Safety Assessment of Steels and Welds Under Cyclic and Monotonic Loadings at Low Temperatures

1984 ◽  
Vol 106 (4) ◽  
pp. 473-479
Author(s):  
N. Urabe ◽  
A. Yoshitake ◽  
H. Kagawa
Keyword(s):  
Fracture Toughness ◽  
Fatigue Life ◽  
Brittle Fracture ◽  
Low Temperatures ◽  
Safety Assessment ◽  
Loading Rate ◽  
Fracture Initiation ◽  
Fatigue Tests ◽  
Loading Rates ◽  
Wide Range

In order to investigate the mechanisms and the factors to govern the brittle fracture initiation during the fatigue crack propagation at low temperatures, fracture toughness tests under wide range of loading rates, fatigue tests at low temperatures and fracture toughness tests after having been given pre-loading were performed on steels and weld junctions. The fatigue fracture toughness Kfc was estimated as equivalent as the fracture toughness Kc under the monotonic tensile loading if they were compared at the same loading rate, since the residual stress due to the cyclic loading was less effective on the brittle fracture initiation. The calculated fatigue life based on Paris’s formula taken into consideration of the crack closure phenomena showed a good one-by-one agreement with the observed fatigue life up to the brittle fracture initiation. Therefore, a design curve was preliminarily drawn to determine the fatigue life at low temperatures.

Discussion of a New Experimental Method in Measuring Fracture Toughness Initiation at High Loading Rates by Stress Waves

1982 ◽  
Vol 104 (1) ◽  
pp. 29-35 ◽  
Author(s):  
J. R. Klepaczko
Keyword(s):  
Fracture Toughness ◽  
Experimental Method ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Fracture Initiation ◽  
High Loading ◽  
Screening Tests ◽  
Hopkinson Pressure Bar ◽  
Loading Rates ◽  
Wide Range

An experimental method is described for measuring the fracture initiation properties of metals and alloys over a wide range of loading rates, which can cover over six orders of magnitude in K˙I (1 MPam s−1 ≤ K˙I ≤ 106 MPam s−1). With some modification of the standard compact tension specimen, a large series of screening tests can be performed in the high loading region at a relatively low cost. At the lower loading rates a standard closed loop testing machine can be used. To evaluate fracture initiation at a very high loading rate, a special arrangement of the split Hopkinson pressure bar has been proposed. Specimens of the same geometry as those used in quasi-static tests are placed between the Hopkinson bars. Since the wedge is attached to the incident bar, and the specimen is backed by the transmitter bar (Fig. 2), the course of specimen loading and fracturing can be exactly monitored by recording the incident, reflected and transmitted longitudinal waves. Using this technique, fracture initiation of the prefatigued specimen has been achieved within ∼ 20 μs after the beginning of specimen loading. The effects of inertia acting on the specimen and an error introduced by friction are both considered. Experiments performed on some aluminum alloys as well as on medium carbon steel revealed a complicated pattern of the fracture toughness behavior. Generally, for the strain rate sensitive materials a substantial decrease in fracture toughness was observed under high loading rates.

scholarly journals Creep Behavior of Passive Bovine Extraocular Muscle

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Lawrence Yoo ◽  
Hansang Kim ◽  
Andrew Shin ◽  
Vijay Gupta ◽  
Joseph L. Demer
Keyword(s):  
Relaxation Function ◽  
Loading Rate ◽  
Creep Function ◽  
Testing Conditions ◽  
Loading Rates ◽  
Creep Coefficient ◽  
Wide Range ◽  
The Mean

This paper characterized bovine extraocular muscles (EOMs) using creep, which represents long-term stretching induced by a constant force. After preliminary optimization of testing conditions, 20 fresh EOM samples were subjected to four different loading rates of 1.67, 3.33, 8.33, and 16.67%/s, after which creep was observed for 1,500 s. A published quasilinear viscoelastic (QLV) relaxation function was transformed to a creep function that was compared with data. Repeatable creep was observed for each loading rate and was similar among all six anatomical EOMs. The mean creep coefficient after 1,500 seconds for a wide range of initial loading rates was at1.37±0.03(standard deviation, SD). The creep function derived from the relaxation-based QLV model agreed with observed creep to within 2.7% following 16.67%/s ramp loading. Measured creep agrees closely with a derived QLV model of EOM relaxation, validating a previous QLV model for characterization of EOM biomechanics.

Relationship Between Fatigue Life Distribution, Notch Configuration, and S-N Curve of a 2024-T4 Aluminum Alloy

1985 ◽  
Vol 107 (3) ◽  
pp. 214-220 ◽  
Author(s):  
T. Shimokawa ◽  
Y. Hamaguchi
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stress Amplitude ◽  
Fatigue Tests ◽  
Test Results ◽  
Notched Specimens ◽  
Wide Range ◽  
Life Distributions ◽  
The Relationship ◽  
Test Stress

The objective of this study is to identify the most closely related variable to the distribution of fatigue life in unnotched and three kinds of notched 2024-T4 aluminum alloy specimens. Carefully designed fatigue tests under a constant temperature and humidity condition provided fatigue life distributions over a wide range of stress amplitude. This study used about 1000 specimens. On the basis of the test results, the dependence of the scatter in fatigue life on notch configuration, the period to crack initiation, the level of stress amplitude, the median fatigue life, and the slope of the median S-N curve is investigated, and the relationship between the distributional form of fatigue life and the shape of the median S-N curve is discussed. It is concluded that the slope and shape of the median S-N curve in the vicinity of the test stress level are closely related to the scatter and distributional form of fatigue life respectively. This is common to the unnotched and three kinds of notched specimens. A variability hypothesis to correlate the median S-N curve with fatigue life distributions is examined.

Serrated Plastic Flow of Various Metallic Glasses during Nanoindentation

2016 ◽  
Vol 368 ◽  
pp. 3-6
Author(s):  
Mária Huráková ◽  
Kornel Csach ◽  
Jozef Miškuf ◽  
Alena Juríková ◽  
Štefan Demčák ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Plastic Flow ◽  
Metallic Glasses ◽  
Alloy Composition ◽  
Loading Rate ◽  
Glass Forming Ability ◽  
Loading Rates ◽  
Glass Forming ◽  
Wide Range ◽  
The Individual

Nanoindentation experiments were executed on amorphous metallic ribbons made of Fe40Ni40B20, Cu47Ti35Zr11Ni6Si1 and Zr65Cu17.5Ni10Al7.5 that differ in microhardness and glass forming ability. The individual serrated plastic flow events were analyzed in a wide range of the loading rates. In the individual pop-in events of the load-displacement (P-h) curve the contributions of plastic deformation (Δhpl) were calculated depending on the loading rate and the alloy composition. It is concluded that the contribution of the serrated plastic deformation flow varies with the composition of the alloy. The highest plastic deformation for the individual pop-ins was observed for Zr-based metallic glasses.

Fatigue of Zirconia - Bioglass Dental Ceramics

2008 ◽  
Vol 591-593 ◽  
pp. 628-633 ◽  
Author(s):  
Luiz A. Bicalho ◽  
R.C. Souza ◽  
Claudinei dos Santos ◽  
M.J.R. Barboza ◽  
Carlos Antonio Reis Pereira Baptista
Keyword(s):  
Fracture Toughness ◽  
Fatigue Life ◽  
Bending Strength ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Modulus Of Rupture ◽  
Dental Ceramics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Four Point Bending

In this work the cyclic fatigue life of 3mol.%Y2O3-stabilized zirconia polycrystalline ceramics, doped with 5%wt 3CaO.P2O5,-SiO2-MgO, has been investigated. Samples with 5 and 10%wt were cold uniaxial pressed (80MPa) and sintered in air at 1200 and 1300oC for 120 minutes. Sintered samples were characterized by X-Ray diffraction and Scanning Electronic Microscopy. Hardness and fracture toughness were determined using Vicker’s indentation method, and Modulus of Rupture was determined by four-point bending testing. Furthermore, the cyclic fatigue tests were also realized by four-point bending tests, under frequency of 25 Hz and stress ratio, R, of 0.1, for the best condition. In this condition, highly dense samples were obtained and presented values of hardness, fracture toughness and bending strength of 11.3 ±0.1GPa, 6.1±0.4MPa.m1/2 and 320±55MPa, respectively. The increasing of stress level leads to decreasing of the number of cycles and the number of run-out specimens. The stress induced tetragonal-monoclinic (t-m)-ZrO2 transformation, observed by X-Ray diffraction, contributes to the increasing of the fatigue life. Samples 3Y-TZP presents clearly a range of loading conditions where cyclic fatigue can be detected.

scholarly journals Adhesion Strength of Al/Epoxy Resin Interface over a Wide Range of Loading Rates

2021 ◽  
Vol 250 ◽  
pp. 01003
Author(s):  
Yoshikatsu Kimoto ◽  
Kohei Kanamori ◽  
Akio Yonezu ◽  
Hiroyuki Yamada
Keyword(s):  
Aluminium Alloy ◽  
Epoxy Resin ◽  
Adhesion Strength ◽  
Loading Rate ◽  
Rate Dependency ◽  
Loading Rates ◽  
Wide Range ◽  
Significant Loading ◽  
Static Tensile ◽  
Split Hopkinson

This study evaluated the interfacial adhesive strength between aluminium alloy and epoxy resin (Al/epoxy resin) over a wide range of strain rates (loading rates). We conducted three types of tests with different loading rate, i.e., a quasi-static tensile test for the range of lower loading rate, a Split Hopkinson Bar (SHB) for the range of middle loading rate, and Laser Shock Adhesion Test (LaSAT) for the range of higher loading rate. LaSAT is a unique test of adhesion evaluation, since laser induced shock wave is employed to lead interfacial fracture. In parallel, finite element method (FEM) is conducted in order to calculate stress distribution at the interface during LaSAT. As a result, it was found that the interface between the aluminium alloy and the epoxy resin interface shows significant loading rate dependency of the adhesion strength and this tendency is very similar to that of bulk epoxy materials.

Effect of loading rate on cohesive parameters of the adhesive Araldite 2015

2020 ◽  
Vol 62 (9) ◽  
pp. 943-950
Author(s):  
Engin Erbayrak ◽  
Halil Ozer
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Fracture Energy ◽  
Transition Region ◽  
Cantilever Beam ◽  
Epoxy Matrix ◽  
Loading Rate ◽  
Double Cantilever Beam ◽  
Loading Rates ◽  
Softening Behavior

Abstract This study addresses the effect of loading rates on cohesive parameters and microstructural composition of the Araldite 2015 adhesive. Double Cantilever Beam (DCB) samples were tested under the loading rates of 1, 5, 10, 20, 100 and 200 mm × min-1. The Park-Paulinho-Roeser model (PPR model) was used to get cohesive parameters. In modelling of the softening behavior, inverse analyses were performed using the date obtained from the PPR softening curves. It was seen that the fracture energy and cohesive parameters are decreasing with increasing the loading rate. However, there seems to be a transition region where the fracture energy nearly remains constant. Microstructural analyses were implemented in order to study the effects of the loading rates on the characteristics of the fracture surfaces. It was concluded that the loading rates greatly influence the distribution of micro-voids in the epoxy matrix. Moreover, the presence of voids in epoxy matrix improved the plastic deformation around the crack tip and increased the fracture toughness.

Enhancement of Fatigue Life in St37 Steels by Carburizing Process

2021 ◽  
Vol 105 ◽  
pp. 59-67
Author(s):  
Jalal Joudaki ◽  
Mehdi Safari
Keyword(s):  
Fatigue Life ◽  
Fatigue Tests ◽  
Diffusivity Coefficient ◽  
Bending Fatigue ◽  
Steel Material ◽  
Wide Range ◽  
Different Temperatures ◽  
St37 Steel ◽  
Fatigue Life Test ◽  
Carburizing Process

Carburizing is a heat treatment process, which used widely for surface hardening. In this process, the parts are placed in a concentrated atmosphere of Carbon atoms. The carbon atoms diffuse in the samples from the surface. In the present article, the effects of carburizing temperature on fatigue life will be studied. The St37 steel material is selected for study due to its wide range of usage in industry and little attention on the carburizing of this material. The samples are prepared by implementing the carburizing process at different temperatures (300, 400, 500, and 600 °C). The holding time is 1 hour for all samples. The two-point bending fatigue tests had been carried out on constant loading stresses. The results of the fatigue life test show that the fatigue life enhances the carburizing process. The fatigue life improved from about 45000 cycles to about 65000 cycles (about 44% increase) by increasing the temperature from 300°C to 600°C. Holding at higher temperatures leads to an increase in fatigue life smoothly due to the increase in the diffusivity coefficient. Also, the fracture surface demonstrates that the crack initiation starts from outer surfaces very slowly and failure happens as a brittle fracture in the samples.

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