Effect of Acidizing Process on the Stress Corrosion Cracking of HP-13Cr Stainless Steel in the Ultra-depth Well Environment

The effect of acidizing process on the stress corrosion cracking of HP-13Cr stainless steel in the ultra-depth well environment was studied by the slow strain rate test, the electrochemical measurement, the microstructure observation, and the finite element modeling. The results indicated that the acidizing process significantly increased the stress corrosion cracking susceptibility of HP-13Cr stainless steel and induced the fracture mode to the brittle characteristic in the high temperature and CO2 pressure environment. The stress corrosion cracking susceptibility also increased with the increase of temperature and CO2 pressure. There were dense defects including pits and cracks in the fracture section from the transverse view. After the acidizing process, under tensile stress condition, the increasing roughness will cause the stress concentration and promote the local anodic dissolution, which induces the initiation of stress corrosion cracking.

On predicting the deformation and fracture properties of ABS / PMMA / Nano-SiO2 composites

The damage mechanism of ABS/PMMA/nano-SiO2 composites was studied by both experiments and finite element analysis in this paper. A microstructure-based the Homogenization theory and the surface-based cohesive method was developed to predict the deformation and fracture behavior of ABS/PMMA/nano-SiO2 composite. The constitutive behavior of the elastoplastic-damage in the matrix, the fracture for the nano-SiO2 reinforement, and the traction-separation for interfaces, were simulated in this model. The validity of the modeling results were validated by the agreement of the experiment and the morphology of fracture section with those predicted by the simulation. The numerical results were used to provide insight into the damage mechamisms of ABS/PMMA/nano-SiO2 composites, and the effects of nano-SiO2 strength on ABS/PMMA blends mechanical properties were also discussed in detail.

Fatigue Behavior Parametric Analysis of Dry Machined UNS A97075 Aluminum Alloy

Fatigue behavior takes special relevance in structural parts for aircraft due to safety reasons. Despite its environmental advantages, dry machining of these parts may negatively affect their surface integrity, which may lead to a reduction in fatigue life. Nevertheless, there is a lack of research focused on the analysis of the cutting parameters influence on fatigue behavior in dry machining of aeronautical aluminum alloys, in spite of its importance. Therefore, in this work, an analysis of the cutting speed and feed influence on fatigue behavior of dry turned UNS A97075-T6 alloy is presented. The stress-fatigue life curves have been obtained and corrected according to the applied cutting parameters values. Additionally, the surface roughness and two macro-geometrical deviations (cylindricity and concentricity) have been controlled. The experimental results have revealed that fatigue life is reduced when high values of cutting speed and feed are combined. Finally, a parametric potential equation for fatigue life, as a function of the load and the cutting parameters, has been developed. The relation has been obtained for the theoretical fracture section and, as the main novelty, corrected for the real one.

Fracture failure analysis of the pump shaft

The failure reasons of the circulating pump shaft in the upper section of the quench tower were analyzed by means of chemical composition analysis, macroscopic observation, metallographic examination and fracture section analysis. The analysis result shows that the calcium-silicate inclusions in the surface of the pump shaft cause the microcracks and the parallel fatigue sources, which leads to the fatigue cracks propagation under alternating load and finally the shaft is fatigue fractured.

Acoustic Emission Location Experiment Research on Stope Roof Breakage Boundaries Time-Varying Process

This paper utilizes self-designed time-varying boundary sound emission test system for rock stratum fracture to complete the sound emission orientation test upon the fracture of marble slab. A new method—image diagnosis and orientation method is proposed to locate fracture section. Sound emission signal Y Position and Events-X position distribution point diagram is utilized to determine the position of fracture surface; by analyzing the time-varying curve of Counts, Energy and Hits of acoustic emission signal in the same stage, the occurrence moment of rock stratum fracture section is confirmed and the development mechanism of fracture section is analyzed. Through study, it can be concluded that located fracture section position is close to actual fracture position, indicating that sound emission image diagnosis technique is characterized by high orientation precision, small error and good orientation effect; sound emission image diagnosis orientation method has very excellent maneuverability and practicability.

Fracture Analysis of a Crankshaft Used for Heavy-Duty Truck

A failure investigation for a diesel engine crankshaft has been conducted which was used for truck in this paper, which is made from 42CrMo steel. The fracture occurred on the crank web between the 4th crankpin and the 4th journal, the fracture section indicates that fatigue is the dominant mechanism. The dimensions, chemical compositions of material and surface hardness were evaluated in order to find the failure causes. Chemical compositions, the depth of hardness layer and surface hardness are qualified; however, there are transition zone of hardness layer on the journal boss fillet, the dimensions of journal boss is not qualified, it less than specified dimension, and many non-metallic inclusions aggregate zones and heavy segregation were found from metallographic photo, these would reduce the tensile strength. FEA analysis is also used to analysis the strength of this crankshaft, and the results suggest that the dimension of journal boss fillet is the key dimension, which has an important effect on the strength of the crankshaft. So the disqualified machining dimensions, material property are the main reasons for the fraction of this crankshaft.

Fabrication and Mechanical Characterization of a Microscale Electrophoretic Polymer Based on MEMS Technology

Microscale polyurethane modified epoxy resin film has been fabricated using MEMS tehnologies in the present paper. The effect of different process conditions on the thickness of fabricated film was discussed. The microscale film shows smooth and uniform surface morphology. The tensile test of the film by DMA indicates its tensile strength and Young's modulus are approximately 55MPa and 1.8GPa, respectively. The fracture section of the film was characterized by SEM. In addition, the interface bonding strength of the fabricated film between Ni substrate is much higher than Parylene-C and SU-8. This microscale polymer film is promising in several smart MEMS fields, especially bio-MEMS structures.

Mechanical Behaviors of Magnesium Alloy AZ61 under Different Strain Rates and Heating Rates

The effects of strain rate (SR) and heating rate (HR) on the mechanical behaviors of the tensile specimens of magnesium alloy AZ61 were experimentally investigated using a Gleeble-1500 thermal-mechanical material testing system. It showed that the higher the temperature is, the lower the ultimate strength of the specimens will be. The higher the heating rate is, the higher the ultimate strength of the specimens will be. The metallurgraphs of the fracture section of the specimens were also experimentally investigated for exploring their failure mechanism under different temperatures and heating rates. It showed that the high temperatures and high heating rates will induce microvoids in the specimens. The microvoids make the specimens failure under relative low loads.

Regular Fracture Control of Pressed Notch Bar under Three-Point Bending

A new method for fabricating crack is introduced by pressing the wedge on bar. The path of the crack propagation is not regular when the ratio of length and diameter is less than 1.8 on the symmetrical support. The load of the wedge for pressing the notch is given in this paper. The 2-D finite element is applied to simulate the crack propagation by the maximum normal stress theory. The experimental results show that the quality of the fracture section will vary with the span on the three-point bending. In order to control the crack propagation along the desired section regularly, the asymmetrical three-point bending is proposed. The simulation results show that when the difference of the two spans is between 11 and 22 in asymmetrical three-point bending under the parameters condition, the good quality of the section will be obtained, and the experimental results also strong support the conclusion.