摘要
眾所周知，焊接技術在現(xiàn)代船舶工業(yè)中的地位變得越來越重要，焊接技術水平對提高船舶焊接生產(chǎn)效率、縮短船舶建造周期、降低成本、提高企業(yè)競爭力具有舉足輕重的作用。而在焊接過程中焊接變形不但備受重視而且又是難以控制的環(huán)節(jié)。焊接變形造成焊件形狀尺寸改變，當受到工作載荷作用時，焊接變形產(chǎn)生的附加彎矩和應力集中現(xiàn)象是造成船舶結構早期失效的主要原因。因此，預測及控制焊接變形已經(jīng)是實際生產(chǎn)中必須要解決的問題。
預測大型復雜焊接結構的焊接變形必須解決兩個問題。其一是要保證足夠的預測精度，其二是要節(jié)約運算時間和成本。焊接熱彈塑性有限元法在焊接數(shù)值模擬中得到廣泛應用。但它需要的計算時間長、計算規(guī)模大，目前只適用于焊接接頭及較小結構的焊接行為力學分析，因而用于預測大型復雜結構焊接變形時還有限。
本文采用日本學者提出的殘余應力之源的固有應變的理論，開展大型復雜船體結構的焊接變形預測研究工作。固有應變法是一種相對快速的、有效的、近似的方法，并能夠得到一定準確度的焊接變形值，為確定反變形量提供一種有力的、新的計算工具。這種方法具有非常大的工程實用意義和發(fā)展前景。需要注意的是，固有應變法是建立在船體結構焊接的固有應變數(shù)據(jù)庫基礎之上，固有應變數(shù)據(jù)庫是確保預測焊接變形結果準確的前提。
本文算例采用基于固有應變預測法和彈性板單元有限元法，利用焊接結構變形專用預測軟件Weld_sta對研究對象進行焊接變形模擬計算，預測其焊接變形。固有應變預測法是在大量的計算和實測數(shù)據(jù)基礎上，整理得到簡化的以板厚為參數(shù)的固有應變計算公式，并建立船體結構焊接的固有應變數(shù)據(jù)庫，為預測大型復雜船體結構的焊接變形提供可能。
研究結果表明，基于固有應變法的專用焊接軟件Weld_sta可以成功預測大型復雜船體結構的焊接變形，為確定反變形量和精度造船的實現(xiàn)提供一種新計算工具，為預測大型復雜結構的焊接變形提供一種新的思路和方法。
通過以上的工作基本實現(xiàn)了大型復雜船體結構焊接變形的預測模擬，由于焊接過程的復雜性，考慮影響焊接變形的因素不夠全面，還存在一定的差距，仍然需要進行深入的研究。

關鍵詞：固有應變理論；Weld_sta軟件；曲板結構；大型復雜船體結構；焊接變形




























Abstract
It is well known that welding technology is playing a more and more important role in ship industry, which can improve productive efficiency in welding of ship, shorten the production cycle, reduce cost and enhance the competitiveness of enterprise. Welding distortion, however, not only has been taken into consideration. But also it is tough to control the welding distortion in the whole welding procedure. Welding distortion existed may lead to shape and size of the ship structure to vary, what’s more, the additional bending moment and phenomenon of stress concentration which were generated by welding distortion under working load is the main reason leading to the premature failure of hull structure. For the reason above mentioned, the prediction and control of welding distortion has been a significant and emergent problem to be resolved in actual production.
There are two problems in predicting welding distortion of large and complicated ship structure. One is how to ensure enough distortion tolerance; another is how to save calculation time and cost. Thermal elastic-plastic finite element method is widely used in numerical simulation of welding, which needs computer memory of large capacity and takes more time to calculate and now is not applicable to research of other large-scale and complicated structures apart from welded joint and small structures.
The paper adopted the inherent strain theory that Japanese scholars brought forward and studied the prediction of the distortion of the large and complicated ship structure on the basic of inherent strain theory. Inherent strain method is a kind of relatively fast and effective and approximate method, what’s more, it can make sure to get values of welding distortion accurately, which offers a strong and new tool in calculating values of anti-deformation. Hence, this method must be really very important in practical significance and be with pretty good future.
This paper takes the seven examples as object, those examples adopted inherent strain method and finite element method of plastic shell element. Then, numerical simulating the welding distortion of ship structures by special software Weld_sta. In the method on the basic of inherent strain theory, getting a simplified formula is about a thickness parameter of plates through a pretty large number of calculating and measuring datas and establishing an inherent strain database of ship structures welding. It is pretty possible to predict the welding distortion of large hull structure on the basic of above mentioned.
The study shows that the exclusive welding software Weld_sta on the basic of inherent strain successfully predict welding distortion of hull structure, which provides a powerful and new tool for confirming value of anti-deformation and accuracy shipbuilding to achieve, providing a kind of new idea and method for predicting the welding distortion of large-scale and complicated structure.
Though the inherent strain finite element method can predict successfully the ..