• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.723-730
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• 2012

During the cold wire-drawing process, the diameter of a wire is reduced and the length of the wire is increased as the wire passes through the die. The pressure and sliding motion at the interface between the wire and die cause elastic recovery of the workpiece and friction and wear on the die. In addition, wire deformation and frictional heating raise the temperature of the wire and die, resulting in difficulty in manufacturing the drawn products according to a designated inner diameter of the die, deviating from the designated dimension or the inner diameter of the die. In this study, considering the die temperature distribution, the effects of dimensional changes of the drawn products were analyzed quantitatively; these changes are caused by the elastic deformation of the die, the elastic recovery of the workpiece, and the thermal deformation of both the die and the workpiece. It was confirmed that the elastic recovery of the workpiece influenced these changes the most. The initial dies considering these factors could avoid deviation from the designated dimension, and the desired drawn products were obtained by using the designed initial drawing dies.

• 한국기계연구소 소보
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• s.19
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• pp.53-60
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• 1989

Hot upsetting experiments were carried out on presintered steel powder preforms in the temperature range 700- $950^{\circ}C$ to examine the hot deformation behavior. Following conclusions were drawn on the basis of the present study. -The flow stress during hot deformation is directly related to $\alpha$- $\gamma$ phase trasformation - The flow stress of ferrite is lower than that of austenite in the moderate temperature range 800- $900^{\circ}C$ for most alloys used in the present study - Major restoration behavior during hot deformation in the ferrite range is dynamic recovery.

• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.87-95
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• 1992

Recently, the robot actuator worked by the driving recovery-force of the thermo elastic martensitic transformation of shape memory alloys(SMA) has been studied. In general, such a SMA actuator necessitates a number of cyclic repeated motion, so that the investigation of gradual decrease of recovery force with repeated motion cycle as well as the prevention of such a degradation of shape memory effect(SME) are very important for the actual use of a robot actuator. However, such research and discussions about the degradation of SME are very few up to the present. Therefore, in this study, the characteristics of the cyclic deformation and degradation of SME of Ti-Ni alloy would be investigated and discussed in detail by current heat type fatigue tester, which is a newly designed fatigue tester by author. In addition, we will establish a new design concept for robot actuator from these result.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.4
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• pp.450-456
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• 2002

Die desig for manufacturing hooks from steel wires has been depended on empirical procedures based on trial and error method. To design die, at first the curvature and bending angle of hook are computed by using AutoCAD and developed program which is composed of Visual Basic. Then spring back should be considered because the elastic recovery of material is very important in bending process. In this study, bending analysis of elastic-plastic materials is applied to predict curvature of hook and spring back. Therefore, systematic procedure of die design for bending hook is achieved to consider elastic recovery in terms of hook shapes. Experimental results are good agreement with calculated results.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.323-323
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• 2000

In the tandem cold wiling mill, the quality is very in portant, and requirements for thickness accuracy become more strict. However, the mathematical model for prediction of rolling force was not considered an elastic deformation at the entry and delivery side of the contacted area between the worked roll and rolling strip so that there was so difficult to control of the thickness. To overcome this problem, the mathematical model included an elastic deformation of strip has been developed and applied to the field in order to predict the rolling force. The simulated results showed that the end of elastic recovery should be included the model, even if the effect of elastic compression was not important.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.101-107
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• 2009

Actuators using shape memory alloys use the one-way shape recovery stress. But when external load is applied the accumulated plastic strain induced by repeated deformation is the factor of generation of uncorrect recovery stress and unreliability. To solve this problem, two-way shape memory effect (TWSME) is considered. TWSME induced by plastic deformation have advantages including simple heating cycle without external force and enough recovery force for using actuators. but there is no research on cylinder-type or tube-type shape memory alloy actuators using two-way shape memory effect until now. Therefore in this study, characteristics of two-way shape memory effect is verified through the compression experiments using cylinder-type and tube-type specimens.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.6
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• pp.717-726
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• 2005

Statement of problem. One of the common problems of provisional crown and fixed partial denture materials is that when they are subjected to constant loads for a long period of time, they exhibit a dimensional change (creep). Purpose. The aim of this study was to investigate the viscoelastic behaviour of polymer-based provisional crown and fixed partial denture materials with time at constant compressive load. Material and methods. Three dimethacrylate-based materials (Protemp 3 Garant, Temphase, Luxatemp) and one monomethacrylate-based material (Trim) were selected. Dimensional changes of the specimens were recorded by a LVDT to evaluate their viscoelastic behavior and creep strain. For all specimens, two loading procedures were used. At first, static compressive stress of 4 MPa was applied for 30 minutes and followed by 1 hour of strain recovery. Then, after 24 hours of water storage, the specimens were loaded again. The creep values between materials were statistically analyzed using one-way ANOVA and multiple comparison $Scheff\acute{e}$ test. Independent samples t-test was also used to identify the difference of creep strain between first and secondary loading conditions at the significance level of 0.05. Results. Following application of the first loading, Trim showed the highest maximum creep strain (32.7%) followed by Luxatemp, Protemp 3 Garant and Temphase, with values of 3.78%, 2.86% and 1.77%, respectively. Trim was significantly different from other materials (P<0.05), while there were no significant differences among Luxatemp, Protemp 3 Garant and Temphase (P>0.05). The highest recovery and permanent set of Trim, were significantly different from those of others (P<0.05). At the secondary loading of the dimethacrylate-based materials, creep deformation, recovery and permanent set decreased and the percentage of recovery increased, while in Trim, all values of the measurements increased. This result showed that the secondary loading at 24 hours produced a significant creep magnitude. Conclusion. The dimethacrylate-based provisional crown and fixed partial denture materials showed significantly higher creep resistance and lower deformation than the monomethacrylate-based material. Thus, monomethacrylate-based materials should not be used in long-term stress-bearing situations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.125-132
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• 2010

In the recent construction industry, an external strengthening method using fiber reinforced polymers has been widely used. Since reinforced concrete structures strengthened with fiber reinforced polymers are always under sustained loads, influence of creep and shrinkage on the structures is inevitable. Due to the creep and shrinkage, behaviors of the structures, such as deflection, deformation, recovery capability, strength and so on are also under the influence of creep and shrinkage. Thus, in order to estimate efficacy, creep recovery and residual strength of FRP strengthened RC beams, long-term flexural experiments and static flexural experiments were carried out. As the result of the experiments, FRP strengthened RC beams were very effective in terms of deflection control. Furthermore, the strengthened beams had higher immediate deformation recovery than immediate deformation. Through the static flexural experiments, it was shown that the CFRP strengthened beam had high residual strength. It seems that the sustained loads did not affect bond and residual strength of the beams.

• Journal of Korea Foundry Society
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• v.22 no.1
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• pp.11-16
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• 2002

Hot deformation behavior of GCD-50 cast iron has been investigated by employing the compressive test. Phenomenological deformation behaviors, which were modeled based on the dynamic materials model and the kinetic model, have been correlated with the microstructural change taken place during compression. Microstructural investigation revealed that the adiabatic shear band caused by the locallized deformation was taken place in low temperature and high strain rate. On the other hand, the wavy and curved grain boundaries, which repersent the occurrence of dynamic microstructure change such as dynamic recovery and dynamic recrystallization, were observed in high temperature and low strain rate. Deformation model based on hyperbolic sine law has also been suggested.

• Fashion & Textile Research Journal
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• v.24 no.6
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• pp.812-824
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• 2022

This study proposes to develop a 3D printed re-entrant(RE) strip by shape memory thermoplastic polyurethane that can be deformed and recovered by thermal stimulation. The most suitable 3D printing infill density condition and temperature condition during shape recovery for mechanical behavior were confirmed. As the poisson's ratio indicated, the higher the recovery temperature, the closer the poisson's ratio to zero and the better the auxetic properties. After recovery testing for five minutes, it appeared that the shape recovery ratio was the highest at 70℃. The temperature range when the shape recovery ratio appeared to be more than 90% was a recovery temperature of more than 50℃ and 60℃ when deformed under a constant load of 100 gf and 300 gf, respectively. This indicated that further deformation occurred after maximum recovery when recovered at a temperature of 80℃, which is above the glass transition temperature range. As for REstrip by infill density, a shape recovery properties of 100% was superior than 50%. Additionally, as the re-entrant structure exhibited a shape recovery ratio of more than 90%, and exhibited auxetic properties. It was confirmed that the infill density condition of 100% and the temperature condition of 70℃ are suitable for REstrips for applying the actuator.