Based on the Almen method, the authors have modified this test method so that the results of the simple test can be correlated to the absolute values of residual stress measured by conventional methods such as X-ray d...Based on the Almen method, the authors have modified this test method so that the results of the simple test can be correlated to the absolute values of residual stress measured by conventional methods such as X-ray diffraction, or mechanical techniques. The technique utilizes changes in the strain of standardized test substrates, which is measured by BHP-700℃ temperature-compensated resistance strain gauges, as an indication of the level of residual stress in the sprayed coatings. Based on the concept that the sprayed coating on the surface of substrate with residual stresses acts a force (N) and bending moment (M) on the test piece, the calculating equation of residual stress in the coatings has been proposed. The results of the test method showed that the technique is potentially reliable and accurate, although deficiencies and many controversies are still exist.展开更多
Using a modified 3D random representative volume（RV）finite element model,the effects of model dimensions（impact region and interval between impact and representative regions）,model shapes（rectangular,square,and c...Using a modified 3D random representative volume（RV）finite element model,the effects of model dimensions（impact region and interval between impact and representative regions）,model shapes（rectangular,square,and circular）,and peening-induced thermal softening on resultant critical quantities（residual stress,Almen intensity,coverage,and arc height）after shot peening are systematically examined.A new quantity,i.e.,the interval between impact and representative regions,is introduced and its optimal value is first determined to eliminate any boundary effect on shot peening results.Then,model dimensions are respectively assessed for all model shapes to reflect the actual shot peening process,based on which shape-independent critical shot peening quantities are obtained.Further,it is found that thermal softening of the target material due to shot peening leads to variances of the surface residual stress and arc height,demonstrating the necessity of considering the thermal effect in a constitutive material model of shot peeing.Our study clarifies some of the finite element modeling aspects and lays the ground for accurate modeling of the SP process.展开更多
文摘Based on the Almen method, the authors have modified this test method so that the results of the simple test can be correlated to the absolute values of residual stress measured by conventional methods such as X-ray diffraction, or mechanical techniques. The technique utilizes changes in the strain of standardized test substrates, which is measured by BHP-700℃ temperature-compensated resistance strain gauges, as an indication of the level of residual stress in the sprayed coatings. Based on the concept that the sprayed coating on the surface of substrate with residual stresses acts a force (N) and bending moment (M) on the test piece, the calculating equation of residual stress in the coatings has been proposed. The results of the test method showed that the technique is potentially reliable and accurate, although deficiencies and many controversies are still exist.
基金the financial support from China Scholarship Council (CSC) (No. 201406025083)National Natural Science Foundation of China (NSFC) (Nos. 51305012 and 51675024)+3 种基金Aviation Science Fund of China (No. 2014ZB51)financial support from NSFC (No. 51375031)financial support from NSFC (No. 51628101)National Sciences and Engineering Research Council (NSERC) Discovery grant (No. RGPIN 418469-2012)
文摘Using a modified 3D random representative volume（RV）finite element model,the effects of model dimensions（impact region and interval between impact and representative regions）,model shapes（rectangular,square,and circular）,and peening-induced thermal softening on resultant critical quantities（residual stress,Almen intensity,coverage,and arc height）after shot peening are systematically examined.A new quantity,i.e.,the interval between impact and representative regions,is introduced and its optimal value is first determined to eliminate any boundary effect on shot peening results.Then,model dimensions are respectively assessed for all model shapes to reflect the actual shot peening process,based on which shape-independent critical shot peening quantities are obtained.Further,it is found that thermal softening of the target material due to shot peening leads to variances of the surface residual stress and arc height,demonstrating the necessity of considering the thermal effect in a constitutive material model of shot peeing.Our study clarifies some of the finite element modeling aspects and lays the ground for accurate modeling of the SP process.
