Papers by Keyword: Dwell Time

Abstract: The Electrical Resistance Welding (ERW) of Magnesium and Aluminium is more difficult than steel because the welding machines must provide high currents and exact pressures in order to provide the heat necessary to melt the magnesium for proper fusion at the interface in order to produce a sound weld. Further, resistance welding of magnesium requires a backup plate made of steel to conduct the heat to the workpiece material. To overcome this problem, Friction Stir Spot Welding (FSSW) has been developed. In this study, the hardness distribution and the tensile shear strength of FSSW welds in the AZ31B Magnesium alloy has been investigated and it has been found that tool rotational speed and dwell time plays a major role in determining the weld strength. From the experimental study, a tool rotational speed of 1100 rpm and dwell time of 20 s produced good shear strength of 2824 N and the corresponding grain size was 4.54 μm. This result is very well supported by microstructural examinations and hardness distribution studies.

Abstract: Recent investigations revealed major fluctuations in the material properties of selective laser melted AlSi10Mg, which corresponded with the varying precipitation-hardening state of the microstructure, caused by the differing dwell times at elevated temperatures. It was indicated that a subsequent heat treatment balances the age-hardening and results in a homogenized material strength. In order to further investigate this statement selective laser melted AlSi10Mg samples were subject to multiple post-heat-treatments. Subsequently, the surface hardness and tensile strength was determined and compared with the as-built results. The post-heat-treatment led to an arbitrary occurrence of rupture, indicating a successful homogenization, coupled with a remarkable improvement in ductility, but to the costs of a lowered tensile strength, which was highly dependent on the chosen heat-treatment procedure.

Abstract: Strain-controlled low cycle fatigue (LCF) and creep-fatigue interaction (CFI) tests of K447A are conducted at 760oC in order to investigate the effects of different dwell times and strain ratios on the fatigue behavior and life. For the cases of stain ratio R_ε=-1 with balanced hold time, the tensile and compressive mean stresses will generate. For the case of stain ratio R_ε=-1 with compressive holding 60s, the tensile mean stress will produce. For the case of stain ratio R_ε=-1 with tensile holding 60s, the compressive mean stress will produce. For the cases of stain ratio R_ε=0.1 and R_ε=-1with no hold time, the tensile mean stress will produce. The cyclic damage accumulation (CDA) method and modified CDA method were employed to predict the fatigue life for K447A, respectively. The fatigue life predicted by CDA method is within the scatter band of 18.2X. The fatigue life predicted by the modified CDA method agrees very well with the experimental life and the predicted life is well within the scatter band of 3.1X, which means that the modified CDA method is able to consider the influences of dwell time and strain ratio on the fatigue life of K447A.

Abstract: Thanks to recent technological advances in the field of eye tracking, eye typing provides means of communication for people with severe disabilities. Typing with gaze using dwell time has been made possible by the development of eye tracking technologies. Recent research indicates that pupil size is viewed as a subtle cue of people is making a decision. Therefore, it may help to infer users’ willing of typing. The present study describes the design process for improving eye typing by adding pupil size index into dwell time triggering. Experimental evaluations showed that the approach was effective; design considerations for such optimization of the gaze typing interfaces are discussed.

Abstract: The short-time dwell time of BRT is hard to predict. Considering impacts of complex traffic environment, we can predict the value more effectively by using a new hybrid method, which is mixed with ARIMA (Autoregressive Integrated Moving Average Model), predicting the self-relevant linear part and SVM, predicting residual nonlinear part, than the single ARIMA model and SVM model. The dwell times of BRT line1in Chang Zhou have proved this thesis.

Abstract: Strain-controlled low cycle fatigue (LCF) and creep-fatigue interaction (CFI) tests of an equiaxed crystal nicke-base superalloy were conducted at 850oC in order to investigate the effects of different dwell times and strain ratios on the fatigue behavior and life distribution. The cyclic damage accumulation (CDA) method and modified CDA method were employed to predict the fatigue life for the superalloy under complex loading condition, respectively. CDA method is employed to predict the fatigue life for the superalloy and the predicted fatigue life is within the scatter band of±6X. The fatigue life predicted by the modified CDA method agrees very well with the experimental fatigue life and the predicted fatigue life is well within the scatter band of±3X, which means that the modified CDA method is able to consider the influences of dwell time and strain ratio on the fatigue life for the superalloy.

Abstract: Based on the mechanism of magnetorheological finishing(MRF), a material removal model was established. The dwell time function was solved by Jansson-Van Cittert algorithm to accomplish the kernel module design. Thus the control software of aspheric optics in MRF was designed. In order to verify accuracy of the processing control software, experiments were carried out on large aperture aspheric optics and the wavefront error of elements was achieved rapidly convergence. It is proved that the software could control the whole polishing process accurately.

Abstract: This paper addresses stability properties of linear switched positive systems composed of continuous-time subsystems and discrete-time subsystems. Based on the common linear copositive Lyapunov functions, stability of the positive systems is discussed under arbitrary switching. Moreover, a sufficient condition on the minimum dwell time that guarantees the stability of linear switched positive systems. The dwell time analysis interprets the stability of linear switched positive systems through the distance between the eigenvector sets. Thus, an explicit relation in view of stability is obtained between the family of the involved subsystems and the set of admissible switching signals.

Abstract: Although Single Point Diamond Turning (SPDT) can do pretty well in optical surfacing of large scale KDP crystal, both the surface accuracy and integrity are considerably high; meanwhile as the defects of micro-waveness and stress are inevitable, the laser-induced damage threshold of KDP optical elements after SPDT still cannot be satisfied. Because of the characters of deliquescent and water-soluble, the process of computer controlled Micro-nano deliquescence is attempted to remove the residual micro-waveness on KDP surface after SPDT. Based on the assumption of Preston and the characters of Micro-nano deliquescence, the model of material removal ratio is suggested, the dwell time for ascertained KDP surface is solved, the processing of computer controlled Micro-nano deliquescence is simulated and the processed surface condition on theory is obtained. Besides, the influences of different parameters on the surfacing efficiency and accuracy are analyzed. Finally, three polishing tracks are comparatively analyzed. The simulation results are quite important in guiding the experimental polishing of large scale KDP by computer controlled Micro-nano deliquescence

Abstract: In this work the dynamics of particle removal by aerosol spray is investigated. Local dwell time of spray cleaning is calculated numerically from the process conditions, and some striking topological similarities between the particle removal efficiency and dwell time profiles are observed. The particle removal rates, defined as the normalized speed of particle removal, are not constant during a typical process, with the highest removal rate for the first tens of milliseconds and a temporal decay as time elapses. Increasing N₂ flow rate results in an enhancement in both the particle removal efficiency and the particle removal rate.