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Viewing 1 to 30 of 3431
2011-04-12
Journal Article
2011-01-0470
Pai-Chen Lin, Ru-Yi He, Zheng-Ming Su, Zhi-Long Lin
Failure modes of spot friction welds in cross-tension specimens of aluminum 6061-T6 sheets are first investigated based on experimental observations. Optical and scanning electron micrographs of the welds before and after failure under quasi-static and cyclic loading conditions are examined. Experimental results show that the failure modes of the welds under quasi-static and cyclic loading conditions are quite different. Under quasi-static loading conditions, the failure mainly starts from the necking of the upper sheet outside the weld. Under low-cycle loading conditions, the dominant fatigue cracks are the kinked cracks growing into the upper sheet from the crack tips; hence, the upper nugget pullout failure mode can be seen. Under high-cycle loading conditions, the dominant fatigue cracks are kinked cracks growing into the lower sheet from the crack tips; subsequently, the lower nugget pullout failure mode can be seen.
2011-04-12
Technical Paper
2011-01-0235
Fadi Abu-Farha, Louis Hector, Paul Krajewski
Forming Limit Curves (FLCs) were developed for the 5083 aluminum alloy at conditions simulating high temperature processes such as superplastic and quick plastic forming. Sheet samples were formed at 450 °C and at a constant strain rate of 5x10-3 s-1, by free bulging into a set of elliptical die inserts with different aspect ratios. Friction-independent formability diagrams, which distinguish between the safe and unsafe deformation zones, were constructed. Although the formability diagrams were confined to the biaxial strain region (right side quadrant of an FLD), the elliptical die insert methodology provides formability maps under conditions where traditional mechanical stretching techniques are limited.
2011-04-12
Journal Article
2011-01-0193
Qigui Wang, Peggy Jones
Cast aluminum alloys are increasingly used in cyclically loaded automotive structural applications for light weight and fuel economy. The fatigue resistance of aluminum castings strongly depends upon the presence of casting flaws and characteristics of microstructural constituents. The existence of casting flaws significantly reduces fatigue crack initiation life. In the absence of casting flaws, however, crack initiation occurs at the fatigue-sensitive microstructural constituents. Cracking and debonding of large silicon (Si) and Fe-rich intermetallic particles and crystallographic shearing from persistent slip bands in the aluminum matrix play an important role in crack initiation. This paper presents fatigue life models for aluminum castings free of casting flaws, which complement the fatigue life models for aluminum castings containing casting flaws published in [1].
2011-04-12
Journal Article
2011-01-0535
L. Rafael Sanchez PhD, Susan Hartfield-Wunsch
During sheet metal forming, the friction and surface roughness change as the sheet slides, bends and stretches against the tools. This study assessed evolution of friction and surface roughness changes on aluminum sheet with two surface finish conditions, mill finish (MF) and electron discharge texture (EDT), in both the longitudinal and the transverse rolling directions of the sheet. The sheets were tested using a three pin Draw Bead Simulator (DBS). Surface roughness of the sheet evolved as a result of bending at the first shoulder, reverse bending at the middle pin, bending at the second shoulder and unbending at the exit. Stretching conditions and sheet-pin contact were also varied to see the impact on surface roughness. In general, the largest surface roughness change for the transverse direction was observed at the convex side of the exit shoulder pin and on the convex side of the first shoulder for the longitudinal direction.
2011-04-12
Journal Article
2011-01-0534
Susan E. Hartfield-Wunsch, Donald Cohen, L. Rafael sanchez PhD, Lars-Erik Brattstrom
Aluminum sheet is commercially available in three surface finishes, mill finish (MF), electric discharge texture (EDT), and dull finish (DF). This surface finish impacts the friction behavior during sheet metal forming. A study was done to compare ten commercially available sheet samples from several suppliers. The friction behavior was characterized in the longitudinal and transverse directions using a Draw Bead Simulator (DBS) test, resulting in a coefficient of friction (COF) value for each material. Characterization of the friction behavior in each direction provides useful data for formability analysis. To quantitatively characterize the surface finish, three-dimensional MicroTexture measurements were done with a WYKO NT8000 instrument. In general, the MF samples have the smoothest surface, with Sa values of 0.20-0.30 μm and the lowest COF values. The EDT samples have the roughest surface, with Sa values of 0.60-1.00 μm, and the highest COF values.
2011-04-12
Journal Article
2011-01-0533
Susan E. Hartfield-Wunsch, Jamie Burdeski, Elgin Miller, Wei Ji
It is important to understand the accuracy level of the formability analysis for any new process so that correct predictions can be made in product and die design. This report focuses on the formability analysis methodology developed for the preform anneal process. In this process, the aluminum panel is partially formed, annealed to eliminate the cold work from the first step, and then formed to the final shape using the same die. This process has the ability to form more complex parts than conventional aluminum stamping, and has been demonstrated on a complex one-piece door inner and a complex one-piece liftgate inner with AA5182-O3. Both panels only required slight design modifications to the original steel product geometry. This report focuses on the formability analysis correlation with physical panels for the liftgate inner, considering both full panel anneal in a convection oven and local annealing of critical areas.
2011-04-12
Journal Article
2011-01-0477
Sri Lathabai, Vinay Tyagi, David Ritchie, Trevor Kearney, Barrie Finnin, Shane Christian, Andrew Sansome, Gary White
Friction stir blind riveting (FSBR) is a new process for joining automotive light alloys based on aluminium and magnesium. During FSBR, a blind rivet, rotating at high speed (typically 2000-12000 rpm), is brought in contact with the upper sheet or workpiece of a lap joint. The frictional heat generated between the rivet and the workpieces softens the material and this, in turn, reduces the force required to drive the rivet into the workpieces. Once fully inserted, the blind rivet is upset using the internal mandrel and an appropriate tool, as in conventional blind riveting. The FSBR process thus retains the one-sided accessibility of conventional blind riveting, but eliminates the extra predrilling and any subsequent cleaning steps required for the latter process.
2013-04-08
Technical Paper
2013-01-1170
Nia R. Harrison, Andrey Ilinich, Peter A. Friedman, Jugraj Singh, Ravi Verma
Traditional warm forming of aluminum refers to sheet forming in the temperature range of 200°C to 350°C using heated, matched die sets similar to conventional stamping. While the benefits of this process can include design freedom, improved dimensional capability and potentially reduced cycle times, the process is complex and requires expensive, heated dies. The objective of this work was to develop a warm forming process that both retains the benefits of traditional warm forming while allowing for the use of lower-cost tooling. Enhanced formability characteristics of aluminum sheet have been observed when there is a prescribed temperature difference between the die and the sheet; often referred to as a non-isothermal condition. This work, which was supported by the USCAR-AMD initiative, demonstrated the benefits of the non-isothermal warm forming approach on a full-scale door inner panel. Finite element analysis was used to guide the design of the die face and blank shape.
2013-04-08
Journal Article
2013-01-1024
Pai-Chen Lin, Zheng-Ming Su, Wei-Jen Lai, Jwo Pan
Fatigue behavior of self-piercing rivets (SPRs) and clinch joints in lap-shear specimens of 6111-T4 aluminum sheets is investigated based on experimental observations and a fatigue life estimation model. Lap-shear specimens with SRPs and clinch joints were tested under cyclic loading conditions. Under cyclic loading conditions, fatigue cracks start from the curved interfacial surface of the upper sheet and then grow into the upper sheet thickness for both self-piercing rivets and clinch joints. The self-piercing rivets and clinch joints fail finally through the circumferential/transverse crack growth in the upper sheets and inner button crack growth, respectively. The structural stress solution and the experimental stress-life data for aluminum 6111-T4 sheets are adopted to estimate the fatigue lives of both types of joints. The fatigue life estimations based on the structural stress model show good agreement with the experimental results.
2004-03-08
Technical Paper
2004-01-0185
Eu-Gene Ng, Mohamed A. Elbestawi, Mihaela Dumitrescu
Advanced manufacturing technology of high silicon aluminium alloys is one of the manufacturing processes in need of new developments to obtain the required improvements for the new generation of vehicles. During ultra high speed machining of aluminium alloys, the optimum machining parameters and tool geometry are controlled by the finished machined workpiece/part surface integrity, burr formation, and part distortion. For the research objectives presented in this paper a dual approach was applied, covering both experimental and theoretical (modeling) work. High speed machining, above 5000 m/min, has been used. From experimental analysis, the most important elements regarding tool life and wear mechanisms are workpiece material microstructure and inhomogenities, non-metallic inclusions, and silicon content.
2004-03-08
Technical Paper
2004-01-0183
Y. Wang, P. K. Mallick
This paper describes the results of dynamic denting experiments conducted on AA5754 and AA6061 alloys. Dynamic denting tests were performed using a drop weight impact machine. The drop height was varied from 38 mm to 914 mm to generate impact velocities ranging from 53.4 m/min to 254 m/min. The dent depth created at different drop heights was related to the input impact energy and peak load observed in the tests. The effects of sheet thickness and yield strength were explored.
2004-03-08
Technical Paper
2004-01-1581
Mike Guo, Ram Bhandarkar, Barry Lin
Loads generated during assembly may cause significant stress levels in components. Under test conditions, these stresses alter the mean stress which in turn, alters the fatigue life and critical stress area of the components as well. This paper describes the Finite Element Analysis (FEA) procedure to evaluate behavior of a cast aluminum wheel subjected to the rotary fatigue test condition as specified in the SAE test procedure (SAE J328 JUN94). Fatigue life of the wheel is determined using the S-N approach for a constant reversed loading condition. In addition, fatigue life predictions with and without clamp loads are compared. It is concluded that the inclusion of clamp load is necessary for better prediction of the critical stress areas and fatigue life of the wheel.
2004-03-08
Technical Paper
2004-01-1025
Zachary Brown, Rathindra DasGupta, Dayne Killingsworth, Mark Musser, Diran Apelian
Semi-solid metal (SSM) casting of aluminum components is currently establishing itself as a viable process for critical applications in the automotive industry. SSM casting processes compete favorably on both cost and performance with other casting techniques including gravity permanent mold (GPM), conventional high pressure die casting (HPDC) and squeeze casting. In this paper the various SSM casting routes in use today are reviewed. The two categories of SSM processes are thixocasting (involves the use of electro-magnetically stirred or grain-refined billets) and rheocasting (slurry produced directly from the liquid phase). The former requires a billet that needs to be reheated and processed, whereas the latter is cast directly from the liquid state. Also described here are new approaches to slurry making. These include the Slurry on Demand (SoD) process from AEMP, the Sub Liquidus Casting (SLCR) process from THT, and Diffusion Solidification.
2004-03-08
Technical Paper
2004-01-1023
Shahrooz Nafisi, Reza Ghomashchi, Jalal Hedjazi, S. M. A. Boutorabi
The effects of Cu-P and Al-Sr master alloys as strong modifiers have been investigated on the microstructure of commercial Al-Si (12-13%Si) alloys. Thermal analysis has been employed to examine the morphological changes of Si particles and identify the optimum concentration of P and Sr to achieve fine and well-distributed eutectic and primary silicon structures. Additions of 0.05% to 0.075% P or Sr have been found to yield the most optimum modification and refining of the structure. The results show that the variation in nucleation temperature of primary phase and the eutectic temperature are the most important parameters.
2004-03-08
Technical Paper
2004-01-1022
H. Mancha-Molinar, H. F. López, A. Silva, K. Still
Alloy A319 is extensively used in the automotive industry. In the as-cast condition the alloy lacks the required strength. A solid solution heat treatment (T4) followed by room temperature quenching improves tensile strength. Accordingly, engine castings in T4 condition are used in the manufacture of automobiles. However, A319 alloy is not thermodynamically stable after solid solution. The matrix is supersaturated with Cu, and a precipitation sequence is expected to occur overtime, which leads to dimensional changes. Alternatively, an aging treatment (T7) can activate the precipitation reactions to achieve dimensional stability in castings. In this work, dilatometric measurements were made during a T7 heat treatment in order to establish the extent of dimensional changes, resulting from the precipitation reactions. In addition, high-resolution electron microscopy was used to follow up the precipitation reactions.
2004-03-08
Technical Paper
2004-01-1029
Carlos C. Engler-Pinto, John V. Lasecki, James M. Boileau, John E. Allison
The high temperature fatigue behaviors of three cast aluminum alloys used for cylinder head fabrication - 319, A356 and AS7GU - are compared under isothermal fatigue at room temperature and elevated temperatures. The thermo-mechanical fatigue behavior for both out-of-phase and in-phase loading conditions (100-300°C) has also been investigated. It has been observed that all three of these alloys present a very similar behavior under both isothermal and thermo-mechanical low-cycle fatigue. Under high-cycle fatigue, however, the alloys A356 and AS7GU exhibit superior performance.
2004-03-08
Technical Paper
2004-01-1027
John C. Hebeisen, Bruce M. Cox
Hot Isostatic Pressing (HIP) has been routinely used to densify castings for aerospace and medical applications for over 30 years. While HIP is widely known to improve the toughness and fatigue life of castings through the healing of internal porosity, it has been perceived as too expensive for most cast aluminum alloys for automotive applications. Recent developments suggest that the cost effectiveness of certain special HIP processes should be revisited due to reductions in process cost and improvements in throughput. This paper will evaluate the Densal® II process applied to a front aluminum steering knuckle. Two casting processes representing differing levels of relative cost and quality were evaluated. The first was Alcoa's VRC/PRC process, a metal mold process with bottom fill, evacuation before fill and pressurization after fill. This is considered to be a premium quality, but higher cost casting process that is already qualified for this application.
2004-03-08
Technical Paper
2004-01-1028
Hirotaka Kurita, Hiroshi Yamagata, Hiroki Arai, Tamotsu Nakamura
A monolithic aluminum block using a newly developed Al-20%Si alloy was made by a vacuum die-casting process. The bore surface design was a sleeveless type with uniformly dispersed primary-Si crystals around 20μm. The die-casting technology consists of a highly airtight die with two series of evacuation systems. The vacuum level in the die cavity was determined to be as low as 5kPa. The gas content of the block was found to be as low as 5cc/100g Al, which has enabled T6 heat treatment. The die cavity temperature was carefully controlled to generate a fine dispersion of primary-Si crystals. The engine testing has proved that the bore wall temperature is 30 K lower than that of the aluminum block enclosing a press-fitted cast iron liner. The superior cooling performance has decreased the oil consumption value to one half that of the aluminum block enclosing a cast iron liner.
2004-03-08
Technical Paper
2004-01-1019
Stephen J. Mashl, Matthew M. Diem
The temperature range used for HIP processing of cast aluminum parts is also appropriate for solution heat treatment. Integration of these two processes should decrease processing time, energy consumption, and processing cost. In this study, Al-Si-Mg castings were subjected to a combined HIP and T6 heat treatment. The properties and microstructure of these castings were compared to parts processed using conventional methods. Apparent differences in the oxide concentration provided insight into the effect of oxide inclusions on HIP response. Results indicate that fatigue life is increased using an integrated HIP/heat treat process, however, oxide contamination can negate this improvement.
2004-03-08
Technical Paper
2004-01-1020
Yun Xia, John Cincilla, Ernie Mohley
Abstract Casting defects such as gas porosity, shrinkage, poor-fill and blistering are related to the filling pattern and flow control in Al and Mg die-casting. It is not clearly understood how atomized and turbulent flow affects the filling patterns and hence casting defects. Significant improvements in casting quality could be achieved with a better understanding of the basic morphology of atomized and turbulent flow and their relationships to the Reynolds number and J number. This paper will explore the relationship between atomized and turbulent flow in Al and Mg die castings and the relationship of wakes produced by obstacles in the flow path and casting defects.
2004-03-08
Technical Paper
2004-01-0835
J. Gholipour, M. J. Worswick, D. Oliveira
This paper examines the application of damage models in tube bending and subsequent hydroforming of AlMg3.5Mn aluminum alloy tubes. An in-house Gurson-based damage model, incorporated within LS-DYNA, has been used for the simulations. The applied damage model contains several void nucleation and growth parameters that must be determined for each material. A simpler straight tube hydroforming process was considered first to check the damage parameters and predicted ductility. Then the model was applied to a sequence of bending and hydroforming. The damage history from pre-bending was mapped to the hydroforming stage, to allow prediction of the overall ductility. The applied forming parameters in the simulation were based on data extracted during the experimental tests. Finally, the numerical results were compared to the experimental data.
2004-03-08
Technical Paper
2004-01-1333
Arthur Scafe, Armondo Joaquin
The use of Friction Stir Welding (FSW) is a robust process to use in the assembly of aluminum automotive components. The advantages include: minimal distortion, higher tensile strength, lower costs and improved weld capability than other joining processes. Though a simple process, there are key parameters that must be carefully selected to optimize the weld. This paper will focus on the use of FSW to assemble extrusions into automotive components.
2004-03-08
Technical Paper
2004-01-1328
S. Liu, Y. J. Chao, C. H. Chien
In the friction stir welding (FSW) process, heat is generated by friction between the interfaces between the tool and the workpiece. The amount of heat conducted into the workpiece determines the quality of the weld. In this paper, 37.6 mm (1.48 inch) thick plates made of aluminum alloy 6061-T6 were welded using the FSW process. We report (a) welding parameters such as tool RPM, welding speeds, (b) power and heat input to the welding process, (c) a complete temperature history from 27 thermocouples. Data are reported for one weld with a full-length pin and two welds with a short pin. In conjunction with the measurement, finite element analyses were also performed to study (1) the heat inputs from the tool shoulder as well as from the probe pin, and (2) temperature distribution and history in the workpiece. The analysis results are also compared with the measured data.
2004-03-08
Technical Paper
2004-01-0603
Ulrich Breitmeier
Surface topography characterisation of engine cylinder walls using optical methods such as microscopic stripe projection, white light interferometry (WLI) and micro ellipsometry is outlined. Both the surface topography and also the kind of material can be measured, in especially the Si particle size and location distribution and the overall profile amplitude distribution. In case of an iron coated aluminium matrix a simple method is described to quickly check the equal roughening of the surface and the pore size distribution. The measurement result decides whether rework is necessary before the time consuming and expensive spraying process is performed.
2004-03-08
Technical Paper
2004-01-0745
D. W. Shoon, C. Y. Kang, Kazuya Miyahara, J. H. Sung
The damping capacity and strength of Fe-6Al-25/34Mn alloys have been studied for the development of new materials with high strength and damping capacity. Particularly, the effect of α′(including α) and ε martensite phases, which constitute the microstructure of cold rolled Fe-Al-Mn alloys, has been investigated in terms of the strength and damping capacity of the alloys. The damping capacity rises with increasing the degree of cold rolling and reveals the maximum value at 32% reduction. The damping capacity is strongly affected by the volume fraction of ε martensite, while the other phases, such as α′ and austenite(γ), actually exhibit little effect on damping capacity. Considering that tensile strength increases and elongation decreases with increasing the volume fraction of α′ martensite, it is proved that tensile strength is mainly affected by the amount of α′martensite.
2004-03-08
Technical Paper
2004-01-0742
Zengtao Chen, Michael Worswick, Keith Pilkey, David Lloyd
A so-called damage percolation model is coupled with Gurson-based finite element (FE) approach in order to accommodate the high strain gradients and localized ductile damage. In doing so, void coalescence and final failure are suppressed in Gurson-based FE modeling while a measured second phase particle field is mapped onto the most damaged mesh area so that percolation modeling can be performed to capture ductile fracture in real sheet forming operations. It is revealed that void nucleation within particle clusters dominates ductile fracture in aluminum alloy sheet forming. Coalescence among several particle clusters triggered final failure of materials. A stretch flange forming is simulated with the coupled modeling.
2004-03-08
Technical Paper
2004-01-1612
Peter Furrer, Rod Jones, Beat Ruckstuhl
The specific characteristics of aluminum alloys offer the possibility to design cost-effective lightweight structures with high stiffness and excellent crash energy absorption potential. As a consequence, aluminum is the preferred material to ensure the safety of the vehicle and its occupants fulfilling also related requirements such as pedestrian protection, low repair costs, etc. Applications range from aluminum side impact beams, bumper beams and crash boxes to complete structural modules. Crashworthy aluminum structures are the result of a total systems approach taking into account the benefits achieved by specifically developed alloy qualities, design concepts and appropriate fabrication methods. Cost-efficient aluminum component production processes include in particular the extrusion technology.
2004-03-08
Technical Paper
2004-01-1614
Takayuki Yamada, Yusuke Takayama, Daisei Abe, Tetsu Nishimura
Recently, it was required that the body should be made lightweight. The use of extrusion aluminum elements as the body frame structure is one way of satisfying the requirement. In this research, the cross-section was designed to optimum shape for the maximum crash energy absorption. The energy absorption is performed by the plastic buckling deformation. Therefore, the compressive load and an effective deformation was elucidated from the analytical consideration and experiment. The cross-section which is able to absorb greater crash energy was discussed by considering buckling mechanism, and it was verified by the experiment.
2013-01-09
Technical Paper
2013-26-0080
Bade Simhachalam, C. Lakshmanarao
In this paper, energy absorption behavior of Aluminum Alloy AA 7003 and high strength steel tubes is investigated for automotive crash application both experimentally and numerically. The compression test results are compared with the static analysis results obtained from LS-Dyna Software. Tube thickness is varied in the LS-Dyna Finite Element Simulation Software to understand its effect on energy absorption behavior. The peak loads and energy absorption between experimental results and Numeral simulation are found to be in good agreement. The specific energy absorption between high strength steel and Aluminum Alloy AA 7003 is compared.
2014-04-01
Journal Article
2014-01-1012
Jianghui Mao, Carlos Engler-Pinto, Xuming Su, Scott Kenningley
In this paper, the cyclic deformation behavior of an Al-Si-Cu alloy is studied under strain-controlled thermo-mechanical loading. Tests are carried out at temperatures from 20 °C to 440 °C. The effect of strain rate, hold time at temperature and loading sequence are investigated at each temperature. The results show that temperature has a significant effect on the cyclic deformation of Al-Si-Cu alloys. With increasing temperature, the effect of strain rate and hold time become more significant, while load sequence effects remain negligible within the investigated temperature range. Thus, an elasto-viscoplastic model is required for modeling the alloy's behavior at high temperature. This study provides an insight into the necessary information required for modeling of automotive engine components operating at elevated temperature.
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