PSI - Issue 39

Szymon Derda et al. / Procedia Structural Integrity 39 (2022) 441–449 Author name / Structural Integrity Procedia 00 (2019) 000–000

445

5

Table 3 Dimensions of specimens for fatigue testing [mm]

W 2

R

T*

T St *

T Cu *

L1

L2 90 90

W 1

Case 1 Case 2

29,87 29,87

6 6

3 3

20 20

4.22-4.58 6.32-6.61

1.40-1.57 1.42-1.51 1.51-1.65 3.18-3.34

* range of measured values

3. Calculations As the tests were carried out in a force-controlled manner for easier comparison a simple analytical model was used to assess maximum stress in each particular composite layer. Several assumptions and approximations had to be made, such as uniform stress distribution, uniaxial state of stress, elastic strain range, continuous and flat surface of the interface. The basic force equilibrium equation was transformed in regard to a layer of interest. Since most cracks appeared in the Tantalum layer the here presented results were introduced as shown in � � � � � � �� � � � � (1) 4. Results Results of fatigue tests were summarized in Tables 4 and 5 which contain the maximum stress in a particular layer, fatigue life in cycles, and location of the primary crack initiation site.

Table 4 Results of fatigue testing for Case 1

Specimen σ Ta , MPa

σ Cu , MPa

σ Steel , MPa

N

exp , cycles

Crack Initiation

F01

325

219

330

1 062 000

Ta

F02

356

239

361

258 367

Ta

F03

370

250

376

244 364

Ta

F04

388

261

394

210 516

Ta

F05

398

268

405

194 929

Ta

F06

437

295

444

43 477

Not identified

F09

415

280

422

108 933

Ta

F13

334

225

339

411 627

Ta

F14

329

222

334

528 343

Ta