THE BOLTED JOINT IS PRELOADED!螺栓连接 有预加负载
And what is the consequence of this diffference?
1-20
AC tightening technique
Question
What is the major difference between a bolted joint on one hand and a welded, glued or riveted joint on the other hand?
• Turning the nut or screw stretches the screw(旋转螺母或 者螺栓拉深螺栓)
Clamping force
• Stretching the screw clamps the parts together(拉伸螺栓保证工件 夹紧)
Tension
• 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)
AC tightening technique
Why use bolted joints?为什么使用螺栓连
接
It’s so easy that a child can do it
• Easy and quick assembly(简单方便)
• Can be disassembled and reassembled(可以拆卸和重新装配)
1-11
AC tightening technique
ton
= 10 kN
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?
1-12
AC tightening technique
The Correct answer is: 正确的答案是:
INTERESTING – BUT WHAT IS THE VALUE OF THAT? 意义-但是这个价值是什么
1-22
AC tightening technique
Variations in external loads are only to a small extent transferred to the bolt => The fatigue resistance of the bolt becomes very high
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
28
AC tightening technique
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。
29
AC tightening technique
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
螺拴与连接件的关系
拉伸弹簧＋ 压紧弹簧
1-32
AC tightening technique
连接件图
螺拴和连接的变形
压力
力
连接件压 缩
压缩量
1-33
AC tightening technique
连接件图
拉力 螺栓拉伸
伸长量
螺栓连接的变形关系
夹紧力
预 紧 力
1-34
AC tightening technique
1-15
AC tightening technique
The Joint Loaded by an Applied Force连接负载被一应用的力产生
1-16
AC tightening technique
The Joint Loaded by an Applied Force
Zero clamp at the
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.
螺栓伸长δ1
连接件 压缩δ2
变形
连接图解
轴向工作载荷的影响
1-35
AC tightening technique
力
螺栓受力
增加部分
工
夹紧力
作 载
减少部分 荷
σδ1
δ1
δ2
变形
Joint Diagrams 连接图解
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
20 kN – the bolt pretension will NOT change (much)螺栓上承受的拉伸力 是不会变化的
1-13
AC tightening technique
The Special Fastener 特殊模式
1-14
AC tightening technique
The Use of the Special Fastener拧紧这个模式
1-21
AC tightening technique
Question
What is the major difference between a bolted joint on one hand and a welded, glued or riveted joint on the other hand?
1-5
AC tightening technique
Clamping force vs tensile load and shear load夹紧力和 螺栓张力和剪切力
Tensile load
Clamping force
Shear load
Shear load
1-6
AC tightening technique
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
1-23
AC tightening technique
螺栓连接的受力
剪切
1-24
AC tightening technique
拉伸
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
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!
interface. 界面中没有夹
紧
1-17
AC tightening technique
The Joint Loaded by an Applied Force
1-18
AC tightening technique
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
The applied torque is measured应用力矩
1-37
AC tightening technique
Clamping force Needed需要的夹紧力
Torque T=Fxr
F
Ta
Tb
1-38
AC tightening technique
r
F
Ta=Fr
Tb= ½ Fr
Result: Ta= 2 Tb
30
AC tightening technique
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。
31
AC tightening technique
• 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)
1-4
AC tightening technique
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)
1-25
AC tightening technique
施加的力不要超过使用极限
• 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
N 夹紧力
1-26
AC tightening technique