Evolution of Microstructure, Mechanical Properties and Residual Stress of a Cold Rolled Invar Sheet Due to Heat Treatment

Invar alloy possesses a uniquely low coefficient of thermal expansion, making it an ideal material for fine metal masks. To manufacture fine metal masks, Invar alloys are often cold-rolled, during which residual stress develops. Heat treatment is an effective means to control residual stress that develops within Invar sheets after cold rolling, but the treatment should be carried out with care. In this article, a comprehensive study on the effect of heat treatment on the residual stress, microstructure, and mechanical properties of a cold-rolled Invar sheet is reported. We show that while both recovery and recrystallization are effective means of reducing residual stress, substantial microstructural changes and, therefore, notable changes in mechanical properties and residual stress, occur after recrystallization. Moreover, residual stress release due to recrystallization can be affected by microstructure and texture prior to heat treatment as these factors play a significant role in recrystallization.

An acoustic emission source localization approach based on time-reversal technology for additive manufacturing

The metal additive manufacturing process can inevitably lead to a great temperature gradient in the workpiece. Therefore, the thermal stress deformation and defects seriously affect the processing quality. In this paper, an array acoustic probe is designed on the base plate with the consideration of the time reversal technology. Corresponding simulations is implemented, which are designed to verify the ability of detecting and positioning the workpiece stress release acoustic emission signal. The simulation results demonstrate that the proposed method can position and monitor the random acoustic emission.

Curcumin and Its Analogs as Potential Epigenetic Modulators: Prevention of Diabetes and Its Complications

<b><i>Background:</i></b> The pathobiology of diabetes and associated complications has been widely researched in various countries, but effective prevention and treatment methods are still insufficient. Diabetes is a metabolic disorder of carbohydrates, fats, and proteins caused by an absence of insulin or insulin resistance, which mediates an increase of oxidative stress, release of inflammatory factors, and macro- or micro-circulation dysfunctions, ultimately developing into diverse complications. <b><i>Summary:</i></b> In the last decade through pathogenesis research, epigenetics has been found to affect metabolic diseases. Particularly, DNA methylation, histone acetylation, and miRNAs promote or inhibit diabetes and complications by regulating the expression of related factors. Curcumin has a wide range of beneficial pharmacological activities, including anti-inflammatory, anti-oxidation, anticancer, anti-diabetes, anti-rheumatism, and increased immunity. <b><i>Key Messages:</i></b> In this review, we discuss the effects of curcumin and analogs on diabetes and associated complications through epigenetics, and we summarize the preclinical and clinical researches for curcumin and its analogs in terms of management of diabetes and associated complications, which may provide an insight into the development of targeted therapy of endocrine diseases.

Intensity and isoseismal map of 25th November 2007 Delhi earthquake

An earthquake of magnitude ML: 4.3 occurred on 25th November 2007 (2312 UTC) in Delhi with hypocenter at 28.56° N / 77.08° E and focal depth 33.1 km. The epicenter was at about 21 km SW of Delhi University. It was widely felt in and around Delhi and created panic among the local populace. A macroseismic survey was conducted in about ten days starting from 27th November, 2007 at 89 locations covering an area of about 1500 sq. km in Delhi and its neighborhood through a questionnaire. The results of the macroseismic survey allowed establishment of spatial distribution of the earthquake effects in the form of isoseismal map generated using geo-statistical analysis tool of ArcGIS 9.1. The isoseismal map shows that most parts of Delhi region experienced an intensity of V on MMI scale, except on northern most region of Delhi where intensity was found IV. The mean isoseismal radii for the zones V, IV, III and II are 29.13, 57.78, 83.63 and 100.75 km, respectively. The orientation of elongated epicentral track of intensity field shows that the stress release was pronounced along Delhi-Sargodha ridge and earthquake was attributed to activities of this ridge.

Crack Group Effect Analysis of the Stress-Release Boot of Solid Rocket Motor Based on Numerical Simulation

Due to the complex process of the insulation layer patch in solid rocket motor (SRM), only manual patch could be used. Sometimes weak bonding or debonding in each joint surface was inevitable. This study is aimed at determining the crack group effect of insulation and interfacial debonded crack in the wide-temperature SRM. The crack group appeared in the front area of the ahead stress-release boot and was induced by low temperature, axial overload, or interface bonding failure. Based on the viscoelastic finite element method, singular crack elements and singular interfacial crack elements at the tips of crack group were established to calculate J -integral. Varying according to the length and position of cracks, the J -integral of crack tips was, respectively, calculated to prejudge their stability and the crack group effect. The results showed that collinear crack group appeared in the front stress-release boot layer, and the crack group had a certain shielding effect on the main crack when the SRM was launched at low temperature. When noncollinear crack group appeared in the front stress-release boot layer, the crack group effect changed with the length of the main crack. The crack group first had a shielding effect on the main crack and then had a strong strengthening effect. The experimental test of the simulated specimen revealed that numerical simulation results matched the experimental test results.

From Nucleation to Percolation: The Effect of System Size when Disorder and Stress Localization Compete

A phase diagram for a one-dimensional fiber bundle model is constructed with a continuous variation in two parameters guiding the dynamics of the model: strength of disorder and range of stress relaxation. When the range of stress relaxation is very low, the stress concentration plays a prominent role and the failure process is nucleating where a single crack propagates from a particular nucleus with a very high spatial correlation unless the disorder strength is high. On the other hand, a high range of stress relaxation represents the mean-field limit of the model where the failure events are random in space. At an intermediate disorder strength and stress release range, when these two parameters compete, the failure process shows avalanches and precursor activities. As the size of the bundle is increased, it favors a nucleating failure. In the thermodynamic limit, we only observe a nucleating failure unless either the disorder strength is extremely high or the stress release range is high enough so that the model is in the mean-field limit. A complex phase diagram on the plane of disorder strength, stress release range, and system size is presented showing different failure modes - 1) nucleation 2) avalanche, and 3) percolation, depending on the spatial correlation observed during the failure process.

ZRO Drift Reduction of MEMS Gyroscopes via Internal and Packaging Stress Release

Zero-rate output (ZRO) drift induces deteriorated micro-electromechanical system (MEMS) gyroscope performances, severely limiting its practical applications. Hence, it is vital to explore an effective method toward ZRO drift reduction. In this work, we conduct an elaborate investigation on the impacts of the internal and packaging stresses on the ZRO drift at the thermal start-up stage and propose a temperature-induced stress release method to reduce the duration and magnitude of ZRO drift. Self-developed high-Q dual-mass tuning fork gyroscopes (TFGs) are adopted to study the correlations between temperature, frequency, and ZRO drift. Furthermore, a rigorous finite element simulation model is built based on the actual device and packaging structure, revealing the temperature and stresses distribution inside TFGs. Meanwhile, the relationship between temperature and stresses are deeply explored. Moreover, we introduce a temperature-induced stress release process to generate thermal stresses and reduce the temperature-related device sensitivity. By this way, the ZRO drift duration is drastically reduced from ~2000 s to ~890 s, and the drift magnitude decreases from ~0.4 °/s to ~0.23 °/s. The optimized device achieves a small bias instability (BI) of 7.903 °/h and a low angle random walk (ARW) of 0.792 °/√ h, and its long-term bias performance is significantly improved.

Analysis of the Impact of Coulomb Stress Changes of Tehoru Earthquake, Central Maluku Regency, Maluku Province

The Tehoru earthquake occurred due to the release of stress in rocks. There is a release of energy as an earthquake as a result of the rock elasticity limit has been exceeded because the rock is no longer able to withstand the stress. One method to determine the distribution of earthquake stress is the Coulomb stress change method. The study aimed to determine the DCS of the Tehoru earthquake, Seram Island, and the effect of the main earthquake stress release on aftershocks. The research results show that the DCS distribution of the Tehoru June 16, 2021 earthquake is shown with negative lobes and positive lobes. The negative lobe is found in an area that is perpendicular to the fault plane and has been identified as having experienced relaxation, so there may be still aftershocks with stress values ranging from (0.0 – 0.3) bar. The dominant positive lobe occurs next to the southern end of the fault plane, too much located in the area of increasing Coulomb stress with values ranging from (0.2 - 0.6) bar