Interfacial Residual Stress Measurement of SiC/Epoxy Composites by Microphotoelastic Method

2006 ◽  
Vol 326-328 ◽  
pp. 273-276
Author(s):  
Xin Wei Yang ◽  
Xin Hua Ji ◽  
Yong Ming Xing ◽  
Yu Wen Qin
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Fem Analysis ◽  
Epoxy Composites ◽  
Residual Stress Field ◽  
Finite Element Software ◽  
Novel Technique ◽  
The Difference

Interfacial residual stresses play an important role in the mechanical properties. In this paper, the interfacial residual stresses of SCI/Epoxy composites were determined using a novel technique-microphotoelastic method. The thermal residual stress field was also numerically simulated using a finite element software MSC.MARC. The difference and the similarities between the experimental results and the simulation of FEM analysis were discussed and the availability of the method was preliminarily certified.

scholarly journals Effect of Residual Stress on the Mechanical Properties of FSW Joints with SUS409L

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Yeong-Seok Lim ◽  
Sang-Hyuk Kim ◽  
Kwang-Jin Lee
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Stress Measurement ◽  
Charpy Impact ◽  
Stir Zone ◽  
Hole Drilling ◽  
Friction Stir ◽  
Compressive Residual Stresses

This study was performed to investigate both the residual stress distribution and the effect of the residual stress formed at the welding region on the mechanical properties of the friction stir welded joints with 409L stainless steel sheets. Residual stress measurement with hole-drilling method; mechanical property evaluation including tensile test, Charpy impact test, and fatigue test; and microstructure observation were conducted. It has got no residual stresses to speak of at the center region of the stir zone because the stored stresses are released in the process of the dynamic recrystallization, while a small quantity of compressive residual stresses is formed at the surface region of the stir zone because of strong compression reaction by the tool shoulder. A considerable amount of compressive residual stresses is formed at the thermomechanical affected zone because of the synergy between the thermal expansion due to the heat conduction from the stir zone and mechanical compression by the tool. The formation of residual stresses shows a similar tendency between the advancing side and the retreating side. Both the mitigation of residual stress in the stir zone and the formation of compressive residual stress in the thermomechanical affected zone contribute to the improvement of the mechanical properties of the friction stir welded joints.

scholarly journals Experimental Measurement of Residual Stress Distribution in Rail Specimens Using Ultrasonic LCR Waves

2021 ◽  
Vol 11 (19) ◽  
pp. 9306
Author(s):  
Young-In Hwang ◽  
Geonwoo Kim ◽  
Yong-Il Kim ◽  
Jeong-Hak Park ◽  
Man-Yong Choi ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Residual Stress Distribution ◽  
Material Surface ◽  
Arrival Times ◽  
Effective Depth ◽  
The Difference ◽  
The Relationship

Longitudinal critically refracted (LCR) waves are considered bulk longitudinal waves and penetrate into an effective depth beneath the surface parallel to the material surface. Such LCR waves can be employed to measure residual stresses because the acoustoelastic effect is the basis for ultrasonic residual stress measurements. This effect is described by the relationship between change of wave travel time and stress applied when such waves propagate in a stressed medium. In this paper, stresses applied in a rail were evaluated by using a developed LCR probe. With this transducer, it was verified how the difference in the arrival times of the LCR waves showed a trend as the tensile stresses increased. The acoustoelastic coefficients were calculated using the relationship between the stresses and the travel times, and the residual stresses of the used rails were measured using these coefficients. In addition, the difference in residual stress distribution according to the characteristics of the wheel-rail contact surface was analyzed from the obtained residual stress value. It was concluded that this non-destructive evaluation technique using LCR waves could be employed for accurate stress measurement of rails because differences in stress applied to the rail can be detected.

Slitting and Contour Method Residual Stress Measurements in an Edge Welded Beam

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Foroogh Hosseinzadeh ◽  
Muhammed Burak Toparli ◽  
Peter John Bouchard
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Stress Measurement ◽  
Welding Process ◽  
Pressure Vessels ◽  
Contour Method ◽  
Residual Stress Field ◽  
Integrity Assessment ◽  
Stress Measurements

Welding is known to introduce complex three-dimensional residual stresses of substantial magnitude into pressure vessels and pipe-work. For safety-critical components, where welded joints are not stress-relieved, it can be of vital importance to quantify the residual stress field with high certainty in order to perform a reliable structural integrity assessment. Finite element modeling approaches are being increasingly employed by engineers to predict welding residual stresses. However, such predictions are challenging owing to the innate complexity of the welding process (Hurrell et al., Development of Weld Modelling Guidelines in the UK, Proceedings of the ASME Pressure Vessels and Piping Conference, Prague, Czech Republic, July 26–30, 2009, pp. 481–489). The idea of creating weld residual stress benchmarks against which the performance of weld modeling procedures and practitioners can be evaluated is gaining increasing acceptance. A stainless steel beam 50 mm deep by 10 mm wide, autogenously welded along the 10 mm edge, is a candidate residual stress simulation benchmark specimen that has been studied analytically and for which neutron and synchrotron diffraction residual stress measurements are available. The current research was initiated to provide additional experimental residual stress data for the edge-welded beam by applying, in tandem, the slitting and contour residual stress measurement methods. The contour and slitting results were found to be in excellent agreement with each other and correlated closely with published neutron and synchrotron residual stress measurements when differences in gauge volume and shape were accounted for.

Slitting and Contour Method Residual Stress Measurements in an Edge Welded Beam

2010 ◽  
Author(s):  
Foroogh Hosseinzadeh ◽  
P. John Bouchard ◽  
M. Burak Toparli
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Structural Integrity ◽  
Stress Measurement ◽  
Welding Process ◽  
Pressure Vessels ◽  
Contour Method ◽  
Residual Stress Field ◽  
Integrity Assessment ◽  
Stress Measurements

Welding is known to introduce complex three-dimensional residual stresses of substantial magnitude into pressure vessels and pipe-work. For safety-critical components, where welded joints are not stress-relieved, it can be of vital importance to quantify the residual stress field with high certainty in order to perform a reliable structural integrity assessment. Finite element modeling approaches are being increasingly employed by engineers to predict welding residual stresses. However, such predictions are challenging owing to the innate complexity of the welding process [1]. The idea of creating weld residual stress benchmarks against which the performance of weld modeling procedures and practitioners can be evaluated is gaining increasing acceptance. A stainless steel beam 50 mm deep by 10 mm wide, autogenously welded along the 10 mm edge, is a candidate residual stress simulation benchmark specimen that has been studied analytically and for which neutron and synchrotron diffraction residual stress measurements are available. The current research was initiated to provide additional experimental residual stress data for the edge-welded beam by applying, in tandem, the slitting and contour residual stress measurement methods. The contour and slitting results were found to be in excellent agreement with each other and correlated closely with published neutron and synchrotron residual stress measurements when differences in gauge volume and shape were accounted for.

Improving the mechanical properties and reducing the residual stresses of AA7075 by combination of cyclic close die forging and precipitation hardening

2020 ◽  
pp. 146442072097242
Author(s):  
MA Moazam ◽  
M Honarpisheh
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Aluminum Alloys ◽  
Tensile Stress ◽  
Residual Stresses ◽  
Precipitation Hardening ◽  
Stress Measurement ◽  
Uniaxial Tensile ◽  
Die Forging ◽  
Aa 7075

As one of the major strengthening mechanisms, the precipitation hardening is used to enhance the mechanical properties of aluminum alloys. Based on the results of the residual stress measurement, after fast quenching, the core of the material is under tensile stress while the surfaces are under compressive residual stress. Distortion commonly happens during the machining of precipitation-hardened aluminum alloys due to the residual stresses created during the quenching step in the heat treatment process. In this study, the combination of cyclic close die forging and precipitation hardening was used to improve the mechanical properties and control the residual stresses of AA 7075, simultaneously. According to the results, a considerable level of residual stresses was developed in the sample after the quenching step. Performing the cyclic close die forging process immediately after the quenching step changed the pattern of the residual stresses and reduced them significantly. The reduction of the residual stresses after the first pass of cyclic close die forging was about 50%, while after two passes, the sample was almost fully stress relieved. Besides, the results of the microhardness and uniaxial tensile tests demonstrated the improvement of the mechanical properties of the processed samples when compared to the T6 condition. Also, in comparison to AA 7075-T6, the yield stress, ultimate tensile stress, and microhardness were increased by about 24%, 22%, and 48%, respectively.

Residual Stress Measurement Simulation in a Type 316 Stainless Steel Girth-Butt Weld Joint

2008 ◽  
Author(s):  
S. Hossain ◽  
C. E. Truman ◽  
D. J. Smith ◽  
K. Ogawa
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Stress Field ◽  
Residual Stresses ◽  
Weld Joint ◽  
Stress Measurement ◽  
Measurement Procedure ◽  
Residual Stress Measurement ◽  
Residual Stress Field ◽  
Butt Weld

Several techniques exist to measure residual stresses, but most only work close to the surface of a component. The deep-hole drilling (DHD) method [1] provides complete, through-thickness, measurements of residual stress with high spatial resolution which can be used to validate numerical models. In common with all mechanical strain release methods of residual stress measurement, extra care must be taken when making measurements on components containing highly triaxial residual stress fields which are close to yield. This is because the introduction of a free surface, created as part of the measurement procedure, can lead to plastic redistribution of the residual stress field which is not accounted for in the elastic inversion algorithms of the experimental procedure. This paper seeks to demonstrate the usefulness and accuracy of the DHD method in a component predicted to contain a triaxial residual stress field by comparing measurements and the results of a DHD simulation on a type 316 stainless steel pipe with girth-butt weld joint. Step 1, results are presented from three-dimensional finite element (FE) simulations of the original girth weld. Step 2, the residual stresses predicted from these simulations are mapped onto a new mesh, designed in order to permit a simulation of the DHD measurement method detailed above. Step 3, an FE simulation of the DHD procedure was undertaken, and the predictions of the radial distortion of the initial reference hole were used in the usual experimental inversion algorithm. This permitted a simulation of the DHD measured residual stresses to be obtained and compared with the predictions of the initial FE model. The effects of different material models as well as the measurement paths were also considered. Finally, step 4, FE predicted residual stresses, DHD simulated residual stresses and actual DHD measured residual stresses were compared and conclusions concerning the accuracy of the DHD measurement procedure were made.

Assessment of the Influence of Plasticity and Constraint on Measured Residual Stresses Using the Contour Method

2008 ◽  
Author(s):  
R. J. Dennis ◽  
D. P. Bray ◽  
N. A. Leggatt ◽  
M. Turski
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Measurement ◽  
General Procedure ◽  
Relaxation Method ◽  
Cutting Process ◽  
Contour Method ◽  
Hole Drilling ◽  
Residual Stress Field ◽  
Rigid Constraint

The contour method is a relatively new relaxation method for residual stress measurement and may be seen as an evolution of established methods such as hole drilling. The general procedure when applying the contour method is cutting, measurement and calculation of residual stress normal to the cut plane using Bueckner’s principle of elastic superposition. That is the residual stresses are determined from the measured profile of a cut surface. While the contour method is simple in concept there are certain underlying issues relating to the cutting process that may lead to uncertainties in the measured results. Principally the issues are that of constraint and plasticity during cutting and the influence they have on the measured residual stresses. In this paper both issues are investigated in detail by simulating the entire contour method process using finite element techniques for two welded specimens. Constraint has been a recognised concern for the contour method with the general requirement being to hold the specimen as rigidly as possible. Both clamping and fixing bolts are routinely used however in reality these methods do not provide a fully rigid constraint. In this work a range of constraints have been examined to determine the influence on the measured residual stresses. Plasticity, as a consequence of the cutting process, has also been recognised as a factor which may affect the measured residual stresses. In this work the extent of plasticity is predicted by simulation of the cutting process. With a known initial residual stress field the effects of plasticity are directly quantifiable. This work therefore provides an extremely useful insight into some of the key issues that affect the measurement performance of the contour method.

Finite Element Validation of the over-Coring Deep-Hole Drilling Technique

2011 ◽  
Vol 70 ◽  
pp. 291-296 ◽  
Author(s):  
Sayeed Hossain ◽  
Ed J. Kingston ◽  
Christopher E. Truman ◽  
David John Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Stress Measurement ◽  
Residual Stress Measurement ◽  
Hole Drilling ◽  
Deep Hole ◽  
Residual Stress Field ◽  
Deep Hole Drilling

The main objective of the present study is to validate a simple over-coring deep-hole drilling (oDHD) residual stress measurement technique by utilising finite element simulations of the technique. A number of three dimensional (3D) finite element analyses (FEA) were carried out to explore the influence of material removal and the cutting sequence during the deep-hole drilling (DHD) residual stress measurement process on the initial residual stress field. Two models were considered in the study. First, the residual stress field predicted in a rapid spray water quenched solid cylinder was used as the initial stress field for the DHD FE model. The DHD reconstructed residual stresses were compared with the initial FE predicted stresses. Different cutting sequences and different dimensions were systematically simulated before arriving at an optimum solution for the oDHD technique. The oDHD technique significantly improved the spatial resolution and was applied in a second model consisting of a 40mm thick butt-welded pipe. The DHD reconstructed residual stresses compared very well with the initial FE predicted weld residual stress thereby validating the oDHD technique.

Monitoring of mechanical properties of prestressed glass fiber epoxy composites over 12 months after fabrication

2021 ◽  
pp. 002199832110047
Author(s):  
Mahmoud Mohamed ◽  
Siddhartha Brahma ◽  
Haibin Ning ◽  
Selvum Pillay
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Flexural Strength ◽  
Compressive Residual Stress ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Epoxy Composites ◽  
Flexural Properties ◽  
Initial Increase ◽  
Fiber Volume

Fiber prestressing during matrix curing can significantly improve the mechanical properties of fiber-reinforced polymer composites. One primary reason behind this improvement is the generated compressive residual stress within the cured matrix, which impedes cracks initiation and propagation. However, the prestressing force might diminish progressively with time due to the creep of the compressed matrix and the relaxation of the tensioned fiber. As a result, the initial compressive residual stress and the acquired improvement in mechanical properties are prone to decline over time. Therefore, it is necessary to evaluate the mechanical properties of the prestressed composites as time proceeds. This study monitors the change in the tensile and flexural properties of unidirectional prestressed glass fiber reinforced epoxy composites over a period of 12 months after manufacturing. The composites were prepared using three different fiber volume fractions 25%, 30%, and 40%. The results of mechanical testing showed that the prestressed composites acquired an initial increase up to 29% in the tensile properties and up to 32% in the flexural properties compared to the non-prestressed counterparts. Throughout the 12 months of study, the initial increase in both tensile and flexural strength showed a progressive reduction. The loss ratio of the initial increase was observed to be inversely proportional to the fiber volume fraction. For the prestressed composites fabricated with 25%, 30%, and 40% fiber volume fraction, the initial increase in tensile and flexural strength dropped by 29%, 25%, and 17%, respectively and by 34%, 26%, and 21%, respectively at the end of the study. Approximately 50% of the total loss took place over the first month after the manufacture, while after the sixth month, the reduction in mechanical properties became insignificant. Tensile modulus started to show a very slight reduction after the fourth/sixth month, while the flexural modulus reduction was observed from the beginning. Although the prestressed composites displayed time-dependent losses, their long-term mechanical properties still outperformed the non-prestressed counterparts.

scholarly journals Residual stresses in thermite welded rails: significance of additional forging

2020 ◽  
Vol 64 (7) ◽  
pp. 1195-1212
Author(s):  
B. Lennart Josefson ◽  
R. Bisschop ◽  
M. Messaadi ◽  
J. Hantusch
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Weld Metal ◽  
Welding Process ◽  
Surface Zone ◽  
Fe Model ◽  
Uneven Surface ◽  
Residual Stress Field ◽  
High Dynamic

Abstract The aluminothermic welding (ATW) process is the most commonly used welding process for welding rails (track) in the field. The large amount of weld metal added in the ATW process may result in a wide uneven surface zone on the rail head, which may, in rare cases, lead to irregularities in wear and plastic deformation due to high dynamic wheel-rail forces as wheels pass. The present paper studies the introduction of additional forging to the ATW process, intended to reduce the width of the zone affected by the heat input, while not creating a more detrimental residual stress field. Simulations using a novel thermo-mechanical FE model of the ATW process show that addition of a forging pressure leads to a somewhat smaller width of the zone affected by heat. This is also found in a metallurgical examination, showing that this zone (weld metal and heat-affected zone) is fully pearlitic. Only marginal differences are found in the residual stress field when additional forging is applied. In both cases, large tensile residual stresses are found in the rail web at the weld. Additional forging may increase the risk of hot cracking due to an increase in plastic strains within the welded area.

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