AtlasCopco基本拧紧技术.ppt

1-1,BASIC TIGHTENING TECHNIQUE 基本拧紧技术,AC Tightening Technique 阿特拉斯科普柯拧紧技术,1-2,基本拧紧技术,介绍装配过程中的基本问题，为正确和使用选择工具提供指导,对客户来讲，成功的关键是所使用的工具设备能够匹配其特定需要,1-3,Different ways of assembling装配的不同方法,Welding(焊接) Gluing(粘接) Riveting(铆接) Tightening with screws and bolts(螺栓拧紧连接),1-4,Why use bolted joints?为什么使用螺栓连接,Easy and quick assembly(简单方便) Can be disassembled and reassembled(可以拆卸和重新装配) Standardised well-defined element(标准化) Cost-efficient(节省成本) The bolt should be weakest link(设计成最薄弱环节),Its so easy that a child can do it,1-5,The thread creates the clamp load that holds the joint together螺纹建立夹紧载何使得工件被夹紧),Clamping force,Tension,Turning the nut or screw stretches the screw(旋转螺母或者螺栓拉深螺栓) Stretching the screw clamps the parts together(拉伸螺栓保证工件夹紧) The clamp load in the joint is the target of all tightening(夹紧载何就是我们的拧紧的目标),1-6,Clamping force vs tensile load and shear load夹紧力和螺栓张力和剪切力,Clamping force,1-7,This must be avoided!这个必须要避免,Shear load,Shear load,Tension,Tension,1-8,1-9,Bolt tension = 20 kN,1-10,Bolt tension = ?,ton,1-11,Bolt tension = ?,ton,= 10 kN,1-12,Is the bolt tension now approximately 现在螺栓的拉伸力大约是多少?,10 kN? 20 kN? Or 30 kN?,1-13,The Correct answer is: 正确的答案是:,20 kN the bolt pretension will NOT change (much)螺栓上承受的拉伸力是不会变化的,1-14,The Special Fastener 特殊模式,1-15,The Use of the Special Fastener拧紧这个模式,1-16,The Joint Loaded by an Applied Force连接负载被一应用的力产生,1-17,The Joint Loaded by an Applied Force,Zero clamp at the interface. 界面中没有夹紧,1-18,The Joint Loaded by an Applied Force,1-19,Question,What is the major difference between a bolted joint on one hand and a welded, glued or riveted joint on the other hand?螺栓连接和焊接铆接粘接有什么最大的区别 And what is the consequence of this difference?这个不同点有什么重要的,1-20,Question,What is the major difference between a bolted joint on one hand and a welded, glued or riveted joint on the other hand? THE BOLTED JOINT IS PRELOADED!螺栓连接有预加负载 And what is the consequence of this diffference?,1-21,Question,What is the major difference between a bolted joint on one hand and a welded, glued or riveted joint on the other hand? THE BOLTED JOINT IS PRELOADED! And what is the consequence of this diffference? ONLY A SMALL PORTION OF THE EXTERNAL LOAD IS TRANSFERRED TO THE BOLT (until the preload is exceeded) !只有很小的一部分外部负载被转移到螺栓上(直到超过预加负载),1-22,Question,What is the major difference between a bolted joint on one hand and a welded, glued or riveted joint on the other hand? THE BOLTED JOINT IS PRELOADED! And what is the consequence of this diffference? ONLY A SMALL PORTION OF THE EXTERNAL LOAD IS TRANSFERRED TO THE BOLT! INTERESTING BUT WHAT IS THE VALUE OF THAT? 意义-但是这个价值是什么,1-23,Variations in external loads are only to a small extent transferred to the bolt = The fatigue resistance of the bolt becomes very high 外部负载的变化只有很小的一部分会转移到螺栓上=这样螺栓就不容易由于负载的交变而产生疲劳损坏 It provides a frictional grip = It will not come apart if the parts cannot move in relation to each other 提供了一个有摩擦力的夹紧=这将不会出现部件分离如果部件不能有相互的位移,1-24,螺栓连接的受力,剪切,拉伸,1-25,一定要确保施加的扭矩达到最小需要扭矩,夹紧力一定要高于外部载荷 安全余量载荷的影响因素: 振动 摩擦力的变化 连接件尺寸变化 拧紧精度,1-26,施加的力不要超过使用极限,螺栓拉伸量,N 夹紧力,施加的力过大会使螺栓过度伸长 安全余量取决于: 拧紧精度 材料等级,27,螺栓连接应用的历史背景,28,历史背景,十九世纪工业革命开始，为得到更大的生产力要求工业产品必须达到： 系统化 质量可控性 可复制性,29,连接图,德国人Rotscher 在1927年提出了连接图，这种方法直到今天仍在使用，帮助我们理解连接的力学特性和进行计算。,30,VDI 2230， 德国工程师协会 2230标准,基于从1960年代就开始的研究，德国工程师协会(VDI， German Society of Engineers)发布了VDI2230：高负荷连接的系统计算方法 Systematic Calculation of High Duty Joints.,31,VDI 2230使用范围,VDI 2230的应用非常广泛，包括带60度法兰的高强度螺拴，螺丝大小从M4到M39。 它给出的是单螺拴连接的分析指导。由多个螺拴组成的连接，负荷首先要被分配，使每个螺拴上的负荷确定下来。,1-32,连接件图,螺拴与连接件的关系,拉伸弹簧压紧弹簧,1-33,螺拴和连接的变形,1-34,连 接 图 解,螺栓连接的变形关系,夹紧力,变形,预紧力,螺栓伸长1,连接件,压缩2,1-35,Joint Diagrams 连 接 图 解,轴向工作载荷的影响,力,1,2,变形,螺栓受力增加部分,夹紧力 减少部分,1,工作载荷,1-36,通过螺纹产生夹紧力把连接件夹紧,旋转螺母或螺丝使螺丝受力伸长 螺丝伸长产生的夹紧力把连接件夹紧 我们需要的是连接件中的夹紧力,1-37,Torque measurement扭矩测量,The applied torque is measured应用力矩,Clamping force Needed需要的夹紧力,Clamping force is the aim at but it is hard to measure. Torque is easy to measure and apply.夹紧力是目标但是比较难测量但是扭矩 比较容易测量,1-38,Torque T=Fxr,r,F,Ta, r,F,Tb,Result: Ta= 2 Tb,F = applied force (in Newton) r = lever length (in meters),1-39,为了拧紧螺栓, 必须施加力以便拧紧螺母/螺丝,1-40,Clamping force depends on torque and other factors 夹紧力的因素是扭矩和其余的因素,Fm= T/ (0.16P + (g * 0.58 * d2) + (Dkm/2) * k) Definitions: Fm = clamping force夹紧力 P = pitch of thread螺距 g = friction value in thread;螺纹摩擦系数 d2 = diameter bolt螺纹中径 Dkm = size of surface bolt (nut)-head螺栓头小表面尺寸 Dkm = (dw + dh)/2 k = friction value surface bolt-head螺栓头下的摩擦系数,1-41,Friction between thread bolt and thread nut螺纹和螺帽的摩擦力,Clamping force夹紧力,Friction under bolt-head 螺栓头下的摩擦力,50%,40%,Relation between applied torque and clamping force扭矩和摩擦力的关系,1-42,Changing friction: bolt-head螺栓头下的摩擦力变化,Teflon washer塑料惦片,1-43,40 %,20 %,40 %,40%,40%,Teflon washer塑料垫片,Friction between thread bolt and thread nut螺纹和螺帽的摩擦力,Clamping force夹紧力,Friction under bolt-head 螺栓头下的摩擦力,Relation between applied torque and clamping force扭矩和摩擦力的关系,1-44,Less friction:,1-45,Changing friction: bolt-head螺栓头下的摩擦力变化,Locking washer防松垫片,1-46,60%,40%,Locking washer防松垫片,Friction between thread bolt and thread nut,Clamping force,Friction under bolt-head,Relation between applied torque and clamping force扭矩和摩擦力的关系,1-47,More friction,1-48,Changing friction: thread bolt - nut螺纹的摩擦力变化,1-49,50 %,20 %,30 %,50%,30%,Oil on threads,Friction between thread bolt and thread nut,Clamping force,Friction under bolt-head,Relation between applied torque and clamping force,1-50,Less friction:,50 %,20 %,30 %,1-51,Changing friction: thread bolt - nut,1-52,50 %,0 %,50 %,50%,50%,Rusted bolt,Friction between thread bolt and thread nut,Clamping force,Friction under bolt-head,Relation between applied torque and clamping force,1-53,More friction,50 %,0%,50 %,1-54,Other ways of changing the friction?,Liquid loctite液体乐泰螺纹胶 Locknut防松螺帽 Paint in the threads螺纹中含有油漆 Damaged threads损坏的螺纹 Welding pearls焊渣 Bolt finishing (Cr6, Dacromet, etc.),1-55,Loctite,1-56,Locknut,1-57,Paint on the threads,1-58,Damaged threads,1-59,50-40-10 规则,扭矩,100%,90% 的扭矩用于克服摩擦力,夹紧力 10%,螺纹副中 40%,螺栓头下摩擦力 50%,1-60,夹紧力与摩擦力的关系,一般情况下,螺栓头下摩擦力 50%,螺纹副中摩擦力 40%,10%,在螺栓法兰面上加润滑油,螺栓头下摩擦力 45%,螺纹副中摩擦力 40%,夹紧力 15%,螺纹副中有杂质或螺纹受损,螺栓头下摩擦力 50%,螺纹副中摩擦力 45%,5%,1-61,螺栓标识系统,生产商标识 第一个数 = 1/100 的最大抗拉强度 (N/mm2) 1008 = 800 N/mm2 第二个数 =屈服强度与最大抗拉强度之间的关系 0.8 = 80% 两数相乘得出屈服应力 800* 0.8 = 640 N/mm2,公制螺纹,1-62,施加的力不要超过使用极限,螺栓拉伸量,N 夹紧力,施加的力过大会使螺栓过度伸长 安全余量取决于: 拧紧精度 材料等级,1-63,64,软连接和硬连接,65,Torque = OK,夹紧角: ,66,硬连接的定义 (ISO 5393),30 max.,夹紧角,67,硬连接举例,Clamping force,Steep slope,Angle,Low angle displacement,68,720 min.,软连接,软连接的定义 (ISO 5393),69,软连接举例,Clamping force,Soft slope,Angle,High angle displacement,1-70,连接的特性也决定着所需工具的类型(ISO 5393) ,旋转角度,目标扭矩,A. 硬连接：到达贴合点后，旋转30以内达到目标扭矩的连接。 B. 软连接：到达贴合点后，旋转2 圈（720）以上达到目标扭矩的连接。 扭矩的过扭程度受连接件硬度以及工具转速影响。,软连接、硬连接,30,720,71,硬连接 30 deg (ISO 5393),软连接 720 deg (ISO 5393),X Nm,X Nm, 30, 720,72,扭矩过冲,10 Nm,9 Nm,工具虽然设定都是9Nm，但是针对不同性质的连接会产生不同的结果,1-73,软、硬连接,目标,均值偏差,扭矩,角度,过扭,贴合点,硬连接,软连接,1-74,如何在一个连接件上测量扭矩,动态扭矩:在拧紧螺栓的同时用在线式扭矩传感器测量。 静态扭矩:安装后用扭矩扳手测量。,1-75,静态扭矩,动力工具 输出扭矩 92 94 91 92 94 92 92 X=92,43 =1,13,扭力扳手 静态扭矩 103 106 103 100 100 103 100 X=102,14 =2,27,T (Nm),时间,20,40,60,80,100,110,120,(A)工具输出 (动态扭矩),(B) 扭力扳手 (静态扭矩),原因:静态摩擦力,76,硬连接上由于较高的静态摩擦力，静态扭矩可比动态扭矩要高。右下图中倒V的拐点即是扭力扳手测得的硬连接上的静态扭矩,1-77,装配 手测 (动态) (静态) 102.6 112 102.6 110 101.4 111 101.2 110 102.4 113 100.9 109 102.1 110 102.4 111 101.0 113 101.8 112 101.84 111.1 0.67 1.4 2.01 4.1,均值 标准偏差 (Sigma) 3 Sigma,硬连接,78,软连接静态扭矩较动态扭矩要偏小，原因是衰减。VDI2230里系统的方法设置螺拴即有计算扭矩衰减这一步骤,79,If we look at what happens to the surface in contact with the threads and under the head, we will notice that locally the load can be extremely high, far exceeding yield and these areas will collapse (embedment). Embedment reduces the clamping force because the elongation of the bolt is reduced.,Very high load,Average load (80% of yield),扭矩衰减, copyright BLM s.a.s - 24 giugno 2004,80,扭矩衰减的原因呢 连接的嵌入,81,82,Calculation Step R4 - Establishing Preload Losses 计算步骤R4确定预加负荷损失,losses.由于局部嵌入和不同的热膨胀特性，螺拴预加负荷可能会损失,Aluminium Joint,Steel Bolt,1-83,弹性衰减会影响夹紧力,材料弹性衰减会使夹紧力衰减!,Time,1-84,均值 标准偏差 (Sigma) 3 Sigma,装配 手测 (动态) (静态) 100.2 88 100.5 84 100.7 92 100.3 86 100.4 90 100.8 88 100.5 86 100.2 85 100.2 84 100.4 84 100.42 86.7 0.21 2.8 0.63 8.3,软连接,1-85,衰减,60-70%的衰减发生在30毫秒以内,时间,牛米,衰减,断气,1-86,扭矩和角度 OK,扭矩,角度,扭矩 = OK 角度 = OK,1-87,结论：,Clamp force,Friction in threads,Friction under nut or head,螺栓装配质量对产品的最终质量有着直接影响,为了得到质量合格的拧紧连接 拧紧扭矩必须精确 连接件质量必须得到监控,88,拧紧方法的分类按工具控制方式,基于扭矩或角度: 弹性范围内: 扭矩控制 角度控制 连接控制 超出弹性范围 角度控制 梯度(扭矩变化率)控制，即屈服点控制 其他方式 超声波 机械测试伸长量,89,夹紧力,角度,扭矩,角度,螺拴连接模型,90,夹紧力,扭矩,角度,角度,螺拴连接模型塑性变形阶段,91,扭矩控制,92,扭矩控制方式利用的是人们熟知的扭矩与张紧力之间的关系公式。扭矩控制方式在出现最大摩擦系数和最小力率(Force Rate)时提供最小的夹紧力，反之亦然。,扭矩控制,93,优势: 容易实现不同精度等级的控制+/-25%的脉冲型工具到+/-1%的拧紧轴 巨量的产品和过程设计的标准数据-历史悠久 过程和设备的有效性校验过程非常容易 工程师非常熟悉，广为人知,扭矩控制,94,Tightening Methods,劣势: 夹紧力的精度很差,可能到+/- 60 %,受摩擦系数影响大 没有根本办法防止螺拴断裂 以上两个原因导致螺拴能力利用率低 60%