摘 要
由于曲軸失效形式的復(fù)雜化和對(duì)曲軸修復(fù)后質(zhì)量要求的日益提高，傳統(tǒng)的修復(fù)技術(shù)已無法滿足曲軸的修復(fù)要求。近年來，作為激光再制造技術(shù)的核心——激光熔覆技術(shù)迅速發(fā)展成為曲軸再制造的一種新型修復(fù)技術(shù)。本文主要研究船用柴油機(jī)廢舊曲軸的再制造問題。
1. 從曲軸的磨損、燒蝕、彎扭變形以及裂紋和斷裂四個(gè)方面具體分析了船用柴油機(jī)曲軸的失效原因，得出以下三點(diǎn)：
(1) 校核靜強(qiáng)度安全系數(shù)，對(duì)曲軸的剛度、硬度和承受載荷能力進(jìn)行可靠性評(píng)估。校核疲勞強(qiáng)度安全系數(shù)，評(píng)估船用柴油機(jī)曲軸再制造前后的疲勞壽命。
(2) 根據(jù)疲勞裂紋擴(kuò)展規(guī)律和Paris公式，對(duì)曲軸的疲勞裂紋擴(kuò)展壽命進(jìn)行預(yù)測(cè)。
(3) 通過對(duì)曲軸材料性能的簡單分析，利用傳統(tǒng)的疲勞壽命預(yù)測(cè)方法、損傷力學(xué)和Miner疲勞損傷積累準(zhǔn)則確定曲軸剩余疲勞壽命的預(yù)測(cè)方法，即先預(yù)測(cè)曲軸在最大載荷下的疲勞壽命，再減去最大載荷下的當(dāng)量壽命，兩者的差就是曲軸的剩余疲勞壽命。
2. 利用1/4點(diǎn)位移法和J積分法對(duì)曲軸圓角處裂紋應(yīng)力強(qiáng)度因子的計(jì)算，判斷其斷裂失效的程度，并應(yīng)用15節(jié)點(diǎn)三維1/4奇異元和20節(jié)點(diǎn)三維單元分析曲軸圓角處裂紋的應(yīng)力場(chǎng)，求出應(yīng)力強(qiáng)度因子。
3. 針對(duì)曲軸的再制造問題，本文研究了激光熔覆技術(shù)的原理和主要特點(diǎn)，為熔覆材料與曲軸基體材料的匹配性提供了判斷依據(jù)；選擇了鎳基、鈷基和鐵基三種自熔性合金粉末作為熔覆材料；確定了修復(fù)工藝為同步式激光熔覆。對(duì)熔池狀態(tài)的研究為下文中的熱分析提供了理論依據(jù)，并為控制熔覆層的裂紋提供了解決的方法。
4. 根據(jù)溫度場(chǎng)的有限元理論和ANSYS的熱分析基礎(chǔ)，通過對(duì)再制造曲軸進(jìn)行有限元熱應(yīng)力分析，得到60秒后曲軸內(nèi)部的溫度場(chǎng)、位移、應(yīng)力場(chǎng)的分布情況和三種熔覆材料的熔滴在100微秒時(shí)的溫度場(chǎng)分布數(shù)據(jù)。根據(jù)熔覆層的應(yīng)力狀態(tài)理論分析三種熔覆層的殘余應(yīng)力場(chǎng)，通過比較得出鐵基自熔性合金粉末Fe55與曲軸基材結(jié)合性較好，熔覆效果好。

關(guān)鍵詞 激光再制造；激光熔覆；曲軸；有限元；殘余應(yīng)力



Abstract
The traditional repair techniques have been unable to meet the requirements of the crankshaft repair，as the crankshaft failure in the form of complex and the increasing quality requirements after the crankshaft has been repaired. In recent years, as the core of the laser remanufacturing technology — laser cladding technology has rapidly developed into a new crankshaft remanufacturing repair technology .The main content of this paper is about that the remanufacturing problem of the marine diesel engine waste crankshaft.
1. From the crankshaft wear, erosion, cracks and bending and torsion deformation and fracture in four areas, detailed analysis of the reasons for the failure of marine diesel engine crankshaft, draw the following three points:
(1) Checking static strength safety factor, assesses the reliability of the crankshaft stiffness, hardness and load bearing capacity. Checking the fatigue strength safety factor, assesses the fatigue life before and after remanufacturing of marine diesel engine crankshaft.
(2) According to the law of fatigue crack growth and Paris formula, predicts fatigue crack growth life of the crankshaft.
(3) Through a simple analysis of the crankshaft material properties, using traditional fatigue life prediction method, damage mechanics and miner fatigue damage accumulation criterion to determine the prediction method of the remaining fatigue life of the crankshaft, that is, first predicts the fatigue life of the crankshaft under maximum load, then minus the equivalent life under maximum load, the difference between the two is the remaining fatigue life of the crankshaft.
2. Using 1 / 4 point displacement method and the J-integral method to calculate the stress intensity factor of the crack at crankshaft fillet, judges it’s degree of fracture failure, while applies the 15-node three-dimensional 1 / 4 singular element and 20-node three-dimensional unit, analyses the stress field of the crack at crankshaft fillet and finds the stress intensity factor.
3. Against the problem of the crankshaft remanufacturing, the paper studies the principle and main characteristics of laser cladding, provides a theoretical basis for the matching of cladding material and the matrix material of crankshaft; chooses nickel , cobalt and iron base three kinds of self-fluxing alloy powder as cladding materials; determines the Repair process to be the synchronized laser cladding. The research on the pool State provides a theoretical basis for the thermal analysis below, and provides a solution for the control of cracks in the cladding layer.
4. According to the finite element theory of temperature field and the basis of thermal analysis of ANSYS, get the distribution of the temperature field, displacement, and the stress field inside the crankshaft after 60 seconds through the finite element thermal stress analysis of the remanufactured crankshaft and the temperature distribution data of three kinds of cladding material’s droplet at 100 microseconds. According to the stress state theory of the cladding layer, analyzed the residual stress fields of the three cladding layer, obtains that the combination of Fe-based self-fluxing alloy powder Fe55 and the crankshaft substrate is better and it’s cladding effect is well by comparison.

Keywords laser remanufa..