The International Journal of Engineering and Science (IJES) || Volume || 9 || Issue || 11 || Series I || Pages || PP 29-35 || 2020 || ISSN (e): 2319-1813 ISSN (p): 20-24-1805 DOI:10.9790/1813-0911012835 www.theijes.com Page 29 The Effect of the Cutting Gap on the Microhardness in the Area of the Strain Hardened Cutting Surface Vladimír Rohaľ 1 , Emil Spišák 1 , Peter Mulidrán 1 , Samuel Vilkovský 1 , Janka Majerníková 1 1 Institute of Technology and Material Engineering, Faculty of Mechanical Engineering, Technical University of Košice, Košice, Slovakia --------------------------------------------------------ABSTRACT----------------------------------------------------------- This work deals with the effect of the cutting gap on the microhardness in the area of the strain hardened cutting surface. The aim of this study is to understand the relationship between the shear cutting process and the strain hardened cutting surface of an electrical steel sheet. Mechanical stress occurring during the manufacturing process of electrical machines detrimentally alters the magnetic properties (iron losses and magnetizability). This affects the efficiency and performance of the machine. The geometry of the shear cut edge as well as the depth and degree of work hardening in the shear affected zone can be adjusted by using specific shear cutting parameters, such as die clearance and cutting-edge radius. Keywords – microhardness, elongation, cutting gap, cutting surface, electrical steel, mechanical tensile test ------------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 18-11-2020 Date of Acceptance: 03-12-2020 ------------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Nowadays, when it is generally common trend to expand the use of electric cars on the market as much as possible, mainly due to declining stocks of non-renewable energy sources, as well as efforts to protect the environment more effectively, research and development in this area is extremely relevant. However, a significant part of the research in this area is devoted to sources of electricity, respectively development of batteries, which are subject to very high requirements. A significantly smaller part of the research is focused on improving the efficient use of stored energy, thus to reduce losses of electric motors. According to current knowledge, the quality of cutting surfaces after cutting and assembling rotors and stators also influences the efficient use of stored energy. The results of the shear cutting process are changes in the surface of the base material. These changes not only affect their geometric properties, but also change the physical, chemical and mechanical properties of the surface (microstructural changes, cracks and microcracks, microhardness, corrosion resistance, etc.). All these changes are part of the concept of surface integrity, which is one of the basic aspects in terms of quality requirements, especially in structural elements for stator and rotor cores in electric motors, where these requirements are very high due to functionality and reliability. [ 1, 2] The shear cutting process is one of the most economical separation processes, since it combines high production rates with low costs. The quality of the shear cut edge depends on the material properties, material thickness, die clearance, cutting edge radius, tool wear and shear cutting strategy. [3] The variation of the influence factors can significantly affect the surface quality of a cut-outs. In addition to the four surface characteristics of rollover zone, clean shear zone, fracture zone and burrs zone, the cutting process causes an area affected by the shear that extends from the edge of the cut to the adjacent material. The shear affected zone represents the volume of material, which is subjected to plastic deformation during the shear cutting process and therefore experiences a strong work-hardening. Because the growth of the fatigue crack in the shear components usually starts from the cutting edge, the shear cutting surface, as well as the affected zone, has a significant effect on the fatigue behavior of the component. [4,5] Silicon steels are the essence of electrical appliances and they provide the best combination for electricity distribution and transmission. Desired properties of these steels are low magnetic losses, high permeability and induction and low magnetostriction. Low magnetic losses reduce heat generation and power consumption, a high permeability and induction result in reduced size and mass of the parts, and low magnetostriction decreases the noise (manifested as buzzing) in transformers and large capacity machines. [6] In the case where the machines are driven by alternating current, the magnetization takes place in rapidly changing fields, which causes the hysteresis loop to be distorted by the effect of eddy currents. Energy