This paper describes a preliminary method for the classification of annealed and unannealed polyetherketoneketone (PEKK) components manufactured using a material extrusion three-dimensional (3D) printing process. PEKK is representative of a class of high-performance thermoplastics that are increasingly employed as feedstocks for use in 3D printing. PEKK components may be used continuously at elevated temperatures, are chemically resistant, and able to withstand large mechanical loads. These properties render PEKK suitable as a metal component replacement in aerospace applications, high-temperature industrial applications, and surgical implants. The structure of PEKK is semi-crystalline with the specific crystallinity correlating to the final properties during application, making determination of this property crucial. This study compares three different signal processing techniques intended to distinguish annealed (high crystallinity) from unannealed (low crystallinity) components using backscattered ultrasound. The first is energy-based and is unable to detect annealing. The second two are based on different entropies of the backscattered signal: a limiting form of Renyi's entropy and a limiting form of joint entropy. The joint entropy values for the annealed and unannealed specimens fall into two non-overlapping intervals and have a statistical separation of two standard deviations.

中文翻译：

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熵和信号能量在基于超声的三维印刷聚醚酮酮组分分类中的应用。

本文介绍了一种初步方法，用于对使用材料挤出三维（3D）印刷工艺制造的退火和未退火的聚醚酮酮（PEKK）组件进行分类。PEKK是一类高性能热塑性塑料的代表，这些热塑性塑料越来越多地用作3D打印的原料。PEKK组件可在高温下连续使用，耐化学腐蚀并能够承受较大的机械负载。这些特性使PEKK适合用作航空航天应用，高温工业应用和外科植入物中的金属部件替代品。PEKK的结构是半结晶的，其特定的结晶度与施工过程中的最终性能相关，因此确定该性能至关重要。这项研究比较了三种不同的信号处理技术，这些技术旨在使用反向散射超声来区分退火（高结晶度）与未退火（低结晶度）组件。第一种是基于能量的，无法检测到退火。后两者基于反向散射信号的不同熵：Renyi熵的限制形式和联合熵的限制形式。退火和未退火样品的联合熵值分为两个不重叠的间隔，并且具有两个标准偏差的统计间隔。后两者基于反向散射信号的不同熵：Renyi熵的限制形式和联合熵的限制形式。退火和未退火样品的联合熵值分为两个不重叠的间隔，并且具有两个标准偏差的统计间隔。后两者基于反向散射信号的不同熵：Renyi熵的限制形式和联合熵的限制形式。退火和未退火样品的联合熵值分为两个不重叠的间隔，并且具有两个标准偏差的统计间隔。