Failure Mechanism of Laser Welds in Lap-Shear Specimens of a High Strength Low Alloy Steel

Author(s):  
Kamran Asim ◽  
Jaewon Lee ◽  
Jwo Pan

In this study, the failure mechanism of laser welds in lap-shear specimens of a high strength low alloy (HSLA) steel under quasi-static loading conditions is examined based on the experimental results. Optical micrographs of the welds in specimens before tests were examined to understand the microstructure near the weld. A micrographic analysis of the failed welds in lap-shear specimens indicates a ductile necking/shear failure mechanism near the heat affected zone. Micro-hardness tests were conducted to provide an assessment of the mechanical properties of the joint area which has varying microstructure due to the welding process. A finite element analysis was also carried out to identify the effects of the weld geometry and different mechanical properties of the weld and heat affected zones on the failure mechanism. The computational results of the finite element analysis indicate that the material inhomogeneity and geometry of the weld bead play an important role in the ductile necking/shear failure mechanism. The computational results match well with the experimental observations of the necking/shear failure and its location. A finite element analysis with consideration of void nucleation and growth based on the Gurson yield function was also carried out. The results of the finite element analysis based on the Gurson yield function are in good agreement with the experimental observations of the initiation of ductile fracture and its location.

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Jaewon Lee ◽  
Kamran Asim ◽  
Jwo Pan

In this study, the failure mechanism of laser welds in lap-shear specimens of a high strength low alloy (HSLA) steel under quasi-static loading conditions is examined based on the experimental and computational results. Optical micrographs of the welds in the specimens before tests were examined to understand the microstructure near the weld. A micrographic analysis of the failed welds in lap-shear specimens indicates a ductile necking/shear failure mechanism near the heat affected zone. Micro-hardness tests were conducted to provide an assessment of the mechanical properties of the joint area which has varying microstructure due to the welding process. A finite element analysis was also carried out to identify the effects of the weld geometry and different mechanical properties of the weld and heat affected zones on the failure mechanism. The results of the finite element analysis show that the geometry of the weld protrusion and the higher effective stress–plastic strain curves of the heat affected and weld zones result in the necking/shear failure of the load carrying sheet. The deformed shape of the finite element model near the weld matches well with that near a failed weld. A finite element analysis based on the Gurson yield function with consideration of void nucleation and growth was also carried out. The results of the finite element analysis indicate that the location of the material elements with the maximum void volume fraction matches well with that of the initiation of ductile fracture as observed in the experiments.


e-Polymers ◽  
2017 ◽  
Vol 17 (1) ◽  
pp. 83-88
Author(s):  
Yi-Chang Lee ◽  
Ho Chang ◽  
Ching-Long Wei ◽  
Rahnfong Lee ◽  
Hua-Yi Hsu ◽  
...  

AbstractThe molecular chains of a highly oriented polymer lie in the same direction. A highly oriented polymer is an engineering material with a high strength-to-weight ratio and favorable mechanical properties. Such an orthotropic material has biaxially arranged molecular chains that resist stress in the tensile direction, giving it a high commercial value. In this investigation, finite element analysis (FEA) was utilized to elucidate the deformation and failure of a highly oriented polymer. Based on the principles of material mechanics and using the FEA software, Abaqus, a solid model of an I-beam was constructed, and the lengths of this beam were set based on their heights. Three-point bending tests were performed to simulate the properties of the orthotropic highly oriented polymer, yielding results that reveal both tension failure and shear failure. The aspect ratio that most favored the manufacture of an I-beam from highly oriented polymers was obtained; based on this ratio, a die drawing mold can be developed in the future.


2011 ◽  
Vol 94-96 ◽  
pp. 2153-2156
Author(s):  
Dong Ling Yu

The mainframe of high-pressure grouting machine used for daily ceramics is the main load bearing member, and it has high strength and stiffness requirements. The finite element static analysis on mainframe is discussed in this paper for researching its stress and transfiguration. The result can provide reference for design, and the discussion has some generality and practical value engineering.


2010 ◽  
Vol 163-167 ◽  
pp. 1029-1032
Author(s):  
He Meng ◽  
Kun Yang ◽  
Qing Xuan Shi ◽  
Jin Jie Men

The finite element analysis of high-strength concrete columns confined by high-strength spiral lateral ties under concentric compression is introduced in this paper. The variables of tie strength, tie spacing and tie configuration influencing the characteristics of confined concrete are discussed; and the stress distributions of lateral ties and concrete at cross-section are analyzed. Compared with the test results, this finite element analysis can predict well the behavior of axially loaded concrete confined by lateral ties. It’s indicated that after peak load, normal stirrups loss the effective constraint on concrete due to yielding early, while the high-strength stirrups can continue to provide larger constraint which can improve significantly the ductility of confined concrete.


2015 ◽  
Vol 651-653 ◽  
pp. 1090-1095 ◽  
Author(s):  
Vitalii Vorkov ◽  
Richard Aerens ◽  
Dirk Vandepitte ◽  
Joost R. Duflou

Bump bending or step bending is a forming technique that allows making large radius bends in a sheet metal part by means of a series of bends performed close to each other. The bump bending process has been studied by means of both an experimental campaign and finite element analysis. High-strength steel Weldox 1300 and a punch of radius 30 mm have been used. The finite element calculations have been performed with Abaqus using the solid formulation and Implicit/Explicit solvers. The results of the finite element analysis have been validated experimentally by monitoring the bending process using a camera system aligned with the bending line. Experiments were performed on a press-brake with a capacity of 50 metric tons. Deflections of a sheet during and after bending have been measured using the images recorded by the camera. In order to investigate the influence of a new bend on a previously formed bend, experiments have been performed with different distances between two consecutive bends. Based on the experiments, the size of the affected zone for the bend has been measured. The dependence of the distance between two consecutive bends on the resulting global bending angle has been studied. Moreover the influence of the bump distance on the springback has been investigated.


2013 ◽  
Vol 648 ◽  
pp. 59-62
Author(s):  
Qi Yin Shi ◽  
Yi Tao Ge ◽  
Li Lin Cao ◽  
Zhao Chang Zhang

In this study, based on the test of the high strength materials of steel-encased concrete composite continuous beam, the ultimate flexural capacity of 8 composite continuous beams are analyzed by using the finite element analysis software ABAQUS. Numerical results show that it is a very good agreement for the load-deflection curves which obtained by finite element method (FEM) and those by the test results, and the error control is less than 8.5%. When selecting and utilizing appropriate cyclic constitutive model, element model and failure criterion of high strength steel and high strength concrete, the accuracy of the calculation can be improved better.


2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Sang-Sup Lee ◽  
Jiho Moon ◽  
Keum-Sung Park ◽  
Kyu-Woong Bae

The punching shear failure often governs the strength of the footing-to-column connection. The punching shear failure is an undesirable failure mode, since it results in a brittle failure of the footing. In this study, a new method to increase the strength and ductility of the footing was proposed by inserting the punching shear preventers (PSPs) into the footing. The validation and effectiveness of PSP were verified through a series of experimental studies. The nonlinear finite element analysis was then performed to demonstrate the failure mechanism of the footing with PSPs in depth and to investigate the key parameters that affect the behavior of the footing with PSPs. Finally, the design recommendations for the footing with PSPs were suggested.


2013 ◽  
Vol 712-715 ◽  
pp. 796-799
Author(s):  
Fuh Kuo Chen ◽  
Shi Wei Liu

Due to the requirement of lightweight in the automotive body structure design, the application of advanced high strength steel (AHSS) has been widely adopted in the automotive industry. However, the technical difficulties are also experienced in the forming process of stamping the advanced high strength steel. One of the major defects is springback. In this study, both the experimental approach and the finite element analysis were adopted to examine the springback phenomenon occurred in the stamping of a front bumper inner made of 590Y advanced high strength steel. The die compensation approach was employed to adjust the amount of springback to make the dimension of the automotive part conforming to the design specification. The accurate dimension of the production part validates the finite element analysis and the die compensation approach adopted in the present study provides a useful guideline for improving the springback defect in the stamping of advanced high strength steel sheets.


2011 ◽  
Vol 250-253 ◽  
pp. 2234-2237
Author(s):  
Hong Hai ◽  
Ying Hua Zhao

The debonding behavior at the interface between fiber-reinforced plastic (FRP) sheet and concrete is a key problem for the application of FRP plate, which has been widely applied in the civil engineering for rehabilitation and retrofitting of conventional structures. This paper presents the experimental and nonlinear finite element analysis results of the CFRP-strengthened high-strength concrete member. On the basis of the test, considering of the adhesive layer, explicit finite element is used for simulating the shear failure of CFRP-strengthened concrete, obtain the whole process of structure deformation development, describe the conformation and development of crack and the failure mode. The FE result coincides with the experimental result.


2014 ◽  
Vol 584-586 ◽  
pp. 1309-1312
Author(s):  
Hong Hai ◽  
Wei Wang

The debonding behavior at the interface between carbon fiber-reinforced plastic (CFRP) sheet and concrete is a key problem for the application of FRP plate, which has been widely applied in the civil engineering for rehabilitation and retrofitting of conventional structures. This paper presents the nonlinear finite element analysis results of the CFRP-strengthened high-strength concrete member. On the basis of the test, considering of the bond-slip relationship, explicit finite element is used for simulating the shear failure of CFRP-strengthened concrete, obtain three-dimensional deformation development diagram, describe the failure mode and the relationship between the shearing bond behavior and concrete strength. The FE results coincide with the experimental results.


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