机械加工——机械类外文翻译、中英文翻译.docVIP

TOOL WEAR MECHANISMS ON THE FLANK SURFACE OF CUTTING INSERTSFOR HIGH SPEED WET MACHINING 5.1 Introduction Almost every type of machining such as turning, milling, drilling, grinding..., uses a cutting fluid to assist in the cost effective production of parts as set up standard required by the producer [1]. Using coolant with some cutting tools material causes severe failure due to the lack of their resistance to thermal shock (like AL2O3 ceramics), used to turn steel. Other cutting tools materials like cubic boron nitride (CBN) can be used without coolant, due to the type of their function. The aim of using CBN is to raise the temperature of the workpice to high so it locally softens and can be easily machined. The reasons behind using cutting fluids can be summarized as follows. Extending the cutting tool life achieved by reducing heat generated and as a result less wear rate is achieved. It will also eliminate the heat from the shear zone and the formed chips. Cooling the work piece of high quality material under operation plays an important role since thermal distortion of the surface and subsurface damage is a result of excessive heat that must be eliminated or largely reduced to produce a high quality product. Reducing cutting forces by its lubricating effect at the contact interface region and washing and cleaning the cutting region during machining from small chips. The two main reasons for using cutting fluids are cooling and lubrication. Cutting Fluid as a Coolant: The fluid characteristics and condition of use determine the coolant action of the cutting fluid, which improves the heat transfer at the shear zone between the cutting edge, work piece, and cutting fluid. The properties of the coolant in this case must include a high heat capacity to carry away heat and good thermal conductivity to absorb the heat from the cutting region. The water-based coolant emulsion with its excellent high heat capacity is able to reduce tool wear [44]. Cutting Fluid as a