In addition to the bending moment caused by the self weight of the cylinder and the weight of the concrete, the mixing cylinder also bears the torque caused by the rotary movement of the mixing cylinder and the circumferential and axial force of the concrete in the mixing cylinder, which is complex [5]. Under the action of cyclic alternating load, the initial micro crack may form in the area with large stress, and then develop into macro crack, and then the macro crack will continue to expand, resulting in the cracking of weld bead or base metal. The main reasons affecting the initial microcracks of the raceway are as follows:
（1）滚道焊缝处的应力集合
(1) Stress concentration at raceway weld
缘由：滚道与筒体焊接时，焊缝处常常呈现应力集合。另外，搅拌筒在利用进程中，滚道与托轮处的集合载荷和滚道截面的全体变形也城市使焊接处呈现应力集合景象。
Cause: when the raceway is welded with the cylinder, stress concentration often occurs at the weld. In addition, during the use of the mixing drum, the concentrated load at the raceway and supporting wheel and the overall deformation of the raceway section will also cause the stress concentration at the welding joint.
对策：打磨应力集合焊缝，从头施焊，对已呈现微观裂纹的焊缝或母材，打孔截断裂纹泉源，从头焊接。
Countermeasures: polish the weld with concentrated stress and re weld. For the weld or base metal with macro cracks, punch holes to cut off the crack source and re weld.
（2）滚道焊缝处的剩余应力
(2) Residual stress at raceway weld
缘由：滚道与筒体刚度相差差异，普通环境下，搅拌筒筒体厚度为6mm 的钢板，滚道的径向厚度在60mm 摆布，筒体和滚道厚度相差很大，在焊接进程中，滚道的热缩短遭到限定，并且在冷却进程中的缩短也遭到限定，而筒体受限水平远小于滚道，终究影响到焊接应力的巨细及散布不均，致使剩余应力的发生。
Reason: the stiffness of the raceway is quite different from that of the barrel. Generally, the radial thickness of the raceway is about 60mm for the steel plate with a thickness of 6mm of the mixing barrel. The thickness of the barrel and the raceway is very different. During the welding process, the thermal expansion of the raceway is limited, and the shrinkage during the cooling process is also limited, and the degree of limitation of the barrel is much less than that of the raceway, Finally, it affects the size and uneven distribution of welding stress, resulting in the generation of residual stress.
对策：调剂焊接挨次，削减单次热量输出，焊接进程顶用紫铜锤敲击构件，接纳振动时效体例调剂、均化、消弭剩余应力。另外，对焊道停止部分打磨，削减焊接缺点。
Countermeasures: adjust the welding sequence, reduce the single heat input, knock the components with a copper hammer during the welding process, and adjust, homogenize and eliminate the residual stress by means of vibration aging. In addition, the weld bead shall be locally polished to reduce welding defects.
（3）滚道与筒体的刚度变更
(3) Stiffness change of raceway and cylinder
缘由：滚道及筒体的刚度跟着车辆的利用呈递加趋向，风雅量打金鱼 尤其较着，刚度的削弱会加快焊道的委靡生效，致使焊道或母材开裂。
Reason: the stiffness of raceway and cylinder decreases with the use of vehicles, especially for large-scale mixer. The weakening of stiffness will accelerate the fatigue failure of weld bead and lead to the cracking of weld bead or base metal.
对策：在滚道与筒体打仗外部增焊加强板，进步该地区的全体刚度，以加强焊接布局的抗委靡生效才能。
Countermeasures: weld reinforcing plates inside the contact between the raceway and the cylinder to improve the overall stiffness of the area, so as to enhance the fatigue failure resistance of the welded structure.
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