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采用最大m值法拉伸试验获得了随应变变化的最佳应变速率关系曲线,以控制钣金超塑胀形气压加载,使得板料变形集中部位的实际等效应变速率等于变化的最佳应变速率,而非等于恒应变速率拉伸获得的最佳应变速率定值,从而获得比目前基于恒应变速率超塑胀性更优良的成形性能。以2A12铝合金为研究对象,采用最大m值法拉伸实验获得其最佳应变速率关系曲线,以控制超塑性胀形,并与恒应变速率胀形进行比较;为改善壁厚均匀性,设计了正反胀形模具与工艺,并结合有限元软件MSC.Marc 2010,对整流罩进行单向和正反向胀形模拟,并进行实验验证。结果表明,对于单向胀形,基于最大m值法的简化应变速率胀形,其成形时间仅为760s,较恒应变速率胀形3 360s大幅缩短,而二者的减薄率分别为70.4%和70.9%,在降低减薄率的同时,极大的提高了胀形效率;基于最大m值法的简化应变速率正反胀形,零件最小壁厚为1.157mm,较基于最大m值法的简化应变速率单向胀形零件的最小壁厚0.887mm有一定程度增加,而不均匀性则由69.97%降为28.9%,有效改善了壁厚均匀性;实验证明,采用最大m值法的胀形件的最小壁厚有所提高,均匀性得到了有效改善,且壁厚分布与模拟结果相吻合。
The maximum strain rate tensile test results obtained with the strain rate of the best strain rate curve to control the sheet metal superplastic bulging pressure, so that the effective part of the sheet deformation equivalent strain rate equal to the change of the best strain Rather than the best strain rate setting obtained at constant strain rate stretch, resulting in a more formative performance than the current superplasticity based on constant strain rate. Taking 2A12 aluminum alloy as the research object, the best strain rate curve was obtained by the maximum m-value tensile test to control the superplastic bulging and compared with constant strain rate bulging. In order to improve the thickness uniformity, The positive and negative bulging mold and process, and combined with finite element software MSC.Marc 2010, the fairing unidirectional and positive and negative bulging simulation, and experimental verification. The results show that for the uniaxial bulging, the simplified strain rate bulging based on the maximum m-value method has a forming time of only 760 s, which is significantly shorter than the constant bulging rate of 3 360 s, and the thinning rates of the two are 70.4% And 70.9%, respectively. While reducing the thinning rate, the bulging efficiency was greatly improved. Based on the maximum m-value method, the minimum strain wall thickness of the part was 1.157mm, which was higher than that based on the maximum m value The minimum wall thickness of the simplified strain rate uniaxial bulge-shaped parts is 0.887mm, while the non-uniformity is reduced from 69.97% to 28.9%, which effectively improves the uniformity of wall thickness. Experiments show that the maximum m value expansion The minimum wall thickness of the shaped part is improved, the uniformity is effectively improved, and the wall thickness distribution is in accordance with the simulation result.