The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate （grinding wheels with conic chamfer and grinding wheels with microdiscontinui...The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate （grinding wheels with conic chamfer and grinding wheels with microdiscontinuities on the active surface）. Using these background details, a suggested thesis was put forward regarding the need to develop a device which will allow for the shaping of the macrogeometry of the grinding wheel （cylindrical and conical surfaces） and the microdiscontinuities within the dressing operation simultaneously. The device was presented and prepared in two functional variants （horizontal and vertical mounting of the motor）, then a prototype was described. An example of the grinding wheel active surface, shaped by using this device, was also presented. The theoretical analysis and experimental verification performed determine that the error of shaping the conic chamfer angle within the range of 0-1.5°, using the developed device, is approximately ±3%.展开更多
The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality(geometry,microstructure and wear rate of cladding track).Self-fluxing ferrous allo...The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality(geometry,microstructure and wear rate of cladding track).Self-fluxing ferrous alloy powders were fabricated on Q235 substrate.Based on the uniform design,the distribution of the experimental samples was designed reasonably in the sample space,which greatly improved efficiency and reduced costs.After a series of microstructural characterization,there was no difference in the phase composition of all samples,but the average grain size had a significant difference,which resulted in the change of wear rate.And the relationship among micro-hardness,average grain size and wear rate of the track had also been investigated.Subsequently,an optimization model was established and the optimal process parameters were obtained with excellent wear rate under the geometric constraints.The correctness of optimization model was verified by experiments.展开更多
We consider a mixed problem for a system describing the evolution of sound in a compressible fluid. We describe how to treat a simultaneous exact boundary controllability problem in the sense proposed by J.L. Lions as...We consider a mixed problem for a system describing the evolution of sound in a compressible fluid. We describe how to treat a simultaneous exact boundary controllability problem in the sense proposed by J.L. Lions as well as D. Russell. By using convenient modified multipliers we obtain an observability inequality provided suitable geometric condition on the domain is valid and the speed velocity of the models are related.展开更多
Segregation results in worse mechanical and durability performance of concrete.Therefore,an accurate modelling of segregation is required for reliable mesoscale modelling.In this context,this paper presents a method t...Segregation results in worse mechanical and durability performance of concrete.Therefore,an accurate modelling of segregation is required for reliable mesoscale modelling.In this context,this paper presents a method to develop the geometric mesoscale modelling of concrete taking into account segregation.In this method,coarse aggregate particles are generated as ellipsoids of random geometry and are randomly placed within concrete.The specimen is stratified in different numbers of layers(NoL)that represent different segregation conditions.The geometric models of four concrete mix designs are generated and the relevant key parameters,e.g.aggregate distribution are analysed and validated.In addition,the segregation level of generated models is classified based on the volumetric index and the correspondence between segregation level and the value of NoL is presented.The results show that 1)The generated geometric models with NoL ranging from 1 to 10 align well with real segregation in concrete and can accurately represent the majority of segregation cases resulting from various experimental factors;2)The NoL reflects the segregation level:more layers indicate a more heterogeneous mesostructure;3)The larger aggregates of the generated models tend to settle at the bottom,while smaller aggregates rise toward the top,leading to uneven vertical distribution,especially as the NoL increases;4)the mix 1 with low aggregate content can represent the construction material with large segregation,while the mix 2 is inverse.展开更多
文摘The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate （grinding wheels with conic chamfer and grinding wheels with microdiscontinuities on the active surface）. Using these background details, a suggested thesis was put forward regarding the need to develop a device which will allow for the shaping of the macrogeometry of the grinding wheel （cylindrical and conical surfaces） and the microdiscontinuities within the dressing operation simultaneously. The device was presented and prepared in two functional variants （horizontal and vertical mounting of the motor）, then a prototype was described. An example of the grinding wheel active surface, shaped by using this device, was also presented. The theoretical analysis and experimental verification performed determine that the error of shaping the conic chamfer angle within the range of 0-1.5°, using the developed device, is approximately ±3%.
基金Project (51210008) supported by National Natural Science Foundation of China
文摘The purpose was to clarify the relationship between the main process parameters of micro-plasma cladding and the comprehensive quality(geometry,microstructure and wear rate of cladding track).Self-fluxing ferrous alloy powders were fabricated on Q235 substrate.Based on the uniform design,the distribution of the experimental samples was designed reasonably in the sample space,which greatly improved efficiency and reduced costs.After a series of microstructural characterization,there was no difference in the phase composition of all samples,but the average grain size had a significant difference,which resulted in the change of wear rate.And the relationship among micro-hardness,average grain size and wear rate of the track had also been investigated.Subsequently,an optimization model was established and the optimal process parameters were obtained with excellent wear rate under the geometric constraints.The correctness of optimization model was verified by experiments.
文摘We consider a mixed problem for a system describing the evolution of sound in a compressible fluid. We describe how to treat a simultaneous exact boundary controllability problem in the sense proposed by J.L. Lions as well as D. Russell. By using convenient modified multipliers we obtain an observability inequality provided suitable geometric condition on the domain is valid and the speed velocity of the models are related.
基金supported by the Project of the Ministry of Science and Technology High-end Foreign Experts of China(No.G2023014042L)the China Scholarship Council(No.201906370013)the Portuguese Foundation for Science and Technology(UIDB/04625/2020).
文摘Segregation results in worse mechanical and durability performance of concrete.Therefore,an accurate modelling of segregation is required for reliable mesoscale modelling.In this context,this paper presents a method to develop the geometric mesoscale modelling of concrete taking into account segregation.In this method,coarse aggregate particles are generated as ellipsoids of random geometry and are randomly placed within concrete.The specimen is stratified in different numbers of layers(NoL)that represent different segregation conditions.The geometric models of four concrete mix designs are generated and the relevant key parameters,e.g.aggregate distribution are analysed and validated.In addition,the segregation level of generated models is classified based on the volumetric index and the correspondence between segregation level and the value of NoL is presented.The results show that 1)The generated geometric models with NoL ranging from 1 to 10 align well with real segregation in concrete and can accurately represent the majority of segregation cases resulting from various experimental factors;2)The NoL reflects the segregation level:more layers indicate a more heterogeneous mesostructure;3)The larger aggregates of the generated models tend to settle at the bottom,while smaller aggregates rise toward the top,leading to uneven vertical distribution,especially as the NoL increases;4)the mix 1 with low aggregate content can represent the construction material with large segregation,while the mix 2 is inverse.
