11 октября, 2015 
Pokraskin As explained in the Introduction Section, the aim of the research was to study the effect of the ER on joint performance. Thus, the first step has consisted in the determination of the most suitable range of the ER to be investigated. The Standard ISO 10123 [13], specific for pin-collar specimens, suggests a sample geometry corresponding to ER=0.9. Based on this remark, it
seemed to be reasonable to focus the study on ERs varying from 0.4 to 1.7, i. e., from approximately one half to the double of the reference value. For statistical evidence reasons, four levels have been considered in the aforementioned range, adding the intermediate values of 0.8, very close to that recommended by the Standard [13], and 1.3.
The second step consisted in the design of the shaft and hub specimens to be connected by interference and adhesive (press-fitted and adhesively bonded samples, HJs). For the sake of the consistency of results, when comparing the responses of HJs to those of pin-collar samples, it seemed to be reasonable not to divert so far from the recommended proportioning in [13]. However, since Ref. [13] is originally intended for slip fit, pin-collar joints, some modifications had to be introduced, to obtain interference at the shaft-hub coupling. Therefore, the external diameter of the pin was slightly increased, whereas the internal bushing diameter was reduced. All the other dimensions, such as the external diameter and the axial length, remained unchanged with respect to the values recommended in [13]. Following this strategy prevented any unexpected effect, due to a different proportioning of the specimen.
The following point consisted in managing the four values of ER to be obtained. Considering a longitudinal extension of 11.1mm, the resulting ER is 0.8, a bit lower than the recommended one, due to the rearranged diametric dimension. The longitudinal length was modified in order to design hubs with different ERs: half length was considered for the lowest level (ER=0.4), while 50% and 100% increased dimensions were used for the two top values (ER=1.3, 1.7). The other dimensions remained unchanged to get a consistency of the results for different ERs. The drawings of specimens for the four different levels of ER are shown in Figure 1 (a, b, c, d), while the pin is sketched in Figure 1 (e): nominal interference is within the interval from 20pm and 30pm, corresponding to an ISO H7/s6 coupling [15]. For reasons of statistical evidence ten pieces were manufactured for each hub type (40 hubs as a total), along with 40 shafts.
Опубликовано в рубрике 