Northeastern University (China)

About: Northeastern University (China) is a education organization based out in Shenyang, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 36087 authors who have published 36125 publications receiving 426807 citations. The organization is also known as: Dōngběi Dàxué & Northeastern University (东北大学).

Investigation of different grain shapes and dressing to predict surface roughness in grinding using kinematic simulations

Abstract: This paper presents a comprehensive study of a computationally efficient kinematic simulation to predict workpiece surface roughness in grinding using three different abrasive grain shapes (sphere, truncated cone, and cone) and a single-point diamond dressing model having both a ductile cutting and brittle fracture component. The resulting predicted workpiece surface roughness was experimentally validated for three different workpiece speeds, three different dressing depths of cut and three different dressing overlap ratios. For the surface grinding and single-point dressing conditions used in this research, the results showed that the dressing parameters used in the simulations supersede the assumed abrasive grain shape in their ability to influence the predicted workpiece surface finish. Furthermore, the corresponding average measured and predicted workpiece surface roughness agreed within approximately 7–11%.

Fixed-Priority Multiprocessor Scheduling with Liu and Layland's Utilization Bound

Abstract: Liu and Layland discovered the famous utilization bound for fixed-priority scheduling on single processor systems in the 1970's. Since then, it has been a long standing open problem to find fixed-priority scheduling algorithms with the same bound for multiprocessor systems. In this paper, we present a partitioning-based fixed-priority multiprocessor scheduling algorithm with Liu and Layland's utilization bound.

Microstructure–properties relationship in a one-step quenched and partitioned steel

Abstract: To comprehensively analyze the relationship between the microstructure and mechanical properties in a one-step quenched and partitioned (Q&P) steel, Q&P processes with different partitioning time were applied to a low-carbon steel. Microstructures were characterized by means of EPMA, XRD, EBSD and TEM. The dislocation density of martensite was calculated using the Williamson–Hall method. Mechanical properties were measured by uniaxial tensile tests. Results show that the microstructures consist of lath martensite accompanying with both film-like inter-lath retained austenite and blocky retained austenite. Martensite laths broaden with prolonged partitioning time. The amount of retained austenite increases first and decreases with the critical partitioning time of 100 s. The relation between the microstructure and properties was clarified by analyzing the stress–strain curves stage by stage combining with the substructure of martensite and the condition of retained austenite. The presence of retained austenite decreases the elastic limit and influences on the yield strength for its early plastic deformation. Two kinds of nano-scaled carbide appearing in the specimens partitioned longer than 100 s promote the austenite decomposition and play the main role in increasing the yield strength. The interaction of the dislocations in martensite and the transformation induced plasticity (TRIP) effect of retained austenite increase the work hardening rate and improve both the ultimate tensile strength (UTS) and the uniform elongation.

Experimental investigation on mechanical damage characteristics of sandstone under triaxial cyclic loading

Abstract: The mechanical damage characteristics of sandstone subjected to cyclic loading is very significant to evaluate the stability and safety of deep excavation damage zones. However to date, there are very few triaxial experimental studies of sandstone under cyclic loading. Moreover, few X-ray micro-computed tomography (micro-CT) observations have been adopted to reveal the damage mechanism of sandstone under triaxial cyclic loading. Therefore, in this research, a series of triaxial cyclic loading tests and X-ray micro-CT observations were conducted to analyse the mechanical damage characteristics of sandstone with respect to different confining pressures. The results indicated that at lower confining pressures, the triaxial strength of sandstone specimens under cyclic loading is higher than that under monotonic loading; whereas at confining pressures above 20 MPa, the triaxial strength of sandstone under cyclic loading is approximately equal to that under monotonic loading. With the increase of cycle number, the crack damage threshold of sandstone first increases, and then significantly decreases and finally remains constant. Based on the damage evolution of irreversible deformation, it appears that the axial damage value of sandstone is all higher than the radial damage value before the peak strength; whereas the radial damage value is higher than the axial damage value after the peak strength. The evolution of Young's modulus and Poisson's ratio of sandstone can be characterized as having four stages: (i) Stage I: material strengthening; (ii) Stage II: material degradation; (iii) Stage III: material failure and (iv) Stage IV: structure slippage. X-ray micro-CT observations demonstrated that the CT scanning surface images of sandstone specimens are consistent with actual surface crack photographs. The analysis of the cross-sections of sandstone supports that the system of crack planes under triaxial cyclic loading is much more complicated than that under triaxial monotonic loading. More axial and lateral tensile cracks were observed in the specimens under cyclic loading than under monotonic loading.