基于廣義邊界層理論的超高速切削穩(wěn)定性的理論與數(shù)值模擬研究
發(fā)布時間：2018-12-14 13:48
【摘要】：做為一種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業(yè)中有廣泛的應(yīng)用。切削過程中包含著材料發(fā)生的高應(yīng)變、高應(yīng)變率和過程中產(chǎn)生的高溫等機(jī)理，導(dǎo)致材料發(fā)生屈服、失穩(wěn)和斷裂等現(xiàn)象。熱粘塑性固體材料，在高應(yīng)變率的加載條件下，常常會形成一條窄的、劇烈變化區(qū)域的剪切帶。這種情形在很多情形下都會遇到；材料的超高速加工，終端彈道學(xué)(沖擊動力學(xué))。這種類型的變形，都有一個相似的特點(diǎn)：這種剪切帶類似流體邊界層，是一個很薄的、具有大的變形梯度的區(qū)域。其厚度的量級通常在10-100μm，同時伴有局部溫度的劇烈變化，并且?guī)У膫鞑ニ俣群芸�，有時能超過1000m/s。此種情況下，通常需要考慮以下因素：塑性大變形、率敏感性、應(yīng)變硬化（加工硬化）、熱對流、熱傳導(dǎo)、熱軟化、內(nèi)耗作用和慣性效應(yīng)。純粹通過固體力學(xué)中定理與方程已經(jīng)很難將這些影響因素考慮進(jìn)去，必須適當(dāng)借助流體力學(xué)邊界層的相關(guān)理論進(jìn)行研究。 本文主要基于廣義邊界層理論與線性攝動理論，建立包含應(yīng)變硬化（加工硬化）、應(yīng)變率硬化、熱軟化和慣性效應(yīng)的切削穩(wěn)定性動力學(xué)模型。本文所做的工作，主要包含一下兩部分內(nèi)容： 1)在廣義邊界層理論的基礎(chǔ)上，綜合運(yùn)用流體力學(xué)中的納維斯托克斯(Navier-Stokes)方程、連續(xù)性方程（不可壓縮性）、歐拉場的應(yīng)變演化方程、變形協(xié)調(diào)方程和能量方程建立二維平面應(yīng)變問題的超高速切削的控制方程。在此基礎(chǔ)上，運(yùn)用流體力學(xué)邊界層理論的無量綱化方法對上述控制方程進(jìn)行無量綱化，用廣義雷諾數(shù)Re（generalized Reynolds number）來表征切削過程中的慣性效應(yīng)；通過廣義雷諾數(shù)的引進(jìn)來解決其他學(xué)者無法在切削理論模型中考慮慣性效應(yīng)的困局，從而，真正在理論上討論超高速切削問題（在以前的研究表明：低速切削時，切削穩(wěn)定性的主控因素為應(yīng)變硬化；在中高速切削時，主導(dǎo)因素為熱軟化作用；但是在超高速切削階段則由慣性作用主導(dǎo)）。然后運(yùn)用線性攝動理論對無量綱化后的控制方程進(jìn)行近似求解得到能夠完整描述切削穩(wěn)定性的判據(jù)。 2)在第二章中所建立超速切削穩(wěn)定性理論判據(jù)的基礎(chǔ)上，首先運(yùn)用商業(yè)軟件ABAQUS/explicit and standard對高溫鎳基合金GH4169進(jìn)行數(shù)值模擬研究。切削的速度范圍為低速，中高速和超高速切削，最高速度達(dá)到360m/s。通過數(shù)值模擬發(fā)現(xiàn)三個速度階段絕熱剪切失穩(wěn)的情況，然后通過研究切削過程中的切削力的波動情況來描述超高速切削階段慣性作用對于塑性失穩(wěn)的影響，找到切削力的波動情況隨著切削速度增加的變化情況。最后，將數(shù)值模擬研究中得到的數(shù)值運(yùn)用第二章得到的理論進(jìn)行計算，得到擾動增長率隨切削速度的變化情況。由于切削力的波動是擾動增長率的單值函數(shù)，兩者相對于切削速度具有相同的變化趨勢，所以，，本章將對比研究由數(shù)值模擬研究得到的切削力隨切削速度的波動的波動情況和由第二章理論計算得到的擾動增長率隨切削速度的變化情況，通過這種對比研究來間接證明第二章中所建立的切削穩(wěn)定性理論判據(jù)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.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG501
本文編號：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.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG501
【參考文獻(xiàn)】
相關(guān)期刊論文 前2條
1 汪小芳,陶偉明,郭乙木;刀-屑摩擦對殘余應(yīng)力分布影響的模擬分析[J];農(nóng)業(yè)機(jī)械學(xué)報;2005年04期
2 宗文俊,王洪祥,李旦,程凱,董申;基于有限元法分析超精密切削中的摩擦問題[J];制造技術(shù)與機(jī)床;2004年08期
本文編號：2378712
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