Comparative Study of Element Formulation on Simulation of Superplastic Forming

2007 ◽  
Vol 551-552 ◽  
pp. 281-286 ◽  
Author(s):  
X.F. Xu ◽  
L.M. Tang ◽  
G.Q. Tong
Keyword(s):  
Finite Element ◽  
Comparative Study ◽  
Strain Rate ◽  
Rate Control ◽  
Superplastic Forming ◽  
Control Algorithms ◽  
Average Strain ◽  
Pressure Time ◽  
Average Strain Rate ◽  
Forming Characteristics

A comparative study of different element formulations in simulating superplastic forming with the MARC finite element code is performed in the paper. Simulations were accomplished with solid, shell, membrane elements to predict forming characteristics and pressure-time curves. Finite element analysis (FEA) predictions of SPF pressure-time curves were found to be greatly affected by the element type and the strain rate control algorithms. Two strain rate control algorithms were applied in the present study: an algorithm based on limiting the rate of deformation with the average strain rate of all the elements, i.e. the build-in method in MARC, and a second algorithm which limits the rate of deformation based on the average strain rate of the elements with the 20 highest strain rates. The resulting pressure-time curves for each of these formulations were compared with respect to each type of element. Under the guide of the analysis, the die was fabricated and the AA5083 bracket was successfully manufactured. Good agreement was obtained between predicted and measured thickness in the part.

Application of Finite Element Method to the Design of Superplastic Forming Processes

1992 ◽  
Vol 114 (4) ◽  
pp. 452-458 ◽  
Author(s):  
N. Chandra ◽  
S. C. Rama
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Metal Forming ◽  
Superplastic Forming ◽  
Design Tool ◽  
Output Pressure ◽  
Pressure Time ◽  
Forming Characteristics ◽  
Element Method

Finite element method is used as a design tool in the prediction of process parameters for superplastic metal forming processes. The method is used in the design of various plane strain and axisymmetric components. The effect of varying die radii and die friction are studied in the forming characteristics of a simple pan. The cone test used for the mechanical characterization of superplastic materials is simulated. A complex component typically used in the aerospace industry is analyzed and the output pressure-time loading and the resulting thickness distributions are determined.

Evaluation of Fatigue Damage on Operating Plant Components in LWR Water

2004 ◽  
Author(s):  
Makoto Higuchi ◽  
Takashi Hirano ◽  
Katsumi Sakaguchi
Keyword(s):  
Strain Rate ◽  
Fatigue Damage ◽  
Austenitic Stainless Steels ◽  
Strain Range ◽  
Average Strain ◽  
Simple Method ◽  
Detailed Method ◽  
Class 1 ◽  
Average Strain Rate ◽  
Fatigue Life Reduction

The effects of LWR water environments on fatigue life reduction of LWR component materials have been evaluated quantitatively. The environmental correction factor Fen, which is determined by strain rate, temperature and dissolved oxygen content has been proposed for assessing this reduction in the case of carbon, low alloy and austenitic stainless steels. Equations to calculate Fen have been established based on fatigue data derived under constant test conditions but strain rate and temperature in actual transients are usually not constant. A method for calculating Fen under conditions of continuously changing strain rate and temperature was established in this study for use in assessing fatigue damage on actual transients, with due consideration to the effects of LWR water environments. The method should be found applicable to Class 1 vessels. It should be possible to determine the stress cycle and fatigue usage factor in air in accordance with the ASME B&PV Code Section III NB-3200. Fatigue damage in LWR water may be found by linear summation of the products of Fen and partial fatigue usage factor in stress cycles. The method is consisted of simple and detailed methods. The evaluation of Fen must be applied for the strain range in which the strain increases continuously. In the simple method, the entire range of stain increasing is used as one segment and the average strain rate and the highest temperature in it are used for computing Fen. In the detailed method, the strain increasing range should be divided into small segments and average strain rate and highest temperature in it are used for finding Fen and Fens in all segments are subsequently averaged by weighting with strain increment in it. The Fen by this latter procedure was found much less than with the former under a condition of considerable temperature change.

Surface strain accumulation and the seismic moment tensor

1997 ◽  
Vol 87 (5) ◽  
pp. 1345-1353
Author(s):  
J. C. Savage ◽  
R. W. Simpson
Keyword(s):  
Strain Rate ◽  
Accumulation Rate ◽  
Moment Tensor ◽  
Surface Strain ◽  
Seismogenic Zone ◽  
Strain Accumulation ◽  
Average Strain ◽  
Average Strain Rate ◽  
Double Couple ◽  
Scalar Moment

Abstract Although the scalar moment accumulation rate within the seismogenic zone beneath a given area is sometimes deduced from the observed average surface strain accumulation rate over that same area (e.g., Working Group on California Earthquake Probabilities, 1995), the correspondence between the two is very uncertain. The equivalence between surface strain accumulation and scalar moment accumulation is based on Kostrov's (1974) relation between the average strain rate over a volume and the moment-rate tensor for that volume. The average strain rate over the volume is replaced by the average strain rate measured at the free surface to deduce an approximate moment-rate tensor. Only in exceptional circumstances will that moment-rate tensor correspond to a double-couple mechanism, a mechanism that can be represented by a scalar moment accumulation rate. More generally, the moment tensor must be resolved into the superposition of two or more double-couple mechanisms, and that resolution can be done in many ways, each with its own scalar moment rate. Thus the resolution is not unique. This is demonstrated by deducing scalar moment accumulation rates for a GPS network that covers most of California south of San Francisco. It is shown that resolutions into different double-couple mechanisms lead to scalar moment accumulation rates differing by factors of ∼2. We suggest that the minimum scalar moment rate equivalent to principal surface strain rates ɛ1 and ɛ2 acting over the area A is M0(min) = 2μHA Max (¦ɛ1¦, ¦ɛ2¦, ¦ɛ1 + ɛ2¦), where μ is the rigidity and H the depth of seismogenic zone, and the function Max is equal to the largest of its arguments. Within the uncertainites of measurement, the scalar moment accumulation rate in southern California based on that approximation is in balance with the average historic seismic moment release rate so that no current earthquake deficit need be accumulating.

The Influence of Strain Rate on the Passive and Stimulated Engineering Stress–Large Strain Behavior of the Rabbit Tibialis Anterior Muscle

1998 ◽  
Vol 120 (1) ◽  
pp. 126-132 ◽  
Author(s):  
B. S. Myers ◽  
C. T. Woolley ◽  
T. L. Slotter ◽  
W. E. Garrett ◽  
T. M. Best
Keyword(s):  
Strain Rate ◽  
Tibialis Anterior ◽  
High Speed ◽  
Large Strain ◽  
Strain Rates ◽  
Average Strain ◽  
Stress Strain ◽  
Engineering Stress ◽  
Average Strain Rate ◽  
Strain Responses

The passive and stimulated engineering stress–large strain mechanical properties of skeletal muscle were measured at the midbelly of the rabbit tibialis anterior. The purpose of these experiments was to provide previously unavailable constitutive information based on the true geometry of the muscle and to determine the effect of strain rate on these responses. An apparatus including an ultrasound imager, high-speed digital imager, and a servohydraulic linear actuator was used to apply constant velocity deformations to the tibialis anterior of an anesthetized neurovascularly intact rabbit. The average isometric tetanic stress prior to elongation was 0.44 ± 0.15 MPa. During elongation the average stimulated modulus was 0.97 ± 0.34 MPa and was insensitive to rate of loading. The passive stress–strain responses showed a nonlinear stiffening response typical of biologic soft tissue. Both the passive and stimulated stress–strain responses were sensitive to strain rate over the range of strain rates (1 to 25 s−1). Smaller changes in average strain rate (1 to 10, and 10 to 25 s−1) did not produce statistically significant changes in these responses, particularly in the stimulated responses, which were less sensitive to average strain rate than the passive responses. This relative insensitivity to strain rate suggests that pseudoelastic functions generated from an appropriate strain rate test may be suitable for the characterization of the responses of muscle over a narrow range of strain rates, particularly in stimulated muscle.

New Developments in Superplastic Forming Simulation and Industrial Applications

2010 ◽  
Vol 433 ◽  
pp. 211-217 ◽  
Author(s):  
Shun Ping Li ◽  
Mathilde Chabin ◽  
Andrew Heath
Keyword(s):  
Strain Rate ◽  
Rate Control ◽  
Numerical Algorithms ◽  
Shell Element ◽  
Superplastic Forming ◽  
Industrial Applications ◽  
Element Formulation ◽  
Material Models ◽  
New Developments ◽  
Forming Simulation

In this paper, the authors presented the material models and numerical algorithms adopted in PAMSTAMP 2G for superplastic forming simulation. The improvements in strain rate control, automatic stop criteria, velocity scaling and shell element formulation to include normal stress can improve the accuracy and efficiency of superplastic forming simulation.

Finite Element Modeling and Numerical Simulation of Superplastic Forming of 8090 Al-Li Alloy in a Rectangular Die

2012 ◽  
Vol 487 ◽  
pp. 116-121 ◽  
Author(s):  
M. Balasubramanian ◽  
K. Ramanathan ◽  
Ke Zhu
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Strain Rate ◽  
Physical Phenomenon ◽  
Tensile Elongation ◽  
Constant Strain Rate ◽  
Superplastic Forming ◽  
Alloy Sheet ◽  
Low Flow ◽  
Polycrystalline Materials

Superplasticity is a physical phenomenon associated with certain polycrystalline materials which exhibit very high tensile elongation prior to fracture under particular conditions of strain rate and temperature. Aluminium alloy undergoes superplastic elongation in the order of a few thousands percent in elongation with low flow stresses. Superplastic forming processes can provide products with integral structure, light weight and superior strength, all of which are of particular importance for aerospace and automotive components. In the present study an analytical model was developed for a rectangular component by considering constant strain rate. This paper attempts to explore the superplastic behaviors of 8090 Al-Li alloy sheet into a rectangular die using blow forming technique. This has been done by a simple theoretical model and by numerical simulation using standard finite element code ABAQUS. The numerical and analytical results agree reasonably well for both the analytical and theoretical values with regard to variation in pressure and time.

Research on the Mechanical Behavior of Styropor Concrete at High Strain Rates

2010 ◽  
Vol 168-170 ◽  
pp. 2086-2091
Author(s):  
Ze Bin Hu ◽  
Jin Yu Xu ◽  
Jie Zhu ◽  
Qiang He ◽  
Gang Li ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Strain ◽  
Dynamic Strength ◽  
Strain Rates ◽  
Average Strain ◽  
High Strain Rates ◽  
Average Strain Rate ◽  
The Impact

Mechanical behavior of Styropor concrete(EPSC) added with various volumetric fractions of EPS subjected to high strain rates were studied by using the Large-Diameter-SHPB. The infection of volumetric fractions and average strain rate to dynamic properties of EPSC were investigated. The experimental results show that under high strain rate condition, the dynamic strength, dynamic strength increase factor(DIF) and limit strain of EPSC are strain rate dependent, the strain rate effect can be expressed by linear approximations, and the relationship between elastic modulus and average strain rate is independent.With the addition of volumetric fractions of EPS, the impact compressive strength and elastic modulus of EPSC declines, and the toughness of EPSC is reinforced.

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