An experimental investigation on the tensile stiffness in layered rock interface using the digital image correlation techniqueDong, Xiong; Huanqiang, Yang; Yang, Liu; Xiaowei, Wang
2020 Strength Fracture and Complexity
doi: 10.3233/sfc-200251
Tensile stiffness of interfacial layered rock is the basis of studying the law of interlaminar propagation of hydraulic cracks. We used similar materials to make simulated specimens of sand-mud layered rock with prefabricated cracks, and used the digital image correlation (DIC) technique together with the three-point bending (TPB) test to obtain the strain field near the prefabricated crack tip in tensile state. Combined with the tensile stress in the corresponding area calculated by the load of the tester, the tensile stress-displacement curve at the interface of layered rock is obtained, and the tensile stiffness and interfacial fracture law at the interface of layered rock is calculated by the curve. The results show that in the process of tensile failure, before reaching its peak value, the interfacial tension stress of layered rock has a linear elastic deformation stage followed by a short hardening stage. Upon reaching the peak value, it is accompanied by interfacial failure and macro-cracks, and then the load decreases and enters the softening stage, which results in the complete destruction of the interface. The tensile stiffness values of layered rock with different sizes vary greatly, which indicates that the interfacial tensile stiffness values are sensitive to the specimen size and have a size effect. The results are of great significance to the study of the law of hydraulic fracture propagation in the interface of layered rock.
An experimental investigation on the tensile stiffness in layered rock interface using the digital image correlation techniqueDong, Xiong; Huanqiang, Yang; Yang, Liu; Xiaowei, Wang
2020 Strength, Fracture and Complexity
doi: 10.3233/SFC-200251
Tensile stiffness of interfacial layered rock is the basis of studying the law of interlaminar propagation of hydraulic cracks. We used similar materials to make simulated specimens of sand-mud layered rock with prefabricated cracks, and used the digital image correlation (DIC) technique together with the three-point bending (TPB) test to obtain the strain field near the prefabricated crack tip in tensile state. Combined with the tensile stress in the corresponding area calculated by the load of the tester, the tensile stress-displacement curve at the interface of layered rock is obtained, and the tensile stiffness and interfacial fracture law at the interface of layered rock is calculated by the curve. The results show that in the process of tensile failure, before reaching its peak value, the interfacial tension stress of layered rock has a linear elastic deformation stage followed by a short hardening stage. Upon reaching the peak value, it is accompanied by interfacial failure and macro-cracks, and then the load decreases and enters the softening stage, which results in the complete destruction of the interface. The tensile stiffness values of layered rock with different sizes vary greatly, which indicates that the interfacial tensile stiffness values are sensitive to the specimen size and have a size effect. The results are of great significance to the study of the law of hydraulic fracture propagation in the interface of layered rock.
Fatigue strength of friction-welded joints of aluminum bronze to stainless steelOchi, Hiizu; Isshiki, Yoshihiro; Kawai, Gosaku
2020 Strength Fracture and Complexity
doi: 10.3233/sfc-204000
Friction welding of C6191 aluminum bronze to SUS304L stainless steel was carried out to examine its weldability. Joint strength was evaluated by fatigue strength. The C6191 and the SUS304L at the weld interface were hardened, while the heat affected zone of the SUS304L was slightly softened. A reaction layer of 1–5 μm that consisted of component elements of the base metals was observed at the weld interface. The fatigue limit of the joint welded under the optimum welding condition was higher than those of the base metals because of the hardening of C6191 and SUS304L, and the fatigue limit of joints decreased as the friction time or the upset pressure varied. In particular, the fatigue strength of joints welded under the conditions varied the upset pressure which was lower than that of the C6191 base metal.
Fatigue strength of friction-welded joints of aluminum bronze to stainless steelOchi, Hiizu; Isshiki, Yoshihiro; Kawai, Gosaku
2020 Strength, Fracture and Complexity
doi: 10.3233/SFC-204000
Friction welding of C6191 aluminum bronze to SUS304L stainless steel was carried out to examine its weldability. Joint strength was evaluated by fatigue strength. The C6191 and the SUS304L at the weld interface were hardened, while the heat affected zone of the SUS304L was slightly softened. A reaction layer of 1–5 μm that consisted of component elements of the base metals was observed at the weld interface. The fatigue limit of the joint welded under the optimum welding condition was higher than those of the base metals because of the hardening of C6191 and SUS304L, and the fatigue limit of joints decreased as the friction time or the upset pressure varied. In particular, the fatigue strength of joints welded under the conditions varied the upset pressure which was lower than that of the C6191 base metal.
Fractal scaling and specimen-size effects on creep resistanceCarpinteri, Alberto; Niccolini, Gianni; Rubino, Alessio
2020 Strength, Fracture and Complexity
doi: 10.3233/SFC-200259
Scaling effects governing the creep behaviour of unnotched and uncracked metallic specimens are investigated by applying similarity considerations and fractal modelling to experimental results provided in the literature. The focus is on stress rupture tests conducted at elevated temperatures on Cr-Mo-V steel cylindrical bars of different sizes. The observed specimen-size effects on the 𝜎 versus tR creep resistance diagrams are interpreted in terms of incomplete self-similarity and fractal weakening (lacunarity) of the specimen reacting cross-section. That leads to a scale-invariant (fractal) formulation of the creep rupture law in terms of renormalized stress.
Fractal scaling and specimen-size effects on creep resistanceCarpinteri, Alberto; Niccolini, Gianni; Rubino, Alessio
2020 Strength Fracture and Complexity
doi: 10.3233/sfc-200259
Scaling effects governing the creep behaviour of unnotched and uncracked metallic specimens are investigated by applying similarity considerations and fractal modelling to experimental results provided in the literature. The focus is on stress rupture tests conducted at elevated temperatures on Cr-Mo-V steel cylindrical bars of different sizes. The observed specimen-size effects on the 𝜎 versus tR creep resistance diagrams are interpreted in terms of incomplete self-similarity and fractal weakening (lacunarity) of the specimen reacting cross-section. That leads to a scale-invariant (fractal) formulation of the creep rupture law in terms of renormalized stress.