Effects Of Wheel Velocity Research Articles

Effect of Spun Velocities and Composition on the Microstructure and Transformation Temperatures of TiNi Shape Memory Ribbons

Ti‒50.13Ni and Ti‒49.62Ni (at.%) shape memory alloy ribbons were fabricated by melt-spinning method at different circumferential wheel velocities. The effects of wheel velocity, chemical composition and heat treatments on microstructure and Transformation temperature were investigated. Differences in wheel velocity led to differences in cooling rate and sample dimension, as well as in phase transformation temperatures. Two heat treatment conditions were studied, 350°C for 1h and 350°C for 5h. In the samples produced at high wheel velocity and heat-treated at 350°C for 5h, nanosized Ti-rich precipitates were observed in both chemical compositions. Cross-sectional microstructure was studied by optical microscopy; SEM was used to study the nanometric grains and nano precipitation. The transformation temperatures were analyzed by DSC.

Effect of Spun Velocities and Composition on the R‒phase and Thermomechanical Behavior in Ti‒Ni Ribbons Electrically Heated

This work deals with structural, electrical and mechanical characterization of Ti‒50.13Ni and Ti‒49.62Ni (at.%) shape memory alloys (SMAs) fabricated at different circumferential wheel velocities. The effect of wheel velocity, chemical composition and heat treatments are investigated. The characterization of crystallographic phases of the Ti‒Ni ribbons was carried out using X-ray diffraction. Electrical resistance variations as function of temperature (∆R/R %) were analyzed using a non-commercial technique, which consists in a thermal-adjustable bath apparatus revealing the temperatures of B2→R→B19´ two stage transformation, whereby the presence of R‒phase can be definitively confirmed. The Stress-Assisted Two-Way Memory Effect was measured by an own designed apparatus with an Linear Variable Differential Transformer captor and a current controlled heating, and results indicate that the as-spun condition, promotes the Stress-Assisted Two-Way Memory Effect. On the other hand, increments in Ni content tend to decrease transformation temperatures and high wheel velocities help to the R‒phase formation.

Damage of a Hadfield steel crossing due to wheel rolling impact passages

The damage of a Hadfield steel crossing in a railway turnout due to wheel rolling impact passages is investigated numerically. A three dimensional elastic–plastic finite element model has been developed by taking into account non-linear material properties, dynamic wheel impact and wheel–crossing contact. The effects of wheel velocity on the damage and deformation of the crossing is analysed. In the present study, four rolling velocities of the wheel, i.e., 50km/h, 100km/h, 150km/h, and 200km/h were chosen. The wheel exhibits elastic material behaviour, whereas the crossing exhibits elastic–plastic material behaviour. To represent the damage and deformation behaviours of the crossing, non-linear dynamic work hardening is further included in the calculation. Dynamic stress and strain in the crossing were obtained by the explicit finite element method, including the maximum von Mises stress, the maximum strain, the maximum horizontal stress, perpendicular stress and parallel stress. The snake-like motion of the wheel rolling on the crossing was verified by the simulation; in the meantime, there is a significant impact load on the nose rail, which caused a big von Mises stress in the nose rail. The big von Mises stress is the main reason for the nose rail fatigue spalling. The maximum von Mises stress and maximum strain in the nose rail increase with the train speed increasing. The study provides a method for the further research on the fatigue and the wear behaviours of railway crossings.

The Effect of Wheel Velocity and Shape on Rotating Airflow in Super-High-Speed Grinding

The Effect of Wheel Velocity and Shape on Rotating Airflow in Super-High-Speed Grinding