【摘要】：在木材干燥和使用過程中,由于水分散失尺寸減小形成的干縮力使木材產(chǎn)生表裂和內(nèi)裂,為了研究和測(cè)試木材干縮力,首先研制木材干縮力測(cè)試儀,研究了不同干燥條件下干縮力的變化規(guī)律;干縮力的研究需要能夠同時(shí)監(jiān)測(cè)水分的散失和尺寸的減小,利用溫濕度試驗(yàn)箱、力學(xué)傳感器、重量傳感器、位移傳感器同步測(cè)試木材在干燥過程中的干縮力、含水率、干縮量,優(yōu)化了木材干縮力測(cè)試系統(tǒng)�；跍貪穸仍囼�(yàn)箱的控溫控濕干縮力綜合測(cè)試系統(tǒng),更好地研究和探索了木材在干燥過程中的干縮力、干縮量和含水率之間的關(guān)系,研究了干燥溫度、相對(duì)濕度對(duì)木材干縮的影響,主要內(nèi)容如下:1.研究測(cè)試了不同規(guī)格樟子松(P.sylvestris)板材在不同干燥條件下干縮力的變化規(guī)律。結(jié)果表明:(1)同一厚度條件下,溫度高的試件達(dá)到應(yīng)力平衡所需時(shí)間比溫度低的試件達(dá)到平衡所需時(shí)間短,干縮力變化也較溫度低的明顯,但達(dá)到應(yīng)力平衡時(shí)溫度高的試件所受的干縮力相對(duì)小于溫度低的試件。(2)同一溫度條件下,薄試件所受干縮力要明顯大于厚試件所受干縮力,且干縮力達(dá)到最大值所需的時(shí)間明顯少于厚試件。試件的個(gè)體差異性產(chǎn)生的誤差對(duì)試驗(yàn)也有一定的影響。2.為了同步測(cè)試木材在干燥過程中的干縮力、質(zhì)量變化和干縮量,研制了木材干縮力測(cè)試系統(tǒng)。系統(tǒng)利用了木材干燥過程中水分散失導(dǎo)致外部干縮力變化的關(guān)系,設(shè)計(jì)了基于溫濕度試驗(yàn)箱的一體化控溫控濕力學(xué)測(cè)試系統(tǒng),更好地研究和測(cè)試了木材在干燥和使用過程中的干縮力、含水率和干縮量之間的關(guān)系。測(cè)試結(jié)果表明:用此設(shè)備可實(shí)時(shí)檢測(cè)干縮力、質(zhì)量變化和干縮量的平衡情況,為木材干縮不均導(dǎo)致干燥過程中的開裂、翹曲變形的調(diào)控奠定了基礎(chǔ)。3.通過系統(tǒng)地研究家榆(UlmuspumilaL.)干燥溫度、相對(duì)濕度對(duì)干縮力的影響,得到以下結(jié)論:(1)當(dāng)干縮量和含水率達(dá)到穩(wěn)定時(shí),干縮力的變化也基本很小,在較高溫度時(shí),內(nèi)裂的形成會(huì)導(dǎo)致干縮力的急劇減小。(2)在干燥初期,干縮力是負(fù)值,是因?yàn)槟静牡臒崤蛎洭F(xiàn)象引起的;隨著含水率的減小和干縮量的增加,干縮力逐漸增加并達(dá)到一個(gè)穩(wěn)定值。(3)影響干縮力的顯著因素是溫度,影響干縮量的顯著因素是收縮的方向和試件厚度,影響含水率的顯著因素是溫度和濕度。
[Abstract]:In the process of wood drying and using, the dry shrinkage force caused by the decrease of the size of water loss causes the surface crack and internal crack of the wood. In order to study and test the dry shrinkage force of the wood, a wood dry shrinkage tester is first developed. The change law of dry shrinkage force under different drying conditions is studied, the study of dry shrinkage force needs to be able to monitor the loss of moisture and the reduction of size simultaneously, using the temperature and humidity test box, mechanical sensor, weight sensor, The dry shrinkage force, moisture content and shrinkage amount of wood were measured by displacement sensor in the process of drying, and the system of measuring dry shrinkage force of wood was optimized. Based on the test box of temperature and humidity, the comprehensive measuring system of controlling temperature and humidity controlling dry shrinkage force is used to study and explore the relationship among the drying shrinkage force, shrinkage amount and moisture content of wood in the drying process, and the drying temperature is studied. The effect of relative humidity on wood shrinkage is as follows: 1. The change of drying shrinkage force of different specifications of Pinus sylvestris var. mongolica (P.sylvestris) plates under different drying conditions was studied. The results show that: (1) under the condition of the same thickness, the time required to achieve stress balance of the specimen with high temperature is shorter than that of the specimen with low temperature, and the change of dry shrinkage force is obviously lower than that of the specimen with low temperature. However, when the stress balance is reached, the dry shrinkage force of the specimen with high temperature is relatively smaller than that of the specimen with low temperature. (2) under the same temperature, the dry shrinkage force of thin specimen is obviously larger than that of thick specimen. And the time required to reach the maximum dry shrinkage force is obviously less than that of the thick specimen. The error caused by the individual difference of the specimen also has certain influence on the experiment. 2. In order to measure the dry shrinkage force, mass change and shrinkage quantity of wood in the drying process simultaneously, a system for measuring the dry shrinkage force of wood was developed. Based on the relationship between moisture loss and external shrinkage force during wood drying, an integrated temperature control and humidity control mechanical testing system was designed based on temperature and humidity test box. The relationship among shrinkage, moisture content and shrinkage of wood during drying and using was studied and tested. The test results show that the balance of dry shrinkage force, mass change and dry shrinkage can be detected in real time by using this equipment, which lays a foundation for controlling the cracking and warping of wood during drying process due to uneven shrinkage. Through systematic research on (UlmuspumilaL.) of Ulmus pumila The effects of drying temperature and relative humidity on the dry shrinkage force are as follows: (1) when the drying shrinkage and moisture content reach a stable level, the change of the dry shrinkage force is also very small, and at a higher temperature, The formation of internal cracks will lead to a sharp decrease in dry shrinkage. (2) at the beginning of drying, the dry shrinkage is negative because of the thermal expansion of wood, and with the decrease of moisture content and the increase of dry shrinkage, The dry shrinkage force increases gradually and reaches a stable value. (3) temperature is the significant factor affecting the dry shrinkage, the direction of shrinkage and the thickness of the specimen is the significant factor affecting the dry shrinkage, and the significant factors affecting the moisture content are temperature and humidity.
【學(xué)位授予單位】：內(nèi)蒙古農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：S782.31

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