Feasibility of Synchronously Straightening Working Line of Adjacent Open-cast Mines

Taking Heidaigou Open-cast Mine and Haerwusu Open-cast Mine in Zhungeer mining area as the research objects,this paper deeply analyzes the current mining status of the two mines.Based on the existing working line length,mining technology,transportation system,equipment configuration,transportation access and many other factors,it systematically discusses the feasibility of straightening the working line of adjacent open-cast mines.Through in-depth theoretical analysis,it establishes the mathematical model of impact indicators and cost calculation,and it is concluded that the work line straightening can be technically achieved.However,from the perspective of economic benefits,straightening the working line does not show obvious advantages.

RESEARCH ON STRAIGHTENING TECHNOLOGY CAM SYSTEM

Automatic straightening process is a nonlinear process, and affected by manyfactors. The straightening technology CAM system has been designed and built up to straightenshafts, which mainly consists of the straightening technology's database and the model ofstroke-controlled precise straightening calculation model. The operational test of the CAM systemhas been passed.

Innovation in the Computing System of Straightening Force

Currently in China, the computing system of the straightening force of the six-rollers straightening machine generally follows the traditional computing system. The force status of the traditional computing system for the straightening force deviates far away from the actual force status of the roller system in the six-rollers straightening machine. In the traditional system, the computing model of the straightening force of the six-roller straightening machine was based on the roller shape of hyperbola, which led to the length of the contacting line between the tube and the straightening roller to be excessively short, i.e., only 0.1~）.2 of the length of the roller. Thus the constructed computing system has relatively large difference from the actual measured result. To solve the above problems, flattening straightening and bend straightening are analyzed on the basis of materials mechanics and bend beam theory, the roll er shape using the envelope method of A.I4.~e：mKoB is generated, and a new computing system for straightening force in six-rollers straightening machine is built. The roller shape of the straightening roller, on which the new computing system for the straightening force is based, is designed according to the envelope method under the condition of ideally full contacting between the tube and the roller body of the straightening roller, therefore the new computing model accords with the practical status of straightening force. According to the comparison of the new computing system with finite element method and the actual measured result of straightening force, it has been proved that the computation accuracy of the new computing system for straightening force satisfies the practical requirements of engineering. New six-rollers straightening machines are designed and manufactured according to the new calculation system, and the new machines not only have higher precision and quality, but also have adopted the force sensor and computer and combined with the new computing system for straightening force to realize the fully automatic adjustment of the straightening machine. The new six rollers straightening machine have obtained notable economical and social benefits.

Longitudinal crack on slab surface at straightening stage during continuous casting using finite element method

Deformation behavior of slab at the straightening stage during continuous casting was simulated by the explicit dynamic finite element method,and the stress distribution along the width direction of the slab and its change regularity at slab center during continuous casting were obtained.The influence of distribution and change of stress on the propagation of longitudinal cracks on slab surface was discussed.The results show that the tensional stress appears on slab surface at the inner arc side and the compressive stress appears on slab surface at the outer arc side at stages 6-8 in straightening zone during continuous casting.Longitudinal cracks generally appear on slab top surface and do not appear on slab bottom surface,which are also observed in industry.

Multi-point flexible straightening process by reciprocating bending for metal profiles

A multi-point flexible straightening process characterized by reciprocating bending is proposed.Specifically,the process is analyzed in terms of deformation mechanism and verified by numerical simulations and physical experiments of the straightening of a series of metal profiles with different materials and initial shapes.Further,the relationship between the bending radius and the times of reciprocating bending required to unify the curvature is discussed,and the distribution of residual stress after straightening is analyzed.The results show that the reciprocating bending process can eliminate the difference of the initial curvature,make the curvature of each section tend to be uniform;the times of reciprocating bending to reach the uniform curvature decreases with the decrease of bending radius.The straightness of the straightened profile obtained from the experiment and simulation is less than 0.2%,demonstrating a good feasibility of this method.

The mathematic model of tension straightening process of magnesium alloy and experimental validation

The stress-strain curve of bending bar and the stress relax curve of AZ31 was obtained by a tension test using Gleeble-1500.The tension straightening process mainly consisted of the elastic loading-I and unloading stage,the elastic loading-II and unloading stage,and the elastic-plastic loading stage,which were based on the stretch force change during straightening.The circular bar straightening under one-dimensional bending was investigated and assumed to be linear strain-hardening elastic-plastic material.According to the elastic-plastic mechanics theory,the mathematical displacement-force model of a tension straightening process established,on which was based,the predicted displacement of tension straightening for various original deflection was calculated.The tension straightening experiment for AZ31 magnesium was conducted under the guidance of the predicted displacement.The experiment results present good straightness when there is a stress relaxation phenomenon or the temperature of tension straightening is 25℃.

Evaluation of straightening capacity of plate roll straightener

Straightening machine is widely used for improving the quality of the defective mild steel plates.In general,the capacity of straightening machine is affected by material properties,the initial shape of the incoming plate and the plastic ratio.The mechanics model describing the capacity of the machine was developed.The deviation of the straightening capacity curves was studied.Then,the presented model was evaluated by comparative study to filed production data.Finally,the influences of overstretch,straightening speed,strengthening coefficient,elastic modulus,width of the plate on the straightening capacity were studied.It is convenient to determine whether the plate can be straightened or not by a series of straightening capacity curves.The straightening speed,width of the plate and elastic modulus of the material are more sensitive to the straightening capacity than the strengthening coefficient.

The Role of Corrugation Die Parameters on the Mechanical Properties of Aluminum Alloy (AA 5083) Processed by Repetitive Corrugation and Straightening

The microstructure and mechanical properties of aluminium alloy (AA 5083) processed through Repetitive Corrugation and Straightening (RCS) was studied. The RCS process consists of corrugating a flat specimen with a pair of systematically grooved dies and straightening was done with two parallel flat dies. The aluminium samples were subjected to RCS process using two different die: Die I-semi grooved die with breath = height = 5 mm and θ = 30。 and Die II-semicircular profile with radius = 10 mm. The specimens were subjected to maximum 8 passes for die I but the other one went upto 14 pass. The grain refinement was studied from the microstructure examination using TEM. The mechanical properties such as tensile strength, hardness and the grain size were compared. The tensile strength and hardness were found increasing with respect to the number of passes. The tensile strength increased 25% in the sixth pass when compared to the parent material. But the strength and hardness values were reduced at 8th pass due to the surface cracks. The TEM studies showed that the Die-I is superior to Die-II in terms of grain refinement.

A Solution of Drawing Straightening Roller Curve by Conjugate Revolving Quadric Theory

Based on the theory of conjugate revolving quadric theory,the analytic method of calculating the straightening roller curve in the procedure of straightening the bar has been given. Meanwhile,the equations,which describe roller curve and the longitudinal section,are given and simulated in computer. A brief method of designing and drawing the straightening roller curve is introduced.

Effects of Channelization on Fish Biomass in River Ecosystems

Channel straightening in a naturally meandering river is a common historical trigger of channel incision which typically results in stream bank destabilization. Several of the larger river systems in the upland portion of the Yazoo River Basin have subjected channelization resulting in profound changes in the physical and geomorphological characteristics of these systems. Fish were sampled using electroshocking gear and hoop nets to evaluate the impact of stream bank destabilization and loss of habitat heterogeneity resulting from channelization on fish communities. While distinct differences in the fish communities were evident, only the Skuna appeared to have characteristics of a damaged system. More than 95% of the biomass was comprised of species reaching an adult length of less than 300 mm. The lotic omnivorous fishes that dominated the biomass from Skuna are often associated with smaller streams rather than rivers. Furthermore, 72% of the catch consisted of fish preferring littoral zone habitats. The shallow depth and lack of woody debris in Skuna provided a selective advantage for smaller species of fish that could use shoreline habitats as protection from the current. Based on results from the Skuna River, channel straightening that leads to channel incision, bank failure and over widening provide habitats too shallow to support a community of fishes typical of northern Mississippi riverine system. This information may be useful in making comparison of damaged riverine ecosystems and assist managers in determining impairment and success in the TMDL （Total Maximum Daily Load） process.

Analytical-Numerical Modeling Approach for Calculation of the Structural Distortions after Welding and Thermal Straightening

The analytic-numerical hybrid model for calculating welding distortions in large welded structures is presented. Objective of the analytical model is the calculation of the plastic strains and their distribution after welding and thermal straightening process. The consideration of the essential physical relations is put into discussion. Afterwards the obtained plastic strains by the analytical calculation are loaded on an elastic FE-model of the structure and the distortions of the whole structure are predicted. The consideration of welding and thermal straightening scenarios and the assembling stages is done by taking into account the intermediate variation of the strain state at every processing step. The model is intended to be used for solving industrial tasks, i.e. intending acceptable precision and calculation time as well as low simulation costs. The application of the model is demonstrated on structures with many welds and straightening spots.

Cone-beam computed tomography analysis of curved root canals after mechanical preparation with three nickel-titanium rotary instruments

Cone beam computed tomography is a 3-dimensional high resolution imaging method. The purpose of this study was to compare the effects of 3 different NiTi rotary instruments used to prepare curved root canals on the final shape of the curved canals and total amount of root canal transportation by using cone-beam computed tomography. A total of 81 mesial root canals from 42 extracted human mandibular molars, with a curvature ranging from 15 to 45 degrees, were selected. Canals were randomly divided into 3 groups of 27 each. After preparation with Protaper, Revo-S and Hero Shaper, the amount of transportation and centering ability that occurred were assessed by using cone beam computed tomography. Utilizing preand post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. Canals were metrically assessed for changes （surface area, changes in curvature and transportation） during canal preparation by using software SimPlant; instrument failures were also recorded. Mean total widths and outer and inner width measurements were determined on each central canal path and differences were statistically analyzed. The results showed that all instruments maintained the original canal curvature well with no significant differences between the different files （P=0.226）. During preparation there was failure of only one file （the protaper group）. In conclusion, under the conditions of this study, all instruments maintained the original canal curvature well and were safe to use. Areas of uninstrumented root canal wall were left in all regions using the various systems.

Effect of flame heating pass on microstructure and properties of A6N01 aluminum alloy welded joint

Flame heating combined with water cooling was used to straighten A6N01 aluminum alloy welded joint and effect of flame heating pass on its microstructure and mechanical properties was studied. Results showed that the flame induced the precipitation and growth of the Mg_2Si phase on the Al substrate for the thermal aging A6N01 aluminum alloy welded joints,thus it led the decrease of micro-hardness and tensile strength of the A6N01 aluminum alloy welded joint with the increase of the heating pass. However,the fatigue property of the flame heated joint was improved because the Mg_2Si precipitation hindered the initiation and propagation of the fatigue crack.

High-temperature mechanical properties of near-eutectoid steel

The high-temperature mechanical properties of near-eutectoid steel were studied with a Cleeble-1500 simu- lation machine. Zero strength temperature （ZST）, zero ductility temperature （ZDT）, hot ductility curves, and strength curves were measured. Two brittle zones and one plastic zone were found in the temperature range from the melting point to 600℃. Embrittlement in zone I is caused by the existence of liquid film along dendritic interfaces. Ductility loss in zone Ⅲ mainly results from precipitates and inclusions as well as S segregation along grain boundaries. Pearlite transformation also accounts for ductility deterioration in the temperature range of 700-600℃. Moreover, the straightening temperature of the test steel should be higher than 925℃ for avoiding the initiation and propagation of surface cracks in billets.

COLD-WORKING AND HEAT-CRACKING IN Ni-Cu-BASE MONEL ALLOY K-500

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Processing practice of Baosteel drill pipes

Drill pipe products are the most critical service requirement,the highest performance requirement and the highest quality reliability OCTG products.Through the continuous research on steelmaking,upset, heart treatment,straightening and friction welding,Baosteel improves the key technical parameters which affect the quality of drill pipe,such as material purity,Miu of internal upset transition area,toughness and straightness.Baosteel drill pipe products have met the demanding requirement of drilling operations.By BRP dephosphorization and LF desulfurization,the P,S content of Baosteel drill pipe is very low.The S content of S-135 drill pipe can be controlled in less than 10ppm.Baosteel designs a new closed-loop control system of upset end induction heating system.The system use temperature measurement inside the oven and closed-loop control.The temperature accuracy of the system can be guaranteed within the±15℃to get a stable upset quality.The upsetting process of the drill pipe is optimized by using patented technology and made the Miu from 100 mm to 140 mm.This make a substantial increase in fatigue life of the drill pipe.To improve the impact toughness of the drill pipe body,the drill pipe body material is changed from Cr-Ni-Mo system to Cr-Mo-V system and the heat treatment is changed from oil quenching to water quenching.To improve the impact toughness of the tool joint,the tool joint furnace is upgraded to improve heating capacity.To improve the impact toughness of the weld zone,a new fuzzy control system of weld zone heat treatment is developed.The temperature accuracy of the system can be guaranteed within the±5℃to get a stable heat treatment quality.A new drill pipe straightness automatic detection devices and self-learning method of straightening are developed to achieve automated straightening.A welding process with high speed,single-stage pressure and high forging force is applied to inertia friction welding.A welding process with low speed,three-stage pressure and low forging force is applied to continous friction welding.

Improvement on straightness of metal bar based on straightening stroke-deflection model

The straightening technics is one of important means to improve the straightness of metal bar. A novel way of predicting the straightening stroke is proposed based on mathematical methods and bending experimental and numerical simulation. The experimental and numerical simulation is conducted by following the mathematical load-stroke model of press straightening process under the elastic-plastic theory. For the linear guide rails, as an example, the stroke-deflection model focusing on the straightening stroke prediction can be achieved by contrasting and integrating the bending experimental results and finite element methods (FEM) simulation data. And then the formula for predicting the straightening stroke is presented based on the precise straightening stroke-deflection model. The stroke prediction formula with high precision can be applied to the straightening stroke prediction in the high straightness metal bar manufacturing process and automatic straightening machine conveniently.

Principle of Multi-roller Straightening Process and Quantitative Resolutions of Straightening Strategies

The multi-roller straightening process of section steel is analyzed by the springback theory of small curva- ture plane bending. The theoretical analysis results prove the curvature unification in straightening process and clear- ly reveal the principle of the multi-roller straightening process. The principle can be described as~ the initial curva- tures are reduced by several times anti-bendingl meanwhile the initial curvature differences are diminished and the residual curvatures are unified~ finally, the member after curvature unification is straightened by the last anti-ben- ding. With the plastic region ratios becoming larger, the initial curvatures are more easily unified in straightening process. Based on the plastic region ratios and the required number of roller systems for unifying the initial curva- tures, the large deformation straightening strategy and the small deformation straightening strategy are redefined. The new definition provides an important theoretical basis for setting reliable reduction rules. Through the theoretical analysis results, a new straightener design philosophy is proposed to improve the straightening quality and further increase the adjustment precision as well as the flexibility of the last roller system. The adjustable end roller emerges as the times required, achieving a good effect in practical application.

Bauschinger-Like Effect of AZ31 Magnesium Alloy Wide Sheet During the Straightening Process

The Bauschinger-like effect, which showed up in the straightening process of the AZ31 magnesium alloy wide sheet, was investigated through the multi-pass discrete three-point bending–unloading–bending(BUB) experiments. The stress variable, anisotropy, and asymmetry of tension and compression on the straightening process were corresponding to the Bauschingerlike effect. The Bauschinger-like effect in the initial, intermediate, and end of the straightening process was dominated by the twinning, detwinning, and dislocation induced by pyramidal < c + a > slip, respectively. Also, they were responsible for the transformation of the Bauschinger stress parameter(BSP) and Bauschinger energy parameter(BEP). Later, the anisotropic nonlinear kinematic hardening model(ANK model) to describe the Bauschinger-like effect was optimized and simplified.

Continuous bending and straightening technology of Q345c slab based on high-temperature creep deformation

A new continuous bending and straightening casting curve with the aim of full using of high-temperature creep deformation was proposed. The curvature of bending and straightening segment varies as sine law with arc length. The basic arc segment is shortened significantly so that the length of bending and straightening area can be extended and the time of creep behavior can be increased. The distance from so lidifying front in the slab was calculated at 1200 ℃ by finite element method. The maximum strain rate of new casting curve at different locations inside the slab is 6.39 × 10 ^-5 s ^-1 during the bending segment and it tends to be 3.70 × 10 ^-5 s ^-1 in the straightening segment. The minimum creep strain rate is 7.45× 10 ^-5 s ^-1 when the stress is 14 MPa at 1 200 ℃. The strain rate of new casting machine can be less than the mini mum creep strain rate. Thus, there is only creep deformation and no plastic deformation in the bending and straightening process of steel continuous casting. Deformation of slabs depending on creep behavior only comes true. It is helpful for the design of the new casting machine and improvement of old casting machine depending on high temperature creep property.