Steel Band Research Articles

Study of the formation of adiabatic shear bands in steel during impact

Both metals and other materials may exhibit the formation of narrow bands of extreme strains when impacted at high strain rates and large strains. These are known as Adiabatic Shear Bands (ASBs). They are observed during material processing such as forging and machining as well as wear and in armor plates during impact by projectiles. The prevailing theory for their formation is that they form in narrow bands because of two competing mechanisms occurring sequentially: strain hardening followed by thermal softening from the retained heat due to the impact. However, recent studies suggest that the formation of ASBs may be a simultaneous occurrence of different mechanisms which starts with the emergence of dislocations depending on the imposed local strain and strain rate. This study uses different methodologies to explore the microstructure of ASBs in a hardened low alloy steel. The study includes the effect of the initial microstructure on the formation of ASBs. The Focused Ion Beam technique was used to prepare transmission electron microscopy samples from regions within the shear bands to eliminate the induced further deformation which could be produced by conventional approaches of electropolishing. The present study reveals that each of these methodologies complements each other. Also more complex series of mechanisms including dislocation cell formation, texture development, dynamic recrystallization and carbide dissolution accommodate the excessive strains that occur during the evolution of the shear bands.

The evolution of bonding in orthodontics.

In the early days of fixed-appliance orthodontic treatment, brackets were welded to gold or stainless steel bands. Before treatment, the orthodontist had to create enough space around each tooth to accommodate the bands, and then those spaces had to be closed at the end of treatment, when the bands were removed. This was time-consuming for the orthodontist and uncomfortable for the patient. Banded appliances frequently caused gingival trauma when fitted, and decalcification could occur under the band. In the mid-1960s, Dr George Newman, an orthodontist in Orange, New Jersey, and Professor Fujio Miura, chair of the Department of Orthodontics at Tokyo Medical and Dental University in Japan, pioneered the bonding of orthodontic brackets to enamel. Many developments have occurred in the decades that followed, including many new adhesives, sophisticated base designs, new bracket materials, faster or more efficient curing methods, self-etching primers, fluoride-releasing agents, and sealants. The purpose of this article is to review the history of orthodontic bonding, especially the materials used in the bonding process.

Development of Spot Welding Steel Band Packing System

Development of Spot Welding Steel Band Packing System

Microstructural stability of ODS steels in cyclic loading

AbstractThe remarkable microstructural stability of high chromium steels prepared by powder metallurgy and strengthened by dispersion of nanometric yttrium oxides in cyclic loading at high temperatures is reported. Contrary to the continuous cyclic softening and profound changes in the microstructure during fatigue of common high chromium steels, the addition of 0.3 wt% Y2O3 stabilizes the microstructure and significantly reduces cyclic softening of investigated steels. The evolution of microstructure as a result of fatigue loading at room temperature, 650 and 750 °C, was examined by means of transmission electron microscopy. Only minor changes in the microstructure were detected. The stability of oxide particles after high‐temperature exposure was confirmed by energy dispersion spectroscopy chemical analysis. The microstructural features are discussed in relation to the cyclic behaviour of the oxide dispersion strengthened steels. The analysis of the hysteresis loop indicates that oxide nanoclusters are intersected and dissolved in slip bands of ODS Eurofer steel. This process contributes to cyclic softening.

Dowel Type Joints of Round Timber Exposed to Static and Cyclic Tension Forces

Timber constructions made of round timber are becoming increasingly popular nowadays. They concern both non-pedestrian and pedestrian bridges, watchtowers and playground equipment. If these constructions are designed with a truss supporting system, the element joints are often made of bolts with slotted-in steel plates. Joints in round timber do not have sufficient support in existing Eurocodes. The problem is also in the characterization of cyclically loaded round timber joints (fatigue loading in wood). The aim of this paper is to present the results of static and dynamic tensile tests of round timber bolted joints with slotted – in steel plates along the grains. Some of these round timber joints samples were reinforced in the timber part (near the bolt) with different components (screws, special washers, steel bands, performed steel plates and nails). The main reason of the reinforcing of the joints was to increase the carrying capacity and safety of these joints in tension. Based on the results of static and dynamic round timber bolted joints tests, reinforcement of the bolted joints significantly increased joint carrying capacity and reliability.

Detailed characterization of complex banding in air-cooled bainitic steels

The presence of banding in a hot-rolled air-cooled bainitic steel has been thoroughly characterized. The banded microstructure was observed due to distinctive sensitivities to the etching agent. Microstructural and crystallographic studies by means of Scanning Electron Microscopy and Electron Backscatter Diffraction did not reveal any substantial differences between bands and matrix. However, solute segregation of some alloying elements was detected by Wavelength- Dispersive Spectroscopy, being found that bands are enriched in Cr, Mo and Si and depleted in Mn. Finally, a set of theoretical calculations suggested that the solidification mode is responsible for such unusual partitioning behavior, which is beneficial in terms of the bainitic transformation.

Clinical comparison of various esthetic restorative options for coronal build-up of primary anterior teeth.

This study was designed to compare the clinical performance of composite, strip crowns, biological restoration, and composite with stainless steel band when used for the coronal build-up of anterior teeth. A total of 20 patients aged 3-6 years presenting with mutilated primary anterior teeth due to caries or trauma were selected for the study using randomized simple sampling. A total of 52 primary anterior teeth were randomly divided into four equal groups having 13 teeth in each group. Teeth in Group I were restored with composite, in Group II with strip crowns, in Group III with biologic restoration and with stainless steel band reinforced composite in group IV. The restorations were evaluated for color match, retention, surface texture, and anatomic form according to Ryge's Direct (US Public Health Service) evaluation criteria at baseline (immediate postoperative), after 48 h, 3, 6, and 9 months. The data obtained were statistically analyzed using Chi-square test, and level of significance, that is, P value was determined. At baseline, none of the groups showed any color changes. Other than Group III all other groups showed highly significant changes (P < 0.05) in color after 3 months. Loss of retention was seen in both Groups I and IV after 3 months. After 6 months, retention loss was seen in all the groups except Group II, in which loss was seen after 9 months (P > 0.05). Deterioration in surface texture was exhibited maximum by restorations in Group IV followed by Group I at 3 months. Whereas, no surface changes were seen in Group II and III. Only Group I and IV showed discontinuity in anatomic form after 3 months. After 6 months, except in Group II, discontinuity in anatomic form was observed in all the groups. Discontinuity in anatomic form was seen in all the 4 groups after 9 months although the difference was not significant (P > 0.05). Biological restoration was found to be most satisfying esthetically owing to color compatibility with the patient's tooth. Thus, it has a great potential to be used as esthetic restorative option in primary anteriors.

Self-organization of adiabatic shear bands in OFHC copper and HY-100 steel

We study the self-organization process of adiabatic shear bands in OFHC copper and HY-100 steel taking into account strain hardening factor. Starting from mathematical model we present a new numerical approach, which is based on Courant–Isaacson–Rees scheme, that allows one to simulate fully localized plastic flow. To prove the accuracy and efficiency of the following method we give solutions of two benchmark problems. Next we apply the proposed method to investigate such quantitative characteristics of self-organization process of ASB as average stress, temperature, localization time and distance between ASB. Then we compare the obtained results with theoretical predictions by other authors.

Research Precast Fool Slab of Massonry Building Roof Reinforcement Methods

Most of the existing building floor roof of brick structure is precast floor slab structures, which structural integrity is not good. In the earthquake, the floor is easy to fall off from the wall, causing casualties and economic losses. Vertical bearing capacity of precast floor slab are usually able to meet the requirements. In most cases the floors have been fall off from the wall before the floors were damaged, Stability of the outer plane of the floor itself to be adequate.By analyzing the patterns and characteristics of precast floor slabs crack under seismic force often appear, this paper presents that the prefabricated floor flat overall reinforcement scheme, which the application of steel band with end portion of the floor a holistic reinforcement,and finite element software ABAQUS be counted cases,the integrity of the reinforced floor to achieve significant improvement, and maximum allowable displacement can be controlled within a limited value.

Reinforcement Possibilities of Round Timber Bolted Joints

In this article the results of round timber bolted joints with inserted steel plates tests are presented. First, unreinforced round timber specimens were tested. Mechanical reinforcement by using modified washers, steel bands, BOVA plates and boost with screws of round timber specimens based on test result was then proposed. Reinforced specimens of various densities were then tested and rate of improvement in tensile strength was established for each of five proposed reinforcement methods. Tests were carried out on EU100 pressure machine in Faculty of Civil Engineering of VŠB-TUO Ostrava.

Buckling of Masts of Bamboos Bundles

Bamboos generally have elasticity module in compression of about 9 GPa, which is a relatively low value compared to timber and concrete, 20 GPa, and steel, 200 GPa. However, the compressive strength is high - 40 to 80 MPa – that, combined with axissimetria of the cross section, makes the bamboos structural elements with high strength and flexibility. Considering the low apparent specific weight of the material 8 kN/m3, photosynthetic production and workability, bamboos have no competitor in the market so that loads can be absorbed independently by any of the above materials. But the industrial structural elements may be produced with dimensions and geometries provided in accordance with the load to be transported. This is not the case of bamboo. Thus, the capacity of the bamboo in compression becomes limited by its natural flexural rigidity, EI. Thus, different structural systems with pipe threads to make large columns or masts were investigated, [1,2], all with bamboo Phyllostachys pubescens species. In this paper, a kind of mast composed of a central bamboo 6 m in length and six smaller segments axi-symmetrically distributed around this central bamboo will be presented. This proposed design is organizationally a set of bars shackled by steel bands along the length of the beam. Flexion-compression tests with bamboo species Phyllostachys pubescens, combined with numerical modeling through the MEF were made. The loading capacity was tripled and the lateral deviations are negligible when compared with the axial bamboo tested alone. This mast, while consuming a relatively high number of bamboo units, has the advantages of ease and constructive possibility of structural use of smaller diameter bamboo. All the design and results of experimental and numerical analyzes will be discussed in this paper.

Biomex Quad Helix

Introduction: Anterior deep bite with narrow maxillary arch is a most common clinical situation orthodontists have to deal with in Class I as well as Class II malocclusions.Objective: To present a modification of the quad helix appliance which incorporates acrylic anterior bite plane for simultaneous bite opening with maxillary expansion (Biomex Quad helix). Appliance design: The appliance is made of 0.036 inch stainless steel wire. The anterior bridge of the quad helix is modified by extending it anteriorly. The wire is soldered to the stainless steel bands on the maxillary first permanent molars. Acrylic anterior bite plane is added to this anterior extension keeping the anterior helices exposed. It combines advantages of a quad helix with that of anterior bite plane. Hence it can be useful for simultaneous bite opening with maxillary expansion, deprogramming, and relieving TMJ symptoms by unlocking the occlusion.Conclusion: Biomex Quad Helix is a versatile appliance which is simple in design, easy to fabricate, comfortable for the patient, and economical for the operator and the patient.

A Survey Study of U.S. Collegiate and K–12 Steel Band Directors’ Attitudes Relating to Steel Band Curriculum and Pedagogy

Steel bands were introduced into U.S. schools and universities during the 1950s and 1960s. There are now more than 600 U.S. school and university steel bands. The range of teaching methods and repertoire choices must be examined to more fully understand the variety of steel band traditions present in K–12 schools and universities. U.S. steel band directors responded to Likert-type, yes/no, and open-ended items about their curriculum and pedagogy as part of a March 2012 survey ( N = 216). Some of the main issues examined include methodology, the balance of genres programmed, the inclusion of contextual information, and directors’ steelpan performance backgrounds. Recommendations for the field, including suggestions for professional development opportunities for steel band directors, are included.

Use of ultrasonic back-reflection intensity for predicting the onset of crack growth due to low-cycle fatigue in stainless steel under block loading

The present study proposes the use of ultrasonic back-reflected waves for evaluating low cycle fatigue crack growth from persistent slip bands (PSBs) of stainless steel under block loading. Fatigue under high-low block loading changes the back-reflected intensity of the ultrasonic wave that emanates from the surface. Measuring the change in ultrasonic intensity can predict the start of crack growth with reasonable accuracy. The present study also proposes a modified constant cumulative plastic strain method and a PSB damage evolution model to predict the onset of crack growth under block loads.

Analysis of the Quality of the Weld Metal Obtained with Alloyed Flux-Cored Wire

Abstract. The main aim of this paper is to assess the quality of newly produced, alloyed flux-cored wire with increased thickness of the steel cover compared to traditional according to AWS A5.29 standard, alloyed with Ni and Mo, and designed for welding of fine-grained HSLA steel. Flux-cored wire was produced on a pilot production line that allows calibration of steel band of higher thickness and production of flux-cored wire. Quality assessment of the alloyed flux-cored wire was based on the analysis of the results of tests of mechanical properties and microstructure mainly of the weld metal. Variation of chemical composition and microstructure were analyzed along weld metal (for each welding pass) and heat affected zone (HAZ) using SEM and EDS. Based on the results of the quality assessment of flux-cored wire, the conclusions about the feasibility of industrial application of selected metallurgical grade of flux-cored wire designed for welding of fine-grain HSLA steel were presented.

The formation of radiation-induced segregation at twin bands in ion-irradiated austenitic stainless steel

Radiation-induced segregation (RIS) at twins was investigated using transmission electron microscopy (TEM) for ion-irradiated austenitic stainless steel. Significant RIS was found to occur at twin boundaries. TEM analysis indicates that interfacial dislocations at partially coherent twin boundaries are potential sites for strong RIS phenomenon. The RIS causes the formation of thin bands having a higher Ni and lower Cr concentration in twin bands with a width less than 15nm. In wider twin bands, strong RIS occurs only at the outer twin boundaries, but not inside the band. The possible mechanism for the formation of the RIS thin band is discussed.

Active confinement of weakened concrete columns

This paper investigates the advantages of using of external active confinement to improve the compression load capacity of concrete cylinders using mild steel band clamps. For this, passive and actively pre-stressed steel bands have been attached to concrete cylinders to mimic real structural columns which may otherwise have to be removed and replaced due to poor strength performance. The experimental programme included compression load testing a number of unreinforced concrete cylindrical specimens to establish the effect the confinement had on the compressive load-carrying capacity and the stress–strain behaviour. A number of parameters were investigated in the study including the effect of varying the band spacing, volumetric ratio and passive and active confining forces. It was found that confining the concrete did produce an increase in compressive strength. However, the different levels of pre-stress used had no significant effect on strength but did influence the confined concrete stress–strain behaviour with greater lateral stresses at peak strength observed. Ductility increases were observed for confined specimens and significant axial strains achieved with noticeable peak strength enhancements. However, due to initial misfit between the bands and the concrete in the passive confinement state, confining forces generated only contained the cracked specimens. The actively pre-stressing confinement yielded an increase in load capacity of 53 % as the bands were fully activated.

An EBSD investigation on deformation-induced shear bands in a low nickel austenitic stainless steel under controlled shock-loading conditions

Adiabatic shear band is an important materials phenomenon often observed in metals when processed at high strain rates. The mechanical responses and microstructure evolution in it attract strong interests from the scientists of materials science and engineering. We report the results of the microstructure characteristic of a 200 series Fe–Cr–Ni austenitic stainless steel with low nickel contents deformed at high strain rates (about 5.8×105s−1) by a split Hopkinson pressure bar. The hat shaped specimens are used to induce the formation of the adiabatic shear bands under shock-loading tests. The microstructure and microtexture of the shear band in a 200 series Fe–Cr–Ni austenitic stainless steel are investigated by means of optical micrograph electron backscatter diffraction. The shear bands can be generated at about 78μs after the true flow stress reaches the value about 923MPa. The grains in the boundary of the shear band are elongated along the shear direction, and the core of the shear band consists of ultrafine equiaxed grains with diameter 0.1–0.3μm and low dislocation density. According to the orientation distribution, the microtexture peaked at (45°, 65°, 0°) in the matrix slightly shifts towards the recrystallization microtexture (60°, 60°, 0°) in the shear band center, and the grain boundaries in the shear band are geometrical necessary boundaries with high-angles. Calculations of temperature rise about 943K suggest that the temperature in the shear band is above the recrystallization point. Finally, the grain refinement in an adiabatic shear band in the 200 series Fe–Cr–Ni austenitic stainless steel is described as a consequence of the rotational dynamic recrystallization.

Modification of Banding in Dual-Phase Steels via Thermal Processing

The potential to utilize controlled thermal processing to minimize banding in a DP780 steel with 2 wt pct Mn was evaluated on samples processed on a Gleeble® 3500 thermomechanical processing simulator. All processing histories were selected to result in final dual-phase steel microstructures simulating microstructures achievable during annealing of initially cold rolled sheet. Strip samples were processed to evaluate the effects of heating rate, annealing time, annealing temperature, and cooling rate. The degree of banding in the final microstructures was evaluated with standard light optical microscopic techniques. Results are presented to illustrate that the extent of banding depended on control of both heating and cooling rates, and a specific processing history based on a two-stage heating rate can be used to minimize visible banding in selected final heat treated products.

Comparative assessment of resistance to enamel demineralization after orthodontic banding with three different cements- An in vitro study.

Objectives: This in vitro study was to compare the resistance to enameldemineralization after banding with three orthodontic cements, namely ZincPhosphate (Harvard Cement), ZincPolycarboxylate (Poly-F, Densply) and ResinModified Glass Ionomer Cement [RMGI] (Ortho Band Pak, GC Fuji).Materials and Methods: 80 premolarswere selected which were cleaned, dried and divided into four groups of 20each. Group A was a Control group. Group B, C and D were banded with thestainless steel bands using the respective cements. The teeth were then placedin deionized water for one month. They were debanded, cleaned and placed inartificial demineralizing solution for four weeks. Later they were cleaned andplaced in methylene blue for 24 hours to check the amount of demineralization. Theteeth were cut buccolingually and observed under the Motic Image Digital microscope.For analysis, the depth of dye penetration was measured in µm, which wasconsidered as equal to the depth of demineralization. Results: RMGI cement group showedsignificantly lesser amount of demineralization (6.679 ±3.016µm) compared to the Zinc Polycarboxylate cementgroup (18.0838± 5.833µm). The Zinc Phosphate cement group(55.360±8.667µm) andthe Control group(76.722± 18.832µm) demonstrated the greatest depth of enameldemineralization. Overall comparison showed a statistically significant difference(F=187.97, p<0.001).Conclusion: RMGI can be safely usedfor banding as it shows greater amount of resistance for enamel demineralization.