Table 3. Database search strings.
| Searching texts/search strings | Web of Science | Scopus | IEEE Xplore | Medline complete | Emerald | Springer link | Dimensions | Science direct |
|---|---|---|---|---|---|---|---|---|
| ((“Equipment*” OR “machine*”) AND (“maintenance*” OR “smart maintenance*”) AND (“predict*”) AND (“digital twin*” OR “virtual model*”)) | 188 | 371 | 409 | 736 | 2,000 | None | 83 | None |
| Equipment AND maintenance AND predictive AND digital twin | 53 | 106 | 107 | 864 | 247 | 7,907 | 111 | 4,336 |
| Machine AND smart maintenance AND predictive AND virtual model | 10 | 8 | 28 | 1,269 | 649 | 13,917 | 14 | 7,713 |
| Equipment AND smart maintenance AND predictive AND virtual model | 5 | 5 | 11 | 1,023 | 498 | 11,889 | 8 | 6,326 |
| Machine AND maintenance AND predictive AND digital twin | 120 | 200 | 187 | 963 | 295 | 8,803 | 200 | 4,923 |
| Predictive maintenance AND digital twin | 302 | 511 | 397 | 1,543 | 287 | 10,079 | 521 | 7,249 |
| Total number of duplicates | 490 | 830 | 730 | 5,662 | 1,976 | 52,595 | 854 | 30,547 |
| Subtotals containing duplicates | 93,684 | |||||||
| Total selected articles | 34 | |||||||