Experimental Study on Coupling Influence of Temperature and Confining Pressure to Deformation and Strength Characteristics of Rock-like Material with Pre-Existing Crack

In this paper, destructive compression tests under the coupled influence of temperatures (20–60 °C) and confining pressures (0–7 MPa) were carried out on rock-like material with pre-existing crack to explore the deformation and strength characteristics. The stress–strain curves of rock-like material under the coupled influence of temperatures and confining pressures were obtained. Meanwhile, the correlations of peak stress, peak strain, and average Young’s modulus with temperatures and confining pressures were obtained. The results of the experiments indicate that, firstly, the compressive strength decreased and the deformation increased due to the influence of pre-existing cracks; the combined effect of initial cracks, temperature, and confining pressure gave rise to a more complicated mechanism of soft rock deformation. Secondly, the deformation of rock-like material was affected by initial cracks, confining pressures, and temperatures, but the influence of temperature was lower than that of confining pressure and initial crack. The failure mode of rock-like material was brittle at the confining pressure of 0 and 1 MPa and plastic at the confining pressure of 5 and 7 MPa. The critical confining pressure value of failure mode for rock-like material was 3 MPa. Thirdly, the peak strength and peak strain of rock-like material increased with confining pressure. Temperature had less influence on the rock-like material strength and peak strain than confining pressure. Lastly, Young’s modulus decreased with temperature and confining pressure.

Analisis Kegagalan Pada Komponen Poros Pompa Industri

Pumps are very important industrial equipment in the petroleum industry. The component that often fails is the pump shaft. Therefore, it is necessary to conduct a failure analysis of this component to determine the mode/type of failure and how it occurred. This study used Scanning Electron Microscope (SEM), metallographic test, chemical composition test, and Brinell hardness test with the standard UNSS42000 material. Fatigue test to determine the fatigue limit of the shaft with a rotary bending fatigue test. The failure model that occurred was fatigue failure characterized by initial cracks, crack growth, ratchet marks, sudden fracture areas. Based on the comparison between the test results of chemical composition and mechanical properties of the material, the drive shaft pump material was suitable for the UNS S42000 material.

Fatigue response of aircraft wing root joints under limit cycle oscillations

When wing root attachments are subject to cyclic loading during a flight, slipbands are produced by fatique. The density of these slipbands increases with the advancing of the fatigue process and initial cracks appear within the persistent slipbands. This project investigates the fatigue response of a titanium alloy wing root joint under different loading spectra during limit-cycle oscillations by the strain-life approach. Although wing root attachments are designed such that the nominal loads remain elastic, stress concentrations often cause plastic strains to develop in the vincinity of notches. Subsequently, wing loads caused by limit-cycle oscillations lead to fatique damage accumulation. This project's results lead to the conclusion that cyclic loading during limit-cycle oscillations can cause fatigue damage in wing root joints. Tensile mean stress is detrimental to the fatique life of wing root joints, while compressive mean stress is beneficial.

Fatigue response of aircraft wing root joints under limit cycle oscillations

When wing root attachments are subject to cyclic loading during a flight, slipbands are produced by fatique. The density of these slipbands increases with the advancing of the fatigue process and initial cracks appear within the persistent slipbands. This project investigates the fatigue response of a titanium alloy wing root joint under different loading spectra during limit-cycle oscillations by the strain-life approach. Although wing root attachments are designed such that the nominal loads remain elastic, stress concentrations often cause plastic strains to develop in the vincinity of notches. Subsequently, wing loads caused by limit-cycle oscillations lead to fatique damage accumulation. This project's results lead to the conclusion that cyclic loading during limit-cycle oscillations can cause fatigue damage in wing root joints. Tensile mean stress is detrimental to the fatique life of wing root joints, while compressive mean stress is beneficial.

Numerical Simulation of the Effect of Loading Angle on Initial Cracks Position Point: Application to the Brazilian Test

The Brazilian Test is the most used test to determine the indirect tensile strength for brittle materials like concrete. It has been observed that the success of the test depends on the cracks initiation point position and therefore the arch loading angle; a crack appears in the center of the disk when the test is valid. To this effect, using Fast Lagrangian of Continua code FLAC2D; numerical analyses were performed to study the impact of the arch loading angle on the initial crack’s position in a 70 mm diameter Brazilian disk of concrete and mortar under loading arch 2α which varies from 5–45°. The distribution of stresses and the tensile strength at the center of the Brazilian disk obtained numerically was closely similar to analytical and experimental existing solutions. The results showed that to obtain a meaningful and validated test with the most accurate indirect tensile strength, it is recommended to take a loading arch 2α ≥ 20° for the concrete and 2α ≥ 10° for the mortar.

Cyclic Behavior and Modeling of Bolted Glulam Joint with Cracks Loaded Parallel to Grain

Under varying humidity and temperature conditions, with the constraint of metal fasteners to wood shrinkage, cracks along the bolt lines are generally observed in bolted glulam joints. A three-dimensional (3D) numerical model was established in software package ANSYS to investigate the cyclic behavior of bolted glulam joints with local cracks. A reversed cyclic loading was applied in the parallel-to-grain direction. The accuracy of numerical simulation was proved by comparison with full-scale experimental results. Typical failure modes were reproduced in the numerical analysis with the application of wood foundation zone material model and cohesive zone material model. The effect of crack number and length on the hysteretic behavior of bolted glulam joints was quantified by a parametric study. It was found that initial cracks impair the peak capacity and elastic stiffness of bolted glulam joints significantly. More decrease in capacity was observed in joints with more cracks, and longer cracks affect elastic stiffness more dramatically. Moreover, with the existence of initial cracks, the energy dissipated and equivalent viscous damping ratio of bolted joints are reduced by 24% and 13.3%, respectively.

DAMMING HUNZA RIVER BY MASSIVE ATTABAD LANDSLIDE, STORY OF A RISK MANAGEMENT INITIATIVE FROM HUNZA, PAKISTAN

The mountainous region of northern Pakistan is seismically active as Indian plate is subducting beneath the Eurasian plate. Various geological phenomena are active due to the mountain building and landslides are one of the most destructive natural disasters in the Karakoram range. The northern part of Pakistan, Gilgit-Baltistan, falling in this region is no exception to that. Attabad was a remote village situated on the right bank of Hunza River at a ground distance of almost 125 km from Gilgit city. The area falls into Darkut-Karakoram metamorphic complex composed of granites, granodiorite, and gneiss. A devastating landslide occurred on 4th January 2010, as mode of circular failure which blocked the Hunza River forming a lake behind. The debris material hit the opposite rock cliff, due to narrow gorge the landslide mass travelled downstream 1.5km with huge debris surges, hitting 8 houses in lower Attabad which came under rubble and 19 people died. Aga Khan Agency for Habitat previously FOCUS Pakistan developed an inventory of active landslides across the KKH in Hunza in 2000-2001, however this landslide was not identified. Later in 2002 after the Astore earthquake initial cracks developed at the top of the slope. The 8th October Kashmir earthquake destabilized and U-shaped demarcation appeared across the slope. Anthropogenic activities like irrigation of lands, seepage of water from rain and snow melt water further destabilized the land. Finally, an earthquake in November 2009 in Hindukush region triggered the landslide and brittle failure occurred on 4th January 2010.

Fatigue Life Prediction of the Zirconia Fixture Based on Boundary Element Method

Zirconia grinding fixtures have been widely used in semiconductor industry to improve the quality and precision of the products. For maximizing the service life and minimizing the risks of accidental damage, it is critical to have a better understanding of the fatigue life of zirconia grinding fixtures. To this end, a boundary element method is developed in this paper to investigate their crack growth and fatigue life. To validate the proposed method, the stress intensity factor of a typical plate structure with initial cracks is considered. On this basis, Paris Law is employed in the boundary element model to further study the crack growth and stress distributions in the zirconia fixture under cyclic loads. Numerical results show that stress concentration occurs at the pillar of the fixture, and crack growth is perpendicular to the loading direction.