Increasing Plate Thickness Research Articles

Theoretical and numerical analysis of acoustic emission guided waves released during crack propagation

This article presents a theoretical and numerical analysis of guided wave released during an acoustic emission event using excitation potentials. Theoretical formulation showed that guided wave generated using excitation potentials follows the Rayleigh–Lamb equation. The numerical studies predict the out-of-plane displacement of acoustic emission guided wave on the plate surface at some distance away from the source. Parameter studies were performed to evaluate the effect of (1) pressure and shear potentials acting alone and in combination, (2) plate thickness, (3) source depth, (4) rise time, and (5) propagating distance away from the source. Numerical results showed that peak amplitude of S0 signal increases with increasing plate thickness, whereas the peak amplitude of A0 signal initially decreases and then increases with increasing plate thickness. Regarding the source depth, it was found that peak amplitude of S0 signal decreases and A0 signal increases with increasing source depth. Peak time showed a notable contribution to the low-frequency component of A0 signal. There were large losses in S0 and A0 peak signal amplitude over the propagation distance from 100 to 500 mm.

The Effect of Infill Steel Plate Thickness on the Cycle Behavior of Steel Plate Shear Walls

Steel plate shear wall (SPSW) is commonly used in civil schemes because of its good deformability and stiffness. In this research, the numerical analysis of steel plate shear wall (SPSW) with unstiffened infill steel plate is conducted. This paper explains the effect of thickness variation of infill steel plate on behavior of steel plate. In this status, several samples are designed and checked by rigid frame and actuator. The experimental samples is joined to a rigid frame. 3 numerical specimens consist of steel plate shear wall with different thickness (1.5, 3, 4. 5) mm formed by finite element code which is advanced by the Amirkabir university. To confirm the model, numerical results were discussed with a valid experiment which explain suitable agreement. Numerical model tested under cyclic loading with frequency of 1/60 Hz. Results show that the increase of infill steel plate thickness enhance stiffness and ductility ratio of model. And so, would decrease energy absorption in comparison with the reference model

Effects of Aspect Ratio and Plate Thickness on the Behavior of Unstiffened Steel-Plate Shear Walls with Pinned and Rigid Connections

Unstiffened steel plate shear walls (SPSWs) have been in use mostly in recent years. In this numerical study, the buckling behavior of a single-storey single-bay unstiffened SPSW with two pinned and rigid beam-column connections under lateral loading is investigated. The SPSW had different wall aspect ratios (L/h=1, 1.5, 2, 2.5, and 3) and infill plate thicknesses (tw= 3, 5, and 7 mm). Their effect on the buckling behavior of SPSW was examined using buckling analysis in ABAQUS software. Results indicated that with the increase of infill plate thickness, the lateral resistance of unstiffened SPSW system increases, but by increasing wall aspect ratio, its resistance decreases. In both connection designs, the model with L/h=1 (square-shaped model) showed better ductility and higher stiffness and strength in all three thicknesses. Maximum shear stress responses of SPSW models showed that in pinned design with L/h=1, the most change in shear stress values was 8% when infill plate thickness reached from 5 to 7 mm; while for rigid connection, it was reported as 7% when it increased from 3 to 5 mm. This indicates that in rigid connection, increasing the infill plate thickness has less effect on the increase of lateral resistance. By examining the performance of rigid and pinned beam-to-column connections with different wall aspect ratio and infill plate thickness, it was found out that maximum shear stress in rigid connection increased by 11% compared to pin connection. It was concluded that an optimum unstiffened SPSW model had a wall aspect ratio of 1 and infill plate thickness of 7 mm.

Delayed development of ossification centers in the tibia of prenatal and early postnatal MPS VII mice

Short stature is a characteristic feature of most of the mucopolysaccharidoses, a group of inherited lysosomal storage disorders caused by a single enzyme deficiency. MPS patients present with progressive skeletal defects from an early age, including short stature due to impaired cartilage-to-bone conversion (endochondral ossification). The aim of this study was to determine which murine MPS model best reproduces the bone length reduction phenotype of human MPS and use this model to determine the earliest developmental stage when disrupted endochondral ossification first appears. Gusmps/mps mice representing severe MPS VII displayed the greatest reduction in bone elongation and were chosen for histopathological analysis. Tibial development was assessed from E12.5 to 6 months of age. Chondrocytes in the region of the future primary ossification center became hypertrophic at a similar age to normal in the MPS VII mouse fetus, but a delay in bone deposition was observed with an approximate 1 day delay in the formation of the primary ossification centre. Likewise, chondrocytes in the region of the future secondary ossification center also became hypertrophic at the same age as normal in the MPS VII early postnatal mouse. Bone deposition in the secondary ossification centre was delayed by two days in the MPS VII proximal tibia (observed at postnatal day 14 (P14) compared to P12 in normal). The thickness of the tibial growth plate was larger in MPS VII mice from P9 onwards. Abnormal endochondral ossification starts in utero in MPS VII and worsens with age. It is characterized by a normal timeframe for chondrocyte hypertrophy but a delay in the subsequent deposition of bone in both the primary and secondary ossification centres, accompanied by an increase in growth plate thickness. This suggests that the signals for vascular invasion and bone deposition, some of which are derived from hypertrophic chondrocytes, are altered in MPS VII.

Fatigue Behavior Investigation and Stress Analysis for Rib-to-Deck Welded Joints in Orthotropic Steel Decks

The fatigue problems in orthotropic steel decks have raised widely concerns in recent years. This study focused on the root crack mechanism at rib-to-deck welded joints, based on the previous test results of sectional specimens and the matching FE analysis, the fatigue behaviors of structure detail were investigated by considering the effect of root gap shapes, weld penetrations, and plate thicknesses on crack initiation. Besides, various root crack depths were simulated in models to clarify the stress variations occurring during the propagation stage under cyclic loading. The results showed that the root gap shape and penetration rate have an impact on the root cracking direction and fatigue life at the initiation stage, but seem not directly related to the crack propagation mechanism; the higher penetration rate is advantageous for the prevention of root crack initiation. However, although the stiffness increased with the increase in plate thickness, the fatigue life of crack initiation might be reduced owing to the low fatigue strength of the thick deck plate, whereas the U-rib thickness has limited effect on the stress response of the root tip. Moreover, the significant difference between the 8 mm-crack model and other crack models is the high stress concentration around the crack tip. The stress conditions of root tip would be changed under loading cycles when a root crack propagated into half of deck plate thickness. Finally, the effect of structural dimensions on fatigue strength were also compared according to test results and FEA.

Experimental and model investigation on residual stresses in Q460GJ thick-walled I-shaped sections

Residual stresses can occur through a variety of mechanisms, and welding is one of mechanisms. This kind of stress variation through materials can be very complex and can vary between compressive and tensile stresses from layer to layer. A new type of high performance structural steel named by Q460GJ has been increasingly utilized in many large scale steel constructions in China, such as the National Stadium of China in Beijing (Birds Nest) and Canton Tower in Guangzhou. Q460GJ structural steel has a nominal yield strength of 460 MPa, which does not decrease significantly with the increase of steel plate thickness. Thus, Q460GJ structural steel is normally used in thick-walled welded sections. Nevertheless, the residual stresses on thick-walled sections may be more complex. Currently, only limited knowledge is available on the residual stress distribution of the members fabricated from high performance structural steel plates, especially for thick-walled sections. In this paper, the residual stresses in four welded medium-walled and four thick-walled H-section specimens fabricated from Q460GJ structural steel plates were studied by experimental tests. Residual stresses were measured by sectioning method, and the variation of residual stress through plate thickness was determined by slicing method. This study provides the magnitude and distribution of the longitudinal residual stresses. This paper also explores the effect of plate thickness on residual stress distribution and the interaction between flanges and webs. Finally, based on the statistical evaluation of the experimental results, a simplified multilayer residual stress model is proposed for predicting residual stress.

Study on The Effect Of Austempering Temperature On The Structure-Properties Of Thin Wall Austempered Ductile Iron

The Production of thin wall austempered ductile iron components can have strength-to-density ratios that approach those of cast aluminum, making it theoretically possible to apply austempered ductile iron in high strength light weight parts. Short term austempering treatment process was used to obtain thin wall austempered ductile iron castings. The samples of 2 and 3 mm thickness were austenitized at 900 °C for 30 minutes followed by holding at 350°C, 400°C and 450°C inoculated by Ce-Ca-Al-S-O-FeSi at 0.4% for 2, 5 and 10 minutes for each temperature. The austempered samples are comparatively harder than the as-cast ductile iron plates. The hardness also decreases with increase in austempering temperature for a given austempering time for thinner plates and for a thicker plates the hardness is more for the samples treated at 400°C than those treated at 350°C and 450°C for a given austempering time. The Yield strength and the ultimate tensile strength decreased for as-cast ductile iron and increased for thin wall austempered ductile iron samples with increase in plate thickness inoculated by Ce-Ca-Al-S-O-FeSi compare to Zr-Mn-Ca-Al-Ba-FeSi and Sr-Al-Ca-FeSi at 0.4%.

Dissimilar Joining with Aluminum Alloy Utilizing Thermal Expansion of CFRTP

The purpose of this study was to investigate the usefulness of dissimilar joining utilizing the property of expansion of the carbon fiber-reinforced thermo plastics (CFRTP) plate near the melting temperature of the matrix resin in the thickness direction. We developed a method to obtain joining strength by generating a force to push an Al piece from out of a groove potion by heating it provided with straight and tapered groove to an arbitrary temperature and then inserting CFRTP and expanding it. Experimental results and joining strength were evaluated. In addition, to confirm the relationship between the thermal expansion of CFRTP and the joining strength, the increase in plate thickness was examined when a CFRTP plate was sandwiched between two previously heated Al plates. Furthermore, to compare joining strength, the same test piece was adhered to the Al piece with epoxy adhesive and the joining strength was evaluated. As a result, a relationship between expansion due to the heating of CFRTP and joining strength was confirmed. Furthermore, by tapering the groove portion of the Al piece, almost the same joining strength as that when using adhesive was obtained.

Imaging and Dosimetric Consideration for Titanium Prosthesis Implanted within the Irradiated Region by Cobalt-60 Teletherapy Unit

The aim of this research is to observe dose distributions in the vicinity of titanium prosthetic implants during radiotherapy procedures on 60Co teletherapy machine, Prowess Panther treatment planning system (TPS). Data were obtained using a locally fabricated tissue equivalent phantom CT images with titanium prosthesis which was irradiated with 60Co gamma radiation. Prowess TPS (1.25 MeV) estimated less variations. Proximal ends of the metal recorded slight increase in doses as a result of backscatter with dose increment below acceptable tolerance of ±3%. Doses measured decreases on the distal side of the prosthesis at a distance less than dmax from the plate on each beam energy. The depth dose increases marginally after a certain depth level which generally originated from the unperturbed dose due to increase in the electron fluence. The percentage of depth doses decrease with the increase in plate thickness. A reduction in the above trend was also noticed with an increase in beam energy primarily because scattered photons are more forwardly directed. Prowess TPS (convolution superposition algorithm) was found to be better at reducing dose variation when correction for artifact. Manual calculations on blue phantom data agree with results from Prowess. This treatment system is capable of simulating dose around titanium prosthesis as its range of densities, 0.00121 to 2.83, excludes titanium density (rED for titanium is 3.74).

A non-classical model for an orthotropic Kirchhoff plate embedded in a viscoelastic medium

A non-classical model for an orthotropic Kirchhoff plate embedded in a viscoelastic medium is developed by using an extended version of the modified couple stress theory and a three-parameter foundation model. The equations of motion and the boundary conditions are simultaneously obtained through a variational formulation based on Hamilton’s principle. The new plate model contains three material length scale parameters to capture the microstructure effect, one damping coefficient to account for the viscoelastic damping effect, and two foundation moduli to represent the foundation effect. The current non-classical orthotropic plate model includes the isotropic plate model incorporating the microstructure effect and the classical elasticity-based orthotropic plate model as special cases. To illustrate the new model, the static bending and free vibration problems of a simply supported orthotropic plate are analytically solved by directly applying the general formulas derived. For the static bending problem, the numerical results reveal that the deflection of the simply supported plate predicted by the current model is smaller than that predicted by the classical model, and the difference is large when the plate thickness is small but diminishes as the thickness becomes large. For the free vibration problem, it is found that the natural frequency predicted by the new plate model with or without the foundation is higher than that predicted by the classical plate model, and the difference is significant for very thin plates. In addition, the damping ratio predicted by the new plate model is lower than that predicted by the classical plate model, and the difference is diminishing as the plate thickness increases. These predicted trends of the size effect at the micron scale agree with those observed experimentally. Furthermore, it is quantitatively shown that the presence of the foundation enlarges the plate natural frequency.

Shear performance of bolted side-plated reinforced concrete beams

Although the bolted side-plating (BSP) technique is feasible to upgrade the shear capacity of reinforced concrete (RC) beams, related studies on its strengthening effect have yet to be sufficient. Therefore, an experimental study of seven specimens was conducted to investigate the shear performance of BSP beams. The failure mode was found shifting from shear–tension to shear–compression after strengthening. The decrease of bolt spacing, the increase of plate breadth and thickness improved the shear capacity, stiffness and ductility effectively. Although the additional stiffeners improved the stiffness considerably, it exhibited no obvious improvement in the shear capacity and caused a serious reduction in ductility. Due to the shear deformation of bolt shaft and the tensile principal stress in the steel plates that was perpendicular to the main diagonal crack, uneven relative longitudinal and transverse slips existed on the interface between the bolted steel plates and the RC beams. An analytical model was developed according to the force equilibrium and deformation compatibility of the beam segment in the shear span. A design procedure, which can be conducted conveniently using ordinary computing software or even a calculator by structural engineers in their strengthening design practise, was also provided to estimate the shear bearing capacity of BSP beams.

Experimental and numerical investigations of a new U-shaped thin plate energy absorber subjected to bending and friction

To explore diversified energy absorption methods, a new energy absorption structure was proposed based on the plastic forming mechanisms of stamping in this paper. Through three repeated quasi-static tests, this new energy absorption structure was proven to be feasible. Moreover, the effects of thickness, friction coefficients and the fillet radius of the plates on the energy absorption of this structure were studied using a verified numerical simulation model. The results show that the structure has good test reproducibility and the deformation mode of the U-shaped plates is both stable and reliable. Stamping forces rise to an initial peak value with increasing stroke and then rapidly decrease to a steady-state force and consequently stabilize. The efficiencies of stamping forces in the three tests were greater than 80%. With increasing plate thickness and friction coefficient, the total energy absorption increased, whilst plastic energy was rarely affected by friction coefficient. The initial peak value of stamping force was sensitive to fillet radius changes of the U-shaped plates; when the fillet radius was larger than 8mm, stamping forces show an unobvious initial peak value. Steady-state force and energy distribution percentages were little impacted by the fillet radius of the plates. Furthermore, the steady-state force stabilized at around 100kN and the energy dissipation proportions of the plastic and friction energies were basically in equilibrium.

Paris Law-Based Approach to Fatigue Crack Growth in Notched Plates under Tension Loading

In this paper the crack path is studied for corner and surface flaws emanating from semicircular notch in plates of finite thickness subjected to cyclic tension loading. To this end, a numerical modeling was performed to evaluate the advance of the crack front on the basis of the Paris equation and the stress intensity factor solutions provided by Newman et al. Results show how the growing cracks tend towards a preferential propagation path. The convergence (closeness between crack propagation curves) is faster as the ratio of the notch radius to the plate thickness increases, and also quicker for corner cracks tan for surface flaws.

NUMERICAL AND EXPERIMENTAL BUCKLING ANALYSIS OF CRANE GIRDER

Generally structural components are subjected to Complex loadings in their working life. These structure must be capable of taking the desired load. Buckling is one of the important parameter which needs to be considered separately as it may cause the complete structure to fail. Plate buckling causes much problem in Bridge girder of EOT Crane; designers are increasing plate thickness of girder to avoid plate buckling which further increases the weight & cost of crane. But instead of increasing the plate thickness of compressed plate, its stability can be increased four times more by adding a suitable stiffener section along longitudinal direction which bisect the plate. Detail theory & example of plate buckling without stiffener & with stiffener is discussed. Manual & finite element analysis report for plate buckling is presented to reduce overall weight & cost of bridge girder of EOT Crane. Results obtained from finite element analysis, Manual calculations and Experimental analysis are compared & presented in table.

Analysis of Shear Banding in Zr-Based Metallic Glass under Laser Shock Peening and Bending

Metallic glasses have been expected to be used as structural materials since their high strength and high hardness. Unfortunately, their catastrophic brittle fracture behavior with poor plasticity becomes the major weakness for structural application. It has been recognized that the mechanism of plastic deformation in metallic glasses is through the formation of shear bands, which provide them with limited ductility. Laser shock peening (LSP) is an innovative surface treatment technique which can introduce deep compressive residual stress layer to materials for improving their mechanical behavior. In this work, a finite-element model has been developed to numerically simulate the pure bending process, LSP and subsequent bending process. An advanced constitutive equation was established based on the large deformation theory of nonlinear mechanics, the free volume model and the Coulomb-Mohr yield criterion. The model is able to capture the following results: (i) for a given bending deflection, the shear band spacing increases with increasing plate thickness; (ii) for a given plate thickness, the free volume increases with the bending deflection; (iii) for a given thickness and a given deflection, the shear bands increase under the effect of LSP.

Cone-beam computed tomography evaluation of dental, skeletal, and alveolar bone changes associated with bonded rapid maxillary expansion

Aims and Objectives: To evaluate skeletal changes in maxilla and its surrounding structures, changes in the maxillary dentition and maxillary alveolar bone changes produced by bonded rapid maxillary expansion (RME) using cone-beam computed tomography (CBCT). Materials and Methods: The sample consisted of 10 patients (6 males and 4 females) with age range 12 to 15 years treated with bonded RME. CBCT scans were performed at T1 (pretreatment) and at T2 (immediately after expansion) to evaluate the dental, skeletal, and alveolar bone changes. Results: RME treatment increased the overall skeletal parameters such as interorbital, zygomatic, nasal, and maxillary widths. Significant increases in buccal maxillary width was observed at first premolar, second premolar, and first molar level. There was a significant increase in arch width both on the palatal side and on the buccal side. Significant tipping of right and left maxillary first molars was seen. There were significant reductions in buccal bone plate thickness and increase in palatal bone plate thickness. Conclusions: Total expansion achieved with RME was a combination of dental, skeletal and alveolar bone changes. At the first molar level, 28.45% orthopedic, 16.03% alveolar bone bending, and 55.5% orthodontic changes were observed.

骨接合プレートにおける新しい締結方式の提案

An osteosynthesis plate is consisted of a plate and screws. It is a medical instrument to support the broken parts of bones. There are two types of the screws consisting the osteosynthesis plates. The one is a monoaxial screws and the other is a polyaxial one. The latter can be fixed at within a certain angle with the plate. By these screws, one can reposition the pieces of a broken bone to a mechanically and anatomically right position. However, the screws have problems of reduced fixing force and requirements of increased plate thickness. In this study, we aimed at the development of new mechanism of osteosynthesis plate. We devised a fixing method of tapping screws into the plate made of the same material. In the experiment, the angle of the screw was set to 15°. The screw was measured its fixing strength to the plate. As a result, we could show the fixing strength was equivalent to that of existing products.

A non-classical model for circular Kirchhoff plates incorporating microstructure and surface energy effects

A new non-classical model for circular Kirchhoff plates subjected to axisymmetric loading is developed using a modified couple stress theory, a surface elasticity theory and Hamilton’s principle. The equations of motion and boundary conditions are simultaneously obtained through a variational formulation. The new plate model contains a material length scale parameter to capture the microstructure effect and three surface elasticity constants to describe the surface energy effect. The current non-classical plate model includes the plate models considering the microstructure influence or the surface energy effect alone as special cases and recovers the classical elasticity-based Kirchhoff plate model when both the microstructure and surface energy effects are suppressed. To demonstrate the new model, the static bending problem of a clamped solid circular Kirchhoff plate subjected to a uniform normal load is analytically solved by directly applying the general formulas derived. The numerical results reveal that the deflection of the clamped circular plate predicted by the current Kirchhoff plate model is smaller than that predicted by the classical elasticity-based model, but the former approaches the latter with the increase of the plate thickness. It is also found that the difference between the plate deflection predicted by the model incorporating the surface energy effect and that predicted by the classical model is significant when the plate thickness is sufficiently small. However, the difference is diminishing as the plate thickness increases. These predicted size effects at the micron scale agree with the general trends observed in experiments.

Mechanical properties of F82H plates with different thicknesses

Fusion DEMO reactor requires over 11,000tons of reduced activation ferritic/martensitic steel and it is indispensable to develop the manufacturing technology for producing large-scale components of DEMO blanket with appropriate mechanical properties. This is because mechanical properties are generally degraded with increasing production volume. In this work, we focused mechanical properties of F82H–BA12 heat which was melted in a 20tons electric arc furnace. Plates with difference thicknesses from 18 to 100mmt were made from its ingot through forging and hot-rolling followed by heat treatments. Tensile and Charpy impact tests were then performed on plates focusing on their homogeneity and anisotropy. From the result, their homogeneity and anisotropy were not significant. No obvious differences were observed in tensile properties between the plates with different thicknesses. However, Charpy impact property changed with increasing plate thickness, i.e. the ductile brittle transition temperature of a 100mmt thick plate was higher than that of the other thinner plates.

An Overview on Effects of Geometric Parameters in Column Connection Behavior via Finite Element Method

Background/Objectives: In this research, behavior of column base with box-shaped column under static loads has been examined via finite element method. Methods/Statistical Analysis: Column connection to column base and column base connection to foundation have been modeled with details, and the behavior of connection in form of moment-curvature diagram has been displayed by changing the parameters including column base plate thickness, diameter of anchor rod, axial load, distance between anchor rods, eccentricity of the column in the direction y, x, connection behavior in form of moment-curvature diagram. Results: The results indicate that the more column base plate thickness increases, in addition to increasing ultimate resisting moment, joint stiffness in the elastic curve will increase. Further, by decreasing diameter of anchor rod, rigidity of connection will increases and the connection behavior will get close to the state of changing the rigid forms. By decreasing the distance between anchor rods, joint stiffness and ultimate moment resistance will increase and formation will decrease. Keywords: Anchor Rod, Column Base Plate, Finite Element Method, Moment-Curvature Diagram, Parametric Study