Yixi Zhao

The Hydrothermal Liquefaction of Rice Husk to Bio-crude Using Metallic Oxide Catalysts

Hydrothermal liquefaction of rice husk was investigated in a 10-ml stainless steel micro-reactor. Without catalyst, the bio-crude yields are in the range of 11.8–23.8 wt%, depending on temperature, reaction time, and water/rice husk mass ratio. With catalysts, the bio-crude yields are obviously increased and the highest bio-crude yield of 32.5 wt% is obtained with La2O3 catalyst at 300°C for 10 min and a water/rice husk mass ratio of 5. The elemental analysis shows that the oxygen contents of bio-crude are significantly decreased by La2O3 and Dy2O3 catalysts, respectively. The highest higher heating value (31.78 MJ/kg) of bio-crude is obtained with La2O3 catalyst, which is obviously higher than that of the raw material (16.19 MJ/kg). Energy balance results show that La2O3 and Dy2O3 catalysts have a beneficial effect on energy recovery and energy consumption ratio. Gas chromatography-mass spectrometry and Fourier transform-infrared analysis show that La2O3 and Dy2O3 decrease the contents of phenols and acids and promote the formation of hydrocarbon (alkenes and alkynes) and esters.

Microstructure-Based RVE Approach for Stretch-Bending of Dual-Phase Steels

Fracture behavior and micro-failure mechanism in stretch-bending of dual-phase (DP) steels are still unclear. Representative volume elements (RVE) have been proved to be an applicable approach for describing microstructural deformation in order to reveal the micro-failure mechanism. In this paper, 2D RVE models are built. The deformation behavior of DP steels under stretch-bending is investigated by means of RVE models based on the metallographic graphs with particle geometry, distribution, and morphology. Microstructural failure modes under different loading conditions in stretch-bending tests are studied, and different failure mechanisms in stretch-bending are analyzed. The computational results and stress-strain distribution analysis indicate that in the RVE models, the strain mostly occurs in ferrite phase, while martensite phase undertakes most stress without significant strain. The failure is the results of the deformation inhomogeneity between martensite phase and ferrite phase. The various appearance and growth of initial voids are different depending on the bending radius.

Stamping failure analysis of advanced high strength steel sheet based on non-uniform local deformation through thickness

The phenomenon “Shear fracture” is often observed in the stretch-bending process of stamping over small radius with advanced high strength steels (AHSS). It occurs parallel to and near the die radius in the stretch-bending test. Since traditional Forming Limit Diagram (FLD) is unable to describe this type of failure, experimental and simulation works were constructed in this paper to investigate and predict the shear fracture. Fracture experiments were carried out through a stretch-bending test system, and failure mode was observed. There is no obviously thinning at the shear fracture surface. Further research shows that the initial crack of shear fracture occurs at the outer layer of specimen at die radius position. Finite element (FE) models were built for stretch-bending test with 3D element. The non-uniform local deformation through thickness corresponding to bending position was obtained and analyzed. Cockcroft & Latham fracture criterion is used. The outer layer of specimen at bending position reaches the critical fracture state firstly, which agrees well with experiments. Different fracture criteria are also compared and selected to determine this fracture. Results show that based on the non-uniform local deformation, the initial crack location of shear fracture at small radius can be effectively predicted by fracture criteria related to the maximum principle stress.