本文選題：螺栓連接 + 軸向激勵(lì)��； 參考：《西南交通大學(xué)》2016年博士論文

【摘要】：由于結(jié)構(gòu)簡單、拆卸方便和成本低等優(yōu)點(diǎn),螺栓連接結(jié)構(gòu)廣泛應(yīng)用于各類工程結(jié)構(gòu)中。作為重要的連接部件,其性能對(duì)整個(gè)結(jié)構(gòu)的安全性和可靠性具有重要影響。在振動(dòng)環(huán)境下,松動(dòng)是螺栓連接結(jié)構(gòu)失效的主要形式之一。鑒于螺栓松動(dòng)機(jī)制的重要性和復(fù)雜性,國內(nèi)外對(duì)其進(jìn)行了廣泛的研究。但是由于加工精度和表面粗糙度不同等原因,螺栓松動(dòng)試驗(yàn)結(jié)果重復(fù)性差、分散性大,難以發(fā)現(xiàn)松動(dòng)的規(guī)律,對(duì)于螺栓的松動(dòng)機(jī)制至今尚未形成統(tǒng)一的認(rèn)識(shí)。開展螺栓松動(dòng)試驗(yàn)的研究,具有重要的科學(xué)意義,不僅可以深化對(duì)螺栓松動(dòng)機(jī)理的認(rèn)識(shí),而且為工業(yè)實(shí)際螺栓防松提供重要的理論指導(dǎo)。本論文基于自主研制的螺栓松動(dòng)試驗(yàn)裝置,成功再現(xiàn)了軸向激勵(lì)下螺栓連接結(jié)構(gòu)的松動(dòng)過程,并在在不同預(yù)緊力矩/預(yù)緊力和交變載荷幅值等試驗(yàn)參數(shù)下,系統(tǒng)開展了軸向激勵(lì)下螺栓/鋁制件連接結(jié)構(gòu)和螺栓/鋼制螺母連接結(jié)構(gòu)的松動(dòng)試驗(yàn)；對(duì)螺栓進(jìn)行表面處理,研究聚四氟乙烯涂層(PTFE涂層)、二硫化鉬涂層(MoS2涂層)和氮化鈦涂層(TiN涂層)對(duì)螺栓連接結(jié)構(gòu)防松性能的影響；基于MoS2涂層螺栓,通過理論計(jì)算獲取合理的預(yù)緊力,并研究其防松性能。在動(dòng)力學(xué)分析的基礎(chǔ)上,運(yùn)用光學(xué)顯微鏡(OM)、掃描電子顯微鏡(SEM)和電子能譜儀(EDX)進(jìn)行微觀分析,并結(jié)合有限元計(jì)算,系統(tǒng)揭示了螺栓連接結(jié)構(gòu)的松動(dòng)機(jī)理。完成的主要研究內(nèi)容和獲得的主要結(jié)論如下：(一)軸向激勵(lì)下螺栓連接結(jié)構(gòu)松動(dòng)機(jī)理基于動(dòng)力學(xué)響應(yīng)以及螺紋表面損傷形貌分析,結(jié)合有限元計(jì)算,發(fā)現(xiàn)螺栓連接結(jié)構(gòu)的松動(dòng)機(jī)理是結(jié)構(gòu)的塑性變形和接觸界面的微動(dòng)磨損。(1)螺栓連接結(jié)構(gòu)的松動(dòng)過程可分為兩個(gè)階段：第一階段,由于螺栓連接結(jié)構(gòu)的塑性變形以及接觸表面粗糙峰被去除,螺栓軸向力迅速下降；第二階段,隨著循環(huán)次數(shù)的增加,由于材料的棘輪效應(yīng),塑性變形趨于穩(wěn)定,微動(dòng)磨損是螺栓軸向力下降的主要原因。(2)研究表明預(yù)緊力矩/預(yù)緊力、交變載荷幅值、循環(huán)次數(shù)等試驗(yàn)參數(shù)對(duì)螺栓連接結(jié)構(gòu)的松動(dòng)行為具有強(qiáng)烈的影響：隨著預(yù)緊力矩/預(yù)緊力的增大,螺栓殘余軸向力與預(yù)緊力之比增大,螺紋表面的磨損程度逐漸降低,主要的磨損機(jī)制由疲勞磨損、粘著磨損向磨粒磨損轉(zhuǎn)變；隨著交變載荷幅值的增大,螺栓殘余軸向力與預(yù)緊力之比減小,螺紋表面的磨損程度加劇,主要的磨損機(jī)制由磨粒磨損向疲勞磨損轉(zhuǎn)變；由于磨屑的塞積、排出,螺栓軸向力在試驗(yàn)過程中出現(xiàn)先增大后減小的現(xiàn)象,但總體呈減小趨勢(shì)；在MoS2潤滑劑潤滑條件下,螺栓/鋁制件連接結(jié)構(gòu)的殘余軸向力與預(yù)緊力之比相對(duì)于無潤滑條件下較大,螺紋表面的損傷程度相對(duì)較輕,主要的磨損機(jī)制為磨粒磨損。(二)軸向激勵(lì)下不同涂層螺栓連接結(jié)構(gòu)的松動(dòng)機(jī)理(1)在螺栓松動(dòng)過程的第一階段,由于界面摩擦系數(shù)低,PTFE涂層和MoS2涂層螺栓表面粗糙峰少,螺栓軸向力在此階段變化��；反之,TiN涂層螺栓軸向力在此階段下降相對(duì)明顯。(2)在螺栓松動(dòng)過程的第二階段,由于PTFE涂層的結(jié)合強(qiáng)度低,螺紋表面的PTFE涂層磨損嚴(yán)重,螺栓軸向力在此階段變化大；MoS2涂層摩擦系數(shù)小,螺紋表面摩擦應(yīng)力小,且該涂層結(jié)合強(qiáng)度高,接觸界面的磨損輕微,螺栓軸向力在此階段變化��；由于TiN涂層的耐磨性能好,接觸界面的磨損輕微,螺栓軸向力在此階段變化也小。(3)在螺栓表面涂覆MoS2涂層后,在與未經(jīng)過表面處理的螺栓螺紋根部相同的應(yīng)力狀態(tài)下,預(yù)緊力可以提高近20%。此時(shí)螺紋接觸界面的摩擦應(yīng)力和單位面積的摩擦耗散能減小,說明螺紋表面的損傷輕微；接觸面積增大,螺紋根部由交變載荷引起的累積塑性應(yīng)變減小。螺栓的防松性能得到大幅度的提高。(三)螺栓連接結(jié)構(gòu)的精確建模及數(shù)值分析運(yùn)用Matlab軟件和ABAQUS軟件建立了螺栓連接結(jié)構(gòu)的精確模型,并通過理論計(jì)算驗(yàn)證了有限元模型的有效性,研究結(jié)果表明：(1)第一圈工作螺紋約承受全部軸向力的30%,前三圈工作螺紋約承受全部軸向力的70%。螺栓第一圈工作螺紋牙底的應(yīng)力集中系數(shù)最大,隨著圈次的增加,應(yīng)力集中系數(shù)首先迅速降低,然后緩慢下降。此外,螺母螺紋牙底的應(yīng)力集中系數(shù)相對(duì)較低。(2)沿螺栓徑向方向,靠近螺紋牙頂區(qū)域單位面積的摩擦耗散能最大,說明此區(qū)域損傷較為嚴(yán)重；靠近螺紋牙底區(qū)域由于沒有發(fā)生相對(duì)滑動(dòng),因此該區(qū)域損傷輕微。沿螺栓周向方向,單位面積的摩擦耗散能總體呈現(xiàn)減小趨勢(shì),說明隨著工作螺紋圈次的增加,磨損總體呈減輕趨勢(shì)；但是單位面積的摩擦耗散能不是單調(diào)減小的,導(dǎo)致螺紋表面的磨損不均勻。(3)隨著預(yù)緊力的增大,螺紋接觸界面的摩擦應(yīng)力略微增大,但相對(duì)滑移量明顯減小,表面單位面積的摩擦耗散能減小,說明螺紋表面的損傷減輕；同時(shí),螺紋接觸面積增大,螺紋根部由交變載荷引起的累積塑性應(yīng)變減小。因此,殘余軸向力與預(yù)緊力之比增大。隨著交變載荷幅值的增大,螺紋接觸界面的摩擦應(yīng)力和相對(duì)滑移量均增大,表面單位面積的摩擦耗散能增大,說明螺紋表面的磨損加劇；同時(shí),螺紋根部由交變載荷引起的累積塑性應(yīng)變?cè)龃�。因�?殘余軸向力與預(yù)緊力之比減小。(4)降低螺栓頭部／被連接件和螺紋接觸界面的摩擦系數(shù),并適當(dāng)提高預(yù)緊力,可降低由交變載荷引起的塑性變形和螺紋表面單位面積的摩擦耗散能,從而有效提高螺栓的防松性能。
[Abstract]:Due to the advantages of simple structure , convenient disassembly and low cost , the bolt connection structure is widely used in various engineering structures . As an important connecting part , the performance of the bolt has an important influence on the safety and reliability of the whole structure .
The effect of PTFE coating ( PTFE coating ) , molybdenum disulfide coating and TiN coating on the anti - loosing performance of bolted connection structure was studied by surface treatment of bolts .
Based on the analysis of dynamic analysis , the loose mechanism of bolt connection structure is analyzed by means of OM , SEM and EDX .
In the second stage , with the increase of the number of cycles , the plastic deformation tends to be stable due to the ratchet effect of the material , and the fretting wear is the main reason for the decrease of the axial force of the bolt .
With the increase of the amplitude of the alternating load , the ratio of the residual axial force of the bolt to the pre - tightening force is reduced , the wear degree of the thread surface is increased , and the main wear mechanism is changed from the wear of the abrasive particles to the fatigue wear ;
The axial force of the bolt is decreased after the increase of the axial force of the bolt in the course of the test , but there is a decrease trend .
Under the condition of lubricant lubrication , the ratio of residual axial force to pre - tightening force of bolt / aluminum part connecting structure is relatively light , the damage degree of thread surface is relatively light , the main wear mechanism is abrasive particle wear .
On the contrary , the axial force of the TiN coating bolt is relatively obvious at this stage . ( 2 ) In the second stage of the bolt loosening process , the PTFE coating on the thread surface is worn seriously due to the low bonding strength of the PTFE coating , and the axial force of the bolt is large in this stage ;
The friction coefficient is small , the friction stress of the thread surface is small , and the bonding strength of the coating is high , the wear of the contact interface is slight , and the axial force of the bolt is small in this stage ;
The wear resistance of TiN coating is good , the wear of the contact interface is slight , and the axial force of the bolt is small in this stage . ( 3 ) After the coating of the coating on the surface of the bolt , the pre - tightening force can be increased by nearly 20 % in the same stress state as the root of the bolt thread without surface treatment .
The results show that ( 1 ) the stress concentration coefficient of the first ring working thread is about 30 % of the total axial force , and the stress concentration coefficient of the first ring working thread is about 70 % . The results show that : ( 1 ) The stress concentration coefficient of the first ring working thread is relatively low .
Due to the absence of relative sliding in the area near the thread bottom , the area is slightly damaged . In the circumferential direction of the bolt , the friction dissipation in the unit area can generally reduce the trend , which indicates that with the increase of the number of working thread turns , the wear is generally decreasing .
However , the friction dissipation in the unit area is not monotonically decreasing , which leads to uneven wear of the thread surface . ( 3 ) As the pre - tightening force increases , the friction stress of the thread contact interface increases slightly , but the relative slip amount is obviously reduced , and the friction dissipation of the surface unit area can be reduced , so that the damage on the surface of the screw thread is reduced ;
Therefore , the ratio of the residual axial force to the pre - tightening force is increased . As the amplitude of the alternating load increases , the friction stress and relative slip amount of the thread contact interface are increased , and the friction dissipation of the surface unit area can be increased , so that the wear of the thread surface is increased ;
As a result , the ratio of residual axial force to pre - tightening force is reduced . ( 4 ) The friction coefficient of bolt head / screwed contact interface is reduced , and the pre - tightening force is increased properly . The frictional dissipation energy caused by alternating load and unit area of thread surface can be reduced , so that the anti - loosing performance of the bolt can be effectively improved .
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TH131.3

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本文編號(hào)：2057306