High-strain fatigue characteristics and fracture toughness of welded joints in components of water turbines

1990 ◽  
Vol 4 (2) ◽  
pp. 153-156
Author(s):  
V Gregor ◽  
P Polak
Keyword(s):  
Fracture Toughness ◽  
Welded Joints ◽  
High Strain ◽  
Fatigue Characteristics ◽  
Water Turbines

Interlaminar Fracture in Carbon Fiber/Thermoplastic Composites

1989 ◽  
Vol 170 ◽  
Author(s):  
J. A. Hinkley ◽  
W. D. Bascom ◽  
R. E. Allred
Keyword(s):  
Fracture Toughness ◽  
Carbon Fiber ◽  
Carbon Fibers ◽  
High Strain ◽  
Thermoplastic Composites ◽  
Plasma Modification ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture ◽  
Polyphenylene Oxide ◽  
Commercial Carbon

AbstractThe surfaces of commercial carbon fibers are generally chemically cleaned or oxidized and then coated with an oligomeric sizing to optimize their adhesion to epoxy matrix resins. Evidence from fractography, from embedded fiber testing and from fracture energies suggests that these standard treatments are relatively ineffective for thermoplastic matrices. This evidence is reviewed and model thermoplastic composites (polyphenylene oxide/high strain carbon fibers) are used to demonstrate how differences in adhesion can lead to a two-fold change in interlaminar fracture toughness.The potential for improved adhesion via plasma modification of fiber surfaces is discussed. Finally, a surprising case of fiber-catalyzed resin degradation is described.

scholarly journals Evaluation of crack resistance of welded joints with soft interlayers

2022 ◽  
Vol 21 (4) ◽  
pp. 308-311
Author(s):  
K. A. Molokov ◽  
V. V. Novikov
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Crack Resistance ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Transverse Load ◽  
Structural Elements ◽  
Metal Structures ◽  
Characteristic Appearance ◽  
Reliability Indicator

Introduction. Welded joints in large-sized metal structures (e.g., in the structures of ship hulls) subject to low-cycle fatigue are considered. The characteristic appearance of soft interlayers, which are significantly plastically deformed under working loads, was noted. Deformation of the metal structure with damage, especially in the form of cracks, reduces the strength and reliability of structural elements and joints. Pre-deformation negatively affects plasticity; therefore, much depends on the residual plasticity of the cracking material. At the same time, with a decrease in residual plasticity, such an important reliability indicator as the resistance of the material to crack propagation — the fracture toughness – decreases. The paper is devoted to the development of a model that includes analytical dependences for assessing the crack resistance of metal structures and their welded joints with soft interlayers according to the crack resistance limit for all crack sizes.Materials and Methods. The theory and methods of linear mechanics of materials destruction, structural-mechanical approach are used. The calculation results were analyzed and compared to the experimental data and other analytical solutions. The numerical experiment was performed for the ferrite-perlite steel grades of 10, 50, 22K, St3sp, etc., widely used in industry, as well as for alloy steels hardened to medium and high strength of 30KhGSA, 37KhN3A, etc. Results. Analytical dependences are obtained for calculating the relative crack resistance limit according to three main known mechanical characteristics of the state of the material of the soft interlayer of the welded joint.Discussion and Conclusions. The results obtained can be used to assess the crack resistance of pre-deformed structural elements and welded joints (including those with soft interlayers) operating under a transverse load. The results of experimental data and analytical calculations are shown in dimensionless form, which enables to obtain invariant results with respect to the fracture toughness limit.

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.

Sign in / Sign up

Export Citation Format

Share Document