基于MM-ALE方法的刚性脚在软土中的沉陷特性研究

为研究刚性机器人脚的形状对其在软土中沉陷特性的影响,以MAT147材料作为土壤本构模型,采用多物质ALE方法对刚性脚在土壤中的沉陷过程进行数值模拟.分别对刚性脚脚底有无孔洞对软土的应力分布和流动状态的影响进行了分析,结果表明,脚部在沉陷过程中,最大有效应力分布在脚底部边缘的正下方区域,刚性脚轮廓外围土壤的应力由大到小沿脚部轮廓向外发散.孔洞改变了脚部正下方土壤的应力分布,与无孔洞脚相比,带孔洞脚底正下方土壤应力在孔洞周围呈环形分布,深度方向上的应力分布相对均匀.孔洞还改变了土壤的流动状态,使得流向脚底部的土壤增多,密度增大,对脚部防陷有积极影响.对不同孔洞半径大小对刚性脚在软土中沉陷特性的影响也进行了比较,结果表明,相等底面积情况下,随着孔洞半径的增大,十字形凹陷处的应力也增大,脚底两倍圆孔半径范围内的应力分布越均匀,而对侧面土壤影响较小;孔洞半径影响了脚底土壤的流动状态,速度方向随着半径的增大由竖直向下变为竖直向上,土壤流速与孔的半径大小呈正相关,而同等压力情况下沉陷深度与孔洞半径大小呈负相关.

Study on the sinkage behavior of legged robot in soft soil based on MM-ALE method

In order to analyze the influence of rigid foot's geometry shape of legged robot on the sinking process in soft soil, it uses MAT 147 material as the constitutive model of soil and realizes the dynamic simulation of rigid foot′s sinking process with Multi Material Arbitrary Lagrangian Eulerian ( MM-ALE) method.It obtains the influ-ence of holes at the bottom of rigid foot on the stress distributions and flow trend of soft soil.The results show that the maximum effective stress of soil concentrates at the bottom of the rigid foot near the edge and the effective stress divergs outwardly along the foot contour.Comparing to the foot with no holes, the holes at the bottom of foot change the stress distribution.The stress just below the foot is distributed annular around the hole and it is more u-niform in the depth direction.The flow trend of soil is also influenced by holes.More soil is flow into the bottom of foot and the density increased obviously.It presents the relationship between hole's radius and the stress distribu-tion in the horizontal and vertical direction are studied and the soft soil flow trend.The results indicate that at the same bottom area, the bigger the hole's radius is, the bigger the stress at the depression of cross-shape is.It shows that with the increase of the radius, the speed direction is turned downward to upward, the sinking depth has a negative correlation with hole's radius under the same pressure, while the speed of soil is opposite.