置氢钛合金高速正交切削切削力的仿真

利用分离式霍普金森压杆(SHPB)实验得到置氢钛合金的流动应力与应变关系,通过数据拟合获得置氢钛合金的Johnson-Cook(J-C)热粘塑性本构模型,应用该模型及有限元分析软件模拟了置氢钛合金切削过程,并进行了相关的验证性切削实验。不同置氢含量钛合金切削力对比显示,置氢工艺改善了钛合金的切削难加工性;高速切削置氢钛合金模拟结果表明,在120m/min切削条件下,置氢能够较大的减小切削力。     

基于黏结-滑移摩擦模型的304不锈钢切削力仿真研究*

通过预测加工304不锈钢时产生的切削力,从而对切削参数和刀具几何参数进行优化,是提高304不锈钢的加工精度、切屑控制及保障刀具寿命的基础。建立304不锈钢切削仿真模型,为提高模型的精确性,选择Johnson-Cook本构方程和黏结-滑移摩擦模型。结果表明：采用黏结-滑移摩擦模型的切削力预测结果更为准确,表明相对于纯剪切摩擦与库仑摩擦模型,黏结-滑移摩擦模型能更准确地描述刀-屑摩擦特性。展开不同参数下的切削力研究,研究发现：切削力随着刀具前角、后角和切削速度的增大而减小,随切削刃钝圆半径和切削厚度、宽度的增大而增大,其中切削宽度、厚度及前角对切削力大小影响较大。研究结果为304不锈钢切削效率的提高和切削机制的研究提供了理论依据。     

考虑热塑性变形的316H不锈钢Johnson-Cook本构参数逆向识别

本构模型能表征材料变形过程中的动态响应,其精度对机械加工中切削力、切削温度的解析预测具有决定性作用.针对316H不锈钢本构模型缺失问题,提出一种基于切削理论的Johnson-Cook本构参数逆向识别方法.通过建立的不等分主剪切区的应力、应变、应变率及温度分布的数学模型,以及准静态压缩试验和正交切削试验的数据,采用粒子群...     

基于正交切削的铝合金切削力理论计算方法

基于传统正交切削力学模型,采用Johnson-Cook材料本构和失效模型,建立同时考虑前刀面和后刀面双摩擦因素的切削力理论计算模型。采用双摩擦切削力模型模拟7050航空铝合金切削力的计算,获得了与试验结果非常吻合的切削力理论计算值。用本文模型计算了不同Johnson-Cook材料本构参数下的切削力,获得了与文献仿真值非常一致的结果。双摩擦切削力模型引入的后刀面摩擦分量,在航空铝合金切削仿真中,占主切削力的比重较少(约占12.5%),但不可忽略。     

0Cr18Ni9不锈钢正交切削过程的数值模拟

为研究0Cr18Ni9(AISI 304)不锈钢切削加工过程,采用刚塑性有限元方法,建立有限元仿真模型,利用自适应网格(ALE)划分技术对其网格进行重新划分。根据Johnson-Cook本构模型建立工件材料模型,运用CrockroftLatham断裂准则来实现工件材料的断裂,刀屑界面摩擦采用剪切摩擦。通过模拟得到锯齿状切屑,并分析工件及切屑的等效应变、等效应力与主应力、切削温度及切削力的变化规律。该结果对研究不锈钢的切削机理将提供有用的依据。     

切削置氢TC4钛合金切削力及切削温度的有限元分析

利用有限元技术,研究了氢含量对TC4钛合金切削力及切削温度的影响规律,并对高速切削时的切削力、切削温度的规律进行了预测.利用电子万能材料试验机及霍普金森压杆装置获取了不同应变速率及温度时置氢钛合金的流变行为,通过数据的拟合得到了Johnson-Cook(J-C)本构方程,据此建立了切削数值模型.切削力及切削温度的模拟结...     

基于改进温度模型的300M钢本构方程参数识别

为了提高通过切削实验获取材料本构方程参数的精度,提出了将基于移动热源理论的温度分布模型沿剪切面积分计算剪切区平均温度的方法,结合不等距剪切区模型求得等效应变和应变率,建立了材料Johnson-Cook(J-C)本构方程参数的求解模型。根据切削实验获取的切削力和切屑厚度数据并采用遗传算法求得了300M钢J-C本构方程参数。与AdvantEdge FEM软件自带的300M钢本构模型相比,用所求模型参数仿真得到的主切削力、进给力和切屑厚度的精度有显著提高,验证了所建本构方程参数求解模型的有效性。     

高应变率下材料本构模型建模及其在插齿切削力预测中的应用

插齿是加工齿轮的重要工艺方法,插削力是制定插齿加工工艺的重要依据。为获得插齿过程中的工件材料属性,采用霍普金森压杆试验,获得工件材料高应变(10~2~10~4s~(-1))下的Johnson-Cook(J-C)本构模型。基于工件材料本构模型,通过有限元模拟插齿过程,获得插齿切削力。采用刨削模拟插齿切削,对插齿切削力进行了实测试验。通过对比分析插齿切削力、模拟与试验结果,验证了本构模型和有限元模型及模拟结果的正确性,进而通过有限元数值模拟分析了刀具几何参数和切削参数对切削力的影响规律。文中建立的材料本构模型和插齿切削有限元模型可较准确地预测插齿切削力。     

钛合金TC4超声波振动切削有限元仿真

采用Johnson-Cook材料模型,以任意拉格朗日欧拉网格算法（ALE）实现切屑分离,建立了热应力耦合二维正交振动切削模型,并进行了钛合金TCA超声波振动稳态切削的有限元仿真,得到了振动切屑形状和切削力、切削温度的变化曲线,同时将振动切削与普通切削进行了对比分析,分析结果表明,振动切削中切屑变形系数、切削力、切削温度明显降低,剪切角增大。     

基于热力耦合模型的金属切削过程有限元分析

基于有限元理论和热力耦合模型的研究,通过讨论切削过程中的关键技术,主要包括切削加工有限元方程的建立：构件材料的Johnson-Cook本构模型;切屑分离准则;材料断裂准则;接触摩擦模型;切削热的产生和分布;残余应力的分析和切削力的比较分析等,建立了二位金属切削过程模型,通过采用粘结．滑移摩擦模型,有效地模拟了航空钛合金的切削加工过程,对此类材料加工的切削力、切屑温度以及应力场和应变的分布进行了分析。     

Modeling of ductile fracture using the dynamic punch test

Many models have been proposed for simulating events at quasi-static and dynamic rates. However, the Johnson–Cook constitutive model had been the workhorse for engineers and analysts when simulating such events, and it is readily available in the increasingly widespread numerical packages. Johnson and Cook also suggested a generalized failure model to be used with their constitutive model, but the challenge has always been in easily determining the correct parameters for these models. In this study, a procedure for determining the Johnson–Cook constitutive and, simplified, failure model parameters for three materials with specific importance in the aerospace industry, aluminum 6061-T6, titanium Ti-6Al-4 V and austenitic, nitrogen-strengthened, stainless steel (Nitronic 33) is proposed. Quasi-static and split Hopkinson pressure bar (SHPB) shear punch experiments were used to assess the materials’ ductility, while the quasi-static and SHPB compression experiments were used to determine the materials’ response. The laboratory results coupled with ABAQUS/Explicit simulations provided a tool for determination and validation of the models’ parameters for each material. While the use of the Johnson–Cook model with the proposed simplified failure model proved adequate for aluminum and titanium, the same could not be concluded for nitronic partly due to the intrinsic characteristics of this material and the multiplicative form of the Johnson–Cook model.     

Constitutive modeling for Ti-6Al-4V alloy machining based on the SHPB tests and simulation

A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 10~4–10~6 s~(–1). Flow stresses at high strain rates are close to that of cutting are difficult to test via experiments. Split Hopkinson compression bar(SHPB) technology is used to study the deformation behavior of Ti-6Al-4V alloy at strain rates of 10~(–4)–10~4s~(–1). The Johnson Cook(JC) model was applied to characterize the flow stresses of the SHPB tests at various conditions. The parameters of the JC model are optimized by using a genetic algorithm technology. The JC plastic model and the energy density-based ductile failure criteria are adopted in the proposed SHPB finite element simulation model. The simulated flow stresses and the failure characteristics, such as the cracks along the adiabatic shear bands agree well with the experimental results. Afterwards, the SHPB simulation is used to simulate higher strain rate(approximately 3×10~4 s~(–1)) conditions by minimizing the size of the specimen. The JC model parameters covering higher strain rate conditions which are close to the deformation condition in cutting were calculated based on the flow stresses obtained by using the SHPB tests(10~(–4)–10~4 s~(–1)) and simulation(up to 3×10~4 s~(–1)). The cutting simulation using the constitutive parameters is validated by the measured forces and chip morphology. The constitutive model and parameters for high strain rate conditions that are identical to those of cutting were obtained based on the SHPB tests and simulation.     

High-temperature dynamic deformation of aluminum alloys using SHPB

This paper investigates the dynamic deformation behavior of two aluminum alloys, 2024-T4 and 6061-T6, using a modified split Hopkinson pressure bar (SHPB) with a pulse shaper technique at both elevated and room temperatures. An experimental strategy is proposed, and the dynamic deformation behaviors of two alloys are evaluated with the modified high-temperature SHPB apparatus. The experiments were carried out under varying strain rates and temperatures. The reflected waves modulated by the pulse shaper, the flow stress-strain relationships, the strain rates, the front- and back-ends stresses during the dynamic deformation period were measured at varying high temperatures. Experimentally obtained data were used to evaluate the parameters in the material constitutive equation, such as the Johnson-Cook (JC) constitutive model.     

Experimental study and modelling of tool temperature distribution in orthogonal cutting of AISI 316L and AISI 3115 steels

Cutting tool temperature distribution was mapped using the IR-CCD technique during machining of carbon steel AISI 3115 and stainless steel AISI 316L under orthogonal cutting conditions using flat-face geometry inserts. The effect of work material treatment on tool temperature was investigated, and the results showed that AISI 3115 in heat-treated state displayed higher tool temperature than the as-rolled state. Stainless steel 316L with high sulphur content (0.027?wt.%) and calcium treatment displayed lower cutting tool temperature than the variant with low sulphur (0.009?wt.%). The experimental results were compared with theoretical tool temperature distributions based on a modified version of Komanduri and Hou??s analytical model. In particular, variable frictional heat source and secondary shear were introduced and modelling of the tool stress distribution on rake surface was also considered.     

基于Deform的304不锈钢的车削仿真与实验研究

不锈钢是典型的难加工材料。为进一步研究不锈钢的切削机理,利用Deform 3D有限元软件对304不锈钢的车削过程进行了仿真,仿真结果可以为切削用量的优化选择提供理论依据。采用正交试验法,在CA6140A车床上进行了车削304不锈钢的加工试验,用测力仪测量了切削力数值,并比较分析了试验结果与有限元仿真的结果。     

45钢高速切削过程中切屑形成的数值模拟

为了研究45钢高速加工中切屑形成机理,建立了高速加工的正交切削有限元模型,研究了45钢高速切削有限元建模过程中的Johnson-Cooks材料模型,刀屑接触模型及切屑分离准则等关键技术.利用建立的有限元模型对45钢的高速切削过程中的切屑成形进行了数值模拟,并研究了不同切削速度对切屑锯齿化程度的影响规律,得到了不同切削速度下的切屑锯齿化程度.     

Numerical study the flow stress in the machining process

In the machining process, the workpiece is under severe plastic deformation with large strain, high strain rate, and temperature. It is necessary to know the flow stress of workpiece material in such condition to better understand the mechanism of chip formation, tool wear and damage, etc. In this study, a Split Hopkinson Pressure Bar (SHPB) with synchronically assembled heating system was employed to study the flow stress similar to the deformation condition in the machining process. A phenomenological constitutive model was proposed by the regression analysis of the experimental results. Furthermore, orthogonal metal cutting processes were carried out by the finite element method (FEM). The cutting force predicted by the FEM showed good agreement with the experimental results, which confirmed that the proposed constitutive model can give an accurate estimate of the flow stress in the machining process.