Change In Residual Strain Research Articles

Association between jejunal remodeling in fasting rats and hypersensitivity of intestinal afferent nerves to mechanical stimulation.

Remodeling of Intestinal properties and hypersensitivity of intestinal afferents to mechanical stimulation were previously demonstrated in a fasting rat model. Other studies investigated the association between mechanical and histological remodeling during fasting. This study aimed to further explore the relationship between the jejunal remodeling and intestinal afferent hypersensitivity by combining afferent nerve recordings with histological and mechanical data. Eight male Sprague Dawley rats had no access to food for 7days (Fasting group). Seven male rats served as controls (Control group). Jejunal segments were studied in vitro in an organ bath for analysis of afferent signaling and for analysis of mechanical and histomorphological parameters. Correlation analyses were done to analyze association between nerve activity (spike rate increase ratio, SRIR) at distension levels of 20, 40 and 80 cmH2O and mechanical stress and histomorphological changes of the jejunal segments. Compared with the Control group, the main findings in jejunal segments in the Fasting group were (1) Most histomorphometry parameters were reduced (P < 0.05-P < 0.001), (2) SRIR values were higher (P < 0.001), (3) The relative numbers of intermuscular and submucosal neurons were increased (P < 0.05-P < 0.01), and (4) SRIR was negatively correlated with intestinal wall thickness, circumferential muscle layer thickness and positively correlated with the inner residual strain, the number of neurons, and the mechanical stress. In conclusion, the fasting-induced histomorphological remodeling (reduced wall thickness and increased relative number of neurons) and biomechanical remodeling (residual strain changes and high stress level) of the intestine in fasting rats were associated with hypersensitivity of intestinal afferents. Afferent hypersensitivity appears to be dependent on stress rather than on strain.

Functional Behavior of Pseudoelastic NiTi Alloy Under Variable Amplitude Loading

Abstract Cyclic loading of superelastic NiTi shape memory alloy (SMA) causes forward and reverse austenite–martensіte transformations, and also increases the volume of stabilized martensite. This appears in the change of stress-strain curve form, the decrease of dissipation energy, and increase of residual strain, that is, named transformation ratcheting. In real structures, the SMA components in most cases are under the action of variable amplitude loading. Therefore, it is obvious that the loading history will influence the functional fatigue. In the present work, the effect of stress ratio on the functional properties of superelastic NiTi shape memory alloy under variable amplitude loading sequence with two blocks was investigated. The studies were carried out under the uniaxial tension of cylindrical specimens under load-full unload and load-part unload. The change of residual strain, strain range, dissipation, and cumulative dissipation energy density of NiTi alloy related to load sequences are discussed. Under both stress ratios, the residual strain in NiTi alloy is increased depending on the number of loading cycles on the high loading block that is similar to the tests at constant stress or strain amplitude. An unusual effect of NiTi alloy residual strain reduction with the number cycles is found at a lower block loading. There was revealed the effect of residual strain reduction of NiTi alloy on the number of loading cycles on the lower amplitude block. The amount of decrement of the residual strain during a low loading block is approximately equal to the reversible part of the residual strain due to the stabilized martensite. The decrease of the residual strain during the low loading block is approximately equal to the reversible part of residual strain due to the stabilized martensite. A good correlation of the effective Young’s modulus for both load blocks with residual strain, which is a measure of the volume of irreversible martensite, is observed.

Mechanical oscillations in the technological processes of restoration of machine parts

The paper addresses the issues of increasing the durability of piston pins of automotive and tractor engines through the use of vibration oscillations during their restoration. Experimentally found the optimal values of the angle of inclination of the machined tool – punch and its effect on the amount of metal sticking to the working surface of the punch, which reduces the quality of the processed surface of the piston pins and increases the non-uniformity of deformation in the radial direction and length. The change of the residual strain along the outer and inner diameter of the piston pin during vibratory deformation is shown. The obtained mathematical dependences of the change in residual strain on the outer diameter on the value of the allowance for processing. Experimentally found a relationship that associates residual deformation with the wear of piston pins. The results of the work will be used for the development of technological processes for the restoration of piston pins and bushings of the top heads of connecting rods of various autotractor engines by the method of vibration deformation.

Study on cyclic deformation behavior of shape memory alloy materials considering damage and the residual strain

This article combines experimental tests and theoretical studies to study the deformation behavior of SMA materials under uniaxial tension cycles considering residual strain and damage. In the laboratory test of SMA material, the critical phase transformation temperatures are firstly measured by DSC curve, and then do the uniaxial tensile test to measure the young's modulus of the martensite and austenite, finally the stress-strain relationship curve under uniaxial tension cycle is approximated, and the relationship between residual strain and cycle number is approximated, then the relationship between damage factor and cycle number is derived by the relationship between the attenuation of the Young's modulus and the cycle number. In the theoretical research, fully consider the influence of damage on the material's permanent maturity in a single cycle and consider the change of residual strain during the cycle, a thermodynamic constitutive model that can simulate the cyclic deformation behavior of SMA materials considering damage and residual strain is established and the numerical results were compared with the experimental results to verify the correctness of the model.

Effect of solution heat treatment on residual stress in Al alloy engine blocks using neutron diffraction

Tensile residual stress in the cylinder bore region is a significant problem associated with Al engine blocks containing cast-in gray iron cylinder liners as it can result in cylinder distortion or engine block fracture. These issues can lead to significant environmental (emissions) and economic (recalls) problems for automotive OEMs. In this study, in-situ and ex-situ neutron diffraction was used to measure the change in residual strain in the cylinder bridge as a function of time during solution heat treatment and map to the stress profiles following heat treatment. A heating system, consisting of coiled tubular heaters in the cylinder bores and strip heaters along the front and side faces of the engine block, was designed and built to heat the blocks to the solution temperatures The results indicated that solutionizing at 470°C caused a gradual relief of tensile residual strain up to approximately 5h, where strain was completely relieved. At 500°C, the strain relieved more rapidly, which resulted in complete relief in under 0.5h. Cooling to ambient temperature caused the partial re-development of tensile residual stress throughout the cylinder depth due to thermo-mechanical mismatch, however the magnitude was lower than for the as-cast condition.

Evaluation of the influence of cooling rate on residual strain development in unidirectional carbon fibre/polyphenylenesulfide laminates using embedded fibre Bragg grating sensors

This study investigates the influence of cooling rate on the residual strain of the carbon fibre/polyphenylenesulfide unidirectional laminates. Three different cooling rates (−300℃/min, −100℃/min and −10℃/min) were applied to simulate a wide range of cooling conditions. The crystallisation behaviour which depends on the cooling rate was evaluated using differential scanning calorimetry. A process monitoring test was then conducted using embedded fibre Bragg grating sensors. In-plane transverse strain of carbon fibre/polyphenylenesulfide unidirectional laminates was measured and the results were presented based on the crystallisation behaviour determined by differential scanning calorimetry. Furthermore, residual strain change after subsequent annealing was examined. This study successfully demonstrates the effectiveness of in situ process monitoring using fibre Bragg grating sensors for evaluating material behaviour of thermoplastic composites during rapid heating and cooling under realistic processing conditions.

OS0302 歯科修復用コンポジットレジンの静的負荷による内部損傷の評価

Columnar specimens were made of resin composites by light curing. The specimens were subjected to static compressive stress. The compressive stress was unloaded when the stress attained to the specified value. Then loading and unloading were repeated with the specified stress increased gradually. Young's modulus was evaluated by gradient of stress-strain curve just after starting unloading. Moreover, apparent density was also measured by the Archimedes' method. Then variation in Young's modulus and apparent density with maximum applied stress increased was clarified. On the other hand, change in residual strain after unloading was clarified in two cases. One is the case in which loading and unloading were repeated in a specimen with the maximum stress increased, and the other is the case in which a set of loading and unloading was made in a specimen once. In the latter case, the maximum stress was changed when a specimen was changed. Finally, a scalar damage variable was evaluated by the variation in Young's modulus from the initial value, and the features of damage development were discussed.

605 IF鋼のひずみ時効硬化異方性(OS4-1 オーガナイズドセッション《材料・組織と加工》)

The work-hardening characteristics of anisotropic tensile deformations and the corresponding residual strain changes of pre-strained ferrite single-phased steels without and with aging treatment were investigated by using in-situ neutron diffraction. The plastic deformation along the pre-strained direction shows discontinuous yielding behavior at the beginning stage. On the other hand, the plastic deformation perpendicular to the pre-strained direction shows continuous yielding. An anisotropy of mechanical property in steel is induced by deformation direction and strain ageing. As a result, the tensile and compressive residual strains were found in the <200> and <110> grains along the pre-strained direction, respectively. It is also found that the work hardening rate along the pre-strained direction is higher than that of perpendicular to the pre-strained direction after strain-ageing, resulting in the deference of residual strain among the crystal orientations.

Filamentary MgB2 wires twisted before and after heat treatment

Two different filamentary MgB2 wires were subjected to twisting before and also after the final heat treatment(HT). Wires twisted before HT showed only degraded critical currents (Ic) starting from theratio Lt/dw < 30–40, whereLt is the twist pitchand dw is the wirediameter. Increased Ic (by 8.0–20%) were measured for wires twisted after HT at anLt/dw ratio of 38–90 depending on the annealing conditions (temperature/time) and also on wire composition. Reduced irreversible strain (εirr) was also measured for wires twisted after HT. ImprovedIc and decreasedεirr of examinedfilamentary MgB2 wires are explained by the change of residual strain inside the composite wire caused bytorsion stress.

Volume Changes in Filled Rubber Under Uniaxial Cyclic Loading

Styrene-butadiene rubber, neat and filled with different silica content was investigated under uniaxial cyclic loading under a constant crosshead speed, with increasing deformation amplitude in subsequent loading cycles. Rubber was investigated in order to evaluate the reversibility of structure rearrangements, occurring in rubber when subjected to cyclic loading. Volume uniformly increases with growing strain and shows hysteresis at unloading. After complete unloading, no residual strain changes are observed. These data are in good conformity with the data of density measurements, which were made on specimens before and after the tests. By correlating data, obtained from volume changes and kinetics of hysteresis losses there were made assumptions on deformation mechanisms at different elongations. Deformational mechanisms, responsible for volume changes in rubber are reversible. Volume changes in specimen occur due to voids formation caused by filler microstructure breakage, rubber chains disentanglement, spaces between rubber macromolecular chains shrinkage, and chain slippage under higher elongations. Voids formation and deformation of rubber macromolecular chain reaches equilibrium state after certain elongation. http://dx.doi.org/10.5755/j01.ms.17.3.592

Biomechanical and Histomorphometric Colon Remodelling in STZ-Induced Diabetic Rats

The histomorphologic and passive biomechanical properties were studied in the mid-colon of 16 non-diabetic and 20 streptozotocin (STZ)-induced diabetic rats (50 mg/kg STZ, ip). The diabetic rats were divided into groups living 4 and 8 weeks after the induction of diabetes (n = 10 for each group). The mechanical test was a ramp distension of fluid into the colon in vitro. The colon diameter and length were obtained from digitized images of the segments at pre-selected pressures and at the no-load and zero-stress states. Circumferential and longitudinal stresses and strains were computed from the length, diameter, and pressure data and from the zero-stress state geometry. The blood glucose level increased 3-4-fold in the diabetic rats compared with the controls (P < 0.001). Diabetes generated pronounced increases in the colon weight per length, wall thickness, and wall cross-sectional area (P < 0.001). Histologically, the thickness of all layers was increased during diabetes (P < 0.05), especially the mucosa layer. The opening angle, and absolute values of residual strain increased in the diabetic group (P < 0.05 and P < 0.01, respectively). Furthermore, diabetes increased the circumferential and longitudinal stiffness of the colon wall (P < 0.001). The observed changes in residual strain, opening angle, and stress-strain relation may be contributing factors to colonic dysfunction and abdominal pain in diabetic patients.

Analysis of the residual strain change of Bi2212, Ag alloy and Ag during the heating andcooling process in Bi2212/Ag/Ag alloy composite wire

The residual strain change of Bi2212 and Ag during the cooling and heating process in theBi2212/Ag/Ag alloy composite superconductor was studied. First, the residual strain ofBi2212 filaments at room temperature was measured by the x-ray diffraction method.Then, the Young’s moduli of the constituents (Bi2212 filaments, Ag and Ag alloy) andyield strains of Ag and Ag alloy were estimated from the analysis of the measuredstress–strain curve, based on the rule of mixtures. Also, the coefficient of thermal expansionof the Bi2212 filaments was estimated from the analysis of the measured thermal expansioncurve of the composite wire. From the modeling analysis using the estimated propertyvalues and the residual strain of Bi2212 filaments, the changes of residual strain of Bi2212,Ag alloy and Ag with temperature during the cooling and heating process wererevealed.

An experimental study of the mouse skin behaviour: Damage and inelastic aspects

Samples of male and female mice skin were tested under monotonic and cyclic loading to mechanically characterize the tissue for large deformations. Cyclic tests have shown a typical Mullins effect widely known for elastomers and other soft tissues. No statistical difference was found in the maximum stretch of the sample after the fifth loading cycle for male ( 1.26 ± 0.035 ) and female ( 1.18 ± 0.083 ) . However, larger dispersion was obtained for the maximum stress for both genders, 0.61 ± 0.16 MPa for male and 0.78 ± 0.32 MPa for female. Results show the presence of inelastic strain and stress softening in the skin at large deformations. They also have shown how stress softening and residual strain change with the magnitude of the applied load. Good correlation was observed between the residual strain and the maximum strain previously attained by the sample during loading for all samples. However, the correlation was different between genders.

Neutron Diffraction Study on Prebending Effects for Bronze Route&lt;tex&gt;$rm Nb_3rm Sn$&lt;/tex&gt;Wires Without Reinforcement

The critical current, upper critical field and critical temperature of bronze route Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn commercial wires are enhanced by applying a repeated bending strain at room temperature, i.e., "prebending strain". In order to investigate the prebending effects from a viewpoint of a residual strain, axial and lateral residual strains were evaluated directly by neutron diffraction at room temperature. We found that the axial residual strain changes from -0.10% to 0.02 % but the lateral one is unchanged by applying a prebending strain of 0.5% for an ordinary bronze route (Nb,Ti) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires without reinforcement. Hence, in the case of the ordinary Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires without reinforcement, the prebending treatment modifies only the axial residual strain states independently to the lateral one, although it may depend on the wire structure. The critical current properties under the axial tensile strain suggest that the axial residual strain is reduced by about 0.11% but the radial residual strain unchanged by the prebending treatment of 0.5%. This is consistent with the results of the neutron diffraction

Theoretical evaluation of the change in residual strain on the rabbit aorta with atherosclerotic plaques

Theoretical evaluation of the change in residual strain on the rabbit aorta with atherosclerotic plaques

1A1-C24 高分子電解質膜アクチュエータ(ICPF)の位置決め制御への応用 : 第3報:長時間位置決め特性に及ぼす稼動イオンの影響と,直線変位型位置決めアクチュエータの試作

Nation based precious metal plating ion conductive polymer-gel film (ICPF) actuator is very attractive because of its high-speed response and softness of the material. The deformation characteristics, especially the generating direction of residual strain changes with the density or the amount of the Na+ driving ion. If the residual strain generates the same side of the initial strain, the displacement of the ICPF can be controlled by popular integral control method. In this paper, the long timedeformation characteristics of Au-NF 115 ICPF was investigated and linear motion type displacement positioning actuator was produced.

Fatigue Property of Super-Elastic Ti&amp;ndash;Ni Alloy Dental Castings

Ti–Ni alloy is a promising material in the medical and dental fields due to its special mechanical properties, especially super-elasticity. Since dental prostheses are generally used under repetitive stress condition, fatigue properties of Ti–Ni alloy castings were investigated in this study. Ti–50.85Ni (mol%) alloy ingots were used for casting, which exhibited super-elasticity at 310 K in tensile test. Specimens were prepared with a centrifugal casting machine and a magnesia-based mold material. Fatigue test was performed at 310 K under repetitive loading condition with sine-waved load. The minimum stress was set at 0 MPa to evaluate the fatigue properties and change in residual strain. The maximum stress was set in the appropriate range considering the tensile property. Ultimate tensile strength and elongation to fracture of Ti–Ni alloy castings were 732 MPa and 10.6%, respectively, which were between those of CP-Ti and Ti–6Al–4V alloy castings. The fatigue limit of Ti–Ni alloy casting (206 MPa) was equivalent to or higher than that of CP-Ti or Ti–6Al–4V alloy. There was linear correlation between the fatigue ratios to ultimate tensile strength and the elongation to fracture for Ti–Ni alloy, CP-Ti and Ti–6Al–4V alloy castings, while Ti–Ni alloy showed high fatigue ratio to proof stress, which appears to relate to the twin deformation by stress-induced martensitic transformation. The stress-strain properties of Ti– Ni alloy castings were evaluated to be stable, and it is possible to utilize the super-elasticity in cast dental prostheses.

A constitutive model for the Mullins effect with permanent set in particle-reinforced rubber

Stress softening during initial loading cycles, known as the Mullins effect, and the residual strain upon unloading are not accounted for when the mechanical properties of rubber are represented in terms of a strain-energy function, i.e. if the material is modelled as hyperelastic. In this paper we first describe some experimental results that illustrate stress softening in particle-reinforced rubber together with associated residual strain effects. In particular, the results show how the stress softening and residual strain change with the magnitude of the applied strain. Then, on the basis of these data a constitutive model is derived to describe this behaviour. The theory of pseudo-elasticity is used for this model, the basis of which is the inclusion of two variables in the energy function in order separately to capture the stress softening and residual strain effects. The dissipation of energy, i.e. the difference between the energy input during loading and the energy returned on unloading is also accounted for in the model by the use of a dissipation function, which evolves with the deformation history.

Mechanical and morphological study of biostable polyurethane heart valve leaflets explanted from sheep.

Two novel biostable polyurethanes, designated EV3.34 and EV3.35, were used to manufacture a flexible trileaflet heart valve. The valves were implanted in the mitral position in young adult (18 month) sheep. Six valves were electively explanted at 6 months and the remaining six valves at 9 months follow-up. The leaflet material was examined by surface Fourier transform infrared spectrometry (ATR/FTIR) and scanning electron microscopy (SEM). The leaflet material was also subjected to cyclic mechanical testing and, compared with unimplanted control material, to demonstrate any change in mechanical properties during implantation. There was no degradation of functional groups detected by ATR/FTIR, although there was a slight surface enrichment of siloxane soft segment. Surface morphology of the explanted leaflet material was similar to unimplanted control material. EV3.34 demonstrated similar inelastic energy loss behavior, with no significant change in residual strain in explanted compared with control material. EV3.35 demonstrated a reduction in inelastic energy and residual strain in explanted compared with control material. There is no evidence of biodegradation of these siloxane-based polyurethanes, in functional valves up to 9 months implantation in sheep. The FTIR and SEM findings are supported by the retention of mechanical properties of the materials.

Effect of Copper Content on Superelasticity Characteristics in Ti-Ni and Ti-Ni-Cu Alloy Wires

The effect of copper content on superelasticity characteristics in Ti–Ni and Ti–Ni–Cu alloy wires was investigated by performing isothermal cyclic tensile tests at a temperature of Af + 25 K. Specimens were Ti–50Ni, Ti–45Ni–5Cu, Ti–40Ni–10Cu and Ti–37Ni–13Cu(at%), annealed at 673 K for 3.6 ks after cold drawing with 30% reduction. The results show that the changes in residual strain, the critical stress for inducing martensite and the strain energy in all alloys are significant in early cycles, but become insignificant after 10 cycles. The degradation of residual strain and the strain energy during loading increases with decreasing copper content. However, changes in the critical stress for inducing martensite and the dissipated strain energy in Ti–Ni–Cu alloys are insensitive to copper content. Furthermore, in order to clarify the effect of copper content on the degradation of materials functions, the volume fraction of martensite subjected to slip deformation is evaluated by a two-phase model consisting of the parent phase and the martensitic phase connected in series. The volume fraction for a residual strain becomes larger as copper content increases, and it is directly related to the critical stress for inducing martensite and the dissipated strain energ y with number of cycles. Based on these results it can be stated that the volume fraction of martensite subjected to slip deformation is a measure which represents the effects of cyclic deformation and copper content on the degradation of materials functions.