本文關(guān)鍵詞： 純銅管材 TECAP工藝 模具結(jié)構(gòu) 微觀組織 成形模擬　出處：《山東建筑大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：純銅管材具有良好的耐蝕性,高溫下亦可正常工作,常用于較為復(fù)雜的環(huán)境。但是純銅擠壓管材質(zhì)地較硬,作為結(jié)構(gòu)件時(shí),受到周期載荷的情況下,純銅管材壽命較差,限制了管材的進(jìn)一步應(yīng)用。為了改善管材性能,提高其強(qiáng)韌性,研究新型工藝,而管的等通道轉(zhuǎn)角擠壓工藝(TECAP)作為一種新型的劇烈塑性變形方法。其工藝是在材料受到三向壓應(yīng)力的作用下,管坯發(fā)生純剪切變形,具有較好的變形效率�？梢詫�(shí)現(xiàn)管坯材料的納米化,具有較高的研究價(jià)值�，F(xiàn)階段,TECAP工藝正處于研發(fā)階段,本文通過對(duì)TECAP工藝?yán)硐霠顩r和三維情況進(jìn)行數(shù)值模擬,并對(duì)模擬結(jié)果進(jìn)行分析研究,為管材TECAP工藝更加深入系統(tǒng)研究打下良好的基礎(chǔ)。首先,在二維理想狀況下對(duì)管坯進(jìn)行等通道轉(zhuǎn)角擠壓數(shù)值模擬,發(fā)現(xiàn)管坯流動(dòng)規(guī)律和應(yīng)力應(yīng)變分布情況。在理想情況下,材料在經(jīng)過一道次的TECAP擠壓以后,部分管坯發(fā)生了較大的剪切變形,產(chǎn)生了良好的效果。在模擬過程中,經(jīng)過一道次TECAP變形后,靠近拐角處的管坯應(yīng)變最為明顯,最小變形處位于管坯的下端面遠(yuǎn)離拐角的位置。除此之外,材料與芯部填充物之間的接觸條件對(duì)試樣變形分布有著重要影響。接觸條件越穩(wěn)定變形質(zhì)量越好,因而在變形過程中摩擦因子選取0.6變形效果較好。在選擇填充材料時(shí),應(yīng)該選擇力學(xué)性能和管坯材料力學(xué)性能相近的金屬材料或非金屬材料。其次,在三維狀況下對(duì)純銅管材進(jìn)行了TECAP的數(shù)值模擬分析,得到不同模具結(jié)構(gòu)下,材料的流動(dòng)規(guī)律以及應(yīng)力應(yīng)變分布情況。發(fā)現(xiàn)圓心角Ψ=20°時(shí),拐角Φ=90°的情況下,管坯的等效應(yīng)力應(yīng)變較大,均勻性較好,管坯一道次變形綜合成形質(zhì)量較好。為了驗(yàn)證TCP模型和文中的TECAP模型變形情況,構(gòu)建了TCP模擬模型,對(duì)比了TECAP的Ψ=20°時(shí),Φ分別為90°、135°模具結(jié)構(gòu),在室溫,低速變形過程中,TCP等效應(yīng)變均值大于TECAP變形量。但是TCP對(duì)于模具質(zhì)量要求較高,變形質(zhì)量要由于TECAP變形質(zhì)量,但是管坯的外表面受損較為嚴(yán)重。除此之外,對(duì)管坯TECAP一道次變形不同變形速度、溫度以及潤滑條件下,材料的應(yīng)力應(yīng)變分布,發(fā)現(xiàn)和棒材具有一致性,在T=200℃時(shí),摩擦因子≤0.2時(shí),材料一道次TECAP變形效果較好。最后,對(duì)材料的微觀組織進(jìn)行了模擬,參考了位錯(cuò)變形機(jī)制和剪切變形機(jī)制,利用3D-deform軟件自帶的微觀組織模擬系統(tǒng),研究在再結(jié)晶溫度以下,材料晶粒、晶界以及位錯(cuò)的變化情況,分析驗(yàn)證Φ=90°,Ψ=20°時(shí),摩擦因子為0.12的情況下,管坯在T=250℃外界環(huán)境下,材料一道次TECAP變形后,管坯微觀組織演化效果較為明顯。通過對(duì)微觀組織模擬,發(fā)現(xiàn)晶粒演化存在位錯(cuò)的增加和消失,亞晶界向大角度晶界的演化,因而TECAP實(shí)現(xiàn)管坯的晶粒細(xì)化,同時(shí)位錯(cuò)的變化強(qiáng)化了管坯的力學(xué)特征。總而言之,管坯實(shí)現(xiàn)了一定程度的強(qiáng)化。
[Abstract]:Pure copper pipes have good corrosion resistance and can work normally at high temperature. They are often used in more complicated environments. However, pure copper extruded pipes have a hard texture. When they are used as structural parts, the life of pure copper pipes is poor when they are subjected to periodic loads. In order to improve the properties of pipes and improve their strength and toughness, a new technology is studied. As a new method of severe plastic deformation, the equal channel angular extrusion (TECAP) of the tube is a pure shear deformation of the tube billet under the action of triaxial compressive stress. It has good deformation efficiency, can realize the nanocrystalline material of tube blank, and has high research value. At present, the TECAP process is in the research and development stage, the ideal condition and three-dimensional condition of TECAP process are numerically simulated in this paper. The simulation results are analyzed and studied, which lays a good foundation for the further and systematic study of pipe TECAP process. Firstly, the equal channel angular extrusion numerical simulation of tube blank is carried out under the two dimensional ideal condition. It is found that the flow law and the stress and strain distribution of the tube billet. In ideal case, after a TECAP extrusion, some of the tube billets have a large shear deformation, which has a good effect. After a secondary TECAP deformation, the strain of the tube billet near the corner is the most obvious, and the minimum deformation is located at the lower end of the tube blank far from the corner. In addition, The contact condition between the material and the core filler has an important effect on the deformation distribution of the specimen. The more stable the contact condition, the better the deformation mass, so the friction factor 0.6 is better in the process of deformation. Metal or non-metallic materials with similar mechanical properties and similar mechanical properties should be selected. Secondly, the TECAP numerical simulation analysis of pure copper pipes is carried out under three dimensional conditions, and different die structures are obtained. It is found that when the center angle is 20 擄and the corner is 90 擄, the equivalent stress and strain of the tube billet is larger and the uniformity is better. In order to verify the deformation of the TCP model and the TECAP model in this paper, a TCP simulation model is constructed, and the die structure of 桅 is 90 擄~ 135 擄at room temperature. During low speed deformation, the mean equivalent strain of TECAP is greater than that of TECAP. However, TCP requires higher die quality, and the deformation quality is due to TECAP deformation quality, but the outer surface of tube billet is damaged seriously. It is found that the stress and strain distribution of the material is consistent with that of the bar under different deformation rates, temperatures and lubrication conditions of the TECAP secondary deformation of the tube billet. When the friction factor is less than 0.2, the deformation effect of the material is better than that of the steel bar. Finally, the stress strain distribution of the material is similar to that of the bar under different deformation rates, temperature and lubrication conditions. The microstructure of the material was simulated, and the change of grain, grain boundary and dislocation under recrystallization temperature was studied by using 3D-deform software's system of microstructure simulation, referring to the mechanism of dislocation deformation and shear deformation. The results show that under the condition of 桅 90 擄, 蠄 20 擄and friction factor 0.12, the microstructure evolution effect of tube billet is obvious after the material is deformed together with secondary TECAP under the external environment of T _ (250 鈩，

本文編號(hào)：1547458