共查询到18条相似文献,搜索用时 156 毫秒
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从不考虑材料冷作硬化(理想弹塑性体)与考虑冷作硬化(双线性随动硬化)两个方面对带坯在成卷、开卷、展平、塑性弯曲及回弹过程中产生的应力进行了解析分析,获得了冷弯残余应力沿厚度方向上的分布,随后对比研究了考虑硬化与不考虑硬化对冷弯残余应力分布的影响,并将理论计算结果与实测残余应力进行了对比。结果表明,理想弹塑性模型和硬化模型预测的残余应力分布形式几乎一致;成卷上存在屈服时,纵向残余应力由内外表面向板厚中心方向呈非线性分布(成卷上无屈服时呈线性分布),横向残余应力呈近似线性分布;在变形外区主要为残余拉应力(横向残余应力在外侧有极小部分受压区),内区主要为残余压应力(横向残余应力在内侧有极小部分受拉区);横、纵向残余应力最大值均在中性层位置;研究结果与试验测量结果基本一致。 相似文献
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用X射线法监测5000kW电机轴的残余应力的矫直过程中的流动应力。 残余应力部份:在对事故后的电机轴受力及变形情况初步分析的基础上,选择测试点,对数据进行整理分析,得出下列结论:电机轴轴颈弯曲,严重的偏向一侧。造成一侧的抗应力达257MPa,另一侧压应力为131MPa,呈现高水平的残余应力状态。矫直应力监测部份:采用持续加载,持续监测的方法。在原来测量残余应力的对应点,作了矫直前的初始态调查。并选择矫直监测的关键点,结果表明:当加载到70吨时,轴发生明显变形,以后持续加载产生应变强化,测试数据曲线反映出明显规律,加载到140吨时将达到理想的矫直效果。 本文结合测试数据,着重分析讨论了:(1)矫直过程中应力的监测与预测推断。(2)矫直过程中轴的受力状态和变形。(3)矫直过程中的间断性重复加载和由此产生的过应变和滞后现象。(4)应变强化和残余应力。 相似文献
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基于工程弹塑性力学建立了不同组坯方式下双金属复合板弯曲矫直过程截面弹塑性状态演变路径的解析模型.基于该模型分析不锈钢复合板矫直过程中的弯曲回弹特性,解释复合板弯曲回弹过程中截面的反向屈服现象,并将不锈钢复合板与单一材料板材弯曲过程进行对比.研究结果表明:双金属复合板在弯曲过程中截面会经历五种弹塑性状态,并伴随着不同的中性层偏移规律,弯曲回弹后的残余应力分布与单一材料板相比更加不均匀且可能进入反向屈服状态;复合板与单一材料板材的弯矩相对差值随着屈服强度比的增大而增大,其绝对值随着弯曲曲率先增大后减小. 相似文献
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皮尔格冷轧无缝钢管过程中为了获得性能较好的成品需要选择合理的送进量数值,本文以冷轧304不锈钢为研究对象,借助有限元模拟软件对不同送进量下的皮尔格冷轧过程进行了完整的仿真,对比分析了送进量对金属流动速度、轧制力、等效应力、残余应力及管材回弹的影响规律.结果表明轧制过程中孔型背脊和与轧辊接触的孔型侧壁处管材金属流动速度随送进量增加而增加,轧制力、等效应力及残余应力均随送进量的增加而增大,并且送进量的增大还会显著增加管材的回弹量.借助试验轧机对不同送进量下皮尔格冷轧管进行轧制试验,对试验得到的管材进行尺寸和残余应力测量,测量结果与有限元仿真结果基本一致,为皮尔格轧制过程不同送进量的选择提供依据. 相似文献
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P110级石油套管淬火组织形态对残余应力的影响 总被引:1,自引:0,他引:1
以降低P110级石油套管淬火冷却过程中的热应力和组织应力为目的,提出了水淬+空冷和水淬+空冷+水淬两种冷却方式。利用逐层钻孔法测试了不同工艺下的残余应力,分析了淬火组织特征和残余应力对裂纹产生和扩展的影响。结果表明:直接淬火工艺的淬火组织为板条马氏体和孪晶马氏体共存,且孪晶马氏体的含量较多。水淬+空冷和水淬+空冷+水淬两种工艺的淬火组织为板条马氏体、下贝氏体和不同程度的残余奥氏体,水淬+空冷+水淬工艺中还有少量孪晶马氏体。水淬+空冷、水淬+空冷+水淬两种冷却方式和直接淬火工艺相比,钢管内的切向和轴向残余应力均减小,从而易减小钢管的变形,以及降低和缓解了钢管内微裂纹的产生和扩展趋势。 相似文献
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为了进一步提高中厚板产品矫直质量,采用弹塑性差分的曲率积分方法,分析了弯辊对矫直效果的影响,研究了弯辊量与压下量的关系,为建立中厚板辊式矫直过程的弯辊设定模型奠定了基础。计算结果表明,为了使板材矫直后的残余曲率和残余应力最小化,施加弯辊时要考虑入口压下量的影响。单从降低残余曲率的角度考虑,小压下量和大压下量下都可以施加负弯辊,但正弯辊只适用于小压下量。从控制宽度方向残余应力的角度考虑,正弯辊施加于小入口压下量时弯辊作用明显,为了消除正弯辊对厚度方向残余应力的不利作用,采用正弯辊时入口压下量不宜过大。施加弯辊会增加矫直力,因此设定弯辊量时要考虑矫直机能力的限制。研究发现了弯辊对塑性变形率的影响规律:负弯辊出现了使塑性变形率随着入口压下量的增加而减少的阶段,正弯辊可消除塑性变形率为零的阶段。 相似文献
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Bending process is one of the most significant fields of application of sheet metal die. Sheet metals are exposed to some spring-back or spring-forward depending on elastic deformation following bending process. S235JR (1.0038) materials having a thickness of 4 mm were bent with 90° punches having 5 different tip radiuses. The bending process was carried out by making the punch waited on the material for 30 s (30 s wait bending) and by removing the punch without waiting (direct bending). Specimens were prepared in three forms as non-heat-treated, normalized and tempered. At the same time, all experiments were performed at a deformation speed of 25 mm/min. As a result, it was determined that as punch tip radius increased, the amount of spring-forward decreased. Although normalizing process applied to specimens increased the amount of spring-forward, tempering process decreased it. The amount of spring-forward was decreased in 30 s wait bending process. 相似文献
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针对双机架平整机生产极薄规格带钢时表面出现的羽痕缺陷生成机理进行了分析。通过研究发现,羽痕生成是由于极薄规格带钢在宽度方向上由轧制力和张力共同作用下出现不均匀变形,该变形产生的分界线在平整过程中出现了不均匀延伸;而在平整过程中由于弯辊和窜辊的预设定参数不合理、单位张力设定偏低、平整过程中弯辊力与轧制力不匹配等因素导致带钢局部延伸偏大,形成了明显的浪形,此浪形若经过平整机辊缝碾压则生成羽痕缺陷。通过将平整机设定张力提高30%、调整板形曲线为1~8 IU的大边浪、依照带钢厚度调整平整机板形预设定参数以及开发轧制力弯辊力跟随控制模型等措施,极薄规格带钢羽痕缺陷带出品由 206降至51 t/月,基板表面质量满足了国内外多家高端用户的要求。 相似文献
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With the aid of elastic plastic large deformation finite element method (FEM), an elastic plastic and coupling thermo mechanical model was built to calculate the bending process of the bent pipe, combining with local heating or cooling of the bent pipe. Based on the FEM simulation, the metal deformation during the bending process was analyzed in detail. The thinning and thickening ratio of the pipe wall thickness, the ovality of the cross section of the pipe and the spring back angle, etc, are presented. 相似文献
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The cold compression test of a strain rate 1s-1 for graphitized carbon steel containing C of 0. 43 mass% with ferrite and graphite was carried out using Gleeble- 3500 thermal simulation machine, the characteristics of the stress- strain relationship was analyzed, and metallographic analysis in the large deformation zone of the compressed samples with different reduction was investigated by optical microscope, field emission scanning electron microscopy and micro hardness tester. The results show that there exists peak stress on the stress- strain curve, namely, 645MPa, the corresponding peak strain is 0. 43; in process of the compressive deformation, morphologies of ferrite and graphite in the large deformation zone on the longitudinal section of the compressed samples gradually become fibrous with increasing the reduction; thereinto, the deformation of graphite particles is realized by means of sliding deformation between basic planes of graphite, shear deformation between substructures of graphite particles, as well as elongation of compacted section near the base of the ferrite of the deformed graphite particles; microhardness of ferrite increases with increasing the reduction, it indicate that ferrite is in a state of hardening, but, increase amplitude of microhardness in the process of compressive deformation after peak stress is decreased. Therefore, based on increase amplitude of microhardness of ferrite and microstructure of the deformed graphite particles, it can be concluded that in process of the compressive deformation after peak stress, deformation of graphite particles in the large deformation zone plays a major role, a deformation of ferrite plays a secondary role (it is mainly to coordinate the deformation of graphite particles), this is one of the main reason that stress decreases in the compressive deformation after peak stress. 相似文献