加工后的双壁金属换热管在升温-降温过程中受到的力学影响

铅冷钠冷快堆核电设备中的蒸汽发生器，有着在液态金属和水之间进行热交换的作用，其换热部分由排列的换热管组成。贴合式的双壁管是一种具有高换热效率及抵抗管裂纹扩展的管材，适合于这种应用环境。这种管材的内外管间存在残余压力，这是内外管紧贴的标志。然而在经历升至高温又降温的过程后，内外管间残余压力有可能消失引起两管脱开。为了得知温度对贴合式双壁金属管的具体影响，本文设计了一种拉伸法来制备双壁管，并同时采用有限元数值模拟管的加工制备过程并得到了内外管间的残余应力，再对加温后降温的过程进行模拟，分析换热管残余应力和应变状态进行了分析的变化，并通过初步试验来进行验证。通过研究，结果表明温度变化引起的塑性变形是管间残余压力变化的主要原因。通过控制管的加工过程来控制管材加工程度的方法，可望应对温度变化对管稳定性的影响。

Influence of Heating-Cooling Process on Residual Stress of Double Wall Metal Heat Exchanger Tube

The steam generator in the nuclear power plant of lead or sodium-cooled fast reactor is used for heat exchange between liquid metal and water. The heat exchange part of the steam generator is composed of heat exchange tubes arranged in a row. Bonded double-wall pipe is a kind of pipe with high heat transfer efficiency and resistance to crack propagation. Residual pressure exists between the inner and outer tubes of this kind of tubee, which is a sign that the inner and outer tubes are pressed together. However, after rising to high temperature and then getting cooled, the residual pressure between the inner and outer tubes may disappear and cause detachment. Temperature in order to know the specific influence of joint type double-wall tube, this paper designs a stretch of the double-wall pipe, and at the same time, the finite element numerical simulation method, the simulation of the pipe processing preparation and residual stress between the inner and outer pipe is obtained, and then simulated the process of cooling down after heating, analyzed the change of residual stress and strain state of the heat exchanger tube, and verified by preliminary tests. Through the study, the results show that the plastic deformation caused by the temperature change is the main reason for the change of residual stress between the tubes. The method of controlling the degree of tube processing by controlling the tube processing is expected to cope with the effect of temperature variation on tube stability.