Formability predictions of Ti6Al4V titanium alloy sheets deformed at room temperature and 600 °C, using D-Bressan’s shear stress rupture criterion and the critical strain gradient macroscopic modelling are presented and discussed in relation to limit strain results obtained experimentally. Ti6Al4V Forming Limit Strain Curves were predicted and compared with experimental curves at 25 °C and 600 °C and strain rate 0.1 s⁻¹. The analytical models were calibrated by means of tensile tests performed on samples cut at 0°, 45° and 90° to the rolling direction at different temperatures and strain rates to obtain the Lankford coefficients and material strain and strain rate hardening behavior. The applied critical shear stress rupture criterion showed to give a fairly good fit with experimental limit strains outcomes, proving that the shear stress rupture nature of specimens deformed at room and elevated temperatures were well reproduced, despite a not-null strain rate sensitivity coefficient at 600 °C. Fracture occurrence by fast shear stress mechanism through thickness direction was corroborated by experimental fractograph observations close to fracture surfaces. It was shown that predicted limiting major true strain of fracture by shear stress curve is governed by normal anisotropy, strain hardening exponent, pre-strain and normalized critical shear stress parameter, which depends on temperature and strain rate whereas the strain hardening exponent depends largely on temperature. In contrast, the critical strain gradient modelling for onset of localized necking showed poor correlation with the experimental limit strains. Best fit of the critical shear stress criterion with experimental limit strain curves was given by specimens deformed near plane strain or FLC_o. Hence, a common feature of various strain-rate independent metals, annealed or cold rolled, is that the main fracture mechanism of thin sheet metals can be considered as fast shear stress through sheet thickness without a visible localized necking in biaxial stretching.

利用D-Bressan的剪切应力断裂准则和临界应变梯度宏观模型，对Ti6Al4V钛合金板在室温和600°C时变形的可成形性预测进行了讨论，并与实验得出的极限应变结果进行了讨论。预测了Ti6Al4V的成形极限应变曲线，并将其与在25°C和600°C且应变速率为0.1 s ^-1的实验曲线进行比较。通过对在不同温度和应变速率下沿轧制方向在0°，45°和90°切割的样品进行拉伸试验，对分析模型进行校准，以获得Lankford系数以及材料的应变和应变速率硬化行为。所应用的临界剪切应力破裂准则显示出与实验极限应变结果相当吻合，证明了尽管在600处应变率敏感性系数不为零，但在室温和高温下变形的试样的剪切应力破裂性质仍能很好地再现。 ℃。通过沿断裂方向的快速剪切应力机理在断裂表面附近证实断裂的发生得到了证实。结果表明，由剪应力曲线预测的极限极限真实断裂应变受法向各向异性，应变硬化指数，预应变和归一化临界剪切应力参数的控制，这取决于温度和应变速率，而应变硬化指数主要取决于温度。相反，用于局部颈缩发生的临界应变梯度模型显示与实验极限应变的相关性较差。临界剪切应力准则与实验极限应变曲线的最佳拟合是由在平面应变或FLC附近变形的试样给出的 局部颈缩开始的临界应变梯度模型显示与实验极限应变的相关性较差。临界剪切应力准则与实验极限应变曲线的最佳拟合是由在平面应变或FLC附近变形的试样给出的 局部颈缩开始的临界应变梯度模型显示与实验极限应变的相关性较差。临界剪切应力准则与实验极限应变曲线的最佳拟合是由在平面应变或FLC附近变形的试样给出的_Ø。因此，退火或冷轧各种应变速率无关的金属的共同特征是，薄板金属的主要断裂机理可以被认为是贯穿板厚的快速剪切应力，而在双轴拉伸中没有明显的局部颈缩。