Influence of laser process parameters on the characteristic of 30CrMnSiA steel substrate and adhesively bonded joints

The effect of laser process parameters including single pulse energy (E), dimples per square millimetre (D) and laser incidence angle (0) on the properties of 30CrMnSiA steel substrate and the tensile shear strength of adhesively bonded joints was investigated. The characterization of the substrate was established by surface morphology, the dimension (diameter and depth) of dimples and surface roughness (Ra and Rz). Single lap joints were fabricated and tensile tests were then performed. The fracture surfaces were observed and analyzed. The results indicated that the dimple dimension and surface roughness increased as the single pulse energy increased. The increase of dimples per square millimetre made surface roughness improve. The larger incidence angle reduced the actually absorbed energy changing the shape and size of dimples. The diameter of dimples increased while the depth decreased as incidence angle increased. The modified substrate morphology as well as increased dimple dimension expanded the contact area between the adhesive and adherend. The shear strength was enhanced and the maximum value was 24.67 MPa increasing by 363% compared to the adhesive joints without surface treatment. The mechanical interlocking between the adhesive and laser textured morphology was discovered in the fracture surface demonstrating the improvement of shear strength.