One of the problems, which engineers face in using of carbon-reinforced composites, is the large scatter of the strength characteristics. To diminish scatter the method of the merger of tests results under varied climatic conditions might be applied. The aim of this merge is diminishing the scatter of the strength test results, and therefore improving the strength estimation accuracy. It is also in connection with the problem of the impact of climatic changes on the material properties. The climate impact is significantly larger in composites than in metals. To deal with those two problems the heredity mechanics developed earlier by Russian academician Ju. N. Rabotnov and his successors has been applied. The developed earlier modification of this theory, related to climate influence, has been applied to the problem of experimental data merger, obtained under varying temperatures, into one generalized set. For consideration of the orthotropy properties which are specific for reinforced composites, it was proposed the experimental investigation of the specimens cut in three different directions. The Rabotnov’s heredity equation should be written in tensor form. The property of viscoelasticity, which is inherent for carbo-plastics materials (especially under the elevated temperatures), is utilized in the decision of this problem. Experimental data and results of the model application are presented.
The Aim of the paper is to create a method for including information on censorship for the purpose of adjusting the estimates of the S-N diagram of composite materials. Censored items are such items that did not fail by the end of testing, for which a certain operation time has been registered. It must be noted that, currently, researchers often ignore the operation time data of the items that did not fail by the end of testing, which does not appear to be justified in terms of cost saving and reliability of statistical conclusions. Censorship information is very important in terms of assessing durability. It only needs the right tool to use it. The proposed Method consists in bootstrapping-based simulation, a method from the group of computer-intensive methods. In the process of the method’s development, the previously used approaches (for instance, as regards metals) were considered. In the examined example of the method’s application, the data was taken from literary sources. Results. The paper shows an example of fatigue testing conducted by the authors that produced a large number of censored items. The results obtained using the method were compared with real data. It is shown that the quality of statistical estimation improves with the use of the method. The paper sets forth certain observations regarding the mechanical testing tool for quality control. The source of data dispersion associated with fatigue testing is discussed. Conclusions. The application of the method will help include the information on censored items in the estimation of the S-N diagram. For scientists who are involved in the experimental research of the fatigue resistance of composite materials, the suggested method might prove to be quite useful. It takes into consideration the characteristic features of the strength analysis of composite materials (large properties dispersion and absence of unlimited fatigue range). The method will allow taking onto account an important, but not always so far used information on the items that operated a certain number of cycles, but did not fail.
According to the kanban (just in time) system, any production system needs continuous improvement. Possessing excellent mechanical properties, composite materials demonstrate a significant variation of properties (in particular, strength indicators). The composite manufacturing process is multi-stage and requires optimization after thoughtful consideration of the nuances. Exploratory data analysis was applied as a first step for this analysis. It serves as a basis for further experimental research, which it is desirable to carry out using the mathematical theory of experimental design. After the first stage of the study of the process, namely, the study of the statistical reproducibility of the technological process, in order to obtain more complete information about the process, it will be necessary to introduce additional influences on it.
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