The workpiece possesses surface residual stresses that exceed its fracture limit; specifically, prior machining, grinding, or heat treatment processes have left behind residual mechanical and thermal stresses within the surface layer. During grinding, the removal of the specific surface material that was maintaining this delicate stress equilibrium causes the remaining residual stresses to exceed the workpiece's material strength, thereby resulting in grinding cracks.

 

Among all contributing factors, the generation of cracks directly caused by the grinding process itself constitutes the core of the problem. The most significant issue is the stress induced by grinding heat. Due to the heat generated during grinding, the local temperature on the workpiece surface rises rapidly; this localized area effectively undergoes a tempering process or other forms of thermal alteration. Consequently, structural changes within the material—coupled with surface contraction—subject the surface to tensile stresses, ultimately leading to the formation of cracks.

 

 

1. The greater the grinding wheel's feed rate, the deeper the penetration depth of the residual stresses.

 

2. While surface residual stresses manifest as tensile stresses acting in the direction of grinding, they may simultaneously manifest as compressive stresses acting in the direction perpendicular to the grinding path; furthermore, as one probes deeper into the material, the magnitude of these stresses diminishes rapidly.

 

3. When analyzing stresses acting along both the grinding direction and the perpendicular direction, the stress state initially appears as compressive stress before abruptly shifting to tensile stress aligned with the grinding direction. Upon reaching its peak magnitude, the stress gradually decreases, eventually reverting to a minor compressive stress.

 

 

1. Tensile stress increases progressively as the grinding wheel's feed force increases, gradually approaching the ultimate tensile strength of the workpiece material. Once the residual stress exceeds the material's tensile strength, cracking will occur.

 

2. Compressive stress does not exhibit significant variation. While direct comparisons across different studies are difficult due to variations in measurement scales and experimental conditions, one consistent observation is that residual tensile stress reaches its maximum magnitude when the depth of cut (back-engagement) is set at 0.05 mm; even if the cutting depth is increased further, the magnitude of the residual tensile stress does not increase substantially beyond this point. This phenomenon is generally attributed to the shedding of abrasive grains during the grinding process.