Identification of the optimum cutting parameters in intermittent hard turning with specific cutting energy, damage equivalent stress, and surface roughness considered

Studies on specific cutting energy, damage equivalent stress, and surface roughness were conducted to identify the optimum cutting parameter area in intermittent hard turning. The optimum cutting parameter area was acquired based on finite element simulations, micromechanics, damage mechanics, and intermittent turning tests. It was found that the transient specific cutting energy and the transient damage equivalent stress evolved cyclically with the periodical formation of saw-tooth chip. The average specific cutting energy in the cutting period became larger as tool wear increased. However, the average damage equivalent stress in the cutting period and surface roughness decreased first and then increased when tool wear became higher. The evolution process of these average values and surface roughness with tool wear can be divided into three stages. There were obvious corresponding relationships between these three stages and the tool wear stages. Analysis of the mean values of specific cutting energy, damage equivalent stress, and surface roughness in the steady tool wear stage indicated that when the feed rate was in the range of 0.2 to 0.25 mm/r and cutting speeds ranging from 110 to 125 m/min were adopted, relatively low energy consumption, relatively long tool life, and relatively good surface quality can be obtained at the same time.