身管弹膛和线膛同锻时下沉段皱褶试验研究及其预测

身管弹膛和线膛同锻技术可用径向精锻工艺同时锻出弹膛和线膛，将彻底解决身管弹膛和线膛的同轴度问题，改善坡膛部位的表面粗糙度。为提高身管内膛的加工质量，以身管弹膛和线膛同锻为对象，研究下沉段和锻造段产生的褶皱以及演变情况。通过对身管径向锻打试验和形貌试验分析处理，发现弹膛和线膛同锻时：下沉段将会产生褶皱，并且褶皱随着变形的增加，深度不断加深；当进入锻造段后，部分皱褶被打平，变成了身管微裂纹。应用有限元分析软件Abaqus对身管锻打过程进行仿真，发现锻打过程中下沉段径向应变ε_r和周向应变ε_θ的比值SX(]ε_r]ε_θSX)]为定值，不同锻打工艺参数下应变比值不同。研究结果表明：身管下沉段单次锻打产生的褶皱深度Δd_w可以用径向应变ε_r和周向应变ε_θ的比值SX(]ε_r]ε_θSX)]来表示，拟合的关系式为Δd_w=0.058 8SX(]ε_r]ε_θSX)]+0.052 1；结合锻打所需的锤数可以预测出下沉段结束位置的皱褶深度，皱褶深度的预测有助于防止褶皱在锻造段挤压形成锻造身管的微裂纹。

The Experimental Study and Prediction of Wrinkles in Sinking Zone of Barrel Forged with Chamber and Rifled Bore

The radial forging process for both chamber and rifled bore is used to improve the coaxiality of rifled bore and the surface quality of chamber. The wrinkles may be formed on the inner surface of barrel during forging. The formation of wrinkles and their evolution are studied. The scanning electron microscope is used to check the inner surface of forged barrel. The results show that the wrinkles are formed in the sinking zone firstly during the radial forging processing. With the increase in deformation, the depth of wrinkles becomes bigger gradually. When the sinking zone turnes to the forging zone, some wrinkles are smoothed under the resistance of the mandrel. Nevertheless, some wrinkles are too deep to smooth and be turned to the fissures. The finite element software ABAQUS is used to simulate the forging process of barrel. It is found that the ratio of radial strain and circumferential strain is nearly same in the sinking zone, and the strain ratio is determined from the forging process parameters. The results show that the wrinkle depth per stroke can be expressed by the ratio of radial strain and circumferential strain SX(]ε_r]ε_θSX)], and the fitted relational expression is Δd_w=0.058 8SX(]ε_r]ε_θSX)]+0.052 1. The total depth of wrinkles can be predicted from the number of the stroke required for whole sinking zone and the value of Δdw. The prediction of wrinkle depth helps to prevent the wrinkles from being squeezed into fissure in the forging zone. Key