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).

Accuracy of the Double-Clip on Gauge Method for Evaluating CTOD of SE(T) Specimens

2014 ◽  
Author(s):  
Zijian Yan ◽  
Yifan Huang ◽  
Wenxing Zhou
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Specimen Thickness ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Integrity Assessment ◽  
Crack Tip Opening ◽  
Edge Tension

The crack tip opening displacement (CTOD)-based fracture toughness has been widely used for structural integrity assessment and strain-based design of oil and gas pipelines. The double-clip on gauge method has been used to experimentally determine CTOD. In this study, three-dimensional (3D) finite element analyses of clamped single-edge tension (SE(T)) specimens are carried out to investigate the accuracy of the CTOD evaluation equation associated with the double-clip on gauge method. The analysis considers SE(T) specimens with ranges of crack lengths (0.3 ≤ a/W ≤ 0.7) and specimen thickness (B/W = 0.5, 1 and 2). Based on the analysis results, a modified CTOD evaluation equation based on the double-clip on gauge method is developed to improve the accuracy of the CTOD evaluation. This study will facilitate the application of the fracture toughness determined from the SE(T) specimen in the strain-based design of pipelines.

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%.

Test for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

2010 ◽  
Vol 36 ◽  
pp. 157-161 ◽  
Author(s):  
Tin Gyi Zhang ◽  
Yuan Bao Leng ◽  
Dan Ying Gao
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Critical Crack Opening ◽  
Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

Experimental Study on CTOD Fracture Toughness of Welded Joints of Low Temperature Steel

2011 ◽  
Vol 328-330 ◽  
pp. 1272-1276 ◽  
Author(s):  
Zong Tao Fang ◽  
Bo Sun ◽  
Chun Run Li
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Welded Joints ◽  
Welding Process ◽  
Offshore Platform ◽  
Fracture Toughness Test ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Welding Procedure ◽  
Crack Tip Opening

According to BS7448 fracture toughness test standard, crack tip opening displacement (CTOD) for ASTM A333 Gr.6 low temperature steel which is used in offshore platform were carried out in low temperature (0°C, -29°C). Three point bending tests were conducted on the specimens, the dimension of which is B×2B (B is the thickness) and notch direction is NP. The final value of CTOD was calculated by P-V curves of both the welds and HAZ (heat affected zone). And the experimental results were analyzed and discussed in the paper. The low temperature steel welded joints show good low temperature toughness, the selected welding procedure is applied to construction of pipelines.The CTOD value of HAZ is larger than weld metal and weld is the weakest position in the whole structure. The experiment results provide an important basis for the choice of welding method and welding process parameters, ECA assessment and construction of offshore platform.

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