This paper deals with geometric error modeling and sensitivity analysis of an overconstrained parallel tracking mechanism. The main contribution is the consideration of overconstrained features that are usually ignore...This paper deals with geometric error modeling and sensitivity analysis of an overconstrained parallel tracking mechanism. The main contribution is the consideration of overconstrained features that are usually ignored in previous research. The reciprocal property between a motion and a force is applied to tackle this problem in the framework of the screw theory. First of all, a nominal kinematic model of the parallel tracking mechanism is formulated. On this basis, the actual twist of the moving platform is computed through the superposition of the joint twist and geometric errors. The actuation and constrained wrenches of each limb are applied to exclude the joint displacement. After eliminating repeated errors brought by the multiplication of wrenches, a geometric error model of the parallel tracking mechanism is built. Furthermore,two sensitivity indices are defined to select essential geometric errors for future kinematic calibration. Finally, the geometric error model with minimum geometric errors is verified by simulation with SolidWorks software. Two typical poses of the parallel tracking mechanism are selected, and the differences between simulation and calculation results are very small. The results confirm the correctness and accuracy of the geometric error modeling method for over-constrained parallel mechanisms.展开更多
The lifetime of metal rubber isolator and its characteristics during lifetime experiment were studied. The stepped-up test principle was adopted to study the lifetime of resonant frequency, the breakage form of metal ...The lifetime of metal rubber isolator and its characteristics during lifetime experiment were studied. The stepped-up test principle was adopted to study the lifetime of resonant frequency, the breakage form of metal rubber isolator was obtained, and the relation between the energy dissipation, resonant frequency and stiffness was obtained in (available) lifetime of the isolator. Furthermore, the reason for the changes of properties of metal rubber isolator was analyzed with contact model of metal rubber material. The results show that if the resonant amplitude is large, the stiffness of metal rubber isolator will be kept steadily for a long time, its resonant frequency will be stable and the effective working time in the protecting area will be long. The lifetime of metal rubber isolator is more than 1376 h in the experiment. The main failure forms of metal rubber isolator are accumulative wear and breaking of metal wires and spirals. In protecting area the metal rubber isolator can work effectively for a long time, and the effective working time depends on the concrete working condition.展开更多
Silicon carbide and silicon nitride are recognized as phases with very good mechanical properties. Many parts of machines and mechanical devices are made of these materials. Particulate composites basing on both menti...Silicon carbide and silicon nitride are recognized as phases with very good mechanical properties. Many parts of machines and mechanical devices are made of these materials. Particulate composites basing on both mentioned phases have significant potential of properties improvement. The aim of presented work was to check the difference in wear behavior when materials surfaces were attacked by hard, loose particles in wet environment (pulp). Investigations were performed on silicon carbide, silicon nitride and two composites on their matrices. The basic performed test was the Miller Test according to ASTM Standard. The detail microstructural and mechanical characterization of investigated materials was done. Residual stress state caused by coefficients of thermal expansion mismatch was calculated using FEM approach. The second phases for composites were selected to introduce the compressive stress state into the matrix phase. Comparative studies of abrasive wear of “pure” phases and composites performed showed differences between dominating wear mechanisms. Tests results proved that the influence of the second phase presence in the materials was significant for the wear rate.展开更多
Novel bioactive injectable composites based on biopolymeric hydrogels reinforced with insulin-functionalized silica particles were synthesized.The insulin(INS)was immobilized on the surface of amine-modifed silica par...Novel bioactive injectable composites based on biopolymeric hydrogels reinforced with insulin-functionalized silica particles were synthesized.The insulin(INS)was immobilized on the surface of amine-modifed silica particles employing covalent attachment by EDC/NHS chemistry and via electrostatic interaction.The resulting formulations were examined for the morphology(SEM),chemical composition(FTIR,XPS)as well as protein content.To facilitate the injectability and support the bone regeneration,developed particles were dispersed in biopolymeric sol composed of collagen,chitosan and lysinemodifed hyaluronic acid and crosslinked with genipin.By means of rheological study,the sol-gel in situ transition of obtained systems was verifed.It was found in vitro study that MG-63 cells cultured on the developed composites exhibit signifcantly higher alkaline phosphatase(ALP)activity,compared to the pristine hydrogel.Furthermore,the biomineralization ability in the simulated body fluid(SBF)model was also demonstrated.Our fndings suggest that proposed herein novel hydrogel-based composites might be the promising formulation for regeneration of bone defects,especially as a less-cost effective support/alternative for BMP-2 systems.展开更多
The objective of this article is to uncover benefits and risks of Integrated Product Service Offering （IPSO） in a systematic manner. To do so, it adopts an explorative longitudinal in-depth case study （development ...The objective of this article is to uncover benefits and risks of Integrated Product Service Offering （IPSO） in a systematic manner. To do so, it adopts an explorative longitudinal in-depth case study （development of an IPSO based on a new technology） and adds insights to the existing literature. The article first proposes a theoretical and generic framework termed the PCP （Provider - Customer - Product） triangle with associated information flow and uncertainty. Second, various types of benefits and risks are presented based on the framework. Among others, the benefit of keeping IPR （Intellectual Property Rights） with the provider and the risk of regulation change are new findings from the case study. In addition, the case study reveals that IPSO is regarded as a positive contributor to innovation. Applying the framework and classification of benefits and risks as norms to other cases has yet to be done for verification. However, the framework contributes scientifically to a better understanding of the benefits and risks of IPSO. In addition, this framework is advantageous with its easiness to understand, which contributes practically to the dissemination of IPS0 insight to industry.展开更多
Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new ca...Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the environment.In addition,automotive brakes emit airborne particles.Some of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental impacts.In this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure.The two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake rotor.The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs.Meanwhile,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material.The LC disc yields a similar wear rate as the GCI disc.The ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake shapes.The HVOF disc emits unique needle-shaped particles.In the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state.Meanwhile,the LC disc emitted particles that are primarily~200 nm in the entire test run.展开更多
基金supported by the National Natural Science Foundation of China [No. 51475321]Tianjin Research Program of Application Foundation and Advanced Technology [No. 15JCZDJC38900 and 16JCYBJC19300]the International Postdoctoral Exchange Fellowship Program [No. 32 Document of OCPC, 2017]
文摘This paper deals with geometric error modeling and sensitivity analysis of an overconstrained parallel tracking mechanism. The main contribution is the consideration of overconstrained features that are usually ignored in previous research. The reciprocal property between a motion and a force is applied to tackle this problem in the framework of the screw theory. First of all, a nominal kinematic model of the parallel tracking mechanism is formulated. On this basis, the actual twist of the moving platform is computed through the superposition of the joint twist and geometric errors. The actuation and constrained wrenches of each limb are applied to exclude the joint displacement. After eliminating repeated errors brought by the multiplication of wrenches, a geometric error model of the parallel tracking mechanism is built. Furthermore,two sensitivity indices are defined to select essential geometric errors for future kinematic calibration. Finally, the geometric error model with minimum geometric errors is verified by simulation with SolidWorks software. Two typical poses of the parallel tracking mechanism are selected, and the differences between simulation and calculation results are very small. The results confirm the correctness and accuracy of the geometric error modeling method for over-constrained parallel mechanisms.
基金Project(50075017) supported by the National Natural Sceince Foundation of China
文摘The lifetime of metal rubber isolator and its characteristics during lifetime experiment were studied. The stepped-up test principle was adopted to study the lifetime of resonant frequency, the breakage form of metal rubber isolator was obtained, and the relation between the energy dissipation, resonant frequency and stiffness was obtained in (available) lifetime of the isolator. Furthermore, the reason for the changes of properties of metal rubber isolator was analyzed with contact model of metal rubber material. The results show that if the resonant amplitude is large, the stiffness of metal rubber isolator will be kept steadily for a long time, its resonant frequency will be stable and the effective working time in the protecting area will be long. The lifetime of metal rubber isolator is more than 1376 h in the experiment. The main failure forms of metal rubber isolator are accumulative wear and breaking of metal wires and spirals. In protecting area the metal rubber isolator can work effectively for a long time, and the effective working time depends on the concrete working condition.
基金The work was financially supported by the Polish State National Centre for Research and Development under Programme INNOTECH-K2/IN2/16/181920/NCBR/13.
文摘Silicon carbide and silicon nitride are recognized as phases with very good mechanical properties. Many parts of machines and mechanical devices are made of these materials. Particulate composites basing on both mentioned phases have significant potential of properties improvement. The aim of presented work was to check the difference in wear behavior when materials surfaces were attacked by hard, loose particles in wet environment (pulp). Investigations were performed on silicon carbide, silicon nitride and two composites on their matrices. The basic performed test was the Miller Test according to ASTM Standard. The detail microstructural and mechanical characterization of investigated materials was done. Residual stress state caused by coefficients of thermal expansion mismatch was calculated using FEM approach. The second phases for composites were selected to introduce the compressive stress state into the matrix phase. Comparative studies of abrasive wear of “pure” phases and composites performed showed differences between dominating wear mechanisms. Tests results proved that the influence of the second phase presence in the materials was significant for the wear rate.
基金the financial support of National Science Centre,Poland,Grant 2016/21/D/ST5/01635。
文摘Novel bioactive injectable composites based on biopolymeric hydrogels reinforced with insulin-functionalized silica particles were synthesized.The insulin(INS)was immobilized on the surface of amine-modifed silica particles employing covalent attachment by EDC/NHS chemistry and via electrostatic interaction.The resulting formulations were examined for the morphology(SEM),chemical composition(FTIR,XPS)as well as protein content.To facilitate the injectability and support the bone regeneration,developed particles were dispersed in biopolymeric sol composed of collagen,chitosan and lysinemodifed hyaluronic acid and crosslinked with genipin.By means of rheological study,the sol-gel in situ transition of obtained systems was verifed.It was found in vitro study that MG-63 cells cultured on the developed composites exhibit signifcantly higher alkaline phosphatase(ALP)activity,compared to the pristine hydrogel.Furthermore,the biomineralization ability in the simulated body fluid(SBF)model was also demonstrated.Our fndings suggest that proposed herein novel hydrogel-based composites might be the promising formulation for regeneration of bone defects,especially as a less-cost effective support/alternative for BMP-2 systems.
基金supported by the project Management of Innovation Processes for Business Driven Networksfunded by VINNOVA(The Swedish Governmental Agency for Innovation Systems)
文摘The objective of this article is to uncover benefits and risks of Integrated Product Service Offering （IPSO） in a systematic manner. To do so, it adopts an explorative longitudinal in-depth case study （development of an IPSO based on a new technology） and adds insights to the existing literature. The article first proposes a theoretical and generic framework termed the PCP （Provider - Customer - Product） triangle with associated information flow and uncertainty. Second, various types of benefits and risks are presented based on the framework. Among others, the benefit of keeping IPR （Intellectual Property Rights） with the provider and the risk of regulation change are new findings from the case study. In addition, the case study reveals that IPSO is regarded as a positive contributor to innovation. Applying the framework and classification of benefits and risks as norms to other cases has yet to be done for verification. However, the framework contributes scientifically to a better understanding of the benefits and risks of IPSO. In addition, this framework is advantageous with its easiness to understand, which contributes practically to the dissemination of IPS0 insight to industry.
基金The authors are grateful for the financial support from FORMAS:Swedish Research Council for Sustainable Development(No.2020-02302)(Nescup project)The research also received funding from European Union's Horizon 2020 research and innovation programme(No.954377)(nPETS project).
文摘Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the environment.In addition,automotive brakes emit airborne particles.Some of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental impacts.In this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure.The two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake rotor.The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs.Meanwhile,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material.The LC disc yields a similar wear rate as the GCI disc.The ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake shapes.The HVOF disc emits unique needle-shaped particles.In the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state.Meanwhile,the LC disc emitted particles that are primarily~200 nm in the entire test run.
