Problems in creep testing under biaxial stress systems

1976 ◽  
Vol 11 (1) ◽  
pp. 1-6 ◽  
Author(s):  
D A Kelly
Keyword(s):  
Microscopic Examination ◽  
Biaxial Tension ◽  
Axial Stress ◽  
Testing Machine ◽  
Biaxial Stress ◽  
The Other ◽  
Creep Testing ◽  
Creep Failure ◽  
Axial Tension

Two types of creep testing machine, one to apply bi-axial tension to cruciform specimens and the other, torsion to disc-shaped specimens, have been constructed in the course of an investigaton of the behaviour of copper subject to multi-axial stress systems. Problems of bending in biaxial tension and buckling in torsion were encountered subsequent to construction of the machines. In the former case the deficiency was accepted and eccentric loading used to control the bending within acceptable limits. In the latter case microscopic examination was found necessary in order to define creep failure.

Understanding the Differences in Hemispherical Dome and Biaxial Test During Equi-Biaxial Tension on Cruciform

2016 ◽  
Author(s):  
Chetan P. Nikhare ◽  
Emmett Vorisek ◽  
John Nolan ◽  
John T. Roth
Keyword(s):  
Sheet Metal ◽  
Test Data ◽  
Biaxial Tension ◽  
Testing Machine ◽  
Biaxial Stress ◽  
Dome Height ◽  
Bulge Test ◽  
Biaxial Test ◽  
Hemispherical Dome ◽  
Biaxial Tests

One metal manufacturing process which uses thousands of processes to trim, stretch, draw, bend etc. under a big umbrella is sheet metal forming. Using heavy equipment, the sheet metal parts are deformed into complex geometries. The complexity in these parts produces multi-axial stress and strain, a state for which it is critical to analyze using conventional tools. Traditionally, the mechanical properties of materials have been characterized using the uniaxial tension test. This test is considered adequate for simple forming operations where single axis loading is dominant. Previous studies, however, have noted that the data acquired from this type of testing is not enough and additional details in other axes under simultaneous deformation conditions are important. To analyze the biaxial strain, some studies have suggested using the limiting dome height test and bulge test. However, these tests limit the extent of using multi-axial loading and the resulting stress pattern due to contact surfaces. Therefore, researchers devised the biaxial machine which is designed specifically to provide biaxial stress components using multiple and varying loading conditions. The idea of this work is to evaluate the relationship between the dome test data and the biaxial test data. For this comparison, cruciform specimens with a diamond shaped thinner gage in the center were deformed with biaxial stretching on the biaxial testing machine. In addition, the cruciform specimens were bi-axially stretched with a hemispherical punch in a conventional die-punch setting. Furthermore, in each case, the process was simulated using a 3D model generated on ABAQUS. These models were then compared with the experimental results. The forces on each arm, strain path, forming and formability was analyzed. The differences between the processes were detailed. It was found that biaxial tests eliminated the pressurization effect which could be found in hemispherical dome tests.

scholarly journals TOPOLOGICAL OPTIMIZATION OF THE TEST SPECIMEN FOR BIAXIAL TENSION

2019 ◽  
Vol 81 (1) ◽  
pp. 103-117
Author(s):  
A. V. Zhidkov ◽  
V. G. Kiselev ◽  
A. K. Lyubimov ◽  
O. A. Sergeev ◽  
A. V. Basalin
Keyword(s):  
Test Specimen ◽  
Biaxial Tension ◽  
Testing Machine ◽  
Finite Element Approximation ◽  
Plane Stress State ◽  
Biaxial Stress ◽  
Topological Optimization ◽  
Element Approximation ◽  
Measuring Devices ◽  
Design Variables

Applying the approaches of topology optimization, we consider the problem of substantiation of the configuration of the 2D test specimen, in the workspace of which the biaxial stress-strain state is realized. The original area occupied by the specimen is a square plate with a given side size made of an isotropic material. At the boundaries of the region, segments of fixed length are established on which boundary conditions are specified. The length of the segments is determined by the dimensions of the grippers of the testing machine. In the central part of the specimen is located the working area of the square form where the definition of displacements is carried out using measuring devices. The dimensions of the working area are selected taking into account the region of the used measuring devices. The test specimen is considered as a complex system consisting of working and auxiliary parts interacting with each other. The latter ensures the transfer of forces from the testing machine to the working part. The basic criterion determining the performance of this system is the criterion of accuracy of determining the deformations (displacements) in the working part. The implementation of the criterion is possible by ensuring the necessary stiffness of the overall system, i.e. the system's ability to carry the effect of external loads with allowable deformations that do not violate the performance of the system. The specimen design scheme for biaxial stretching used in the topological optimization process is reduced to the scheme of a two-dimensional plate of variable thickness which is in a plane stress state and occupies the initial region. The original search field is replaced by its finite element approximation. The objective function to be maximized is the stiffness of the system, and the design variables are the thicknesses of 2D finite elements. The specimen volume is set. A technique is proposed that allows determining the distribution of the material ensuring the achievement of the maximum integral stiffness of the system. The analysis of results of numerical simulation using the technique showed the need for holes on the specimen sleeves used in the experiments.

About the effect of resection of the deferent duct on the tone of the sphincter of the urinary bladder

1903 ◽  
Vol 3 (3-4) ◽  
pp. 154-155
Author(s):  
M. A. Vasiliev
Keyword(s):  
Urinary Tract ◽  
Urinary Bladder ◽  
Clinical Significance ◽  
Microscopic Examination ◽  
Rapid Onset ◽  
The Other ◽  
Negative Data ◽  
Deferent Duct ◽  
The One

Beneficial influence is so-called. sexual operations in persons with hypertrophy of prostatae was explained by the advancing atrophy of the last days. But the rapid onset of the result, on the one hand, and the negative data of the microscopic examination of the prostate after the operation, on the other, showed that the atrophy of the prostate was not very good here. In addition to the explanation of this fact, they put a decrease in the congestion of the urinary tract, which was considered an ethological moment for hypertrophy of the prostatae. smyavinoschago duct) on the tone of the sphincteris vesicae, in order to find out in this way partly the clinical significance of these operations.

Anisotropic Loading Functions for Combined Stresses in the Plastic Range

1955 ◽  
Vol 22 (1) ◽  
pp. 77-85
Author(s):  
L. W. Hu ◽  
Joseph Marin
Keyword(s):  
Plastic Flow ◽  
Biaxial Tension ◽  
Strain History ◽  
Test Results ◽  
Axial Tension ◽  
State Of Stress ◽  
Loading Function ◽  
Combined Stresses ◽  
Shift Of Origin ◽  
Tubular Specimens

Abstract A loading function is a relation between combined stresses for which the beginning of plastic flow takes place. The loading function for a given material is different depending upon the initial plastic strains produced. That is, the initial stress or strain history influences the subsequent loading function. This paper gives the results of an experimental investigation to determine the validity of certain loading functions proposed for anisotropic materials. The study reported was conducted for an aluminum alloy 24S-T and the state of stress covered was biaxial tension. These stresses were produced in the usual way by subjecting thin-walled tubular specimens to axial tension and internal pressure. The test results showed that none of the existing loading functions is adequate for interpreting the plastic stress-strain relations obtained. Tests also were made to determine the change in the loading function with increase in plastic flow. It was found that the loading function did not remain symmetrical with respect to the original function, nor was the new loading function the same as the original except for a shift of origin. However, the test results support in a qualitative way the concept of the so-called “yield corner.”

Numerical Stress Analysis of the Biaxial Tension-Compression Wedge-Splitting Test in Vicinity of the Crack Tip

2018 ◽  
Vol 784 ◽  
pp. 85-90
Author(s):  
Stanislav Seitl ◽  
Petr Miarka ◽  
Ildikó Merta ◽  
Zbyněk Keršner
Keyword(s):  
Stress Analysis ◽  
Mechanical Test ◽  
Biaxial Tension ◽  
Crack Tip ◽  
Biaxial Stress ◽  
Stress Fields ◽  
Wedge Splitting Test ◽  
Splitting Test ◽  
Compression Wedge ◽  
Wedge Splitting

Wedge-splitting test is widely used fracture mechanical test for its stability in measurement during the testing and many papers were published. However, the biaxial wedge-splitting test is relatively a new method and the numerical stress analysis of such test is necessary. Especially the investigation of the stress fields in the vicinity of the crack tip. In this contribution, influence of various biaxial stress level is discussed on values of first and second terms of William’s expansion.

Biaxial Strength of HY 80 Steel

1985 ◽  
Vol 107 (2) ◽  
pp. 132-137 ◽  
Author(s):  
K. S. Chan ◽  
U. S. Lindholm ◽  
J. Wise
Keyword(s):  
Biaxial Tension ◽  
Strain Ratio ◽  
Thin Wall ◽  
Plastic Strain Ratio ◽  
Axial Tension ◽  
Diffuse Necking ◽  
Stress States ◽  
Von Mises ◽  
Tube Geometry ◽  
Good Agreement

The biaxial deformation behavior of HY 80 steel has been examined by testing thin wall tubes under combined axial tension and internal pressure. The effective stress-strain curves and the hardening response have been found to vary with the stress state. The plastic strain ratio at a given stress ratio deviates from the von Mises value except at the stress states near uniaxial tension, plane strain and equi-biaxial tension. Using Drucker theory, these deviations are eliminated and the resulting yield locus is in good agreement with both the Bishop-Hill theory and the experimental results. Influenced by the tube geometry, the instability strains at the onset of diffuse necking are decreased by an increase in hoop tension. The diffuse necking strains are reasonably predicted by the Swift and the Lankford-Saibel/Mellor criteria.

scholarly journals Effect Of Accelerating Aging On Retention And The Release Period Of Clips In A Bar Retained Maxillary Implant Overdenture

2021 ◽  
Vol 8 ◽  
Author(s):  
Dalia El naggar ◽  
Ahmed Mohamed Alam-Eldein ◽  
Maha Mostafa Halim ◽  
Hoda Mohammed Amin Rashad
Keyword(s):  
Testing Machine ◽  
Accelerated Aging ◽  
The Other ◽  
Universal Testing Machine ◽  
Universal Testing ◽  
Retention Loss ◽  
Significant Difference ◽  
Implant Overdenture

Objectives: This study was made to detect the effect of accelerating aging on retention and measuring the release period of clips in a 2 and 3 bar retained maxillary implant overdenture. Materials and Methods: Four implants were placed in two maxillary edentulous epoxy models. One model had two bar attachments with two clips overdenture while the other model had three bar attachments with three clips in the overdenture. Retention and release period of the clips were checked before applying insertion removal cycles. Retention was measured using universal testing machine after 540 cycles (6 months) and 1080 cycles (1 year) of insertion removal on a chewing simulator.Results and Conclusions: There was a significant difference in retention and release period between two bars and three bars implant retained maxillary overdentures. A significant difference was also seen in each group after accelerated aging. Therefore, the three bar implant retained overdenture had higher retention values than two bar. Retention loss occurred in both groups after the insertion removal cycles. Release period value was lower in two bar overdenture than three bar overdenture.

Densification Behavior in Forming of Stir Casted Aluminium Boron Carbide Composite Perform during Cold Upsetting

2014 ◽  
Vol 592-594 ◽  
pp. 117-121
Author(s):  
K.R. Thangadurai ◽  
A. Asha
Keyword(s):  
Boron Carbide ◽  
Hydrostatic Stress ◽  
Axial Stress ◽  
Testing Machine ◽  
Strain Curve ◽  
High Hardness ◽  
Casting Process ◽  
Cold Upsetting ◽  
Sem Images ◽  
Upsetting Test

The forming behavior of AA6061 boron carbide composites produced by stir casting process was investigated with the cold upsetting test. The composites containing 0%, 5%, 10% and 15% of B4Cp reinforcements were investigated with the cold upsetting test in Universal Testing Machine under tri-axial stress state condition. SEM images were taken to identify the presence of B4Cp particle in aluminium matrix. From the analysis, it was found that the hardness of composite was increased due to increasing amount of boron carbide particle in the composite and the density was decreased due to the lower value of density of boron carbide. The maximum true axial stress, true hoop stress and hydrostatic stress were gradually increased in the event of increasing order of B4Cp in the composites. Finally, it was found that in the stress – strain curve, the boron carbide was the main factor in improving the compressive strength of composites because of its high hardness.

scholarly journals Effect of Combined Stress on Yield and Fracture Behavior of Zircaloy-2

1961 ◽  
Vol 83 (4) ◽  
pp. 499-508 ◽  
Author(s):  
R. L. Mehan
Keyword(s):  
Plastic Flow ◽  
Biaxial Tension ◽  
Effective Strain ◽  
Tension Stress ◽  
Combined Stress ◽  
Flow Properties ◽  
Axial Tension ◽  
Fracture Ductility ◽  
Stress States ◽  
Single Stress

The yielding and fracture characteristics of Zircaloy-2 as a function of stress state were investigated at room temperature through the medium of thin-walled cylindrical specimens under internal pressure and axial tension. Stress states from uniaxial longitudinal tension to uniaxial tangential tension were examined. Two tests at elevated temperature were performed at a single stress ratio. It was found that the fracture ductility lessened with increasing biaxiality. A minimum in ductility was found at balanced biaxial tension where the fracture ductility, as expressed by the effective strain, was 29 per cent. The yielding and plastic flow properties were found to be highly anisotropic. Two methods were used to express the plastic flow data: a graphical approach and a theoretical analysis based on a theory proposed by R. Hill, either one of which is suitable to express the flow properties of Zircaloy-2 under various states of combined stress.

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