In this study the stress fields under uniaxial tension of the plane with arc cut were calculated. To describe the concentration of normal and shear stresses in the areas of the crack ends, new characteristics based on equilibrium conditions were introduced. The influence of the angle of the crack arc opening and the direction of the plane tension was studied. It was found that those factors changed the value and the stresses sign at the crack ends. The opening angles of arc cracks and tension direction promoting the development of cracks under the influence of tensile strain, tensile stresses or combination of the stresses were determined. The promoting conditions that inhibit the cracks were studied. Copyright © VBRI Press.