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.

scholarly journals Materials for Automotive Lightweighting

2019 ◽  
Vol 49 (1) ◽  
pp. 327-359 ◽  
Author(s):  
Alan Taub ◽  
Emmanuel De Moor ◽  
Alan Luo ◽  
David K. Matlock ◽  
John G. Speer ◽  
...  
Keyword(s):  
Galvanic Corrosion ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
New Materials ◽  
Specific Strength ◽  
Advanced High Strength Steels ◽  
Strength And Stiffness ◽  
The Cost

Reducing the weight of automobiles is a major contributor to increased fuel economy. The baseline materials for vehicle construction, low-carbon steel and cast iron, are being replaced by materials with higher specific strength and stiffness: advanced high-strength steels, aluminum, magnesium, and polymer composites. The key challenge is to reduce the cost of manufacturing structures with these new materials. Maximizing the weight reduction requires optimized designs utilizing multimaterials in various forms. This use of mixed materials presents additional challenges in joining and preventing galvanic corrosion.

Expulsion Intensity Monitoring and Modeling in Resistance Spot Welding Based on Electrode Displacement Signals

2020 ◽  
Author(s):  
Yu-Jun Xia ◽  
Yan Shen ◽  
Lang Zhou ◽  
Yong-Bing Li
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Low Carbon Steel ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Material Strength ◽  
Low Carbon ◽  
Resistance Spot ◽  
Electrode Displacement

Abstract Weld expulsion is one of the most common welding defects during resistance spot welding (RSW) process especially for high strength steels (HSS). In order to control and eventually eliminate weld expulsion in production, accurate assessment of the expulsion severity should be the first step and is urgently required. Among the existing methods, real-time monitoring of RSW-related process signals has become a promising approach to actualize the online evaluation of weld expulsion. However, the inherent correlation between the process signals and the expulsion intensity is still unclear. In this work, a commonly used process signal, namely the electrode displacement and its instantaneous behavior when expulsion occurs are systematically studied. Based upon experiments with various electrodes and workpieces, a nonlinear relation between the weight of expelled metal and the sudden displacement drop accompanied by the occurrence of weld expulsion is observed, which is mainly influenced by electrode tip geometry but not by material strength or sheet thickness. The intrinsic relationship between this specific signal feature and the magnitude of expulsion is further explored through geometrical analysis, and a modified analytical model for online expulsion evaluation is finally proposed. It is shown that the improved model could be applied to domed electrodes with different tip geometries and varying workpieces ranging from low carbon steel to HSS. The error of expulsion estimation could be limited within ±20.4 mg (±2σ) at a 95% confidence level. This study may contribute to the online control of weld expulsion to the minimum level.

Expulsion Intensity Monitoring and Modeling in Resistance Spot Welding Based on Electrode Displacement Signals

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Yu-Jun Xia ◽  
Yan Shen ◽  
Lang Zhou ◽  
Yong-Bing Li
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Low Carbon Steel ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Material Strength ◽  
Low Carbon ◽  
Resistance Spot ◽  
Electrode Displacement

Abstract Weld expulsion is one of the most common welding defects during the resistance spot welding (RSW) process, especially for high strength steels (HSS). In order to control and eventually eliminate weld expulsion in production, accurate assessment of the expulsion severity should be the first step and is urgently required. Among the existing methods, real-time monitoring of RSW-related process signals has become a promising approach to actualize the online evaluation of weld expulsion. However, the inherent correlation between the process signals and the expulsion intensity is still unclear. In this work, a commonly used process signal, namely, the electrode displacement and its instantaneous behavior when expulsion occurs are systematically studied. Based upon experiments with various electrodes and workpieces, a nonlinear correlation between the weight of expelled metal and the sudden displacement drop accompanied by the occurrence of weld expulsion is observed, which is mainly influenced by electrode tip geometry but not by material strength or sheet thickness. The intrinsic relationship between this specific signal feature and the magnitude of expulsion is further explored through geometrical analysis, and a modified analytical model for online expulsion evaluation is finally proposed. It is shown that the improved model could be applied to domed electrodes with different tip geometries and varying workpieces ranging from low carbon steel to HSS. The error of expulsion estimation could be limited within ±20.4 mg (±2σ) at a 95% confidence level. This study may contribute to the online control of weld expulsion to the minimum level.

State-of-Art High Strength Steel Sheets for the Automotive Application

2007 ◽  
Vol 539-543 ◽  
pp. 4369-4374 ◽  
Author(s):  
Toshiaki Urabe ◽  
Fusato Kitano ◽  
Takeshi Fujita ◽  
Yuji Yamasaki ◽  
Yoshihiro Hosoya
Keyword(s):  
Mechanical Properties ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Grain Structure ◽  
Solid Solution Hardening ◽  
Automotive Application ◽  
Continuous Annealing ◽  
Low Carbon ◽  
Body In White

New type of IF cold-rolled high strength steels (HSSs) with the strength level of 390 and 440MPa have been developed under the chemistry of the extra-low carbon steel containing around 60ppm C with an intentional addition of niobium by hybridizing the precipitation hardening with niobium carbides and the supplemental solid-solution hardening. In this steel, Precipitation Free Zone (PFZ) nearby recrystallized grain boundaries forms during continuous annealing. This structure leads to unique mechanical properties such as lower yielding and superior anti-secondary-work embrittlement under fine grain structure strictly required for the exposed panels in Body-in-White. Principles of the unique mechanical properties of the steel are introduced related with the formation of PFZ during annealing, and the results of further approach to improve them as the state-of-the-art product, which is widely used for the exposed panels in Body in White, are introduced in the paper.

Enhanced Mechanical Properties of a 0.22C-Mn-Si-Cr Low Alloyed Steel Treated by ART and Q&P Processes

2014 ◽  
Vol 1004-1005 ◽  
pp. 203-208
Author(s):  
Bai Feng An ◽  
Gu Hui Gao ◽  
Xiao Lu Gui ◽  
Zhun Li Tan ◽  
Bing Zhe Bai
Keyword(s):  
Retained Austenite ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Total Elongation ◽  
Alloyed Steel ◽  
Low Carbon ◽  
Multiphase Microstructure ◽  
Element Enrichment ◽  
Low Alloyed Steel

There is a currently desirable demand for high strength steels with good ductility reduce the weight of steel parts for automobile and train applications. Retained austenite in steels can improve the toughness and plasticity. The austenite reverse transformation + quenching and partitioning (ART + Q&P) process was treated on a 0.2C-Mn-Si-Cr low alloyed steel, a multiphase microstructure composed of intercritical ferrite (IF), martensite, bainite and retained austenite (RA) can be obtained in the low carbon steel. Microstructures of the steel treated by different heat treatments were characterized by SEM and XRD. Results show that the formation of RA in low alloy steel depends on the following: (1) the enrichment of the carbon and manganese in the reversed austenite during the ART step; (2) the secondary enrichment of carbon in retained austenite during the following Q&P step. High fraction of RA (14vol.%) was obtained through the two-step element enrichment treatment (ART + Q&P). Due to continuous TRIP effect of RA during the deformation, a good combination of strength and plasticity was achieved in our works: the product of strength and elongation is greater than 35 GPa•%, the tensile strength is more than 1230 MPa, the yield strength greater than 890 MPa, the total elongation is about 28.6%.

Trimming of Advanced High Strength Steels

2005 ◽  
Author(s):  
Sergey F. Golovashchenko ◽  
Andrey M. Ilinich
Keyword(s):  
Carbon Steel ◽  
Low Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Advanced High Strength Steels ◽  
Stretch Flanging ◽  
Alternative Materials ◽  
The Impact ◽  
Current Standards

Modern product design and manufacturing often utilizes a wide variety of materials. Where once low carbon steel predominated, a variety of different materials such as aluminum alloys and advanced high-strength steels (AHSS) are now being utilized. Although such alternative materials may provide a variety of benefits in manufacturing and design, these same materials may present difficulties when subjected to manufacturing processes originally designed for low carbon steel. One such manufacturing area where difficulties may arise is in trimming operations. A defect that may arise directly in the trimming operation are burrs. Burrs decrease the quality and accuracy of stamped parts and cause splits in stretch flanging and hemming. Current standards limit the production of burrs through accurate alignment of the upper and lower edges of the trim knives. The clearance between the shearing edges should be less than 10% of the material thickness. For automotive exterior sheet, this requires a gap less than 0.06mm. Unfortunately, tolerances often exceed the capabilities of many trim dies resulting in the production of burrs. To satisfy the current standards of quality and to meet customer satisfaction, stamped parts frequently need an additional deburring operation, which is often accomplished as a metal-finish operation and conducted manually. The objective of the research described in this paper was to study the mechanisms of burr generation and the impact on AHSS formability in stretch flanging. Results on both the conventional trimming process and a recently developed robust trimming process, which has the potential to expand tolerances of trim die alignment, will be discussed.

scholarly journals Comprehensive Analysis of the Microstructure and Mechanical Properties of Friction-Stir-Welded Low-Carbon High-Strength Steels with Tensile Strengths Ranging from 590 MPa to 1.5 GPa

2021 ◽  
Vol 11 (12) ◽  
pp. 5728
Author(s):  
HyeonJeong You ◽  
Minjung Kang ◽  
Sung Yi ◽  
Soongkeun Hyun ◽  
Cheolhee Kim
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Joint Strength ◽  
Solid Phase ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
Friction Stir ◽  
Welding Processes

High-strength steels are being increasingly employed in the automotive industry, requiring efficient welding processes. This study analyzed the materials and mechanical properties of high-strength automotive steels with strengths ranging from 590 MPa to 1500 MPa, subjected to friction stir welding (FSW), which is a solid-phase welding process. The high-strength steels were hardened by a high fraction of martensite, and the welds were composed of a recrystallized zone (RZ), a partially recrystallized zone (PRZ), a tempered zone (TZ), and an unaffected base metal (BM). The RZ exhibited a higher hardness than the BM and was fully martensitic when the BM strength was 980 MPa or higher. When the BM strength was 780 MPa or higher, the PRZ and TZ softened owing to tempered martensitic formation and were the fracture locations in the tensile test, whereas BM fracture occurred in the tensile test of the 590 MPa steel weld. The joint strength, determined by the hardness and width of the softened zone, increased and then saturated with an increase in the BM strength. From the results, we can conclude that the thermal history and size of the PRZ and TZ should be controlled to enhance the joint strength of automotive steels.

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.

scholarly journals Laser Welding Dissimilar High-Strength Steel Alloys with Complex Geometries

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 792 ◽  
Author(s):  
Panos Efthymiadis ◽  
Khalid Nor
Keyword(s):  
Carbon Steel ◽  
Laser Welding ◽  
Cross Sections ◽  
High Carbon Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Low Carbon ◽  
High Carbon ◽  
Material Chemistry ◽  
Metallurgical Defects

Laser welding of dissimilar high-strength steels was performed in this study for two different geometries, flat and circular samples with material thicknesses of 5 and 8 mm. The material combinations were a low carbon to a medium or high carbon steel. Three different welding systems were employed: a Nd:YAG, a CO2 and a fiber laser. The process stability was evaluated for all the experiments. The resulting full penetration welds were inspected for their surface quality at the top and bottom of the specimens. Cross sections were taken to investigate the resulting microstructures and the metallurgical defects of the welds, such as cracks and pores. Significant hardening occurred in the weld region and the highest hardness values occurred in the Heat Affected Zone (HAZ) of the high carbon steel. The occurrence of weld defects depends strongly on the component geometry. The resulting microstructures within the weld were also predicted using neural network-simulated Continuous Cooling Transformation (CCT) diagrams and predicted the occurrence of a mixture of microstructures, such as bainite, martensite and pearlite, depending on the material chemistry. The thermal fields were measured with thermocouples and revealed the strong influence of component geometry on the cooling rate which in term defines the microstructures forming in the weld and the occurring hardness.

Sign in / Sign up

Export Citation Format

Share Document