Effect of One- and Two-Stage Shear Cutting on the Fatigue Strength of Truck Frame Parts

Abstract

The longitudinal and transverse beams of trucks are manufactured with a large number of holes to fasten brackets for springs, fuel tanks, batteries etc. The quality of the holes, which is particularly influenced by the manufacturing process, has a major influence on the fatigue strength of the beams and thus the service lifetime of the vehicle. In most cases, the holes are produced using the highly economical shear cutting process. Previous investigations have shown that the fatigue strength of thin sheets can be increased by adjusting the shearing parameters and using a two-stage shear cutting process. This paper discusses the difference between one- and two-stage shear cutting on the hole quality of components made of S500MC (1.0984, thickness 8 mm) and its resulting fatigue strength. The hole quality is characterized by the geometry of the shear cut surface, its roughness, microstructure, and microhardness. It was shown that the two-stage shear cutting process allows producing holes of better quality than the ones manufactured by a one-stage shear cutting process. Furthermore, this resulted in an improved fatigue behavior.

Understanding the Fatigue Notch Sensitivity of High-Strength Steels through Fracture Toughness

“…Both geometries in conventional tensile and in the normal location of failure onset exhibit a stress triaxiality of 0.33 at maximum force, which is in agreement with the results reported by several authors [39,40]. The shearing clearances specified in Table 3 are commonly used in chassis parts to avoid burrs and excessive deformation of the edge [21,41].…”

“…The technique leaves a cutting offset cut in a consecutive shearing operation resulting in a less damaged edge and better surface quality. The process highly improves the formability and fatigue resistance of the sheared material [21]. Another technique relies on introducing compressive residual stresses to the sheared edge through shot-peening and coining processes [22][23][24].…”

Fracture toughness to assess the effect of trimming on the fatigue behaviour of high-strength steels for chassis parts

“…The HR CP980 SF presents a longer burnish zone and less rollover than HR CP800 SF and HR DP600. These differences in the shear edge, related to the material properties, may affect the fatigue resistance as the burr, the defects in the fracture zone or the transition between the burnish to fracture zone act as stress concentration points [4]. Such locally higher stresses induce the nucleation of cracks that propagate throughout the specimen, as observed in figure 6.…”

“…Similarly, improving the edge geometries by reducing the fracture zone or the burr is proven to be effective in enhancing fatigue resistance. A clear example is the utilization of the double-shearing strategy [4]. In this case, the consecutive shearing process removes a thin layer of damaged material, leaving a smoother edge with less damage than after the first cutting operation.…”

Finite Element Analysis of Notch Depth and Angle in Notch Shear Cutting of Stainless-Steel Sheet

“…Rollover and burrs are the least desired zones on the surface, and investigations often involve methods and parameter modifications for eliminating these zones. Stahl et al [16] implemented two-stage shear cutting instead of one-stage shear cutting of truck frame parts and revealed the effects of different process parameters on the improvement of surface quality and burr formations along with fatigue enhancement of the sheared parts. Mucha and Tutak [17] studied the impact of clearance on the burr size formed on a thin steel sheet with a 55 HRC hardness during the blanking of angled hooks, as well as the wear characteristics of the punch.…”