【正文】 —物料作用在螺桿端面上的總壓力，D—螺桿的處直徑，cm —螺桿端部的物料壓力，—在螺桿擠出時由于動載荷產(chǎn)生的附加壓力的軸向分量，根據(jù)實(shí)驗(yàn)得出：當(dāng)機(jī)頭壓力時，；當(dāng)時。由于機(jī)筒外徑與內(nèi)徑之比大于1：1，所以可按壁厚理論進(jìn)行計(jì)算，按壁厚理論，機(jī)筒內(nèi)受物料的壓力P作用時，機(jī)筒臂上每一點(diǎn)都處于三向應(yīng)力狀態(tài)，如圖62所示，即徑向應(yīng)力，切向應(yīng)力和軸向應(yīng)力，則對一只受內(nèi)壓力作用的壁厚容器有： 圖61 機(jī)筒受力情況（a）機(jī)筒受力分布 （b）機(jī)筒應(yīng)力分布 式中 ，—機(jī)筒的內(nèi)外徑 ， r—機(jī)筒厚臂任意一點(diǎn)半徑由上式可知，當(dāng)時，徑向及切向應(yīng)力均達(dá)到最大值，即：當(dāng)時，徑向切向應(yīng)力達(dá)到最小值，即：由軸向力引起的軸向拉應(yīng)力在機(jī)筒全長上不變，即：按第四強(qiáng)度理論—最大變形能量理論計(jì)算，其強(qiáng)度條件為：所以有 機(jī)筒強(qiáng)度足夠。 電動機(jī)型號為，滿載轉(zhuǎn)速。 確定V帶的基準(zhǔn)長度及傳動中心距① 初定中心距即?、?帶的基準(zhǔn)長度為由文獻(xiàn)[3]：。/2) =（6）帶輪的結(jié)構(gòu)設(shè)計(jì) 根據(jù)D≤300時，可采用腹板式結(jié)構(gòu)；D300時，采用輻條式結(jié)構(gòu)。則有 查文獻(xiàn)[3]： 表33 普通V帶帶輪輪槽尺寸槽型槽根槽頂高槽間距e槽邊寬基準(zhǔn)寬度輪緣厚度輪 寬B槽 角φB14101 故取 (37)帶入數(shù)據(jù)得 (38)帶入數(shù)據(jù)得 齒輪工作為單班制，使用壽命10年，每年300個工作日，使用期限內(nèi)工作時間占20%。實(shí)際分度圓直徑中心距齒寬因模數(shù)取標(biāo)準(zhǔn)值時，齒數(shù)已重新確定并圓整則重合度系數(shù)齒間載荷分配系數(shù)齒向載荷分布系數(shù)載荷系數(shù)齒形系數(shù)應(yīng)力修正系數(shù)彎曲疲勞極限彎曲最小安全系數(shù)彎曲壽命系數(shù)尺寸系數(shù)許用彎曲應(yīng)力驗(yàn)算 　　　　　　外嚙合直齒圓柱齒輪傳動計(jì)算結(jié)果(表中) (mm) 名稱符號計(jì)算公式小齒輪大齒輪模數(shù)m4齒數(shù)z變位系數(shù)x嚙合角 分度圓直徑d節(jié)圓直徑中心距a實(shí)際中心距中心距變動系數(shù)y齒頂高降低系數(shù)齒頂高齒根高齒頂圓直徑齒根圓直徑齒輪寬度B6零件的選擇1鍵的選擇本設(shè)計(jì)選用的鍵有鍵A2260GB109680,鍵A25100 GB109680,本設(shè)計(jì)選用的軸承有軸承GB29764 7210，軸承GB29764 7214，軸承GB29764 7216。動聯(lián)接花鍵強(qiáng)度條件： （） （） 查表，則計(jì)算轉(zhuǎn)距為： （）  平鍵校核（以電機(jī)軸上的平鍵為例，鍵A1060）由文獻(xiàn)[1]平鍵聯(lián)接的強(qiáng)度校核公式可知： (64)式中 T —傳遞的轉(zhuǎn)矩，D —軸的直徑，m L —鍵的長度，mm L=60—許用應(yīng)力，=40則有 =所以 =40MPa，所用平鍵合格。之后在參考相關(guān)文獻(xiàn)和老師的指導(dǎo)下，完成了初步方案的初步設(shè)計(jì)。畢業(yè)設(shè)計(jì)在最大程度上綜合了大學(xué)所學(xué)的知識。花費(fèi)將近半個學(xué)期的時間，終于完成了此次設(shè)計(jì)所要完成的任務(wù)。經(jīng)歷了從查閱資料到設(shè)計(jì)計(jì)算再到結(jié)構(gòu)設(shè)計(jì)和軟件分析，對于我們學(xué)機(jī)械的是必須要掌握的，尤其是想從事科學(xué)研發(fā)方面的工作的更加重要。 Biomass resource。 China1. IntroductionDuring the course of global economic sustainable development, human beings are confronted with immense pressures in population, resources and the environment. The exploitation and utilization of energy is concerned with several factors: Developing countries are faced with the challenge of economic development, especially in the rural area. The energy problem in the rural area is mon in most developing countries. The core of the problem is how to coordinate development energy, society, economy and the environment. Biofuel has been a source of energy which human beings have used since ancient times. It has played an important role during the historical development of human society, and has accounted for more than 15% of China’s energy consumption in recent years. From the environmental point of view, it is part of the essence that poses the ecosystem and will not cause greenhouse warming [1,2].As a very important part of the national energy system, energy supply and consumption in the rural area has a great influence on the development of the rural society, economy and ecological environment. China is a large developing agricultural country, with its rural area largely populated. These areas used to be scarcely supplied with modities and the consumption of mercial energy per capita was low. Nonmercial energy was the main source of energy consumption, which was mainly local biofuel. The increase in population and the sterility of soil gave prominence to the contradiction between the demand and supply of energy, which led to the overconsumption of the local biomass resources and the direct threat to the environment [3–5].With the rapid development of the rural economy and the improvement of peasants’ living conditions, the energy consumption structure of the rural area is undergoing great changes. The demand for mercial energy is rapidly increasing, especially in some rural areas with good economy and modities which consume the main part of the available energy. This led to the superabundance of the original biomass energy source. The improper disposition of the superabundant biomass polluted the atmosphere, waters, and the ecological environment [6–8].Confronted with the pressures from both economical development in the rural area and environmental protection, China must realize that the sustained increase in the national economy changes the traditional production mode of energy and the way consumption exploits and utilizes biomass energy resources. This article discusses: (1) the present situation and development of the biomass resources and its consumption in the rural areas of China, (2) the outflow discharge of poisonous gases due to the consumption of biofuel, and (3) the changes of the total outflow discharge in the rural area after the substitution of fuels.532. The supply of biomass energy resources in the rural areaChina is abundant in biomass resources, which mainly includes straw and stalk and firewood. According to the statistics in 2000, the annual yield of crop straw was about billion metric ton, which could be converted into 338 Mtce. Recently, the straw and stalk resources have increased at a rate of % annually. Among all the straw and stalk, the losses during recycling in field and collection account for %, forage 28%, papermaking raw materials % and energy resources %.According to the survey on forest resources, forests co