Fatigue Life Prediction After Laser Forming

2005 ◽  
Vol 127 (1) ◽  
pp. 157-164 ◽  
Author(s):  
J. Zhang ◽  
D. Pirzada ◽  
C. C. Chu ◽  
G. J. Cheng
Keyword(s):  
Fatigue Life ◽  
Sheet Metal ◽  
Low Carbon Steel ◽  
Laser Forming ◽  
Primary Concern ◽  
Low Carbon ◽  
Forming Process ◽  
Proposed Model ◽  
Life Model ◽  
Residual Stresses And Strains

Analysis of the laser forming process has been focused on geometry, yield strength, and microstructure change in the past. However fatigue life has been the primary concern for engineering components in many applications. For laser forming to become a practical rapid prototyping tool, research has to be done to predict fatigue life of sheet metal after laser forming. Microstructure as well as the distribution of residual stresses and strains changes during laser forming process. The current models cannot predict the fatigue life after laser forming accurately because of differences in assumptions. This work presents a model to predict fatigue life of sheet metal after laser forming. Results from microstructure integrated finite element modeling of laser forming are incorporated in the fatigue life model. Low carbon steel is used in this work to validate the model. It is shown that the proposed model can predict the fatigue life of sheet metal after laser forming with good accuracy. The predictions from the model are consistent with experimental results. Effects of laser forming conditions on fatigue life of sheet metal are under investigation.

Microstructure Integrated Modeling of Multiscan Laser Forming

2002 ◽  
Vol 124 (2) ◽  
pp. 379-388 ◽  
Author(s):  
Jin Cheng ◽  
Y. Lawrence Yao
Keyword(s):  
Flow Stress ◽  
Numerical Models ◽  
Flow Behavior ◽  
Fem Simulation ◽  
Constitutive Models ◽  
Low Carbon Steel ◽  
Laser Forming ◽  
Low Carbon ◽  
Forming Process ◽  
Heating And Cooling

Laser forming of steel is a hot forming process with high heating and cooling rate, during which strain hardening, dynamic recrystallization, and phase transformation take place. Numerical models considering strain rate and temperature effects only usually give unsatisfactory results when applied to multiscan laser forming operations. This is mainly due to the inadequate constitutive models employed to describe the hot flow behavior. In this work, this limitation is overcome by considering the effects of microstructure change on the flow stress in laser forming processes of low carbon steel. The incorporation of such flow stress models with thermal mechanical FEM simulation increases numerical model accuracy in predicting geometry change and mechanical properties.

Investigating Bauschinger Effect and Plastic Hardening Characteristics of Sheet Metal under Cyclic Loading

2017 ◽  
Vol 4 (2) ◽  
pp. 1-14 ◽  
Author(s):  
Jasri Mohamad
Keyword(s):  
Cyclic Loading ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Bauschinger Effect ◽  
Low Carbon Steel ◽  
Cyclic Hardening ◽  
Low Carbon ◽  
Forming Process ◽  
Metal Forming Process

To improve sheet metal forming process simulation using finite element method, there is a need to incorporate an appropriate constitutive equation capable of describing the Bauschinger effect and the so-called cyclic transient, derived from a near to actual sheet metal forming process testing tool. A cyclic loading tool has been developed to test and record the characteristics of sheet metal deformation by investigating the Bauschinger effect factors (BEF) and cyclic hardening behaviour. Experimental investigation conducted on low carbon steel and stainless steel demonstrates that the tool is able to record sheet metal behaviour under cyclic loading. The results are analysed for signs of the Bauschinger effect and cyclic hardening effect. It was found that the Bauschinger effect does occur during bending and unbending loadings in sheet metal forming process.

Influence of Segmented Blank Holder for Rectangular Box Drawing

2011 ◽  
Vol 189-193 ◽  
pp. 2495-2498
Author(s):  
Xi Ning Li ◽  
L.X. Liu ◽  
J.P. Wang ◽  
C.Y. Jiang ◽  
Z.Q. Wang
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Orthogonal Experiment ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Forming Process ◽  
Blank Holder ◽  
Forming Simulation ◽  
Straight Segments

Blanker holder force (BHF) is one of the important parameters in sheet metal forming process, which is loaded by blanker holder in order to avoid wrinkling. With the development of technology, segmented blanker holder is applied to complicated product forming in order to improve the parts quality. On the basis of analyzing the character of rectangle box forming, the blank holder was divided eight portions, including 2 long straight segments, 2 short straight segments and 4 corners, which each part can separately move. Then the forming simulation of the low carbon steel rectangular box with segmented constant BHF was conducted using orthogonal experiment and considering test conditions. After the results were analyzed according to the thinnest level of the parts, the influence of the segmented blank holder on rectangular box forming was obtained. It indicates that the segmented blank holder has the ability of the local control to sheet metal forming, and can effectively adjust material flow and the strain distribution.

The Effect of Small Defects on Fatigue Life of a Low Carbon Steel

2019 ◽  
Author(s):  
Natalia Gonçalves Torres ◽  
Vinícius Rodrigues ◽  
Edgar Mamiya
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Low Carbon Steel ◽  
Low Carbon

Measurement and Calculation of Elastic Properties in Low Carbon Steel Sheet

2005 ◽  
Vol 495-497 ◽  
pp. 1591-1596 ◽  
Author(s):  
Vladimir Luzin ◽  
S. Banovic ◽  
Thomas Gnäupel-Herold ◽  
Henry Prask ◽  
R.E. Ricker
Keyword(s):  
Carbon Steel ◽  
Elastic Property ◽  
Elastic Properties ◽  
Steel Sheet ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Forming Process ◽  
Element Analysis ◽  
Wide Range ◽  
Carbon Steel Sheet

Low carbon steel (usually in sheet form) has found a wide range of applications in industry due to its high formability. The inner and outer panels of a car body are good examples of such an implementation. While low carbon steel has been used in this application for many decades, a reliable predictive capability of the forming process and “springback” has still not been achieved. NIST has been involved in addressing this and other formability problems for several years. In this paper, texture produced by the in-plane straining and its relationship to springback is reported. Low carbon steel sheet was examined in the as-received condition and after balanced biaxial straining to 25%. This was performed using the Marciniak in-plane stretching test. Both experimental measurements and numerical calculations have been utilized to evaluate anisotropy and evolution of the elastic properties during forming. We employ several techniques for elastic property measurements (dynamic mechanical analysis, static four point bending, mechanical resonance frequency measurements), and several calculation schemes (orientation distribution function averaging, finite element analysis) which are based on texture measurements (neutron diffraction, electron back scattering diffraction). The following objectives are pursued: a) To test a range of different experimental techniques for elastic property measurements in sheet metals; b) To validate numerical calculation methods of the elastic properties by experiments; c) To evaluate elastic property changes (and texture development) during biaxial straining. On the basis of the investigation, recommendations are made for the evaluation of elastic properties in textured sheet metal.

Laser Forming for Flexible Fabrication

2000 ◽  
Vol 16 (02) ◽  
pp. 97-109
Author(s):  
Koichi Masubuchi ◽  
Jerry E. Jones
Keyword(s):  
Three Dimensional ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
Cost Benefit ◽  
Network Models ◽  
High Strength ◽  
Laser Forming ◽  
Low Carbon ◽  
Flat Plates ◽  
Neural Network Models

A 36-month program supported by the Defense Advanced Research Projects Agency (DARPA) was conducted to demonstrate the feasibility to predictably laser form a variety of ferrous and non-ferrous metals of different thickness. Laser forming provides a method of producing complex shapes in sheet, plate, and tubing without the use of tooling, molds, or dies. By heating a localized area with a laser beam, it is possible to create stress states that result in predictable deformation. This research program has developed, refined and demonstrated constitutive and empirical, and neural network models to predict deformation as a function of critical parametric variables and established an understanding of the effect of laser forming on some metallurgical properties of materials. The program was organized into two, time-phased tasks. The first task involved forming flat plates to one-dimensional (I -D) shapes, such as, hinge bends in various materials including low-carbon steel, high-strength steels, nickel-based super alloys, and aluminum alloys. The second task expanded the work conducted in the first task to investigate three-dimensional (3-D) configurations. The models were updated, 3-D specimens fabricated and evaluated, and cost benefit analyses were performed.

Thermal Fatigue and Fracture Mechanics Analysis of Aluminium Alloy

2011 ◽  
Vol 201-203 ◽  
pp. 2476-2480
Author(s):  
Wen Xiao Zhang ◽  
Guo Dong Gao ◽  
Guang Yu Mu
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Fracture Mechanics ◽  
Thermal Fatigue ◽  
Low Carbon Steel ◽  
Strain Range ◽  
J Integral ◽  
Low Carbon ◽  
Thermal Fatigue Life ◽  
Energy Aspect

The in-phase and out-of-phase thermal fatigue of aluminum alloy were experimentally studied. The fatigue life was evaluated analytically by using the elastic-plastic fracture mechanics method (mainly J integral). The results of experiments and calculations showed that the life of out-of-phase fatigue was longer than that of in-phase fatigue within the same strain range. This is the same as the results of other materials such as medium and low carbon steel. On the other hand, the predicted life was consistent with experimental results. This suggests that J integral as a mechanics parameter for characterizing the thermal fatigue strength of aluminum alloy and the calculation method developed here is efficient. A parameter ΔW was proposed from energy aspect to characterize the capacity of crack propagation. The in-phase thermal fatigue life was the same as the out-of-phase thermal fatigue life for identical ΔW values.

scholarly journals FEM Simulation of the Riveting Process and Structural Analysis of Low-Carbon Steel Tubular Rivets Fracture

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 374
Author(s):  
Jaroslaw Jan Jasinski ◽  
Michal Tagowski
Keyword(s):  
Carbon Steel ◽  
Fracture Mechanism ◽  
Fem Simulation ◽  
Low Carbon Steel ◽  
Structural Defects ◽  
Composition Analysis ◽  
Assembly Process ◽  
Low Carbon ◽  
Forming Process ◽  
Explicit Integration

Riveted joints are a common way to connect elements and subassemblies in the automotive industry. In the assembly process, tubular rivets are loaded axially with ca. 3 kN forces, and these loads can cause cracks and delamination in the rivet material. Such effects at the quality control stage disqualify the product in further assembly process. The article presents an analysis of the fracture mechanism of E215 low-carbon steel tubular rivets used to join modules of driver and passenger safety systems (airbags) in vehicles. Finite element method (FEM) simulation and material testing were used to verify the stresses and analysis of the rivet fracture. Numerical tests determined the state of stress during rivet forming using the FEM-EA method based on the explicit integration of central differences. Light microscopy (LM), scanning electron microscopy (SEM) and chemical composition analysis (SEM-EDS) were performed to investigate the microstructure of the rivet material and to analyze the cracks. Results showed that the cause of rivet cracking is the accumulation and exceeding of critical tensile stresses in the rivet flange during the tube processing and the final riveting (forming) process. Moreover, it was discovered that rivet fracture is largely caused by structural defects (tertiary cementite Fe,Mn3CIII along the boundaries of prior austenite grains) in the material resulting from the incorrectly selected parameters of the final heat treatment of the prefabricate (tube) from which the rivet was produced. The FEM simulation of the riveting and structural characterization results correlated well, so the rivet forming process and fracture mechanism could be fully investigated.

The Initial Life and Short Crack Propagation Life for Low Carbon Steel Based on Dislocation Method

2018 ◽  
Vol 1145 ◽  
pp. 1-7
Author(s):  
Yuan Long Yang ◽  
Qing Chun Meng ◽  
Wei Ping Hu
Keyword(s):  
Fatigue Life ◽  
Carbon Steel ◽  
Crack Propagation ◽  
Low Carbon Steel ◽  
Short Crack ◽  
Low Carbon ◽  
Grain Sizes ◽  
Steel Material ◽  
The Relationship ◽  
Good Agreement

In the paper, the relationship between the grain size and fatigue life are studied. To specify the initial and short crack propagation life of low carbon steel material, three methods are used in the simulation. At first, the K. Tanaka’s model is introduced to calculate the fatigue life of a grain. Then, the Voronoi Diagram is used to generate the microstructure of grains. At last, a criteria to specify the short crack is proposed. Based on these methods, the numerical simulation is conducted. With the help of the process, the grain sizes are generated randomly in order to specify how grain sizes effect fatigue life. The computational results are in good agreement with the experimental data. The results show that the randomness of fatigue life is closely related to the randomness of grain sizes.

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