辐射松层板抗弯性能的指接参数优化及无损检测研究

叶琦; 管成; 张厚江; 龚迎春; 隋永峰; 刘丽阁

doi:10.12171/j.1000-1522.20210351

辐射松层板抗弯性能的指接参数优化及无损检测研究

Optimization of finger joint parameters and nondestructive testing of bending properties of radiata pine laminates

摘要

摘要:
目的通过对辐射松层板指接工艺的研究，优化指接过程中的参数，提高指接层板的力学性能；基于应力波方法，开展对指接层板抗弯性能的无损检测研究，提高指接层板的强度稳定性。
方法通过预试验过程确定端压，选择4种不同指长的铣刀，设定3种不同嵌合度大小，研究3因素对指接层板抗弯性能的影响，进而从中选出较优指接参数组合并与标准比对；采用应力波方法检测试件动态弹性模量，并分析密度与动态弹性模量两种无损检测参数与静态弹性模量、抗弯强度两种抗弯性能参数的关系，通过检测层板的密度、动态弹性模量对其抗弯性能进行评估。
结果指接参数对抗弯强度存在较大影响，其中指长与嵌合度对抗弯强度存在一定影响，端压对抗弯强度影响不大；本试验范围内，较优指接参数组合辐射松层板抗弯强度均值可达到29.80 MPa，标准值为20.64 MPa，静态弹性模量为8 533 MPa；试件动态弹性模量与静态弹性模量、抗弯强度和层板密度与静态弹性模量、抗弯强度之间均存在显著相关关系，其中使用动态弹性模量评估层板抗弯性能的预测模型要显著优于基于密度的预测模型。
结论基于端压–位移曲线理论，本研究给出的辐射松结构集成材较优指接参数组合为指长15 mm、齿顶宽0.8 mm、齿底宽0.7 mm、齿根宽3.3 mm、斜度1/12.90、嵌合度0.1 mm、端压11 ~ 17 MPa。基于应力波检测动态弹性模量的方法能够较好地评估指接后辐射松层板的抗弯性能。

Abstract:
Objective By the research of finger joint technology of radiated pine laminates, the parameters in finger joint process were optimized and the mechanical properties were improved. Based on the stress wave method, the bending properties of finger joint laminates were studied nondestructively and the strength stability of finger joint laminates was enhanced.
Method The influence of three factors on the laminate mechanical properties was studied with ending pressure determined by pre-experiment process, four milling cutters selected with different finger lengths, three different chimerism degree and finally compared with the standard. The dynamic elastic modulus of the specimens was measured by stress wave method, and the relationship between the two non-destructive testing parameters of density and dynamic elastic modulus and the two bending property parameters of static elastic modulus and bending strength were analyzed. And the bending properties of the laminates were evaluated by testing the density and dynamic modulus of elasticity.
Result The finger joint parameters had great effect on the bending strength. The finger length and chimerism degree had a degree of effect on the bending strength, while the ending pressure had little effect; within the scope of this experiment, the mean value of bending strength of radiata pine laminates with better finger joint parameters could reach 29.80 MPa, while the standard value of bending strength was 20.64 MPa and the static modulus of elasticity was 8 533 MPa; the density and dynamic elastic modulus of the specimens were significantly correlated with the dynamic elastic modulus and bending strength, and the prediction model using dynamic elastic modulus to evaluate the bending properties of the laminates was significantly better than the density-based prediction model.
Conclusion Based on the end-pressure-displacement curve theory, the optimal combination of finger joint parameters for structural glued laminated timber of radiated pine was obtained as follows: finger length 15 mm, tooth tip width 0.8 mm, tooth base width 0.7 mm, tooth root width 3.3 mm, inclination ratio 1/12.90, chimerism degree 0.1 mm, and end pressure 11−17 MPa. The dynamic elastic modulus measurement method based on stress wave can evaluate the bending properties of finger-jointed radiata pine laminates well.

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