Research On Three-dimensional Measurement Of High-temperature Hot Objects

Forging industry is the basis of developing equipment manufacturing industry, especially for large forgings, whose dimensional precision is an important factor to ensure the manufacturing quality of major technical equipment. According to the survey of Department of Energy, rejection rate of forging industry in the United States is more than 15%, mainly due to the lack of measurement techniques about hot forgings, and this situation also exists in Chinese forging industry. The field measurement for hot forging parts to control the quality of forging process is needed, in order to effectively reduce forging rejection rate. As China's rapid development in energy and power, aerospace, nuclear power, high-speed trains, engineering chemistry and metallurgy, shipping and other fields, the demand for large forgings is growing, so is the economic significance of the research on field measurement techniques of high temperature objects. Connected with the related optical measurement research of the Eleventh Five-Year national defense pre-research item, this paper makes an exploratory study on measurement techniques of hot forgings, with a view to provide strong support for controlling the quality of forging process.After making research on the related techniques of measurement of hot forgings at home and abroad, this paper adopts the current structured light 3D measurement system and design the reasonable image acquisition scheme aiming at the characteristics that forgings in the produce process is accompanied by high temperature,high pressure and the airwaves existing in forging surface, on the basis of successfully finishing the intrinsic and extrinsic parameters calibration of measurement system. Then according to the characteristics of high temperature measurement, it makes analysis of phase error and chooses median filtering algorithm to make filtering preprocess of raster image, reducing the picture noises'influence on phase error, and chooses five-step phase-shifting method as phase computation of the system to reduce the influence of phase displacement error and system's nonlinear response on phase errors, and finally the whole measurement system measures the objects being measured under the situation of separately using five-step phase-shifting method and five-step phase-shifting method, and through the comparison of their three-dimensional data, the Five-step phase shift algorithm improving measurement precision of the system can be found.