Papers by Keyword: Failure Patterns

Abstract: In this paper, a new type of specimen, which can be easily made by rock core through geological exploration, of mode II rock crack has been designed and processed. The crack propagation forces F of the specimen are measured under different temperatures and different confining pressures. The crack extension patterns are observed. The 3D finite element model of the specimen is established. The stresses near crack tip are calculated to get the value of K_IIC when the crack initiation. The variation of K_IIC of the model II rock crack is obtained under different temperatures and confining pressures. The experiments and numerical results show that temperature and confining pressure have obviously influence on K_IIC, the value of K_IIC decreases with the temperature increasing, and increases with the confining pressure increasing. The results of the paper can provide an important reference for analyzing the stability of the rock cracks in underground engineering.

Abstract: Refueling aircraft in-flight is a complex procedure at any time and has its concerns that have not fully been addressed, these are compounded if we consider remote piloting. Long term the need will exist to refuel unmanned vehicles if they are to carry out extensive applications; these complexities of in-flight refueling increases due to time delays and visual challenges between the actual remote aircraft and operators. This paper addresses the reliability of a drogue used in refueling and what can be learnt for future designs and usage. In particular what we can interpret from remote pilots and in-situ pilots.

Abstract: Based on the experimental data of reinforced concrete (RC) slabs subjected to concentrated loads, the influence of breadth span ratio on the failure characteristics and shear capacity is analyzed. It can be concluded that with the increment of breadth span ratio, the failure patterns of RC slabs will gradually convert from beam shear failure to punching shear failure and then punching failure. Furthermore, a formula derived from a range of experimental data for the shear capacity calculation of RC slabs is put forward. Then a comparison between the calculated values and test results is carried out which demonstrates a high degree of consistency. The suggested formula has fairly good practical value in engineering application and provides a beneficial reference to the concrete specification revision in the future.

Abstract: In order to studying the failure patterns under impact compression of Hybrid Fiber Reinforced Concrete(HFRC), tests focused on static and dynamic compression properties according to steel fiber reinforced concrete(SFRC) and HFRC are adopted. The equipment of dynamic compression properties test is Ф74mm split Hopkinson pressure bar (SHPB). The static and dynamic compressive strength at four different strain rates of the two materials are obtained, while failure mechanism has been analyzed from specimens’ failure modes in static and dynamic compressive tests, which in turn provides theory basis for the application of HFRC.

Abstract: The thickness or the type of insulating material of cavity wall can be changed in order to satisfy different requirement of thermal insulation properties, so it suits for the hot-summer and cold-winter zone. The static test of 16 pieces of cavity wall with different depth-thickness ratio and different eccentricity has been carried out in this paper, and the failure patterns of the cavity wall, the feature of out-of-plane deformation, the characteristic of vertical deformation and the impact of binding rebar have also been analyzed. As result shows that there is interaction between the interior piece and the external piece of wall under vertical loading which leads to the improvement of the compression capacity. With theoretical analysis, a formula of vertical compression capacity of cavity wall with insulation is proposed. The result calculated by the formula is coincided with the data obtained by the test.

Abstract: Brazilian test is a standardized test for measuring indirect tensile strength of rock and concrete disc (or cylinder). Similar test called indirect tensile test has also been used for other geomaterials. Although splitting of the disc into two halves is the expected failure mode, other rupture modes had also been observed. More importantly, the splitting tensile strength of rock can vary significantly with the specimen geometry and loading condition. In this study, a numerical code called RFPA2D (abbreviated from Rock Failure Process Analysis) is used to simulate the failure process of disc and ring specimens subject to Brazilian test. The failure patterns and splitting tensile strengths of specimens with different size and loading-strip-width are simulated and compared with existing experimental results. In addition, two distinct failure patterns observed in ring tests have been simulated using RFPA2D and thus this verifies the applicability of RFPA2D in simulating rock failure process under static loads.