• Journal of Welding and Joining
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• v.5 no.1
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• pp.42-56
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• 1987

Fatigue Fracture behaviors of the TIG-welded aluminum alloys, such as Al 2024-T4, A1 5050-0 and Al 7075-T7 were investigated when a crack propagated from tensile residual stress region and compressive residual stress region. The experimental values were compared with the values expected by the Forman equation. The experimental results are summarized as the following: (1) In case of fatigue crack propagation from residual stress region, the values predicted by Forman equation were Found to exactly corresponded to the experimental values. (2) When the stress intensityfactors affected by compressive residual stress, Kres, were greater than the stress intensity factors by minimum applied stresses. Kmin, the Forman equation was found to be improper to be applied directly, but the equation appeared to be proper, if the stress ratio was modified to zero. (3) The experimental results confirmed that residual stress was relaxed by repeated tensile loading and the relaxing trend was greater in case of compressive residual stress than that of tensile residual stress.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.203-209
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• 2018

Reliable estimation of compressive as well as tensile in-situ stresses is critical in the design and analysis of underground structures and openings in rocks. Kaiser effect technique, which uses acoustic emission from rock specimens under cyclic load, is well established for the estimation of in-situ compressive stresses. This paper investigates the Kaiser effect on marble specimens under cyclic uniaxial compressive as well as cyclic uniaxial tensile conditions. The tensile behavior was studied by means of Brazilian tests. Each specimen was tested by applying the load in four loading cycles having magnitudes of 40%, 60%, 80% and 100% of the peak stress. The experimental results confirm the presence of Kaiser effect in marble specimens under both compressive and tensile loading conditions. Kaiser effect was found to be more dominant in the first two loading cycles and started disappearing as the applied stress approached the peak stress, where felicity effect became dominant instead. This behavior was observed to be consistent under both compressive and tensile loading conditions and can be applied for the estimation of in-situ rock stresses as a function of peak rock stress. At a micromechanical level, Kaiser effect is evident when the pre-existing stress is smaller than the crack damage stress and ambiguous when pre-existing stress exceeds the crack damage stress. Upon reaching the crack damage stress, the cracks begin to propagate and coalesce in an unstable manner. Hence acoustic emission observations through Kaiser effect analysis can help to estimate the crack damage stresses reliably thereby improving the efficiency of design parameters.

• The korean journal of orthodontics
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• v.32 no.5 s.94
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• pp.343-353
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• 2002

This study was designed to investigate the stress distribution of alveolar bone in case of on masse retraction with lingual K-loop archwire using the 3-dimensional photoelastic stress analysis followed by stress freezing process. Lingual K-loop archwire which had loop in 15mm height was used and activated by retraction force of 350gm per each side. The results were as follows 1. Central incisor : As the closer side to crown, the larger tensile stress was distributed at both mesial and labial surfaces and the larger compressive stress was distributed at distal surface. As the closer side to root apex, the larger compressive stress was distributed at lingual surface. The compressive stress was distributed at root apex. 2. Lateral incisor : The tensile stress was distributed at the coronal side of mesial surface. The compressive stress was distributed at distal surface. As the closer side to crown, the larger tensile stress was distributed at labial surface. The tensile stress was distributed at coronal side and the compressive stress was distributed at apical side of lingual surface. The compressive stress was distributed at root apex. 3. Canine The tensile stress was distributed at coronal side and the compressive stress was distributed at apical side of mesial surface. The tensile stress was distributed at distal surface. As the closer side to crown, the larger tensile stress was distributed at both mesial and distal surfaces. The compressive stress was distributed at root apex. 4. Second premolar : The tensile stress was distributed at mesial surface. The compressive stress was distributed at coronal side and the tensile stress was distributed at apical side of distal surface. The compressive stress was distributed at coronal side of buccal surface. As the closer side to crown, the larger tensile stress was distributed at lingual surface. The compressive stress was distributed at root apex. 5. First molar . As the closer side to crown, the larger tensile stress was distributed at both mesial and distal surfaces. No stress was distributed at buccal surface and palatal root apex. As the closer side to crown, the larger tensile stress was distributed at both lingual surfaces. The compressive stress was distributed a4 buccal root apexes. 6. Second molar The compressive stress was distributed at all root apexes. As the closer side to crown, the larger compressive stress was distributed at both mesial and lingual surfaces, and the larger tensile stress at both distal and buccal surfaces. Transverse bowing effect was observed in on-masse retraction with lingual K-loop archwire, however vertical towing effect was not. Rather, reverse vortical bowing effect was developed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.458-466
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• 2020

The purpose of this experimental research is to evaluate the compressive and tensile behaviors of high performance hybrid fiber reinforced concrete(HPHFRC) using amorphous steel fiber(ASF) and polyamide fiber(PAF). For this purpose, the HPHFRCs using ASF and PAF were made according to their total volume fraction of 1.0% for target compressive strength of 40MPa and 60MPa, respectively. And then the compressive and tensile behaviors such as the compressive strength, compressive toughness, direct tensile strength, and stress-strain characteristics under compressive and tensile tests were estimated. It was observed from the test results that the compressive strength of HPHFRC was slightly decreased than that of plain concrete, but the compressive toughness, compressive toughness ratio, and direct tensile strength of HPHFRC increased significantly. Also, it was revealed that the plain concrete showed brittle fracture after the maximum stress from the stress-strain curves, but HPHFRC showed strain softening.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.8-13
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• 2004

The purpose of this paper is to investigate the welding residual stress distribution according to the constraint or non-constraint welding condition with titanium commonly using power station, aircraft, and ship. The measuring method of the residual stress was applied stress release rating method with strain gages and a potable strain meter. The x direction residual stress generally showed the tensile residual stress in case of res03int welding. On the other hand, the x direction residual stress under non-restraint welding were changed tensile stress into compressive stress on 15mm away from welding bead center. Also, the y direction residual stress generally showed the tensile residual stress in case of non-restraint welding and the y direction residual stress under restraint welding were changed tensile stress into compressive stress about 60mm away from welding bead center.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.391-398
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• 1998

The purpose of this study was to find the distribution and measurement of compressive and tensile stress when intrusi- on arch wire is forced engage with upper canine and to analysis stress at each section through FEM. And we compare compressive and tensile ratio at each section. The results were as follows. 1. At FA point and cemento-enamel junction of upper canine, compressive and tensile force ratio is about the same. 2. At apex, compressive force is the four times as tensile force. ; In intrusion, we show root resorption at apex. 3. At Cemento-enamel junction, the compressive and tensile force show the maximun value except FA Point.

• Electrical & Electronic Materials
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• v.10 no.4
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• pp.327-333
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• 1997

Experiments on mechanical fatigue were conducted using the specimens which were cut from hydrogen cooled generator(rated 22kV and 50OMW) stator windings. We have investigated the aged mechanism of mica/epoxy insulation systems under air or hydrogen by both the tensile and compressive loadings. The fracture of generator stator windings is generally affected by mechanical stress. Thus, the tensile strength test were conducted. In this case, the maximum strength and strain are quite different between sound and aged specimens. It is observed that low bonded interface parts of tapes generally have lower strength than those of normal tapes which causes stress. In order to estimate the effects of cyclic load by the electromagnetic forces while the generator starts/stops, the mechanical fatigue test was also conducted. It is confirmed that the equation of expected life depends on stress amplitude and number of cycles. Though the stress amplitude and number of cycles are very tiny, the tensile fatigue of aged specimens under hydrogen atmosphere is bigger than those under air. In the case of hydrogen atmosphere, the tensile stress gives bigger effect than the compressive one.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.295-322
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• 2013

Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, toughness, energy absorption capacity and fracture toughness. Modification in the mix design of SCC may have a significant influence on the SFRSCC mechanical properties. Therefore, it is vital to investigate whether all of the assumed hypotheses for steel fiber reinforced concrete (SFRC) are also valid for SFRSCC structures. Although available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates material's mechanical properties. The present study includes: a) evaluation and comparison of the current analytical models used for estimating the mechanical properties of SFRSCC and SFRC, b) proposing new relationships for SFRSCC mixtures mechanical properties. The investigated mechanical properties are based on the available experimental results and include: compressive strength, modulus of elasticity, strain at peak compressive strength, tensile strength, and compressive and tensile stress-strain curves.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.118-121
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• 2006

The research reported here is concerned with the effects of the fiber combination condition and water/cement ratio on the mechanical properties of high performance fiber-reinforced cementitious composites(HPFRCC). An experimental investigation of the behavior of steel cords(SC) and SC and Polyethylene(PE) hybrid fiber reinforced cementitious material under compressive and tensile loading is presented. In this experimental research, the tensile and compressive strength and strain capacity of HPFRCC were selected using the cylindrical specimens. The results show that W/C ratio is a significant effect factor on the compressive and tensile performance of HPFRCC. The envelope curve concept applies to hybrid fiber-reinforced cementitious composites in tension just as it does to compressive stress-strain curve of fiber-reinforced cement composites. For practical purposes, the tensile envelope curve may be taken to be the same as the monotonic tensile stress-strain curve.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.3-11
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• 1999

The creep characteristics of concrete under tensile stress has been usually assumed to have the same characteristics as that under compressive stress in the time-dependent analysis of concrete structures. However, it appears from the recent experimental studies that tensile creep behavior is much different from compressive one. In particular, high sustaining tensile stress may cause time-dependent cracking and thus lead to tensile failure. It is, therefore, necessary to model the tensile creep behavior accurately for realistic time-dependent analysis of concrete structures. The present paper to have been focused to suggested more realistic model for the tensile creep behavior of concrete. The models are compared with tensile creep test data available in the literature. The proposed model may allow more refined analysis of concrete structures under time-dependent loading.