Papers by Keyword: Structural Stress

Abstract: Various types of welded joints are of wide application in industrial and productional regions, including T-shaped, butt, and fillet joints of steel, stainless steel, and cast steel. Under cyclic fatigue load, the fatigue performance of welded joints is significant for the engineering design and it’s of interest to investigate the fatigue property of the welded joints using the recommended prediction methods. In this paper, the fatigue performance of welded T-shaped joints is investigated. The mesh-insensitive property of the structural stress method is validated with the comparison of various prediction methods. The fatigue cyclic life of welded T-shaped joints under tensile loads is analyzed. The structural stress curve of T-shaped joints with various base metal thicknesses is determined for the engineering design.

Abstract: Though fatigue failure is often happened in steel gate, fatigue design has not yet been included in design or evaluation standards in China. In this paper, analytical theory based structural stress method and structural stress based fatigue analysis method are combined and employed for fatigue life evaluation of plane steel gate. The variation of water head is taken into consideration for the conditions of gate running and resting. In order to give a valid evaluation, the weld located among all components is considered as rigid connection when calculating structural stress. Master S-N curve in ASME code is used for life evaluation. Example shows the method can be used for fatigue analysis of plane steel gate, and can be used to identify fatigue failure zone.

Abstract: A comparative study among five methods to calculate the structural stress of the trough to deck plate joint in orthotropic steel deck was carried out. The five methods used are surface stress extrapolation method (SSE), Haibach method, Xiao and Yamada method and CAB method. FEM analysis shows the five methods are mesh sensitive. Structural stress calculated using element type solid95 is larger than that of solid45. For fine and medium mesh model, structural stress calculated by Haibach method is larger than other methods, which means a lower fatigue life. Structural stress calculated by Yamada method is lower than other methods, which means a higher fatigue life than that calculated by other methods. For coarse mesh model, structure stress calculated by quadratic extrapolation method is larger than other methods, and, structural stress calculated by Yamada method is much lower than other methods.

Abstract: Based on finite element analysis, the structural stress of 8×8 InSb Infrared Focal Plane Array integrating with microlens arrays dependent on indium bump sizes is systemically researched. Simulation results show that as the diameters of indium bump increase from 16μm to 38μm in step of 2μm, the maximum stress existing in InSb chip first reduces, then increases, and reaches minimum with indium bump diameter 32μm. Yet the maximum stress in the indium bump array is almost unchangeable and keeps at 16.5MPa. The maximum stress in Si readout integrated circuit almost half stress in InSb chip. Besides, the stress appearing on those regions situating just on microlens array is much smaller than its surrounding regions, and the stress distribution is uniform at contacting areas between InSb chip and indium bump.

Abstract: In more and more complicated urban building environment, a new construction method that metro engineering is constructed by large-diameter shield and shallow mining method can be regarded as a great attempt in China. By taking the Gaojiayuan station of Beijing metro line 14 as an engineering background, the main construction steps for the platform of the metro station built by a large-size shield with an outer diameter of 10 m and the Pile-Beam-Arch (PBA) method are introduced. Based on the soil-structure interaction theory, a two-dimensional finite element model is used to simulate the shield tunneling and the platform construction by the PBA method to enlarge the shield tunnel. The ground deformation and structural stress of the platform are predicted. The numerical results can be regarded as a valuable reference for the application of the new construction method in Beijing metro line 14.

Abstract: Based on viscoplastic Anand’s model, the structural stress of 8×8 InSb array detector with underfill dependent on indium bump sizes is systemically researched by finite element method. Simulation results show that as the diameters of indium bump decrease from 36μm to 20μm in step of 2μm, the maximum stress existing in InSb chip first reduces sharply, then increases flatly, and reaches minimum with indium bump diameter 32μm. The maximum stress in Si readout integrated circuit (ROIC) fluctuates at 320MPa with amplitude less than 50MPa, almost half stress in InSb chip. Yet the maximum stress in the indium bump array is almost unchangeable and keeps at 16.3MPa. When the height of indium bump increases from 9μm to 21μm in step of 6μm, the maximal stress in InSb chip first reduces sharply from 800MPa to 500MPa, then almost retains constant. With indium bump diameter 32μm and height 21μm, the maximum stresses in whole 8×8 InSb array detector reaches minimum 458MPa, besides, the stress distribution at the contacts areas is uniform and concentrated, the stress value is smallest and this structure is promising to avoid device invalidation.

Abstract: Two-step method is used to research stress and its distribution in 64×64 InSb infrared focal plane array (IRFPA) employing finite element method. First, a small 8×8 InSb IRFPA is studied by changing indium bump diameters from 24μm to 36μm, with indium bump thickness 20μm and InSb thickness 10μm, the simulated results show that von Mises stress in InSb chip is dependent on indium bump diameters, the varying tendency is just like the letter V, here when indium bump diameters is set to 30μm, the smallest von Mises stress is achieved and its distribution in InSb chip is uniform at contacting areas. Then, InSb IRFPA array scale is doubled once again from 8×8 to 64×64 to learn the effect from array size, thus, the stress and its distribution of 64×64 InSb IRFPA is obtained in a short time. Simulation results show that von Mises stress maximum in InSb chip and Si readout integrated circuit almost do not increases with array scale, and the largest von Mises stress is located in InSb chips. Besides, stress distribution on the bottom surface of InSb chip is radiating, and decreases from core to four corners, and stress value at contacting area is smaller than those on its surrounding areas, contrary to stress distribution on top surface of InSb chip.

Abstract: The structural stress (SS) method developed by BATTELLE has been studied based on small or mid-size scale specimens. In order to apply the new method, such as SS, on an actual project, it should have application results on actual project. However, SS method didn’t have a lot of application data compared to class procedure using hot spot stress (HSS). In order to find out whether the SS method, for the evaluation of fatigue life, can give reasonable results when it is applied under the same loading suggested by classification societies, it was compared with fatigue lives derived by class. ABS & DNV’s simplified fatigue analysis method were adopted to check the validity of SS method. Before applying complicated loading of class, static loading case was applied, since the class method has their own correlation factor for wave loading. And then, simplified fatigue analysis was performed with more complicated loading cases. From the results of fatigue life calculation, it can be said that SS shows reasonable fatigue lives with respect to HSS or notch stress based fatigue lives.

Abstract: In this study, a methodology for the assessment of fatigue failure modes of weldments due to partial penetration weld has been carried out by using structural stress method. Structural stress calculation procedure, using shell element based on equilibrium consideration using nodal forces and moments, is employed. It is important to note that the structural stress calculation procedures for partial penetration welds can be used to determine a minimum weld leg length, beyond which, weld root failure modes can be effectively suppressed. An example study, with respect to a fillet weld leg length design, is compared with a design criterion, and they are found to be in agreement.

Abstract: Some recently developed variants of local concepts for assessing the fatigue strength and structural durability of welded joints are reviewed. These comprise structural stress, notch stress or strain and fracture mechanics concepts. New variants of the structural stress concept are Dong’s gradient stress approach and Xiao-Yamada’s ‘one millimetre stress’ approach. FE meshing rules have been developed for welded joints in thin sheet structures. The concept of fictitious notch rounding is now better substantiated for aluminium alloys. The small-size notch concept is applicable to thin sheet lap joints. The new notch stress intensity factor concept is based on the singular stresses at the sharp weld toe notch. Advanced fracture mechanics concepts combine crack initiation at the seam weld root or nugget edge and crack propagation over the plate thickness resulting in endurable FK values as function of cycles per unit thickness, N/t.