OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 4 No. 4 2022 As a widely used shaping method, grinding requires machining with a tool, the condition of which will ensure proper product quality. Dressing is used to return the original properties to the grinding wheel (GW). This also needs to be well timed for technological and economic reasons. TCM is the most effective tool to determine this moment. It is also performed at the end of the process chain, followed by finishing. Methods which do not require suspension of the production process, in order to determine wear parameters, i.e. indirect methods, are of interest among many approaches to determine GW condition. Acoustic methods (acoustic emission and noise diagnostics as per GOST 23829–85) are both indirect and passive methods, meaning that there is no external source of energy affecting the object of study. Many studies have focused on determining and predicting GW condition during processing through the use of acoustic emission signals [2]. It is shown that this method has a sufficiently high level of accuracy, information content [3], and sensitivity [4, 5] aimed at establishing current tool performance. However, this method is not common due to the high cost of equipment, and the need for specific signal transformations to filter it [6], etc. Furthermore, the method directly involving the acoustic wave generated by GW vibrations during processing (noise diagnostic) has been studied much less, despite its comparable practical potential [7]. Most of the main types of machining operations have been studied using acoustic methods (both acoustic emission and noise diagnostics): turning [8, 9]; milling [10]; micromilling [11]; drilling [12]; and grinding [13, 14]. All kinds of machined materials – brittle [15], ductile, composites [16], wood [17], have been considered. The studies have shown the applicability of the method for a wide range of process conditions of various machining operations aimed at determining the various parameters of the object to be studied. According to the majority of the authors of the works herein presented, the main aim of this method is to monitor cutting tool wear parameters. Researchers agree that acoustic monitoring methods are essential for practical application, in order to increase the process efficiency. Despite all the advantages of acoustic monitoring methods and its wide use in various types of processing, determining GW condition by this method in profile grinding has not yet found extensive application. Profile grinding is used for finishing complex shape surfaces and involves the processing of a workpiece with a grinding wheel with a pre-shaped profile. The aim is to ensure the required dimensions, shape, and surface quality (Fig. 1). The significance of the method lies in the high degree of responsibility connected with the production of the profiled parts. Surveys show that despite the high demand for profile grinding in mechanical engineering, the acoustic phenomena of this process have been poorly studied. Nevertheless, there is a demand for determination of the current cutting capacity of the profiled GW and predicting its durability period [18, 19, 20]. A deeper insight into this issue will allow rationalizing the consumption of cutting tools and increasing the efficiency of profile grinding in digital production. An acoustic method for TCM in profile grinding needs to be developed. This is also connected with the need for expedient profile tool dressing in this type of processing, as well as in other types of grinding. The purpose of this research is to establish the acoustic parameters of flat grinding with a profile wheel as it wears out, as opposed to a similar process using a straight profile wheel. The tasks to be solved to achieve this purpose are listed below. Since the sound pressure generated by grinding results from the natural vibrations of the wheel [21], it is necessary to study the natural vibration frequencies (NVF) of grinding wheels of various profiles. Fig. 1. Profile grinding of bearing rings: a – external; b – internal
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