(一) 疲劳试验分类疲劳试验按试验对象可以分为材料疲劳试验和结构疲劳试验。材料疲劳试验使用标准试样或非标准试样进行疲劳试验，结构疲劳试验使用模型、全尺寸零部件乃至整机进行疲劳试验。按失效循环数可以分为高周疲劳试验和低周疲劳试验。失效循环次数大于5×104的称为高周疲劳试验；失效循环数小于5×104的称为低周疲劳试验。按应力比可以分为对称疲劳试验（R=-1）和非对称疲劳试验（R≠-1）。
（1） According to the test object, fatigue test can be divided into material fatigue test and structural fatigue test. Standard or non-standard samples are used for material fatigue test, and model, full-scale parts and even whole machine are used for structural fatigue test. According to the number of failure cycles, it can be divided into high cycle fatigue test and low cycle fatigue test. High cycle fatigue test is called when the number of failure cycles is more than 5 & times; 104; and it is called low cycle fatigue test if the number of failure cycles is less than 5 & times; 104. According to the stress ratio, it can be divided into symmetrical fatigue test (r = - 1) and asymmetric fatigue test (R & ne; - 1).
非对称疲劳试验又分为单向加载疲劳试验（Rgt;0）和双向加载疲劳试验（Rlt;1）。单向加载疲劳试验（R=0或R=∞）又分为脉动疲劳试验和波动疲劳试验（0lt;R∞）。按循环波形可以分为：正弦波、三角波、梯形波、方波和随机波。循环波形确定了加载速率与在最大应力下停留的时间，对室温高周疲劳试验影响不大，对高温蠕变疲劳试验则有较大影响。低周疲劳试验时，迟滞回线与循环波形密切相关，这时循环波形对裂纹形成寿命有较大影响，但对裂纹扩展寿命影响不大。
Asymmetric fatigue test is divided into unidirectional loading fatigue test (RGT; 0) and bidirectional loading fatigue test (RLT; 1). The unidirectional loading fatigue test (r = 0 or r = & infin;) is divided into pulsation fatigue test and wave fatigue test (0lt; R & infin;). According to the cyclic waveform, it can be divided into sine wave, triangle wave, trapezoidal wave, square wave and random wave. The cyclic waveform determines the loading rate and residence time under the maximum stress, which has little effect on the high cycle fatigue test at room temperature, but has a great influence on the high temperature creep fatigue test. In the low cycle fatigue test, the hysteresis loop is closely related to the cyclic waveform, and the cyclic waveform has a great influence on the crack formation life, but has little effect on the crack growth life.
在焊接疲劳试验时，将三角波变为方波时疲劳寿命有所降低。按加载控制方式可以分为：柔性加载和刚性加载。柔性加载采用载荷控制，刚性加载采用位移控制。柔性加载时，在整个试验过程中载荷保持恒定，而运动位移不受限制。刚性加载时，在整个试验期间，运动位移保持不变，而载荷随系统刚度的变化而变化。
In the welding fatigue test, the fatigue life decreases when the triangular wave is changed into square wave. According to the loading control mode, it can be divided into flexible loading and rigid loading. Flexible loading is controlled by load, while rigid loading is controlled by displacement. During the flexible loading, the load remains constant during the whole test process, and the movement displacement is not limited. In the case of rigid loading, the movement displacement remains unchanged during the whole test period, while the load changes with the change of system stiffness.
在出现疲劳裂纹以后，载荷控制的加载力不变，其裂纹扩展速率随裂纹长度的增大而不断增大；位移控制试验时，裂纹引起的松弛使加载力降低，其裂纹扩展速率也随之不断降低。因此，载荷控制下的疲劳寿命远远低于位移控制下的疲劳寿命。通常的静定结构相当于载荷控制情况，而有赘余的非静定结构则相当于位移控制情况。按试样的加载方式可以分为：拉—压疲劳试验，弯曲疲劳试验，扭转疲劳试验，复合应力疲劳试验。
After the fatigue crack appears, the loading force controlled by load remains unchanged, and the crack growth rate increases with the increase of crack length; in displacement control test, the relaxation caused by crack reduces the loading force, and the crack growth rate also decreases. Therefore, the fatigue life under load control is much lower than that under displacement control. Generally, the statically determinate structure is equivalent to the load control case, while the non statically determinate structure with redundancy is equivalent to the displacement control case. According to the loading mode of the specimen, it can be divided into tension fatigue test, bending fatigue test, torsion fatigue test and composite stress fatigue test.
弯曲疲劳试验按弯曲的施加方向与试样是否旋转，又可分为旋转弯曲疲劳试验、圆弯曲疲劳试验和平面弯曲疲劳试验；按试样承载情况与加载点，又可分为三点弯曲、四点弯曲与悬臂弯曲疲劳试验。
The bending fatigue test can be divided into rotary bending fatigue test, circular bending fatigue test and plane bending fatigue test according to the bending application direction and whether the specimen rotates; according to the bearing condition and loading point of the specimen, it can be divided into three-point bending, four-point bending and cantilever bending fatigue test.
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