The static compression test of metal rubber components was carried out by using the control variable method. Influences of technological parameters such as relative density and metal wire diameter as well as structural parameters such as height and bearing area on mechanical properties of metal rubber material were studied. Based on micro-element infinitesimal spring theory, one-dimensional (1D) constitutive model of metal rubber material bearing compressive load was established, and it was found by comparing with experimental data that the curve fitted well and the model was reliable, could accurately describe the mechanical behaviors of metal rubber component when bearing load. The model provides theoretical basis for further study of mechanical properties of metal rubber material. It also guides design and manufacture of metal rubber products as well as its engineering application.
Offshore pipelines and risers constructed from carbon steel have reduced levels of performance when operating in a sour environment. Fatigue crack growth rates can be significantly higher and material fracture toughness may be significantly lower. In this paper a fracture toughness test procedure for the pipeline girth weld in a sour environment is introduced. The single edge notched tensile (SENT) specimen, which has been widely accepted for the pipeline girth weld fracture toughness tests, was used in this proposed procedure. As expected it was found that the fracture toughness of the girth weld was reduced significantly after exposure to simulated sour service (NACE solution A), and this result is used for the assessment of the weld root defects that may work in the sour environment.
Fracture toughness testing in sour environment using Single Edge Notch Tensile (SENT) and Single Edge Notch Bend (SENB) specimens has been developed and applied by authors' laboratory for Engineering Critical Assessment (ECA) of pipeline girth welds. The method of testing and application of fracture toughness result for ECAs of pipeline girth welds for sour service has been presented at a previous OMEA conference (paper OMAE2009-79305 (1) ). The current paper presents the results of further experimental work carried out to evaluate the effect of strain rate on the fracture toughness value. A series of fracture toughness tests using SENT specimens was carried out in artificial brine sour environment (NACE solution "A" saturated with H 2 S) at ambient temperature. For comparison, the result from test in air condition are also presented and discussed. Following the test, the J-integral and the CTOD values were calculated and assessed. As expected, the results show significant effect of strain rate on the J integral value and the CTOD, especially for the strain rate range between 10 -6 /s to 10 -7 /s. Further experiments and studies are suggested to establish appropriate procedures and guidelines for selection of suitable strain rates for sour environment fracture toughness testing of pipeline girth welds.
It is of great significance to study the damage and fracture mechanism of trigonometrically symmetric eutectic multiphase ceramics with excellent mechanical properties at room temperature and high temperature. According to the microstructure characteristics of inner triangular symmetric eutectic in multiphase ceramics, a two-scale cell model containing triangular symmetric eutectic was established. The fracture stress of cohesive bond in eutectic was calculated by considering the conditions of cohesive bond fracture at interface phase and fiber junction. The damage variable was introduced and combined with cohesive bond fracture stress to establish the microcosmic damage fracture stress model of eutectic Based on the Dugdale Barenblatt model, the damage localization band model is established by introducing the micro damage fracture stress as the residual strength. It is found that with the increase of fiber volume fraction, the strong confinement of interface phase is destroyed, the residual strength decreases and the length of damage localization band increases with the increase of fiber volume fraction. Reducing the damage degree and selecting the appropriate fiber volume content can increase the fracture stress of eutectic, and then reduce the length of damage localization band, increase the threshold value of crack instability propagation, and enhance the material strength.
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