Rolling Plane Research Articles

Improvement of strength and toughness for hot rolled low-carbon bainitic steel via grain refinement and crystallographic texture

Low-carbon bainitic steel with effective grain size of ~2.0µm and strong <110>//RD (rolling direction) transformation texture was obtained by adopting ultra fast cooling following non-recrystallization rolling. The steel exhibited higher tensile strength of ~840MPa and lower ductile-to-brittle transition temperature of ~−106°C in comparison with the steel that had no distinct texture with effective grain size of ~4.5µm. High intensity of {110} planes normal to the rolling direction were formed as a result of the strong {114}~{223}<110> transformation texture and effectively inhibited the main crack propagation by ductile fracture mechanism. The existing {100} planes parallel to the rolling plane led to the impact fracture delamination at −20~−100°C, which improved the low temperature toughness.

Superelastic alloy Ti-22%Nb-6%Zr: X-ray study of deformation features

In this paper features of deformation of superelastic Ti-22%Nb-6%Zr alloy were studied. Using X-ray method of generalized pole figures for study orientation dependence of martensite transformation in superelastic Ti-22%Nb-6%Zr alloy it was shown that: under compression the strain hardening due β → α '' transformation is significantly greater in grains with rolling plane {100} than in grains with a rolling plane {111}; the lattice microdeformation at β - and α '' - phase grains under loading is redistributed so that it extremely assist the sample macrodeformation (most of all); most intense β → α '' transformation occurs in grains, where Δd / dav> 0, most prone to increasing of its lattice volume. Diagrams of the cross-correlation substructural parameters built on the basis of generalized pole figure indicate that in loaded sample the deviation of interplanar space from the weight average level promotes the activation of martensite transformation at which the X-ray line broadening is minimal.

Effect of layerwise structural inhomogeneity on stress- corrosion cracking of steel tubes

Based on X-ray texture and structure analysis data of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The degree of this inhomogeneity affects on the tendency of tubes to stress- corrosion cracking under exploitation. Samples of tubes were cut out from gas pipelines located under various operating conditions. Herewith the study was conducted both for sections with detected stress-corrosion defects and without them. Distributions along tube wall thickness for lattice parameters and half-width of X-ray lines were constructed. Crystallographic texture analysis of external and internal tube layers was also carried out. Obtained data testifies about considerable layerwise inhomogeneity of all samples. Despite the different nature of the texture inhomogeneity of gas pipeline tubes, the more inhomogeneous distribution of texture or structure features causes the increasing of resistance to stress- corrosion. The observed effect can be explained by saturation with interstitial impurities of the surface layer of the hot-rolled sheet and obtained therefrom tube. This results in rising of lattice parameters in the external layer of tube as compared to those in underlying metal. Thus, internal layers have a compressive effect on external layers in the rolling plane that prevents cracks opening at the tube surface. Moreover, the high mutual misorientation of grains within external and internal layers of tube results in the necessity to change the moving crack plane, so that the crack growth can be inhibited when reaching the layer with a modified texture.

Verticality Perceptions Associate with Postural Control and Functionality in Stroke Patients.

Deficits of postural control and perceptions of verticality are disabling problems observed in stroke patients that have been recently correlated to each other. However, there is no evidence in the literature confirming this relationship with quantitative posturography analysis. Therefore, the objectives of the present study were to analyze the relationship between Subjective Postural Vertical (SPV) and Haptic Vertical (HV) with posturography and functionality in stroke patients. We included 45 stroke patients. The study protocol was composed by clinical interview, evaluation of SPV and HV in roll and pitch planes and posturography. Posturography was measured in the sitting and standing positions under the conditions: eyes open, stable surface (EOSS); eyes closed, stable surface (ECSS); eyes open, unstable surface (EOUS); and eyes closed, unstable surface (ECUS). The median PV in roll plane was 0.34° (-1.44° to 2.54°) and in pitch plane 0.36° (-2.72° to 2.45°). The median of HV in roll and pitch planes were -0.94° (-5.86° to 3.84°) and 3.56° (-0.68° to 8.36°), respectively. SPV in the roll plane was correlated with all posturagraphy parameters in sitting position in all conditions (r = 0.35 to 0.47; p < 0.006). There were moderate correlations with the verticality perceptions and all the functional scales. Linear regression model showed association between speed and SPV in the roll plane in the condition EOSS (R2 of 0.37; p = 0.005), in the condition ECSS (R2 of 0.13; p = 0.04) and in the condition EOUS (R2 of 0.22; p = 0.03). These results suggest that verticality perception is a relevant component of postural control and should be systematically evaluated, particularly in patients with abnormal postural control.

Abnormal Tilt Perception During Centrifugation in Patients with Vestibular Migraine.

Vestibular migraine (VM), defined as vestibular symptoms caused by migraine mechanisms, is very common but poorly understood. Because dizziness is often provoked in VM patients when the semicircular canals and otolith organs are stimulated concurrently (e.g., tilting the head relative to gravity), we measured tilt perception and eye movements in patients with VM and in migraine and normal control subjects during fixed-radius centrifugation, a paradigm that simultaneously modulates afferent signals from the semicircular canals and otoliths organs. Twenty-four patients (8 in each category) were tested with a motion paradigm that generated an inter-aural centrifugal force of 0.36G, resulting in a 20° tilt of the gravito-inertial force in the roll plane. We found that percepts of roll tilt developed slower in VM patients than in the two control groups, but that eye movement responses, including the shift in the eye's rotational axis, were equivalent in all three groups. These results demonstrate a change in vestibular perception in VM that is unaccompanied by changes in vestibular-mediated eye movements and suggest that either the brain's integration of canal and otolith signals or the dynamics of otolith responses are aberrant in patients with VM.

The Effect of Age on Improvements in Vestibulo-Ocular Reflexes and Balance Control after Acute Unilateral Peripheral Vestibular Loss.

An acute unilateral peripheral vestibular loss (aUVL) initially causes severe gaze and balance control problems. However, vestibulo-ocular reflexes (VOR) and balance control are nearly normal 3 months later as a result of peripheral recovery and/or central compensation. As pre-existing vestibular sensory loss is assumed to be greater in the healthy elderly, this study investigated whether improvements in VOR and balance function over time after aUVL are different for the elderly than for the young. Thirty aUVL patients divided into three age-groups were studied (8 age range 23-35, 10 with range 43-58, and 12 with range 60-74 years). To measure VOR function eye movements were recorded during caloric irrigation, rotating chair (ROT), and head impulse tests. Balance control during stance and gait was recorded as lower trunk angular velocity in the pitch and roll planes. Measurements were taken at deficit onset, and 3, 6, and 13 weeks later. There was one difference in VOR improvements over time between the age-groups: Low acceleration ROT responses were less at onset in the elderly group. Deficit side VOR responses and asymmetries in each group improved to within ranges of healthy controls at 13 weeks. Trunk sway of the elderly was greater for stance and gait at onset when compared to healthy age-matched controls and the young and greater than that of the young and controls during gait tasks at 13 weeks. The sway of the young was not different from controls at either time point. Balance control for the elderly improved slower than for the young. These results indicate that VOR improvement after an aUVL does not differ with age, except for low accelerations. Recovery rates are different between age-groups for balance control tests. Balance control in the elderly is more abnormal at aUVL onset for stance and gait tasks with the gait abnormalities remaining after 13 weeks. Thus, we conclude that balance control in the elderly is more affected by the UVL than for the young, and the young overcome balance deficits more rapidly. These differences with age should be taken into account when planning rehabilitation.

Influence of loading direction on the anisotropic fatigue properties of rolled magnesium alloy

The influence of loading direction on the fatigue behavior of rolled AZ31 alloy was investigated by conducting fully reversed stress-controlled fatigue tests along the rolling direction and normal to the rolling plane. Alternating twinning and detwinning behavior during initial cycling was found to cause asymmetric hysteresis loops, resulting in a compressive strain in the rolling direction and a tensile strain normal to the rolling plane. A transition in the dominant deformation mechanism from twinning–detwinning to slip occurs at around five cycles under both conditions due to cyclic hardening, thus making their loops symmetric. The lower twinning stress in tension along the normal direction leads to an increase in fatigue damage by plastic strain, resulting in a lower fatigue resistance than along the rolling direction.

The Subjective Postural Vertical Determined in Patients with Pusher Behavior During Standing

Background: The subjective postural vertical (SPV), i.e., the perceived upright orientation of the body in relation to gravity, is disturbed in patients with pusher behavior. So far, the SPV has been measured only when these patients were sitting, and the results were contradictory as regards the side of the SPV deviation.Objective: The objective was to investigate the SPV in patients with different degrees of severity of pusher behavior while standing.Methods: Eight stroke patients with pusher behavior, ten age-matched stroke patients without pusher behavior, and ten age-matched healthy control subjects were included. The SPV (SPV error, SPV range) was assessed in the pitch and the roll planes. Pusher behavior was classified with the Burke Lateropulsion Scale (BLS).Results: In the pitch plane, the SPV range was significantly larger in pusher patients than in patients without pusher behavior or healthy controls. The SPV error was similar for groups. In the roll plane, the SPV error and the SPV range were significantly larger and more ipsilesionally tilted in the pusher group than in the other two groups. There was a significant correlation between the SPV error in the roll plane and the BLS score.Conclusions: The study revealed that patients with pusher behavior had an ipsilesional SPV tilt that decreased with decreasing severity of the behavior. The large uncertainty in verticality estimation in both planes indicates that their sensitivity for the perception of verticality in space is generally disturbed. These findings emphasize the importance of specific rehabilitation approaches to recalibrate the impaired inner model of verticality.

An efficient methodology for simulating roll dynamics of a tank vehicle coupled with transient fluid slosh

An efficient methodology is proposed for simulation of roll dynamics of a tank vehicle system coupled with transient hydrodynamic forces due to fluid slosh. The transient fluid slosh in a horizontal cylindrical tank is analytically modeled considering simultaneous lateral, vertical and roll excitations assuming potential flows and a linearized free-surface boundary condition. For this purpose, the fluid domain in the Cartesian coordinate system is transformed to the bipolar coordinates, where the Laplace equation could be solved using separation of variables. The resulting hydrodynamic pressure, free-surface elevation and slosh force and roll moment are formulated in the tank-fixed coordinate system. The transient fluid slosh model is subsequently integrated to a dynamic roll plane model of a tank vehicle combination to investigate the effect of transient liquid slosh on the roll stability of the vehicle during steady-turning as well as path-change maneuvers. The analyses are performed for different fluid fill heights considering both variable and constant cargo load conditions. The results suggest that the roll stability of tank vehicles can be efficiently analyzed using the coupled linear slosh and multi-body vehicle models with significantly lower computational effort than the methods employing computational fluid dynamic fluid slosh models.

Effect of anisotropic microstructure of a 12Cr-ODS steel on the fracture behaviour in the small punch test

Oxide dispersed strengthened steels can exhibit a strongly anisotropic microstructure with elongated pancake-like grains in the rolling plane. This gives rise to intergranular fracture and subsequent delamination along large-area grain boundaries. We investigated an oxide dispersed strengthened alloy with 12 mass percent Cr, manufactured by mechanical alloying, hot extrusion and cold rolling by means small punch tests and subsequent fractographic analysis. The fracture behaviour was analysed in dependence of the specimen orientation. The results from small punch tests were contrasted with those from impact tests with sub-sized samples. In both tests, the ductile to brittle transition temperatures as well as the upper shelf energies depend significantly on the orientation of the specimens. However, the delamination affects the fracture of impact and small punch test samples in different ways. Thus, it depends on the load situation whether delamination has a beneficial or a detrimental effect on the fracture behaviour.

Real-time bus rollover prediction algorithm with road bank angle estimation

The bus rollover warning has achieved many progresses for researcher endeavors in the past decades. But these researches have not taken account for dynamic road bank. To fill up the gap, this paper presents a real-time rollover trend prediction to indicate bus rollover risk with road bank estimation. The prediction algorithm consists of a dynamic roll stability analysis, which is based on a suspended roll plane model, and a real-time warning velocity calculation. An estimator for the dynamic road bank and vehicle sideslip angle estimation using the dynamic simplex algorithm (DSA) is designed to take into account the influence of road bank on rollover trend. By comparing maximum stable lateral acceleration to the affordable lateral acceleration depending on the tire/road friction limit, a warning velocity is determined using the measurement of lateral acceleration and the estimate of instantaneous vehicle turning radius. The proposed rollover trend prediction algorithm is evaluated by TruckSim software. Simulation results show that the proposed warning velocity can represent the vehicle potential to resist rollover and give appropriate prediction of vehicle rollover crashes in typical scenarios.

The formation of delamination cracks in impact-toughness tests as a cause of the increase in the impact toughness of steels with bcc structure

The role of weakened surfaces parallel to the plane of rolling in the formation of delamination cracks in the course of impact-toughness testing of steels with the bcc structure subjected to high-temperature thermomechanical treatment has been theoretically substantiated. A mechanism of increasing impact toughness during the formation of delamination cracks has been described using 08Kh18T1 steel as an example. It has been shown that the stress state that arises in a material with weakened surfaces can be modeled using composite specimens.

An Analytical Framework for Predicting the Limit in Structural Refinement in Accumulative Roll Bonded Nickel

The limit in structural refinement of lamellar bands (LBs) generated during accumulative roll bonding (ARB) of commercially pure nickel was investigated by transmission electron microscopy and transmission Kikuchi diffraction. A typical LB consists of an internal cellular substructure of low angle boundaries (LABs) bounded by two high angle boundaries (HABs) that are aligned parallel to the rolling plane. At low true strains (e 4.8; 6 to 10 ARB cycles), a homogenous distribution of well-defined, highly elongated LBs of average thickness 75 nm was generated throughout the entire thickness of the material. The thickness of these LBs decreased with increasing number of ARB cycles and reached a saturation thickness of ~75 nm after 6 to 8 cycles. A theoretical framework for the limit to LB refinement during ARB is presented based on the refinement rate due to the stored energy of deformation balanced by the growth rate caused by adiabatic heating. The analysis takes into account the unique features of LB structures and processing parameters.

Effects of Initial Texture on Rolling Texture and Property of Electrodeposited Nickel Plate

By cutting electro-deposited nickel plates at different angles between the rolling planes and the growth plane, we obtained bulk samples with different initial textures. We investigated the microstructures, macrotextures, and microhardness of such samples before and after cold rolling. The results showed that the samples cut at different angles have different initial textures before the cold rolling, and their microstructures changed from isotropic crystals to columnar ones as the cutting angle increased. After cold rolling, the deformed microstructures textures were the same. However, the microhardness of the material was closely related to the cutting angle. As the cutting angle increased, the microhardness decreased significantly. This phenomenon is associated with the dimensional differences between the axial and horizontal directions of the columnar crystal grains of the electro-deposited materials.

Relationships among crystallographic texture, fracture behavior and Charpy impact toughness in API X100 pipeline steel

The crystallographic texture and Charpy impact toughness have been investigated in American Petroleum Institute (API) X100 pipeline steel, and the different rolling processes are applied to adjust the crystallographic texture for the sake of improving impact toughness. It has been found that the very weak textures exist in the steel only rolled in the recrystallization region of austenite, but the intensity of the unfavorable {001} 〈110〉 component is quite high. The {001} 〈110〉 texture is harmful for impact toughness and needed to be decreased in most cases. It is confirmed that the appropriate controlled rolling processes effectively reduce the intensity of the {001} 〈110〉 texture. By contrast, low temperature finish rolling in the non-recrystallization region produces the fine grain structures, beneficial textures and superior impact toughness at the low temperature. In addition, the occurrence of delamination in the ductile region generates the unfavorable cleavage crack on the fracture surface of Charpy specimen and inevitably reduces the impact energy in the upper shelf region. The delamination will occur continuously with decreasing temperature due to the large volume fraction of {001} planes parallel to the rolling plane.

Texture evolution of rolled Mg–3Al–1Zn alloy undergoing a {10-12} twinning dominant strain path change

The texture modification, caused by {10-12}–{10-12} double twinning, in rolled Mg–3Al–1Zn alloy was investigated by carrying out consecutive in-plane compressions along two orthogonal directions in combination with an electron backscatter diffraction measurement and a Schmid factor analysis. The results revealed that the Schmid law still governs twin variant selection, thereby controlling texture evolution, however, the specific crystallographic feature of {10-12} twinned region in which the c-axis orients to the compression direction with a variation of ±30° on the rolling plane and one prismatic plane including the rotation axis of {10-12} twinning, corresponding to an a-axis, is aligned almost parallel to the rolling plane gives rise to a significantly different texture evolution of {10-12}–{10-12} double twinned region as compared to {10-12} twinned region.

Study of texture and microstructure evaluation of steel API 5L X70 under various thermomechanical cycles

This work studies the influence of different thermomechanical paths on the microstructure and crystallographic texture across the thickness of API 5L X70 pipeline steel manufactured via hot rolling using X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscattered diffraction (EBSD). The starting materials were controlled hot-rolled at 1000°C to 44% and 67% reductions and subsequently heat treated with such processes as annealing, water quenching and quench tempering at three different temperatures to evaluate the microstructure and crystallographic texture changes across the thickness. The banded ferrite-pearlite microstructure of the initial material was changed to acicular ferrite, quasi-polygonal ferrite, granular bainite, martensite and retained austenite via different heat treatments. Moreover, different thermomechanical paths induced crystallographic texture variations across the thickness, e.g., {112}//ND, {111}//ND 11The notation {hkl}//ND (Normal Direction) represents grain orientations with {hkl} planes parallel to the rolling plane [1]. (γ fibre), and {011}//ND fibres dominated on the surface plane in contact with the rolls, whereas {001}//ND and particularly the (001)[110] texture component developed in the centre plane on which shear deformation has a zero value in this region. In this study, a simple interpretation of texture evolution was analyzed by comparison with the orientation changes that occurred during different rolling schedules and post-treatment processes.

Quantitative Crystal Structure Analysis of Poly(vinyl Alcohol)–Iodine Complexes on the Basis of 2D X-ray Diffraction, Raman Spectra, and Computer Simulation Techniques

The crystal structures of the two types of iodine complexes (complex I and II) of poly(vinyl alcohol) (PVA), which were prepared respectively from the KI/I2 aqueous solution of middle (0.1–0.5 mol/L) and high (1–3 mol/L) concentration of I2, have been analyzed quantitatively on the basis of 2-dimensional X-ray diffraction diagrams and Raman spectral data in addition to the computer simulation method. In the crystal lattice of the original PVA, the PVA chains of zigzag conformation are packed together by intermolecular hydrogen bonds. Once the I3– ions migrate into the crystal lattice of PVA, these hydrogen bonds are deconstructed and the PVA chains are displaced from the original positions so that the I3– ions can be coupled together with the PVA chains through the charge-transfer between the I3– and hydroxyl groups, resulting in the formation of complex I. In this complex, the averaged occupancy of I3– ions is about 0.2, and the PVA–iodine pairs and the original PVA chain pairs coexist to form a kind of super lattice with the disordered packing structure of PVA chains and iodine ion columns. As the iodine concentration is increased furthermore, most of the PVA chains are combined with I3– ions at the occupancy of about 0.7 to create the complex II. The comparison of X-ray end diffraction patterns of the doubly oriented samples clarified the spatial relation of the crystal lattices between PVA, complex I and complex II. In the original PVA sample, the planar–zigzag planes of PVA chains are parallel to the rolled plane of the doubly oriented sample. This geometrical relation is kept in the complex I sample. However, in the complex II, the PVA chains have been found to rotate by 38° around the chain axis in the transition process from complex I to complex II. In this way, the change in the packing mode of PVA chains and iodine ions in the complex formation process has been successfully revealed for the first time from the atomic level.

Is perception of vertical impaired in individuals with chronic stroke with a history of ‘pushing’?

Post-stroke ‘pushing’ behaviour appears to be caused by impaired perception of vertical in the roll plane. While pushing behaviour typically resolves with stroke recovery, it is not known if misperception of vertical persists. The purpose of this study was to determine if perception of vertical is impaired amongst stroke survivors with a history of pushing behaviour. Fourteen individuals with chronic stroke (7 with history of pushing) and 10 age-matched healthy controls participated. Participants sat upright on a chair surrounded by a curved projection screen in a laboratory mounted on a motion base. Subjective visual vertical (SVV) was assessed using a 30 trial, forced-choice protocol. For each trial participants viewed a line projected on the screen and indicated if the line was tilted to the right or the left. For the subjective postural vertical (SPV), participants wore a blindfold and the motion base was tilted to the left or right by 10–20°. Participants were asked to adjust the angular movements of the motion base until they felt upright. SPV was not different between groups. SVV was significantly more biased towards the contralesional side for participants with history of pushing (−3.6±4.1°) than those without (−0.1±1.4°). Two individuals with history of pushing had SVV or SPV outside the maximum for healthy controls. Impaired vertical perception may persist in some individuals with prior post-stroke pushing, despite resolution of pushing behaviours, which could have consequences for functional mobility and falls.

Ipsilesional limb ataxia and truncal ipsipulsion in isolated infarction of the superior cerebellar peduncle

The clinical features of a lesion confined to the superior cerebellar peduncle (SCP) have not been defined well in human. A 92-year-old woman suddenly developed mild dysarthria and severe imbalance from an isolated unilateral SCP infarction, and examination showed ipsiversive ocular torsion, severe ipsilesional limb ataxia, and truncal ipsipulsion. These findings are well consistent with those observed in monkeys when the SCP was severed. In addition to the dentate-rubro-thalamic projections, the SCP appears to contain the fibers involved in the control of eye motion in the roll plane.