test ◽  
Metallographic Analysis ◽  
Cast Irons ◽  
Fracture Surfaces ◽  
Static Tensile ◽  
Different Content

The paper deals with comparison of the failure micromechanisms of nodular cast iron at static, impact and fatigue stress. Several specimens of ferrite-pearlitic nodular cast irons with different content of ferrite in a matrix were used for metallographic analysis, mechanical tests and microfractographic analysis. Mechanical properties were found out by static tensile test, impact bending test and fatigue tests. The microfractographic analysis was made with use of scanning electron microscope on fracture surfaces of the specimens fractured by these mechanical tests. Fracture surfaces of analysed specimens are characteristic of mixed mode of fracture. Failure micromechanism of nodular cast irons is dependent on mode of stress.

scholarly journals Consideration of the transient material behavior under variable amplitude loading in the fatigue assessment of nodular cast iron using the strain-life approach

2020 ◽  
Author(s):  
Jan Hesseler ◽  
Jörg Baumgartner ◽  
Christoph Bleicher
Keyword(s):  
Cast Iron ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Cyclic Hardening ◽  
Nodular Cast Iron ◽  
Fatigue Tests ◽  
Material Behavior ◽  
Strong Impact ◽  
Static Creep ◽  
Cyclic Relaxation

The consideration of realistic load assumptions is important for the fatigue design of highly stressed nodular cast iron components for wind energy application. Especially in case of overloads causing elastic-plastic deformation, residual stresses may have a strong impact on fatigue life. In strain-controlled fatigue tests with constant and variable amplitudes, the influence of overloads on the lifetime was investigated. The overload was applied with the objective to create high tensile residual stresses. During fatigue testing the transient material behavior, cyclic hardening, cyclic relaxation of the residual stresses as well as quasi static creep effects, of the EN-GJS-400-18-LT was recorded and evaluated. To quantify the influence of the transient material behavior on the calculated lifetime, fatigue analyses are carried out with the strain-life approach, both with and without consideration of the transient material behavior. The results show that conservative damage sums are derived if the transient material behavior, especially the relaxation of tensile residual stresses, is neglected.

scholarly journals Augmentation of Fatigue and Tensile Strength of AA-6061 Processed through Equal Channel Angular Pressing

2019 ◽  
Vol 38 (2) ◽  
pp. 435-442
Author(s):  
Nazeer Ahmed Anjum ◽  
Shahid Mehmood ◽  
Waqas Anwar ◽  
Zahid Sulman ◽  
Saeed Badshah
Keyword(s):  
Equal Channel Angular Pressing ◽  
Stress Ratio ◽  
Shear Plane ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Perfectly Plastic ◽  
Outer Corner ◽  
Angular Pressing ◽  
Hardness Tests ◽  
Point Bend

ECAP (Equal Channel Angular Pressing) is a technique used to enhance the strength of material by grain refinement. In this research, an aerospace grade aluminum alloy-6061 is investigated. The specimens were pressed through ECAP die channels, intersecting each other at an angle of 90oC where a shear plane of 45oC was developed, that results grains refinement. Fatigue strengths and CGR (Crack Growth Rate) for the stress ratio R 0.7 and 0.1 are found and compared with the as-received material.It was observed that the CGR is slower at stress ratio R=0.1, as compared to stress ration R=0.7. An electric furnace was embedded with ECAP die to regulate the material flow through this die. The temperature of the die was maintained at 450oC during ECAP pressing and the specimens were also preheated at this temperature using another furnace. The ECAP die consists of two channels intersecting at 90o provided with safe inner and outer corner radius to avoid scaling.The microstructural observations revealed that the deformation was perfectly plastic. The ECAPed and as-received materials were also characterized by tensile tests, micro-hardness tests, and 3-point bend fatigue tests.

scholarly journals Fatigue Properties Of Nodular Cast Irons Alloyed By Si, Mo And Cu

2019 ◽  
Vol 1 (1) ◽  
pp. 738-744
Author(s):  
Alan Vaško ◽  
Marek Krynke
Keyword(s):  
Cast Iron ◽  
Low Frequency ◽  
Hardness Test ◽  
Nodular Cast Iron ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Bending Test ◽  
Fatigue Properties ◽  
Cast Irons ◽  
Number Of Cycles

AbstractIn recent years, the research of nodular cast iron has been focused on increasing fatigue resistence. In the paper, two types of alloyed nodular cast irons have been investigated – SiMo-nodular cast iron alloyed by 4% of silicon and 1% of molybdenum and SiCu-nodular cast iron alloyed by 4% of silicon and 1.5% of copper. SiMo-nodular cast iron is suitable for high-temperature applications, for example the exhaust manifolds of the combustion engines. SiCu-nodular cast iron is used in various components of tribotechnical units. These components are often loaded by fatigue. The mechanical and fatigue behaviour of both nodular cast iron types has been studied by means of tensile test, impact bending test, hardness test and fatigue tests. Fatigue tests were realised at low frequency cyclic push-pull loading up to 10 million cycles. The relationship between the amplitude of stress and number of cycles to failure was investigated and the fatigue strength was determined. Mechanical and fatigue properties of both nodular cast iron types are correlated with the microstructure of specimens.

High-Tc superconductors from the experimental point of view

1988 ◽  
Vol 156 (9) ◽  
pp. 117-135 ◽  
Author(s):  
L.P. Gor'kov ◽  
N.B. Kopnin
Keyword(s):  
Point Of View ◽  
Experimental Point
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