Number Of Rolling Passes Research Articles

Compaction quality assessment of cement stabilized gravel using intelligent compaction technology—A case study

As a new compaction quality management system of road construction, the intelligent compaction (IC) technology has shown a great potential for quality control and acceptance (QC/QA) in the compaction of cement stabilized gravel (CSG) subbase. However, before it achieves a high level of technology readiness, there are some challenges to be solved. One of the critical problems is that there is no reliable correlation between IC measurement values (ICMVs) and field test measurements, which is thus focused on. The influence of moisture content on the relationships between ICMVs and density were studied. Two types of ICMVs, roller-integrated stiffness (Kb) and compaction meter value (CMV), were collected and their correlations with material compactness were established respectively. In addition, it discusses the changing pattern of compaction degree and its uniformity with roller passes. The results show that, moisture content has a significant effect on the correlation between ICMVs and compaction degree of CSG. Compared with CMV, Kb has a higher regression coefficient with the in-situ measurements. Also, it is proven that the compaction degree and uniformity of CSG do not necessarily increase with the development in the number of rolling passes. Finally, this study makes a comprehensive evaluation of the compaction quality of the test section based on the relationships between ICMVs and in-situ test results.

Automatic roller path tracking and mapping for pavement compaction using infrared thermography

AbstractCompaction is an important task in asphalt pavement construction. It ensures high quality of the pavement to provide required long‐term performance. Intelligent compaction (IC) integrated with global positioning system (GPS) is an innovative technology to help control the compaction quality of asphalt pavement by continuously providing the operator with the roller's current position and the number of rolling passes. However, the high equipment cost and signal disturbance are two identified issues when adopting the GPS for position estimation. This paper proposed a thermal‐based method for real‐time roller path tracking and mapping in pavement compaction operations. In this method, first, the incremental roller motion between each two consecutive frames was jointly estimated via calculation of the roller's heading direction by exploiting the pavement boundary information and the roller's translation using the optical flow technique. Then, the accuracy of the estimated incremental motion was optimized by incorporation of the roller's lateral position estimated by a position optimization model proposed by the authors. Finally, the roller's global location was estimated by chaining frame‐by‐frame roller motions recursively. Both laboratory and field validations were conducted to examine the performance of the proposed method, leading to the maximum mean absolute errors along the lateral direction to be 5.2 mm and 3.3 cm, respectively, and the maximum cumulative error rates along the longitudinal direction to be 0.85% and 0.73%, respectively. The validation results signified the method's potential as a low‐cost and applicable alternative to the GPS in the current IC technology for roller's position tracking and mapping.

Determination of processing conditions of 1420 alloy of Al-Mg-Li system by applied temperature analysis

The design of airplanes and spacecraft of the new era requires the creation of materials that will be distinguished by lightness, increased strength and load capacity. When determining the processing parameters, the method of applied temperature analysis turned out to be useful and effective, the optimization of the composition and structure was greatly simplified, as well as the very transformation of the obtained experimental data into a ready-made digital form. Thanks to the method of applied temperature analysis, by linking to the periodicity of discrete states, the accuracy of determining the processing conditions of alloy 1420 of the Al-Mg-Li system is increased. The number of rolling passes can be reduced if, in addition to the data of forces, rolling speed, changes in sheet thickness, control of the dynamics of cracking is included. To perform the decomposition of the continuous deformation process of the blanks by scanning through the crack formation elements relative to the temperature axis in agreement with the determination of the sample size change data.

Effect of Nb on the Austenite Microstructural Homogeneity of Hot Rolled Rebars

While the role of Nb in flat rolling of low carbon steels has been investigated in many works, the information about the use of Nb in rebar rolling of higher carbon grades is more limited. Rebar rolling presents differences relative to flat rolling that can affect the role of Nb, such as the application of higher number of rolling passes, higher strain rates, lower interpass times, and, consequently, enhanced adiabatic heating. Increasing the number of passes can contribute to austenite grain refinement. However, the high finishing temperatures in rebar rolling can lead also to significant austenite grain growth and microstructural heterogeneity development before phase transformation. This phenomenon will directly influence the final grain size and can also lead to the appearance of second hard phases in the final product. One of the options to avoid austenite grain growth is to add microalloying elements that retard grain growth kinetics, either in solid solution or as precipitates. This can open new roles for the application of Nb in rebar rolling. To analyze this, in this work laboratory torsion tests were performed with two 0.2%C steels microalloyed with two different Nb contents (0.029% and 0.015%). Soaking temperatures from 1100°C to 1250°C were applied to obtain different amounts of Nb in solid solution before grain growth study. The study shows that not only finish rolling temperature and cooling time, but also reheating temperature and the amount of Nb remaining in the form of undissolved precipitates are important factors controlling austenite grain growth.

Treatments to improve the aeolian sand foundation in solar park construction

The aeolian sand in the Mohammad bin Rashid Al Maktoum (MBR) Solar Park Phase IV Project site in Dubai, United Arab Emirates, is cohesionless, uniformly graded, non-plastic fine sand, with high permeability, low shear strength and low bearing capacity, which are properties that cause many geotechnical and structural challenges. With aeolian sand used as backfill soil, sandstone and sabkha (gatch, gypsum) excavated during field levelling were used as sand fixation material to improve the aeolian sand foundation. In a field compaction test, the compaction method, moisture content, paving thickness, number of rolling passes, backfill layer deformation, compaction coefficient and California bearing ratio were analysed to summarise the technological aspects of the compaction process. Rolling greatly improved the aeolian sand foundation, achieving the required capacity for various projects. The surface layer was stabilised by sandstone–gatch, which had the strongest resistance to wind erosion. By contrast, the resistance of the sandstone–gypsum layer to wind erosion was moderate, and that of the sandstone layer was weak. The experiments used to improve the aeolian foundation in this study can be applied to similar desert areas on the Arabian Peninsula and in North Africa.

Analysis of crack formation of an Al-Mg-Li (1420) system alloy under the influence of thermal energies

Cracks of all types are extremely dangerous for structures; this fact is critically unacceptable in the rocket and space industry. Aluminum-lithium alloys have a perfect set of mechanical, operational and corrosion characteristics that allow them to compete with traditional alloys and even polymer composite materials. The main focus of scientific research was the analysis of crack formation when combining two successive methods of heating samples of the promising rocket and space industry alloy 1420: discrete isothermal scanning and continuous program heating. The relationship between such factors as the average elongation of cracks in the sample, the number of cracks in the sample, changes in the area of the sample relative to the degree of compression of the material, the heating temperature of the sample, the exposure time in the furnace, the number of rolling passes, and rolling speed were revealed in the paper.

Microstructure and mechanical properties of caliber rolled Mg–Y–Zn alloys

The microstructural evolution and mechanical properties were investigated using a caliber rolled Mg–5Y-2.5Zn (in at.%) alloy. Deformation kink bands could be induced by the caliber rolling process, which is the same as that of conventional wrought processed (extruded or rolled) Mg–Y–Zn alloys. The number of rolling passes was an influential factor for the microstructure, i.e., the bending angle of the long periodic stacking ordered (LPSO) phase associated with deformation kink bands. The mechanical properties of strength and hardness also depended on the number of rolling passes. These properties were improved with increased number of rolling passes (up to 6 passes). The yield strength and hardness before the rolling process were 260 MPa and ~90 Hv. On the other hands, after caliber rolling, these properties showed over 500 MPa and 129 Hv, respectively, for the alloy with 6 rolling passes. Microstructural observations revealed that such good properties resulted from the existence of deformation kink bands and dense dislocations induced by caliber rolling. Controlling the morphology of the LPSO phase associated with deformation kink bands was found to be an effective strategy; the bending angle of this phase of more than 20° is outstanding for further improving the mechanical properties.

Theoretical and experimental study on the producible rolling thickness in ultra-thin strip rolling

Abstract The cold rolling process of a thin strip is difficult to continue when the strip has been thinned to a certain thickness. A limit thickness, which is referred to as the limiting producible rolling thickness below which plastic deformation does not occur, exists even if the rolling force and the number of rolling passes are increased. The Stone formula is the most common approach for predicting this limit, but its results are inaccurate in experiments or in ultra-thin strip-rolling production. In this study, the variation laws of the contact profile and rolling pressure of ultra-thin strips with different thickness specifications at different reductions were obtained by finite element simulations, indicating that the Stone minimum thickness can be regarded as the critical thickness that exists when a neutral zone is present under a minimal reduction. A theoretical calculation model of producible rolling thickness for an ultra-thin strip based on Fleck theory was established and verified by experiments. When this model is used, the single-pass reduction can be obtained in accordance with the given unit width rolling force, the technical parameters of the rolling mill, the yield strength of the material, and the initial thickness of the strip. The formula for the conditional limiting producible thickness considering the restriction of rolling force was corrected. The relationship between single-pass reduction and the ratio of the initial thickness of the strip to the theoretical limiting producible thickness under the condition of the maximum allowable rolling force of the rolling mill was discussed. This study provides theoretical guidance for practical production by defining the product specification ranges and rolling regulations for existing rolling mills and determining the roller diameters and force and energy parameters for the design of rolling mills.

Thermal Conductivity of an AZ31 Sheet after Accumulative Roll Bonding

Accumulative roll bonding (ARB) is one of the methods of severe plastic deformation which is relevant for industrial production of sheets. While mechanical properties of several magnesium alloys subjected to the ARB process have been studied, the physical properties have been reported only for some magnesium alloys. These properties are influenced by the texture developed during the ARB process and the temperature load. In the presented contribution, we studied thermal conductivity of an AZ31 magnesium alloy after one and two passes through the rolling mill. Thermal diffusivity was measured with the laser-flash method in the temperature range between 20 and 350 °C. Thermal conductivity depends on the number of rolling passes. The microstructure and texture of sheets are significant factors influencing thermal properties.

Studying Temperature Variations that Occurred during Cold and Hot Rolling of AA5454-O Alloy

In this study, temperature distribution that occurred during cold and hot rolling of AA5454-O alloy has been investigated. Temperature variation taking place in the aluminium alloy that has undergone plastic deformation between the rollers during hot and cold rolling process is of major importance in terms of determining the positive and negative characteristics or features which such temperature variation adds to the formation of the internal structure of the material concerned. Temperature distribution has been measured by use of the installed laboratory equipment and respective data recorded has been presented in the form of graphic charts. Temperature distribution has varied depending on the application of hot or cold rolling process and it has been noted that variations in terms of temperature reduction took place depending on the number of roll passes. While average temperature variation has occurred as a 16°C increase in the case of cold rolling, it has been observed that such variation appeared as a 100°C decrease on the average in the case of hot rolling.

Mechanical Properties and Microstructure of Mg-SiCp Composite Sheets Fabricated by Sintering and Warm Rolling

In this study, magnesium matrix composite sheets were fabricated by applying powder metallurgy and warm rolling methods. After preparing required mixtures of magnesium powder and SiC particles in different conditions, they were cold-pressed and sintered. Then, the sintered specimens were warm rolled through different numbers of passes. The effects of ball-milling process and the number of rolling passes were investigated on the tensile strength, hardness, microstructure, and fracture surface of magnesium matrix composites. The results were compared to those monolithic magnesium specimens (without reinforcement particle) produced in a way similar to that of the composites. The results show that among different factors (i.e., ball-milling process, the presence of SiC particles, and the number of rolling passes), the number of rolling passes is the most effective parameter on increasing the ultimate tensile strength (UTS),Vickers microhardness, and grain refinement. In this regard, UTS of the samples was increased at least 163% between second and sixth rolling passes. Moreover, for the sintered and six-pass rolled composite samples, microhardness and grain refinement were improved, respectively, about 30 and 70%.

Deformation mechanism and microstructure evolution during on-line heating rolling of AZ31B Mg thin sheets

An AZ31B sheets were processed by on-line heating rolling (ON-LHR) in five passes. Roll and sheets temperatures were 473K and 533K, respectively. The grain size was reduced in the first three roll passes, to a minimum of 4.1μm, due to dynamic recrystallization, and coarsened in the last two passes due to a combination of dynamic recrystallization and grain growth. The yield strength, ultimate tensile strength and elongation to fracture reached 232MPa, 347MPa and 21% in the rolling direction. The maximum yield strength occurred after the fourth pass. The maximum is attributed to the small grain size and the formation of networks of sub-grains and deformed grains. The rolled sheets had a strong basal texture, which was largely unchanged with the number of roll passes. The existence of the strong texture after rolling indicated discontinuous dynamic recrystallization.

롤 포밍 공정에서의 롤 패스의 수에 따른 스프링 백 영향 연구

This study was analyed V-bending in order to analyze the spring-back phenomenon in the roll forming process. The material of forming sheet used in the roll forming process is high tension steel and the product name of sheet material is POSTEN 60. The most important variable is the number of roll passes (3-Pass, 4-Pass, 5-Pass, 6-Pass and 10-Pass) and other roll forming process variables were fixed. To determine the characteristics of the tension and compression, the forming sheet was analyzed by dividing the layer (Upper and Bottom) in the thickness direction from the center line. The results of FEM simulation analysis was derived to von-mises stress equivalent strain, and the spring-back value was calculated according to the final forming shape. The more number of the roll pass, von-mises stress and equivalent strain value of forming sheet were lowed. Also, spring-back values tended to decrease. The results of this study can be utilized for prediction and trend of spring-back value in the roll forming process applied to high tension steel sheet. So, development time and cost of the roll forming process is expected to be reduced.

Accumulative Roll Bonding of Pure Copper and IF Steel

Severe plastic deformation is a new method to produce ultrafine grain materials with enhanced mechanical properties. The main objective of this work is to investigate whether accumulative roll bonding (ARB) is an effective grain refinement technique for two engineering materials of pure copper and interstitial free (IF) steel strips. Additionally, the influence of severely plastic deformation imposed by ARB on the mechanical properties of these materials with different crystallographic structure is taken into account. For this purpose, a number of ARB processes were performed at elevated temperature on the materials with 50% of plastic deformation in each rolling pass. Hardness of the samples was measured using microhardness tests. It was found that both the ultimate grain size achieved, and the degree of bonding depend on the number of rolling passes and the total plastic deformation. The rolling process was stopped in the 4th cycle for copper and the 10th cycle for IF steel, until cracking of the edges became pronounced. The effects of process temperature and wire-brushing as significant parameters in ARB process on the mechanical behaviour of the samples were evaluated.

Effects of hot rolling and inter-stage annealing on the microstructure and texture evolution in a partially homogenized AZ91 magnesium alloy

The evolution of microstructure during hot rolling and inter-stage annealing of a partially homogenized AZ91 magnesium alloy was investigated by microscopic examination and micro-texture analyzing. The effects of key processing parameters including rolling temperature, rolling speed, number of rolling passes and inter-stage annealing treatment on the deformation mechanism and recrystallization behavior of the experimental alloy were studied. At lower rolling temperature, the plastic strain applied during rolling was accommodated by the formation of twin and shear bands whereas at higher temperatures non-basal slip systems were activated resulting in the suppression of twinning and, hence, slip became the dominant deformation mechanism in such rolling conditions. The process facilitated an effective grain refinement by both dynamic and static recrystallization phenomena with an increase in the number of rolling passes and conducting inter-pass annealing stages leading to a reduction of average grain size to below 10μm. Moreover, optical microscopic examinations for all the rolling conditions demonstrated that twin DRX was the major dynamic recrystallization mechanism at the beginning of the rolling process due to the large initial grain size. However, new grains were found to nucleate preferably at grain boundaries as the average grain size decreased during the hot rolling process. Micro-texture analysis for all the processing conditions showed a relatively strong basal texture produced after the first pass of rolling, which was then weakened during the subsequent annealing and rolling stages.

FEM Analysis of the Deformation Behavior at Thickness Direction in Laboratory Plate Hot Rolling

As significant theory evidence in thick plate or heavy gauge plate hot rolling, the deformation behavior at the thickness direction was investigated. In the present work, multi and single pass rolling processes were studied by 2D explicit dynamic finite element method (FEM) simulation and verified by laboratory hot rolling experiment. The value of stress and strain could be obtained in any passes and time in the hot rolling process accurately. The verified FEM model could be used as an important reference factor for other hot rolling processes. Strain and stress distribution data was obtained from four portions at the thickness direction. A cooper rod was knocked into the hot rolling specimen, as a reference substance to observe the deformation after the hot rolling experiment. In the multi-pass simulation with nearly 10% per-pass reduction, the core metal yield when the total reduction was 40%. The same performance could be achieved when the first pass reduction larger than 20%. However, extremely first pass reduction would cause an instability deformation result in a confusion of microstructure. Finally, the relation between the reduction and the number of rolling passes was discussed.

Toughness behavior in roll-bonded laminates based on AA6061/SiCp composites

Lamination has been shown to enhance damage tolerance of discontinuously reinforced aluminum (DRA) composites. Doing this technique, DRA layers could be laminated with ductile interlayers. In this research, two types of laminates consisting similar DRA layers and a ductile AA1050 interlayer were fabricated by means of hot roll-bonding. AA6061–5vol% SiCp and AA6061–15vol% SiCp composites were considered as exterior layers. Different rolling strains, was applied to control the interfacial strength which was examined by shear test. Toughness behavior of laminates was evaluated by three-point bending test in crack-divider orientation. Based on obtained results, the plastic deformation of ductile interlayer and delamination are challenging toughening mechanisms which were influenced by the degree of interfacial bonding and ceramic particle content. An increment in reinforcement content alters the toughness behavior of laminates in the way that the governing mechanism in laminates containing 5vol% SiCp is interfacial adhesion since in laminates having 15vol% SiCp the dominant mechanism is AA1050 deformability. Meanwhile, optical and scanning electron microscopy observations proved the importance of toughening mechanisms in each type of materials. Also, shear test results revealed that the interfacial strength of laminates increases by the number of rolling passes and deteriorated by higher reinforcement contents.

Processing of ultrafine-grained aluminum by cross accumulative roll-bonding

In this paper, the structural and mechanical characteristics of aluminum strips subjected to two severe plastic deformation processes, namely accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), are compared. Transmission electron microscopy studies on the strips showed that ultrafine grains are formed by both of the processing routes to eight passes. However, the structure of the CARB-processed specimen was less elongated than that of the ARB-processed specimens; that is, the aspect ratio of grains in the CARB case was less than that in the ARB specimens. Tensile tests indicated that the tensile strength is increased with the number of rolling passes, and the strength of the CARB specimens is higher than that of the ARB specimens.

Toughness Enhancement in Roll-Bonded Al6061-15 vol.% SiC Laminates via Controlled Interfacial Delamination

Researchers have examined different approaches to improve damage tolerance of discontinuously reinforced aluminum (DRA). In this study, three-layer DRA laminates containing two exterior layers of Al6061-15 vol.% SiCp and an interlayer of Al1050 were fabricated by hot roll bonding. Interfacial adhesion between the layers was controlled by means of rolling stain. The results of shear test revealed that, the bonding strength of laminates was influenced by number of rolling passes. Considering this effect, the role of interfacial bonding on the toughness of laminates was studied under three-point bending in the crack divider orientation. The quasi-static toughness of the laminates was greater than that of the monolithic DRA. Plastic deformation of the ductile interlayer and interfacial delamination were found as the major sources of energy absorption in this fracture process. It was shown that interfacial adhesion in these laminate does not alter the initiation energy in quasi-static test. Propagation energy under same loading condition, however, illustrated significant sensitivity to the interfacial bonding. The results of the current study reveal that improving the interfacial adhesion by means of rolling strain eliminates the ease of plastic deformation of the ductile interlayer and thus reduces the contribution of this mechanism in quasi-static toughness of the laminate.

Experimental study of the disturbed layer generation during hot rolling contact of aluminum with steel

Effects of rolling passes and forward speed on the generation of disturbed layer on aluminum alloy sheet surfaces were investigated using a hot rolling simulator at forward speeds of −1% and 12% in presence of spraying emulsion. The results showed that at higher forward speed and number of rolling passes, the localized shear deformations become more pronounced on the surface. However, when the two rolling passes were in opposite directions, the localized shear deformations did not stick out, but were embedded into the aluminum surface. The defects generated were representative of the initial stages of the disturbed layer formation.