The lath-or plate-shaped bainitic ferrite of low and medium carbon alloy steels consists of packets of ferrite sublaths which are composed of many finer and regular ferrite blocks.They are uniform shear growth units o...The lath-or plate-shaped bainitic ferrite of low and medium carbon alloy steels consists of packets of ferrite sublaths which are composed of many finer and regular ferrite blocks.They are uniform shear growth units of bainitic phase transformation.No carbide is precipitated from them.The bainitic O-carbides are precipitated from γ-α interface or carbon-rich austenite.The mode of arrangement of the units in ferrite sublath packet is in uni-or bi-di- rection.Single surface relief is produced by the accumulation of uniform shear strains with all the ferrite units arranged unidirectionally in a sublath packet,while tent-shaped surface relief is formed by the integration of the uniform shear strains of two groups with ferrite units piling up in two directions and growing face to face;whereas if they grow back to back,the integra- tion will be responsible for invert-tent-shaped surface relief.The interface trace between two groups of ferrite units in a sublath packet is shown as“midrib”.展开更多
The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculat...The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.展开更多
The precipitates in P92 steel after long-term service in an ultra-supercritical unit were investigated by field-emission scanning electron microscopy and transmission electron microscopy and were found to mainly consi...The precipitates in P92 steel after long-term service in an ultra-supercritical unit were investigated by field-emission scanning electron microscopy and transmission electron microscopy and were found to mainly consist of M23 C6 carbides,Laves phase,and MX carbonitrides.No Z-phase was observed.M23 C6 carbides and Laves phase were found not only on prior austenite grain boundaries,martensite lath boundaries,and subgrain boundaries but also in lath interiors,where two types of MX carbonitrides—Nb-rich and V-rich particles—were also observed but the "winged" complexes were hardly found.Each kind of precipitate within the martensite laths exhibited multifarious morphologies,suggesting that a morphological change of precipitates occurred during long-term service.The M23 C6 carbides and Laves phase coarsened substantially,and the latter grew faster than the former.However,MX carbonitrides exhibited a relatively low coarsening rate.The effect of the evolution of the precipitate phases on the creep rupture strength of P92 steel was discussed.展开更多
In order to ensure that the system has the advantage of light weight and vibration absorption, the steel rope is used as a flexible transmission part. A flexible drive unit(FDU) is developed, whose features are guided...In order to ensure that the system has the advantage of light weight and vibration absorption, the steel rope is used as a flexible transmission part. A flexible drive unit(FDU) is developed, whose features are guided by steel rope, increasing force by the movable pulley group, modular, convenient and flexible. Dynamics model for controller is deduced based on the constitutive equation of viscoelasticity. Controller is designed for position control and is based on the viscoelasticity dynamics model compensation control strategy proposed. The control system is based on the TURBO PMAC multi-axis motion control card.Prototype loading experiments and velocity experiments results show that the FDU can reach 2 Hz with no load and the max speed of 30(°)/s. The FDU has the capability of the load torque 11.2 N·m and the speed of 24(°)/s simultaneously, and the frequency response is 1.3 Hz. The FDU can be used to be the pitch joint of hip for biped robot whose walking speed is 0.144 km/h theoretically.展开更多
A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The ...A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.展开更多
Differential scanning calorimetry (DSC) provides easy screening for thermal hazard evaluation. Here, we investigate the difference between using glass and stainless-steel vessels on the DSC measurement of exothermic d...Differential scanning calorimetry (DSC) provides easy screening for thermal hazard evaluation. Here, we investigate the difference between using glass and stainless-steel vessels on the DSC measurement of exothermic decomposition energy (QDSC) for 41 chemical substances (containing nitro, halogen, peroxide, and sulfur groups, and hydrazine bonds). Two borosilicate glass vessels (capillary and ampule) and one stainless-steel vessel were used. All QDSC values obtained were investigated with reference to the permissible fluctuation range specified by the ASTM (American Society for Testing and Materials) international Both glass vessels produced very similar QDSC values, despite different sample scales. The QDSC values obtained with the glass vessels were generally roughly within the variation tolerance range of the stainless-steel vessel. Notable exceptions were halogen- or sulfur-containing compounds;these exhibited smaller QDSC values with glass vessels in almost all cases. We will investigate whether certain structures in compounds react with stainless steel. The vessel material choice is crucial in evaluating the true reactivity of a substance.展开更多
文摘The lath-or plate-shaped bainitic ferrite of low and medium carbon alloy steels consists of packets of ferrite sublaths which are composed of many finer and regular ferrite blocks.They are uniform shear growth units of bainitic phase transformation.No carbide is precipitated from them.The bainitic O-carbides are precipitated from γ-α interface or carbon-rich austenite.The mode of arrangement of the units in ferrite sublath packet is in uni-or bi-di- rection.Single surface relief is produced by the accumulation of uniform shear strains with all the ferrite units arranged unidirectionally in a sublath packet,while tent-shaped surface relief is formed by the integration of the uniform shear strains of two groups with ferrite units piling up in two directions and growing face to face;whereas if they grow back to back,the integra- tion will be responsible for invert-tent-shaped surface relief.The interface trace between two groups of ferrite units in a sublath packet is shown as“midrib”.
文摘The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.
文摘The precipitates in P92 steel after long-term service in an ultra-supercritical unit were investigated by field-emission scanning electron microscopy and transmission electron microscopy and were found to mainly consist of M23 C6 carbides,Laves phase,and MX carbonitrides.No Z-phase was observed.M23 C6 carbides and Laves phase were found not only on prior austenite grain boundaries,martensite lath boundaries,and subgrain boundaries but also in lath interiors,where two types of MX carbonitrides—Nb-rich and V-rich particles—were also observed but the "winged" complexes were hardly found.Each kind of precipitate within the martensite laths exhibited multifarious morphologies,suggesting that a morphological change of precipitates occurred during long-term service.The M23 C6 carbides and Laves phase coarsened substantially,and the latter grew faster than the former.However,MX carbonitrides exhibited a relatively low coarsening rate.The effect of the evolution of the precipitate phases on the creep rupture strength of P92 steel was discussed.
基金Project(2006AA04Z201,2012AA041601)supported by the National High-Tech Research and Development Program of China
文摘In order to ensure that the system has the advantage of light weight and vibration absorption, the steel rope is used as a flexible transmission part. A flexible drive unit(FDU) is developed, whose features are guided by steel rope, increasing force by the movable pulley group, modular, convenient and flexible. Dynamics model for controller is deduced based on the constitutive equation of viscoelasticity. Controller is designed for position control and is based on the viscoelasticity dynamics model compensation control strategy proposed. The control system is based on the TURBO PMAC multi-axis motion control card.Prototype loading experiments and velocity experiments results show that the FDU can reach 2 Hz with no load and the max speed of 30(°)/s. The FDU has the capability of the load torque 11.2 N·m and the speed of 24(°)/s simultaneously, and the frequency response is 1.3 Hz. The FDU can be used to be the pitch joint of hip for biped robot whose walking speed is 0.144 km/h theoretically.
文摘A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.
文摘Differential scanning calorimetry (DSC) provides easy screening for thermal hazard evaluation. Here, we investigate the difference between using glass and stainless-steel vessels on the DSC measurement of exothermic decomposition energy (QDSC) for 41 chemical substances (containing nitro, halogen, peroxide, and sulfur groups, and hydrazine bonds). Two borosilicate glass vessels (capillary and ampule) and one stainless-steel vessel were used. All QDSC values obtained were investigated with reference to the permissible fluctuation range specified by the ASTM (American Society for Testing and Materials) international Both glass vessels produced very similar QDSC values, despite different sample scales. The QDSC values obtained with the glass vessels were generally roughly within the variation tolerance range of the stainless-steel vessel. Notable exceptions were halogen- or sulfur-containing compounds;these exhibited smaller QDSC values with glass vessels in almost all cases. We will investigate whether certain structures in compounds react with stainless steel. The vessel material choice is crucial in evaluating the true reactivity of a substance.
