疲劳试验机的工作原理，您了解吗？

Do you know the working principle of the fatigue testing machine?

疲劳试验机用于进行测定金属、合金材料及其构件（如操作关节、固接件、螺旋运动件等）在室温状态下的拉伸、压缩或拉压交变负荷的疲劳特性、疲劳寿命、预制裂纹及裂纹扩展试验。高频疲劳试验机在配备相应试验夹具后，可进行正弦载荷下的三点弯曲试验、四点弯曲试验、薄板材拉伸试验、厚板材拉伸试验、强化钢条拉伸试验、链条拉伸试验、固接件试验、连杆试验、扭转疲劳试验、弯扭复合疲劳试验、交互弯曲疲劳试验、CT试验、CCT试验、齿轮疲劳试验等。疲劳试验机特点是可以实现高负荷、高频率、低消耗，从而缩短试验时间，降低试验费用。

Fatigue testing machine is used to test the fatigue properties, fatigue life, prefabricated cracks and crack propagation tests of metal, alloy materials and their components, such as joints, solid joints, spiral moving parts, etc. at room temperature. The high frequency fatigue testing machine can carry out three point bending test, four point bending test, sheet metal tensile test, thick sheet tensile test, tensile test of reinforced steel strip, tensile test of steel strip, tensile test of steel chain, solid joint test, connecting rod test, torsion fatigue test, torsional torsional fatigue test, and bending and torsion test under sine load. , interactive bending fatigue test, CT test, CCT test, gear fatigue test and so on. The fatigue testing machine is characterized by high load, high frequency and low consumption, thereby shortening the test time and reducing the cost of testing.

动态分割图

Dynamic segmentation graph

疲劳试验机的工作原理

Working principle of fatigue testing machine

疲劳试验机根据电磁谐振的原理工作，依靠电磁铁的震荡施加载荷，载荷比较大20KN-300KN，频率80-250HZ测试时间短的首选。需要调频率，频率时固定几个档，根据使用客户的反馈，调频操作比较麻烦。

According to the principle of electromagnetic resonance, the fatigue testing machine relies on the shock of electromagnet to load the load. The load is relatively large 20KN-300KN, and the frequency 80-250HZ test time is the first choice. It is necessary to adjust the frequency and fix several files in frequency. According to the feedback from customers, FM operation is more troublesome.

低频疲劳试验机根据电液伺服的原理工作，依靠液压作动缸的往复运动施加载荷，大载荷5KN-1000KN低频率0-10HZ的首选，一般建议在10HZ左右使用，更高的频率对于液压伺服阀、密封圈等等部件的摩擦损伤太大，后面的维护成本太高，不建议使用更高频率。如果不考虑维护成本，使用20HZ，30HZ也是可以的，只是液压疲劳试验机的寿命会受到重大的影响。

Low frequency fatigue testing machine works according to the principle of electro-hydraulic servo. It depends on the reciprocating motion of hydraulic cylinder, the first choice of 5KN-1000KN low frequency 0-10HZ of large load is generally recommended to be used around 10HZ. The higher frequency is too high for the friction and friction of the hydraulic servo valve, seal ring and so on, and the maintenance cost is too high. It is not recommended to use higher frequency. If the cost of maintenance is not considered, it is also possible to use 20HZ and 30HZ, but the life of the hydraulic fatigue testing machine will be greatly affected.

疲劳强速测算方法

Calculation method of fatigue strength

零件的疲劳寿命与零件的应力、应变水平有关，它们之间的关系可以用应力一寿命曲线（σ-N曲线）和应变一寿命曲线（δ－Ν曲线）表示。应力一寿命曲线和应变一寿命曲线，统称为S-N曲线。根据试验可得其数学表达式：

The fatigue life of parts is related to the stress and strain level of the parts. The relationship between them can be expressed by the stress-life curve (the sigma -N curve) and the strain life curve (delta curve). The stress life curve and strain life curve are collectively referred to as S-N curves. The mathematical expressions can be obtained according to the experiment.

σmN=C

Sigma mN=C

式中：N应力循环数； m、C材料常数。

In the formula: N stress cycle number, m, C material constant.

在疲劳试验中，实际零件尺寸和表面状态与试样有差异，常存在由圆角、键槽等引起的应力集中，所以，在使用时必须引入应力集中系数K、尺寸系数ε和表面系数β。

In fatigue test, the size and surface state of the actual parts are different from those of the sample. There is often a stress concentration caused by the round angle and keyway. Therefore, the stress concentration coefficient K, the dimension coefficient, and the surface coefficient beta must be introduced.