圆弧面凹模刃口直边线切割加工工艺设计

利用慢走丝线切割编程原理以及机床上下异形加工功能的特点,实例分析如何采用偏移计算、添加补偿点、上下异形(锥度加工)等加工原理进行圆弧凹模刃口直边的加工,从而获得均匀的圆弧冲孔刃口直边,大大提高凹模刃口的使用寿命,降低模具加工费用,缩短模具制造周期。     

凹模刃口倒角对薄壁精冲件塌角高度的影响

介绍了塌角形成及其影响因素,设计了凹模刃口倒角部分。为减小薄壁精冲件断面塌角,利用有限元模拟软件DEFORM-2D研究了某型槽针针坯的塌角情况。通过改变凹模刃口倒角高度,观察针坯塌角变化及光亮带比例变化情况。分析了塌角大小随凹模刃口倒角高度变化趋势及冲裁过程中力-行程曲线。对模拟情况做了相关实验,实验结果与模拟结果基本一致。对于薄板冲裁件而言,塌角高度随凹模刃口倒角高度减小而减小,但倒角高度过小时,撕裂带会增大,光亮带比例有所减小。     

复杂凹模（刃口）的简易加工方法

针对形状复杂凹模内孔非刃口部分加工困难的问题,提出了凹模刃口部分和非刀口部分分别加工即组合凹模的概念,使凹模部分的制造变得简单、容易,并降低了模具制造成本。     

模具间隙对冲件尺寸精度的影响

1.问题的提出实践证明,落料件的尺寸接近于凹模刃口尺寸,冲孔的尺寸接近于凸模刃口的尺。因此计算凸凹模尺寸应遵守的原则。(1)落料时,先确定凹模刃口尺寸,其大小应取接近或等于冲件的最小极限尺寸,以保证凹模磨损至一定尺寸后,也能冲出合格冲件。凸模刃口的基本尺寸应比凹模刃口基本尺寸小一     

凹模刃口倒角及模具间隙对细薄精冲件断面塌角的影响

为了减小精冲件断面塌角,分析研究了塌角形成及其影响因素,设计了凹模刃口倒角。对影响精冲件断面塌角的凹模刃口倒角高度及倒角角度、凹凸模间隙三个因素进行了研究,并设计了考虑交互作用的正交试验,测量了精冲件塌角及光亮带比例。结果表明,在凹模倒角高度为0.05 mm、倒角角度5°、模具间隙0时,细薄精冲件的断面质量较好。     

闭挤式精冲变形区应力状态对断裂损伤的影响

文章将考虑静水应力、最大主应力及应变历史对材料损伤影响的Brozzo断裂准则模型,用于闭挤式精冲的断裂预测。分析了变形区材料的应力、应变状态对材料断裂损伤的影响,并通过DEFORM-2D有限元软件的模拟及物理试验进行验证。研究表明,Brozzo断裂准则能比较精确地模拟闭挤式精冲过程,模拟结果与试验误差在6%以内;主、副凹模闭合时,变形区材料所受的压应力越大,越有利于抑制裂纹的产生和扩展;精冲过程中,凸模刃口附近材料的压应力大于主凹模刃口附近材料,裂纹首先出现在主凹模刃口处,材料开始产生裂纹时的有效应变,随压应力的增加而增大。     

提高冲裁模寿命的途径

提高冲裁模寿命是好多工业部门冷冲压生产中的一个重要问题。将现有的提高冲裁模寿命的方法运用于生产,并探讨新的、更有效的提高冲裁模寿命的方法,其意义是很明显的。冲裁模工作零件(冲头和凹模)刃口处的工作特点是单位面积上要承受短时间、周期性的高负荷的作用,这就导致刃口出现微观和宏观的疲劳剥落以及冲头损坏。     

防止废料上行的最佳凹模形状

本文报告了一种倒锥形刃口凹模能成为有效防止废料上行的最佳凹模形状的初步实验研究结果。     

模锻件切边凹模刃口形状探讨

通过对模锻件切边过程与定位要求的描述，对切边凹模刃口形状与模锻件飞边桥部关系的分析，并基于实践经验，指出对于非平面分模锻件和水平投影轮廓形状复杂的锻件，切边凹模刃口形状不宜完全按(热)锻件分模面轮廓制造，而应针对锻件具体结构作一些调整。     

谈弯曲件级进冲模的设计(二)

三 弯曲件级进模的下模设计 弯曲件级进模的下模是由两部分凹模组成,即一部分凹模对工件进行冲裁,另一部分凹模对工件进行弯曲变形。这两部分的凹模在使用过程中又出现不同情况,对于冲裁变形的凹模部分,随着不断地冲压其刃口需经常进行修磨。而进行弯曲变形的凹模则没有这种现象。由于冲裁凹模与弯曲部分的凹     

Fatigue failure of coated carbide tool and its influence on cutting performance in face milling SKD11 hardened steel

Failure patterns of coated carbide tool were investigated by high-speed face milling of the hardened steel SKD11. Tool failure surface morphology, cutting force and machined surface roughness were also analyzed to reveal the failure mechanisms. The results indicated that the dominant failure pattern of coated carbide tool was breakage. The primary mechanism of tool breakage was fatigue fracture. Under different cutting speeds, the distinctive morphologies of fatigue fracture were presented on the failure surfaces. At low cutting speeds, many fatigue sources were observed on the rake face. The distance between fatigue sources and tool nose was approximately two times of the depth of cut. With the increase of cutting speed, the fatigue striations and riven patterns were observed at the fracture surface. In addition, the fatigue steps and crack deflection were found under high cutting speeds. The main fracture mode was intergranular fracture at lower cutting speeds. However, it was transgranular fracture at higher cutting speeds. Furthermore, the irregular fracture surfaces at low cutting speeds and at high cutting speeds contribute to a larger cutting force increment compared with the medium cutting speeds. The increment of surface roughness in the initial and severe wear stages was lower than that in the steady wear stage, while the deviation of surface roughness was relatively large.     

陶瓷刀具断续车削淬硬钢失效形态研究

采用Al_2O_3/Ti(C,N)陶瓷刀具进行淬硬钢的断续车削正交试验,对不同切削速度下刀具的失效形态进行了对比。结果表明,低速时,刀具的失效形态主要是崩刃和前刀面剥落,疲劳破损影响较小。随着切削速度的增加,疲劳破损对刀具的影响逐渐增大。高速时,疲劳裂纹扩展引起的破损成为刀具主要失效形式。在不同切削速度下,刀具内部的应力水平不同,导致裂纹扩展速率及裂纹方向有所差异,疲劳特征则表现出不同形式。低速时疲劳特征表现为疲劳条带,而高速时的疲劳特征通常为疲劳弧线。     

冲击功对球磨机衬板用低碳高合金钢冲击腐蚀磨损性能的研究

利用改造的冲击腐蚀磨损机,测试了不同冲击功下低碳高合金钢的冲击腐蚀磨损性能。结果表明,在模拟实际工况条件下,当冲击功为0.7、1.2和1.7J时,低碳高合金钢的冲击腐蚀磨损机理分别为轻微的显微切削、轻微的微观犁皱和二次显微切削以及挤出棱的低周疲劳沿根断裂,长时间后则兼有少量的加工硬化层的浅层疲劳剥落和轻微的腐蚀磨损。在低冲击功下,低碳高合金钢具有优良的耐冲击腐蚀磨损性能,是一种优良的冶金矿山用湿式球磨机衬板用钢。     

Polycrystalline diamond cutting element control using high frequency C-scan image processing

The quality control of drilling tools used in the oil industry essentially consists of testing the cutting elements distributed around the petroleum tool. This study presents a nondestructive testing (NDT) method for the detection of different kinds of defects inside polycrystalline diamond cuttine elements (PDC). This ultrasonic method, based on high frequency (100 MHz) C-scan image processing, allows the detection of three major types of defect such as diamond layer debonding from the substrate, cracks and thermal defects of the diamond layers. These defects induce a perfectly quantified behaviour to mechanical abrasion resistance and fatigue tests. Experimental results show good correlation between our ultrasonic measurements and classical abrasion resistance tests. In fact, a PDC sample exhibiting defects detected by the C-scan technique has been submitted to a mechanical fatigue process and optical microscopic analysis. These tests have shown that each kind of defect has an influence on one or more mechanical characteristics. Using C-mode scanning acoustic microscopy (with a 50 μm pixel size), allows an extremely precise and quantified level of erosion resistance of the cutting elements without systematic resort to expensive destructive tests carried out during the reception of the batch. The rejection of samples showing harmful defects will eliminate the erratic and sometimes unexplained destruction of some tools which were considered to be defect-free.     

The effect on fatigue life of residual stress and surface hardness resulting from different cutting conditions of 0.45%C steel

The affected layer is generated within the machined surface layer through the cutting process. Cutting conditions such as the nose radius of the tool, feed rate and shape of cutting edge at the finishing operation affect the residual stress, surface hardness, and surface roughness. In this paper, it is shown that such machined surface property could be controlled by the setting of the cutting conditions to some extent. Then the effect of the machining conditions on the fatigue life was investigated through a fatigue test using the specimen finished under various cutting conditions. It was shown that it is possible to get longer fatigue life for machined parts than the virgin material or the carefully finished material without affected layer, only by setting the proper cutting conditions. Such a situation was realized when the generated residual stress was small and the induced surface hardness was high. A longer fatigue life for the machined components can be obtained by applying such cutting conditions as a low feed rate, a small corner radius and a chamfered cutting edge tool.     

某型号前轴疲劳试验及结果分析

为测试前轴的疲劳寿命,采用台架试验装置对某型号汽车前轴进行了试验,仅运行19.9万次就发生断裂。通过对断口的观察分析、断口部位的金相分析、硬度检测等方式,确定了前轴的失效模式,并对其断裂失效原因进行了分析。研究结果表明:汽车前轴的断裂性质为疲劳断裂,裂纹源起源于锻件飞边表面,该处存在较明显的沟槽;锻件表面的加工沟槽形成的附加应力集中是造成前轴疲劳断裂的主要原因;加工沟槽可能由于切边模的磨损而产生,因此切边模刃口需及时修整。     

The influence of mechanical and CO2 laser cut-edge characteristics on the fatigue life performance of high strength automotive steels

The cut-edge characteristic properties of automotive structures formed during the mechanical blanking and laser-cutting processes significantly influence fatigue life performance. This factor is becoming increasingly important as S355MC and DP600 high strength steels (HSS) grades under investigation exhibit an increased sensitivity to fatigue cracks initiating from cut-edge regions. It was determined that by manipulating the critical cutting process parameters, clearance in terms of mechanical blanking, and by controlling the interrelationship between power and traverse cutting speed during the laser cutting process can result in optimised fatigue lives being achieved. Optimal fatigue lives were attained by minimising the cut-edge surface damage and by controlling the near edge microstructural deformations during each cutting process. It is the critical significance of fatigue which is the limiting factor towards being able to effectively downgauge steel grades used as automotive chassis and suspension components. This research is some of the first that considers the influence of mechanical and laser cut-edge surface quality and internal properties, which has then been partnered to the critical fatigue performance of HSS grades.     

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 用TC4和TC8钛合金制造的加工刀具,在使用过程中发生失效。利用金相分析、力学性能测试和无损检测等手段对刀具失效的原因进行了分析。结果表明：刀具失效是由刀具开裂引起的。工作过程中刀具表面产生疲劳裂纹,疲劳裂纹在表面不连续缺陷处萌生并扩展。而失效零件粗糙的表面是裂纹产生的主要原因。     

数控等离子弧切割多参数的选择与优化控制

数控等离子弧切割是一种经济、实用、高效的先进热切割技术.在数控等离子弧切割工艺参数中,许多参数相互耦合,影响切割质量与切割效率,因此,切割参数的选择及控制是一个重要的问题.通过对数控等离子弧切割的加工工艺进行分析,对等离子弧切割的空载电压、弧柱电压、切割电流、切割速度、工作介质及流量、喷嘴距工件的高度、喷孔直径、电极内...     

热应力作用下碳化钨基钢结硬质合金梯形裂纹的形成机理

在自约束型热疲劳试验机上对碳化钨含量不同的钢结硬质合金进行了热疲劳试验，用金相显微镜和扫描电镜对热疲劳裂纹扩展行为进行了研究。结果表明：在热应力作用下，不仅在合金的表面，在合金的内部都形成了“梯形”裂纹。这种形态的裂纹是由试样缺口处的热疲劳裂纹扩展而引起的，合金中的钢基体相阻碍裂纹扩展，而WC硬质相诱导裂纹扩展，这两种因素的综合作用促使热疲劳裂纹成“梯形”扩展。分析认为：使WC粒子在钢基体中均匀分布，提高钢基体的热疲劳抗力，从而来阻止梯形裂纹的形成，是提高碳化钨钢锆硬质合金抗热疲劳性能的有效途径。