Increasing Tilt Angle Research Articles

Transmission of low-energy Cl<sup>–</sup> ions through Al<sub>2</sub>O<sub>3</sub> insulating nanocapillaries

<sec> The transmission of 10-keV Cl<sup>–</sup> ions through Al<sub>2</sub>O<sub>3</sub> insulating nanocapillaries is studied both by experiment and simulation. The double-peak structure in the transmitted angular distribution is found to be the same as our previous result. The peak around the direction of the primary beam is caused mainly by the directly transmitted Cl<sup>–</sup>, and the other peak around the tilt angle of Al<sub>2</sub>O<sub>3</sub> nanocapillaries is mainly induced by Cl<sup>+</sup> and Cl<sup>0</sup>. The intensity of transmitted Cl<sup>–</sup> decreases with the tilt angle increasing, which is in accord with the geometrically allowed transmission. Beyond the geometrically allowed angle, the transmitted projectiles are mainly Cl<sup>+</sup> ions and Cl<sup>0</sup> atoms. The ratio of transmitted Cl<sup>+</sup> ion to Cl<sup>0</sup> atom drops as tilt angle increases, and it turns more obvious when the tilt angle is larger than the limit of the geometrical transmission.</sec><sec> A detailed physics process was developed within Geometry and Tracking 4 (Geant4) to perform the trajectory simulation, in which the forces from the deposited charges and the image charges, the scattering from the surfaces as well as the charge exchange are taken into consideration. The transmissions at the tilt angle of 1.6<sup>o</sup> are simulated for the cases without and with deposited charges of –100 e/capillary. For the deposition charge quantity of –100 e/capillary, the majority of the transmitted projectiles are mainly the directly transmitted Cl<sup>–</sup> ions exiting to the direction of tilt angle, and the transmitted Cl<sup>0</sup> and Cl<sup>+ </sup>account for a very small portion. While for the case with no deposited charges, the simulation results agree well with the experimental results. The dependence of the scattering process on the tilt angle, which results in the different features in the transmitted projectiles, is studied in detail by the simulation. It is found that the transmitted Cl<sup>0</sup> atoms exit through single to multiple scattering, and most of transmitted Cl<sup>0</sup> atoms exit through single and double scattering, and are centered along the axis of nanocapillaries, while Cl<sup>+</sup> ions mainly exit by single scattering, which results in the fact that the intensity of the transmitted Cl<sup>0</sup> atoms drops slower than that of the transmitted Cl<sup>+</sup> ions with the increase of the tilt angle, leading the ratio of the transmitted Cl<sup>+</sup> to Cl<sup>0</sup> to decrease as the tilt angle increases in experiment. </sec> <sec> Our results describe the physical mechanism of low-energy ions through insulating nanocapillaries in detail, i.e. how the scattering process dominates the final transmission. It is found that the transmission of the negative ions in the energy range above 10 keV is caused by the scattering and the charge exchange process.</sec>

Heat transport behavior of bicrystal ZnO containing tilt grain boundary

Zinc oxide (ZnO), as a conventional semiconductor material, has excellent characteristics, such as piezoelectricity, photoelectricity, gas sensitivity, etc. With the improvement of nanopreparation technology, different types of nanostructrued ZnO compounds have appeared and their heat conductions have become a main research topic in nanodevices. In order to study the effects of grain boundary on the thermal properties of materials of this kind, bicrystal ZnO containing small-angle and high-angle grain boundaries are constructed by the embedded dislocation line and coincidence site lattice method. The variation of grain boundary energy with tilt angle is studied by the non-equilibrium molecular dynamics simulation. In addition, the dislocation density is calculated by using the Frank-Bilby formula. Our results show that the grain boundary energy and dislocation density increase with the increase of tilt angle in a small-angle region, and they tend to be stable in a high-angle region. The tilt angle of 36.86° is defined as the transition angle. The trend of the Kapitza resistance is the same as that of the grain boundary energy and satisfies the theoretical value from the extended Read-Shockley model. Furthermore, it is found that both the Kapitza resistance and thermal conductivity have a significant size effect. When the sample length is between 23.2 nm and 92.6 nm, the Kapitza resistance decreases sharply with the increase of the length and then tends to be stable. The thermal conductivity of the sample increases with length increasing, but is always less than that of the single crystal. At the same time, temperature is an important factor affecting the heat transport properties. The Kapitza resistance and thermal conductivity decrease with temperature increasing. At different temperatures, the Kapitza resistance of 38.94° grain boundary sample is greater than that of 5.45° grain boundary sample. In order to further explore the influence mechanism of grain boundary angle on heat conduction, the phonon state density of 5.45° and 38.94° grain boundary sample are calculated. The results indicate that the high-angle grain boundary has stronger scattering for acoustic branch phonons and the peak frequency becomes lower, whereas the optical branch ones have almost no effect on the heat conduction.

Magnetic motion of biogenic guanine crystal plate combined with Fe2O3 nanoparticles

To reduce the magnetic field amplitude required to orient guanine crystal plates, we have attached magnetic nanoparticles to these guanine crystal plates. Fe2O3 nanoparticles are mixed with the guanine crystal plates, which are dispersed in water. Observation by optical microscopy confirmed that the large particles, which are nanoparticle aggregates, attach preferentially to the side edges of the guanine crystal plates. The individual crystal plate surfaces show clear, undisturbed light interference patterns, which mean that each plate’s optical properties have been maintained. The magnetic orientation experiments of these guanine crystal plates with different numbers of optically observed particles are conducted under both in-plane and vertical magnetic fields. The positions of the attached particles do not change, even when the magnetic field is applied. In these experiment, it was difficult to align the crystal direction with the magnetic field direction because the magnetic orientation characteristics are strongly affected by the positions and numbers of the attached particles. However, in-plane rotation and an increased tilt angle are achieved for the guanine crystal plates using magnetic fields of several millitesla.

Influences of key process parameters on orbital forging of thin-walled smartphone shell frame of aluminum alloy

Smartphone shell frame is a thin-walled component, which is quite difficult to be fabricated by integral die forging process because of narrow die cavity and high forging load. In this paper, an orbital forging process is proposed to forge the thin-walled smartphone shell frame. Firstly, a FE model on orbital forging of thin-walled smartphone shell frame is developed under Deform-3D platform. By using this model, the influences of initial temperature of workpiece T, tilt angle of swing die γ and feed moment per rotation λ on temperature distribution, equivalent strain distribution and forging load are comprehensively discussed. The results show that final temperature of workpiece compared with initial temperature of workpiece T can be improved with decreasing initial temperature of workpiece T, increasing tilt angle of swing die γ and increasing feed moment per rotation λ. Equivalent strain is positively correlated with tilt angle of swing die γ, negatively correlated with feed moment per rotation λ and almost unaffected by initial temperature of workpiece T. Moreover, forging load can be obviously reduced by increasing initial temperature of workpiece T, increasing tilt angle of swing die γ and decreasing feed moment per rotation λ.

Simulations of transmission of 1 MeV protons through an insulating macrocapillary

We report the simulated results of 1 MeV protons transmitted through a straight insulating macrocapillary with a diameter of 0.8 mm and a length of 50 mm. In the simulations, the atomic scattering due to collisions with atoms in the capillary bulk and the guiding caused by the charge patch are both considered. The simulation results indicated a charge-up process in the macrocapillary, leading to a guided transmission. Some transmitted protons suffered significant energy losses due to the atomic scatterings. A temporal evolution of the transmitted proton fraction is shown. The fractions with the tilt angle can be well described by the exponential function . Altogether, the results reveal that the transmission of 1 MeV protons through a macrocapillary is determined by both the guiding and scattering. In the case of smaller angles, the MeV-ion transmission is mainly governed by the guiding. However, the scattering becomes more important as the tilt angle increases.

Study on the method of compensation for the heading effect of the rate offset frequency laser inertial measurement unit.

For the rate offset frequency laser inertial measurement unit (IMU), the errors of its three attitude angles, laser gyroscope, and accelerometer are coupled, which will affect the initial alignment result of the IMU and will make the measurement results of the IMU at different positions and angles deviate from the truth value. Meanwhile, with the increase of tilt angle, the heading effect becomes more obvious, and the error value is distributed positively cosine with the heading angle. In order to ensure the adaptability of the IMU to various operating conditions, it is necessary to compensate for the heading effect. The contribution of each error source of IMU to the heading effect is theoretically studied in this paper. We present a new method for compensating for the heading effect of the rate offset frequency laser IMU, in which the normal drift error of the vertical direction laser gyroscope and the zero bias error of the accelerometer under the turntable coordinate system are compensated. Based on the above method, simulation analysis and test verification are carried out. The experimental results show that the compensation method has a remarkable effect. In the case of two horizontal attitude angles tilted 0.0873 rad and 5 min initial alignment, the error of the rate offset frequency laser IMU reduced from 5.02E-04 rad $({3}\sigma)$(3σ) to 1.45E-04 rad $({3}\sigma)$(3σ), and the accuracy increased by 71%. High-precision initial alignment is achieved, which can meet the requirements of high-precision engineering applications.

Tomographic measurement of current density and heat input density for tilting TIG arc

ABSTRACT Heat source characteristics in the arc welding process such as temperature distribution of arc plasma, the current and heat input densities to the base metal is very important since they are one of the upstream factors of the process. Many studies have reported the distribution of temperature and metal vapour concentration in welding arc plasma by emission spectroscopy, and the distribution of heat input density to the base metal by split copper anode plate method. These studies generally require the axisymmetric assumption of the arc plasma. However, actual welding arcs are not limited as axisymmetric phenomenon. For example, tilted TIG arc welding is often performed due to the visibility and some reasons, resulting in a non-axisymmetric phenomenon in production sites. In order to measure such target, a tomographic approach is necessary. In this study, multidirectional measurement system with rotary split copper anodes was constructed to measure the non-axisymmetric distribution of the current and heat input densities of tilted TIG arc plasma. Integral values are measured from four directions and converted into a two-dimensional distribution by the image reconstruction method. It was experimentally revealed that as the tilting angle increases, the maximum value of current and heat input density decreases and the low density region of the distribution spreads towards the aiming direction. Although the measurement method using split anode including this study possesses the problem of arc deflection the insulating gap of split part, we found the fitting process on the measured data is useful to reduce this effect.

Effect of Tilt Angle and Pin Depth on Dissimilar Friction Stir Lap Welded Joints of Aluminum and Steel Alloys.

Automobile, aerospace, and shipbuilding industries are looking for lightweight materials for cost effective manufacturing which demands the welding of dissimilar alloy materials. In this study, the effect of tool rotational speed, welding speed, tilt angle, and pin depth on the weld joint were investigated. Aluminum 5052 and 304 stainless-steel alloys were joined by friction stir welding in a lap configuration. The design of the experiments was based on Taguchi’s orthogonal array for conducting the experiments with four factors and three levels for each factor. The microstructural analysis showed tunnel defects, micro voids, and cracks which formed with 0° and 1.5° tilt angles. The defects were eliminated when the tilt angle increased to 2.5° and a mixed stir zone was formed with intermetallic compounds. The presence of the intermetallic compounds increased with the increase in tilt angle and pin depth which further resulted in obtaining a defect-free weld. Hooks were formed on either side of the weld zone creating a mechanical link for the joint. A Vickers hardness value of HV 635.46 was achieved in the mixed stir zone with 1000 rpm, 20 mm/min, and 4.2 mm pin depth with a tilt angle of 2.5°, which increased by three times compared to the hardness of SS 304 steel. The maximum shear strength achieved with 800 rpm, 40 mm/min, and a 4.3 mm pin depth with a tilt angle of 2.5° was 3.18 kN.

Formation of functionally graded hybrid composite materials with Al2O3 and RHA reinforcements using friction stir process

ABSTRACT In the present investigation, hybrid aluminium based composite material was developed by using two dissimilar aluminium alloys with Al2O3 and RHA reinforcement particles via Friction Stir Process. Equally proportions of Al2O3 ceramic particles and RHA were used as filler (reinforcement) material in between the two aluminium plates (Al6063 and Al8011). Microstructures results showed a uniform distribution of reinforcement particles in between two aluminium alloys plates. The tensile strength of Al2O3 andRHAreinforced FGM composite is better for lower tool rotational speed i.e. 560 rpm but as the tool speed increases the tensile strength decreases. The least tensile strength can be observed for 1460 rpm. The tensile strength reduces with the increase in tilt angle. The tensile strength is better for triangular tool shape but continuously decreases with the smoothness of the tool. However, the hardness of Al2O3 and RHAreinforced FGM composite is better for the triangular tool shape and minimum tool speed i.e. 560 rpm but as the smoothness of the tool increases the hardness decreases. The least hardness can be observed for the circular tool. The hardness decreases as the tool angle increases. The better hardness can be seen for minimum tool angle i.e. 00.

Operational range of a ferrofluid pocket bearing

Ferrofluid pocket bearings are interesting for fast and precise positioning systems thank to the absence of stick-slip, the low viscous friction and their cost-effective nature. However, the characteristics of the bearing change due to over(de)compression since air escapes out of the enclosed pocket. This article presents an experimentally validated model that includes the air mass inside the pocket in the calculation of the equilibrium position of the ferrofluid bearing. Moreover, a simple and efficient way to obtain the operational range of the bearing is presented and a sensitivity analysis was performed. The sensitivity analysis showed that ferrofluid pocket bearings are always self-aligning and that the tilt stiffness increases when the fly height decreases or the tilt angle increases.

Effect of column inclination and oscillation on liquid spreading in a trickle bed

Gas–liquid–solid flow in a trickle bed installed on a floating production unit is affected by oscillations imparted by sea waves. The oscillations may affect the spreading of liquid, and in turn, the performance of a reactor. The present work investigates the effect of bed inclination and two types of oscillations (roll and roll+pitch) on the spreading of liquid in a cylindrical trickle bed with a single point liquid injection by using computational fluid dynamics. In the simulations, column tilt varied in a range of 0–15° and three oscillation frequencies (0.1, 0.2 and 0.5Hz) were considered. Initially, a three-phase Eulerian model was validated using the published experimental data for a stationary column. The effect of closure models such as capillary pressure model and Ergun drag model constants on predictions was analyzed for the selection of these closures. In a tilted column, liquid was pushed to flow in the direction of tilt. Increase in tilt angle from 0 to 15° resulted in increase in the flow segregation and ∼20% reduction in pressure drop. Oscillations (both roll and roll+pitch) resulted in more uniform liquid spreading and higher liquid holdup compared to a vertical column. With decrease in oscillation frequency, the index of uniformity in the radial liquid distribution further increased. The higher uniformity and liquid holdup caused by oscillations can be attributed to higher radial velocity of liquid due to the effect of gravity in the radial direction. Compared to the roll type oscillations, the roll+pitch type resulted in higher radial velocity and radial distribution of liquid.

Tracer dispersion in trickle beds under tilts and roll motions – CFD study and experimental validation

A wire-mesh sensor was used to measure the liquid residence time distribution (RTD) and tracer dispersion in trickle beds subjected to stationary tilts and roll motions. The measured tracer characteristics were confronted to three-dimensional transient Euler-Euler CFD simulations to expose the role of inclined and oscillating porous media. The simulation results satisfactorily reproduced the widening tracer signals with increased bed inclination reflecting in asymmetric RTDs prompted by permanent gravity-driven stratified flow zone through the packing. Similarly, tracer dispersion was predicted to increase for rolling beds by increasing tilt angle and motion period. While an increase of tilt angle shortened RTD breakthrough time due to the faster tracer stream evolving in the liquid-rich lower-most zones, tracer elution tended to slow-down with increasing the rolling period. In addition, it was revealed that with altering the column angular position during roll motions the fluid flow structures inevitably varied inside the packing leading to different mixing behaviors and residence time distributions.

Numerical research on jet tab thrust vector nozzle aerodynamic characteristics

Jet tab thrust vector nozzle is a unique kind of thrust vector device which generates control force by inserting tab into the nozzle exhaust. The influence of tab geometric parameters on the nozzle aerodynamic characteristics is not clear. In order to meet the requirements of control rate modeling and optimization of jet tab thrust vector control system, a computational study was conducted to investigate the effects of tab geometric parameters which include insertion height, width, axial distance, incline angle on nozzle aerodynamic characteristics. The flow structure of nozzle with different tabs are demonstrated, and thrust vector performance is evaluated. Results indicate that the lateral force coefficient and the thrust loss coefficient increased with the increase of the tab insertion height, the thrust vector efficiency decreased as the insertion height increased; increasing tab width increased the thrust vector efficiency, the thrust vector efficiency increased by 24.8% when the tab width increased form 10mm to 18mm; both increasing axial distance and increasing tilt angle decreased the lateral force and efficiency, in practical application, the axial position and incline angle should be minimized.

A biomechanical investigation of the retentive force of pedicle screw structures for different screw tulip designs

BackgroundPedicle screw based spinal fixation systems have been widely used for treating a variety of spinal diseases. The retentive force is an important factor that determines structural stability. The screw tulip design and the magnitude of nut tightening torque influence the retentive force. This study investigated the influences of varied tilt angles between the shaft-rod interface and varied nut tightening torques on the retentive force of the monoaxial, polyaxial, and uniplanar screws. MethodsThree types of tulip constructs were biomechanically tested. Two parameters that affect the retentive force include the tilt angle and the nut tightening torque. The retentive force was investigated by an axial gripping capacity test and axial torque gripping capacity test. FindingAmong all combinations of screw designs and tilt angles, the 12 Nm nut tightening torque offered a greater retentive force than the 8 Nm, except for monoaxial screws with a 0 degree tilt angle. For monoaxial screws, the retentive force was negatively correlated with increasing tilt angles. For polyaxial and uniplanar screws, the retentive forces remained constant with increasing tilt angles. InterpretationIn monoaxial screws, when the axis of the shaft isn't perpendicular to the axis of the rod, a gap is formed between the tulip-rod interface. This results in a decreased retentive force. In polyaxial and uniplanar screws, the contact surfaces were the same in different tilt angles, therefore, the retentive force remained constant, which was attributed to the adjustable tulips always being perpendicular to the axis of the rods.

Non-spherical single cone bit tooth failure analysis and tooth load test

Single cone bit is frequently used in slim-hole drilling field. To solve the problems of the spherical single cone bit during drilling process, a new type of single cone bit is designed, and field test is carried out. In this paper, the statistical analysis of tooth wear is done, and the causes of cutting tooth wear and protects radial tooth eccentric wear are analyzed in detail. In order to figure out the causes of tooth failure, the tooth load of non-spherical single cone bit was measured by experiment method and the change regularity of tooth load was statistically analyzed. The results show that the axial load is greater than the tangential load and radial load during drilling process. The axial load increase is more obvious with increase of weight on bit (WOB), but the tangential load and radial load change less. With increase of axle tilt angle of bit axis, the axial load and tangential load is reduced at the end of cone, but the radial load is increase. However, the axial load, tangential load and radial load of other's tooth is increase with increase of axle tilt angle of bit axis. The experiment results explained the cause of tooth wear, and it was important to understand the mechanism of tooth wear, optimize the structure parameters of bit, and understand the movement of bit in the well.

How anterior pelvic tilt affects the lower extremity kinematics during the late swing phase in soccer players while running: A time series analysis

Anterior pelvic tilt has been proposed to predispose the hamstring in soccer players to injury at the late swing phase during a sprint, however the mechanism on how the changes in the alignment would affect the kinematics are still unclear. Thirty-four male amateur soccer players were recruited for this study. Pelvic tilt was measured using the DIERS Formetric 4D. Lower extremity angles were recorded using an 8-camera Vicon motion capture system at 200 Hz while the athlete performed a high speed run on a motorised treadmill. Late swing phase was extracted from 5 running cycle which were later analysed using statistical parametric mapping (SPM). The results show that the increase of anterior pelvic tilt angle was significantly correlated with hip (r = −0.421 to −0.462, p = 0.015) and knee flexion (r = −0.424 to −0.472, p = 0.026) values. No other correlation was found between the anterior pelvic tilt and the angles at the coronal plane. By using time series analysis it was shown that the anterior pelvic tilt measured in a standing position would affect the adjacent segments’ kinematics while running as suggested in the kinetic chain theory; which would potentially predispose the soccer athletes to hamstring injury by maintaining knee extension.

Effect of orientation on the directional and hemispherical emissivity of hyperbolic metamaterials

We investigate the spectral directional and hemispherical emissivity of hyperbolic metamaterials with arbitrary orientation of the optic axis. The 4 × 4 matrix method is combined with coordinate rotational transforms to circumvent projection operations. The two hyperbolic bands of hexagonal boron nitride (hBN) are examined in detail to elucidate the influence of the orientation of the optic axis on the emissivities for both transverse magnetic (TM) and transverse electric (TE) waves. The results show that the orientation of the optic axis can greatly affect the hemispherical emissivity in the two hyperbolic bands of hBN. The directional emissivity varies periodically with the azimuthal angle when TM and TE waves are coupled, resulting in conversion of polarization in the medium. For both TM and TE waves, the matching of impedance and admittance at the surface of the material is better for smaller tilting angle in the type I hyperbolic band, but the opposite is true in type II hyperbolic band where the matching becomes better for larger tilting angles. As the tilting angle increases, the hemispherical emissivity decreases in the type I hyperbolic band but increases in the type II hyperbolic band. Our conclusions can be extended to other hyperbolic materials. Therefore, this work may provide valuable guidance on characterization, measurement and tailoring of the directional and hemispherical emissivity for hBN and other hyperbolic materials with arbitrary orientation and application of such materials for manipulation of radiative heat transfer.

Optimal Safe Layout of Fuel Storage Tanks Exposed to Pool Fire: One Dimensional Deterministic Modelling Approach

Fire hazard is one of the main risks associated to fuel storage tanks in petroleum and in the petrochemical industries. Such a hazard includes pool fires in the storage tanks or in the bunds, fire propagation from the source tank to target tanks both in absence and in presence of wind, and also the cascading/domino effect due to confined and unconfined vapour cloud explosion and or BLEVE associated with the source tank. In the present work, a radiation shield of flowing water has been introduced at a distance from the source fuel storage tank to prevent the domino effect originating from this source tank, under fire, to the target fuel storage tanks in a tank farm. A simple one dimensional model has been developed from the steady state energy balance to simulate the safe distances (i.e. rim–rim distance) between fuel storage tanks containing class-I fuel (e.g. gasoline), both in presence and absence of a water-shield under no-wind and cross-wind conditions. The model predictions have shown that the maximum safe inter-tank separation distance of 28.42 m is anticipated at a wind velocity of 6 m/s, compared to 16.34 m in no-wind condition, beyond which the centroid of the parallelepiped (a solid-flame geometry) falls outside the base of the tilted flame geometry causing flattening of flame and a very sluggish increase in the flame tilt angle as the inverse of the Richardson number in the presence of wind velocity vector increases. Furthermore, the present one dimensional mathematical model has also been extended to show that introduction of a water-shield with an appropriate thickness (δopt) is able to prevent the propagation of radiation heat flux under both no-wind and cross-wind conditions to a much lower distance close to 8.34 m between tanks (measured from the centre of the source tank), than those predicted from the existing empirical models; viz. Point Source model and Shokrie-Beyler’s model.

Radial breathing modes coupling in plasmonic molecules.

Metallic hexamer, very much the plasmonic analog of benzene molecule, provides an ideal platform to mimic modes coupling and hybridization in molecular systems. To demonstrate this, we present a detailed study on radial breathing mode (RBM) coupling in a plasmonic dual-hexamers. We excite RBMs of hexamers by symmetrically matching the polarization state of the illumination with the distribution of electric dipole moments of the dual-hexamer. It is found that the RBM coupling exhibits a nonexponential decay when the inter-hexamer separation is increased, owing to the dark mode nature of RBM. When the outer hexamer is subjected to the in-plane twisting, resonant wavelengths of two coupled RBMs as well as the coupling constant show cosine variations with the twist angle, indicating the symmetry of hexamer structure plays a critical role in the coupling of RBMs. Moreover, it is demonstrated that the coupling of RBMs is dominated by the in-plane interaction as the outer hexamer is under an out-of-plane tilting, causing convergence of resonant wavelengths of the two coupled RBMs with increasing tilt angle. Our results not only provide an insight into the plasmonic RBM coupling mechanism, but also pave the way to systematically control the spectral response of plasmonic molecules.

Tilt strain glass in Sr and Nb co-doped LaAlO3 ceramics

Strain glass, a glassy state of lattice strain, has been found in Ti50-xNi50+x alloys and later in many metallic ferroelastic/martensitic systems, where shear or shuffle serves as a primary order parameter (POP). Another class of non-metallic ferroelastic ceramics are also known to widely exist and commonly possess a polyhedral tilt as the POP. So far, it is unclear whether a “tilt” strain glass exists. Here, we report a finding of a tilt strain glass in La1-xSrxAl0.95Nb0.05O3-δ ceramics. With increasing Sr2+ dopants, the ferroelastic transition from cubic to rhombohedral phases is gradually suppressed. At a critical concentration (xc ∼10%), a strain glass transition emerges, characterized by five sets of evidence: (I) an invariance of average structure; (II) frequency dependence of elastic moduli at a strain glass transition temperature Tg; (III) non-ergodicity; (IV) formation of rhombohedral nanodomains; (V) a gradual increase of tilt angle upon cooling. Surprisingly, the established phase diagram shows an increase of Tg with increasing dopants (a positive correlation), which is different from previous strain glass phase diagrams. The positive and negative correlations can be explained as a balance between two factors of strain glass transition: a global transition factor producing a negative contribution competes with a local field one producing a positive contribution. Our discovery of strain glass in ceramics may also bring novel properties as in metals.