Radial compression response of honeycomb rollers with multi dense degrees for forest harvester
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摘要:
目的 针对为林木采育机而设计的蜂窝进料辊，研究其在采伐时夹紧和翻转工序的模拟工况下，密实度差异对压缩响应的影响。 方法 将15套蜂窝辊按照密实度划分为3种等级，经由理论模型和模拟仿真分析，对多密实度下的力学和吸能特性的变化做量化探究。选出其中3套制备试件，进行线弹性阶段内的径向压缩试验，利用数字图像相关技术对压缩过程中试件的变形进行监测，比较微观上塑性铰处的结点变形，同时对比仿真与试验的结果，进而总结双V附翼蜂窝进料辊的变形模式。 结果 仿真结果显示：平台阶段下随着密实度增长约10%，蜂窝辊的等效应力上升幅度处于2 MPa以内，但吸能量则提升了近乎6倍。试验结果表明：线弹性阶段下相同幅度的密实度提升，虽然导致质量增大约59.78%，但接触力却获得约3.4倍的提升。变形观测后提出准静态压缩下的V型变形模式，在离散系数低于6%的情况下获得了验证。 结论 蜂窝辊在密实度为0.25 ~ 0.40范围内的压缩响应表现为：以壁厚和层数为主要变量的密实度分别与等效应力和吸能量均具有显著非线性的正相关关系；在近似密实度下，增加壁厚，有助于获得更高的抗压强度，减少层数则促进了吸能特性的提升；双 V附翼蜂窝进料辊在周向的变形机制显露出不均匀的拉胀现象。 Abstract:Objective The radial compression response of honeycomb rollers with multi dense degrees for forest harvester was studied under simulated working conditions, that is, clamping and overturning process during logging. Method 15 kinds of rollers were divided into three grades according to different dense degrees. In order to obtain the quantitative exploration of mechanical and energy absorption characteristics, a combined theoretical and numerical study was designed. Then 3 of them was selected for manufacturing, and radial compression tests in linear elasticity phase were carried out. After monitoring with digital image correlation technology, the node deformation at the plastic hinge was compared. By comparing the results of simulation and test, the deformation mode of roller of double V-wing honeycomb (RDVH) with multi dense degrees was studied. Result The simulation results in the platform stage showed that, with the increase of dense degree by about 10%, the increase of equivalent stress of honeycomb roll was within 2 MPa, but the energy absorption increased by nearly 6 times. The test results in the linear elastic stage showed that the same increase in dense degree acted as a trigger for a mass increase of 59.78%, while it had largely led to the promotion of contact force to about 3.4 times. The V mode deformation pattern was proposed in this work, which could be verified when the dispersion coefficient was less than 6%. Conclusion The compression response of RDVH with dense degrees in the range of 25%−40% could be shown as follows: to begin with, the dense degree, which is significantly induced by wall thickness and number of layers, has a remarkable nonlinear positive correlation with equivalent stress and energy absorption. Furthermore, under approximate dense degrees, the increase of wall thickness could be capable to meet higher compressive strength, while the decrease of the number of layers would contribute to the improvement of energy absorption. Finally, the deformation mechanism of RDVH in circumferential directions shows uneven auxeticity. -
图 1 蜂窝进料辊的示意图
t为壁厚、l为胞元半宽、θ1为下胞角、θ2为上胞角、θR为附翼角、lf为附翼半宽、 L为层数、N为胞元个数、R为辊外径、R0为辊内径、T为辊宽、c为联结量。t is wall thickness, l is cell half-width, θ1 is angle at the lower part of cell, θ2 is angle at the upper part of cell, θR is wing angle, lf is wing half-width, L is number of layers, N is number of cells, R is outer radius of roller, R0 is inner radius of roller, T is roller width, and c is connection quantity.
Figure 1. Schematic diagram of honeycomb feeding roller
图 2 不同密实度的蜂窝进料辊的仿真模拟
Figure 2. Simulation of the honeycomb feeding rollers with different dense degrees
图 3 蜂窝辊的等效应力和吸能量拟合曲线
σ1、σ2、σ3、σ4分别代表层数为1、2、3、4的辊的等效应力; e1、e2、e3、e4分别代表层数为1、2、3、4的辊的吸能量; Fσ1、Fσ2分别代表层数为1、2的辊的等效应力拟合曲线; Fe1、Fe2分别代表层数为1、2的辊的吸能量拟合曲线。σ1, σ2, σ3, σ4 represent the equivalent stress of rollers with 1, 2, 3 and 4 layers, respectively; e1, e2, e3, e4 represent the energy absorption of rolls with 1, 2, 3 and 4 layers, respectively; Fσ1, Fσ2 represent the equivalent stress fitting curves of rolls with 1 and 2 layers, respectively; Fe1, Fe2 represent the absorbed energy fitting curves of rolls with 1 and 2 layers, respectively.
Figure 3. Equivalent stress and absorbed energy fitting curves of honeycomb rollers
图 4 压缩试验相关设备搭建和压缩图像
Figure 4. Construction of equipment related to compression experiment and compressed image
图 5 蜂窝进料辊位移分布云图
Figure 5. Displacement distribution nephograms of double V-wing honeycombs (RDVH)
图 6 双V附翼型蜂窝结构的关键结点
A、B、C、D、E、b、c和e均为加载前的对应区域的结点，A′、B′、C′、D′、E′、b′、c′和e′均为加载后对应区域的结点。A, B, C, D, E, b, c and e are node codes of corresponding areas before loading， A′, B′, C′, D′, E′, b′, c′ and e′ are node codes of corresponding areas after loading.
Figure 6. Key nodes of RDVH
图 7 结点变形量−加载位移曲线
双V附翼型蜂窝辊上结点的命名规则为：结点代号−所属密实度等级，L，M和H分别对应低、中、高密实度辊，A、B、C、D、E分别为结点代号。Naming rule of the node on RDVH is: node code-grade of RDVH. L, M and H correspond to RDVHs with low, medium and high dense degrees, respectively. A, B, C, D and E are node codes, respectively.
Figure 7. Node deformation-loading displacement curves
图 8 多密实度型蜂窝进料辊数值仿真与试验变形结果比较
Figure 8. Comparison between numerical simulation and experimental deformation results of RDVHs with multi dense degrees
图 9 V型模式变形
Ω为内层胞元所在的区域，Li为平行直线系。Ω is the region where the inner cells are located, and Li is a parallel linear system.
Figure 9. V mode deformation pattern
表 1 不同密实度等级的蜂窝进料辊的参数
Table 1. Parameters of honeycomb rollers with different dense degrees
等级
Grade壁厚
Wall thickness/mm外径
Outer radius/mm内径
Inner radius/mm填充面积
Filled area/mm2待填充面积
Area to be filled/mm2密实度
Dense degree低 Low 2.5 151.85 60.00 16297.598 58126.289 0.280 中 Medium 5.0 155.74 60.00 20504.573 61885.284 0.331 高 High 10.0 163.51 60.00 26039.716 69678.232 0.374 
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