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16 results on '"Yang, Zhengheng"'

11. Numerical Study on the Heating Effect of a Spring-Loaded Actuator—Part Ⅰ: Temperature and Humidity Distribution Characteristics.

Author

Xi, Lei, Zhao, Zhen, Ruan, Qicheng, Yang, Zhengheng, Xu, Liang, Gao, Jianmin, and Li, Yunlong

Subjects
TEMPERATURE distribution, ACTUATORS, AIR flow, ATMOSPHERIC temperature, HUMIDITY
Abstract

Inappropriate distributions of temperature and humidity will cause the failure of the spring-loaded actuators. Therefore, it is essential to understand the temperature and humidity distribution characteristics in typical spring-loaded actuators, to guarantee the safe operation of the spring-loaded actuators. In this work, a numerical simulation study on the temperature and humidity distribution characteristics in a spring-loaded actuator was conducted. The influence laws of ambient temperature, heater power, and heater size on the temperature and humidity distributions inside the spring-loaded actuator were analyzed. The practical empirical correlations for the spring-loaded actuators were fitted. The results show that the air temperature around and directly above the heater is the highest and the corresponding relative humidity is the lowest. Then, the air temperature gradually decreases, and the relative humidity increases with the lateral flow of air. When the ambient temperature increases from 233.15 K (−40 °C) to 313.15 K (40 °C), the minimum temperature inside the actuator is increased by 34%, the maximum humidity first increases and then decreases, and the maximum temperature on the heater surface is increased by 30%. When the heating power increases from 10 W to 150 W at ambient temperatures of 273.15 K and 298.15 K, the minimum temperature inside the actuator is increased by 3.40% and 3.61%, the maximum humidity is decreased by 51.97% and 58.63%, and the maximum temperature on the heater surface is increased by 30.33% and 33.25%, respectively. The influence of heater length, width, and height on the minimum temperature and maximum relative humidity inside the spring-loaded actuator is relatively small. Within the study range, the increase in heater length, width, and height makes the maximum temperature on the heater surface decrease by 9.15%, 7.59%, 4.63% at ambient temperatures of 273.15 K, and 10.74%, 9.01%, 4.73% at ambient temperature of 298.15 K, respectively. The results may provide a reference for predicting temperature and humidity distributions inside general spring-loaded actuators and provide a calculation basis for the design of their heaters. [ABSTRACT FROM AUTHOR]

Published
2023
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15. Dissipative Structures and Superplasticity

Author

Jiwei Shi, Reginald W. Smith, Yang Zhengheng, and Hechun Chen

Subjects
Materials science, Classical mechanics, Deformation mechanism, Thermodynamic equilibrium, Dissipative system, Superplasticity, Deformation (engineering), Indeterminism, Instability, Determinism
Abstract

The characteristics of superplasticity are discussed from the viewpoint of irreversible thermodynamics, in particular, system evolution and the formation of dissipative structures. A mathematical model combining determinism with indeterminism is used to analyze plastic deformation and superplasticity in metals. Since the plastic deformation of a metal is in essence a dissipative process occurring in a system far away from thermodynamic equilibrium, the instability of the system resulting from structure fluctuations (defects) and thermodynamic bifurcations (possible thermodynamic states) will result in many deformation mechanisms being available to provide the deformation observed in the system. Thus it is virtually impossible to describe all the possible models in conventional terms i.e. by the application of the method of determinism. A new model is proposed, and is shown to account for much of the experimental data reported.

Published
1990
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16. The equivalence between the free bulging process and the uniaxial tensile test

Author

Gong Yaofu, Gong Yiji, and Yang Zhengheng

Subjects
Materials science, business.industry, General Engineering, Uniaxial tension, Biaxial tensile test, Pneumatic pressure, Superplasticity, Structural engineering, Limiting, Stress (mechanics), Composite material, business, Equivalence (measure theory), Tensile testing
Abstract

Bulge forming, in which the material undergoes biaxial tensile stress, is the most widely applied superplastic forming method, whilst the uniaxial tensile test, in which the material undergoes only uniaxial tensile stress, is the most common material test-method. The superplastic parameters of the material as measured in the uniaxial tensile test cannot be used to establish the technological parameters for pneumatic bulge forming — for instance, the optimal variation in the pneumatic pressure during the process and the limit to which forming can be carried out — due to the differences in the two stress states. In this paper, the equivalent relationships between pneumatic bulge forming and the uniaxial tensile test are determined, from which relationships the limiting ratio of the current area to the original area of the component can be established. The experimental results in this paper show that theory and practice are in very good agreement.

Published
1988
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