Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved b...Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power （P）, scanning speed （Vs）, wire feed rate （Vf）, and wire current （/）, were optimized based on the analysis of signal-to-noise （S/N） ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.展开更多
Creating sustainable cities is the only way to live in a clean environment,and this problem can be solved by using bio-sourced and recycled materials.For this purpose,the authors contribute to the valuation of sheep w...Creating sustainable cities is the only way to live in a clean environment,and this problem can be solved by using bio-sourced and recycled materials.For this purpose,the authors contribute to the valuation of sheep wool waste as an eco-friendly material to be used in insulation.The paper investigates the thermal,hygrothermal,and biological aspects of sheep wool by testing a traditional treatment.The biological method of aerobic mesophilicflora has been applied.Fluorescence X was used to determine the chemical composition of the materials used.Also,thermal characterization has been conducted.The thermal conductivity is above 0.046(W·m^(-1)·K^(-1))and the thermal diffusivity is 1.56.10^(-6) m^(2)·s^(-1).Besides,the energy efficiency of using sheep wool in buildings was studied.Furthermore,its humidity behavior was evaluated in different aspects in both winter and summer.Results of biological analyses show the efficiency of the treatment by removing the majority of the microorgan-isms:the value of yeast and mildew was reduced from 38.10^(2) to 2.10^(2)(UFC·g^(-1)).In addition to that,sheep wool permits obtaining a low thermal transmittance on the scale of the walls and low cooling needs on the scale of the building with a gain of 45%and 52%,respectively.展开更多
In this paper,a new measurement technique for determining thermal conductivity of semitransparent media in the temperature range 300-800 K is reported.The experimental setup is based on the step power forced transient...In this paper,a new measurement technique for determining thermal conductivity of semitransparent media in the temperature range 300-800 K is reported.The experimental setup is based on the step power forced transient hot wire technique.It is assumed that the radiative contribution to the heat transfer process arises from emission,not from absorption.In this case,application of the'thermal quadruples'method allows a very simple construction of analytical models of the experimental setup.The parameter sensitivity analysis demonstrates that the thermal conductivity of semitransparent media can be determined from the hot wire temperature response. The experimental results of a kind of glass between 300 and 800 K are presented.展开更多
The paper reports the measurements of the thermal conductivity of gaseous HFC32 over the temperature range 254.51K to 341.76K near the saturation line. The thermal conductivities were measured in a transient hot-wire ...The paper reports the measurements of the thermal conductivity of gaseous HFC32 over the temperature range 254.51K to 341.76K near the saturation line. The thermal conductivities were measured in a transient hot-wire instrument employing two anodized tantalum wires as the heat source with an uncertainty of 1%. The resuilts were correlated as a function of temperature for engineering use.展开更多
文摘Laser hot wire cladding, with the prominent features of low heat input, high energy efficiency, and high precision, is widely used for remanufacturing metal parts. The cladding process, however, needs to be improved by using a quantitative method. In this work, volumetric defect ratio was proposed as the criterion to describe the integrity of forming quality for cladding layers. Laser deposition experiments with FV520B, one of martensitic stainless steels, were designed by using the Taguchi method. Four process variables, namely, laser power （P）, scanning speed （Vs）, wire feed rate （Vf）, and wire current （/）, were optimized based on the analysis of signal-to-noise （S/N） ratio. Metallurgic observation of cladding layer was conducted to compare the forming quality and to validate the analysis method. A stable and continuous process with the optimum parameter combination produced uniform microstructure with minimal defects and cracks, which resulted in a good metallurgical bonding interface.
文摘Creating sustainable cities is the only way to live in a clean environment,and this problem can be solved by using bio-sourced and recycled materials.For this purpose,the authors contribute to the valuation of sheep wool waste as an eco-friendly material to be used in insulation.The paper investigates the thermal,hygrothermal,and biological aspects of sheep wool by testing a traditional treatment.The biological method of aerobic mesophilicflora has been applied.Fluorescence X was used to determine the chemical composition of the materials used.Also,thermal characterization has been conducted.The thermal conductivity is above 0.046(W·m^(-1)·K^(-1))and the thermal diffusivity is 1.56.10^(-6) m^(2)·s^(-1).Besides,the energy efficiency of using sheep wool in buildings was studied.Furthermore,its humidity behavior was evaluated in different aspects in both winter and summer.Results of biological analyses show the efficiency of the treatment by removing the majority of the microorgan-isms:the value of yeast and mildew was reduced from 38.10^(2) to 2.10^(2)(UFC·g^(-1)).In addition to that,sheep wool permits obtaining a low thermal transmittance on the scale of the walls and low cooling needs on the scale of the building with a gain of 45%and 52%,respectively.
文摘In this paper,a new measurement technique for determining thermal conductivity of semitransparent media in the temperature range 300-800 K is reported.The experimental setup is based on the step power forced transient hot wire technique.It is assumed that the radiative contribution to the heat transfer process arises from emission,not from absorption.In this case,application of the'thermal quadruples'method allows a very simple construction of analytical models of the experimental setup.The parameter sensitivity analysis demonstrates that the thermal conductivity of semitransparent media can be determined from the hot wire temperature response. The experimental results of a kind of glass between 300 and 800 K are presented.
文摘The paper reports the measurements of the thermal conductivity of gaseous HFC32 over the temperature range 254.51K to 341.76K near the saturation line. The thermal conductivities were measured in a transient hot-wire instrument employing two anodized tantalum wires as the heat source with an uncertainty of 1%. The resuilts were correlated as a function of temperature for engineering use.
