Effect of Competing Mechanisms on Fracture Toughness of Polycrystalline Metals

2015 ◽  
Author(s):  
Yan Li ◽  
Min Zhou
Keyword(s):  
Fracture Toughness ◽  
Failure Mechanisms ◽  
Fracture Mechanisms ◽  
Ductile Materials ◽  
Polycrystalline Metals ◽  
Inadequate Knowledge ◽  
Az31 Mg Alloy ◽  
Plastic Dissipation ◽  
Explicit Simulation ◽  
Material Fracture

Fracture toughness in ductile materials is the combined effect of the plastic dissipation and the energy spent in creating new surfaces. The design of polycrystalline metals with improved fracture toughness requires in-depth understanding of two levels of competitions: the competition between plastic deformation and crack formation as well as the competition between transgranular and intergranular fracture. Currently, no systematic approach exists to address the two competitions. The fundamental challenges lie in the difficulty in separating the two energy dissipations and inadequate knowledge about the correlation between fracture mechanisms and material fracture toughness. In this paper, a Cohesive Finite Element Method (CFEM) based multiscale framework is introduced to quantify the two levels of competitions. The fracture toughness of ductile materials is predicted by calculating the J-integral at the macroscale. The fracture surface energy for different type of failure mechanisms is evaluated through explicit simulation of crack propagation at the microstructure level. The calculations carried out here concern AZ31 Mg alloy. Results indicate that the mixed transgranular and intergranular failure can lead to optimized fracture toughness. Microstructures with refined grain size and grain boundary bonding strength can best promote the favorable failure mechanisms.

The Dimensionless Load Separation Method Used for Fracture Toughness Test and its Application

2011 ◽  
Vol 117-119 ◽  
pp. 460-466
Author(s):  
Kai Kai Shi ◽  
Li Xun Cai ◽  
Chen Bao ◽  
Yao Yao
Keyword(s):  
Fracture Toughness ◽  
316L Stainless Steel ◽  
Standard Test ◽  
Separation Method ◽  
Rotor Steel ◽  
Fracture Toughness Test ◽  
Ductile Materials ◽  
Resistance Curves ◽  
Load Separation ◽  
Material Fracture

One of tasks of fracture mechanics analysis is to get J resistance curves and fracture toughness of ductile materials. Based on the dimensionless theory, a modified Spb method from the load separation method was proposed. In order to apply load separation method to analysis the fracture toughness of a material from its test data, the testing application J-LSS (J resistance curve-Load Separation Software) has been developed by using visual basic (VB) language and was applied to obtain the fracture toughness values of Cr2Ni2MoV rotor steel and 316L stainless steel. Additionally, the differences between the traditional normalization method and the modified Spbmethod in analyzing fracture toughness through J-LSS were discussed. The modified Spbmethod presented in the paper is more available and can be recommended to renew the current material fracture toughness standard test.

Direct Observation of Fracture Mechanisms in Polymer-Layered Silicate Nanocomposites

1996 ◽  
Vol 457 ◽  
Author(s):  
Evangelos Manias ◽  
Wook Jin Han ◽  
Klaus D. Jandt ◽  
Edward J. Kramer ◽  
Emmanuel P. Giannelis
Keyword(s):  
Fracture Toughness ◽  
Polymer Nanocomposites ◽  
Direct Observation ◽  
Failure Mechanisms ◽  
Layered Silicate ◽  
Fracture Mechanisms ◽  
Three Point Bending ◽  
Silicate Nanocomposites

AbstractConventional three point bending and TEM techniques are employed to determine the fracture toughness and identify the failure mechanisms in model layered-silicate polymer nanocomposites.

Random Critical Fracture Toughness Values of China Railway Grade B Cast Steel Wheel

2011 ◽  
Vol 480-481 ◽  
pp. 381-386
Author(s):  
Lei Chen ◽  
Yong Xiang Zhao ◽  
Guo Xiang Song
Keyword(s):  
Fracture Toughness ◽  
Structural Damage ◽  
Cast Steel ◽  
Comparison Method ◽  
Growth Direction ◽  
Steel Wheel ◽  
Quantitative Measurements ◽  
Critical Fracture ◽  
Plastic Dissipation ◽  
Damage Process

Fracture surface observations and statistical deriving are applied for investigating the random critical fracture toughness values of China grade B cast steel wheel. Results reveal that: the crack grows to show fabric like stripes along the growth direction with few of dimples. Cleavage flowers appear under higher magnification. Cracked structural damage process is verified with few of plastic dissipation. At the same time, code based evaluated results indicate that significant scatter exists for the toughness values. Lognormal modeling is constructed appropriately with a comprehensive statistical comparison method. It is verified that random characters and quantitative measurements have been well depicted for the present critical fracture toughness values.

A review on experimental and numerical investigations of cortical bone fracture

2022 ◽  
pp. 095441192110703
Author(s):  
Ajay Kumar ◽  
Rajesh Ghosh
Keyword(s):  
Fracture Toughness ◽  
Cortical Bone ◽  
Bone Fracture ◽  
Bone Fractures ◽  
Complete Information ◽  
Fracture Pattern ◽  
Future Research ◽  
Fracture Mechanisms ◽  
Numerical Investigations ◽  
Fracture Parameters

This paper comprehensively reviews the various experimental and numerical techniques, which were considered to determine the fracture characteristics of the cortical bone. This study also provides some recommendations along with the critical review, which would be beneficial for future research of fracture analysis of cortical bone. Cortical bone fractures due to sports activities, climbing, running, and engagement in transport or industrial accidents. Individuals having different diseases are also at high risk of cortical bone fracture. It has been observed that osteon orientation influences cortical bone fracture toughness and fracture mechanisms. Apart from this, recent studies indicate that fracture parameters of cortical bone also depend on many factors such as age, sex, temperature, osteoporosis, orientation, location, loading condition, strain rate, and storage facility, etc. The cortical bone regains its fracture toughness due to various toughening mechanisms. Owing to these factors, several experimental, clinical, and numerical investigations have been carried out to determine the fracture parameters of the cortical bone. Cortical bone is the dense outer surface of the bone and contributes to 80%–82% of the skeleton mass. Cortical bone experiences load far exceeding body weight due to muscle contraction and the dynamics of motion. It is very important to know the fracture pattern, direction of fracture, location of the fracture, and toughening mechanism of cortical bone. A basic understanding of the different factors that affect the fracture parameters and fracture mechanisms of the cortical bone is necessary to prevent the failure and fracture of cortical bone. This review has summarized the advancement considered in the various experimental techniques and numerical methods to get complete information about the fracture mechanisms of cortical bone.

Impact of Metallic Foam’s Microstructure to its Mechanical Property

2013 ◽  
Vol 634-638 ◽  
pp. 2808-2812
Author(s):  
Zhu Feng Sun ◽  
Ling Yun Xie
Keyword(s):  
Fracture Toughness ◽  
Cell Structure ◽  
Crack Tip ◽  
Metallic Foam ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Metal Material ◽  
Loading Mode ◽  
Foam Metal ◽  
Material Fracture

Explored the influence of pore structure of foam metal material on mechanical behavior of fracture. Discuss fracture toughness of several different micro geometric structure of foam metal material with finite element method. The author's calculations showed, microstructure and loading mode has an important effect on the fracture toughness of the foam metal material. due to ignoring the effects of cell structure on the mechanical properties of materials, the classic fracture toughness criterion -crack tip opening displacement (COD) is incomplete, it would be more efficient to take opening displacement change rate of the crack-tip as the parameter to characteristic the metallic foam material fracture toughness.

Variations in Fracture Toughness for Alloy 718 Given a Modified Heat Treatment

1990 ◽  
Vol 112 (1) ◽  
pp. 116-123 ◽  
Author(s):  
W. J. Mills ◽  
L. D. Blackburn
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Fracture Mechanisms ◽  
Alloy 718 ◽  
Percent Confidence Level ◽  
Heat Treated ◽  
Curve Method ◽  
Heat Treated Condition ◽  
The Impact ◽  
Product Forms

Heat-to-heat and product-form variations in the JIC fracture toughness for Alloy 718 were characterized at 24, 427, and 538°C using the multiple-specimen JR-curve method. Six different material heats along with three product forms from one of the heats were tested in the modified heat treated condition. This heat treatment was developed at Idaho National Engineering Laboratory to improve the impact toughness for Alloy 718 weldments, but it has also been found to enhance the fracture resistance for the base metal. Statistical analysis of test results revealed four distinguishable JIC levels with mean toughness levels ranging from 87 to 190 kJ/m2 at 24°C. At 538°C, JIC values were 15 to 20 percent lower than room temperature toughness levels. Minimum expected values of JIC (ranging from 72 kJ/m2 at 24°C to 48 kJ/m2 at 538°C) and dJR/da (27 MPa at 24 to 538°C) were established based on tolerance intervals bracketing 90 percent of the lowest JIC and dJR/da populations at a 95 percent confidence level. Metallographic and fractographic examinations were performed to relate key microstructural features and operative fracture mechanisms to macroscopic properties.

scholarly journals Cracking and Toughening Mechanisms in Nanoscale Metallic Multilayer Films: A Brief Review

2018 ◽  
Vol 8 (10) ◽  
pp. 1821 ◽  
Author(s):  
Qing Zhou ◽  
Yue Ren ◽  
Yin Du ◽  
Dongpeng Hua ◽  
Weichao Han
Keyword(s):  
Fracture Toughness ◽  
High Strength ◽  
Plastic Instability ◽  
Multilayer Films ◽  
Fracture Mechanisms ◽  
Toughening Mechanisms ◽  
Individual Layer ◽  
Practical Applications ◽  
Mechanical Responses ◽  
The Individual

Nanoscale metallic multilayer films (NMMFs) have captured scientific interests on their mechanical responses. Compared with the properties of monolithic films, multilayers possess unique high strength as the individual layer thickness reduces to the nanoscale, which is benefited from the plentiful hetero-interfaces. However, NMMFs always exhibit a low fracture toughness and ductility, which seriously hinders their practical applications. While there have been reviews on the strengthening and deformation mechanisms of microlaminate, rapid developments in nanotechnology have brought an urgent requirement for an overview focused on the cracking and toughening mechanisms in nanoscale metallic multilayers. This article provides an extensive review on the structure, standard methodology and fracture mechanisms of NMMFs. A number of issues about the crack-related properties of NMMFs have been displayed, such as fracture toughness, wear resistance, adhesion energy, and plastic instability. Taken together, it is hoped that this review will achieve the following two purposes: (1) introducing the size-dependent cracking and toughness performance in NMMFs; and (2) offer a better understanding of the role interfaces displayed in toughening mechanisms. Finally, we list a few questions we concerned, which may shed light on further development.

X-ray Fractographic Study on Alumina and Zirconia Ceramics

1990 ◽  
Vol 34 ◽  
pp. 719-727 ◽  
Author(s):  
Sumio Tanaka ◽  
Yukio Hirose ◽  
Keisuke Tanaka
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Fracture Surface ◽  
High Strength Steels ◽  
High Strength ◽  
Fatigue Tests ◽  
Fracture Mechanisms ◽  
Zirconia Ceramics ◽  
X Ray ◽  
Fractographic Study

The residual stress left on the fracture surface is one of the important parameters in X-ray fractographic study. It has been used to analyze fracture mechanisms in fracture toughness and fatigue tests especially of high strength steels.In this paper, X-ray fractography was applied to brittle fracture of alumina (Al2O3) and zirconia (ZΓO2) ceramics.

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