The energy release rate for hygrothermal coupling elastic materials

In the fracture problems of hydrophilic elastic materials under coupling effects of heat conduction, moisture diffusion and mechanical deformation, the conventional J-integral is no longer path independent. The value of J is unequal to the energy release rate in hygrothermal coupling cases. In the present paper, we derived a general form of the energy release rate for hygrothermal fracture problems of the hydrophilic elastic materials on the basis of energy balance equation in cracked areas. By introducing the constitutive relations and the essential equations of irreversible thermodynamics, a specific expression of the energy release rate was obtained, and the expression can be reformmulated as path independent integrals, which is equivalent to the energy release rate of the fracture body. The path independence of the integrals is then verified numerically.

Effects of Strain Rate on Stress Corrosion of S355 Steel in 3.5% NaCl Solutions

The stress corrosion of S355 steel in 3.5% NaCl solution under the different strain rates was analyzed with the slow strain rate test（SSRT）, the stress corrosion cracking（SCC） behaviors of S355 steel under the different strain rates in the solution were investigated, and the fracture morphologies and compositions of corrosion products under the different strain rates were analyzed with scanning electron microscopy（SEM） and energy dispersive spectrometerry（EDS）, respectively. The experimental results show that the SCC sensitivity index is the highest when the strain rate is 2×10-6, and the medium corrosion is the main reason resulting in the highest SCC sensitivity index. The SCC sensitivity index is the least when the strain rate is 5×10-6, and the stress is the main reason resulting in the stress corrosion. The SCC sensitivity index is the middle when the strain rate is 9×10-6, the interaction of stress and medium is the stress corrosion fracture mechanism.

Microearthquake analysis for hydraulic frac－turing proces

The hydraulic fracture technique is widely applied in the enhancement of petroleum and natural gas productions and in the development of geothermal energy. This technique is also used to create an underground fracture zone system for disposal of solid and liquid wastes. This is the most recent development in the application of industrial techniques to environmental protection scientific problems. Knowledge of mechanical properties and geometrical parameters of a hydraulic fracture zone is important for both energy resource development and safe disposal of waste. Hydraulic fracturing often induces many microearthquakes.Analysis of the spatial temporal distribution of the induced seismicity yields the geometry of a hydraulic fracture zone, and kinetic and dynamic parameters associated with the fracture growth process. Applying a waveform correlation analysis and a space time grid search method, we precisely determined hypocentral locations for 157 microearthquakes induced by hydraulic fracturing. Spatial distribution of the induced seismicity celarly shows the dimension and orientation of a hydraulic fracture zone. Variation of the seismicity distribution in time and space was used to infer the growth rate and direction of the fracture zone. An empirical Greens function(EGF) method was applied to earthquake doublets to retrieve relative source time functions(RSTFs) and to estimate source parameters, such as seismic moment, source radius, and stress drop, for larger microearthquakes. Azimuthal variation of the RSTF of a master event indicates that the source ruptured to the northwest, which aggrees with the fracture zone growth direction. Large variation of stress drops for these induced earthquakes reflects the significant heterogeneity of mechanical properties in the hydraulic fracture zone.

Shear response of β-SiC bulk dependent on temperature and strain rate

The shear responses of β-SiC are investigated using molecular dynamics simulation with the Tersoff interatomic potential. Results show a clear decreasing trend in critical stress,fracture strain and shear modulus as temperature increases. Above a critical temperature, β-SiC bulk just fractures after the elastic deformation. However, below the critical temperature, an interesting pattern in β-SiC bulk emerges due to the elongation of Si-C bonds before fracture. Additionally, the shear deformation of β-SiC at room temperature is found to be dependent on the strain rate. This study may shed light on the deformation mechanism dependent on temperature and strain rate.

Benefit of infusions with ibandronate treatment in children with osteogenesis imperfecta

Background Osteogenesis imperfecta （OI） is a rare bone disease and its effective treatment is relatively deficient. We tried to assess the effects of new bisphosphonate, ibandronate on children with OI.Methods In this open-label, prospective, controlled study, 30 children with OI were enrolled. They received either infusions of ibandronate （2 mg） in every three months or oral calcitriol 0.25 μg daily for 24 months. All patients took 500 mg calcium plus 200 U vitamin D daily together. The endpoints were the change of annual new fracture rate （observed by case history and X ray films of spine）, bone mineral density （BMD, measured by dual energy X-ray absortiometry）, serum concentration of carboxy-telopeptide cross-links of type Ⅰ collagen （CTX, bone resorption marker） and alkaline phosphatase （ALP, bone formation marker） during the follow-up.Results After the cyclic infusions of ibandronate, the annual new fracture rate was significantly decreased from 1.9 to 0.13 time, obviously lower than that of calcitriol group, which decreased from 1.8 to 1.0 time after the treatment （P 〈0.001）.The significant increase of BMD at the lumbar spine, femoral neck, trochanter, total hip was found in the group of ibandronate by 59.0%, 42.0%, 47.5% and 36.6% in time dependent manner （compared with the baseline, P 〈0.001）. The increase of BMD in ibandronate group was greater than that of calcitriol group （P 〈0.001）. The concentrations of ALP and CTX were obviously decreased in ibandronate group, and the reduction of CTX was more significant than that of ALP （P 〈0.001）. The tolerance of the children to ibandronate was quite well. Mild fever and muscle pain were found in 9 cases within 1-3 days after the first infusion of ibandronate, which could relieve after 1-2 days without special management.Conclusions The benefits of cyclic infusions of ibandronate to children with OI are significant because ibandronate could significantly reduce annual bone fracture rate, increase lumbar and hip BMD, preserve vertebral morphometry of patients through inhibition of bone resorption.