scholarly journals Structural Characteristic Length in Metallic Glasses

2020 ◽  
Vol 36 (2) ◽  
pp. 255-264
Author(s):  
F. A. Akçay
Keyword(s):  
Fracture Toughness ◽  
Metallic Glasses ◽  
Characteristic Length ◽  
Experimental Results ◽  
Structure Property ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Material Parameters ◽  
Fracture Of Materials

ABSTRACTFracture of materials at the microscopic level involves a characteristic length related to microstructure. However, a clear structure-property relationship is still absent in metallic glasses. Therefore, a physics-based expression is derived for the characteristic length (relevant to brittle fracture) in metallic glasses (MGs) in order to link the microscopic material features controlling the fracture process to the macroscopic material parameters. The derived characteristic length is associated to micro/nano structural fracture patterns, critical crack tip opening displacement as well as fracture toughness. Characteristic lengths of various metallic glasses are determined using the proposed expression and compared to the experimental results. Theoretical results are in very good agreement with the experimental results of various metallic glasses. Furthermore, the contribution of characteristic length as well as macroscopic material parameters such as Poisson’s ratio, yield strength, and Young’s modulus on fracture toughness (and fracture energy) is investigated and compared to the experimental results.

Analysis on Critical CTOD of Long-Term Used Penstock

2017 ◽  
Vol 741 ◽  
pp. 57-62
Author(s):  
Fumito Kawamura ◽  
Masazumi Miura ◽  
Ryuichiro Ebara ◽  
Keiji Yanase
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Steel Structures ◽  
Chemical Compositions ◽  
Structural Components ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Crack Tip Opening

Many studies have been conducted to characterize the fracture toughness of structural steels and their welded joints. However, most studies focus on newly developed steels, and the number of studies on the fracture toughness of long-term used steels in structural components is rather limited. Furthermore, a lack of data on the fracture toughness causes difficulties in evaluating the structural integrity of existing steel structures. In this study, CTOD tests were performed to characterize the fracture toughness of penstock that has been in service for 50 years. By measuring the critical crack tip opening displacement in conjunction with analysis for chemical compositions, the characteristics of fracture toughness were investigated.

Fracture Toughness of PC and PC/ABS Alloy

2008 ◽  
Vol 33-37 ◽  
pp. 567-572
Author(s):  
Hui Min Li ◽  
Qin Zhi Fang ◽  
Tie Jun Wang
Keyword(s):  
Fracture Toughness ◽  
Essential Work ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Simple Method ◽  
Double Edge ◽  
Crack Tip Opening ◽  
Fracture Measurement ◽  
Work Of Fracture

As a direct and simple method, essential work of fracture has been widely used for fracture measurement of ductile polymers. In this paper, fracture toughness of PC and PC/ABS alloy is experimentally investigated. A series of double edge-notched tension (DENT) specimens and essential work method are employed to measure the fracture toughness of PC and PC/ABS alloy. By the way, the critical crack tip opening displacement is obtained. Moreover, the fracture surfaces of DENT specimens are examined by using a scanning electron microscope (SEM).

Experimental Study on the Cleavage Fracture Behavior of an ASTM A285 Grade C Pressure Vessel Steel

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Rafael G. Savioli ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Cleavage Fracture ◽  
Pressure Vessel ◽  
Fracture Behavior ◽  
Pressure Vessels ◽  
Experimental Results ◽  
Pressure Vessel Steel ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Vessel Steel

This work addresses an experimental investigation on the cleavage fracture behavior of an ASTM A285 Grade C pressure vessel steel. One purpose of this study is to enlarge previously reported work on mechanical and fracture properties for this class of steel to provide a more definite database for use in structural and defect analyses of pressurized components, including pressure vessels and storage tanks. Another purpose is to determine the reference temperature, T0, derived from the Master curve methodology which defines the dependence of fracture toughness with temperature for the tested material. Fracture toughness testing conducted on single edge bend SE(B) specimens in three-point loading extracted from an A285 Grade C pressure vessel steel plate provides the cleavage fracture resistance data in terms of the J-integral and crack tip opening displacement (CTOD) at cleavage instability, Jc and δc. Additional tensile and conventional Charpy tests produce further experimental data which serve to characterize the mechanical behavior of the tested pressure vessel steel. The experimental results reveal a strong effect of specimen geometry on Jc and δc-values associated with large scatter in the measured values of cleavage fracture toughness. Overall, the present investigation, when taken together with previous studies, provides a fairly extensive body of experimental results which describe in detail the fracture behavior of an ASTM A285 Grade C pressure vessel steel.

Novel Specimen Design for Measurement of In-Plane Fracture Toughness of Metals

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Abderrazak Traidia ◽  
Elias Chatzidouros ◽  
Mustapha Jouiad ◽  
Kaamil-Ur-Rahman Shibly
Keyword(s):  
Fracture Toughness ◽  
Pipeline Steel ◽  
Compact Tension ◽  
Experimental Results ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Steel Grades ◽  
Plane Direction ◽  
Crack Tip Opening

Abstract Standard-compliant measurement of the in-plane fracture toughness of metals is often challenging due to insufficient material in the through-thickness direction to extract a full single edge bending (SEB) or compact tension (CT) fracture specimen. In the present work, we propose a new specimen design methodology to overcome this challenge. A W-shaped SEB specimen (called W-SEB) was developed, and its topology was optimized using finite element simulations. The new specimen design was validated numerically and experimentally on a case study showing excellent agreement with standard ASTM E1820 actual SEB specimen geometry. In view assessing the anisotropy of the fracture toughness (KQ and crack tip opening displacement (CTOD)) of pipeline steels susceptible to hydrogen-induced cracking (HIC), the W-SEB specimen was tested on X65 and X42 pipeline steel samples taken from the field. Experimental results show an increase in the maximum CTOD along the in-plane direction as compared to the transverse direction for both steel grades. Such experimental results could lead to important considerations with respect to accurate fitness for service assessment of HIC-damaged assets.

scholarly journals Brittleness of Concrete under Different Curing Conditions

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7865
Author(s):  
Shuai Zhang ◽  
Bing Han ◽  
Huibing Xie ◽  
Mingzhe An ◽  
Shengxu Lyu
Keyword(s):  
Fracture Toughness ◽  
Concrete Beams ◽  
Strain Energy Release ◽  
Crack Tip Opening Displacement ◽  
Steam Curing ◽  
Opening Displacement ◽  
Critical Crack ◽  
Curing Conditions ◽  
Curing Condition

In order to shorten construction periods, concrete is often cured using steam and is loaded at an early age. This changes the performance and even the durability of the concrete compared to concrete that has been cured under normal conditions. Thus, the pattern and the mechanism of concrete performance change under different curing conditions, and loading ages are of great significance. The development of brittleness under different curing conditions and loading ages was studied. The evaluation methods that were used to determine concrete brittleness were expounded. Steam, standard, and natural curing conditions were carried out on single-side notched concrete beams as well as on a concrete prism and cubic blocks. The compressive strength and splitting tensile strength of the concrete blocks along with the fracture performance of the concrete beams were tested after 3, 7, 28, and 90 days. The steam curing condition significantly improved the strength of concrete before 28 days had passed, and the standard curing condition improved the strength of concrete after 28 days. Based on the experimental fracture parameters, a two-parameter fracture model was applied to study the development of fracture toughness KICS, critical crack tip opening displacement CTODc, and critical strain energy release rate GICS with hydration age under different curing conditions. With respect to long-term performance, the standard curing condition was better at resisting concrete crack propagations than the steam curing condition was. The characteristic length lch and the material length Q under the three curing conditions and the long-term development of brittleness in the concrete indicated that steam curing increased the concrete brittleness. Considering the effects of the curing condition and the loading age, a time-dependent concrete fracture toughness model was established, and the predicted value of the model was verified against the measured value. The results indicated that the model was able to accurately predict the fracture toughness with an error rate of less than 16%.

scholarly journals Analysis influence of Dmax on fracture mechanics parameters of concrete made of limestone aggregate at three point bending.

2007 ◽  
Vol 1 (1) ◽  
pp. 005-016
Author(s):  
Grzegorz Golewski
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Fracture Mechanics ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Initial Crack ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Load Displacement

The analysis of concrete behaviour taking into account fracture mechanics method makes it possible to describe the origin and development of the damages occurring in it, which is impossible in case of using global strength characteristics of composite. In the work the experiment results were presented regarding the determination of the influence of grain-size distribution of coarse aggregate on the crack mechanics parameters of limestone concretes as defined according to the I mode of crack propagation at bending. Two types of optimal composition of grains were used with Dmax up to 8 and up to 16 mm. During the experiments the basic parameters of fracture mechanics were determined: critical value of stress intensity factors: : and KIc, fracture energy GF, critical crack tip opening displacement CTODc and unit work of failure JIc. During the fracture toughness tests the method of loading samples based on RILEM recommendations was used. For basic experiments six beams with one initial crack were used. In the course of the experiments carried out, two dependencies were recorded for each sample: load – displacement of crack outlet opening and load - displacement of the point of applied force. In the course of the tests carried out it was found out that the higher fracture toughness was characteristic of concretes with the grain - size distribution up to 16 mm. The results presented in the work can be used in designing concretes in order to obtain materials characterized by the minimum number of initial defects which, thanks to increased fracture toughness, can increase to the reliability of construction work.

Applying Gurson Type of Damage Models to Low Constraint Tests of High Strength Steels and Welds

2006 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang
Keyword(s):  
Damage Mechanics ◽  
Ductile Failure ◽  
High Strength Steels ◽  
High Strength ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Gtn Model ◽  
Strain Capacity ◽  
Low Constraint

Pipelines experiencing displacement-controlled loading need to have adequate strain capacity. Large tensile strain capacity can only be achieved when the failure processes are ductile. In ductile failure analyses, the strain capacity may be determined by two approaches. The first approach uses the conventional fracture mechanics criteria, such as the attainment of the critical crack tip opening displacement, to assess the onset of the crack propagation. The other approach uses damage mechanics models in which the onset and propagation of cracks are controlled by the nucleation, growth, and coalescence of voids in the material. The damage mechanics models can provide some insights of the ductile failure processes as they have more physical mechanisms built in the constitutive model. In this paper, the Gurson-Tvergaard-Needleman (GTN) model is applied to two types of low-constraint tests: curved wide plates and back-bend specimens. The wide plate test is considered more representatives of full-scale pipes than the conventional laboratory-sized specimens, but requires large-capacity machines. The back-bend test is a newly developed low-constraint laboratory-sized test specimen. A relatively simple approach to determine the damage parameters of the GTN model is discussed and the transferability of damage parameters between those two test types is also analyzed.

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