Sensitivity Analysis of Effect Related with Material Process and Assembly Variations to Loads Deformation and Stress on HSS Stamping Die

During stamping process, the material properties, process design parameters and production environments inevitably have variation and noisy factors, which possibly affect the sheet metal formability and the deformation of the die structure.After gaining a success in applying sheet metal forming numerical simulation analysis to get the forming loads during stamping process, a methodology of die structure analysis based on sheet metal forming simulation was proposed and validated by experiments.Based on these results, the effect related with initial blank thickness, blank holder force, blank positioning error and die alignment error variations to a DP600 hyperbolic bottomed cup drawing die's forming loads(especially unbalanced loads), and deformation and stress was studied numerically.The influence level of these variations to the die's forming loads, deformation and stress was disclosed.The findings can guide die design, die tryout and process control for high-strength steel(HSS) stamping with increased forming load and decreased sheet metal formability.     

Wave slamming loads on wave-piercer catamarans operating at high-speed determined by hydro-elastic segmented model experiments

Catamaran vessels operating at high-speed can be exposed to deck diving and bow damage and one resolution of this problem is the wave-piercer design of INCAT Tasmania. Owing to the complexity of the unsteady non-linear flow in the bow area during large wave encounter model testing has been undertaken to identify the peak dynamic slam loads on the ship structure. This paper provides experimental benchmark information relating to the wave slam loads on wave-piercing catamaran ferries. Since the time frames of transient slam loadings and whipping vibration of the entire hull in its first bending mode are similar it is important that the test model replicates the whipping response and therefore needs to be a hydro-elastic model. A 2.5 m hydro-elastic segmented catamaran model has been developed based on the 112 m INCAT Tasmania wave-piercer catamaran to establish the peak wave slamming loads acting on the full-scale vessel. Towing tank tests were performed in regular seas at a maximum full-scale operating speed of 38 knots. The model was instrumented to measure the dynamic slam loads acting on the centre bow and vertical bending moments acting in the demihulls of the catamaran model as a function of wave frequency and wave height. Peak slam loads measured on the centre bow were found to approach the total weight of the model, this being a broadly similar result to the peak loads measured at full-scale. It was found that global dimensionless heave and pitch accelerations peaked in the same range of encounter frequency as did the peak slam load.     

道路软土地基处治方法综论

本文从工程实际出发,分析了道路工程中软土地基的几种处治方法,对不同处治方法的应用范围及施工工艺进行了介绍,指出软土地基的处治必须结合道路的工程实际加以确定,才能有效地保证路基的稳定性。     

破损船体剩余强度衡准研究

本文研究了船体破损非对称淹水和刚度损失引起的船体外载荷变化,并利用破损船体非对称弯曲极限强度计算方法详细分析碰撞、搁浅和爆炸破损对船体极限强度的影响.然后基于破损船体极值载荷和极限强度,给出破损船体剩余强度衡准,并对破损船体临界海况进行预报.     

倾斜荷载下基桩P-Δ效应等效剪力有限元迭代法研究

假定桩身位移为三次幂函数,结合倾斜偏心荷载下单桩受力微分方程确定的桩身弯矩、剪力与桩身水平位移关系,在此基础上引入等效剪力增量概念,提出了基桩P-Δ效应的等效剪力有限元迭代法,相应编制了Matlab分析程序,并结合算例对成层地基中倾斜偏心荷载、桩自重、水平分布荷载、竖向分布荷载和竖向荷载综合作用下基桩内力位移进行了分析。结果表明:等效剪力有限元迭代法用于倾斜荷载下基桩P-Δ效应计算分析是有效的;当墩身较高时,墩身倾斜、墩顶偏心弯矩、水平力等对基桩产生的P-Δ效应显著。     

A unified seakeeping and maneuvering analysis of ships in regular waves

The behavior of a ship in regular waves during maneuvering was studied by using a two-time scale model. The maneuvering analysis was based on Söding’s (Schiffstechnik 1982; 29:3–29) nonlinear slender-body theory generalized to account for heel. Forces and moments due to rudder, propeller, and viscous cross-flow follow from the state-of-the-art procedures. The developed unified theory of seakeeping and maneuvering was verified and validated for calm water by comparing it with experimental and calculated zigzag and circle maneuvers. Linear wave-induced motions and loads were determined by generalizing the Salvesen-Tuck-Faltinsen (Trans SNAME 1970; 78:250–287) strip theory. The mean second-order wave loads in incident regular deep water waves in oblique sea conditions were estimated by the potential flow theories of Faltinsen et al. (Proc 13th Symp Naval Hydrody 1980), Salvesen (Proc Intl Symp Dynam Mar Vehicl Struct Wave 1974), and Loukakis and Sclavounos (J Ship Res 1978; 22:1–19). The considered theories cover the whole range of important wavelengths. Comparisons between the different mean second-order wave load theories and available experimental data were carried out for different ship hull forms when the ship was advancing forward on a straight course. The mentioned methods have been incorporated into the maneuvering model. Their applicability from the perspective of the maneuvering ability of the selected types of ships was investigated in given wave environments. The wave conditions are valid for realistic maneuvering cases in open coastal areas. It was demonstrated that the incident waves may have an important influence on the maneuvering behavior of a ship. The added resistance, mean second-order transverse force, and yaw moment also play important roles.     

车轮随机动载特性的Simulink仿真分析

利用汽车的两自由度模型，应用Simulink软件仿真分析了车速与路面不平度对车轮随机动载变化趋势的影响。同时也分析了车轮随机动载的大小对路面疲劳应力的影响，指出了不同车速和路面不平度引起的路面动力反应及损伤变化规律，即车速和路面不平度的增加将导致汽车动载的增加，从而加速路面的损伤。提出了针对路面状况调整车速可以降低车轮随机动载，从而达到减轻路面损伤的要求。     

局部砰击载荷预报的规范算法研究与分析

通过比较不同船级社砰击规范的适用范围及要求,对砰击压力展开研究。通过对实例船型的计算和分析,比较不同规范计算得到的艏底和外飘砰击压力。分解砰击压力计算的经验公式,提出对砰击压力有显著影响的参数,比较这些参数对砰击压力影响的程度,以指导砰击载荷作用下船体局部结构的设计实践。     

多功能支持船波浪载荷研究

波浪载荷研究是船舶性能预报和结构安全评估的关键内容。文中利用势流理论直接数值求解多功能支持船遭受的波浪载荷(包括一阶波频力和二阶漂移力),利用统计方法得到波浪载荷的长期预报和短期预报极值,包括波浪总纵弯矩和垂向波浪剪力以用于后续的船舶整体结构安全评估,以及纵向漂移力、横向漂移力和首摇漂移力矩用于船舶的动力定位能力分析中。研究结果表明:求解波浪载荷的势流理论方法精确,能为后续的船舶性能预报和结构安全评估提供可靠的载荷输入。     

船首形状对船-冰碰撞性能的影响研究

基于冰的各向同性弹性断裂模型,分别以船首的初速度和冰的厚度为变量,采用LS-DYNA非线性有限元软件对不同船首形状与冰排碰撞问题展开数值模拟研究。研究结果表明,不同形状船首在相同工况下其破冰距离、受到的冰载荷以及能量变化有显著差异。前倾首、飞剪首的破冰能力比直立首、球鼻首强,随着船首初速度的增大、冰厚的增加,飞剪首的破冰能力逐步好于前倾首,球鼻首的破冰能力逐步好于直立首。本文研究对于航行于季节性冰区的船舶具有一定的指导意义。