求翻译：利用超声波来评价金属材料的晶粒尺寸,与传统的金相法测量相比较，特点是直接性和非破坏性,具有很强的实用性。本文综述了超声波无损评价金属材料晶粒尺寸各方法的原理和研究现状，最后，结合超声无损检测（评价）技术的应用需求及研究现状中的不足，对超声波无损评价金属材料晶粒度方法的设计方案的优化作了展望是什么意思？

Compared to the use of ultrasound to evaluate the grain size of the metal material, measured with conventional metallographic method is characterized by the direct and non-destructive, and highly practical. In this paper, the principle of ultrasonic nondestructive evaluation of metallic materials gr

Use of ultrasound to evaluate metal die size, with the traditional Kim Sang-law compared measurements, characterized by direct and non-destructive, with a very strong sense of practicality. This article provides an overview of ultrasonic non-destructive Evaluation methods of metal die sizes the theo

Appraises the metal material using the ultrasonic wave the crystal grain size, compares with the traditional metallography law survey, the characteristic is the substantivity and the non-destructiveness, has the very strong usability.This article summarized the ultrasonic wave lossless appraisal met

Use of ultrasound to evaluate the materials grain size, compared with traditional metallography measurement, is characterized by directness and non-destructive, highly practical. This article provides an overview of ultrasonic non-destructive evaluation method for grain size of metallic materials an

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