Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some ...Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.展开更多
Recent anomalies observed in e^(+)e^(-)nuclear transitions of,^(8)Be,^(4)He,and^(12)C by the ATOMKI collaboration may hint at the existence of a vector boson with a mass around 17 MeV,which is referred to as X17.If it...Recent anomalies observed in e^(+)e^(-)nuclear transitions of,^(8)Be,^(4)He,and^(12)C by the ATOMKI collaboration may hint at the existence of a vector boson with a mass around 17 MeV,which is referred to as X17.If it exists,this boson would affect similar processes in particle physics,including the Dalitz decays of vector mesons.Recently,the BESIII collaboration measured the Dalitz decay D^(*0)→D^(0)e^(+)e^(-)for the first time and reported a excess over the theoretical prediction based on the vector meson dominance(VMD)model.This excess may be another signal of X17.In this study,we investigate the possible effects of X17 on the Dalitz decays,D_(s)^(*)→D_(s)e^(+)e^(-),B_(s)^(*)→B_(s)e^(+)e^(-),and J/ψ→η_(c)e^(+)e^(-).The required hadronic form factors are calculated within the framework of our covariant confined quark model without relying on heavy quark effective theory or the VMD model.We present predictions for the Dalitz decay widths and the ratios R_(ee)(V)≡Γ(V→Pe^(+)e^(-))/Γ(V→Pγ)within the standard model and in several new physics scenarios involving modifications attributed to X17.Our results are compared with other theoretical calculations.展开更多
We justify and extend the standard model of elementary particle physics by generalizing the theory of relativity and quantum mechanics. The usual assumption that space and time are continuous implies, indeed, that it ...We justify and extend the standard model of elementary particle physics by generalizing the theory of relativity and quantum mechanics. The usual assumption that space and time are continuous implies, indeed, that it should be possible to measure arbitrarily small intervals of space and time, but we ignore if that is true or not. It is thus more realistic to consider an extremely small “quantum of length” of yet unknown value <em>a</em>. It is only required to be a universal constant for all inertial frames, like<em> c</em> and <em>h</em>. This yields a logically consistent theory and accounts for elementary particles by means of four new quantum numbers. They define “particle states” in terms of modulations of wave functions at the smallest possible scale in space-time. The resulting classification of elementary particles accounts also for dark matter. Antiparticles are redefined, without needing negative energy states and recently observed “anomalies” can be explained.展开更多
Forging is state-of-the-art for producing hand tools on an industrial scale.Due to high demands on the stiffness and the fracture toughness,high-strength forging steels were used to provide cavity-free components with...Forging is state-of-the-art for producing hand tools on an industrial scale.Due to high demands on the stiffness and the fracture toughness,high-strength forging steels were used to provide cavity-free components with high mechanical load capacity.Moreover,forging is a cost-effective mass production process but,in spite of all its advantages,it has its limitations,e.g.in the freedom of designs.However,because of the extreme thermal loading(particularly with regard to permanent moulds) and the frequently unavoidable casting defects,hand tools are not cast.By means of thixocasting steel,technical difficulties can be reduced and new options are provided which allow the manufacturing of components with much higher complexity than that using forging.Through near-net shape production,manufacturing steps and costs can be reduced.Furthermore,steels,which are difficult to forge but nonetheless have high potential for specific applications(such as high strength or corrosion resistant steels),can also be processed.In cooperation with industrial partners,X39CrMo17 stainless steel combination spanners with 17 mm width across flats were thixocast.Forming dies were designed and optimized by simulation,the hot forming X38CrMoV5 tool steel as well as the molybdenum alloy TZM were selected as the tool alloys.The dies were treated by a plasma nitriding process and subsequently coated with crystalline Al2O3 protective coatings by plasma-enhanced chemical vapor deposition(PECVD).During the experiments,combination spanners were successfully cast in the semi-solid state.Cast parts were heat-treated to enhance the toughness of components,which was subsequently measured by a standardized torque test.Moreover,a hypothetical approach of a possible,industrial batch process was carried out using the simulation software MAGMAsoft.展开更多
文摘Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.
基金Supported by Ho Chi Minh City University of Technology and Education(T2024-65)。
文摘Recent anomalies observed in e^(+)e^(-)nuclear transitions of,^(8)Be,^(4)He,and^(12)C by the ATOMKI collaboration may hint at the existence of a vector boson with a mass around 17 MeV,which is referred to as X17.If it exists,this boson would affect similar processes in particle physics,including the Dalitz decays of vector mesons.Recently,the BESIII collaboration measured the Dalitz decay D^(*0)→D^(0)e^(+)e^(-)for the first time and reported a excess over the theoretical prediction based on the vector meson dominance(VMD)model.This excess may be another signal of X17.In this study,we investigate the possible effects of X17 on the Dalitz decays,D_(s)^(*)→D_(s)e^(+)e^(-),B_(s)^(*)→B_(s)e^(+)e^(-),and J/ψ→η_(c)e^(+)e^(-).The required hadronic form factors are calculated within the framework of our covariant confined quark model without relying on heavy quark effective theory or the VMD model.We present predictions for the Dalitz decay widths and the ratios R_(ee)(V)≡Γ(V→Pe^(+)e^(-))/Γ(V→Pγ)within the standard model and in several new physics scenarios involving modifications attributed to X17.Our results are compared with other theoretical calculations.
文摘We justify and extend the standard model of elementary particle physics by generalizing the theory of relativity and quantum mechanics. The usual assumption that space and time are continuous implies, indeed, that it should be possible to measure arbitrarily small intervals of space and time, but we ignore if that is true or not. It is thus more realistic to consider an extremely small “quantum of length” of yet unknown value <em>a</em>. It is only required to be a universal constant for all inertial frames, like<em> c</em> and <em>h</em>. This yields a logically consistent theory and accounts for elementary particles by means of four new quantum numbers. They define “particle states” in terms of modulations of wave functions at the smallest possible scale in space-time. The resulting classification of elementary particles accounts also for dark matter. Antiparticles are redefined, without needing negative energy states and recently observed “anomalies” can be explained.
基金the German Research Foundation (DFG),which supports this work within the framework of the collaborative research centre SFB 289
文摘Forging is state-of-the-art for producing hand tools on an industrial scale.Due to high demands on the stiffness and the fracture toughness,high-strength forging steels were used to provide cavity-free components with high mechanical load capacity.Moreover,forging is a cost-effective mass production process but,in spite of all its advantages,it has its limitations,e.g.in the freedom of designs.However,because of the extreme thermal loading(particularly with regard to permanent moulds) and the frequently unavoidable casting defects,hand tools are not cast.By means of thixocasting steel,technical difficulties can be reduced and new options are provided which allow the manufacturing of components with much higher complexity than that using forging.Through near-net shape production,manufacturing steps and costs can be reduced.Furthermore,steels,which are difficult to forge but nonetheless have high potential for specific applications(such as high strength or corrosion resistant steels),can also be processed.In cooperation with industrial partners,X39CrMo17 stainless steel combination spanners with 17 mm width across flats were thixocast.Forming dies were designed and optimized by simulation,the hot forming X38CrMoV5 tool steel as well as the molybdenum alloy TZM were selected as the tool alloys.The dies were treated by a plasma nitriding process and subsequently coated with crystalline Al2O3 protective coatings by plasma-enhanced chemical vapor deposition(PECVD).During the experiments,combination spanners were successfully cast in the semi-solid state.Cast parts were heat-treated to enhance the toughness of components,which was subsequently measured by a standardized torque test.Moreover,a hypothetical approach of a possible,industrial batch process was carried out using the simulation software MAGMAsoft.
