基于广义边界层理论的超高速切削稳定性的理论与数值模拟研究
发布时间：2018-12-14 13:48
【摘要】：做为一种重要的加工成型手段，超高速切削具有效率高，精度好，在航空航天和模具制造等工业中有广泛的应用。切削过程中包含着材料发生的高应变、高应变率和过程中产生的高温等机理，导致材料发生屈服、失稳和断裂等现象。热粘塑性固体材料，在高应变率的加载条件下，常常会形成一条窄的、剧烈变化区域的剪切带。这种情形在很多情形下都会遇到；材料的超高速加工，终端弹道学(冲击动力学)。这种类型的变形，都有一个相似的特点：这种剪切带类似流体边界层，是一个很薄的、具有大的变形梯度的区域。其厚度的量级通常在10-100μm，同时伴有局部温度的剧烈变化，并且带的传播速度很快，有时能超过1000m/s。此种情况下，通常需要考虑以下因素：塑性大变形、率敏感性、应变硬化（加工硬化）、热对流、热传导、热软化、内耗作用和惯性效应。纯粹通过固体力学中定理与方程已经很难将这些影响因素考虑进去，必须适当借助流体力学边界层的相关理论进行研究。 本文主要基于广义边界层理论与线性摄动理论，建立包含应变硬化（加工硬化）、应变率硬化、热软化和惯性效应的切削稳定性动力学模型。本文所做的工作，主要包含一下两部分内容： 1)在广义边界层理论的基础上，综合运用流体力学中的纳维斯托克斯(Navier-Stokes)方程、连续性方程（不可压缩性）、欧拉场的应变演化方程、变形协调方程和能量方程建立二维平面应变问题的超高速切削的控制方程。在此基础上，运用流体力学边界层理论的无量纲化方法对上述控制方程进行无量纲化，用广义雷诺数Re（generalized Reynolds number）来表征切削过程中的惯性效应；通过广义雷诺数的引进来解决其他学者无法在切削理论模型中考虑惯性效应的困局，从而，真正在理论上讨论超高速切削问题（在以前的研究表明：低速切削时，切削稳定性的主控因素为应变硬化；在中高速切削时，主导因素为热软化作用；但是在超高速切削阶段则由惯性作用主导）。然后运用线性摄动理论对无量纲化后的控制方程进行近似求解得到能够完整描述切削稳定性的判据。 2)在第二章中所建立超速切削稳定性理论判据的基础上，首先运用商业软件ABAQUS/explicit and standard对高温镍基合金GH4169进行数值模拟研究。切削的速度范围为低速，中高速和超高速切削，最高速度达到360m/s。通过数值模拟发现三个速度阶段绝热剪切失稳的情况，然后通过研究切削过程中的切削力的波动情况来描述超高速切削阶段惯性作用对于塑性失稳的影响，找到切削力的波动情况随着切削速度增加的变化情况。最后，将数值模拟研究中得到的数值运用第二章得到的理论进行计算，得到扰动增长率随切削速度的变化情况。由于切削力的波动是扰动增长率的单值函数，两者相对于切削速度具有相同的变化趋势，所以，，本章将对比研究由数值模拟研究得到的切削力随切削速度的波动的波动情况和由第二章理论计算得到的扰动增长率随切削速度的变化情况，通过这种对比研究来间接证明第二章中所建立的切削稳定性理论判据的合理性。
[Abstract]:The high-speed cutting has the advantages of high efficiency and high precision, and has wide application in the industries of aerospace and die manufacture and the like. The mechanism of high strain, high strain rate and high temperature in the process of the material in the cutting process results in the occurrence of the material, the instability and the fracture. The hot-viscoplastic solid material, under the loading condition of high strain rate, is often formed with a narrow, highly variable region shear zone. This situation will be encountered in many cases; ultra-high speed processing of materials, terminal topology (impact dynamics). This type of deformation has a similar feature: this shear band is similar to the fluid boundary layer and is a very thin area with a large deformation gradient. The thickness of the belt is usually in the order of 10-100. m u.m, accompanied by a sharp change in local temperature, and the propagation speed of the belt is very fast, sometimes exceeding 1000m/ s. In this case, it is generally necessary to consider the following factors: plastic large deformation, rate sensitivity, strain hardening (work hardening), thermal convection, thermal conduction, thermal softening, internal friction and inertial effects. It is very difficult to consider these influencing factors through the theory and equation of solid mechanics, and the relevant theories of the hydrodynamic boundary layer must be properly studied. In this paper, based on the theory of generalized boundary layer and the theory of linear perturbation, the dynamic model of cutting stability including strain hardening (work hardening), strain rate hardening, thermal softening and inertia effect is established. Type. The work done in this paper mainly includes two parts Capacity: 1) On the basis of the theory of the generalized boundary layer, the Navier-Stokes equations, the continuity equation (incompressibility) and the strain of the Euler field are used in the comprehensive application of fluid mechanics. The Control of the High-speed Cutting of the Two-dimensional Plane Strain Problem Based on the Equation, the Deformation Coordination Equation and the Energy Equation On the basis of this, the non-dimensional method of the fluid mechanics boundary layer theory is used to dimensionless the above-mentioned control equation, and the generalized Reynolds number is used to characterize the use of the cutting process. The introduction of the generalized Reynolds number is used to solve the difficulty of the other scholars to consider the inertia effect in the cutting theory model, so that the very high-speed cutting problem is discussed in theory (the previous research shows that the main control factor of the cutting stability during low-speed cutting should be the main control factor of the cutting stability). in high-speed cutting, that dominant factor is the heat-softening effect; however, in the ultra-high-speed cutting stage, the inertia effect and then using the linear perturbation theory to approximate the dimensionless control equation to obtain the complete description of the cutting stability. On the basis of the theory criterion of the overspeed cutting stability established in the second chapter, the number of high-temperature nickel-based alloy GH4169 was first applied by using the commercial software ABAQUS/ explan and standard. Value simulation study. The speed range of the cutting is low speed, medium speed and ultra-high speed cutting, and the maximum speed is up to 3 It is found that the adiabatic shear instability of the three speed stages is found by numerical simulation, and then the inertia effect of the ultra-high-speed cutting stage is described by studying the fluctuation of the cutting force in the cutting process. The influence of the instability is found, and the fluctuation of the cutting force is found to increase with the cutting speed. and finally, calculating the numerical value obtained in the numerical simulation study by using the theory obtained in the second chapter to obtain the disturbance growth rate with the cutting speed The variation of the cutting force is a single-valued function of the disturbance growth rate, which has the same variation with respect to the cutting speed In this chapter, the fluctuation of the cutting force with the cutting speed and the disturbance growth rate calculated by the second theory are compared with the cutting speed. The change of the cutting stability theory established in the second chapter is directly proved by this comparative study.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG501
本文编号：2378712
[Abstract]:The high-speed cutting has the advantages of high efficiency and high precision, and has wide application in the industries of aerospace and die manufacture and the like. The mechanism of high strain, high strain rate and high temperature in the process of the material in the cutting process results in the occurrence of the material, the instability and the fracture. The hot-viscoplastic solid material, under the loading condition of high strain rate, is often formed with a narrow, highly variable region shear zone. This situation will be encountered in many cases; ultra-high speed processing of materials, terminal topology (impact dynamics). This type of deformation has a similar feature: this shear band is similar to the fluid boundary layer and is a very thin area with a large deformation gradient. The thickness of the belt is usually in the order of 10-100. m u.m, accompanied by a sharp change in local temperature, and the propagation speed of the belt is very fast, sometimes exceeding 1000m/ s. In this case, it is generally necessary to consider the following factors: plastic large deformation, rate sensitivity, strain hardening (work hardening), thermal convection, thermal conduction, thermal softening, internal friction and inertial effects. It is very difficult to consider these influencing factors through the theory and equation of solid mechanics, and the relevant theories of the hydrodynamic boundary layer must be properly studied. In this paper, based on the theory of generalized boundary layer and the theory of linear perturbation, the dynamic model of cutting stability including strain hardening (work hardening), strain rate hardening, thermal softening and inertia effect is established. Type. The work done in this paper mainly includes two parts Capacity: 1) On the basis of the theory of the generalized boundary layer, the Navier-Stokes equations, the continuity equation (incompressibility) and the strain of the Euler field are used in the comprehensive application of fluid mechanics. The Control of the High-speed Cutting of the Two-dimensional Plane Strain Problem Based on the Equation, the Deformation Coordination Equation and the Energy Equation On the basis of this, the non-dimensional method of the fluid mechanics boundary layer theory is used to dimensionless the above-mentioned control equation, and the generalized Reynolds number is used to characterize the use of the cutting process. The introduction of the generalized Reynolds number is used to solve the difficulty of the other scholars to consider the inertia effect in the cutting theory model, so that the very high-speed cutting problem is discussed in theory (the previous research shows that the main control factor of the cutting stability during low-speed cutting should be the main control factor of the cutting stability). in high-speed cutting, that dominant factor is the heat-softening effect; however, in the ultra-high-speed cutting stage, the inertia effect and then using the linear perturbation theory to approximate the dimensionless control equation to obtain the complete description of the cutting stability. On the basis of the theory criterion of the overspeed cutting stability established in the second chapter, the number of high-temperature nickel-based alloy GH4169 was first applied by using the commercial software ABAQUS/ explan and standard. Value simulation study. The speed range of the cutting is low speed, medium speed and ultra-high speed cutting, and the maximum speed is up to 3 It is found that the adiabatic shear instability of the three speed stages is found by numerical simulation, and then the inertia effect of the ultra-high-speed cutting stage is described by studying the fluctuation of the cutting force in the cutting process. The influence of the instability is found, and the fluctuation of the cutting force is found to increase with the cutting speed. and finally, calculating the numerical value obtained in the numerical simulation study by using the theory obtained in the second chapter to obtain the disturbance growth rate with the cutting speed The variation of the cutting force is a single-valued function of the disturbance growth rate, which has the same variation with respect to the cutting speed In this chapter, the fluctuation of the cutting force with the cutting speed and the disturbance growth rate calculated by the second theory are compared with the cutting speed. The change of the cutting stability theory established in the second chapter is directly proved by this comparative study.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG501
【参考文献】
相关期刊论文 前2条
1 汪小芳,陶伟明,郭乙木;刀-屑摩擦对残余应力分布影响的模拟分析[J];农业机械学报;2005年04期
2 宗文俊,王洪祥,李旦,程凯,董申;基于有限元法分析超精密切削中的摩擦问题[J];制造技术与机床;2004年08期
本文编号：2378712
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