Cyclic strength of parts with overlapping zones formed by roller burnishing

The authors study residual stresses in and cyclic strength of shaft with overlapping zones formed during roller burnishing. The most significant decrease in fatigue strength is shown to occur in the presence of an overlapping zone with the areas arising due to a lowered roller burnishing pressure in the second pass. __________ Translated from Problemy Prochnosti, No. 3, pp. 144–148, May–June, 2006.     

Experimental study of composite cold-formed steel C-section floor joists

Twelve large-scale slab specimens and twenty-two companion push-out specimens were tested to study the behavior and capacity of composite slab joists consisting of cold-formed steel C-sections and concrete. Four shear transfer mechanisms, including surface bond, pre-fabricated bent-up tabs, pre-drilled holes, and self-drilling screws, were employed on the surface of the flange embedded in the concrete to provide shear transfer capacity. Results indicated that specimens employed with shear transfer enhancements showed a marked increase in strength and reduced deflection compared with those relying only on a natural bond between steel and concrete to resist shear. Of the three shear transfer enhancements investigated, bent-up tabs provided the best performance at both the strength and serviceability limit states, followed by drilled holes in the embedded flanges. The use of self-drilling screws resulted in the lowest strength increase. The correlation of shear transfer capacity of push-out specimens with the ultimate capacity of large-scale specimens indicated that the average experimental flexural capacity of the slab specimens was approximately 1.16 times the average predicted value based on push-out test results.     

Elastoplastic Finite Element Analysis and Strength Evaluation of Adhesive Butt Joints of Similar and Dissimilar Hollow Shafts Subjected to External Bending Moments

Stress distributions and deformation of adhesive butt joints are analyzed by an elastoplastic finite element method when the joints of similar and dissimilar shafts are subjected to external bending moments. The effects of the ratio of Young's modulus for the adherends to that for an adhesive and the effects of the adhesive thickness on the interface stress distribution are investigated. Joint strength is predicted by using the elastoplastic interface stress distributions. It is found that the singular stress at the edge of the interfaces increases with an increase of the ratio of Young's modulus. Measurement of strains in joints and experiments on joint strength were conducted. The numerical results are in fairly good agreement with the experimental results. It is observed that the joint strength for dissimilar shafts are smaller than those for similar shafts. A fracture of dissimilar adhesive up-bonded shafts occurred from the interface of the adherend with smaller Young's modulus. It is seen that joint strength increases as the adhesive thickness increases.     

汽轮发电机组轴系中心测量优化调整系统

介绍了一种汽轮发电机组轴系中心测量优化调整系统 ,既可用手持检测仪进行机组轴系中心的测量计算 ,并将数据传输至计算机 ;亦可直接用计算机进行检测 ,进行机组轴系中心的优化调整及数据管理     

立井 4m 深孔爆破参数研究及应用

通过对深孔装药爆破作用特性的分析，利用爆炸动力学推出了立井深孔爆破参数，并在工程试验中获得较好的效果。     

双抽可调式汽轮机控制系统整定研究

介绍双抽可调式汽轮机通过蒸汽图确定各电、热负荷解耦控制参数的方法，并通过实例给出具体计算过程，对比例常数和边界条件进行了分析。由于该方法采用前馈 反馈控制模式，不要求解耦公式达到很高的精度，因此有助于解决生产中的实际问题。     

城市隧道竖井送排式通风优化

为了更有效地发挥送排风竖井在城市隧道中的通风作用,选择合理的送排风组合是一个重要的途径。本文采用CFD方法,对5种排风速度与5种送风速度的25种送排风组合进行了模拟,分析了不同送排风组合隧道内的通风效果。模拟结果表明:当送排比大于1时,隧道内会出现回流,且送排比越大,隧道回流效应越强,经济效益越低。隧道内气流分布和污染物浓度都与送排风组合有关,较大的排风速度虽有利于降低污染物浓度,但能耗也较大,过大或者过小的送风速度都会使隧道局部污染物浓度过高,降低通风作用。因此,综合考虑隧道通风经济性和实用性,确定排风速度为5~6m/s和送风速为8~12m/s为最优组合。选择合理的送排风组合,不仅能有效控制隧道污染物浓度,还能减少能量损失,对城市隧道的建设具有指导意义。     

Base resistance of drilled shafts in soft rock using in situ load tests: A limit state approach

This paper presents a probabilistic limit state framework for the evaluation of the base resistance of drilled shafts in soft rock. In situ load tests and the Griffith fracture theory are used to evaluate the mode of failure for the rock mass under the drilled shaft base. The base resistance or the limit state in the context of this paper is defined by the contact pressure at which load induced vertical to subvertical cracks form and the contact pressure-displacement relationship passes into a steep and fairly straight tangent. The parameters affecting the base resistance are evaluated using an in situ load test database. A statistical approach using the maximum likelihood method is utilized for the development of the design model for the base resistance. Reliability analysis is used to calibrate the corresponding resistance factors. The in situ load tests and the Griffith fracture theory suggest that the soft rock mass underlying the drilled shaft base primarily fails by the formation of vertical to subvertical cracks. Field observations indicate that the displacements in the underlying rock mass are largely in the vertical direction and that the base displacements required to mobilize the proposed base resistance are generally less than 30 mm. Load test data show that the base resistance is chiefly related to the unconfined compressive strength of soft rock. The calculated resistance factors are found to slightly decrease with increase in the span length of the structure and increase with the increase in the foundation redundancy.     

回弹法检测长龄期混凝土抗压强度的探讨与工程实践

参照行业标准(JGJ/T 23-2001)和地方标准(DB21/T834-2000),计算了实际工程长龄期混凝土的换算强度,并与芯样换算抗压强度进行了比较;提出了拓展回弹法检测长龄期混凝土抗压强度技术应用范围的建议.     

300 MW国产引进型机组轴瓦振动诊断与处理

国产引进型300 MW机组6、7号瓦普遍存在振动、不稳现象.针对此类型机组6、7号瓦振动突升之故障,对其进行跟踪测试,找出了故障原因及故障诱发因素,并加以消除,减小了6、7号瓦振动.该方法对同类型机组故障的诊断及排除具有借鉴意义.