Search

In this study, the ductile iron ingots are cast using a metal mold, and the riser neck diameter is changed to control the micro-shrinkage porosity, which can affect the ultra-low temperature toughness of ferritic ductile iron. The metallographic structure and micro-shrinkage porosity were observed by an Axiovert200 MAT measurer metallographic microscope and an MLA 250 (FEI quanta) scanning electron microscope, and the number and diameter of graphite nodules and micro-shrinkage porosity size were measured by Nano Measurer 1.2 software. The effect of micro-shrinkage porosity on the ultra-low temperature toughness of ferritic ductile iron was studied. It is found that the impact energy of ductile iron decreases with the increase of micro-shrinkage porosity size, and the influence of micro-shrinkage porosity is more obvious with the decrease of temperature. The results point out that the micro-shrinkage porosity becomes the key factor affecting the ultra-low temperature impact toughness of ductile iron when the spheroidization rate of ferritic ductile iron is greater than 98% and the number of graphite nodules is more than 810 mm−2. The impact energy of ferritic ductile iron can still reach more than 12 J at −70°C when the length of micro-shrinkage porosity is less than 3.7 μm.

This paper is focus on power energy distribution control of auxiliary power unit (APU) for a range-extended electric vehicle (RE–EV). Based on the working characteristic of the engine and the generator, a coordination control strategy of RE–EV is proposed. A regulating rule of APU control system speed and torque which meets the power demand of the RE–EV is designed. The PID and fuzzy control methods of engine speed are discussed by simulation analysis. In order to investigate the APU control processing, the incremental PID and fuzzy control algorithms are used to achieve speed control in the APU test bench. The influence on tuning parameters, control period and the working condition are analyzed from test results. The coordination control strategies of engine and generator are realized and verified by experimental research. [ABSTRACT FROM AUTHOR]