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Temperature gradient in wood during grinding

机译：磨削过程中木材的温度梯度

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Grinding is a commonly used method for producing pulps for papermaking, but its rather poor energy efficiency is a drawback. This paper focuses on developing a model dealing with temperature rise in wood during grinding. The model paves the way for the development of theoretical methods which can be used for reducing the energy consumption of the process. In grinding, wood is loaded by grits, which cause stress waves in the wood matrix. The stress waves fatigue the wood and ultimately separate fibres from the matrix, but because of wood's viscoelasticity, part of the mechanical energy of waves is converted into heat. In order to understand the wood temperature increase in this process, a mechanistic model is developed here. The model is based on three hypotheses: a flux of mechanical energy occurs through the wood, the magnitude of the flux can be derived from the contact mechanics of the grits, and the rise in wood temperature can be determined from the dissipation of the flux. A temperature distribution in the actual grinding process was simulated with the model. The simulated temperatures were compared with a measured temperature profile obtained from the literature. The modelled and measured temperatures matched quite well. The simulations show that an increase in grit size results higher temperatures, whereas an increase in the distance between grits gives lower temperatures. The main result of the study is that the Hertz theory of contact mechanics can be considered an adequate method for analysing the effect of grits in the grinding process. The result shows that the Hertz theory is applicable when fatigue models are developed; these models can then be used to reduce the energy consumption of the process.
机译：研磨是生产造纸用纸浆的常用方法，但其能源效率较差是一个缺点。本文着重于开发一种处理木材在磨削过程中温度升高的模型。该模型为理论方法的发展铺平了道路，这些理论方法可用于减少过程的能耗。在磨削过程中，木屑会被木屑加载，这会在木基体中引起应力波。应力波使木材疲劳，并最终使纤维与基质分离，但是由于木材的粘弹性，波的部分机械能转化为热量。为了了解此过程中木材温度的升高，在此建立了一个机械模型。该模型基于三个假设：机械能的通量通过木材发生，通量的大小可以从砂粒的接触力学中得出，而木材温度的升高可以通过通量的消散来确定。利用该模型模拟了实际磨削过程中的温度分布。将模拟温度与从文献中获得的实测温度曲线进行比较。建模和测量的温度非常匹配。模拟表明，增加砂粒尺寸会导致温度升高，而增加砂粒之间的距离会降低温度。该研究的主要结果是，可以将赫兹接触力学理论视为分析磨料在磨削过程中影响的合适方法。结果表明，赫兹理论适用于疲劳模型的建立。然后可以使用这些模型来减少过程的能耗。

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