Extension of grouting-induced splitting fractures in materials similar to coal rocks containing prefabricated fractures

To reveal the influence of prefabricated fractures (PFs) with different parameters on the extension of grouting-induced splitting fractures, a combination of numerical simulation and physical experiments were used to carry out grouting trials on similar materials to coal rock. The RFPA software was used to simulate the whole process of fracture initiation and expansion of coal rock with PFs during grouting. In the experiment, acoustic emission (AE) technology was used to monitor the extension process of grouting-induced splitting fractures. The results demonstrated that when the PFs do not intersect with the grouting holes, the extension of grouting-induced splitting fractures in rocks containing PFs experienced four stages: splitting and penetrating, slurry filling, fracture splitting and splitting extension. PFs have an orienting effect on the direction of grouting fracture extension and the size of the PFs influenced the extension of the grouting-induced splitting fractures: the larger the size, the easier the surrounding rocks were ruptured, the easier the connection was formed of channels between the grouting-induced splitting fractures and the PFs were formed, and the more complex the secondary splitting pattern in the PFs. This indicated that the angle of PFs played a decisive role in determining the extension direction of grouting-induced splitting fractures. The extension of grouting-induced splitting fractures during grouting of rock mass with different parameters is revealed by numerical simulation and experimental results.

Setting of Natural Fracture Splitting Surface on Connecting Rod and Its Formation Mechanism

To break through the limitation of fracture splitting process on material selection and solve problems during fracture splitting such as parts tearing, failing to split, dropping dregs, fracture surface deformation and so on, a new technique of setting natural splitting surface in casting blank is proposed, aiming to achieve brittle fracture along pre-set surface during fracture splitting process. In this research, casting blanks are produced with metal molds. A layer of AZ31 foil is set in advance before casting, the layer interacts with liquid LD10 aluminum alloy, forming a brittle interface layer across the whole casting, then a fracture splitting hole is machined in the middle of the casting blank and cracking grooves are machined on the inner hole near the interface to achieve fracture splitting. Experiment revealed that the initial crack on the specimen starts from the root of the cracking groove, and the crack basically expands along the pre-set fracture splitting surface. The fracture surface is characterized by flaky brittle fracture. There is residual magnesium and pellumina, which have characteristics of melt with low-melting point, and micro-porosity in the fracture. Further analysis suggests that the formation mechanism of a natural fracture splitting surface can be described as follows: the magnesium foil with strong oxidation in high-temperature alloy liquid interacts with the pellumina at the front of liquid flow, which forms a interface. Meanwhile a layer of melt with a low-melting point forming as a result of interface reaction is pushed to the edge of the grain boundary, and surface liquid film shrinks to be micro-porosity. With such a combined effect it finally forms the brittle surface, which provides the condition for conducting subsequent fracture splitting process.

Properties and fracture splitting of cast steel matrix composites

To break through current limitations of fracture splitting materials for connecting rods, a bimetallic compound as a fracture splitting material was studied. The bimetallic sample was produced by investment casting, and interface performance tests and splitting tests were conducted. At a casting temperature of 1600 °C for 0.25 wt. % C cast carbon steel, the preheating temperature of T10A was 500 °C, and the thickness of T10A was in the range of 2–3 mm. The 0.25 wt. % C cast carbon steel and T10A were fully combined in the interface. The appearance of the fracture zone was a flat cleavage fracture, which would facilitate meshing of the cracked surface if the specimen were assembled and improve the quality of fracture splitting.

Effect of Different Microstructures on the Performance of Air-Cooled Forging Steel 46MnVS5 Fracture Splitting Connecting Rod

This paper analyzed mechanical properties and splitting fracture performance of 46MnVS5 with different microstructures. It will provide support of date for new type of splitting fracture connecting rod materials. The results show that bainite has good strength and ductility, but its high ductility is bad for splitting fracture. Martensite and tempered martensite have high strength and low ductility, which is bad for using performance. Ductility of tempered sorbite is too high to meet splitting fracture performance. Tensile and yield strength, impact toughness of tempered troostite is 1569MPa, 1407MPa and 17.5J/cm2, respectively. Tempered troostite has high strength and good splitting fracture performance. Bainite+martensite and tempered troostite maybe two good choices for better splitting fracture and using performance.