薄板射线照相的最佳黑度

研究了薄板平焊缝在不同条件下Ｘ射线照相底片黑度与射线照相灵敏度之间的关系,发现通过实验方法可以确定不同厚度的平焊缝达到最高灵敏度时底片的黑底范围。     

“射线照相检验技术最佳黑度”的错误

从识别细节的最小黑度差理论和射线标准的有关规定,讨论了一些教材中普遍存在的关于"最佳黑度"叙述的错误。     

射线照相黑度值的重要性及其标准规定值的合理性

黑度是射线照相检验中的一个重要参数，我国射线照相标准中的黑度规定值与国际标准化组织（ISO）和国外标准存在的较大差距。指出该参数与景仰质量和检测有效性、可靠性的利害关系，建议按两种主要焊接接头型式分别规定射线照相许用黑度范围。     

高颈法兰与接管对接焊缝射线照像中的黑度控制

根据国家标准要求，钢制压力容器对接焊缝一般采用射线探伤，因为射线照像底片即具有直观性，又能够永久保存。《GB3323—87》标准中对底片质量有严格的要求，底片黑度值AB级限定在1．2～3．5之间。我们要透照的高颈法兰与接管对接有一定的厚度差（图i），当射线源中心（强度为     

黑度对射线照像底片质量的影响

射线探伤是以射线照像底片来评定探伤结果的。因此，底片质量直接影响检测结果。影响义片质量的因素较多，本文仅就黑度对底片质量的影响进行研究，并对最佳黑度范围等问题进行探讨。     

底片黑度对射线照相灵敏度的影响

射线探伤是以射线照相底片来评定探伤结果的，底片质量是射线探伤的核心要素。影响底片质量的因素有多种，就其中一个因素底片黑度展开探讨，揭示底片黑度对射线照相灵敏度的影响。     

钛合金焊缝X射线照相底片黑度对灵敏度的影响

分析了钛合金焊缝Ｘ射线照相底工对度灵敏度的影响,试验表明,底片的黑度应限制在比标准要求要窄的范围内。     

叠加双片的黑度

当我们对厚度差较大的工件进行射线探伤时,常会采用双片技术,即用一个暗盒内装不同感光度的两张胶片,照相后,对黑度较大部位,用单片观察其影象,而对黑度较小部位,则可将双片重叠进行观察,以有利于缺陷的评定.下面就双片叠加时的黑度进行分析.1 理论分析由黑度定义可知,黑度D=lg(L_0/L)式中 L_0—入射光强度L—透射光强度如附图所示,设1号底片黑度为 D_1,2号底片黑度为D_2,双片叠加时黑度为D_3;那么对于1号底片D_1=lg(L_0/L_1)对于2号底片D_2=lg(L_1/L_2)当1号底片和2号底片叠加时     

论“气缩孔”概念造成的误导

分析了论述了“气缩孔”概念产生的原因及混淆气孔与缩孔形成机理而造成的不良后果，并认为所谓气缩孔不属于气孔类缺陷，是缩孔形成时由于真空作用，伴随有气体被吸入，实际上是一种缩孔现象。气缩孔概念的误导，影响较大，有必要加以澄清，提高铸造理论与经验的指导价值。     

警惕我国重点大学学科建设中的若干误区

近年来 ,我国一批重点大学 ,在创建世界一流大学过程中 ,对学科建设的理论研究重视不够 ,不论是在实践上 ,还是在认识上都存在着一些误区。这些误区主要有 :认为学科门类齐全就是学科布局合理 ;认为学科带头人的学术水平等于学科发展水平 ;认为科学研究水平等于学科发展水平 ;认为有钱就能搞好学科建设。对此 ,我们必须保持高度的警惕 ,并及时在理论上予以廓清。     

Optimum design of welding transformer

Welding transformer is widely used in industry manufacturing,depleting a large Portion of electricity energy.Based on modern computer and mathematical programming,Optimun design of electro-magnetic devicesleads to highly efficient use of energr and materials.Arc welding transformer is optimized here.A mathematical model,considering both productive cost and operating losses,which is called ar Economical-through-Life transformer,is estab-lished.Mixed function method,mixed dispersing variable method and improved orthogonal method have beenapplied to carry out the optimization calculations.Result shows that the power factor is quite important in an Econmi-cal-through-Life transformer,and that some principles must be followed in the design work.Also discussed are the ad-vantages and disadvantages of the three methods.In the end,the prospect of optimum design of welding transformer isforecast.     

牛头刨床的遗传优化设计

牛头刨床中实现刨刀切削运动的关键机构是Ⅱ级六杆机构,它决定了刨刀的工作速度的平稳性,对刨削质量有非常重要的影响。以六杆机构最大压力角尽量小为条件,建立了以刨刀的工作速度平稳性为目标函数的优化设计数学模型,将混沌引入基本遗传算法对其进行了优化设计,在很短的时间内获得了最佳设计方案。     

Optimum design of the multifacet drill

A two-stage strategy has been used to design an optimum multifacet drill (MFD) for crankshaft drilling. In the first stage, a heuristic MFD was developed by adding an additional facet to the outer corner of the conventional split-point drill. Under accelerated life test conditions, this new drill can decrease thrust force by 21.0% and increase drill life by 50% compared to a split-point drill. In the second stage, compre-hensive force models for predicting thrust and torque were modified and developed. Using the force mod-els, point optimization was carried out to design the optimum MFD. This new MFD can further decrease the thrust by 21.3 % over the heuristic MFD, and accelerated life tests haveshowna25% further increase in drill life.     

阶梯式浇注系统的优化设计

通过采用水力学模拟试验 ,本文对目前生产中较通用阶梯式浇注系统的优劣进行了评价 ,提出了较为理想的阶梯式浇注系统结构和设计方法     

Optimum design of headstocks of precision lathes

The optimum designs of headstocks of precision lathes are studied. Three different outer shapes of headstocks are explored. Thermal deformations due to heat generated by spindle bearings are considered. The objective is to minimise the overall deflection of the workpiece at the cutting point. The constraint is to force the fundamental natural frequency much greater than the working frequency in order to reduce dynamic deflections. The design variables include the shape dimensions, the locations of the spindle bearings, the stiffnesses of the spindle bearings, the dimensions of the fins and the locations of the fins. The genetic algorithm is utilised to solve these mixed-variable optimisation problems. Optimum solutions for the three different types of headstocks are found and discussed.