本文選題：熱擠壓 + 凸模　； 參考：《中北大學(xué)》2017年碩士論文

【摘要】：熱擠壓技術(shù)作為金屬塑性加工技術(shù)的重要手段之一,越來越被廣泛應(yīng)用于航空航天、軍工、民用、電器等行業(yè)。在熱擠壓工藝得到廣泛應(yīng)用的同時,對模具的強度、疲勞壽命提出了較高的要求。當(dāng)熱擠壓模具在高溫、高壓、局部應(yīng)力集中的環(huán)境中長時間工作,極易使模具內(nèi)部應(yīng)力分布不均勻、斷裂失效。熱擠壓模具的失效嚴重阻礙工廠的批量化生產(chǎn),使得經(jīng)濟效益大大降低。因此,為使擠壓工藝在實際生產(chǎn)中廣泛使用,有必要對這種類型的杯形件擠壓模具進行優(yōu)化,提高其使用壽命。此類杯形件以前提高其模具壽命的方法有:選取優(yōu)質(zhì)高溫合金鋼作為模具材料、研究模具材料淬火和回火的熱處理最合理溫度區(qū)間以及模具使用工作過程的模具預(yù)熱溫度、潤滑等進行了大量的研究,這些方法可提升擠壓模具的壽命。但是當(dāng)前模具的使用周期仍不能滿足工廠實際需求,迫切需要尋求新思路來提高模具的使用壽命。隨著有限元數(shù)值模擬技術(shù)、優(yōu)化設(shè)計、傳熱學(xué)、熱疲勞、熱彈塑性等理論的不斷發(fā)展,為建立熱擠壓實際工況的有限元數(shù)值仿真模擬提供了有力的理論指導(dǎo)�；诟呔扔邢拊浖膽�(yīng)用,可通過數(shù)值模擬的方法得出:熱擠壓模具應(yīng)力的分布以及估算出模具的使用壽命,為設(shè)計者優(yōu)化模具提供新思路。本文以實際生產(chǎn)中杯形件熱擠壓凸模的斷裂失效問題為切入點,對模具材料為H13鋼的使用壽命進行了研究。通過有限元數(shù)值模擬,分析了凸模不同緊固方式和內(nèi)部水冷卻結(jié)構(gòu)對使用壽命的影響,最后對模具疲勞壽命進行了實際驗證。具體做了以下幾方面的工作:(1)采用ANSYS(APDL)分別對單螺紋緊固實心凸模、組合緊固式凸模進行了靜力學(xué)分析,得到等效應(yīng)力最大的危險點,從而為下一步的疲勞壽命分析,提供科學(xué)依據(jù)。(2)基于軟件ANSYS里的Fatigue模塊對不同結(jié)構(gòu)參數(shù)的凸模進行了疲勞計算。用電液伺服疲勞試驗機Instron8032測試H13鋼模具材料的S-N曲線數(shù)據(jù)。采用模擬和實驗相結(jié)合,進行疲勞分析,增加了模具疲勞壽命估算的精確度。通過比較疲勞結(jié)果發(fā)現(xiàn):采用組合式結(jié)構(gòu)緊固方式的凸模比單螺紋緊固的凸模疲勞壽命長。(3)在結(jié)構(gòu)優(yōu)化理論、傳熱學(xué)等理論的支持下,通過ANSYS對凸模內(nèi)部水循環(huán)冷卻結(jié)構(gòu)進行優(yōu)化。首先通過對不同內(nèi)徑D、底厚H凸模的熱應(yīng)力強度校核,得到空心凸模的參數(shù)取值范圍:實驗參數(shù)是底厚H為25mm,內(nèi)徑D為18mm、20 mm、22 mm、24 mm、26 mm、28 mm。(4)利用CFX軟件對上一步得到的不同結(jié)構(gòu)參數(shù)的空心凸模進行了流體分析。模擬計算完成后,得到不同內(nèi)徑(D)結(jié)構(gòu)凸模的溫度場云圖。分析發(fā)現(xiàn):在空心凸模同一切面上,D(內(nèi)徑)分別為24mm、26mm、28mm的凸模冷卻效果較好。(5)綜合上述緊固結(jié)構(gòu)的改進以及內(nèi)部內(nèi)徑、底厚尺寸的優(yōu)化參數(shù)范圍,分別制作凸模進行生產(chǎn)驗證其優(yōu)化前后的疲勞使用壽命情況。
[Abstract]:As one of the important means of metal plastic processing, hot extrusion technology has been widely used in aerospace, military, civil, electrical and other industries. While the hot extrusion process is widely used, the strength and fatigue life of die are required. When the hot extrusion die works for a long time in the environment of high temperature, high pressure and local stress concentration, it is easy to make the internal stress distribution uneven and fracture failure. The failure of hot extrusion die seriously hinders the mass production of the factory and greatly reduces the economic benefit. Therefore, in order to make the extrusion process widely used in practical production, it is necessary to optimize this type of cup extrusion die and increase its service life. The methods used to improve the life of this kind of cup are as follows: select high quality high temperature alloy steel as mould material, study the most reasonable temperature range of quenching and tempering of die material and the preheating temperature of die during the working process of die. A lot of researches have been done on lubrication. These methods can improve the life of extrusion die. However, the current life cycle of the die still can not meet the actual needs of the factory, so it is urgent to find new ways to improve the service life of the mould. With the development of finite element numerical simulation technology, optimization design, heat transfer, thermal fatigue, thermoelastic-plastic theory and so on, it provides a powerful theoretical guidance for the establishment of finite element numerical simulation under the actual conditions of hot extrusion. Based on the application of high precision finite element software, it can be obtained by numerical simulation that the stress distribution of hot extrusion die and the service life of die can be estimated, which provides a new idea for designers to optimize dies. In this paper, the service life of H13 steel is studied by taking the fracture failure of hot extrusion punch of cup in production as the breakthrough point. Through finite element numerical simulation, the influence of different fastening modes and internal water cooling structure on service life is analyzed. Finally, the fatigue life of die is verified. In this paper, the following work is done: 1) the single thread solid punch and the combined fastening punch are analyzed by ANSYS APDL, respectively, and the maximum equivalent stress danger point is obtained, which is the next step in the fatigue life analysis. Based on the Fatigue module in the software ANSYS, the fatigue calculation of the punch with different structural parameters is carried out. The S-N curve data of H 13 steel die materials were measured by Instron8032. Fatigue analysis is carried out by combining simulation and experiment, and the precision of die fatigue life estimation is increased. By comparing the fatigue results, it is found that the fatigue life of the punch with combined structure fastening is longer than that with single thread fastening, with the support of structural optimization theory and heat transfer theory. The water circulation cooling structure inside the punch was optimized by ANSYS. First of all, the thermal stress intensity of H punch with different inner diameters and bottom thickness is checked. The parameters of the hollow punch are obtained: the experimental parameters are: the bottom thickness H is 25mm, and the inner diameter D is 18mm 20 mm 20 mm 22 mm 24 mm 26 mm 28 mm. 4) the flow analysis of the hollow punch with different structure parameters obtained from the previous step is carried out by using CFX software. After the simulation, the temperature field of the punch with different inner diameters is obtained. It is found that the cooling effect of the die with D (internal diameter) of 24mm / 26mm / 28mm on the hollow punch and all surfaces is better. (5) the improvement of the above fastening structure and the optimum parameter range of the internal diameter and the bottom thickness size are synthesized. The punch was made to verify the fatigue life before and after optimization.
【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG375.41

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